RFQ加速器同时加速同荷质比正负离子的实验研究

阐述了利用北京大学26MHz 300keV整体分离环高频四极场(ISR RFQ)加速器同时加速同荷质比正负离子的研究结果.分别用O⁺和O^－离子的连续束以及脉冲束同时注入,均实现了RFQ加速器对同荷质比正负离子的同时加速.用快靶测得的经RFQ腔同时加速后形成的O⁺及O^－离子微脉冲束与预想的正负氧离子微脉冲束相位关系完全一致.证实了同时加速时得到的氧离子束总和明显高于单加速一种离子时得到的氧离子束.在国际上首次实现了用RFQ加速器同时加速同荷质比的正负离子.     

分离作用射频四极场加速器的结构和工艺设计

 介绍了北京大学分离作用射频四极场(RFQ)加速器的结构特点,包括膜片式电极、支撑环式电极支撑系统、水冷系统、调谐系统及其工艺实现;介绍了基于该分离作用RFQ加速腔进行的调谐测试、高功率实验和束流实验。结果表明:调谐系统的频率调节范围及品质因数完全满足实验要求;分离作用RFQ加速腔的输入功率可以达到33 kW以上,满足高功率下稳定运行的条件;在束流实验中,把1.03 MeV的O⁺入射束流加速到1.65 MeV,半高宽能散小于3%。加速器结构满足物理设计要求,加速系统运行稳定。     

利用QMD分析中高能质子入射208Pb的(p,xn)反应双微分截面

中高能质子入射重金属靶产生散裂中子是加速器驱动洁净核能系统的一个关键部分.利用量子分子动力学(QMD)模型研究入射质子能量在300MeV—1.5GeV,散裂靶为²⁰⁸Pb的(p,xn)核反应的双微分截面,QMD计算结果很好再现了实验数据,且QMD的计算结果明显优于HETC和LAHET.QMD在较宽的能区和核区满足加速器驱动洁净核能系统散裂靶物理计算的要求.     

半导体器件单粒子效应的加速器模拟实验

 着重描述了应用加速器开展半导体器件的单粒子效应实验研究的方法。采用金箔散射法可以降低加速器束流几个量级，从而满足半导体器件单粒子效应实验的要求。研制的弱流质子束流测量系统和建立的质子注量均匀性测量方法解决了质子注量的准确测量问题。实验测得静态随机存取存储器的质子单粒子翻转截面为10^-7 cm²·bit^-11量级，单粒子翻转重离子LET阈值为4～8MeV·cm²/mg，重离子单粒子翻转饱和截面为10^-7 cm²·bit^-1量级。     

在加速器上探测周围的超对称暗物质

探讨了在加速器上直接检测周围超对称暗物质的可能性, 计算了暗物质与e⁺e^－和强子对撞机上束粒子碰撞的弹性和非弹性散射截面.     

用HI-13串列加速器质谱装置测量182Hf的研究

¹⁸²Hf的半衰期为(8.90±0.09)Ma, 是一个接近灭绝的放射性核素. 超新星爆炸是自然界中已知的惟一能产生¹⁸²Hf的途径. 因此¹⁸²Hf是研究近1亿年来在地球附近可能发生的超新星事件的理想核素. 另外, ¹⁸²Hf是核工程中特别感兴趣的一个长寿命放射性核素. 精确测量超痕量的¹⁸²Hf对反应堆的设计和核天体物理学以及其他研究领域都是非常重要的. 用加速器质谱有可能实现对超低含量¹⁸²Hf的测量. 在中国原子能科学研究院的HI-13加速器质谱装置上对¹⁸²Hf的测量方法以及样品的化学去钨方法进行了研究, 分别得到了空白样品以及系列标准样品的¹⁸²Hf和¹⁸³W的能量-飞行时间双维谱. ¹⁸²W对¹⁸²Hf计数的贡献是通过测量¹⁸³W的计数归一扣除的. 目前本工作对¹⁸²Hf的测量灵敏度为4.15±10^－11 (¹⁸²Hf/¹⁸⁰Hf比值).     

利用加速器质谱计测量10Be形成截面

加速器质谱计具有很高的灵敏度,能测量样品中含量极微的杂质同位素.¹⁰Be是一种宇宙成因核,在地学、环境科学和宇宙学等领域有广泛的应用,它为纯β衰变核,端点能量低且半衰期很长.采用测量剩余核放射性方法确定¹⁰Be形成截面很困难.本文报道利用加速器质谱计技术测量¹⁰Be反应总截面的方法和结果,并对应用前景作了讨论.     

