Recent lbnl_ps_bcmt items

Characterization of the First Prototype of the L1K65n Differential-Output Charge-Sensitive Preamplifier ASIC for High-Performance, Low-Background HPGe Detector Readout

Fri, 5 Jun 2026 00:00:00 +0000

Next-generation neutrinoless double-beta ( $\mathbf {0}\boldsymbol { u }\boldsymbol {\beta }\boldsymbol {\beta }$ ) decay searches require a large detector/isotope mass and very low radioactive backgrounds. The upcoming LEGEND-1000 experiment (Large Enriched Germanium Experiment for Neutrinoless double-beta Decay) constitute a ton-scale array of several hundred high-purity germanium (HPGe) detectors enriched in 76Ge, the isotope of interest. It aims to reach a sensitivity beyond $10\mathbf {^{28}}$ years on the $\mathbf {0}\boldsymbol { u }\boldsymbol {\beta }\boldsymbol {\beta }$ decay half-life of 76Ge, necessitating an order of magnitude reduction in background with respect to the state of the art. This will require the implementation of a dedicated application specific integrated circuit (ASIC) preamplifier that will significantly lower background contribution compared to the conventional low-mass front end (LMFE) employed in the Majorana Demonstrator and LEGEND-200 experiments...

Conceptual Structural Design and Analysis of a 20 T Hybrid Cos Dipole for Future Particle Colliders

Tue, 24 Mar 2026 00:00:00 +0000

To reach high collision energy for future high-energy particle colliders, like the Future Circular Collider (FCC) or the Muon Collider, it is required to achieve high field strength of the bending dipoles. Currently, the practical limit for Nb$_{\text{3}}$ Sn technology is around 16 T and, in order to further increase the magnetic field, the superconducting magnet community is considering High Temperature Superconductors (HTS), in particular Bi-2212 and REBCO conductors. However, their relevant higher cost has led the community to consider a hybrid approach where HTS materials are used in the high field region of the coils with so-called insert coils, and Low Temperature Superconductors are involved in the lower field part ($< $ 16 T) with so-called outsert coils. This paper describes the conceptual mechanical design of a 20 T hybrid cos$\theta$ dipole configuration. The high stress levels that the structure is facing due to the high magnetic field are discussed. Moreover,...

Elliptic Aperture CCT Coils for HTS Dipole Magnets

Thu, 19 Mar 2026 00:00:00 +0000

High-temperature REBa$_{2}$Cu$_{3}$O$_{7-x}$ (REBCO) superconductors are a route to increase the field of accelerator magnets beyond the 15-16T practical limit of Nb$_{3}$Sn. REBCO cabled in a CORC geometry is a promising fit for this application, enabling the design of low inductance magnets with conductor transposition. However, the use of CORC in coils with the tight conductor bending radii typical of accelerator magnets remains a key challenge, with on-going research both on the conductor development and coil design fronts seeking to address this issue. In this work we explore the tradeoffs between circular and elliptic aperture canted-cosine-theta (CCT) coils when the conductor minimum bending radius is a key consideration, concluding that aperture ellipticity is an important free parameter in the optimization of magnetically efficient CORC dipole magnets. In particular, we show that elliptic bore designs enable a regime of smaller aperture HTS coils, an important result...

Cooling Design and Thermal Analysis for Thermal Shields of a Cryocooler-Cooled Superconducting ECR Ion Source MARS-D Magnet

Wed, 11 Mar 2026 00:00:00 +0000

A demonstrative NbTi based Mixed Axial and Radial field System (MARS-D) is being developed for a next-Generation Electron Cyclotron Resonance Ion Source (ECRIS) at Lawrence Berkeley National Laboratory (LBL), which employs a novel closed-loop coil design scheme that more efficiently utilizes conductor fields and extend the application of NbTi for high frequency (up to 45 GHz) ECR operation. The NbTi MARS-D magnet consists of a single hexagonally shaped closed-loop coil and a set of auxiliary solenoids. A cryostat for cooling the MARS-D magnet is under design at LBL. The MARS-D magnet working around 4.2 K will be bath-cooled in liquid helium using multiple two-stage cryocoolers. An intermediate temperature thermal radiation shield is adopted to reduce the heat leakage imposed on 4.2 K coil cold mass from room temperature. The thermal shield is conduction-cooled by the first-stage cold heads of four two-stage cryocoolers and the cold head of a single-stage cryocooler shared with...

Analysis of Screening Current Effects in a Hybrid Nb$_{3}$Sn/REBCO Superconducting Accelerator Magnet Using a T-A Formulation

Wed, 11 Mar 2026 00:00:00 +0000

To explore the feasibility of using high-temperature superconducting (HTS) REBCO coated conductors in future accelerator magnets, two REBCO flat racetrack coils were fabricated using 4-mm wide EuBCO tapes at the High Energy Accelerator Research Organization (KEK). These coils were tested as an insert inside a Nb$_{3}$Sn common-coil dipole magnet, which provides a background field of up to $\sim$ 9.5T, at the Brookhaven National Laboratory (BNL). REBCO tapes offer exceptionally high critical current density under strong magnetic fields; however, they also exhibit significant magnetization due to screening currents, leading to magnetic field errors. This study presents a 2D finite element model of screening current-induced fields (SCIF) in REBCO coils using the T-A formulation, along with the results obtained. Simulations were then performed for two KEK test cases: one where the REBCO conductors were oriented with the HTS tapes parallel to the background field, and another where...

Thermal Performance of a Conduction-Cooled CCT Dipole ReBCO Magnet: Several Cycles of Cool-Down and Thermal Gradient Measurements

Wed, 11 Mar 2026 00:00:00 +0000

This paper presents experimental results from conduction-cooled thermal testing of a ReBCO canted cosine theta (CCT) magnet (C2), originally designed and fabricated at LBNL using CORC cables. While the performance of the coil under liquid helium and nitrogen environments has been previously established, this study explores its behavior under conduction cooling using a large test cryostat at The Ohio State University. The magnet, measuring 613 mm in length and weighing 75 kg, consists of four helical layers wound with ReBCO-based CORC wire and was thermally anchored to a copper cold ring supported by a G-10 strongback. Cooling was provided by two Sumitomo RDK-415D cryocoolers, offering a combined 3 W at 4.2 K and 150 W at 77 K. Multiple thermal cycles were performed, with cooldown durations of up to 45 hours. Final base temperatures of approximately 10.8 K (at the coil edge) and 12.0 K (at the coil center) were achieved, with an axial temperature difference of approximately 1.2...

Design of a Structure for Assembly and Cooling the Magnet of the Next-Generation 45 GHz ECR Ion Source MARS-D

Wed, 11 Mar 2026 00:00:00 +0000

The current Electron Cyclotron Resonance Ion Sources (ECRISs), constructed with Nb-Ti wires and the conventional racetrack-and-solenoid structure, have achieved operating frequencies up to 28 GHz and utilized about 90% of the critical current of the Nb-Ti wire. A Mixed Axial and Radial field System Demonstrator (MARS-D) is being developed at Lawrence Berkeley National Laboratory (LBNL). This system, which consists of an innovative hexagonal Closed-Loop Coil (CLC) and a set of solenoids, can generate higher magnetic fields (up to 150% ) while requiring only about 50% of the superconducting wire, enabling Nb-Ti wires to be used in the next-generation 45 GHz ECRIS. However, the assembly and cooling of such an efficient and compact magnet are particularly challenging due to the small radial gap between the CLC and solenoids, as well as the tight operating temperature margin. To address these challenges, a structure was developed that combines a three-section radially split solenoid...

Test Results of the LQXFAB02 and LQXFAB03 Cryo-Assemblies for the High Luminosity LHC Upgrade

Wed, 4 Mar 2026 00:00:00 +0000

The US High-Luminosity LHC Accelerator Upgrade Project (AUP) is responsible for delivering cryo-assemblies for the Q1Q3 quadrupole optical components of the High Luminosity LHC upgrade at CERN. Total of 10 cryo-assemblies containing two Nb3Sn quadrupole magnets per cold mass will be delivered within this program. After the successful test of the first pre-series cryo-assembly in 2023, two more cryo-assemblies were tested at Fermilab's horizontal test facility. Production overview and the test results of the LQXFAB02 and LQXFAB03 cryo-assemblies are summarized in this paper. After the first test, to increase the capability of the horizontal test facility, various improvements have been made. These improvements are also described in this paper.

First Results on the Search for Lepton Number Violating Neutrinoless Double-β Decay with the LEGEND-200 Experiment

Tue, 10 Feb 2026 00:00:00 +0000

The LEGEND Collaboration is searching for neutrinoless double-beta ( ) decay by operating high-purity germanium detectors enriched in in a low-background liquid argon environment. Building on key technological innovations from the GERmanium Detector Array (GERDA) experiment and the MAJORANA DEMONSTRATOR experiment, LEGEND-200 has performed a first decay search based on 61.0 kg yr of data. Over half of this exposure comes from our highest performing detectors, including newly developed inverted-coaxial detectors, and is characterized by an estimated background level of in the decay signal region. A combined analysis of data from GERDA, the MAJORANA DEMONSTRATOR, and LEGEND-200, characterized by a 90% confidence level exclusion sensitivity of on the half-life of decay, reveals no evidence for a signal and sets a new observed lower limit at (90% confidence level). Assuming the decay is mediated by Majorana neutrinos, this corresponds to an upper limit on the effective...

