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The dependence of radiation enhancement effect on the concentration of gold nanoparticles exposed to low- and high-LET radiations
No full textWe examined the dependence of hydroxyl radical production on the concentration of 15 nm citrate-capped AuNPs and dose using coumarin-3-carboxylic acid in phosphate buffered saline (PBS), and investigated the radiosensitisation of different concentration AuNPs on human cervix carcinoma HeLa cells through clonogenic survival assay for X-rays and carbon ions. The enhancement factor of AuNPs for hydroxyl radical production reached a maximum 3.66 for X-rays at the concentration of 0.1 mg/mL while the maximum was 5.52 for carbon ions in presence of 1.0 mu g/mL AuNPs in PBS. At 50% survival level, the sensitizer enhancement ratios of X-rays and carbon ions varied from 1.14 to 2.88 and from 1.27 to 1.44, respectively, when cells were co-cultured with 1.5-15.0 mu g/mL AuNPs. Our data indicate AuNPs showed radiosensitisation in terms of hydroxyl radical production and cell killing for low- and high-LET radiations. The concentration of AuNPs in PBS and cells played an important role in radiosensitizing effect. Based on the fact-the AuNPs in PBS could improve the production of hydroxyl radical and no accumulation of cells in the G(2)/M phase was observed, we deduce that the increment of hydroxyl radical production with AuNPs provided a mechanism for radiosensitisation. (C) 2015 Associazione Italiana di Fisica Medica. Published by Elsevier Ltd. All rights reserved
Beam Dynamics Simulation and Research of SSC-LINAC Heavy Ion RFQ
No full text采用多粒子跟踪程序BEAMPATH 对SSC-LINAC 重离子RFQ 直线加速器进行动力学模拟,分别对RFQ 的接受度、高频特性、束流稳定性、空间电荷效应等进行了分析。该RFQ具有很大的纵向接受度,有利于束流在RFQ中的传输;高频特性研究表明,翼间电压设定在理论值以上时,该RFQ都能保持较好的束流特性;束流稳定性分析结果表明,该RFQ具有很大的束流失配容忍度;空间电荷效应研究表明,当束流强度低于0.5 mA时,束流传输不受影响。综合研究结果表明,53.667 MHz重离子RFQ具有较好的动力学特性,满足SSC-LINAC直线加速器的设计要求。The RFQ beam dynamics of a heavy ion linac was investigated in this paper and the BEAMPATH code was employed in this study. The main research was focused on the beam performances depending on longitudinal acceptance, RF properties, beam instability and space charge effect. The RFQ has large longitudinal acceptance in design, which brings the beam performances well. In the RF parameter study, the beam can keep good transmission in the acceleration even the vane voltage is larger than the theoretical value. It is also shown that the RFQ has a large robustness for the mismatch of the input beam by the analysis of the beam instability. Furthermore, the beam evolution is independent on the space charge effect when the beam current is less than 0.5 em A. The preliminary analysis of the beam dynamics shows that the 53.667 MHz heavy ion RFQ has a promising performance, which meets the requirements of SSC-LINAC.国家自然科学基金创新研究群体科学基金; 国家重点基础研究发展计划(973计划)项
Double-peak structures in transmission of H-2(+) ions through conical multicapillaries in a polymer: Projectile-energy dependence
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);">Transmission experiments of 7-200 keV H-2(+) ions through conical multicapillaries with inlet or outlet diameters of 4/2 mu m and a length of 30 mu m etched in a PC polymer are reported. The yield of the transmitted particles as a function of the capillary tilt angle was measured. The results show that for 200 keV H-2(+) ions the guiding effect disappears but a focusing effect is obtained with a density enhancement factor of 3.5. For 7-50 keV H-2(+) ions their transmitted particle curves exhibit a pair of shoulder peaks on the left-and right-hand side of the center angle 0 degrees. As the ion energy increases, the shoulder-peak structure is found to vanish leaving one peak at 0 degrees.</span
激光离子源双脉冲打靶方案的实现
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);">设计并实现了近代物理研究所激光离子源双脉冲打靶方案以产生高电荷态离子束。从Nd:YAG激光器输出的激光束经过一对分光棱镜的分束-合束,通过改变两束光的光程差,得到有一定时间延迟的双激光脉冲。利用四分之一玻片,双脉冲的能量比值可以在3:8~8:3之间连续调节。为了验证该方案的可行性,对C靶进行了初步实验。实验结果发现,与以往单脉冲打靶方案对比,双脉冲方案在离子束的脉冲时间结构和电荷态分布有所不同。但是,导致这些差异的机理和实验的优化还尚需要进一步研究。</span><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 double-pulse laser irradiating scheme has been designed and established for the production of highly charged ion beams at Institute of Modern Physics (IMP), Chinese Academy of Sciences. The laser beam output by a Nd:YAG laser is split and combined by a double of beam splitters, between which the split laser beams are transmitted along different optical paths to get certain time delay between each other. With the help of a quarter-wave plate before the first splitter, the energy ratio between the two laser pulses can be adjusted between 3:8 to 8:3. To testify its feasibility, a preliminary experiment was carried out with the new-developed double-pulse irradiating scheme to produce highly charged carbon ions. Comparing the results with those got from the previous single-pulse irradiating scheme, the differences in the time structure and Charge State Distribution (CSD)of the ion pulse were observed, but its mechanisms and optimization require further studies.</span
