RF knock-out extraction in HITFiL

A compact facility for cancer therapy has been designed and is presently under construction. A slow beam extraction system using the RF-Knock Out method and 3rd-order resonance is adopted in the synchrotron of this facility. Eight sextupoles are used, four of them are for correcting the chromaticity and the rest for driving the 3rd-order resonance. In order to save the aperture of vacuum chamber, a 3-magnet bump is adopted during the extraction process. The extraction phase space map and the last 3 turns' particle trajectory before extraction are given. The matching betatron functions with HEBT (high energy beam transport) are also presented.     

CSRm束流径向和轴向振荡的耦合

 介绍了由于磁铁的安装误差和螺线管的存在而造成的束流径向和轴向的耦合，以及耦合对束流稳定的影响。结合CSRm结构的典型参数分析得出：二极磁铁和四极磁铁在纵向角安装偏差为-0.5~0.5 mrad；有螺线管存在的情况下，工作点落在和共振线时，将导致束流不稳定而大量损失，落在差共振线时，束流稳定。通过模拟计算发现：螺线管产生的耦合远大于磁铁的纵向角安装偏差产生的耦合。     

用逐次线性化法对储存环动力学孔径的解析研究

从逐次线性化法解粒子非线性Betatron振荡方程出发,对存在非线性六极场、八极场及六极场与八极场共存的粒子Betatron振荡方程进行研究.应用线性理论得出了粒子非线性Betatron振荡稳定性的判据,得到了动力学孔径的半解析表达式,分析了在小振幅下,导致粒子非线性不稳定性的另外一种机制———小振幅下,参量共振所引起的自激振荡.用此方法对实际lattice的动力学孔径进行了研究,所得结果与数值跟踪结果吻合得很好     

CSR注入引出高压静电偏转板设计

 利用3维电磁场计算程序MAFIA对CSR注入引出静电偏转板的物理结构进行了理论设计。该偏转板高压电极材料采用表面经过阳极氧化处理的锻铝板材,倒角半径为20mm,电极半宽度60mm,其几何形状能够同时满足电场均匀性、耐压性及机械强度的要求,切割板电极采用半钨丝半钽板的结构,入口厚度不大于0.1mm。在设计基础上制造了偏转板模型,并对之进行了真空模拟试验,结果证明该高压静电偏转板的设计方案是合理的,基本满足物理实验要求。     

兰州重离子直线加速器设计初步

兰州重离子直线加速器是作为兰州重离子冷却储存环(CSR)未来的注入器而开始的一个新项目, 其目的是为CSR提供更好束流品质及更高流强的束流, 更加充分的发挥CSR的潜能, 同时也可以为超重等研究直接提供束流. 其设计最小荷 质比为1/6, 引出能量为16MeV/u, 设计流强为1A.μA, 工作频率为100MHz及其倍频200MHz.采用超导ECR离子源、RFQ及IH型DTL加速结构的方式, 设计总长度小于40m. 整个工程分阶段进行,现阶段的工作重点是第一个IH腔体之前的工作于基频的部分, 本文主要介绍这部分的动力学设计及整台机器的基本参数.     

Electromagnetic characteristics of the CH cavity

In this paper, we present the RF simulation, the fabrication and the normal RF test of a six-cell copper model cross bar H mode (CH) cavity. The CH cavity was researched and developed at the Institute of Modern Physics for Injector II of the superconducting linac of the accelerator driven system of China, operating at a frequency 162.5 MHz, β=0.065. The deep drawing and electron beam welding were employed to fabricate this cavity, which would be used to develop the superconducting CH cavity in the future. The results of the normal RF test agree with the simulation of the electromagnetic properties, such as the electric field distribution on the cavity axis, frequency and Q factor.     

Preliminary design and simulation of a 162.5 MHz high-intensity proton RFQ for an accelerator driven system

A new procedure for the design and simulation of a Radio Frequency Quadrupole (RFQ) accelerator has been developed at the Argonne National Laboratory. This procedure is integrated with the beam dynamics design code DESRFQ and the simulation code TRACK, which are based on three-dimensional field calculations and the particle-in-cell mode beam dynamics simulations. This procedure has been applied to the development of a 162.5 MHz CW RFQ which is capable of delivering a 10 mA proton beam for the Accelerator Driven System (ADS) of the CAS. The simulation results show that this RFQ structure is characterized by the stable values of the beam acceleration efficiency for both the zero current beam and space charge dominated beam. For an average beam current of 10 mA, there is no transverse rms emittance growth, the longitudinal rms emittance at the exit of RFQ is low enough and there is no halo formation. The beam accelerated in the RFQ could be accepted easily and smoothly by the following super-conducting linear accelerator.     

CSRe电子冷却模式下核质量测量研究

研究了CSRe电子冷却模式下使用线性质量刻度时, 空间电荷效应对测量精度的影响、 CSRe上测量190Ir质量的实验可行性以及估算了电子冷却模式下, 使用非线性刻度法所能达到的测量精度。 理论上的分析表明, CSRe在束流和二极铁磁场稳定的理想情况下, 如果电子冷却对同种离子束的冷却效果能达到δp/p=10－6量级, 采用非线性刻度的方法, 能够对像190Ir这样的重离子达到σ(m)/m≈10-8的测量精度。 Nuclear mass measurement by electron cooling mode in CSRe is discussed, mainly in three related aspects: the systematic error caused by the space charge effect in the case of linear mass calibration; the possibility of mass measurement of 190 Ir in CSRe; the estimation of the attainable precision in the case of non linear mass calibration. Theoretic analysis of the attainable precision shows that a precision of σ(m)/m≈10-8 can be achieved if the momentum spread of each kind of ions can be reduced to 10-6 in CSRe.     

Commissioning of electron cooling in CSRm

A new generation electron cooler has started operation in the heavy ion synchrotron CSRm which is used to increase the intensity of heavy ions. Transverse cooling of the ion beam after horizontal multi-turn injection allows beam accumulation at the injection energy. After optimization of the accumulation process an intensity increase in a synchrotron pulse by more than one order of magnitude has been achieved. In given accumulation time interval of 10 seconds, 10⁸ particles have been accumulated and accelerated to the final energy. The momentum spread after accumulation and acceleration in the 10^－4 range has been demonstrated in six species of ion beams. Primary measurements of accumulation process varying with electron energy, electron beam current, electron beam profile, expansion factor and injection interval have been performed. The lifetimes of ion beams in the presence of electron beams were roughly measured with the help of DCCT signal.     

高精度环形谱仪等时性模式的闭轨校正模拟

高精度环形谱仪（SRing）是HIAF装置的重要组成部分,闭轨校正设计是该同步加速器设计的关键部分。由于等时性模式（γ_t=1.43）线性光学水平β函数很大,磁铁场误差及安装误差会引起较大的闭轨畸变,并导致线性光学发生变化。模拟过程采用奇异值分解（SVD）算法,通过多次计算响应矩阵并计算校正铁校正量实现闭轨校正。同时考虑BPM误差的影响,并通过减少特征值使用个数降低校正铁校正量。校正后全环最大闭轨小于0.8 mm,线性光学也得到明显优化。