CSRe的 Schottky束流诊断系统的研制

介绍了Schottky信号的产生原理。研制了CSRe的Schottky束流诊断系统,该系统由一对平行的Schottky电极板、四分之一波螺旋谐振腔、低噪声放大器及数据获取系统组成。利用能量为481.88 MeV/u的78Kr36+束流对Schottky束流诊断系统进行灵敏度测试。结果表明该系统能够测量流强大于82 nA的束流。     

29Si NMR研究TEOS/DDS双前驱体体系的水解动力学

原位引入有机组分对氧化硅体系改性是合成有机-无机杂化硅材料的重要方法. 利用原位的²⁹Si液体核磁, 研究了甲醇为溶剂、氨水催化条件下的四乙氧基硅烷(TEOS)和二甲基二乙氧基硅烷(DDS)原位共水解的动力学过程. 通过改变反应体系中氨和水的浓度, 拟合出单体及中间产物浓度随时间的变化曲线, 得到了TEOS和DDS各自的水解速率常数以及相应各反应物的反应级数. 与单前驱体水解一致的是, 在双前驱体系中TEOS和DDS自身的反应级数仍保持一级, 但是氨和水的反应级数都有不同程度的增大. 与单前驱体水解速率方程相比, 混合体系中TEOS的水解速率常数增大. 同时, DDS在双前驱体中比单前驱体中的水解速率常数有很大程度的减少. 水解动力学表明, TEOS和DDS在双前驱体体系中显示出更平行的水解速率. 利用固体²⁹Si MAS NMR, XPS及小角X射线散射(SAXS)手段对双前驱体体系研究得到的信息显示, 碱催化条件下原位的TEOS水解中间物与DDS中间产物的原位共缩聚程度很弱.     

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60 μm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。A new non-intercepting beam profile monitor, residual gas Ionization Profile Monitor (IPM), has been developed and tested at the main Cooling Storage Ring of Heavy Ion Research Facility in Lanzhou (HIRFL-CSRm). It has been successfully used for studies of electron cooling mechanisms, as well as profile monitoring under normal-mode operation in HIRFL-CSRm. The IPM measures the distribution of ions resulting from the residual gas ionization during the beam passage. The gas ions are collected and multiplied by tandem-type MCPs and a phosphor screen, and eventually captured by a commercial CCD camera outside the vacuum chamber. Before formally applied in HIRFL-CSRm, the IPM was tested and compared with a conventional wire scanner profile monitor at Sector Separated Cyclotron Linac (SSC Linac). Both results show good agreement. Besides, the IPM has higher signal to noise ratio than the wire scanner. It also has a very high spatial resolution of around 60 μm. This monitor can be used for low vacuum like Linac with resistance for bias voltage, or for ultra-high vacuum with discrete electrodes for bias voltage where the bakeout process is essential. Furthermore, a novel and compact design of one IPM with capability of detecting both horizontal and vertical profile is proposed. This compact IPM is quite suitable for non-invasive profile diagnostics at space shortage and high-current Linac.     

CSRm变谐波加速

 在研究兰州重离子冷却储存环(HIRFL-CSR)纵向相振荡运动特性的基础上,对主环(CSRm)内重离子的加速过程进行了模拟研究。选取由扇聚焦回旋加速器（SFC）剥离注入的能量为7 MeV/u,动量散度为±0.5%的¹²C⁶⁺典型离子,模拟了CSRm内束流的加速过程,加速的最终能量为1 GeV/u。在加速过程中采用了变换谐波的方式,解决了较低能量下的加速问题。模拟结果给出了不同时刻粒子在纵向相空间的分布以及各主要高频参数随时间的变化曲线。     

Longitudinal Schottky spectra of a bunched Ne10+ ion beam at the CSRe

The longitudinal Schottky spectra of a radio-frequency (RF) bunched and electron cooled ²²Ne¹⁰⁺ ion beam at 70 MeV/u have been studied by a newly installed resonant Schottky pick-up at the experimental cooler storage ring (CSRe), at IMP. For an RF-bunched ion beam, a longitudinal momentum spread of Δp/p=1.6×10^-5 has been reached with less than 10⁷ stored ions. The reduction of momentum spread compared with a coasting ion beam was observed from Schottky noise signal of the bunched ion beam. In order to prepare the future laser cooling experiment at the CSRe, the RF-bunching power was modulated at 25^th, 50^th and 75^th harmonic of the revolution frequency, effective bunching amplitudes were extracted from the Schottky spectrum analysis. Applications of Schottky noise for measuring beam lifetime with ultra-low intensity of ion beams are presented, and it is relevant to upcoming experiments on laser cooling of relativistic heavy ion beams and nuclear physics at the CSRe.     

Simulation and measurement of the resonant Schottky pickup

A resonant Schottky pickup with high sensitivity, built by GSI, will be used for nuclear mass and lifetime measurement at CSRe. The basic concepts of Schottky noise signals, a brief introduction of the geometry of the detector, the transient response of the detector, and MAFIA simulated and perturbation measured results of characteristics are presented in this paper. The resonant frequency of the pickup is about 243 MHz and can be slightly changed at a range of 3 MHz. The unloaded quality factor is about 1072 and the shunt impedance is 76 kΩ. The measured results of the characteristics are in agreement with the MAFIA simulations.     

冷却储存环CSRm中螺线管场耦合效应研究

介绍了重离子冷却储存环中螺线管场对束流水平方向和垂直方向产生耦合的原理, 由耦合运动方程及耦合系数推导出螺线管场耦合的补偿方法. 结合兰州冷却环主环实际的单元结构,工作点选在束流稳定的差共振附近, 模拟计算了冷却环主环在电子冷却段没有螺线管、有螺线管和增加补偿螺线管三种情况下的束流发射度及此三种情况下冷却环主环的动力学孔径. 通过模拟计算可知螺线管的存在将引起束流的水平方向和垂直方向严重耦合, 由于耦合效应, 垂直方向的发射度将超出其接受度, 致使束流大量损失. 针对这种情况, 提出了在螺线管两端的合适位置增加一组补偿螺线管的校正方案. 模拟结果表明这种措施行之有效.     

Tune调制对HIRFL-CSRm动力学孔径影响的模拟研究

 通过引进包含tune调制的传输矩阵,模拟计算了由四极铁电源纹波所引起的tune调制对HIRFL-CSRm动力学孔径的影响。模拟计算中,对HIRFL-CSRm实际(lattice)跟踪1.0×10⁶圈。从结果可以看出,动力学孔径随调制振幅的增大迅速减小,大体呈线性变化;动力学孔径随调制tune值的变化在研究范围内也有变化,变化的范围在0.049~0.089 m之间。     

CSR电子冷却系统电子束空间电荷效应对电子束温度的影响

 通过求解电子冷却系统中冷却段漂移管区的强流电子束产生的空间电荷场,研究了电子束空间电荷效应对电子温升的影响。结合HIRFL CSR电子冷却系统的典型参数,得到了电子在自身空间电荷场和纵向螺线管磁场组成的交叉场作用下产生的漂移速度和由此引起的附加温度大小,并指出减小电子束空间电荷效应的方法。     

CSRm纵向束流绝热俘获研究

在研究重离子储存环纵向相振荡运动特性的基础上,对CSR主环CSRm内重离子的绝热俘获及加速过程进行了模拟,得出与CSR机器特性相适应的高频参数,并给出了高频参数在绝热俘获过程中随时间的变化曲线