Zhilong Hou

20-T Dipole Magnet With Common-Coil Configuration: Main Characteristics and Challenges

The Institute of High Energy Physics (Beijing, China) is pursuing R&D of high-field accelerator magnet technology for the recently proposed CEPC-SPPC project, which will need thousands of 20-T level accelerator magnets in 20 years. A long-term plan has been made aiming to realize the 20-T magnets in 15 years. The conceptual design study has been ongoing from 2014 based on the current Jc level of superconductors. As both Nb3Sn and high-temperature superconductor superconducting materials are strain sensitive, the common-coil configuration has been chosen as the first option for the design study of the 20-T dipoles, to simplify the coil structure, raise the bending radius, and lower the strain level in superconducting coils. The magnetic analysis, mechanical analysis, and preliminary design study of the straight section and the coil ends have been completed for a 20-T common-coil dipole magnet. The main characteristics and challenges of this design concept will be presented in this paper.

Magnetic Design Study of the High-Field Common-Coil Dipole Magnet for High-Energy Accelerators

The Institute of High Energy Physics (IHEP, Beijing, China) is proposing a two-stage particle collider: CEPC-SppC. The first stage is a circular electron-positron collider (CEPC), expected to carry out high-precision studies on Higgs bosons. Upon completion of the CEPC experiment, it will be upgraded to a super proton-proton collider (SppC), aiming at the discovery of physics beyond the standard model. The circumference of the accelerator for CEPC and SppC will be 50 ~ 70 km. The required dipole held strength is 20 T for SppC. As the start of a long-term R&D plan for high-held accelerator magnet technology at IHEP, a 15-T short sample held Nb3Sn dipole is planned to be developed within the next five years. The common-coil configuration is adopted to provide space for two apertures with a maximum diameter of 60 mm. The 10-4 level held uniformity will be reached at a reference radius of 15 mm. Magnetic analytical modeling and FEM cross section study of this high-held common-coil dipole has been done and will be presented here. A preliminary cross section study of the 20-T common-coil dipole will also be introduced; the design is based on the current Jc level of Nb3Sn and HTS superconductors.

Magnetic Field Mapping in the BESIII Solenoid

The Beijing Spectrometer III (BESIII) superconducting solenoid magnet, which is running in the Beijing Electron Positron Collider II (BEPC-II), is an important part of BESIII and provides a 1 Tesla field in the main drift chamber. A 3-D mapping device with three 3-D probes was fabricated to measure the field components of , and . The mapping of the magnetic field of the BESIII superconducting solenoid magnet is presented, with the accelerator interaction region magnets located inside the BESIII solenoid excited to different current values. A set of polynomials, and a few trigonometric-Bessel terms are used to fit the data. The measurements and the functional model agree to 5 Gauss within the main drift chamber tracking volume at nominal field values.

Numerical Study on Quench Process in Multi-Sectioned Adiabatic Superconducting Electromagnetic Iron Separator

A two-dimensional quench simulation model was developed for the Superconducting Electromagnetic Iron Separator (SEIS) system, which is designed to separate small pieces of ferromagnetic materials, such as detonators, from coal to achieve high purity and good yield. The SEIS coil adopted passive quench protection system with four-sectioned arrangement, each shunted with four diodes. The aluminum slices, with 99.99% purity and 0.5 mm × 12 mm cross section dimension, working as quench propagator, were clothed on the inner and the outer surfaces of the coil. The minimum quench energy, the temporal variations of current, voltage and hot spot temperature rise of the coil were analysed. Furthermore, the coil stress during winding, cool-down, charging and quench process was also included in this paper. The simulation results demonstrated that the existing protection system could guarantee the SEIS magnet experience no fatal damage during quench.

