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EM Design of a f =325 MHz, =0:52 Double Spoke Superconducting Cavity
No full text中国科学院近代物理研究所设计的工作频率为325 MHz、最优为0.52的双柱超导Spoke 腔的电磁已经完成。详细地描述了Spoke 基部横截面形状和大小对腔体射频性能的影响,采用了跑道形来取代通常的圆形Spoke 基部截面。从归一化峰值电磁场和分路阻抗两方面出发,比较了横截面为横向跑道和纵向跑道的Spoke 基部。Spoke 基部横截面的形状为横向跑道时能得到较好的射频参数,满足中国ADS(C-ADS)的工程需求。最后利用CST 粒子工作室对得到的腔体进行了二次电子倍增分析,在工作电压附近不存在二次电子倍增,验证了该腔体形状的可行性。<span style="color: rgb(51, 51, 51); font-family: arial, helvetica, sans-serif; font-size: 13px; line-height: 22px; background-color: rgb(248, 248, 248);">The EM design of a 325 MHz beta = 0.52 superconducting double Spoke cavity has been finished at Institute of Modern Physics (IMP), Chinese Academy of Sciences(CAS). In this paper, the optimization of the Spoke base is described in detail. The goal is to minimize the peak surface field and maximize the shunt impedance. The common cylinder is replaced by the racetrack shape for the Spoke base. The transverse racetrack Spoke base can offer a better RF property than the longitudinal racetrack Spoke base, which meet the requirement of the C-ADS. The simulation of multipactor finished by CST Particle Studio is also presented, which gives a promising result that there is no multipactor around working voltage.</span
Study of a High-Yield Cellulase System Created by Heavy-Ion Irradiation-Induced Mutagenesis of Aspergillus niger and Mixed Fermentation with Trichoderma reesei
No full text<span style="color: rgb(51, 51, 51); font-family: arial, helvetica, sans-serif; font-size: 13px; line-height: 22px; background-color: rgb(248, 248, 248);">The aim of this study was to evaluate and validate the efficiency of C-12(6+) irradiation of Aspergillus niger (A. niger) or mutagenesis via mixed Trichoderma viride (T. viride) culturing as well as a liquid cultivation method for cellulase production via mixed Trichoderma reesei (T. reesei) and A. niger culture fermentation. The first mutagenesis approach was employed to optimize yield from a cellulase-producing strain via heavy-ion mutagenesis and high-throughput screening, and the second was to effectively achieve enzymatic hydrolysis of cellulase from a mixed culture of mutant T. viride and A. niger. We found that C-12(6+)-ion irradiation induced changes in cellulase biosynthesis in A. niger but had no effect on the time course of the synthesis. It is notable that the exoglucanases (CBH) activities of A. niger strains H11-1 and H differed (6.71 U/mL vs. 6.01 U/mL) and were significantly higher than that of A. niger mutant H3-1. Compared with strain H, the filter paper assay (FPA), endoglucanase (EG) and beta-glucosidase (BGL) activities of mutant strain H11-1 were increased by 250.26%, 30.26% and 34.91%, respectively. A mixed culture system was successfully optimized, and the best ratio of T. reesei to A. niger was 5: 1 for 96 h with simultaneous inoculation. The BGL activity of the mixed culture increased after 72 h. At 96 h, the FPA and BGL activities of the mixed culture were 689.00 and 797.15 U/mL, respectively, significantly higher than those of monocultures, which were 408.70 and 646.98 U/mL for T. reesei and 447.29 and 658.89 U/mL for A. niger, respectively. The EG activity of the mixed culture was 2342.81 U/mL, a value that was significantly higher than that of monocultures at 2206.57 U/mL for T. reesei and 1727.62 U/mL for A. niger. In summary, cellulose production and hydrolysis yields were significantly enhanced by the proposed combination scheme.</span
First isochronous mass measurements with two time-of-flight detectors at CSRe
No full text<span style="color: rgb(51, 51, 51); font-family: arial, helvetica, sans-serif; font-size: 13px; line-height: 22px; background-color: rgb(248, 248, 248);">Isochronous mass spectrometry (IMS) established in heavy-ion storage rings has proven to be a powerful tool for mass measurements of short-lived nuclides. In IMS, the revolution times of stored ions should be independent of their velocity spread. However, this isochronous condition is fulfilled only in the first order and in a small range of revolution times. To correct for non-isochronicity, an additional measure of the velocity or magnetic rigidity of each stored ion is required. For this purpose two new time-of-flight (TOF) detectors were installed in one of the straight sections of the experimental cooler storage ring in Lanzhou. It is expected that the resolving power of the IMS will significantly be improved with such a double-TOF arrangement. The double-TOF system was tested in a recent experiment with the Kr-78 fragments. Some of the experimental results are presented in this contribution.</span
Collective effects on the wakefield and stopping power of an ion beam pulse in plasmas
