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At least 37 records · Page 2

Commissioning of an MPGD-based Drift Chamber for Heavy-ion Tracking in FRIB's Sweeper magnet system

A newly developed drift chamber equipped with an innovative hybrid Micro-Pattern Gaseous Detector based readout was commissioned at FRIB. The detector consists of a Multi-layer Thick Gas Electron Multiplier (M-THGEM) mounted over a high-granularity, position-sensitive readout board. Denoted as the Micro-Pattern Drift Chamber (MPDC), the new device is used to provide tracking capability as part of the detectors of the Sweeper magnet system for neutron-invariant-mass spectrometry at the Facility for Rare Isotope Beams (FRIB). The localization of impinging ions in a 30 × 30 cm 2 drift area is derived by processing the charge-avalanche distribution induced on the segmented readout board. The signals induced on the readout pads are processed by a compact, multi-channel Data Acquisition System (DAQ) based on the Scalable Readout System (SRS). To facilitate synchronization with other detector systems of the Sweeper magnet system, the SRS has been configured to accept an external trigger.

Gaseous detectors↗

Room temperature long range ferromagnetic ordering in Ni{sub 0.58}Zn{sub 0.42}Co{sub 0.10}Cu{sub 0.10}Fe{sub 1.8}O{sub 4} nano magnetic system

The structural and magnetic behavior of sol-gel autocombustion synthesized nanocrystalline Ni{sub 0.58}Zn{sub 0.42}Co{sub 0.10}Cu{sub 0.10}Fe{sub 1.8}O{sub 4} have been investigated by X-ray diffraction (XRD), transmission electron microscopy (TEM), Mössbauer spectroscopy and vibrating sample magnetometer(VSM). Sample of high purity and high homogeneity was obtained by calcination at low temperature (500°C) resulting in nanoparticles of average diameter ∼15nm as determined by XRD and further confirmed by TEM. X-ray diffraction (XRD) and selective area diffraction (SAED) confirmed the single phase of the sample. Mössbauer results are supported by magnetization data. Well defined sextets and appearance of hysteresis at room temperature indicate the existence of ferromagnetic coupling at room temperature finding material utility in magnetic storage data. The existence of iron in ferric state confirmed by isomer shift is a clear evidence of improved magnetic properties of the present system.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗

Thermal Analysis and Simulations of the Abort Kicker Magnets Systems for the Electron-Ion Collider

The Abort Kicker Magnets system used in the current Relativistic Heavy Ion Collider (RHIC) to steer the circulating beam into the dump will be subjected to higher heat loads in the Electron-Ion Collider (EIC). After analyzing the existing abort kicker magnets and running thermal simulations in ANSYS it was concluded that they may not be suitable for use as-is in the future EIC due to heat and impedance concerns in the magnets. Possible solutions include adding a round titanium-coated ceramic beam tube to help solve the heat and impedance concerns, but this will reduce the limiting aperture of the kicker magnet. Another possible solution to meet all the performance requirements for EIC would be to add titanium-coated ceramic plates with water-cooling and tapered transitions that significantly improve the impedance and lower the heat in the magnets with less reduction to the aperture.

43 PARTICLE ACCELERATORS↗

Design of a New Superconducting Magnet System for High Strength Minimum-B Fields for ECRIS

A novel Mixed Axial and Radial field System (MARS) seeks to enhance the B fields inside the plasma chamber within the limits of a given conductor, thereby making it possible to raise the operating fields for Electron Cyclotron Resonance Ion Sources (ECRISs). The MARS concept consists of a hexagonally shaped closed-loop coil and a set of auxiliary solenoids. The application of MARS will be combined with a hexagonal plasma chamber to maximize the use of the radial fields at the chamber inner surfaces. Calculations using Opera's TOSCA-3D solver have shown that MARS can potentially generate up to 50% higher fields and use of only about one half of the same superconducting wire, as compared with existing magnet designs in ECRISs. A MARS magnet system built with Nb 3 Sn coils could generate a high strength minimum-B field of maxima of ≥ 10 T on axis and ~6 T radially in an ECRIS plasma chamber. Following successful development, the MARS magnet system will be the best magnet scheme for the next generation of ECRISs. This paper will present the MARS concept, magnet design, prototyping a copper closed-loop coil, and discussions.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗

SPY: a conceptual design study of a magnet system for a high-pressure gaseous TPC neutrino detector

Here, we present a novel conceptual design for a magnet system that provides the magnetic field necessary for the analysis of tracks in a high-pressure gaseous argon TPC while simultaneously serving as a pressure vessel to contain the TPC gas volume. The magnet was developed within a Near Detector proposal for the Deep Underground Neutrino Experiment (DUNE). The high-pressure gaseous argon TPC is a component proposed to be one of the elements of an ensemble of near detectors that are needed for DUNE.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗

SU-F-T-211: Evaluation of a Dual Focusing Magnet System for the Treatment of Small Proton Targets

Purpose: To investigate magnetic focusing for small volume proton targets using a doublet combination of quadrupole rare earth permanent magnet Halbach cylinder assemblies Methods: Monte Carlo computer simulations were performed using the Geant4 toolkit to compare dose depositions of proton beams transported through two focusing magnets or in their absence. Proton beams with energies of 127 MeV and initial diameters of 5, 8 and 10 mm were delivered through two identical focusing magnets similar to those currently in experimental use at Loma Linda University Medical Center. Analogous experiments used optimized configurations based on the simulation results. Dose was measured by a diode detector and Gafchromic EBT3 film and compared to simulation data. Based on results from the experimental data, an additional set of simulations was performed with an initial beam diameter of 18 mm and a two differing length magnets (40mm & 68mm). Results: Experimental data matched well with Monte Carlo simulations. However, under conditions necessary to produce circular beam spots at target depth, magnetically focused beams using two identical 40 mm length magnets did not meet all of our performance criteria of circular beam spots, improved peak to entrance (P/E) dose ratios and dose delivery efficiencies. The simulations using the longer 68 mm 2nd magnet yielded better results with 34% better P/E dose ratio and 20–50% better dose delivery efficiencies when compared to unfocused 10 mm beams. Conclusion: While magnetic focusing using two magnets with identical focusing power did not yield desired results, ongoing Monte Carlo simulations suggest that increasing the length of the 2nd magnet to 68 mm could improve P/E dose ratios and dose efficiencies. Future work includes additional experimental validation of the longer 2nd magnet setup as well as experiments with triplet magnet systems. This project was sponsored with funding from the Department of Defense (DOD# W81XWH-BAA-10-1).

60 APPLIED LIFE SCIENCES↗

A Bulk Superconducting Magnetic System for the CLAS12 Target at Jefferson Lab

A feasibility study of a bulk magnetic system for the target of an experiment to measure the transverse spin effects in semi-inclusive deep inelastic scattering (SIDIS) at 11 GeV with a transversely polarized target using the CLAS12 detector is presented. An experiment has been approved with the highest priority rating to study spin azimuthal asymmetries in SIDIS using 11-GeV polarized electron beams from the upgraded CEBAF facility and the CLAS12 detector equipped with a transversely polarized target. The transverse target in CLAS12 requires the shielding of a volume inside the longitudinal field of the main solenoid. In the shielded region, a transverse target magnet can operate; for the proposed magnetic configuration, the main solenoid maximum magnetic induction is 2 T. A bulk MgB 2 cylinder cooled in liquid helium is proposed both to shield the longitudinal field of the main solenoid and to provide a transverse field induction up to 1.2 T for the hydrogen deuteride ice (HD-ice) target. The installation and magnetization procedure will be described. The magnetization procedure has to be compatible with the polarization and installation procedure of the HD-ice target. The design of a test bench to measure the transverse magnetization of a MgB2 bulk cylinder cooled by a coldhead is presented together with the scheduled measurements.

