基于滑模极值搜索的SSC-LINAC RFQ调谐系统设计与测试

将滑模极值搜索算法引入基于腔体反射信号的SSC-LINAC射频四极场加速器(Radio Frequency Quadrupole, RFQ)腔体频率稳定系统设计中,结合Lyapunov稳定性理论和SSC-LINAC RFQ高频系统的特点,对滑模极值搜索算法的控制增益和参考信号进行改进;通过求解微分方程,得到腔体反射信号关于时间和调谐杆位置的函数。通过软件仿真和设计硬件系统,对基于滑模极值搜索算法的调谐过程进行仿真与实际测试,结果显示,所设计的频率稳定系统能够在较短时间内实现SSC-LINAC RFQ腔体功率自动馈入过程且频率稳定度满足设计指标要求,通过了长时间稳定性试验。证明了将滑模极值搜索算法应用于高频谐振腔调谐工作的可行性。

A particle-in-cell mode beam dynamics simulation of medium energy beam transport for the SSC-Linac

A new linear accelerator system,called the SSC-Linac injector,is being designed at HIRFL （the heavy ion research facility of Lanzhou）.As part of the SSC-Linac,the medium energy beam transport （MEBT） consists of seven magnetic quadrupoles,a re-buncher and a diagnose box.The total length of this segment is about 1.75 m.The beam dynamics simulation in MEBT has been studied using the TRACK 3D particle-in-cell code,and the simulation result shows that the beam accelerated from the radio frequency quadrupole （RFQ） matches well with the acceptance of the following drift tube linac （DTL） in both the transverse and longitudinal phase spaces,and that most of the particles can be captured by the final sector focusing cyclotron for further acceleration.The longitudinal emittance of the RFQ and the longitudinal acceptance of the DTL was calculated in detail,and a multi-particle beam dynamics simulation from the ion source to the end of the DTL was done to verify the original design.

Beam dynamics simulation of HEBT for the SSC-linac injector

The SSC-linac （a new injector for the Separated Sector Cyclotron） is being designed in the HIRFL （Heavy Ion Research Facility in Lanzhou） system to accelerate 238U34＋ from 3.72 keV/u to 1.008 MeV/u. As a part of the SSC-linac injector, the HEBT （high energy beam transport） has been designed by using the TRACE-3D code and simulated by the 3D PIC （particle-in-cell） Track code. The total length of the HEBT is about 12 meters and a beam line of about 6 meters are shared with the exiting beam line of the HIRFL system. The simulation results show that the particles can be delivered efficiently in the HEBT and the particles at the exit of the HEBT well match the acceptance of the SSC for further acceleration. The dispersion is eliminated absolutely in the HEBT. The space-charge effect calculated by the Track code is inconspicuous. According to the simulation, more than 60 percent of the particles from the ion source can be transported into the acceptance of the SSC.

Particle-in-cell mode beam dynamics simulation of the low energy beam transport for the SSC-linac injector

A new SSC-linac system （injector into separated sector cyclotron） is being designed in the HIRFL （heavy ion research facility of Lanzhou）. As part of SSC-Linac, the LEBT （low energy beam transport） consists of seven solenoids, four quadrupoles, a bending magnet and an extra multi-harmonic buncher. The total length of this segment is about 7 meters. The beam dynamics in this LEBT has been studied using three-dimensional PIC （particle-in-cell） code BEAMPATH. The simulation results show that the continuous beam from the ion source is first well analyzed by a charge-to-mass selection system, and the beam of the selected charge-to-mass ratio is then efficiently pre-bunched by a multi-harmonic buncher and optimally matched into the RFQ （radio frequency quadrupole） for further acceleration. The principles and effects of the solenoid collimation channel are discussed, and it could limit the beam emittance by changing the aperture size.

SSC直线注入器RFQ腔体多物理场分析

SSC-LINAC是为兰州重离子研究装置(HIRFL)设计的直线注入器,它将U34+离子加速到1 Me V/u注入到分离扇回旋加速器(SSC)中,为冷却储存环(CSR)提供10 Me V/u的U34+。该注入器可以将SSC引出的重离子流强提高一个量级以上。SSC-LINAC由一个RFQ(Radio Frequency Quadrupole)加速器和4个DTL(drift tube linac)组成,设计频率为53.667 MHz。RFQ工作在连续波模式,设计功率30 k W,如果不能有效地冷却,高频电流在电极表面产生的热量会使RFQ的腔壁和电极发生形变,从而导致腔体频率的漂移以及加速和聚焦电场的改变。因此,为了保证连续波工作的RFQ加速器稳定运行,对水冷模式和通道设计提出了很高的要求。作者用有限元软件ANSYS对RFQ进行高频电磁场、温度场、结构应力的耦合分析,验证了冷却方案设计的可行性和可靠性。

一种应用于HIRFL-CSR上的非拦截式剩余气体电离束流剖面探测器（英文）

兰州重离子加速器冷却储存环主环(CSRm)上成功应用了一种剩余气体电离剖面探测器(IPM),这种新型非拦截式剖面探测器的应用服役对CSRm的束流冷却研究及常规调束的实时剖面监测具有重要意义。IPM探测器通过收集束流与剩余气体之间的电离产物(气体离子或电子),利用偏转静电场将电离产物加速至多重微通道板(MCP),并在其上进行电子放大,放大的信号电子随后在荧光屏(P46等)上进行电子-光子转换,最终含有束流剖面信息的投影光子被真空靶室外的CCD相机获取。在正式应用于CSRm之前,IPM探测器还在分离扇回旋加速器直线(SSC Linac)上进行了束流实验,并与传统单丝扫描剖面探测器进行了对比。IPM探测器与单丝刮束器的剖面测量结果相近,并且具有较好的信噪比和约60μm的较高空间分辨率。这种IPM探测器可以利用电阻串联进行均匀分压,较便捷地应用于真空度较低的直线加速器,还可以改造为分离电极单独供压的结构,应用在超高真空需要烘烤的环形加速器。最后还介绍了一种全新紧凑型结构的IPM探测器设计,该设计利用一套IPM探测器实现束流横向水平与垂直两个方向的剖面测量功能,这种紧凑型IPM结构尤其在空间紧缺型的强流直线加速器上具有重大的应用价值。