Abstract
The development of a new hard x-ray beamline I-TOMCAT equipped with a 1 m long short-period bulk high-temperature superconductor undulator (BHTSU) has been scheduled for the upgrade of the Swiss Light Source at the Paul Scherrer Institute. The very hard x-ray source generated by the BHTSU will increase the brilliance at the beamline by over one order of magnitude in comparison to other state-of-the-art undulator technologies and allow experiments to be carried out with photon energies in excess of 60 keV. One of the key challenges for designing a 1 m long (100 periods) BHTSU is the large-scale simulation of the magnetization currents inside 200 staggered-array bulk superconductors. A feasible approach to simplify the electromagnetic model is to retain five periods from both ends of the 1 m long BHTSU, reducing the number of degrees of freedom to the scale of millions. In this paper, the theory of the recently-proposed 2D A -V formulation-based backward computation method is extended to calculate the critical state magnetization currents in the ten-period staggered-array BHTSU in 3D. The simulation results of the magnetization currents and the associated undulator field along the electron beam axis are compared with the well-known 3D H -formulation and the highly efficient 3D H -ϕ formulation method, all methods showing excellent agreement with each other as well as with experimental results. The mixed H -ϕ formulation avoids computing the eddy currents in the air subdomain and is significantly faster than the full H -formulation method, but is slower in comparison to the A -V formulation-based backward computation. Finally, the fastest and the most efficient A -V formulation, implemented in ANSYS 2020R1 Academic, is adopted to optimize the integrals of the undulator field along the electron beam axis by optimizing the sizes of the end bulks.
Highlights
In 2004, Tanaka et al first proposed the concept of the bulk high-temperature superconductor undulator (BHTSU) in which a dipole field was utilized to magnetize in-situ a series of rectangular high-temperature superconductors (HTS) [1]
In 2008, Kinjo et al proposed the concept of the staggered-array BHTSU by using a superconducting solenoid to magnetize a series of staggered-array superconducting half-moon-shaped disks [2], and in 2013, they demonstrated for the first time an undulator field B0 of 0.85 T in a 10 mm period, 4 mm gap BHTSU prototype subjected to an external field change ∆B of 4 T [3]
In late 2020, the Paul Scherrer Institute scheduled the development of a 1 m long BHTSU with a 10 mm period and 4 mm gap for installation in the new I-TOMCAT microscopy tomography beamline planned for the upgraded Swiss Light Source [5]
Summary
In 2004, Tanaka et al first proposed the concept of the bulk high-temperature superconductor undulator (BHTSU) in which a dipole field was utilized to magnetize in-situ a series of rectangular high-temperature superconductors (HTS) [1]. In 1995, Brandt proposed the integral method based on an equation of motion for the current density and an E-J power law for computing the critical state in bulk superconductors with rectangular crosssection [31] This integral method was extended by Brandt in 1996 to compute more realistic cases and by Bouzo et al to solve 3D magnetization problems [32, 33]. In 1976, Witzeling proposed the circuit method to compute the screening currents inside a superconducting cylinder, assuming the superconductors as an array of parallel wires and creating a relation between different current loops based on the law of induction [34] This was the very first numerical method which solved the critical state currents in superconducting bulks. We use the fastest and most efficient A-V formulationbased backward computation method to optimize the bulk sizes to minimize the integrals of the undulator field along the beam-axis
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