43 PARTICLE ACCELERATORS↗

A Dual 5T Superconducting Magnet System for the Brookhaven National Lab Electron Beam Ion Source

Cryomagnetics has delivered an upgraded magnet system to the Brookhaven National Laboratory's RHIC Electron Beam Ion Source project. This consists of two 2.25-m long, 215-mm room temperature bore 5T solenoids separated by 20 cm. The initial system used a single PT-415RM cryocooler but was unstable a long term. As a result, the new system adds a second SHI cryocooler, which produces much higher recondensing margins.

43 PARTICLE ACCELERATORS↗

Conceptual Design of DUNE Near Detector Superconducting Magnet System

The Deep Underground Neutrino Experiment (DUNE) has formed a near detector design group (NDDG) tasked with delivering a CDR by the end of 2019. The DUNE Near Detectors will be housed in an underground hall on the Fermilab site. The two main detector systems are a liquid argon detector and a high-pressure gas time projection chamber (HPgTPC). The HPgTPC requires a magnet that generates a 0.5 T solenoidal magnetic field in a large volume of 6 m diameter, and 5 m length. Herein, we present a superconducting magnet system design. We investigated: an open air core magnet with three coils, and a five coils system having two active fringe field shielding coils. Coils positions were optimized to obtain the specified field homogeneity in the magnet good field region, while minimizing the Lorentz forces and the superconductor volume. We discuss the magnetic, mechanical, and thermal conceptual designs.

43 PARTICLE ACCELERATORS↗

Initial performance of the magnet system in the splitter/combiner section of the Cornell-Brookhaven Energy-Recovery Linac Test Accelerator

The Cornell-Brookhaven Energy-recovery Linac Test Ac- celerator is a four-pass, 150-MeV electron accelerator with a six-cell 1.3 GHz superconducting-RF linear accelerator and a fixed-field alternating-gradient (FFAG) return loop made up of Halbach-style quadrupole magnets. The optics matching between the linear accelerator and the return loop is achieved with a conventional magnet system comprised of 50 dipole magnets and 64 quadrupole magnets in four beamlines at each end of the linac. The 42-, 78-, 114- and 150-MeV electron beams are separated into independent vacuum chambers in order to allow for the path-length ad- justment required by energy recovery. We report on the first beam tests of the initial installation of the splitter/combiner section at the exit of the linac. The vacuum system of the 42-MeV S1 line was installed during the first week of April. Nine dipole and four quadrupole magnets were installed and surveyed into position the following week, and the water cooling system was commissioned. A 6-MeV beam passed through the line on April 11 with no need for adjusting pre-set magnet excitation currents. One week later, time- of-flight measurements were used to calibrate and phase the individual superconducting RF cavities. The S1 magnet settings were then scaled up to achieve 5-cavity, 42-MeV operation through the first nine FFAG permanent-magnet quadrupoles. This initial Fractional Arc Test will conclude on May 18, when the installation of the remaining seven split- ter/combiner lines and the return loop will begin. CBETA operations are scheduled to begin in early 2019.

43 PARTICLE ACCELERATORS↗

Spin-liquid behavior of the three-dimensional magnetic system Ba 3 NiIr 2 O 9 with S = 1

The quantum spin liquid (QSL) is an exotic phase of magnetic materials where the spins continue to fluctuate without any symmetry breaking down to zero temperature. Among the handful reports of QSL with spin S ≥ 1, examples with magnetic ions on a three-dimensional (3D) magnetic lattice are extremely rare since both larger spin and higher dimension tend to suppress quantum fluctuations. In this work, we offer a new strategy to achieve 3D QSL with high spin by utilizing two types of transition metal ions; both are magnetically active but located at crystallographically inequivalent positions. Furthermore, we design a 3D magnetic system Ba 3 NiIr 2 O 9 consisting of interconnected corner-shared NiO 6 octahedra and face-shared Ir 2 O 9 dimer, both having triangular arrangements in a-b plane. X-ray absorption spectroscopy measurements confirm the presence of Ni 2+ (S = 1). Furthermore, our detailed thermodynamic and magnetic measurements reveal that this compound is a realization of gapless QSL state down to at least 100 mK. Ab initio calculations find a strong magnetic exchange between Ir and Ni sublattices and in-plane antiferromagnetic coupling between the dimers, resulting in dynamically fluctuating magnetic moments.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗

Current-carrying element based on second-generation high-temperature superconductor for the magnet system of a fusion neutron source

Application of current-carrying elements (CCEs) made of second-generation high-temperature superconductor (2G HTS) in magnet systems of a fusion neutron source (FNS) and other fusion devices will allow their magnetic field and thermodynamic stability to be increased substantially in comparison with those of low-temperature superconductor (LTS) magnets. For a toroidal magnet of the FNS, a design of a helical (partially transposed) CCE made of 2G HTS is under development with forced-flow cooling by helium gas, a current of 20–30 kA, an operating temperature of 10–20 K, and a magnetic field on the winding of 12–15 T (prospectively ∼20 T). Short-sized samples of the helical flexible heavy-current CCE are being fabricated and investigated; a pilot-line unit for production of long-sized CCE pieces is under construction. The applied fabrication technique allows the CCE to be produced which combines a high operating current, thermal and mechanical stability, manufacturability, and low losses in the alternating modes. The possibility of fabricating the CCE with the outer dimensions and values of the operating parameter required for the FNS (and with a significant margin) using already available serial 2G HTS tapes is substantiated. The maximum field of toroidal magnets with CCEs made of 2G HTS will be limited only by mechanical properties of the magnet’s casing and structure, while the thermal stability will be approximately two orders of magnitude higher than that of toroidal magnets with LTS-based CCEs. The helical CCE made of 2G HTS is very promising for fusion and hybrid electric power plants, and its design and technologies of production, as well as the prototype coils made of it for the FNS and other tokamaks, are worth developing now.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗

Structural and magnetic properties of hard magnetic system Ce(Co 1 -Fe ) 4.4 Cu 0.6 (0 ≤ x ≤ 0.19)

The Ce(Co 1 -Fe ) 4.4 Cu 0.6 (0 ≤ x ≤ 0.19) is a composite, hard magnetic system that is based on the CaCu 5 -type structure (1:5). It shows both, unique magnetic and microstructural features that are essential for permanent magnets, e.g., exceptional squareness of the 2nd. quadrant of the magnetization loops and microstructural features typically needed for pinning. Samples solidified in alumina crucibles are coarse-grained and often clearly faceted and readily align in a magnetic field. X-ray, SEM, and TEM analyses show a 1:5-type single-phase material when quenched from high temperature, which, after heat treatment, transforms into a laminar coherent nanostructure through the formation of a dense array of extended intercalated regions. Furthermore, these extended intercalated regions are comprised of segments of the Ce 2 Ni 7 –type structure (2:7) which segregate into various closely related precipitates forming a nanostructure similar to the SmCo 5 - Sm 2 Co 17 composites seen in Sm-Co permanent magnets. Based on TEM and Lorentz microscopy of well-aligned single grain particles, the magnetic domains’ reversal mechanism is regulated by anisotropy fluctuations occurring along the easy direction of magnetization and strong exchange interactions between the matrix and defects (e.g.: stacking faults). Lorentz microscopy suggests the domain wall is not physically pinned by the defect, but rather is offset/deflected when it interacts with the defect. The Lorentz and magnetization data suggest that defects cause a bending of the moment away from the c axis inside the grains.

