Self-Bunching of a Circulating Beam in the U-70 Proton Synchrotron

The results of an investigation of self-bunching of the U-70 proton synchrotron beam are presented. The self-bunching arises on the top magnetic-field plateau and is caused by the interaction of the beam with the accelerating resonators from which the rf voltage was removed. A specific feature of self-bunching is its anomalously low threshold. It is shown that this is due to the filamentary beam structure, which appears during drfiting of the bunches, and the threshold is determined not by the total but rather the local momentum spread in each filament, continuously decreasing during drifting of the bunches. A novel method used in U-70 to suppress self-bunching is described.     

同步加速器束流能量自动切换控制系统

带电粒子放射治疗中3D主动治疗方式需要不同的束流能量照射不同的病灶切面,这就需要同步加速器控制系统能实现多级束流能量的自动切换控制并提供接口对接治疗计划进行自动变能控制。本文开发了同步加速器束流能量切换控制系统,同步加速器的前端服务器中存储着执行1个同步加速器加速周期所需的全部控制数据集,其中控制数据通过索引标号对其进行区分,同步事例信息是同步加速器多级束流能量切换的触发信号。当前端控制器被同步时间系统的同步事例触发激活后,从DSP波形发生器的SDRAM空间中读出磁铁电源、高频等控制数据进行数据切换。同步事例信号包含同步触发信息、束流能量控制数据的索引信息和控制数据的更新操作信息。多级束流能量自动切换控制系统能实现255级束流能量间自动切换控制（碳束能量在50～500 MeV间切换,步长可控制在1.77 MeV）,完全能满足实际中碳束能量在50～500 MeV间以10 MeV为步长的自动切换控制。     

Acceleration of Carbon Nuclei up to Relativistic Energy in the U-10 Synchrotron

The reconstruction of a system of ring-shaped accelerators has been completed at the Institute of Theoretical and Experimental Physics: carbon nuclei have been accelerated in the U-10 synchrotron up to maximum energy 4 GeV/amu C⁴⁺ ions from a laser ion source are preaccelerated in the I-3 linear injector up to 1.5 MeV/amu and in the UK booster synchrotron up to 50 MeV/amu, injected via the charge-transfer scheme C⁴⁺ C⁶⁺ into the U-10 synchrotron on an increasing magnetic field and accelerated to maximum energy. The basic technological features of the acceleration scheme employed and the results of the first physical experiment with relativistic carbon nuclei are described.     

Upgrade of the Slow-Extraction System in the U-70 Proton Accelerator

The purpose of this work was to increase the efficiency of slow extraction of accelerated protons from the U-70 accelerator in order to provide the extracted beam for a physical setup requiring high intensity. On account of the limited power of the first extraction setup – an electrostatic deflector, the angle spread of the beam near the deflector barrier had to be decreased in order to decrease the losses and increase the efficiency. For this, the structure function was increased by inserting two additional quadrupole lenses into the magnetic structure of the accelerator. As a result of the inadequate strength of the system which corrects the frequencies of the betatron oscillations at the maximum accelerator energy 70 GeV, the beam was extracted at energy 64 GeV, where the frequency of the vertical betatron oscillations could be set above the line of the resonance 4Q _z = 39. As a result, the losses at the first two extraction setups increased by a factor of 3 and the efficiency of the slow-ejection system increased from 85% to 95%.     