Silicon wafer fracture stress for tracking sensors in particle physics experiments

Wed, 28 Jan 2026 00:00:00 +0000

For the construction of the ATLAS Inner Tracker strip detector, silicon strip sensor modules are glued directly onto carbon fibre support structures using a soft silicone gel. During tests at temperatures below -35°C, several of the sensors were found to crack due to a mismatch in coefficients of thermal expansion between polyimide circuit boards with copper metal layers (glued onto the sensor) and the silicon sensor itself. While module assembly procedures were developed to minimise variations between modules, cold tests showed a wide range of temperatures at which supposedly comparable modules failed. The observed variance (fracture temperatures between -35°C and -70°C) for supposedly comparable modules suggests an undetected variation between modules suspected to be intrinsic to the silicon wafer itself. Therefore, a test programme was developed to investigate the fracture stress of representative sensor wafer cutoffs. This paper presents results for the fracture stress of...

The High Rigidity Spectrometer at the FRIB: Magnet Development Status

Tue, 16 Dec 2025 00:00:00 +0000

This paper presents the 2025 progress of the High Rigidity Spectrometer (HRS) project at the Facility for Rare Isotope Beams (FRIB). We report on the construction and testing of the first-article HRS-High Transmission BeamLine (HTBL) magnets. An HTBL dipole magnet has successfully completed cold testing, achieving full magnetic performance without quenching, and is now ready for field mapping at FRIBs offline test bench. HTBL quadrupole triplet coils have been fabricated and tested, with all coils reaching their design currents, some following initial training quenches. Furthermore, the preliminary design of the large-scale, large-aperture SPectrometer Section (SPS) magnets has progressed to determine the baseline of the downstream HRS-SPS subproject in 2025. This includes the introduction of novel magnet designs, such as the sweeper dipole magnet, the sector dipole magnet, and iron-free coil-dominated quadrupole magnets, representing a significant scale breakthrough and a first...

A Computational Procedure for Assessing Ic(ε) in Nb3Sn/Bi-2212 Hybrid Magnets

Tue, 16 Dec 2025 00:00:00 +0000

The critical current of superconductors is commonly measured by testing unloaded wires under an external magnetic field. While stressed by intense Lorentz forces, the existing HTS/LTS superconductors are prone to a reduction in critical current before reaching their structural mechanical limit. In this work, the magnetic and mechanical analysis of the FNAL 4-layer Bi-2212/Nb_{3}Sn hybrid dipole magnet is reported, aimed at predicting the critical current degradation for both the superconductors during powering at 16T. All the Rutherford cables in the coils of the hybrid magnet were modeled at the strand level in Ansys APDL with the heterogeneous cable model. Utilizing this detailed geometry, it was possible to evaluate the effects of strain on the critical current degradation for both the Nb3 Sn and Bi-2212 superconductors under the intense Lorentz forces. The analysis presented in this paper integrates strain-dependent critical current laws, with parameters derived from experimental...

Electromagnetic modeling and science reach of DMRadio-m3

Mon, 8 Dec 2025 00:00:00 +0000

is an experimental search for dark matter axions. It uses a solenoidal dc magnetic field to convert an axion dark-matter signal to an ac electromagnetic response in a coaxial copper pickup. The current induced by this axion signal is measured by dc SQUIDs. is designed to be sensitive to Kim-Shifman-Vainshtein-Zakharov (KSVZ) and Dine-Fischler-Srednicki-Zhitnisky (DFSZ) QCD axion models in the 10–200 MHz ( ) range, and to axions with over 5–30 MHz as an extended goal. In this work, we present the electromagnetic modeling of the response of the experiment to an axion signal over the full frequency range of , which extends from the low-frequency, lumped-element limit to a regime where the axion Compton wavelength is only a factor of 2 larger than the detector size. With these results, we determine the live time and sensitivity of the experiment. The primary science goal of sensitivity to DFSZ axions across 30–200 MHz can be achieved with a live scan time of 2.9 ye...

Magnetic Field Mapping of a 2.5 T Fixed-Field HTS Gantry Magnet for Proton Therapy

Mon, 27 Oct 2025 00:00:00 +0000

We present results from testing a high-temperature superconducting (HTS) magnet prototype for proton therapy. This magnet is specifically designed for a novel rotating gantry capable of delivering the entire proton beam energy range (70225 MeV) while maintaining a fixed magnetic field in the superconducting magnets. The gantry layout simplifies the magnet design, enabling the use of straight, flat racetrack Bi-2223 (DI-BSCCO) coil technology and operation at higher temperatures (1015 K). The magnet has a non-linear field distribution for bending and focusing the proton beams. To validate this feature, we developed a system for measuring the magnetic field distribution in the magnet aperture. We present the design of this hall probe array and experimental results from two different magnet tests at 4.2 K in a liquid helium bath. These results are compared with the simulated field distribution and discussed in the context of the required field quality for the application.

Nanoscale detection of metastable states in porous and granular media

Mon, 13 Oct 2025 00:00:00 +0000

Microseismicity in subsurface geologic environments, such as sandstone gas reservoirs, is expected in the presence of liquid or gas injection. Although difficult to predict, the potential for microseismic events is important to field-scale projects, such as geologic storage of CO2, whereby the gas is injected into natural sandstone formations. We conjecture that a primary factor causing microseismicity is the existence of metastable states in a granular porous medium and provide experimental evidence for its validity. External perturbation triggers abrupt relaxation events which, with a certain probability, can grow into macroscopic microseismic events. Here, the triggering perturbation is produced by cooling to a cryogenic temperature. As the "sensor" for the abrupt relaxation events, we use thin Al films deposited on the sandstone surface. We show that as the temperature is varied, the films' resistance exhibits sharp jumps, which we attribute to mechanical restructuring or...

Noise limits for dc SQUID readout of high-Q resonators below 300 MHz

Fri, 10 Oct 2025 00:00:00 +0000

We present the limits on noise for the readout of cryogenic high-Q resonators using dc Superconducting Quantum Interference Devices (SQUIDs) below 300 MHz. This analysis uses realized first-stage SQUIDs (previously published), whose performance is well described by Tesche–Clarke (TC) theory, coupled directly to the resonators. We also present data from a prototype second-stage dc SQUID array designed to couple to this first-stage SQUID as a follow-on amplifier with high system bandwidth. This analysis is the first full consideration of dc SQUID noise performance referred to a high-Q resonator over this frequency range and is presented relative to the standard quantum limit. We include imprecision, backaction, and backaction–imprecision noise correlations from TC theory, the noise contributed by the second-stage SQUIDs, wiring, and preamplifiers, and optimizations for both on-resonance measurements and off-resonance scan sensitivity. This architecture has modern relevance due to...

Final report on Characterization of Nb3Sn Wires and Cables for the Test Facility Dipole Project (TFD)

Fri, 26 Sep 2025 00:00:00 +0000

Fermi National Accelerator Laboratory (FNAL) has an ongoing research program for characterization of superconducting wires. This includes expertise and special equipment to measure critical current of virgin and extracted strands over a broad range of current, magnetic field and temperature. These capabilities are required as part of comprehensive conductor characterization program for the Test Facility Dipole, a large bore, high field magnet under development to support future testing of large current cables and insert coils for Fusion Energy and High Energy Physics applications. The Test Facility Dipole is being developed at Lawrence Berkeley National Laboratory (LBNL) for installation in a newly commissioned High Field Vertical Magnet Test Facility (HFVMTF) at FNAL.

Irradiation-induced gas production in REBCO-based magnet materials used for future compact fusion reactors

Tue, 19 Aug 2025 00:00:00 +0000

Nuclear fusion is an enticing alternative to current sources of energy, with multilayered Rare-Earth Barium Copper Oxide (REBCO) coated conductors deemed pivotal in the race toward fully realized, commercially viable, and magnetic confinement fusion reactors. In this study, we simulated the ion spectrum expected to evolve from REBCO's nickel-based Hastelloy C-276 substrate and copper stabilizer in an affordable robust compact-like reactor. We then emulated this gas production through helium implantation to investigate changes in materials and superconducting properties. Our results revealed that the substrate and stabilizer are capable of producing protons energetic enough to recoil throughout the tape thickness in appreciable doses, and alphas energetic enough to deposit 7.54 × 1014 ions/cm2 or 50.1 helium appm in the superconducting layer over a 30-year reactor lifetime. The superconducting layer of SuperPower® tapes exhibited at least double the swelling rate of the other major...

Tape-in-tape-out (TITO): a new approach for in-situ contact resistance measurements in high temperature superconducting CORC® cables

Thu, 14 Aug 2025 00:00:00 +0000

One of the ongoing development challenges with ReBCO high-temperature superconducting (HTS) cables is normal zone initiation and local heating, which is associated with over-critical current flowing through and around local performance reductions in individual tapes. Although inter-tape contact resistances are well-reported for individual tapes and HTS cables, these measurements are a challenge in CORC® cables as current percolates through much of the cable. In this work, developments in tape-in-tape-out (TITO) automated individual tape powering experiments are presented, and a simplified modeling approach for current percolation in CORC® cables is developed. An optimization is formulated to fit the model parameters to a large set of TITO experiments on a single cable, allowing the layer-dependent inter-tape contact resistance to be extracted. Measurements are presented and discussed for a straight CORC® cable and a cable bent to a 152 mm and 76 mm radius. The approach provides...

