520 resultados para intermediate energy heavy-ion beam


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用能量11.4MeV/u和注量1×108ions/cm2的197Au离子垂直辐照聚丙烯薄膜,通过电导测量法监测温度、硫酸浓度和重铬酸钾浓度对径迹蚀刻速率的影响,得到合适的蚀刻条件;成功制备出孔径范围在600—1000nm的重离子径迹聚丙烯孔膜,并用场发射扫描电镜对孔的形状及孔径大小进行了表征,对孔洞锥角的形成进行了分析,为重离子辐照技术制备锂离子电池隔膜提供了实验数据。

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介绍了中国科学院近代物理研究所重离子治癌装置的安装定位测量技术和方法。利用激光跟踪仪通过控制网的建立,和多重坐标系的转换,使最后的磁铁安装径向相对误差不超过±(0.05-0.1)mm,真空管道的横向及竖向精度也达到了±(0.1-0.2)mm。

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主环二极铁电源是兰州重离子加速器冷却储存环(HIRFL-CSR)工程的关键设备和指标要求最高的一台电源,采用了独特的拓扑和控制策略。为满足峰值功率3.15MW(3kA,1.45kV)的输出能力和快脉冲要求,采用了晶闸管整流并联脉宽调制补偿单元的主电路拓扑结构和特殊的控制方式,这套综合方案确保电源满足了全部技术指标。本文介绍了该拓扑结构的原理和优势,讨论了为满足±2×10-4的跟踪误差的要求而采用的控制拓扑和双基准给定的原理,并简介了调试过程和近年来的运行和改进情况。

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中国科学院近代物理研究所基于兰州重离子研究装置(HIRFL/HIRFL-CSR),在被动型束流配送系统下采用二维分层适形照射治疗技术开展重离子治癌临床试验研究。为了更好地利用重离子束在肿瘤放射治疗中的生物物理优势并保障重离子临床治疗试验的顺利实施,一个初级版本的重离子治疗计划系统已经设计完成。此计划系统是针对被动型束流配送系统下的二维分层适形照射治疗方式来进行设计的。介绍了此系统的设计框架、可提供的功能以及利用宽束算法进行剂量计算在此系统中的实现。通过人体仿真体模实验证实由该治疗计划系统给出的靶区计划剂量与实测剂量的偏差在5%之内。最后讨论了设计较为完备的重离子治疗计划系统仍需解决的问题。

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选用12C6+离子辐照诱变阿维菌素B1a产生菌ZJAV-A1,研究其诱变效应。实验结果表明,12C6+离子辐照剂量50Gy时致死率97%,正突变率最高可达到34.2%。通过12C6+离子诱变处理,结合平板培养基及斜面培养基的正突变菌株筛选,最终获得一株稳定性良好,阿维菌素B1a组分产量稳定在4460—4588μg/ml之间,较出发菌株提高11.1%—14.7%的突变株ZJAV-Y1-203。

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Yeast strain Saccharornyces cerevisiae was irradiated with different doses of 85 MeV/u Ne-20(10+) to investigate DNA damage induced by heavy ion beam in eukaryotic microorganism. The survival rate, DNA double strand breaks (DSBs) and DNA polymorphic were tested after irradiation. The results showed that there were substantial differences in DNA between the control and irradiated samples. At the dose of 40 Cy, the yeast cell survival rate approached 50%, DNA double-strand breaks were barely detectable, and significant DNA polymorphism was observed. The alcohol dehydrogenase II gene was amplified and sequenced. It was observed that base changes in the mutant were mainly transversions of T-->G and T-->C. It can be concluded that heavy ion beam irradiation can lead to change in single gene and may be an effective way to induce mutation.

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Within the framework of the improved isospin-dependent quantum molecular dynamics (ImIQMD) model, the dynamics of strangeness (K-0,K-+, Lambda, and Sigma(-,0,+)) production in heavy-ion collisions near threshold energies is investigated systematically, with the strange particles considered to be produced mainly by inelastic collisions of baryon-baryon and pion-baryon. Collisions in the region of suprasaturation densities of the dense baryonic matter formed in heavy-ion collisions dominate the yields of strangeness production. Total multiplicities as functions of incident energies and collision centralities are calculated with the Skyrme parameter SLy6. The excitation function of strangeness production is analyzed and also compared with the KaoS data for K+ production in the reactions C-12 + C-12 and Au-197 + Au-197.

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Parity (P)-odd domains, corresponding to nontrivial topological solutions of the QCD vacuum, might be created during relativistic heavy-ion collisions. These domains are predicted to lead to charge separation of quarks along the orbital momentum of the system created in noncentral collisions. To study this effect, we investigate a three-particle mixed-harmonics azimuthal correlator which is a P-even observable, but directly sensitive to the charge-separation effect. We report measurements of this observable using the STAR detector in Au + Au and Cu + Cu collisions at root s(NN) = 200 and 62 GeV. The results are presented as a function of collision centrality, particle separation in rapidity, and particle transverse momentum. A signal consistent with several of the theoretical expectations is detected in all four data sets. We compare our results to the predictions of existing event generators and discuss in detail possible contributions from other effects that are not related to P violation.