Radiation-Insensitive Silicon Oxynitride Films for Use in Silicon Devices---Part II

We report here on the interface state densities at the Si/Silicon Oxynitride (SiON) interface before and after ionizing irradiation, on extended B T tests on Si/SiON capacitors, and on the fabrication and properties of SiON passivated bipolar transistors and P-channel IGFETs. Preliminary data are also presented for gold and copper diffused capacitor structures. The fast state density Nfs after a 1/2 hr. anneal in H2 at 900°C is approximately 8x1010 eV-1 cm-2 near midgap, and increases into the high 1011 eV-1 cm-2 range near the band edges. After an absorbed dose of 1.3 Mrads, the densities near midgap had increased by a factor of 1.3, but showed little change near the band edges. B-T tests under negative bias at l.6×106 V/cm and at temperatures up to 330°C showed a Vfb drift of 2-3 V to more positive values during the first hour, which did not change thereafter; very little drift occurred under positive bias and the same test condition. Test duration was 63 hours for either polarity of bias. This BT-stability, observed on Si/SiON/Al structures, is often lost after gold wire thermocompression bonding. Si/SiON/ tungsten-gold contacts showed no deterioration after thermocompression bonding. SiON passivated type 16F NPN bipolar transistors had initial gain characteristics similar to SiO2 passivated controls, whereas their tolerance to ionizing radiation was much greater. Degradation of hFE to 50% of the initial gain occurred for the SiO2 passivated devices after an absorbed dose of about 1 Mrad and for the SiON passivated devices after 35 Mrads.     

Status of the U-70 Accelerator at the Institute of High-Energy Physics

A brief history of the development and the present status of the accelerator complex at the Institute of High-Energy Physics are presented. The problems facing this complex, which mainly involve increasing the intensity of the accelerated proton beams, decreasing particle losses, and producing an efficient extraction system for high-intensity beams, are expounded. The possibility of accelerating beams of light nuclei, which are a promising tool for performing fundamental and applied research, is discussed. Attention is focused on the upgrading and reconstruction of the systems in the accelerator complex which are being performed for solving these problems.     

3 GHz Superconducting Accelerator Cavity for Use in an Electron Synchrotron

Experience has shown that superconducting accelerator cavity performance improves as the operating frequency rises. To use this effect to advantage in an electron synchrotron one must develop cavities of aperture large enough to provide the necessary phase space admittance and of such a configuration as to avoid problems with lost particles and synchrotron radiation in the orbit plane. The development of such a cavity, open in the mid-plane, is described and test results given.     

The Application of Synchrotron Radiation Techniques to the Study of Domain Structures and their Dynamics in Ferroic Crystals

The recent research work on domain structures and their dynamics in fenoelastic and ferroelectric crystals by white-beam synchrotron radiation topography is summarized.The real-time imaging,fine-beam Laue diffraction,and anomalous-scattering topography were carried out to the study of the domain structures and phase transition in the ferroelastic NdP5O14 and LaP5O14,and ferroelectric KTa1-xNbxO3,(Ba0.25Sr0.75)0.9(K0.5Na0.5)0.2Nb2O6,and KTiOPO4 crystals.Some preliminary results are presented and discussed.     

Calculation of Beam Extraction Pulse Duration for Beam Angular Divergence Measurement of EAST Neutral Beam Injection

Distributed thermocouple measurement will be used on EAST neutral beam injection beam angular divergence measurement. In order to determine the pulse duration of neutral beam extraction, the plates of calorimeter are analyzed by using heat transfer science. Mathematic derivations and the results are given according to the installation location of thermocouple in the plate. Those results could point the way to beam angular divergence measurement of EAST neutral beam injection.     

北京正负电子对撞机同步辐射X射线能谱的测量

本文提供了北京正负电子对撞机同步辐射光束线上X射线能谱的首次测量结果,文章对探测器和谱仪系统、测量方法及数据分析予以扼要的描述。     

强流氘束引出系统与加速管束流匹配的研究

为增加传输通过加速管的束流强度,提高中子发生器的中子产额,采用Particle-in-cell(PIC)程序模拟研究了入射束强度在10～150 mA范围内,不同初始参数条件下D⁺₁束在加速管中的传输状态。结果表明,当入射束在加速管入口处的归一化发射度取0.25 πcm•mrad,Courant-Snyder参数α=-4、β=60 cm/rad时,50～100 mA D⁺₁束与加速管匹配良好。根据匹配参数,对双等离子体离子源的引出系统进行了优化,结果显示,在引出系统与加速管之间放置两个螺线管透镜和1个光阑,能有效去除D⁺₂、D⁺₃离子,实现100 mA D⁺₁束顺利传输通过加速管的目的。     