A round bobbin critical current measurement and thermal runaway simulation of REBCO coated conductors

Mon, 28 Jul 2025 00:00:00 +0000

A round bobbin test has been widely used to measure critical current Ic of practical superconductors including Nb–Ti, Nb3Sn, and Bi-2212 round strands at 4.2 K and in high magnetic fields but rarely used for rare earth-barium-copper-oxide (REBCO) coated conductor tapes. Here, we applies this method to REBCO tapes and test their Ic at 77 K, self-field, and 4.2 K with a magnetic field of 14 T applied parallel to the tape. The sample carries very high current densities; it is 1.3 m long and has a dense array of voltage taps that allows probing localized thermal runaways and correlation with Ic variations along the length. At 77 K, the Ic values of all sections were measured and found to be rather uniform. However, at 4.2 K, we found that a 3 cm section has 90% of the overall voltage drop and it went into thermal runaways upon further increasing current. Thus, at 4.2 K, we were prevented by localized thermal runaways and unable to determine Ic of most of the REBCO conductor sections;...

Distributed fiber-optic sensing in a subscale high-temperature superconducting dipole magnet

Fri, 25 Jul 2025 00:00:00 +0000

High-temperature superconductors, such as REBa2Cu3O7−x (REBCO, RE = rare earth), are becoming pivotal for high-field magnet technology for future circular colliders and compact fusion reactors. The U.S. Magnet Development Program, in collaboration with industry, is developing REBCO magnet technology using round conductors consisting of multiple REBCO tapes. For these multi-tape cables, traditional instrumentation, such as voltage taps and resistive strain gauges, become insufficient to help measure and understand the performance-limiting factors in these model magnets. Distributed fiber-optic sensing (DFOS) is a potential solution to address this challenge. Although DFOS is well established for various applications, measuring temperature and strain in high-temperature superconducting magnets is in its infancy. Here we report the detailed implementation and test results of DFOS based on Rayleigh scattering in a subscale canted cosθ (CCT) dipole magnet using high-temperature superconducting...

Fabrication and Test of C3a: A Six-Layer Subscale Canted $\cos \theta$ Dipole Magnet Using High-Temperature Superconducting corc Wires

Wed, 21 May 2025 00:00:00 +0000

rebco coated conductors have a strong potential for high-field magnet applications. The rebco technology, however, is still in its infancy for accelerator magnet applications. As part of the U.S. Magnet Development Program, we developed a six-layer canted $\cos \theta$ dipole magnet, C3a, using corc wires developed by Advanced Conductor Technologies LLC. All the layers were wound using a semiautomated winding machine. Three layers of the magnet used corc wires containing the SuperPower AP rebco tapes and the remaining layers used the wires containing the HM tapes. At 77 K, both kinds of corc wires showed 5% to 10% degradation, after bending to a minimum bend radius of 30 or 35 mm, with respect to the self-field critical current measured before winding. At 4.2 K, the magnet reached 9.5 kA at a ramp rate of 9 A s$^{-1}$ and generated a dipole field of 1.4 T. The critical current of one layer degraded by 4% after a current transient up to 10.5 kA ramped in an averaged rate of 175...

A procedural solution for determining the temperature dependence of transport critical current in Nb3Sn superconducting wires using magnetization measurements

Tue, 20 May 2025 00:00:00 +0000

Using magnetization techniques to determine the temperature dependence of critical current in Nb3Sn wires is attractive because of the relative ease compared with using variable-temperature transport measurements. However, there is a known mismatch in the temperature scaling characterizations when using magnetization data compared to transport data. From a practical standpoint, it is the transport properties that matter, as performance prediction, margin calculations, and other aspects of magnet designs rely on the knowledge of the amount of transport current the superconductor can carry in a magnetic field. In this paper, we will identify the underlying issues and propose a procedural solution for determining the temperature dependence of transport critical current in Nb3Sn superconducting wires using magnetization measurements. By using one standard transport measurement at 4.2 K as an ‘anchor’, with this procedural solution it becomes possible to combine the simplicity and...

Processing of Low T C Conductors: The Compound Nb3Sn

Tue, 20 May 2025 00:00:00 +0000

Processing of Low T C Conductors: The Compound Nb3Sn

Microstructure Characterization of Nb3Sn Wires With Nanoprecipitate Artificial Pinning Centers Using Synchrotron High-Energy X-Rays

Thu, 10 Apr 2025 00:00:00 +0000

Synchrotron high-energy X-rays were used in an attempt to estimate nanoprecipitate size and size distribution in Nb3Sn powder-in-tube wires with ZrO2 or HfO2 artificial pinning centers via small angle X-ray scattering (SAXS). The effect of sample preparation was studied but measurements for as-received and for partially etched wires were not successful. Extracted sub-elements appeared to show more scattering contrast due to the lower number of phases, but no particle size could be extracted in this first attempt. Analysis of TEM data from the literature showed large particle size distribution (PSD) for different heat treatment conditions, suggesting that PSD could likely never be measured with SAXS due to a smeared signal. Experimental challenges with in-situ measurements revealed the sensitivity of infra-red furnaces and to changes in sample emissivity. The use of in-situ wide angle X-ray scattering data was successful in estimating the wire temperatures from the lattice parameter...

Crack Identification and Characterization in Deformed Nb3Sn Rutherford Cable Stacks Using Machine Learning

Thu, 10 Apr 2025 00:00:00 +0000

An investigation of instance segmentation of cracks in Nb3Sn 4-stack 40-strand Rutherford cables using machine learning is presented. Three samples were uniaxially and biaxially loaded before metallographic inspections were performed. The Mask R-CNN model was used in the Detectron2 framework with pre-trained weights but fine-tuned to detect and segment cracks. The model detected cracks with bounding box and mask average precisions (AP) of 42.8 and 27.9, respectively, and was used for instance segmentation of all cracks in the three samples. More cracks were found in the sample pre-loaded along the z-axis (i.e., along the cable length). Pre-loading along the x-axis (i.e., on the cables edges) reduced the number of cracks and changed the crack orientation distribution, away from being highly aligned with the y-axis (i.e., normal to the cables broad faces), i.e., the direction with the highest applied load. Fine-tuning of the Segment Anything Model (SAM) was also studied but performed...

Voltage-Current Behavior of a Superconducting star Wire in a 6-Around-1 Cable Configuration

Fri, 14 Feb 2025 00:00:00 +0000

A 6-around-1 transposed cable using superconducting star wires can be useful for future circular collider applications. We made three cable samples using single star wires with a diameter of 1.3 mm. The first two samples, made with a cabling machine, used star wires consisting of a 0.7 mm diameter Nb-Ti core. The third cable sample was manually wound and used a star wire made with a 0.81 mm diameter Cu core. The first sample showed severe degradation after the cable was bent to a 75 mm radius. The current-carrying capability of the innermost and outermost rebco tapes in the star wire degraded by 42 to 98 and the middle rebco tapes remained intact. This was also the case for the second and straight cable sample. After fabrication of the third cable sample, we observed only about 5 reduction in the current along the wire, measured at different locations inside the terminations. The results indicate that the differences in architecture or fabrication of the star wires could have...

A 6-around-1 cable using high-temperature superconducting STAR ® wires for magnet applications

Mon, 27 Jan 2025 00:00:00 +0000

To generate a dipole field above 20 T, we need high-temperature superconductors, including REBa2Cu3O 7 − x (RE = rare earth, rebco) coated conductors. However, the optimal architecture of a high-current flexible rebco cable is not yet settled for high-field magnet applications. Here we report a 6-around-1 cable concept based on the high-temperature superconducting star ® wires. We made two cable samples. One had a single star ® wire and the other had six star ® wires. The cable with six star ® wires was 1.5 m long. It had a diameter of 5.7 mm and a pitch length of 52 mm. The critical current of the cable before bending was 1448 A at 77 K, retaining at least 77% of the total critical current from individual star ® wires. The cable had a low n value around 4.5. At a bend radius of 30 mm, the critical current and n value remained the same as before bending. The total resistance of electrical terminations was 61 nΩ at 77 K. The flexible and transposed 6-around-1 star ® cable can provide...

Residual resistance ratio measurement system for Nb3Sn wires extracted from Rutherford cables

Mon, 13 Jan 2025 00:00:00 +0000

Residual resistance ratio (RRR) of superconducting strands is an important parameter for magnet electrical stability. RRR serves as a measure of the low-temperature electrical conductivity of the copper within a conductor that has a copper stabilization matrix. For Nb3Sn, due to the need of a reaction heat treatment, the technical requirements for high quality measurements of strands extracted from Rutherford cables are particularly demanding. Quality of wire, cabling deformation, heat treatment temperature, heat treatment atmosphere, sample handling, and measurement methods can all affect the RRR. Therefore, as an integral part of the electrical quality control (QC) of Nb3Sn Rutherford cables manufactured at the Lawrence Berkeley National Laboratory, it was prudent that we established a RRR measurement system that can isolate the assessment of cable-fabrication-related impacts from sample preparation and measurement factors. Here we describe a bespoke cryocooler-based measurement...