2-D Mechanical Design Study of a 20-T Two-in-One Common-Coil Dipole Magnet for High-Energy Accelerators

A two-stage particle collider, i.e., CEPC-SppC, is proposed by the Institute of High Energy Physics (Beijing, China). The circular electron-positron collider (CEPC) will be upgraded to a super proton-proton collider (SppC) after the first-stage experiment. According to the requirement of SppC, the field strength of the main dipoles is 20 T, and 10-4 level field uniformity should be reached within two thirds of the aperture. The outer diameter is restricted to be 900 mm. The magnetic design study of a 20-T two-in-one common-coil dipole magnet has been done and previously presented. This paper mainly focuses on the corresponding mechanical design study by establishing a two-dimensional finite-element model with a shell-based structure. The water-pressurized bladder is adopted to apply the preload on coils with the pressure of 80 MPa. The peak coil stress is minimized to reduce the critical current degradation of superconductors. An appropriate aluminum shell thickness is selected to overcome the significant Lorentz force under the restriction of the main dipoles outer diameter.

Development of an Eddy-Current Separation Equipment With High Gradient Superconducting Magnet

A high gradient magnetic separator (HGMS) used for recovery of waste electric and electronic equipment has been designed and fabricated in the Institute of High Energy Physics of China. It has a warm bore of 200 mm diameter and consists of two superconducting solenoid coils made of epoxy-impregnated NbTi/Cu superconductors. The designed center field is 5 T, and the field gradient more than 36 T/m. The magnet suffered several trainings to reach its designed current of 153 A and stably operated during many charging and discharging. In this paper, the detailed development of this magnet is presented.

Test of BESIII Detector Magnet

The Beijing Spectrometer III (BESIII) detector magnet running in Beijing electron positron collider reached its nominal current successfully in 2008. The 3.39 m diameter, 3.91 m long superconducting solenoid magnet (SSM) provides a 1 Tesla central magnetic field. It was inner wound with aluminum stabilized NbTi/Cu cable and conduction - cooled with forced flow of two phase helium circulating in a tracing tube. A thermal shield was conduction - cooled with liquid nitrogen in the cryostat. This paper reports the experience of the test of the BESIII detector magnet.

Tests of 3 T Superconducting Electromagnetic Iron Separator

A 3 T central field Superconducting Electromagnetic Iron Separator (SEIS) has been designed, fabricated and tested at Institute of High Energy Physics (IHEP) of China. The SEIS system is deliberately designed to separate small pieces of hazardous ferromagnetic materials, such as detonators, from coal to achieve high purity and good yield. The SEIS system mainly consists of a NbTi superconducting magnet, a LHe recondensation type cryostat with two GM cryocoolers (31 W/40 K, 1 W/4.2 K), a pair of binary current leads (CL). The 1 ton cold mass was located in the cryostat of the system with 630 mm room temperature bore. The system is powered with a 250 A/50 V power supply, and has charging time and discharging time of 15 minutes and 20 minutes, respectively. It took 10 days for SEIS magnet to cool down from 300 K to 4.2 K and 6 days to accumulate LHe at designed level 360 mm. The SEIS magnet suffered no quench to reach its designed current, and operated stably during many experiments afterwards. The experiment research of the SEIS system is detailedly presented in this paper.

The BESIII detector magnet

Publisher Summary BESIII (Beijing Spectrometer III) is a detector designed to run in the autumn 2007 at a 1 ╳ 10 33 cm -2 s -1 luminosity @1.89 GeV at BEPCII (Beijing Electron–Positron Collider II) at IHEP Beijing. It has a 1 T superconducting solenoid magnet with the inner winding diameter of 2962 mm, winding length of 3532 mm, and a 600 tonne flux return yoke. The indirectly cooled, pure aluminum stabilized single layer coil is internally wounded with a 4 kA superconductor. The magnet design is described. The NbTi/Cu superconductor has been delivered and the critical current test of a short sample of the superconductor has been performed. An inner winding machine is under construction.

Design of Cylindrical Transverse Gradient Coil for 1.5 T MRI System

Magnetic resonance imaging (MRI) requires the gradient coils to produce magnetic field gradients, to encode three-dimensional information. In this work, a parametric method to the design of cylindrical transverse gradient coils for high-resolution magnetic resonance imaging (MRI) is proposed. The cylindrical transverse gradient coil was separated to several turns of curves, each turn is considered as a curve butted by two quasi-elliptic arcs. The parameterized curve is optimized with the simulated annealing algorithm. A cylindrical transverse gradient coil with high level of linearity is designed for 1.5 T MRI system. The cylindrical transverse gradient coil can build a high-quality transverse gradient magnetic field in a large spherical zone, concentric with the main magnet of the MRI system.