同步辐射区光束线位置测量系统的控制和数据获取

介绍了上海同步辐射光源的X射线光束位置测量系统的控制和数据获取,具体描述了位置测量系统的控制和数据获取的总体设计、原理和软件系统,以及在上海同步辐射光源(SSRF)光束线线站的应用。     

Experimental Results of Ion Beam Extraction of High-Current Ion Source for EAST Neutral Beam Injector

The first campaign of ion beam extraction tests are completed for EAST NBI high current ion source. The hydrogen ion beam with beam voltage of 80 keV is extracted from tetrode accelerator system. During the experiment, the characteristics of arc discharge and ion beam extraction are studied. The arc power reaches 120 kW and the extracted ion beam power reaches 3 MW. The relationship of some key parameters of arc and beam are investigated, and the details are described in this paper.     

中国散裂中子源快循环同步加速器环斜切型束流位置探测器设计

束流位置探测器(BPM)是加速器束流测量系统的重要组成部分。本文通过在斜切型BPM的差和比计算式中引入相对电极间的耦合电容及电容差,解释实测灵敏度偏小、存在零点偏移量的原因。结合模拟软件CST的仿真结果及推得的计算式,得到BPM几何结构与电子学参数的关系。最后,基于CSNS-RCS环上参数及电子学要求,得到优化的BPM几何结构及其电子学参数值。     

壁电流探测器在中国散裂中子源快循环同步加速器调束中的应用

快循环同步加速器（RCS）是中国散裂中子源（CSNS）的重要组成部分。负氢粒子束经直线加速器加速至80 MeV,剥离成质子束注入至RCS环并加速累积至1.6 GeV引出打靶。束流通过安装在RCS环的壁电流探测器（WCM）感应得到束流的强度信息,环高频与环主二极磁铁的失配会导致束流的实际振荡偏离理论预测。本文通过对WCM的数据进行分析得到了纵向工作点、束流的实际振荡频率、束团的电荷量、束团的形状变化等信息,方便了加速器的调束,并对参数测量中的测量误差进行了分析。     

Achievement of 100 s Long Pulse Neutral Beam Extraction in EAST Neutral Beam Injector

Neutral beam injection (NBI) is recognized as one of the most e®ective means for plasma heating. A 100 s long pulse neutral beam with 30 keV beam energy, 10 A beam current and a 100 s long pulse modulating neutral beam with 50 keV beam energy, 16 A beam current were achieved in the EAST neutral beam injector on the test-stand. The preliminary results suggest that EAST-NBI system initially possess the ability of long pulse beam extraction.     

中国散裂中子源靶站中子通道初步屏蔽计算分析

基于中国散裂中子源靶站中子通道设计,采用二维离散纵标程序DORT对中子导出通道各种设计方案的屏蔽效果进行计算分析。计算得出二维剂量场分布及通道中心处剂量当量率轴向分布,并得到较优化的屏蔽方案及模型,确保谱仪大厅内工作人员接受的剂量低于规定的标准。结果表明,未安装谱仪的中子通道屏蔽模型中心含有SS316合金钢时的屏蔽效果较好,剂量在辐射防护标准以下,符合设计要求。中子孔道开闭装置屏蔽模型中前端加入钨板屏蔽效果较好,并随钨板长度的增加,屏蔽效果提高。     

辐照样品孔塞短杆抓取工具的研制

分析压水堆核电厂中现有的孔塞抓具在抓取辐照样品孔塞时的局限性和操作风险,引出辐照样品孔塞短杆工具的研制,阐述短杆工具的使用优点和对现有抓具功能上的补充,希望能提高大修中孔塞抽取工作的安全水平。