Purpose X-ray free-electron laser facilities require high-repetition and high-energy electron beams, which makes the radiation safety become an important issue due to beam loss. Beam collimation is used to protect the undulator and other devices by removing the beam halo in operation, as well as absorbing the off-axis beam in the case of machine failure. Method In this paper, the beam collimation system in the switchyard of the SHINE is presented. Results and conclusion Tracking with an expanded initial beam distribution, the efficiency of the collimation system is shown, and the detailed collimation performance is simulated to evaluate the available limitation from the acceptance of the undulator. Moreover, the accidental beam loss and wakefield effects are also considered to ensure the reliability of the collimation.

Because of its excellent dose distribution, proton therapy is becoming increasingly popular in the medical application of cancer treatment. A synchrotron-based proton therapy facility was designed and constructed in Shanghai. The synchrotron, beam delivery system, and other technical systems were commissioned and reached their expected performances. After a clinical trial of 47 patients was finished, the proton therapy facility obtained a registration certificate from the National Medical Products Administration. The characteristics of the accelerator and treatment systems are described in this article.

BackgroundSuperconducting undulator (SCU) prototype with small magnet gap of 5 mm, long magnet length of 4 m and high magnet field of 1.58 T was being developed at Shanghai High Repetition rate XFEL and Extreme light facility (SHINE). Compared to any other superconducting undulator, there is no cryocooler being installed on the cryostat in this SCU prototype.PurposeThis study aims at the cooling design for the binary current leads for SCU's normal operating.MethodsBinary current leads composed of normal conductive copper leads and high temperature superconducting current leads (HTS) were adopted for SCU to connect superconducting coils inside the cryostat and outer cables. Low-temperature helium gas was used to transport independent refrigerator system to the cooling tubes inside the prototype, hence the binary current leads were cooled. Thermal conduction components installed on the middle of the thermal shield were employed to transfer heat load of normal conductive copper leads, and heat load of copper leads was optimized by simulation. Auxiliary superconducting rods were designed for connecting cold ends of HTS in the cryostat test.ResultsThe temperature difference between hot ends of HTS and low-temperature helium gas is less than 20 K from the result of cryostat test, all binary current leads is operating normally with full current.ConclusionsIt is practicable to use cooling tubes with low-temperature helium gas to cool binary current leads of the SCU prototype by thermal conduction, which is different from cooling solution for current leads in any other SCU being developed presently.

A high-gradient radiofrequency (RF) gun operated in continuous-wave (CW) mode is required in various accelerating applications. Due to the high RF power loss, a traditional normal-conducting (NC) RF electron gun has difficulty meeting the requirement of generating a high-repetition-rate electron beam. The development of a scheme for a CW NC-RF gun is urgently required. Demonstrated as a photoinjector of a high-repetition-rate free-electron laser (FEL), an electron gun operated in CW mode and the VHF band is designed. An analysis of the reentrant gun cavity is presented in this paper to increase the gradient and decrease the power density and power dissipation. Referring to the analysis results, the design of a 162.5 MHz gun cavity is optimized by a multi-objective evolutionary algorithm to achieve better performance in CW mode. Multipacting and thermal analyses are also deliberated in the design to coordinate with RF and mechanical design. The optimized 162.5 MHz gun cavity can be operated in CW mode to generate a high-repetition-rate beam with voltage up to 1 MV and gradient up to 32.75 MV/m at the cathode.

Forty planar superconducting undulators (SCUs) of 4 m length will be used in Shanghai High Repetition rate XFEL and Extreme Light (SHINE) facility. As the longest SCU in developing of the worldwide, they could generate photon in energy range of 10–25 keV. NbTi/Cu wires with the diameter 0.6 mm and the ratio of Cu to NbTi 0.9 have been chosen as the fundamental element of superconducting coils. Coils temperature must be below 5 K when operating current reaches 400 A. Meanwhile, the magnetic gap need to be less than 5 mm to obtain the peak field of 1.58 T. Therefore, beam chamber installation is infeasible in such a small gap. Two parallel copper foils close to the surface of magnetic poles have been designed to shield beam heat load. Furthermore, four liquid Helium tubes located symmetrically around magnetic structure have been designed to cool the copper foils used as beam channel. There is no cryocooler on the SCU because liquid Helium is provided by the cryogenic plant of SHINE.