No full text<span style="color: rgb(51, 51, 51); font-family: arial, helvetica, sans-serif; font-size: 13px; line-height: 22px; background-color: rgb(248, 248, 248);">A two-dimensional (2D) particle-in-cell simulation is carried out to study the collective effects on the wakefield and stopping power for a hydrogen ion beam pulse propagation in hydrogen plasmas. The dependence of collective effects on the beam velocity and density is obtained and discussed. For the beam velocity, it is found that the collective effects have the strongest impact on the wakefield as well as the stopping power in the case of the intermediate beam velocities, in which the stopping power is also the largest. For the beam density, it is found that at low beam densities, the collective contribution to the stopping power increase linearly with the increase of the beam density, which corresponds well to the results calculated using the dielectric theory. However, at high beam densities, our results show that after reaching a maximum value, the collective contribution to the stopping power starts to decrease significantly with the increase of the beam density. Besides, at high beam densities, the wakefield loses typical V-shaped cone structures, and the wavelength of the oscillation wakefield increases as the beam density increases. (C) 2015 AIP Publishing LLC.</span
Reconstructed primary fragments and symmetry energy, temperature and density of the fragmenting source in Zn-64+Sn-112 at 40 MeV/nucleon
No full text<span style="color: rgb(51, 51, 51); font-family: arial, helvetica, sans-serif; font-size: 13px; line-height: 22px; background-color: rgb(248, 248, 248);">Symmetry energy, temperature and density at the time of the intermediate mass fragment formation are determined in a self-consistent manner, using the experimentally reconstructed primary hot isotope yields and anti-symmetrized molecular dynamics (AMD) simulations. The yields of primary hot fragments are experimentally reconstructed for multifragmentation events in the reaction system Zn-64 + Sn-112 at 40 MeV/nucleon. Using the reconstructed hot isotope yields and an improved method, based on the modified Fisher model, symmetry energy values relative to the apparent temperature, a(sym)/T, are extracted. The extracted values are compared with those of the AMD simulations, extracted in the same way as those for the experiment, with the Gogny interaction with three different density-dependent symmetry energy terms. The a(sym)/T values change according to the density-dependent symmetry energy terms used. Using this relation, the density of the fragmenting system is extracted first. Then symmetry energy and apparent temperature are determined in a self consistent manner in the AMD model simulations. Comparing the calculated a(sym)/T values and those of the experimental values from the reconstructed yields, rho/rho 0 = 0.65 +/- 0.02, a(sym) = 23.1 +/- 0.6 MeV and T = 5.0 +/- 0.4 MeV are evaluated for the fragmenting system experimentally observed in the reaction studied. (C) 2014 Elsevier B.V. All rights reserved.</span
Hillock formation on CaF2, A12O3, c-SiO2and MgO single crystal surfaces by ion impact - From potential energy deposition to electronic energy loss
No full text<span style="color: rgb(51, 51, 51); font-family: arial, helvetica, sans-serif; font-size: 13px; line-height: 22px; background-color: rgb(248, 248, 248);">For impact of very slow highly charged ions on single crystal surfaces the appearance of hillocks can be linked to a threshold in potential energy while for swift heavy ions a minimum electronic energy loss per unit length is necessary. Recent investigations on CaF2 in the medium energy range bridge the gap between these two extreme cases. These investigations are now extended to other target materials.</span
低温超导组件的标定与准直测量
No full text<span id="ChDivSummary" name="ChDivSummary">Cry Module由于其无法通视和超低温特性,是超导直线加速器准直中的重点与难点。文中提出由激光跟踪仪和测微准直望远镜协同准直冷质量组件。作者设计了测微准直望远镜所用十字丝目标及其支架,而且成功安装低温超导组件,监测了两次低温实验时的位移。常温安装精度达到0.15mm,低温监测精度达到0.5mmm。目前ADS-Cry Module已通过中期检查验收,成功引出能量2.68Me V、最大流强3.6m A的连续波质子束,束流功率达到9.6k W,是目前国际上连续束运行的超导质子直线加速器中束流功率最高的,也是我国首次实现超导高频腔加速毫安级连续波质子束。这标志着我国强流质子超导直线加速器技术进入国际先进行列。</span
Defect production and deuterium retention in quasi-homogeneously damaged tungsten
No full textTo understand the deuterium (D) bulk retention behavior in plasma facing materials under reactor-relevant conditions, tungsten (W) foils were irradiated with 122 MeV 20Ne ions and then exposed to D 2 gas at 773 K. A quasi-homogeneous distribution of atomic displacement damage to 0.3 dpa within a depth of 50 mum was produced in W using an energy degrader in the irradiation chamber. Results of positron annihilation lifetime spectroscopy showed a long positron lifetime component of ~400 ps appeared after irradiation, indicating the formation of vacancy clusters with up to 12 vacancies in W. Thermal desorption spectra showed a broad D desorption temperature range (730-1173 K) with a high release peak at ~1010 K for the irradiated W specimens. The amounts of D retained in the irradiated W were significantly larger than the annealed ones, which could be attributed to the trapping effects of the vacancy clusters formed by cascade collisions and the clustering of mono-vacancies. [All rights reserved Elsevier]