36 MATERIALS SCIENCE↗

Using fiberglass volumes for VPI of superconductive magnetic systems’ insulation

The paper describes the method of manufacturing fiberglass molds for vacuum pressure impregnation (VPI) of high-voltage insulation of superconductive magnetic systems (SMS) with epoxidian hot-setting compounds. The basic advantages of using such vacuum volumes are improved quality of insulation impregnation in complex-shaped areas, and considerable cost-saving of preparing VPI of large-sized components due to dispensing with the stage of fabricating a metal impregnating volume. Such fiberglass vacuum molds were used for VPI of high-voltage insulation samples of an ITER reactor’s PF1 poloidal coil. Electric insulation of these samples has successfully undergone a wide range of high-voltage and mechanical tests at room and cryogenic temperatures. Some results of the tests are also given in this paper.

36 MATERIALS SCIENCE↗

Characterizing the spin orbit torque field-like term in in-plane magnetic system using transverse field

In this work, we present an efficient method for characterizing the spin orbit torque field-like term in an in-plane magnetized system using the harmonic measurement technique. This method does not require a priori knowledge of the planar and anomalous hall resistances and is insensitive to non-uniformity in magnetization, as opposed to the conventional harmonic technique. We theoretically and experimentally demonstrate that the field-like term in the Ta/Co/Pt film stack with in-plane magnetic anisotropy can be obtained by an in-plane transverse field sweep as expected, and magnetization non-uniformity is prevented by the application of fixed magnetic field. The experimental results are in agreement with the analytical calculations.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗

Cryogenic Considerations for Superconducting Magnet System Design for the Material Plasma Exposure eXperiment (MPEX)

The Material Plasma Exposure eXperiment (MPEX) has been proposed as a facility to address plasma material interaction knowledge gaps to qualify and develop materials and technologies that surround plasma environments for future fusion reactors. Utilizing different radio-frequency (rf) heating technologies, MPEX is a linear plasma device that will generate fusion reactor–like plasmas with energies and particle fluxes at the target materials with electron temperatures of 1 to 15 eV, electron densities of 10 20 to 10 21 m -3 , and ion fluxes greater than 10 24 m -2 s -1 . Starting with the MPEX requirements with respect to magnetic fields between 0.1 and 2.5 T and warm bores of either 0.65 m or 1.56 m, conceptual designs for a superconducting magnet system have been developed that utilize multiple NbTi windings distributed across seven cryostats to accommodate rf heating, water cooling, and vacuum systems needed for MPEX. While the cryogenic and magnet technologies relative to the field and space requirements are mature, the integration of these technologies across multiple cryostats presents several technical and logistical challenges. An analysis of the preferred refrigeration approach, modular recondensing liquid helium cryocoolers, was performed. Utilizing a design margin of a factor of two, this approach is feasible within the current design requirements for MPEX with some considerations related to its implementation within the thermal shields and the magnet subsystem geometries.

Duckworth, Robert↗

Improved methods for calculating thermodynamic properties of magnetic systems using Wang-Landau density of states

The Wang-Landau method [F. Wang and D. P. Landau, Phys. Rev. E 64, 056101 (2001)] is an efficient way to calculate the density of states (DOS) for magnetic systems, and the DOS can then be used to rapidly calculate the thermodynamic properties of the system. A technique is presented that uses the DOS for a simple Hamiltonian to create a stratified sample of configurations which are then used calculate a warped DOS for more realistic Hamiltonians. This technique is validated for classical models of bcc Fe with exchange interactions of increasing range, but its real value is using the DOS for a model Hamiltonian calculated on a workstation to select the stratified set of configurations whose energies can then be calculated for a density-functional Hamiltonian. The result is an efficient first-principles calculation of thermodynamic properties such as the specific heat and magnetic susceptibility. Another technique uses the sample configurations to calculate the parameters of a model exchange interaction using a least-squares approach. The thermodynamic properties can be subsequently evaluated using traditional Monte Carlo techniques for the model exchange interaction. Finally, a technique that uses the configurations to train a neural network to estimate the configuration energy is also discussed. This technique could potentially be useful in identifying the configurations most important in calculating the warped DOS. VC2011 American Institute of Physics. [doi:10.1063/1.3565413]

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