The Japan Proton Accelerator Research Complex (J-PARC) is a world-class accelerator facility for particle and nuclear physics experiments such as the rare kaon decays experiment (KOTO), the T2K ...long-baseline neutrino experiment, and future projects such as COMET. A new stretcher ring (SR) comprising a combined function superconducting magnet is proposed to run all of the facilities at the same time, which can improve beam efficiency and increase operating time. In order to achieve the field quality requirements on the magnet aperture, it is critical to identify an optimum pole shape. Dipole, quadrupole, and sextupole fields are required for the combined function magnet. To find the best design parameters for this analysis, we employed singular value decomposition. The singular value decomposition (SVD) technique resulted in a solution to the desired parameters and a quick process to obtain a 2D pole profile.
Experimental investigation of electron-ion coupling and electron heat capacity of copper in warm and dense states are presented. From time-resolved x-ray absorption spectroscopy, the temporal ...evolution of electron temperature is obtained for non-equilibrium warm dense copper heated by an intense femtosecond laser pulse. Electron heat capacity and electron-ion coupling are inferred from the initial electron temperature and its decrease over 10 ps. Data are compared with various theoretical models.
We use time-resolved x-ray absorption spectroscopy to investigate the unoccupied electronic density of states of warm dense copper that is produced isochorically through the absorption of an ...ultrafast optical pulse. The temperature of the superheated electron-hole plasma, which ranges from 4000 to 10 000 K, was determined by comparing the measured x-ray absorption spectrum with a simulation. The electronic structure of warm dense copper is adequately described with the high temperature electronic density of state calculated by the density functional theory. The dynamics of the electron temperature is consistent with a two-temperature model, while a temperature-dependent electron-phonon coupling parameter is necessary.
Superconducting magnets for high-intensity accelerators and secondary particle sources are required to operate in the high radiation environment by beam collisions and beam losses. Neutron fluence in ...the high-luminosity LHC and the COMET experiment is expected to exceed 10 21 /m 2 . The stabilizer of superconductor is made of pure copper and/or aluminum, and it should degrade by such high radiation. A series of irradiation tests was done to evaluate degradation and recovery by measuring the electrical resistance. The effect of repetitive cycles of irradiation at cryogenic temperature and anneal at room temperature on stabilizer materials of copper and aluminum was measured using reactor neutrons at KUR. Also, pure metals were irradiated at cryogenic temperature by high-energy protons at J-PARC. This paper reviews the results of repetitive irradiation tests on copper and aluminum with reactor neutrons and accelerator protons.
New generation accelerators, such as future circular collider (FCC), require superconducting wires with non-copper J c of 1500 A/mm 2 at 16 T and 4.2 K. Kobe Steel Ltd. developed Nb 3 Sn conductors ...with elemental addition to achieve the target J c for FCC. The effect of zinc addition to the copper matrix on the superconducting properties and mechanical strength of the distributed tin (DT) method processed Nb 3 Sn wire is studied. In the present study, the I c -strain characteristics were evaluated using Walters springs (WASP) at 16 T and 4.2 K to investigate the impact of copper (Cu) and brass (Cu-Zn) matrix on further J c improvement and mechanical robustness.
This study is about a design method for ASSMs (Active Shield Steering Magnets). ASSMs will be applied to a g-2/EDM precise measurements experiment which is under preparation in J-PARC. The experiment ...needs a very homogeneous 3.0 T magnetic field using a superconducting magnet with iron yoke. Muons are injected through spiral orbits in the fringe field and two ASSMs are planned for orbit fine tuning. ASSMs need to generate steering magnetic fields without additional error field. Then, they need active shields, and they are ASSMs. For such ASSMs, a design method has been developed and trial design have been done, using a technique of the MRI GC design method which can well determine 3D current pattern on surfaces.
