Fu-Yuan Lin

Design and construction performance of a compact cryogen-free superconducting wavelength shifter

A compact cryogen-free superconducting wavelength shifter with a warm bore for electron beam has been constructed for generating synchrotron radiation hard X-rays. This magnet consists of three pairs of racetrack NbTi superconducting coils that can produce a maximum magnetic field of 6.0 Tesla at the central pole. The superconducting coils, the aluminum supporting block, and the return iron yokes are cooled to 4 K, and the thermal shielding and HTS current leads to 60 K, by using a 1.5 W Gifford-McMahon type cryocooler. The technical issues on the magnet design and the construction process are presented. Several different measurement systems are used to characterize the magnetic field performance.

Design of a superconducting multipole wiggler for synchrotron radiation

A 32-pole superconducting magnet with a 12 /spl times/ 80 mm/sup 2/ cold bore aperture was designed to serve as a multipole wiggler in the Taiwan synchrotron light source. The magnet consists of 32 pairs of racetrack NbTi superconducting coils with a periodic length of 60 mm, and can produce a maximum magnetic field of 3.2 Tesla at a pole gap of 18 mm. The superconducting coils, the aluminum-supporting block, and the return iron yokes are cooled to 4.4 K in LHe bath. The temperature of cold bore beam duct will be at 70 K using liquid nitrogen. Technical issues concerning the design of the magnet and its construction are discussed. A prototype magnet with five poles was also constructed to characterize the magnet design by means of various methods of magnetic field measurement.

Mini-pole Superconducting Undulator for X-Ray Synchrotron Light Source

A mini-pole planar vertically-wound racetrack coil undulator was studied to determine its potential for use as a hard X-ray source in a 3 GeV storage ring. A field strength of 1.4 T can be obtained for a superconducting undulator with a periodic length of 1.5 cm and a fixed magnetic gap of 5.6 mm. The magnetic circuit was optimized and a current density of 1090 A/mm2, at 80% of the critical current, meets the field strength requirement. A prototype with 40 poles was constructed to verify the design of the magnet and the performance of NbTi superconductor. Additionally, the magnetic field shimming method was developed for spectrum shimming. This study discusses the design of the magnetic circuit and the structure of the magnetic array, the field shimming technique, and the test results of the prototype magnet

Design, Fabrication, and Performance Tests of a HTS Superconducting Dipole Magnet

The use of HTS (high-temperature superconductor) coils for accelerator magnets decreases significantly the power consumption and operating cost. Therefore, a preliminary study was launched and a prototype of a dipole magnet with HTS coils has been designed and fabricated by NSRRC and HTS-110 Ltd. Although 2G YBCO wire is expected to be used in future HTS applications, it currently requires more joints to form the completed coils. For this reason, we chose 1G BSCCO wires for the HTS coils. Two single-stage pulse-tube refrigerators with one compressor serve to cool the HTS coils of the magnet, but we shall use LN2 to replace the pulse-tube refrigerators in the future. The HTS magnet is designed to provide a stable field of strength 1.19 T with field homogeneity better than 1.5 × 10-4 in the range of the transverse -20 ≤ x ≤ 20 mm direction when it operates at 50 K with a current of 110 A. To compare with the field features of copper-coil dipole magnets, a Hall-probe measurement system was used to measure the detailed magnetic field and B-I characteristics of the HTS dipole magnet at NSRRC.

Field Correction of an Elliptically Polarized Undulator

The correction of the magnetic field of an elliptically polarized undulator (EPU) decreases the phase errors, the RMS trajectory and multipole magnetic components. The conventional method to correct the field involves tedious work with much trial and error. Based on field-shimming procedures and a field-shimming simulator proposed in National Synchrotron Radiation Research Center, the duration of field correction of EPU46 becomes decreased. The first field integral and the kicker value at each magnet pole determine the amount of adjustment of vertical and horizontal positions of the magnet. The final result of correcting a single pair of a magnet array shows a phase error less than 5 and a variation of the RMS trajectory less than 5 , in both circular and linear polarization modes for single pair of magnet array. Here we describe a standard operating procedure of EPU field correction that is becoming established, which will be beneficial for a future mass-production stage and for training purposes.