High-Field Magnets for Future Hadron Colliders

Wed, 13 Nov 2024 00:00:00 +0000

Recent strategy updates by the international particle physics community have confirmed strong interest in a next-generation energy frontier collider after completion of the High-Luminosity LHC program and construction of a e + e − Higgs factory. Both hadron and muon colliders provide a path toward the highest energies, and both require significant and sustained development to achieve technical readiness and optimize the design. For hadron colliders, the energy reach is determined by machine circumference and the strength of the guiding magnetic field. To achieve a collision energy of 100 TeV while limiting the circumference to 100 km, a dipole field of 16 T is required and is within the reach of niobium–tin magnets operating at 1.9 K. Magnets based on high-temperature superconductors may enable a range of alternatives, including a more compact footprint, a reduction of the cooling power, or a further increase of the collision energy to 150 TeV. The feasibility...

Updimensioning strategy derived from synthetic equiaxed grain structures for approximating 3D grain size distributions from 2D visualizations with 1D parameters

Sat, 9 Nov 2024 00:00:00 +0000

We generated synthetic equiaxed grain structures using computer graphics software to explore the relationship between various grain size determination methods and true three-dimensional (3D) grain diameters. Mirroring grain measurement techniques, the synthetic 3D grain structures are imaged as 2D micrographs which are measured to yield 1D grain size parameters. Synthetic grain structures provide data at a mass scale and permit exploration of both polished and fractured surface micrographs, revealing one-to-one correspondence between exposed 2D grain cross-sections and individual 3D grains. Analysis of this correspondence yielded a procedure to approximate 3D equiaxed grain size and volume distributions based on the mode of the 2D fractograph grain size distribution. The 3D approximation procedure is shown to be less susceptible to different imaging conditions that affect small, undiscernible grains compared to the standard planimetric and linear intercept methods, which by design...

Producing circular field harmonics inside elliptic magnet apertures with superconducting canted-cosine-theta coils

Mon, 12 Aug 2024 00:00:00 +0000

Superconducting magnets with noncircular aperture are desired for accelerators and many other high-field applications. This paper presents new methods for the analytic design of elliptic bore superconducting accelerator magnets. Part 1 of this work shares the derivation of current to field relations between a sheet current density on an elliptic cylinder and the magnetic field harmonics inside the aperture. This result is explored in the general context of elliptic bore magnet design with relevant scaling laws compared between elliptic and circular bore magnets. In part 2, this approach is applied to the specific geometry of canted-cosine-theta (CCT) accelerator magnets, enabling analytic winding design for single or mixed circular harmonics within elliptic aperture CCT magnets. Published by the American Physical Society 2024

Technological developments and accelerator improvements for the FRIB beam power ramp-up

Mon, 29 Jul 2024 00:00:00 +0000

The Facility for Rare Isotope Beams (FRIB) began operation with 1 kW beam power for scientific users in May 2022 upon completion of 8 years of project construction. The ramp-up to the ultimate beam power of 400 kW, planned over a 6-year period, will enable the facility to reach its full potential for scientific discovery in isotope science and applications. In December 2023, a record-high beam power of 10.4 kW uranium was delivered to the target. Technological developments and accelerator improvements are being made over the entire facility and are key to completion of the power ramp-up. Major technological developments entail the phased deployment of high-power beam-intercepting systems, including the charge strippers, the charge selection systems, the production target, and the beam dump, along with support systems, including non-conventional utilities (NCU) and remote handling facilities. Major accelerator improvements include renovations to aging legacy systems associated...

Quench protection for high-temperature superconductor cables using active control of current distribution

Mon, 22 Jul 2024 00:00:00 +0000

Superconducting magnets of future fusion reactors are expected to rely on composite high-temperature superconductor (HTS) cable conductors. In presently used HTS cables, current sharing between components is limited due to poorly defined contact resistances between superconducting tapes or by design. The interplay between contact and termination resistances is the defining factor for power dissipation in these cables and ultimately defines their safe operational margins. However, the current distribution between components along the composite conductor and inside its terminations is a priori unknown, and presently, no means are available to actively tune current flow distribution in real-time to improve margins of quench protection. Also, the lack of ability to electrically probe individual components makes it impossible to identify conductor damage locations within the cable. In this work, we address both problems by introducing active current control of current distribution...

A Possible Alternative Concept of HTS Accelerator Magnets

Tue, 21 May 2024 00:00:00 +0000

In this paper, we consider the advantages of an alternative design concept for HTS accelerator magnets operating at 20 K or above. The idea is primarily built on using REBCO tape as the main conductor, but may be applicable to other HTS. The key concepts are to align REBCO tapes in the most favourable field orientation and to make joints for every turn such that the tapes will not have to be wound over the saddle ends. We argue that such a concept involving resistive joints is viable at 20 K or above due to an increased cryogenic efficiency, and has multiple advantages that would more than compensate for the resistive heating cost penalty. First, the favourable tape orientation can allow a much higher current carrying capability. Second, the short unit length of tapes equal to the length of the magnet will be much more economical and can be specified at a higher performance than a long continuous piece equal to the number of turns multiplied by the length of the magnet. Third,...

Critical current and stability tests of Nb3Sn for LBNL CCT magnet project

Mon, 22 Apr 2024 00:00:00 +0000

Critical current and stability tests of Nb3Sn for LBNL CCT magnet project

Conceptual Design of a 20 T Hybrid Cos-Theta Dipole Superconducting Magnet for Future High-Energy Particle Accelerators

Thu, 21 Mar 2024 00:00:00 +0000

High energy physics research will need more and more powerful circular accelerators in the next decades. It is therefore desirable to have dipole magnets able to produce the largest possible magnetic field, in order to keep the machine diameter within a reasonable size. A 20 T dipole is considered a desired achievement since it would allow the construction of an 80 km machine, able to circulate 100 TeV proton beams. In order to reach 20 T, a hybrid Low-Temperature Superconductor (LTS) - High-Temperature Superconductor (HTS) magnet is needed, since LTS technology is presently limited to 16 T for accelerator magnet applications. In this paper, we present the design of a 6 layers 20 T hybrid dipole magnet using Nb3Sn (LTS) and Bi2212 (HTS). We show that it is possible to achieve this magnetic field with accelerator field quality, with sufficient margin on a realistic conductor, keeping the stresses within safe limit, avoiding conductor degradation.

A Review of the Mechanical Properties of Materials Used in Nb3Sn Magnets for Particle Accelerators

Wed, 20 Mar 2024 00:00:00 +0000

Superconducting magnets experience significant thermo-mechanical loads throughout their life cycle. These are introduced by the electro-magnetic forces during powering, but also by the prestress applied in many magnet designs. Further to this, the large thermal excursion that components of different materials experience can generate significant internal forces. The loads are also experienced by the superconducting coils, whose critical current can decrease as a consequence of the applied strain. It is then crucial to predict the overall mechanical behavior and conservatively design a magnet, avoiding failure of the mechanical components and of the superconducting coils. Finite Element Analysis (FEA) is generally used to perform these tasks, but its results rely heavily on the material properties and models used. This is in particular true for the coil composite, which is simplified to allow reasonable model sizes in full magnet models. In this paper, we present the state-of-art...

A Novel Design for Improving the Control on the Stainless-Steel Vessel Welding Process for Superconducting Magnets

Wed, 20 Mar 2024 00:00:00 +0000

Stainless steel vessels see widespread use in superconducting magnets for particle accelerator applications. Their function varies in different magnet designs: they always provide the necessary liquid helium containment, but in some cases are also used to provide azimuthal prestress and can also be welded to the magnet end plate to provide additional longitudinal stiffness. A magnet designed with the bladder and key technology does not rely on the structural role of the vessel. They are structurally supported using azimuthally prestressed aluminum shells, and the longitudinal constraint by rods. In this case, the magnet designer would generally like to minimize the interaction between the magnet and the stainless-steel vessel and to minimize the coil stress variation due to the vessel. The stress state in the vessel and in the coil is a function of the circumferential interference, defined as the vessel azimuthal length minus the magnet circumference. The vessel and the magnet...

Computation of the Strain Induced Critical Current Reduction in the 16 T Nb3Sn Test Facility Dipole

Wed, 20 Mar 2024 00:00:00 +0000

A test facility dipole is being developed at LBNL, targeting a 16 T field in a 144 mm wide aperture. The magnet uses a block design, with two double-pancake coils. In order to minimize motion under the large Lorentz forces, the coils are preloaded against a thick aluminum shell and iron yoke using bladder and key technology. It is then crucial to verify that the performance of the magnet is not degraded due to strain induced on the Nb3Sn conductor during assembly, cool-down and powering. The critical current of extracted strands was measured in a varying background magnetic field and as a function of the applied longitudinal strain. Finite element analysis was used to extract the strain state inside the superconducting strands during magnet assembly and operation. This strain was then compared to the measurements to evaluate potential reversible and irreversible effects on the magnet performances. The results suggest that the magnet can reach 16 T with sufficient margin, with...

Status of the High Field Cable Test Facility at Fermilab

Tue, 12 Mar 2024 00:00:00 +0000

Fermi National Accelerator Laboratory (FNAL) and Lawrence Berkeley National Laboratory (LBNL) are building a new High Field Vertical Magnet Test Facility (HFVMTF) for testing superconducting cables in high magnetic field. The background magnetic field of 15 T in the HFVMTF will be produced by a magnet provided by LBNL. The HFVMTF is jointly funded by the US DOE Offices of Science, High Energy Physics (HEP), and Fusion Energy Sciences (FES), and will serve as a superconducting cable test facility in high magnetic fields and a wide range of temperatures for HEP and FES communities. This facility will also be used to test high-field superconducting magnet models and demonstrators, including hybrid magnets, produced by the US Magnet Development Program (MDP). The paper describes the status of the facility, including construction, cryostat designs, top and lambda plates, and systems for powering, and quench protection and monitoring.

