绝缘微堆质子直线加速器关键技术研究进展

基于绝缘微堆技术的直线加速器由于其能够实现较高的粒子加速梯度,尤其在质子加速及肿瘤治疗领域的优势得到高度关注。目前该种加速器处于研发阶段,有一系列技术和工程问题有待解决。介绍了课题组在过去的两年里围绕建立一台1 MeV质子注入器原型样机在固态脉冲功率系统、绝缘微堆及质子束源等方面取得的研究进展。实现了耐压梯度接近20 MV/m的环形绝缘微堆样品,样品内径30 mm,外径50mm,厚度15mm,基本达到设计要求;固态脉冲功率系统实现了光导开关多路稳定工作模式,开关直流偏置耐压达到20kV,采用激光二极管触发同步系统在15路同步时实现了低于1ns的抖动,输出300kV的电压脉冲,输出电压脉冲宽度10ns;进行了低能质子加速束流动力学的初步分析和模拟工作,模拟结果表明采用微堆结构可以实现质子束的有效加速和传输。     

PSY-g-PAA/Na-MMT复合高吸水性树脂的制备及其对Cu2+的吸附

以欧车前胶(PSY)、丙烯酸(AA)和钠基蒙脱土(Na-MMT)为原料,过硫酸铵(APS)为引发剂,N,N'-亚甲基双丙烯酰胺(MBA)为交联剂,采用水溶液聚合法制备了欧车前胶接枝聚丙烯酸/钠基蒙脱土(PSY-g-PAA/Na-MMT)复合高吸水性树脂.考察了Na-MMT质量分数对复合高吸水性树脂吸水能力和Cu2+吸附...     

FRANZ-KELDYSH OSCILLATION FROM THE SPACE CHARGE REGION OF MBE GaAs FILMS

We have investigated doped MBE GaAs films using photoreflectance (PR) spec-troscopy. Special spectral structures have been observed in the vicinity of the funda-mental band gap, which are quite different from the Franz-Keldysh oscillation (FKO) from uniform electric fields under flatband modulations. Numerical analysis has been performed for FKO from electric fields in the space charge region under non-flatband modulations. Some typical FKO line shapes are illustrated. For moderately doped samples the calculated line shapes are basically consistent with experiments. The surface electric field and the Fermi level pinning have also been deduced from exper-iments.     

小间隙异面电极结构的光导开关

介绍了应用于介质壁加速器的小间隙异面电极结构的光导开关。所用光导开关为异面结构的砷化镓（GaAs）光导开关,电极间隙5 mm,偏置电压为15~22 kV脉冲高压,工作在非线性（高增益）模式,由半导体激光器产生的脉冲激光触发。脉冲激光的中心波长为905 nm,脉冲宽度（FWHM）约20 ns,前沿约3.1 ns,抖动小于200 ps,峰值功率约90 W。实验结果表明:光导开关的偏置电压较低时,开关寿命较长,导通性能较差;偏置电压较高、驱动脉冲激光功率较大时,开关导通性能较好,寿命较短。     

Tailoring of Bandgap and Spin-Orbit Splitting in ZrSe2 with Low Substitution of Ti for Zr

Tuning the bandgap in layered transition metal dichalcogenides（TMDCs） is crucial for their versatile applications in many fields. The ternary formation is a viable method to tune the bandgap as well as other intrinsic properties of TMDCs, because the multi-elemental characteristics provide additional tunability at the atomic level and advantageously alter the physical properties of TMDCs. Herein, ternary Ti_xZr_1-xSe₂ single crystals were synthesized using the chem...     

香港瓜馥木生物碱类化合物的细胞毒活性

研究香港瓜馥木Fissistigma uonicum生物碱类化合物的抗肿瘤细胞活性。采用硅胶、ODS、MCI、Sephadex LH-20等多种柱色谱及制备型高效液相色谱等现代分离技术对香港瓜馥木的化学成分进行分离纯化,并根据其理化性质、NMR波谱技术进行结构鉴定。同时采用MTT比色法筛选对两种不同肿瘤细胞（HepG-2,SGC-7901）的有效抑制浓度。从香港瓜馥木的95%乙醇提取物中分离得到17个化合物,分别鉴定为（1）鹅掌楸碱,（2）氧代克列班宁,（3）subsessilina,（4）芒籽香碱,（5）7-oxodehydrocaaverine,（6）O-methylmoscatoline,（7）观音莲明碱,（8）4,5-dioxodehydroa-similobing,（9）降赛法拉二酮B,（10）aristololactam AIIIa,（11）goniokpedaline,（12）穆坪马兜铃酰胺,（13）顺式阿魏酸酰对羟基苯乙胺,（14）对羟基桂皮酰酪胺,（15）Gusanlung C,（16）5,6,7,8-tetramethoxyflavone,（17）（+）-丁香脂素。化合物芒籽香碱,goniokpedaline,对羟基桂皮酰酪胺是从瓜馥木属中首次分离得到,其余化合物均从该植物中首次分离得到。结果表明生物碱氧代克列班宁、O-methylmoscatoline、aristololactam BIIIa、对羟基桂皮酰酪胺对HepG-2显现了很好的细胞毒活性,化合物O-methylmoscatoline、观音莲明碱、aristololactam AIIIa对SGC-7901有明显的细胞毒活性。     