Design and Improvement of a Mini-Pole Superconducting Undulator at NSRRC

The wire windings and magnetic performance of the mini-pole superconducting undulator (SCU) at the National Synchrotron Radiation Research Center (NSRRC) are being improved. NbTi superconducting (SC) wire with a rectangular cross section 0.51 mm 0.77 mm was wound on a racetrack iron pole. The designed field strength was 1.4 T at excitation current 510 A. The bath LHe-cryostat cools the SC wire directly and uniformly using LHe. A stainless-steel (SS) beam duct (thickness 0.3 mm) is designed to separate the ultra-high vacuum (UHV) from the storage ring and the LHe. The SS beam duct is glued to the dummy arrays with resin epoxy. The dummy arrays provide a strong support for the beam duct, providing against deformity from a pressure differential. A vacuum test was performed with a short version of a beam duct (length 400 mm) at low temperature. This paper describes the construction of the magnet, the measurement of the field and the testing of the SS beam duct.

Analysis of Heat Load in a Superconducting Wiggler With a Semi-Cold UHV Beam Duct

A superconducting wiggler with a magnetic period of 6.0 cm (SW6) and a peak field of 3.2 T has been designed and fabricated in the National Synchrotron Radiation Research Center (NSRRC). The beam duct separates the electron beam from the cryogenic system of the magnet. The heat load on the beam duct should be low to stabilize the operation of the superconducting magnets. However, outgassing caused by synchrotron radiation at an electron energy of 1.5 GeV and a current of 200 mA must be reduced. Accordingly, operating the system at a higher temperature can minimize the adsorption of molecules on the beam duct. Therefore, the beam duct system and its connection by finite element analysis are designed to optimize the operating temperature of the beam duct at between 100 and 120 K. Performance of the beam duct is established to comply with specifications during the operation of magnet

Preliminary Test Results Concerning the “Within-Achromat”Superconducting Wiggler at NSRRC

A 0.96 m with 16 poles superconducting wiggler is fabricated in-house at NSRRC. The wiggler produced a magnetic field of 3.1 T for a 61 mm period with a pole gap of 19 mm. Three 5-pole prototype magnets using various pole materials from low carbon steel, vanadium permendure steel and holmium are tested and measured to verify the magnetic field performance in the testing dewar. This work describes the design and construction of a magnet and cryostat system. Furthermore, this work presents the results of magnet tests and the field performance of the compact superconducting wiggler

Magnetic-Field Shimming and Field Measurement Issue of the 130-Pole Superconducting Undulator

A 130-pole superconducting undulator with NbTi wires was wound and tested at National Synchrotron Radiation Research Center (NSRRC). The magnetic field was measured with a cryogenic mini-Hall sensor in a vertical dewar. The difference of total length between the nominal design and that measured experimentally with the Hall probe is approximately 1.2 mm; this discrepancy arises from the thermal contribution during the field measurement in the test dewar. The reliability of the measurement system is confirmed, and is discussed in terms of the field-mapping spectrum. The measurement of the field strength revealed a non-uniform distribution of the field in the 1 m long arrays. An iron pole piece was used to shim the on-axis field strength of the undulators. We discuss the thermal effect of the measurement system, a useful shimming method and its results for the superconducting undulator.

Design, Construction, and Performance Testing of a 6.5 T Superconducting Wavelength Shifter

A compact three-pole superconducting magnet with an aluminum warm beam duct was designed and fabricated as an X-ray source in a 1.5 GeV Taiwan Light Source (TLS) or the 3 GeV Taiwan Photon Source (TPS). Three pairs of racetrack NbTi superconducting coils were connected to one main power supply to create a central field of over 6.5 T. Two low current trim power supplies were connected in parallel to the two side pairs of the coil to eliminate the first and second field integrals. The wavelength shifter magnet was cooled in a pool boiling helium bath. Helium boils off at 1.3 L/hr. The vapor-cooled current lead is used to pass the 350 A excitation current. The magnetic field strength was measured at room temperature using a Hall probe and a stretched wire system. The magnet was tested successfully to 308 A, at which the central field exceeded 6.5 T, and the peak field on coil was 8.2 T. The design and construction of the magnet and the cryostat, the quenching protection, and field measurement results will be presented and discussed.