Eos: conceptual design for a demonstrator of hybrid optical detector technology

Tue, 27 Feb 2024 00:00:00 +0000

Eos is a technology demonstrator, designed to explore the capabilities of hybrid event detection technology, leveraging both Cherenkov and scintillation light simultaneously. With a fiducial mass of four tons, Eos is designed to operate in a high-precision regime, with sufficient size to utilize time-of-flight information for full event reconstruction, flexibility to demonstrate a range of cutting edge technologies, and simplicity of design to facilitate potential future deployment at alternative sites. Results from Eos can inform the design of future neutrino detectors for both fundamental physics and nonproliferation applications. This paper describes the conceptual design and potential applications of the Eos detector.

Development of the manufacturing and QA processes for the magnetic modules of the LCLS-II soft X-ray undulators

Thu, 19 Oct 2023 00:00:00 +0000

A new free electron laser being built at SLAC National Accelerator Laboratory, the Linear Coherent Light Source II (LCLS-II), will use 21 soft x-ray undulators (SXR) and 32 hard x-ray undulators (HGVPU). Lawrence Berkeley National Laboratory (LBNL) is responsible for the design and manufacturing of all variable-gap, hybrid permanent-magnet undulators. The physics requirements for the undulators specify a longitudinal pole misalignment maximum rms error of 25 µm and a vertical pole misalignment maximum error of 50 µm. In addition, magnet positioning critically influences the gap-dependent field properties due to saturation effects at the smallest operational gaps. This paper discusses the manufacturing and QA methods developed to carefully control the longitudinal and vertical pole and magnet positions during undulator production. Inspection results are discussed based on data gathered during construction of a prototype as well as pre-production soft x-ray undulator.

Applied Metrology for the Assembly of the Nb3Sn MQXFA Quadrupole Magnets for the HL-LHC AUP

Thu, 19 Oct 2023 00:00:00 +0000

The US HL-LHC Accelerator Upgrade Project (AUP) is building Nb3Sn quadrupole magnets, called MQXFA, with plans to install 16 of them in the HL-LHC Interaction Regions. Variability in coil size must be dealt with at the assembly level, which requires timely and repeatable measurement of each coil. In this paper we will present the methodology used for coil measurements and the geometrical size data for the coils that have been measured thus far. We will also show the coil measurements of 8 coils before and after cold test. The Leica AT960-MR laser tracker with Spatial Analyzer software acquired to achieve these measurements has been used elsewhere in the project to great effect.

Challenges and Lessons Learned From Fabrication, Testing, and Analysis of Eight MQXFA Low Beta Quadrupole Magnets for HL-LHC

Mon, 14 Aug 2023 00:00:00 +0000

By the end of October 2022, the US HL-LHC Accelerator Upgrade Project (AUP) had completed fabrication of ten MQXFA magnets and tested eight of them. The MQXFA magnets are the low-beta quadrupole magnets to be used in the Q1 and Q3 Inner Triplet elements of the High Luminosity LHC. This AUP effort is shared by BNL, Fermilab, and LBNL, with strand verification tests at NHMFL. An important step of the AUP QA plan is the testing of MQXFA magnets in a vertical cryostat at BNL. The acceptance criteria that could be tested at BNL were all met by the first four production magnets (MQXFA03-MQXFA06). Subsequently, two magnets (MQXFA07 and MQXFA08) did not meet some of the criteria and were disassembled. Lessons learned during the disassembly of MQXFA07 caused a revision to the assembly specifications that were used for MQXFA10 and subsequent magnets. In this article, we present a summary of: 1) the fabrication and test data for all the MQXFA magnets; 2) the analysis of MQXFA07A08 test results...

Design, fabrication, and characterization of a high-field high-temperature superconducting Bi-2212 accelerator dipole magnet

Fri, 16 Jun 2023 00:00:00 +0000

The use of high-field superconducting magnets has furthered the development of medical diagnosis, fusion research, accelerators, and particle physics. High-temperature superconductors enable magnets more powerful than those possible with Nb-Ti (superconducting transition temperature Tc of 9.2 K) and Nb3Sn (Tc of 18.4 K) conductors due to their very high critical field Bc2 of greater than 100 T near 4.2 K. However, the development of high-field accelerator magnets using high-temperature superconductors is still at its early stage. We report the construction of the world’s first high-temperature superconducting Bi2Sr2CaCu2Ox (Bi-2212 with Tc of ∼82 K) accelerator dipole magnet. The magnet is based on a canted-cosine-theta design with Bi-2212 Rutherford cables. A high critical current was achieved by an overpressure processing heat treatment. The magnet was constructed from a nine-strand Rutherford cable made from industrial 0.8 mm wires. At 4.2 K, it reached a quench current of...

Current distribution monitoring enables quench and damage detection in superconducting fusion magnets

Mon, 5 Jun 2023 00:00:00 +0000

Fusion magnets made from high temperature superconducting ReBCO CORC® cables are typically protected with quench detection systems that use voltage or temperature measurements to trigger current extraction processes. Although small coils with low inductances have been demonstrated, magnet protection remains a challenge and magnets are typically operated with little knowledge of the intrinsic performance parameters. We propose a protection framework based on current distribution monitoring in fusion cables with limited inter-cable current sharing. By employing inverse Biot-Savart techniques to distributed Hall probe arrays around CORC® Cable-In-Conduit-Conductor (CICC) terminations, individual cable currents are recreated and used to extract the parameters of a predictive model. These parameters are shown to be of value for detecting conductor damage and defining safe magnet operating limits. The trained model is then used to predict cable current distributions in real-time,...

High-Performance Bi-2212 Round Wires Made With Recent Powders

Fri, 26 May 2023 00:00:00 +0000

Multifilamentary Bi₂Sr₂CaCu₂O_x (Bi-2212) wire made by the powder-in-tube technique is the only high temperature superconductor made in the round shape preferred by magnet builders. The critical current density (J _C ) of Bi-2212 round wire was improved significantly by the development of overpressure heat treatment in the past few years. Bi-2212 wire is commercially available in multiple architectures and kilometer-long pieces and a very promising conductor for very high field NMR and accelerator magnets. We studied the effects of precursor powder and heat treatment conditions on the superconducting properties and microstructure of recent Bi-2212 wires. Short samples of recent wire with optimized overpressure processing showed J _C (4.2 K, 15 T) = 6640 A/mm² and J _C (4.2 K, 30 T) = 4670 A/mm², which correspond to engineering critical current...

Development of a modeling toolbox for CORC cable performance evaluation

Wed, 12 Apr 2023 00:00:00 +0000

Development of a modeling toolbox for CORC cable performance evaluation

Flux Creep in a Bi-2212 Rutherford Cable for Particle Accelerator Applications

Wed, 5 Apr 2023 00:00:00 +0000

Bi-2212 superconducting cables are being considered for use in the high field magnets needed for the next generation of particle accelerators. Magnetization in these cables and the decay of that magnetization lead to field error and field-error drift, respectively, which need to be compensated. To study this, a segment of the winding pack was extracted from a racetrack coil made from Bi-2212 Rutherford cable. Using a Hall probe measurement technique, we measured the response of the cable's magnetization and its magnetization decay to changes in the applied magnetic field. The effect of adjustments to the cycling of the magnetic field was studied, intended to simulate the preinjection cycles of an accelerator magnet. Three M vs. H loops were constructed by sweeping the magnetic field applied to the sample from 0 to 2.5 T, then to a preinjection field x (where x 0, 0.25, 0.75 T), and finally up to 1 T. The applied field was then held at 1 T for 1500 s, and the magnetization decay...

An initial magnet experiment using high-temperature superconducting STAR® wires

Mon, 27 Mar 2023 00:00:00 +0000

A dipole magnet generating 20 T and beyond will require high-temperature superconductors such as Bi2Sr2CaCu2O 8−x and REBa2Cu3O 7−x (RE = rare earth, rebco). Symmetric tape round (star®) wires based on rebco tapes are emerging as a potential conductor for such a magnet, demonstrating a whole-conductor current density of 580 A mm−2 at 20 T, 4.2 K, and at a bend radius of 15 mm. There are, however, few magnet developments using star® wires. Here we report a subscale canted cosθ dipole magnet as an initial experiment for two purposes: to evaluate the conductor performance in a magnet configuration and to start developing the magnet technology, leveraging the small bend radius afforded by star® wires. The magnet was wound with two star® wires, electrically in parallel and without transposition. We tested the magnet at 77 and 4.2 K. The magnet reached a peak current of 8.9 kA, 78% of the short-sample prediction at 4.2 K, and a whole-conductor current density of 1500 A mm−2. The experiment...

Magnetic Measurements of HL-LHC AUP Cryo-Assemblies at Fermilab

Mon, 20 Mar 2023 00:00:00 +0000

LQXFAB production series cryogenic assemblies are being built for the LHC upgrade by the HL-LHC Accelerator Upgrade Project (AUP). These contain a pair of MQXFA quadrupole magnets combined as a cold mass within a vacuum vessel, and are to be installed in the IR regions of the LHC. The LQXFAB are being tested at 1.9 K to assess alignment and magnetic performance at Fermilab's horizontal test facility. The 10 m long assembly must meet stringent specifications for quadrupole strength and harmonic field integrals determination, magnetic axis location, and for variations in axis position and local field profiles. A multi-probe, PCB-based rotating coil and a Single Stretched Wire system are employed for these measurements. To accurately determine rotating coil location and angles within the cold mass, a laser tracker is utilized to record multiple targets at one end of the probe. This paper describes the measurements, probesequipment, and techniques used to perform the necessary characterization...