介质壁加速腔加速结构优化

为了在介质壁加速器中增大轴向加速电场, 提高加速梯度的同时抑制径向电场对束包络的扩张, 提出了在每个加速电极上添加金属栅网结构。采用基于粒子云网格方法的电磁粒子模拟软件对不加栅网与添加栅网的电极结构进行了数值仿真, 分析了不同结构下加速管道中的电场分布和束包络变化。通过实验对比了两种不同结构下经过相同的加速长度获得的粒子能量。结果表明:添加金属栅网结构相对于不加栅网的金属小孔式结构, 轴向加速电场强度提高20%, 同时径向电场得到有效抑制;栅网结构下, 被加速的粒子束在自由漂移空间中的径向发散基本得到抑制;在相同的加速长度下加速H3+粒子, 栅网结构得到的能量增益提高了一倍。     

介质壁直线加速器加速单元间的电路耦合及解耦

中国工程物理研究院流体物理研究所研发的介质壁直线加速器是基于固态脉冲形成线、GaAs光导开关和高梯度绝缘介质壁三项关键技术的新型直线脉冲加速器。在加速器调试阶段,测量出获得加速的质子束流能量远低于预期值,在排除功率源负载能力因素之后,发现脉冲功率源因连接回路引起的电路耦合效应是导致束流能量低的主要原因。基于介质壁直线加速器加速单元放电回路结构的分析,确认了加速单元之间的电路耦合的必然性。并通过测量回路电流,研究了几种不同工作模式下的电路耦合效应。结合电路耦合的特点,给出了两种基于磁芯隔离的解耦方法,并测量了这两种方法的解耦效率。     

维生素C对菲醌三重激发态的淬灭机理及动力学研究

Time-resolved electron spin resonance has been used to study quenching reactions between the antioxidant Vitamin C (VC) and the triplet excited states of 9,10-phenanthrenequinone (PAQ) in ethylene glycol-water (EG-H₂O) homogeneous and inhomogeneous reversed micelle solutions. Reversed micelle solutions were used to be the models of physiological environment of biological cell and tissue. In PAQ/EG-H₂O homogeneous solution, the excited triplet of PAQ (³PAQ*) abstracts hydrogen atom from solvent EG. In PAQ/VC/EG-H₂O solution, ³PAQ* abstracts hydrogen atom not only from solvent EG but also from VC. The quenching rate constant of ³PAQ* by VC is close to the diffusion-controlled value of 1.41×10⁸ L/(mol·s). In hexadecyltrimethylammonium bromide (CTAB)/EG-H₂O and aerosol OT (AOT)/EG-H₂O reversed micelle solutions, ³PAQ* and VC react around the water-oil interface of the reversed micelle. Exit of ³PAQ* from the lipid phase slows down the quenching reaction. For Triton X-100 (TX-100)/EG-H₂O reversed micelle solution, PAQ and VC coexist inside the hydrophilic polyethylene glycol core, and the quenching rate constant of ³PAQ* by VC is larger than those in AOT/EG-H₂O and CTAB/EG-H₂O reversed micelle solutions, even a little larger than that in EG-H₂O homogeneous solution. The strong emissive chemically in-duced dynamic electron polarization of As^- resulted from the effective TM spin polarization transfer in hydrogen abstraction of ³PAQ* from VC.     

Superconductivity of bilayer titanium/indium thin film grown on SiO_2/Si(001)

Bilayer superconducting films with tunable transition temperature(Tc) are a critical ingredient to the fabrication of high-performance transition edge sensors. Commonly chosen materials include Mo/Au, Mo/Cu, Ti/Au, and Ti/Al systems. Here in this work, titanium/indium(Ti/In) bilayer superconducting films are successfully fabricated on SiO_2/Si(001)substrates by molecular beam epitaxy(MBE). The success in the epitaxial growth of indium on titanium is achieved by lowering the substrate temperature to-150?C during indium evaporation. We measure the critical temperature under a bias current of 10 μA, and obtain different superconducting transition temperatures ranging from 645 m K to 2.7 K by adjusting the thickness ratio of Ti/In. Our results demonstrate that the transition temperature decreases as the thickness ratio of Ti/In increases.