北京散裂中子源RCS注入系统物理设计和研究

北京散裂中子源(BSNS)的主加速器——快循环同步加速器(RCS)采用H^－剥离注入方法, 将从直线加速器预加速的束流进行累积和进一步加速. 束流损失率的控制是该类高功率质子加速器所面临的关键问题之一, 而束流损失中很重要的部分是由空间电荷效应造成的. 为了减小该类束流损失, 注入系统设计中利用H^－剥离注入和相空间涂抹方法将直线加速器预加速的发射度较小的束流尽可能均匀地涂抹到较大的横向相空间中. 与其他的类似加速器相比, RCS注入系统将所有注入元件放在一个长为9m的无色散漂移节中以充分节省RCS环的纵向空间, 并使对注入系统的操作与对RCS主体的操作完全独立. 对于RCS累积的粒子数1.9×10¹³, 空间电荷效应对粒子的运动有非常重要的作用, 本文介绍了采用ORBIT程序进行三维模拟计算并进行设计优化的结果. 还介绍了系统设计时需要考虑的其他重要因素, 如质子穿越、电子收集等.     

V2质子静电加速器的改进与现状

V2质子静电加速器(简称V2)在1958年建成,已运行40年.现在最高运行能量为2.4MeV;质子束流强度为微安量级(0.6—2.5μA).磁分析器磁铁励磁电流电源稳定度为±0.01%,加速器能量分辨率可达1‰.改变了输电带的分压装置,使更换输电带更为方便.添加了三岔管道,增加了外束.从70年代以来,V2主要用于核分析工作.最近开展了用离子感生发光法对外长石中铁的不同化学价态Fe²⁺和Fe³⁺进行了分析,Fe²⁺和Fe³⁺光谱峰分离,清晰可辨.     

分离作用RFQ加速系统研究进展

介绍了SFRFQ加速系统的最新研究进展. 为验证SFRFQ结构的抗打火性能, 设计了一个高功率模型腔, 进行了高功率打火实验, 并最终证明了该结构的可行性. 为验证SFRFQ加速器的载束性能, 设计了一台长度仅为1m的600keV O⁺ SFRFQ加速器, 它将把从1MeV ISR RFQ引出的O⁺离子加速到1.6MeV. 为解决1MeV ISR RFQ引出束流与SFRFQ加速器的横向匹配问题, 在其间插入了一个三单元磁四极透镜. SFRFQ加速器加工和1MeV ISR RFQ改造的进展顺利.     

Beam dynamics and RF design of trapezoidal IH-RFQ with low energy spread

Beam dynamics and RF design have been performed of a new type trapezoidal IH-RFQ operating at 104 MHz for acceleration of ¹⁴C⁺ in the framework of RFQ based ¹⁴C AMS facility at Peking University. Low energy spread RFQ beam dynamics design was approached by the method of internal discrete bunching. ¹⁴C⁺ will be accelerated from 40 keV to 500 keV with the length of about 1.1 m. The designed transmission efficiency is better than 95% and the energy spread is as low as 0.6%. Combining the beam dynamics design, a trapezoidal IH-RFQ structure was proposed, which can be cooled more easily and has better mechanical performance than traditional RFQ. Electromagnetic field distribution was simulated by using CST Microwave Studio (MWS). The specific shunt impedance and the quality factor were optimized primarily.     

Beam dynamics and RF design of trapezoidal IH-RFQ with low energy spread

Beam dynamics and RF design have been performed of a new type trapezoidal IH-RFQ operating at 104 MHz for acceleration of 14C+ in the framework of RFQ based 14C AMS facility at Peking University. Low energy spread RFQ beam dynamics design was approached by the method of internal discrete bunching. 14C+ will be accelerated from 40 keV to 500 keV with the length of about 1.1 m. The designed transmission efficiency is better than 95% and the energy spread is as low as 0.6%. Combining the beam dynamics design, a trapezoidal IH-RFQ structure was proposed, which can be cooled more easily and has better mechanical performance than traditional RFQ. Electromagnetic field distribution was simulated by using CST Microwave Studio (MWS). The specific shunt impedance and the quality factor were optimized primarily.     

分段共振耦合RFQ场调谐方法研究

强流质子加速器需要采用分段共振耦合RFQ作为其低能加速结构,为减少束流损失,RFQ加速器必须达到所要求的场分布.针对共振耦合结构的特殊性,在RFQ传输线模型的理论基础上,在一台RFQ冷模型上进行了场调谐的实验研究,获得了满意的实验结果.同时,也验证了作者用LabVIEW编写的RFQ场调谐程序的正确性.     

BNCT中子源用RFQ加速器

 分析了加速器作为硼中子俘获治疗(BNCT)中子源的优势，提出以射频四极场（RFQ）加速器作为BNCT用中子源的首选机型。对该RFQ的参数进行了选择，利用质子轰击锂靶近阈反应产生的前冲中子束能散低、散角小的优势，设定RFQ最终能量为1.9 MeV。采用“匹配均温”设计方法进行了此强流质子RFQ的束流动力学设计，并对设计方案进行了传输模拟，在入口归一化均方根发射度为0.25 mm·mrad、流强为100 mA时，束流传输效率为99.3％。选择合适厚度的锂靶，经过整形即可得到满足BNCT治疗需要的中子束。     