Assembly and Pre-Loading Specifications for the Series Production of the Nb3Sn MQXFA Quadrupole Magnets for the HL-LHC

Wed, 8 Mar 2023 00:00:00 +0000

The High Luminosity LHC (HL-LHC) Project is planning to install 16 cold-masses made with Nb3Sn quadrupole magnets in the LHC Interaction Regions to significantly increase its luminosity. Half of these cold masses are fabricated at BNL, FNAL, and LBNL under the US Accelerator Research Program (AUP). Each cold mass includes two identical Nb3Sn quadrupole magnets, called MQXFA with a magnetic length of 4.2 m. Currently, the AUP project has completed the fabrication and test of the first 5 pre-series magnets, and is working on the following 16 magnets for the series production. The brittleness and strain sensitivity of the Nb3Sn superconducting material requires a careful definition of the allowable maximum stress in the windings during magnet assembly and pre-load, and a tight control of their variation within the whole coil length. Therefore, a series of assembly and pre-load specifications have been defined with the goals of minimizing the risk of conductor degradation and providing...

Magneto-Mechanical Optimization of Cross-Sections for $ \text{cos}(\theta)$Accelerator Magnets

Mon, 6 Mar 2023 00:00:00 +0000

The cross-sectiondesign of $\cos (\theta)$superconducting magnets is historically developed in a two-step process: initially, the coil geometry is defined on the basis of magnetic optimizations; then, the structure is designed around the coil. The first step searches for the best coil cross-section maximizing the magnetic field, margin, field quality and conductor efficiency. The latter step aims at limiting the coil stresses and deformations. However, the coil design, defined with the initial magnetic optimization, can influence the mechanical behaviour of the magnet, altering, for example, the peak stress during operation. As the critical current is a function of the applied strain, the mechanical implications of the coil cross-section design can limit the achievable performance. In this paper we propose an integrated optimization process that targets the peak stress on the conductor in addition to the magnetic objectives. The results are presented for a sample high-field Nb...

Towards 20 T Hybrid Accelerator Dipole Magnets

Wed, 15 Feb 2023 00:00:00 +0000

The most effective way to achieve very high collision energies in a circular particle accelerator is to maximize the field strength of the main bending dipoles. In dipole magnets using Nb-Ti superconductor the practical field limit is considered to be 8-9 T. When Nb3Sn superconductor material is utilized, a field level of 15-16 T can be achieved. To further push the magnetic field beyond the Nb3Sn limits, High Temperature Superconductors (HTS) need to be considered in the magnet design. The most promising HTS materials for particle accelerator magnets are Bi2212 and REBCO. However, their outstanding performance comes with a significantly higher cost. Therefore, an economically viable option towards 20 T dipole magnets could consist in an hybrid solution, where both HTS and Nb3Sn materials are used. We discuss in this paper preliminary conceptual designs of various 20 T hybrid magnet concepts. After the definition of the overall design criteria, the coil dimensions and parameters...

Carbon nanotube substrates enhance SARS-CoV-2 spike protein ion yields in matrix-assisted laser desorption–ionization mass spectrometry

Tue, 14 Feb 2023 00:00:00 +0000

Nanostructured surfaces enhance ion yields in matrix-assisted laser desorption–ionization mass spectrometry (MALDI-MS). The spike protein complex, S1, is one fingerprint signature of Sars-CoV-2 with a mass of 75 kDa. Here, we show that MALDI-MS yields of Sars-CoV-2 spike protein ions in the 100 kDa range are enhanced 50-fold when the matrix–analyte solution is placed on substrates that are coated with a dense forest of multi-walled carbon nanotubes, compared to yields from uncoated substrates. Nanostructured substrates can support the development of mass spectrometry techniques for sensitive pathogen detection and environmental monitoring.

An Initial Look at the Magnetic Design of a 150 mm Aperture High-Temperature Superconducting Magnet With a Dipole Field of 8 to 10 T

Tue, 14 Feb 2023 00:00:00 +0000

High-temperature superconducting REBa$_{2}$ Cu$_{3}$O$_{7-x}$ (rebco) conductors have the potential to generate a high magnetic field over a broad temperature range. The corresponding accelerator magnet technology, still in its infancy, can be attractive for future energy-frontier particle colliders such as a multi-TeV muon collider. To help develop the technology, we explore the requirements and potential characteristics of a rebco magnet, operating at 4.2 or 20 K, with a dipole field of 810 T in a clear aperture of 150 mm. We use the canted $\cos \theta$ magnet configuration to reduce the electromagnetic stresses on the conductors. We present the resulting dipole fields, field gradients for combined-function cases, conductor stresses, magnet dimensions and conductor lengths. We also discuss the conductor performance that is required to achieve the target dipole field at 4.2 and 20 K. The information can provide useful input to the development of rebco magnet and conductor technology...

The Majorana Demonstrator readout electronics system

Fri, 10 Feb 2023 00:00:00 +0000

The Majorana Demonstrator comprises two arrays of high-purity germanium detectors constructed to search for neutrinoless double-beta decay in 76Ge and other physics beyond the Standard Model. Its readout electronics were designed to have low electronic noise, and radioactive backgrounds were minimized by using low-mass components and low-radioactivity materials near the detectors. This paper provides a description of all components of the Majorana Demonstrator readout electronics, spanning the front-end electronics and internal cabling, back-end electronics, digitizer, and power supplies, along with the grounding scheme. The spectroscopic performance achieved with these readout electronics is also demonstrated.

Distributed Fiber Optic Sensing to Identify Locations of Resistive Transitions in REBCO Conductors and Magnets

Thu, 15 Dec 2022 00:00:00 +0000

High-temperature superconductors such as REBa2Cu3O7-x (REBCO, RE rare earth) can generate strong magnetic fields that are promising for applications in particle accelerators and compact fusion reactors. Traditionally, voltage taps are installed in superconducting magnets to measure the voltage signals due to resistive transitions. The voltage-tap-based diagnostics is important for the development of magnet technology as it can help pinpoint the locations in the magnet windings that limit the magnet performance. The architecture of the multi-tape REBCO cable such as CORC wires, however, makes it difficult to apply the voltage-tap-based diagnostics to identify the locations of resistive transitions. Distributed fiber optic sensing (DFOS) has the potential to address this issue. In this paper, we report the measurements of thermal strain along a CORC wire based on optical frequency domain reflectometry with a maximum spatial resolution of 0.65 mm and a temporal resolution of 10 Hz....

Analysis of Defect Irrelevancy in a Non-Insulated REBCO Pancake Coil Using an Electric Network Model

Thu, 15 Dec 2022 00:00:00 +0000

High-temperature superconducting REBCO coated conductor is one of the main candidates for next-generation high field magnets in fusion reactors and particle accelerators owing to their high current-carrying capability. Although these materials can operate at higher temperatures and generate higher magnetic fields than their counterparts with lower critical temperatures, protecting the REBCO magnet against quench is challenging. A variety of candidate technologies that may be able to enable self-protection, including no-insulation technology and insulative coatings with temperature-dependent resistance, are in development. In order to understand current sharing and thermal processes during a quench, we model a REBCO pancake coil as an electrical circuit, considering power generation and heat transfer along conductor turns, and study the current distribution around a local defect with lower critical current. The magnetic field and coil terminal voltage predicted by the simulation...

Mechanical and Thermal Analysis of an HTS Superconducting Magnet for an Achromatic Gantry for Proton Therapy

Wed, 17 Aug 2022 00:00:00 +0000

The mechanical and thermal analysis of the superconducting magnets, forming an innovative fixed-field bending section for use in a proton therapy gantry, is presented here. The design concept has a large momentum acceptance, covering the full proton energy range of 70 to 220 MeV with fixed field in the superconducting magnets, and uses a simple magnet geometry based on double-pancake high temperature superconductor coils. The main planned steps for the assembly and fabrication of the magnets are discussed. The mechanical analyses of the magnet, with emphasis on the stress state of the conductor during the powering of the magnet, is here described. The thermal analysis investigating the adequacy of the copper structure surrounding the conductor to extract the heat deposited in the conductor during powering is also discussed in detail.

Stabilization and control of persistent current magnets using variable inductance

Tue, 24 May 2022 00:00:00 +0000

Ultra-stable, tunable magnetic fields are desirable for a wide range of applications in medical imaging, electron microscopy, quantum science, and atomic physics. Superconducting magnets operated in persistent current mode, with device current flowing in a closed superconducting loop disconnected from a power source, are a common approach for applications with the most stringent requirements on temporal field stability. We present a method for active control of this persistent current by means of dynamic inductance change within the superconducting circuit. For a first realization of this general technique, we consider a variable superconducting inductor placed in series with the main magnet. The inductor acts as a dynamic flux storage device capable of transferring flux to or from the main magnet through inductance change. This allows for fine and fast adjustments of the persistent current without the use of thermal switches that limit the speed and accuracy of many present-day...

