Zq Li

A tuning system for BEPC II

The tuning system plays a very important role when a superconducting cavity is in operation. It cooperates with other control loops to adjust the cavity frequency with high precision, reduce the reflection power, guarantee the stability of beam, and ensure the safety of the superconducting cavity. This paper focuses mainly on the tuning system working principle, the working state and problems that Beijing Electron Positron Collider (BEPC II) has encountered during operation.

Design and test of frequency tuner for a CAEP high power THz free-electron laser

Peking University is developing a 1.3 GHz superconducting accelerating section highpower THz free-electron laser for the China Academy of Engineering Physics (CAEP). A compact fast/slow tuner has been developed by the Institute of High Energy Physics (IHEP) for the accelerating section to control Lorentz detuning, compensate for beam loading effect, microphonics and liquid helium pressure fluctuations. The tuner design, warm test and cold test of the first prototype are presented, which has a guiding significance for the manufacture of the formal tuner and cryomodule assembly.Peking University is developing a 1.3 GHz superconducting accelerating section highpower THz freeelectron laser for the China Academy of Engineering Physics(CAEP). A compact fast/slow tuner has been developed by the Institute of High Energy Physics(IHEP) for the accelerating section to control Lorentz detuning, compensate for beam loading effect, microphonics and liquid helium pressure fluctuations. The tuner design, warm test and cold test of the first prototype are presented, which has a guiding significance for the manufacture of the formal tuner and cryomodule assembly.

Some experiences with BEPCII SRF system operation

The Superconducting Radio Frequency (SRF) system of the upgrade project of the Beijing Electron Positron Collider (BEPCII) has been in operation for almost 8 years. During operation, many problems have been encountered, such as excessive heating of the power couplers, frequent beam trips during high intensity colliding, false arc interlock trigger and so on. Among them, some has been solved successfully, some have been alleviated. This paper will describe some experiences with BEPCII SRF system operation, including the symptoms, causes and solutions of problems.

Design of a 325 MHz half wave resonator prototype at IHEP

A 325 MHz β = 0.14 superconducting half-wave resonator prototype has been developed at the Institute of High Energy Physics, Beijing, which can be applied in the low energy section of continuous wave high current proton linear accelerators. The electromagnetic design, multipacting simulation, mechanical optimization and fabrication are introduced in detail. Test results at room temperature and 4.2 K, and a comparison between measured and simulated results, are analyzed in this paper.

Design of a 325 MHz SC Spoke040 cavity at IHEP

A spoke cavity is a TEM-class superconducting resonator with particular advantages: compact structure and high shunt impedance. The 325 MHz beta=0.40 (beta=v/c, v is the velocity of particle and c is the velocity of light) single spoke cavity (Spoke040) is adopted for the Chinese ADS (Accelerator Driven Sub-critical System) project. The physics and mechanical design has been accomplished, and the fabrication of a prototype is currently in progress. In this paper, the optimization processes for the main radio frequency (RF) and mechanical parameters are analyzed in detail. Two kinds of cavity end-walls (flat and convex) are compared. The convex end-wall is preferred in order to improve mechanical performance of the cavity. Two prototypes of the Spoke040 cavity are in the machining stage, and should be finished in early 2014. Vertical testing is also under preparation.

Horizontal test for BEPC 500 MHz spare cavity

The horizontal test for the BEPC II 500 MHz spare cavity has been completed at IHEP. The maximum voltage of the cavity reached 2.17 MV, while Q(0) was 5.78x10(8). The process and results of the high power horizontal test are presented and discussed in this paper.