Pan Weimin

FPGA-based amplitude and phase detection in DLLRF

The new generation particle accelerator requires a highly stable radio frequency (RF) system. The stability of the RF system is realized by the Low Level RF (LLRF) subsystem which controls the amplitude and phase of the RF signal. The detection of the RF signals amplitude and phase is fundamental to LLRF controls. High-speed ADC (Analog to Digital Converter), DAC (Digital to Analog Converter) and FPGA (Field Programmable Gate Array) play very important roles in digital LLRF control systems. This paper describes the implementation of real-time amplitude and phase detection based of the FPGA with an analysis of the main factors that affect the detection accuracy such as jitter, algorithms defects and non-linearity of devices, which is helpful for future work on high precision detection and control.

Low beta spoke cavity multipacting analysis

The simulation and analysis for electron multipacting phenomenon in a low β spoke superconducting cavity in ADS proton accelerator are proposed. Using both CST and Track3P codes, the electron multipacting calculation for β=0.12 spoke superconducting cavity is implemented. The methods of multipacting...The simulation and analysis for electron multipacting phenomenon in low {\beta} spoke superconducting cavity in ADS proton accelerator are proposed. Using both CST and Track3P codes, the electron multipacting calculation for {\beta} = 0.12 spoke superconducting cavity is implemented. The methods of multipacting calculation on both codes are studied and described. With the comparison between the calculation results and the cavity vertical test results, the accuracy and reliability of different code on calculating multipacting are analyzed. Multipacting calculation can help to understand the result of vertical test and also can help to do the optimation in cavity design.

Calculation of the external quality factor of the high power input coupler for the BEPCII superconducting cavity

It is very important to predict the coupling between the cavity and the high power input source in the coupler design. In this paper, a time domain method is used to calculate the external quality factor Q(ext) for the BEPC II superconducting cavity. A comparison between simulation results and experimental results is presented. The results of simulation and measurement of Q(ext) have a good agreement within an error of 10%. The geometry parameters related with Q(ext) are also studied.

Coupler conditioning and high power testing of ADS Spoke cavity

Power couplers, used in China-ADS proton linac injector I, are required to transfer 6 kW RF power to the superconducting Spoke cavities. At present, first the two couplers of a coaxial design have been fabricated, which accomplished a high power test at IHEP. The test results indicated that couplers of this design are qualified to deliver 10 kW RF power in continuous travelling wave mode. This paper describes the couplers room temperature test procedures and results and discusses the original high power test, which was terminated due to serious out-gassing and after some modifications. In the final test, the couplers smoothly exceeded the design power level.

Development of a 500 MHz high power RF test stand

A flexible high power RF test stand has been designed and constructed at IHEP to test a variety of 500 MHz superconducting RF components for the upgrade project of the Beijing Electron Positron Collider (BEPC II), such as the input coupler, the higher order modes (HOMs) absorber and so on. A high power input coupler has been conditioned and tested with the RF power up to 250 kW in continuous wave (CW), traveling wave (TW) mode and 150 kW CW in standing wave (SW) mode. A prototype of the HOMs absorber has been tested to absorb power of 4.4 kW. An introduction of the test stand design, construction and high power tests is presented in this paper.

HOM study and parameter calculation of the TESLA cavity model

The Superconducting Proton Linac (SPL) is the project for a superconducting, high current H-accelerator at CERN. To find dangerous higher order modes (HOMs) in the SPL superconducting cavities, simulation and analysis for the cavity model using simulation tools are necessary. The. existing TESLA 9-cell cavity geometry data have been used for the initial construction of the models in HFSS. Monopole, dipole and quadrupole modes have been obtained by applying different symmetry boundaries on various cavity models. In calculation, scripting language in HFSS was used to create scripts to automatically calculate the parameters of modes in these cavity models (these scripts are also available in other cavities with different cell numbers and geometric structures). The results calculated automatically are then compared with the values given in the TESLA paper. The optimized cavity model with the minimum error will be taken as the base for further simulation of the SPL cavities.