Shell-Based Support Structure for the 45 GHz ECR Ion Source MARS-D

Mon, 4 Apr 2022 00:00:00 +0000

Superconducting electron cyclotron resonance ion sources (ECRISs) using NbTi coils and optimized for 28 GHz resonant heating have been successfully operated for almost two decades. Moving to higher heating frequencies requires increased magnetic fields, but traditional racetrack-and-solenoid ECRIS structures are at their limit using NbTi. Rather than moving to a superconductor untested in this field, the Mixed Axial and Radial field System (MARS) being developed at Lawrence Berkeley National Laboratory employs a novel closed-loop-coil design that more efficiently utilizes conductor fields and will allow the use of NbTi in a next-generation, 45 GHz ECRIS. This article presents the design of the shell-based support structure central to the MARS-D magnet design, as well as structural analysis of its components and optimization of pre-load parameters that will guarantee its successful operation.

REBCO -- a silver bullet for our next high-field magnet and collider budget?

Wed, 30 Mar 2022 00:00:00 +0000

High-field superconducting magnets with a dipole field of 16 T and above enable future energy-frontier circular particle colliders. Although we believe these magnets can be built, none exists today. They can also be a showstopper for future high-energy machines due to a prohibitively high price tag based on the current conductor and magnet fabrication cost. The high-temperature superconducting REBCO coated conductor can address both the technical and cost issues, a silver bullet to lay both monsters to rest. The challenges and unknowns, however, can be too arduous to make the silver bullet. We lay out a potential road forward and suggest key action items. As a contribution from the accelerator community, we attempt to clarify for our theorist and experimenter colleagues a few aspects about the future high-field superconducting magnets. We hope to stimulate an effective plan for the 2023 P5 process that can lead to a cost-effective high-field magnet technology for future colliders...

Field Quality of the 4.5-m-Long MQXFA Pre-Series Magnets for the HL-LHC Upgrade as Observed During Magnet Assembly

Wed, 30 Mar 2022 00:00:00 +0000

The U.S. High-Luminosity LHC Accelerator Upgrade Project (HL-LHC AUP) is developing MQXFA magnets, a series of 4.5 m long 150 mm aperture high-field Nb$_{3}$Sn quadrupole magnets for the HL-LHC upgrade at CERN. Five pre-series magnets, MQXFA03 through MQXFA07, have been developed. During the magnet assembly stage, we perform magnetic measurements on the coil-pack sub-assembly and magnets after loading to track the field quality for two purposes. First, it serves as a quality assurance tool to check if the magnet field quality is on track to meet the acceptance criteria. Magnetic measurements are used to understand if magnetic shims are needed to compensate low-order field errors and to meet the field quality targets. Second, the measurements during the assembly stage can also help understand the field quality, especially the geometric field errors, for Nb$_{3}$Sn accelerator magnets. Here we summarize the measurement results of the pre-series MQXFA magnets, including the magnetic...

Cable Design and Development for the High-Temperature Superconductor Cable Test Facility Magnet

Wed, 16 Mar 2022 00:00:00 +0000

A large bore 'High-Temperature Superconductor Cable Test Facility Magnet' for testing advanced cables and inserts in high transverse field is in its design phase. This magnet will be the core component of a facility for developing conductors and accelerator magnets operating above 15 T, an enabling technology for next-generation fusion devices using magnetic confinement of plasma and for future energy frontier colliders. The procurement of Nb3Sn conductor, fabrication of cables, winding of coils, and assembly of the dipole magnet will be done at Lawrence Berkeley National Laboratory (LBNL) and the test pit and cryostat will be constructed at Fermi National Accelerator Laboratory. This article will present the conductor element of the LBNL project, specifically cable design parameters (based on the Bruker OST RRP^{\bigcirc \!\!\!\! {\hbox{R}}} Nb3Sn superconducting wire) and the development phase cable fabrication experience. Challenges of the cable fabrication will be discussed....

Developing a Vacuum Pressure Impregnation Procedure for CORC Wires

Tue, 8 Mar 2022 00:00:00 +0000

Superconducting magnets designed for high energy physics and nuclear fusion require mechanical and electrical integrity to perform at high currents and magnetic fields. Vacuum Pressure Impregnation (VPI), a process of curing epoxy in and around the superconducting wires, is often used to support and consolidate a magnet. However, the heat and mechanical stresses associated with the process can degrade the wires, significantly lowering their critical current. This study explores different methods of potting and curing CORC wire with the aim of reducing wire performance degradation to less than 3% measured at 77 K, self-field. The wires were 2.9 mm in diameter consisting of a total of six REBCO tapes (three layers of two tapes). Two bending radii (20 mm and 50 mm) were tested to mimic the winding shape of a magnet. Mix 61 epoxy was used in preliminary tests for potting. For each test, two wires were used, and their critical currents were measured simultaneously in liquid nitrogen...

3D Mechanical Analysis of a Compact ${\text{Nb}}_{\text{3}}{\text{Sn}}$ IR Quadrupole for EIC

Tue, 9 Nov 2021 00:00:00 +0000

The Electron Ion Collider (EIC) will require large aperture quadrupole magnets for the Hadron beam in the insertion region. Key requirements include high field, compact size, and tight control of the fringe fields. A 120mm aperture, 308.4mm outer diameter actively shielded ${\rm {Nb}}_{3}{\rm {Sn}}$ quadrupole model is under development to support these goals. This work is being carried out by a collaboration of BNL, JLAB and LBNL. A compact shell-based structure preloaded with a bladder and key system was developed for this project. In this paper, the effect of the compact structure on the mechanical behavior was investigated. In particular, the impact of the assembly tolerances and coil size variations on the actual coil stresses and bladder pressures was computed and compared with results from larger bladder and key structures developed for the LHC IR. The longitudinal preload is provided by stainless steel rods. Differently from other bladder and key magnets, the rods are...

Development and performance of a 2.9 Tesla dipole magnet using high-temperature superconducting CORC wires

Wed, 20 Oct 2021 00:00:00 +0000

Although the high-temperature superconducting (HTS) REBa2Cu3Ox (REBCO, RErare earth elements) material has a strong potential to enable dipole magnetic fields above 20 T in future circular particle colliders, the magnet and conductor technology needs to be developed. As part of an ongoing development to address this need, here we report on our CORC canted cos magnet called C2 with a target dipole field of 3 T in a 65 mm aperture. The magnet was wound with 70 m of 3.8 mm diameter CORC wire on machined metal mandrels. The wire had 30 commercial REBCO tapes from SuperPower Inc. each 2 mm wide with a 30 m thick substrate. The magnet generated a peak dipole field of 2.91 T at 6.290 kA, 4.2 K. The magnet could be consistently driven into the flux-flow regime with reproducible voltage rise at an engineering current density between 400550 A mm2, allowing reliable quench detection and magnet protection. The C2 magnet represents another successful step towards the development of high-field...

Inverse Biot–Savart Optimization for Superconducting Accelerator Magnets

Fri, 8 Oct 2021 00:00:00 +0000

Superconducting (SC) magnets for accelerator concepts are often synthesized by numerically optimizing magnetic field waveforms, a process that requires a subsequent solution of a constrained inverse problem to identify suitable SC magnet windings. When the desired field distribution is intuitive, the inverse process is facilitated by seeding preconceived coil distributions into design optimization methods for refinement. With more complex magnetic field distributions, an initial design may be unknown, and topology optimization tools are required to synthesize current distributions without a priori guidance from a subject matter expert. In this work, we develop a constrained inverse Biot–Savart topology optimization methodology that synthesizes optimal distributions of current density in racetrack-like SC coils. The problem structure is exploited through a computationally efficient quadratic programming formulation, and the method is applied to recently published magnetic field...

CORC ® cable terminations with integrated Hall arrays for quench detection

Tue, 4 May 2021 00:00:00 +0000

ReBCO superconducting cables have the potential to enable compact thermonuclear fusion reactors that operate at magnetic fields exceeding 20 T and allow operation at temperatures far exceeding the boiling point of liquid helium, potentially allowing for demountable magnets. Normal zone detection remains a challenge, and while novel quench detection techniques are an active area of research, few are non-invasive, provide real-time quench detection, and have been demonstrated with current ramp rates relevant for fusion reactors. To address this problem, a CORC ® cable termination is developed with integrated Hall sensors to monitor current redistribution as a proxy for quench detection. The methodology exploits the current sharing and layered topology in CORC ® cables, and allows quench detection using a localized sensor instead of co-wound voltage wires or optical fibers. Experiments are presented where current redistribution is measured from induced quenches, and in a 0.2 meter...

Design of a High Toughness Epoxy for Superconducting Magnets and Its Key Properties

Fri, 30 Apr 2021 00:00:00 +0000

Nb3Sn accelerator magnets are poised to enable the luminosity upgrade of the Large Hadron Collider (LHC) at CERN, improving its potential for exploring physics beyond the standard model of particle physics. The prototype Nb3Sn magnets consistently need 1025 quenches to achieve their best performance. A hypothesis is that the long training of these magnets may at least be partially induced by epoxy cracking and bonding failures. In 2018, we showed that several existing epoxies have a higher toughness and less tendency to crack at low temperatures than CTD-101K, the epoxy resin with which almost all Nb3Sn accelerator magnets have been impregnated. Here we explore a new high toughness formulation for reducing quench training of Nb3Sn accelerator magnets, through combining two amine curing agents to achieve a good glass transition temperature $(T_{g})$, adding a viscosity reducer to achieve low viscosity, and experimenting a coupling agent for improved bonding strengths. We report...