Nb 3 Sn superconducting wires are under consideration for producing high field accelerator magnets for the proposed Future Circular Collider (FCC) due to their high critical field. R&D studies are ...ongoing worldwide with a target non-Cu critical current density ( J c ) of 1500 A/mm 2 at 4.2 K, 16 T. As an accomplishment of this R&D, one of the conductor manufacturers, JASTEC, has developed Nb 3 Sn wires with non-Cu J c higher than 1100 A/mm 2 at 16 T, 4.2 K by a distributed-tin (DT) method. In high field Nb 3 Sn magnets, degradation of performance has been frequently reported due to the brittleness of Nb 3 Sn and the high electromagnetic force. To realize more robust Nb 3 Sn accelerator magnets, electro-mechanical properties of the conductors should be deeply understood. In this study, the variation of the critical current with mechanical loading is evaluated for a DT Nb 3 Sn wire in two configurations, i.e. under axial strain and under transverse compression.
Magnetic field shimming using low saturation magnetization material was tested to realize spatial magnetic field homogeneity of less than 1 ppm. The magnetic moment per unit mass were measured for ...three candidates, that is, Nickel, magnetic fluid and magnetic putty, and it was verified that those have low magnetic moments suitable for precise shimming below 1 ppm. The magnetic shimming test was performed using MRI magnet for MuSEUM experiment at 1.2 T with iron plates, Ni thin plates and magnetic putty. The magnetic shimming with iron plates was conducted employing the two step shimming scheme, and the homogeneity could be reached to 0.29 ppm peak-to-peak (ppm<inline-formula><tex-math notation="LaTeX">_\text{pp}</tex-math></inline-formula>) after six shimming trials. Then, the precise shimming was carried out with Ni thin plates and magnetic putty, and the homogeneity could be reached to 0.16 ppm peak-to-peak with Nickel and 0.17 ppm<inline-formula><tex-math notation="LaTeX">_\text{pp}</tex-math></inline-formula> with magnetic putty. No deformation of putty in the magnetic field was observed even after two months. The magnetic field monitoring for two months showed that magnetic field strength and homogeneity largely depended on the temperature, and the temperature of the magnet room has to be controlled within <inline-formula><tex-math notation="LaTeX">\pm</tex-math></inline-formula> 0.35 degC under the circumference condition of the shimming test in order to keep the magnetic field change and the homogeneity within <inline-formula><tex-math notation="LaTeX">\pm</tex-math></inline-formula> 0.1 ppm. In addition, it is showed that the refilling of LHe in the MuSEUM magnet system should be performed once per 29 days The practical implementation method for magnetic putty was suggested for the existing magnet system by using plastic spacers with holes.
We report the test results of the first series beam separation dipole, MBXF1, for the HL-LHC project. The magnet has a full length of 7 m and is designed to generate a field integral of 35 T ...<inline-formula><tex-math notation="LaTeX">\cdot</tex-math></inline-formula> m at a nominal operating current (<inline-formula><tex-math notation="LaTeX">I_\text{nominal}</tex-math></inline-formula>) of 12.11 kA. The cold test is performed at the test facility in High Energy Accelerator Research Organization (KEK) using a 9-m deep vertical cryostat. The test consists of two test cycles with one thermal cycle. In each of the test cycles MBXF1 is energized in superfluid helium at 1.9 K and subjected to a series of quench training and magnetic field evaluation. The test shows that the magnet has a good training performance as it reaches <inline-formula><tex-math notation="LaTeX">I_\text{nominal}</tex-math></inline-formula> with two quenches and an ultimate operating current (<inline-formula><tex-math notation="LaTeX">I_\text{ultimate}</tex-math></inline-formula>) of 13.231 kA with seven quenches. Furthermore we observe no quench during the training of the second test cycle, indicating MBXF1 has a good training memory. Magnetic measurements of MBXF1 show that the discrepancy between the measured and computed harmonics at the magnetic center is 3.9 units for normal sextupole and less than 0.5 units for the other allowed-normal multipoles. Finally sextupole integral (<inline-formula><tex-math notation="LaTeX">\bar{b}_{3}</tex-math></inline-formula>) and decapole integral (<inline-formula><tex-math notation="LaTeX">\bar{b}_{5}</tex-math></inline-formula>), which are major systematic field errors in MBXF, respectively are estimated to be 2.0 units and 1.7 units for an actual environmental condition with ferromagnetic materials in the LHC accelerator tunnel.
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