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利用100MeV/u的12C6+离子束辐照酵母Saccharomyces cerevsiea YY,选育出一株高产突变菌株C03A,考察C03A发酵过程中不同温度、pH、糖汁浓度对发酵的影响。通过正交实验确定最佳发酵条件为:糖汁浓度24%、温度35℃、pH5.0。在10L发酵罐实验中,C03A发酵速率相对原始菌株高,36h发酵完全,比原始菌株缩短12h;发酵产酒率达到13.2%(V/V),比原始菌株高1.6%(V/V)。

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Superconducting electron cyclotron resonance ion source with advance design in Lanzhou (SECRAL) is an 18-28 GHz fully superconducting electron cyclotron resonance (ECR) ion source dedicated for highly charged heavy ion beam production. SECRAL, with an innovative superconducting magnet structure of solenoid-inside-sextupole and at lower frequency and lower rf power operation, may open a new way for developing compact and reliable high performance superconducting ECR ion source. One of the recent highlights achieved at SECRAL is that some new record beam currents for very high charge states were produced by 18 GHz or 18+14.5 GHz double frequency heating, such as 1 e mu A of Xe-129(43+), 22 e mu A of Bi-209(41+), and 1.5 e mu A of Bi-209(50+). To further enhance the performance of SECRAL, a 24 GHz/7 kW gyrotron microwave generator was installed and SECRAL was tested at 24 GHz. Some promising and exciting results at 24 GHz with new record highly charged ion beam intensities were produced, such as 455 e mu A of Xe-129(27+) and 152 e mu A of Xe-129(30+), although the commissioning time was limited within 3-4 weeks and rf power only 3-4 kW. Bremsstrahlung measurements at 24 GHz show that x-ray is much stronger with higher rf frequency, higher rf power. and higher minimum mirror magnetic field (minimum B). Preliminary emittance measurements indicate that SECRAL emittance at 24 GHz is slightly higher that at 18 GHz. SECRAL has been put into routine operation at 18 GHz for heavy ion research facility in Lanzhou (HIRFL) accelerator complex since May 2007. The total operation beam time from SECRAL for HIRFL accelerator has been more than 2000 h, and Xe-129(27+), Kr-78(19+), Bi-209(31+), and Ni-58(19+) beams were delivered. All of these new developments, the latest results, and long-term operation for the accelerator have again demonstrated that SECRAL is one of the best in the performance of ECR ion source for highly charged heavy ion beam production. Finally the future development of SECRAL will be presented.

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Correlation analysis of the standard Gibbs energy for a series of tetraalkylammonium ions, protonated substituted ethylenediamine derivatives and protonated aromatic amine derivatives using three new topological indices Ax1, Ax2 and Ax has been studied. T

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A stoichiometric Gd2O3-x thin film has been grown on a silicon (10 0) substrate with a low-energy dual ion-beam epitaxial technique. Gd2O3-x shares Gd2O3 structures although there are many oxygen deficiencies in the film. The photoluminescence (PL) measurements have been performed in a temperature range 5-300 K. The detailed characters of the peak position, the full-width at half-maximum (FWHM) and the peak intensity at different temperature were reported. An anomalous intensity behavior of the PL spectra has been observed, which is similar to that of some other materials such as porous silicon and silicon nanocrystals in silicon dioxide. Therefore, we suggest that the nanoclusters with the oxygen deficiencies contribute to the PL emission and employ the model of singlet-triplet exchange splitting of exciton to discuss the four peaks observed in the experiment. (C) 2003 Elsevier B.V. All rights reserved.

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Stoichiometric gadolinium oxide thin films have been grown on silicon (100) substrates with a low-energy dual ion-beam epitaxial technique. Gadolinium oxide shares Gd2O3 structures although the ratio of gadolinium and oxygen in the film is about 2:1 and a lot of oxygen deficiencies exist. Photoluminescence (PL) measurements have been carried out within a temperature range of 5-300 K. The detailed characters of the PL emission integrated intensity, peak position, and peak width at different temperature were reported and an anomalous photoluminescence behavior was observed. The character of PL emission integrated intensity is similar to that of some other materials such as porous silicon and silicon nanocrystals in silicon dioxide. Four peaks relative to alpha band and beta band were observed also. Therefore we suggest that the nanoclusters with the oxygen deficiencies contribute to the PL emission and the model of singlet-triplet exchange splitting of exciton was employed for discussion. (C) 2003 American Institute of Physics.

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The magnetic semiconductor GdxSi1-x was prepared by low-energy dual ion-beam epitaxy. GdxSi1-x shows excellent magnetic properties at room temperature. A high magnetic moment of 10 mu(B) per Gd atom is observed. The high atomic magnetic moment is interpreted as being a result of the RKKY mechanism. The indirect exchange interaction between ions is strong at large distances due to the low state density of the carriers in the magnetic semiconductor.