A methodology to compute the critical current limit in Nb3Sn magnets

Tue, 16 Feb 2021 00:00:00 +0000

Numerous experiments have shown that the loads applied to Nb3Sn strands and cables can reduce their critical current. Experiments, performed on uniaxially loaded strands, allowed to define clear laws to describe the evolution of the critical surface as a function of the applied current, field, temperature and strain. It is, however, still unclear how these laws can be applied to superconducting magnets. The present paper proposes a methodology to estimate the critical current and temperature margin reduction on superconducting magnets due to stress on the superconducting material. The methodology is tested on the MQXF magnets, a quadrupole developed for the High Luminosity LHC project, and successfully validated by comparing computed strain with data from strain gauge measurements. Results suggested that, because of the stresses arising in winding during assembly, cool-down and powering, the current limit of the magnet is lower than the expected short sample limit, and that the...

The ABC130 barrel module prototyping programme for the ATLAS strip tracker

Thu, 7 Jan 2021 00:00:00 +0000

For the Phase-II Upgrade of the ATLAS Detector [1], its Inner Detector, consisting of silicon pixel, silicon strip and transition radiation sub-detectors, will be replaced with an all new 100% silicon tracker, composed of a pixel tracker at inner radii and a strip tracker at outer radii. The future ATLAS strip tracker will include 11,000 silicon sensor modules in the central region (barrel) and 7,000 modules in the forward region (end-caps), which are foreseen to be constructed over a period of 3.5 years. The construction of each module consists of a series of assembly and quality control steps, which were engineered to be identical for all production sites. In order to develop the tooling and procedures for assembly and testing of these modules, two series of major prototyping programs were conducted: an early program using readout chips designed using a 250 nm fabrication process (ABCN-250) [2,2] and a subsequent program using a follow-up chip set made using 130 nm processing...

A new quench detection method for HTS magnets: stray-capacitance change monitoring

Thu, 17 Dec 2020 00:00:00 +0000

Abstract Fast quench detection is a key requirement for the successful implementation of superconducting magnet technology. In high temperature superconductor (HTS) magnets, this issue is especially challenging due to the low quench propagation velocity, and presently represents one of the main factors limiting their application. A new detection technique based on stray-capacitance monitoring is proposed. The capacitance between electrically-insulated magnet elements, such as magnet structure and end parts, is utilized as an indication of local heat deposition in the conductor. In fact, the relative permittivity of helium drops when it changes from the liquid to the gaseous phase. Thus, when heating occurs, part of the helium impregnating the insulation layers boils off, and the monitored stray-capacitance decreases. The proposed technique is successfully demonstrated on three small-scale Bi-2212 magnets manufactured at the Lawrence Berkeley National Laboratory. Results from the...

Thermoeconomic cost optimization of superconducting magnets for proton therapy gantries

Wed, 21 Oct 2020 00:00:00 +0000

A compact gantry delivering 70-220 MeV protons with fixed field in the superconducting magnets could reduce the cost and improve the adoption of proton therapy. While a number of magnet and cryogenics designs have been proposed, the combined capital and operating costs of state-of-the-art superconducting materials have not been analyzed. In response, we develop a thermoeconomic model of a multi-stage, conduction cooled gantry lattice and analyze the cryocooler operating cost, cryocooler capital cost and conductor capital cost for Nb-Ti, Nb3Sn, REBCO and Bi-2223 over a continuous range of magnet temperatures, and a differential evolution algorithm is used to identify the optimal combination of thermal intercept temperatures. Although Nb3Sn yields the lowest Net Present Value (NPV) of 111.7k at a magnet temperature of 9.4 K, the optimized Bi-2223 design at 12.8 K approaches the realm of commercial feasibility by offering improved thermal stability and forgoing the need for costly...

Vanadium oxide coatings to self-regulate current sharing in high-temperature superconducting cables and magnets

Mon, 24 Aug 2020 00:00:00 +0000

High-temperature superconductors such as REBa2Cu3O7 − δ (REBCO, RE = rare earth) enable high-current cables and high-field magnets. By removing the turn-to-turn insulation in a magnet application, recent experiments demonstrated that REBCO magnets can self-protect against catastrophic damage during a superconducting-to-normal transition (quench), i.e., when the stored magnetic energy rapidly converts to heat. The current can bypass the hot spot during a quench, thereby reducing the localized heat dissipation. The removal of the insulation between turns, however, leads to excessive eddy currents during current ramping, thereby forcing a much-prolonged magnet charging time. To address this issue, we investigate vanadium oxide (VOx) coatings as a temperature-dependent self-switching medium that automatically manages current sharing. VOx coatings (with 1.70 ≤ × ≤ to 2.07) were deposited by reactive cathodic arc deposition, initially on insulating glass to determine the electrical...

Demonstration of cooling by the Muon Ionization Cooling Experiment

Mon, 13 Jul 2020 00:00:00 +0000

The use of accelerated beams of electrons, protons or ions has furthered the development of nearly every scientific discipline. However, high-energy muon beams of equivalent quality have not yet been delivered. Muon beams can be created through the decay of pions produced by the interaction of a proton beam with a target. Such ‘tertiary’ beams have much lower brightness than those created by accelerating electrons, protons or ions. High-brightness muon beams comparable to those produced by state-of-the-art electron, proton and ion accelerators could facilitate the study of lepton–antilepton collisions at extremely high energies and provide well characterized neutrino beams1–6. Such muon beams could be realized using ionization cooling, which has been proposed to increase muon-beam brightness7,8. Here we report the realization of ionization cooling, which was confirmed by the observation of an increased number of low-amplitude muons after passage of the muon beam through an absorber,...

An Electric-Circuit Model on the Inter-Tape Contact Resistance and Current Sharing for REBCO Cable and Magnet Applications

Sun, 10 May 2020 00:00:00 +0000

REBCO coated conductor has demonstrated high current capacity that can enable high-field magnets for high energy physics and fusion applications. However, quench protection is still one of the main challenges to be addressed for these applications. In addition, ${I}_{\text{c}}$ and $n$ value variations along the length of REBCO tapes exist in commercial production. The inter-tape contact resistance plays a key role to develop the self protection capability in cables and magnets by enabling current sharing and suppressing excessive eddy currents. Here we propose an electric-circuit model to describe the inter-tape contact resistance and its impact on the current sharing between REBCO tapes. We report the experiments on a 2-stacked tape REBCO cable with local ${I}_{\text{c}}$ drop to validate the model. With the developed model, we study the upper limit of the contact resistance which allows current sharing between tapes. We also study the impact of variation in ${I}_{\text{c}}$...

High Temperature Superconductor Cable Test Facility Specifications

Tue, 7 Apr 2020 00:00:00 +0000

High Temperature Superconductor Cable Test Facility Specifications

Design Options for the JLEIC Large Aperture IR Quadrupoles

Tue, 7 Apr 2020 00:00:00 +0000

Design Options for the JLEIC Large Aperture IR Quadrupoles

Mitigation of persistent current effects in the RHIC superconducting magnets

Fri, 13 Mar 2020 00:00:00 +0000

Persistent currents in superconducting magnet introduce magnetic errors especially at low operating fields. In addition, their decay causes magnetic field variations and therefore drifts of the beam orbits, tunes, and chromaticities. To reduce field errors and suppress magnetic field variations, a new magnetic cycle was proposed for the low-energy beam operation at the Relativistic Heavy Ion Collider (RHIC). In the new magnetic cycle, the magnet current oscillates around the nominal operating current with diminishing amplitude a few times before it settles. The new magnetic cycle has been demonstrated experimentally to reduce field errors and the amplitude of magnetic field variations significantly and is essential for the ongoing RHIC Beam Energy Scan II (BES-II) program. This article will present beam-based experimental studies of the persistent current effects with the new magnetic cycle, and discuss its application in RHIC.

Superconducting Magnets for Particle Accelerators

Tue, 10 Dec 2019 00:00:00 +0000

In this paper we summarize the evolution and contributions of superconducting magnets to particle accelerators as chronicled over the last 50 years of Particle Accelerator Conferences (PAC, NA-PAC and IPAC). We begin with an historical overview based primarily on PAC Proceedings augmented with references to key milestones in the development of superconducting magnets for particle accelerators. We then provide some illustrative examples of applications that have occurred over the past 50 years, focusing on those that have either been realized in practice or provided technical development for other projects, with discussion of possible future applications.

Dipole Magnets above 20 Tesla: Research Needs for a Path via High-Temperature Superconducting REBCO Conductors

Wed, 27 Nov 2019 00:00:00 +0000

To enable the physics research that continues to deepen our understanding of the Universe, future circular colliders will require a critical and unique instrument—magnets that can generate a dipole field of 20 T and above. However, today’s maturing magnet technology for low-temperature superconductors (Nb-Ti and Nb3Sn) can lead to a maximum dipole field of around 16 T. High-temperature superconductors such as REBCO can, in principle, generate higher dipole fields but significant challenges exist for both conductor and magnet technology. To address these challenges, several critical research needs, including direct needs on instrumentation and measurements, are identified to push for the maximum dipole fields a REBCO accelerator magnet can generate. We discuss the research needs by reviewing the current results and outlining the perspectives for future technology development, followed by a brief update on the status of the technology development at Lawrence Berkeley National Laboratory....

A new quench detection method for HTS magnets: stray-capacitance change monitoring

Wed, 13 Nov 2019 00:00:00 +0000

Superconducting ECR ion source: From 24-28 GHz SECRAL to 45 GHz fourth generation ECR