Institutional Repository of Institute of Modern Physics, CAS
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非对称磁聚焦结构的同步加速器
No full text 本发明涉及一种带电粒子同步加速器磁聚焦结构的设计方法技术领域，尤其是涉及一种非对称磁聚焦结构的同步加速器。包括有引入切割磁铁装置(9)、脉冲注入磁铁(6)、内靶装置(4)、电子冷却装置(5)、高频加速装置(10)、八个同步加速器弯曲段(1-1至1-8)和八个同步加速器直线段(2-1至2-8)。其通过一个带电粒子运行在其中的环形真空管道，以及布置在环形管道上的磁铁元件、加速元件、束流诊断元件、注入引出元件和实验平台。有效的利用同步加速器空间，安装尽可能多的核物理、原子物理实验平台，最大限度的降低制造成本和安装体积
高能电子辐照诱导GaN异质结应变弛豫机制的研究
No full text<span id="ChDivSummary" name="ChDivSummary">利用能量为2 MeV的高能电子束对金属有机物化学气相沉积方法(MOCVD)生长的非故意掺杂氮化镓(GaN)异质结在室温下进行辐照,辐照剂量分别为1×1015/cm2和5×1015/cm2。经垂直于样品表面的电子辐照后,GaN外延层的(0004)和(10ī2)高分辨X射线衍射峰分别向高角和低角发生移动,表明电子辐照使GaN外延层发生了部分应变弛豫。利用电子背散射衍射(EBSD)对应变弛豫进行了表征。EBSD结果显示,剂量为5×1015/cm2的电子辐照相对于1×1015/cm2的电子辐照可诱导GaN外延层发生更为显著的应变弛豫。卢瑟福背散射/沟道(RBS/C)实验结果表明,5×1015/cm2的电子辐照对GaN外延层引入更为严重的辐照损伤。上述实验结果表明,GaN外延层的应变弛豫与2 MeV的电子辐照引入的缺陷如弗伦克尔对有关。运用弹性原子链模型(EACM)对电子辐照诱导GaN外延层应变弛豫机制进行了讨论。</span
Non-randomized mtDNA damage after ionizing radiation via charge transport
No full textAlthough it is well known that there are mutation hot spots in mtDNA, whether there are damage hot spots remain elusive. In this study, the regional DNA damage of mitochondrial genome after ionizing radiation was determined by real-time quantitative PCR. The mtDNA damage level was found to be dose-dependent and regional unequal. The control region was the most susceptible region to oxidative damage. GGG, as an typical hole trap during charge transport, was found to be disproportionally enriched in the control region. A total of 107 vertebrate mitochondrial genomes were then analyzed to testify whether the GGG enrichment in control region was evolutionary conserved. Surprisingly, the triple G enrichment can be observed in most of the homeothermal animals, while the majority of heterothermic animals showed no triple G enrichment. These results indicated that the triple G enrichment in control region was related to the mitochondrial metabolism during evolution
Experimental measurement of the correlation between CT number and heavy ion range
No full textFor precision delivery of the Bragg peak of a heavy-ion beam to a target volume in ion beam therapy, it is necessary to know the tissue stopping power. A general approach to solve this problem in ion beam therapy is to convert X-ray CT (computed tomography) numbers into water-equivalent path length (WEPL) coefficients using a CT-WEPL calibration curve for all voxels traversed by the beam. This work aims at establishing a CT-WEPL coefficient calibration curve for the heavy ion therapy project at IMP, so as to compute the range of carbon ion beams in tissues easily according to the patient CT data. Several tissue-equivalent materials were applied to measure their WEPL coefficients using a high-energy carbon ion beam in this work. A CT-WEPL calibration curve was obtained through fitting the measured data, which can be used directly for dose optimization and facilitates the design of patient treatment plans significantly at IMP
Design of a superconducting magnet for CADS
No full textThis paper describes a superconducting magnet system for the China Accelerator Driven System (CADS). The magnetic field is provided by one main, two bucking and four racetrack coils. The main coil produces a central field of up to 7 T and the effective length is more than 140 mm, the two bucking coils can shield most of the fringe field, and the four racetrack superconducting coils produce the steering magnetic field. Its leakage field in the cavity zone is about 5 x 10(-5) T when the shielding material Niobium and cryogenic permalloy are used as the Meissner shielding and passive shielding respectively. The quench calculations and protection system are also discussed
X-ray emission induced by 1.2-3.6 MeV Kr13+ ions
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);">X-ray emission from Kr13+ ions in the energy range 1.2-3.6 MeV in steps of 0.6 MeV impacting on an Au target was investigated on electron cyclotron resonance ion source at the Heavy Ion Research Facility in Lanzhou. It was found that a shift of the X-ray lines to the higher energy side occurred. We measured the relationship between the characteristic of X-ray yield of Au M X-rays and Kr L X-rays as a function of incident energy. Furthermore, M-shell X-ray production cross-section of Au induced by Kr13+ was measured. The measured cross-section of target is compared to the classical binary-encounter approximation and plane-wave-born approximation theoretical model, which is a significant different between experimental and theoretical model.</span
