Study on the HOMs coupler design of spoke cavity

The superconducting spoke cavity has been proposed to accelerate the proton in the low energy section of high power proton linac for an Accelerator Driven Sub-critical System (ADS).Considering that the High Order Modes (HOMs)in the superconducting cavity have far reaching influence on power dissipation and beam stability,the analysis of HOMs of the spoke cavity is needed.In this paper,we put emphasis on the analysis of HOMs of the spoke cavity and the HOMs coupler design.     

Study on the Lorentz detuning and tuning of β=0.3, 352 MHz spoke cavity

The superconducting spoke cavity has been proposed to accelerate the proton in the low energy section of the high power proton linac for the Accelerator Driven Sub-critical System in China. In this paper, the basic geometric and RF parameters of a β=0.3, 352 MHz spoke cavity are given, and the Lorenz detuning and tuning are presented.     

Study on the RF performance of 2-cell superconducting cavity

The physical design of the 2-cell superconducting cavity is presented. The RF parameters of the cavity and HOMs （high order modes） are reported. In this paper, we put the emphasis on the analysis of the HOMs and interaction between beam and cavity.     

Study of medium beta elliptical cavities for CADS

The China Accelerator-Driven Sub-critical System(CADS) is a high intensity proton facility to dispose of nuclear waste and generate electric power.CADS is based on a 1.5 GeV,10 mA CW superconducting(SC) linac as a driver.The high energy section of the linac is composed of two families of SC elliptical cavities which are designed with geometrical beta 0.63 and 0.82.In this paper,the 650 MHz β=0.63 SC elliptical cavity is studied,including cavity optimization,multipacting,high order modes(HOMs) and generator RF power calculation.     

加速100 mA质子束的低β超导半波长谐振腔内的高阶模（英）

基于超导器的连续波运行的高流强质子/氘束被越来越多的大科学装置所采用。在流强低于10 mA情况下,用于加速低段粒子的超导腔的高阶模影响基本可以忽略,但是对于加速百mA强流的低超导腔,其高阶模损耗情况有待研究。近期北京大学设计并加工了一支=0.09、运行频率162.5 MHz的超导半波长谐振腔,用于研究非相对论低超导半波长谐振腔加速100 mA强流质子束时可能涉及到的关键物理问题。重点研究了这支半波长谐振腔内部高阶模损耗的问题,用时域和频域两种方法分别计算了腔的高阶模损失因子,同时计算了考虑加工误差下腔内发生高阶模共振激发的概率。     

Design of a β=0.45, f=350 MHz Spoke Cavity

Recently intensive studies have been done on superconducting cavities (e.g. spoke cavity, reentrant cavity, and ch cavity), which are used as accelerating structures in the low and medium energy part of high power high intensity proton or ion accelerators. many experiments have shown that spoke cavity is a good candidate for low energy part. it is also promising to be used for the medium β area. so a β=0.45 spoke cavity is being studied at Peking university. in this paper, the structural and electromagnetic design of a β=0.45, f=350mhz spoke cavity is reported in detail. the calculated rf parameters (e.g. Q, r/Q, peak surface fields and dissipated power) indict a potential of good acceleration.     

Study on the RF performance of 2-cell superconducting cavity

The physical design of the 2-cell superconducting cavity is presented.The RF parameters of the cavity and HOMs (high order modes) are reported.In this paper,we put the emphasis on the analysis of the HOMs and interaction between beam and cavity.     

TESLA式高阶模衰减器的改进与设计研究

为了消除超导加速腔中高阶模场对加速粒子的影响, 在DESY的高阶模耦合器结构的基础上本文提出了改进的耦合器. 用HFSS程序针对1.5cell腔设计优化了高阶模耦合器, 得到高阶模耦合器对几种主要模式的吸收. 研究结果表明, 采用新型结构后, 衰减器对主要有害模的衰减由－40dB提高到－15dB, 使原有高阶模衰减器的性能明显提高. 该高阶模衰减器也适用于国产2cell超导腔的使用.     

Error analysis and lattice improvement for the C-ADS Injector- I

The injector Scheme- 1 （or Injector- I ） of the C-ADS linac is a 10 mA 10 MeV proton linac working in C／V mode. It is mainly comprised of a 3.2 MeV room-temperature 4-vane RFQ and twelve superconducting single-spoke cavities housed in a long cryostat. Error analysis including alignment and field errors, and static and dynamic ones for the illjector are presented. Based on detailed numerical simulations, an orbit correction scheme has been designed, which shows that with correction the rms residual orbit errors can be controlled within 0.3 mm and a beam loss rate of 1.7× 10-6 is obtained. To reduce the beam loss rate further, an improved lattice design for the superconducting spoke cavity section has been studied.     