Design study of a radio-frequency quadrupole for high-intensity beams

The Rare isotope Accelerator Of Newness(RAON) heavy-ion accelerator has been designed for the Rare Isotope Science Project(RISP) in Korea. The RAON will produce heavy-ion beams from 660-MeV-proton to200-MeV/u-uranium with continuous wave(CW) power of 400 k W to support research in various scientific fields.Its system consists of an ECR ion source, LEBTs with 10 ke V/u, CW RFQ accelerator with 81.25 MHz and 500 ke V/u, a MEBT system, and a SC linac. In detail, the driver linac system consists of a Quarter Wave Resonator(QWR) section with 81.25 MHz and a Half Wave Resonator(HWR) section with 162.5 MHz, Linac-1, and a Spoke Cavity section with 325 MHz, Linac-2. These linacs have been designed to optimize the beam parameters to meet the required design goals. At the same time, a light-heavy ion accelerator with high-intensity beam, such as proton,deuteron, and helium beams, is required for experiments. In this paper, we present the design study of the high intensity RFQ for a deuteron beam with energies from 30 ke V/u to 1.5 MeV/u and currents in the m A range. This system is composed of an Penning Ionization Gauge ion source, short LEBT with a RF deflector, and shared SC Linac. In order to increase acceleration efficiency in a short length with low cost, the 2nd harmonic of 162.5 MHz is applied as the operation frequency in the D~+RFQ design. The D~+RFQ is designed with 4.97 m, 1.52 bravery factor. Since it operates with 2nd harmonic frequency, the beam should be 50% of the duty factor while the cavity should be operated in CW mode, to protect the downstream linac system. We focus on avoiding emittance growth by the space-charge effect and optimizing the RFQ to achieve a high transmission and low emittance growth. Both the RFQ beam dynamics study and RFQ cavity design study for two and three dimensions will be discussed.     

The R/D of high power proton accelerator technology in China

In China, a multipurpose verification system as a first phase of our ADS program consists of a low energy accelerator (150 MeV/3 mA proton LINAC) and a swimming pool light water subcritical reactor. In this paper the activities of HPPA technology related to ADS in China, which includes the intense proton ECR source, the RFQ accelerator and some other technology of HPPA, are described.     

小型加速器质谱系统研制及分析技术研究

加速器质谱(AMS)是测量长寿命放射性核素灵敏度最高的分析技术,在环境、地质、考古、物理等领域有着广泛应用。近年来,AMS装置的小型化在国际上得到了很大发展。为了研发小型化AMS装置及其分析技术,中国原子能科学研究院分别自主研制了加速电压为0.2 MV的单极型AMS装置和端电压为0.3 MV的串列型AMS装置。基于研制的单极型AMS装置,成功开展了14C的高效传输和本底排除技术研究,实现了14C的高灵敏测定,14C/12C的测量灵敏度达到2×10–15;利用研制的串列型AMS装置,开展了低能量下129I的气体剥离条件、本底排除和探测方法研究,建立了129I的高效传输和高灵敏测量方法,129I/127I的测量灵敏度为1×10–14。这是国内首次研制成功小型AMS装置,为AMS国产化奠定基础。     

200MHz质子带窗四翼型射频四极场加速器结构模拟研究

根据束流动力学设计方案,使用电磁场计算软件CST Microwave Studio对带窗四翼型射频四极场(RFQ)结构进行了模拟研究,分析了加速腔结构参数对其物理特性的影响,得到了200MHz质子带窗四翼型RFQ优化结构方案。该结构的比分路阻抗为79.5kΩ·m,模式间隔达25.802MHz。与传统的四翼型RFQ比较结果表明:带窗四翼型RFQ具有较低的工作频率范围、良好的电稳定性以及较高的比分路阻抗。     

MAFF — The Munich accelerator for fission fragments

At the new high flux reactor FRM-II in Munich the accelerator MAFF (Munich accelerator for fission fragments) is under design. In the high neutron flux of 10¹⁴ n/cm² s up to 10¹⁴ neutron-rich fission fragments per second are produced in the 1 g U-235 target. Ions with an energy of 30 keV are extracted from the ion source. In the mass separator two isotopes can be selected. One of the beams is used for low energy experiments, the other one is injected into an ECRIS (or EBIS) for charge breeding to a q/A≥0.16. A gas filled RFQ cooler is used for emittance improvement. The subsequent LINAC delivers beams with an energy ranging from 3.7 MeV/u to 5.9 MeV/u. New IH structures are being developed at the Munich tandem laboratory. A small storage ring is planned in a further stage to recycle the fission fragments. A thin target foil can be placed into this ring, e.g., for synthesis of super-heavy elements. The through-going beam tube has been installed in the heavy water tank of the reactor. Tests of the target ion source in a special oven to test long term stability and safety tests were in progress.     

RFQ加速器中二极模稳定杆作用机理的研究

RFQ加速器中的二极模场给束流施加一个偏转力,导致束流损失在机器上.因此,必须采取降低二极模场的措施.人们提出采用二极模稳定杆使二极模频率远离四极工作模.在一台RFQ冷模上开展的实验研究中,发现了一些与二极模稳定杆作用机理相关的新现象,本文报告这些实验结果,并对其进行分析解释.根据这些结果,提出,利用非对称性地插入二极模稳定杆,可以降低非对称RFQ腔体中的二极模场分量.