A new low-energy radioactive beam line for nuclear astrophysics studies in China
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 gas-target system has been newly developed and installed at a Radioactive Ion Beam Line in Lanzhou (RIBLL), which makes RIBLL capable of delivering intense, low-energy RIBs for nuclear astrophysics studies. A 1.7 x 10(4)-pps intensity Na-22 RI beam has been achieved in a commissioning run. With further improvements, a 10(5)-pps intensity of some RI beams with mass A < 30 (close to the line of beta-stability) can be expected in the near future. Some detection equipment including Germanium and Silicon arrays (or balls) available (or to be constructed) at IMP are briefly introduced. A new low-energy radioactive beam line in China is now ready for nuclear astrophysics studies. (C) 2012 Elsevier B.V. All rights reserved.</span
Mass measurements of the neutron-deficient Ti41, Cr45, Fe49, and Ni53 nuclides: First test of the isobaric multiplet mass equation in fp-shell nuclei
No full text<span style="color: rgb(0, 0, 0); font-family: Arial, verdana, helvetica, sans-serif; line-height: 14px;">Isochronous mass spectrometry has been applied to neutron-deficient Ni58 projectile fragments at the HIRFL-CSR facility in Lanzhou, China. Masses of a series of short-lived T</span><inf style="color: rgb(0, 0, 0); font-family: Arial, verdana, helvetica, sans-serif; line-height: 14px;">z</inf><span style="color: rgb(0, 0, 0); font-family: Arial, verdana, helvetica, sans-serif; line-height: 14px;">=-3/2 nuclides including Ti41, Cr45, Fe49, and Ni53 have been measured with a precision of 20-40keV. The new data enable us to test for the first time the isobaric multiplet mass equation (IMME) in fp-shell nuclei. We observe that the IMME is inconsistent with the generally accepted quadratic form for the A=53, T=3/2 quartet. We perform full space shell model calculations and compare them with the new experimental results. © 2012 American Physical Society.(39 refs)</span
Electric field simulation and measurement of a pulse line ion accelerator
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);">An oil dielectric helical pulse line to demonstrate the principles of a Pulse Line Ion Accelerator (PLIA) has been designed and fabricated. The simulation of the axial electric field of an accelerator with CST code has been completed and the simulation results show complete agreement with the theoretical calculations. To fully understand the real value of the electric field excited from the helical line in PLIA, an optical electric integrated electric field measurement system was adopted. The measurement result shows that the real magnitude of axial electric field is smaller than that calculated, probably due to the actual pitch of the resister column which is much less than that of helix.</span
Injector and beam transport simulation study of proton dielectric wall accelerator
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 simulation study of a short-pulsed proton injector for, and beam transport in, a dielectric wall accelerator (DWA) has been carried out using the particle-in-cell (PIC) code Warp. It was shown that applying "tilt pulse" voltage waveforms on three electrodes enables the production of a shorter bunch by the injector. The fields in the DWA beam tube were simulated using Computer Simulation Technology's Microwave Studio (CST MWS) package, with various choices for the boundary conditions. For acceleration in the DWA, the beam transport was simulated with Warp, using applied fields obtained by running CST MWS. Our simulations showed that the electric field at the entrance to the DWA represents a challenging issue for the beam transport. We thus simulated a configuration with a mesh at the entrance of the DWA, intended to improve the entrance field. In these latter simulations, a proton bunch was successfully accelerated from 130 key to about 36 MeV in a DWA with a length of 36.75 cm. As the beam bunch progresses, its transverse dimensions diminish from (roughly) 0.5 x 0.5 cm to 0.2 x 0.4 cm. The beam pulse lengthens from 1 cm to 2 cm due to lack of longitudinal compression fields. (C) 2012 Elsevier B.V. All rights reserved.</span