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Shanghai Coherent Light Facility (SCLF), a superconducting accelerated structure-baesd FEL device, is now under development at Shanghai Institute of Applied Physics, Chinese Academy of Sciences. We investigate effects of cryogenic losses caused by trapped longitudinal high order modes (HOM). Results of calculations are presented for losses caused by HOMs excitation in the acceleration RF system of the continues-wave (CW) linac of SCLF., Proceedings of the 9th Int. Particle Accelerator Conf., IPAC2018, Vancouver, BC, Canada

A RF trip diagnostic system is essential to find out the trip source when a trip happened. In this paper, a fast RF trip diagnostic system, in storage ring RF system of SSRF, is reported. This system includes a synchronous acquisition recorder to sampling the trip data and a trip server to analysis the data. The recorder has more than 100 channels and maximum sampling rate of each channel is up to 60 MSPS. High precision I/Q cards are designed to detect RF signals. Trip server has been developed to process the trip data., Proceedings of the 7th Int. Particle Accelerator Conf., IPAC2016, Busan, Korea

This paper illustrates the design and simulation of a unique 500 MHz single-cell superconducting radio frequency cavity with a fluted beam pipe and a coaxial-type fundamental power coupler. The simulation results show that the cavity has a high r/Q value, a low peak surface field and a large beam aperture, so it can be a candidate cavity for high current accelerators. With the help of a fluted beam tube, almost all the higher order modes can propagate out of the cavity, especially the first two dipole modes, TE111 and TM110, and the first higher monopole mode, TM011. The external quality factor of the coaxial fundamental power coupler is optimized to 1.2x10(5), which will be useful when it is applied in the light source storage ring.

A third harmonic superconducting niobium cavity has been proposed for installation in the Shanghai Synchrotron Radiation Facility (SSRF) storage ring to improve the Touschek lifetime. In order to investigate the feasibility of the superconducting cavity fabrication indigenously and the possibility to master the fabrication techniques, cavities were fabricated from copper and niobium sheets by deep drawing and electron-beam welding, and a series of measurements, such as resonant frequency, shape dimensions and wall thickness, were carried out during this process. After analysis of various problems existing in the fabrication process, technique improvements were proposed, and finally the precise shape as designed and resonant frequency within 1.2 MHz were achieved for the new completed cavities. In addition, full annealing was finally proved to be a good cure for niobium sheets' tearing up during deep drawing. By fabricating niobium cavities successfully, some problems to the next step were cleared. This paper introduces the process of cavity fabrication and its technique improvements towards forming, and the initial vertical test result of niobium cavity is also presented.

This paper explores the formation process of surface pyramid morphologies and etching characteristics during the texturing process of silicon heterojunction (SHJ) solar cells. Our research discovered that pyramid size followed a linear correlation with etch amount at the transition point of planes {100} to {111} as the etch rate reached the transition point. Several techniques were developed to control pyramid size by monitoring and adjusting the etching amount at the transition point. Using this approach, the average pyramid size was successfully controlled from 0.5 µm to 12 µm. We concluded that for pyramids smaller than 1 µm or greater than 12 µm, the light reflectance, minority carrier lifetime (MCLT), and performance of SHJ solar cells were adversely affected. In conclusion, a desirable range of pyramid sizes was empirically determined by our investigation.

The digital low level radio frequency (DLLRF) system and the beam trip diagnostic system in the storage ring of Shanghai Synchrotron Radiation Facility (SSRF) have been operational for more than one year. The DLLRF has successfully maintained the amplitude and phase stability of the cavity field in the superconducting cavity even when the beam current in the storage ring reached 300mA at 3.5GeV, and the beam trip diagnostic system has been realized and is helpful for improving the reliability of the RF system., Proceedings of the 1st International Particle Accelerator Conference, IPAC2010, Kyoto, Japan

The superconducting RF system has been operated successfully in the storage ring of SSRF since July, 2008. The superconducting RF modules integrated with 310 kW transmitters and digital low level radio frequency (LLRF) control are adopted to provide about 4.5 MV cavity voltages to 3.5GeV electron beam. The operation status of SRF system is mainly reported here, the problems we met are analyzed, and the operation with normal conducting cavity systems is introduced briefly. The challenge for us is to improve the system reliability and machine performance., Proceedings of the 1st International Particle Accelerator Conference, IPAC2010, Kyoto, Japan

To investigate the higher order mode(HOM) damping in the higher harmonic cavity for Shanghai Synchrotron Radiation Facility(SSRF) when using HOM absorbers, simulations have been done for changing the position and the length as well as the thickness of ferrite of HOM damper. The best values under which the Q value of HOMs can be greatly lowered and the impedance of harmonic cavity will be trapped in the impedance threshold have been found., Proceedings of the 1st International Particle Accelerator Conference, IPAC2010, Kyoto, Japan