非均匀束团在储存环高频腔中产生的高次模功率

通过分析束流频谱与高频腔高次模的相互作用,提出了计算单束流和双束流储存环中非均匀束团产生的高频腔高次模功率的方法,推导出了这两种情况下的一般通用公式,并对所得到的解析结果进行了比较和讨论.     

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 (BEPCⅡ), 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.     

Error analysis and lattice improvement for the C-ADS Injector-Ⅰ

The injector Scheme-Ⅰ (or Injector-Ⅰ) of the C-ADS linac is a 10 mA 10 MeV proton linac working in CW mode. It is mainly comprised of a 3.2 MeV room-temperature 4-vane RFQ and twelve superconducting single-spoke cavities housed in a long cryostat. Error analysis including alignment and field errors, and static and dynamic ones for the injector are presented. Based on detailed numerical simulations, an orbit correction scheme has been designed, which shows that with correction the rms residual orbit errors can be controlled within 0.3 mm and a beam loss rate of 1.7× 10^-6 is obtained. To reduce the beam loss rate further, an improved lattice design for the superconducting spoke cavity section has been studied.     

Tuner control system of Spoke012 SRF cavity for C-ADS injector I

A new tuner control system for spoke superconducting radio frequency(SRF) cavities has been developed and applied to cryomodule I of the C-ADS injector I at the Institute of High Energy Physics, Chinese Academy of Sciences. We have successfully implemented the tuner controller based on Programmable Logic Controller(PLC)for the first time and achieved a cavity tuning phase error of ±0.7?(about ±4 Hz peak to peak) in the presence of electromechanical coupled resonance. This paper presents preliminary experimental results based on the PLC tuner controller under proton beam commissioning.     

Design study on very low Beta spoke cavity for China-ADS

Very low Beta superconducting spoke cavity is one of the key challenges for the China-ADS project. In this paper, a new structure of 3βλ/2 spoke cavity is first studied in detail. Its RF and mechanical properties are simulated using CST-MWS and ANSYS, and compared with the traditional βλ/2 spoke structure.     

Study and design of RF coupler for Chinese ADS HWR superconducting cavity

An RF power coupler is a key component of the superconducting accelerating system in Chinese ADS proton linac injector I, which is used to transmit 15 kW RF power from the power source to the superconducting HWR cavity. According to the requirement of working frequency, power level, transmission capability and cooling condition, the physics design of coupler has been finished, which includes RF structure optimization, thermal simulation, thermal stress analysis and so on. Based on this design, the prototype of HWR coupler has been fabricated, and it has successfully passed the high power test.     

HOMs simulation and measurement results of IHEP02 cavity

In accelerator RF cavities, there exists not only the fundamental mode which is used to accelerate the beam, but also higher order modes(HOMs). The higher order modes excited by the beam can seriously affect beam quality, especially for the higher R/Q modes. 1.3 GHz low-loss 9-cell superconducting cavity as a candidate for ILC high gradient cavity, the properties of higher order mode has not been studied carefully. IHEP based on existing low loss cavity, designed and developed a large grain size 1.3 GHz low-loss 9-cell superconducting cavity(IHEP02cavity). The higher order mode coupler of IHEP02 used TESLA coupler's design. As a result of the limitation of the mechanical design, the distance between higher order mode coupler and end cell is larger than TESLA cavity.This paper reports on measured results of higher order modes in the IHEP02 1.3 GHz low-loss 9-cell superconducting cavity. Using different methods, Q e of the dangerous modes passbands have been obtained. The results are compared with TESLA cavity results. R/Q of the first three passbands have also been obtained by simulation and compared with the results of the TESLA cavity.     

2-cell超导腔的高阶模分析

 阐述了2-cell Telsa腔的设计。用3维程序HFSS分析了其高阶模的特点，给出了高阶模的主要参数频率、品质因数、分路阻抗以及模式的电场分布，并且π模的电场分布与Superfish的模拟结果相比较，两者是一致的。最后，简要分析了各高阶模对电子加速的影响，分析表明高阶模降低了电子加速效率和束流的稳定性。     

Design study on very low Beta spoke cavityfor China-ADS

Very low Beta superconducting spoke cavity is one of the key challenges for the China-ADS project. In this paper, a new structure of 3βλ/2 spoke cavity is first studied in detail. Its RF and mechanical properties are simulated using CST-MWS and ANSYS, and compared with the traditional βλ/2 spoke structure.