TOPOPIC对强流束流在周期FODO结构中的传输研究

粒子云网格(Particle In cell,PIC) 方法是研究带电粒子在加速器中运动的关键工具之一。基于PIC 算法,开发了模拟强流条件下的束流动力学模拟程序TOPOPIC(Trace of Particle Orbit with PIC method),并且利用TOPOPIC,研究了束流在四极铁周期结构(FODO) 中的传输问题。结果表明,在强流条件下空间电荷效应显著地影响了束流的整体行为和单粒子的运动轨迹。最后比较了TOPOPIC 程序和通用的BEAMPATH 程序在相同条件下的计算结果,可以看到两个程序给出的模拟结果吻合得非常好,这表明TOPOPIC程序的计算结果是合理、可靠的。The Particle in cell (PIC) method is one of the key techniques in the research of charged particles in accelerators. Based on the PIC method, a new beam simulation code for high intensity beam named TOPOPIC (Trace of particle orbit with PIC method) has been developed. With the code TOPOPIC,the beam behavior during passing through the periodic quadrupole (FODO) structure has been studied. The results show that the nonlinear space charge affects the single particle behavior and beam envelope a lot. At last, the PIC code BEAMPATH is used for benchmark, the results given by TOPOPIC and BEAMPATH show good agreements,which means the code TOPOPIC is reliable.     

Beam dynamics study of RFQ for CADS with a 3D space-charge-effect

The ADS (accelerator driven subcritical system) project was proposed by the Chinese Academy of Sciences. The initial proton beams delivered from an electron cyclotron resonance ion source can be effectively accelerated by 162.5 MHz 4.2 m long room temperature radio-frequency-quadrupoles (RFQ) operating in CW mode. To test the feasibility of this physical design, a new Fortran code for RFQ beam dynamics study, which is space charge dominated, was developed. This program is based on Particle-In-Cell (PIC) technique in the time domain. Using the RFQ structure designed for the CADS project, the beam dynamics behavior is performed. The well-known simulation code TRACK is used for benchmarks. The results given by these two codes show good agreements. Numerical techniques as well as the results of beam dynamics studies are presented in this paper.     

Study of a magnetic alloy-loaded RF cavity for bunch compression at the CSR

The Heavy Ion Research Facility and Cooling Storage Ring（HIRFL-CSR）accelerator in Lanzhou offers a unique possibility for the generation of high density and short pulse heavy ion beams by non-adiabatic bunch compression longitudinally,which is implemented by a fast jump of the RF-voltage amplitude.For this purpose,an RF cavity with high electric field gradient loaded with Magnetic Alloy cores has been developed.The results show that the resonant frequency range of the single-gap RF cavity is from 1.13 MHz to 1.42 MHz,and a maximum RF voltage of 40 kV with a total length of 100 cm can be obtained,which can be used to compress heavy ion beams of 238U72＋ with 250 MeV/u from the initial bunch length of 200 ns to 50 ns with the coaction of the two single-gap RF cavity mentioned above.     

基于表面增强拉曼散射特征峰位移检测触珠蛋白

急性脑梗死(Acute cerebral infarction, ACI)具有起病急、死亡率高的特点,快速判断ACI的发生发展对患者的诊治和预后方案的制定具有关键作用。研究表明,人血清中触珠蛋白(Haptoglobin, Hp)的含量水平与ACI有关。本研究采用表面增强拉曼散射技术(Surface enhanced Raman scattering, SERS)结合免疫反应,建立了血清中Hp的定量分析方法。首先,在硅片上制备银纳米粒子SERS基底,以4-巯基苯甲酸(4-Mercaptobenzoic acid, MBA)为拉曼探针,通过形成Ag—S键将其连接在纳米粒子表面,MBA的羧基与自制的高效价Hp抗体的氨基通过酰胺键共价交联连接到SERS基底上,从而形成检测Hp的SERS自组装芯片(Ag/MBA/anti-Hp)。Hp可以被Ag/MBA/anti-Hp基底上的抗体特异性捕获,从而引起MBA的SERS特征峰发生位移。结果表明,Hp浓度的对数与MBA的SERS特征峰位移之间存在良好的线性关系,线性范围为1～1000 ng/mL(R²=0.988)。采用本方法对9...