Comparison doses of secondary neutron with the heavy ions in a 75-mev/n heavy ion beam

国科图

20—50 MeV O~(5+)离子引起Au的L壳层X射线产生截面研究

在北京13 MV串列加速器上利用20—50MeVO5+离子研究Au的L壳层X射线产生截面.实验结果表明σ(Ll)/σ(Lα),σ(Lβ)/σ(Lα)和σ(Lγ)/σ(Lα)与ECPSSR理论计算结果符合比较好.在实验中由于较高的能量,在能量点存在能移现象.

1.2 MeV/40 mA电子加速器的研制

装置应国内辐照加工需求而研制,采用单相无铁芯变压器结构,初级供以400 Hz的中频交流,次级全波整流倍压后级联形成直流高压。加速管同心地位于次级线圈内,电子枪采用间热式LaB6发射阴极。该装置结构紧凑,电子束1.2 MeV/40 mA,束流功率近50 kW,不稳定度均好于±5%,电功率转化效率高于65%,已通过8 h运行测试。

47 MeV/u ~(12)C与~(133)Cs反应中碘同位素产生截面的Q_(gg)依赖关系

用47 MeV/u 12C离子轰击133Cs靶,应用放射化学分离技术和离线γ射线谱学,得到碘同位素的产生截面。丰中子碘同位素的独立产生截面指数地依赖于Qgg值,而缺中子碘同位素的独立产生截面则偏离这一直线关系。这一事实可对在深部非弹转移过程中产生丰中子碘同位素予以解释。

60 MeV/u~(18)O离子同天然铀反应钡同位素截面的测定

通过60MeV/u18O离子照射天然铀靶产生Ba放射性同位素,使用BaCl2沉淀法从大量铀和其它反应产物混合物中分离出Ba.通过离线γ谱学方法测量了Ba样品的γ射线单谱,根据Ba同位素特征γ射线峰的强度及其它相关数据计算了Ba同位素的生成截面.发现在厚铀靶的情况下,缺中子Ba同位素仍有较高的截面.

MeV离子辐照聚酰亚胺的化学结构及电性能转变

在室温真空条件下,用北京大学离子注入机提供的3 MeV Si~+对厚度大约25μm的电绝缘聚酰亚胺(PI/Kapton)进行了表面改性,通过紫外可见光谱分析(UV/Visible)、傅立叶转换红外光谱分析(FTIR)及电性能测量,研究了不同离子注量(1×10~(12)—1×10~(15)cm~(-2))下注入层中聚酰亚胺各官能团的化学降解及石墨化结构转变机制。红外结果表明,官能团随离子注入量的增加指数降解,并通过实验点的拟合给出了典型分子键的损伤截面。辐照后聚合物的导电性发生了巨大变化,在我们的实验中,聚酰亚胺的面电阻与未辐照样相比下降了近10个数量级,呈现出半导体的电特性。紫外光谱中吸收边缘从紫外到可见区的红移表明了光能隙的逐渐减小,这是由于芳香团尺寸的增加而引起的。

15.14 MeV/u ~(136)Xe离子引起的单粒子效应(英文)

研究了 1 5.1 4MeV/u136 　Xe离子在不同批次的 3 2k× 8bits静态存储器中所引起的单粒子效应 .获得了单粒子翻转和单粒子闭锁截面与入射角度的依赖关系 .将单粒子效应截面与灵敏区中沉积的能量相联系 ,而不是线性能量转移(LET)值 .估计了灵敏体积的深度和死层的厚度 .

30 MeV/u~(40)Ar+~(nat)Ag反应中类弹碎片发射的时-空演化

报道了 ３０ＭｅＶ／ ｕ(４０)Ａｒ＋(ｎａｔ)Ａｇ反应中中等质量碎片（ＩＭＦ）发射时间（τ）随发射源空间大小的演化规律，并对类弹碎片的发射时空进行了讨论．结果表明，ＩＭＦ的发射时标与中等质量碎片关联函数以及发射源的核物质密度（ρ）有关，而与发射源的质量数的关系不大．对于能量较高的类弹碎片来说，在较小的核物质密度下提取的发射时间也较小，因此，在正常核物质密度参数下提取出的发射时间值可作为碎片实际发射时间的上限值．中速碎片的发射时间随密度大小的变化非常缓慢，提取出的发射时间值即可作为实际的发射时间。

Void swelling in MA956 ODS steel irradiated with 122 MeV Ne-ions at elevated temperatures

An investigation of a commercial oxide dispersion-strengthened steel (MA9561) irradiated with high energy Ne-ions to high doses at elevated temperatures is presented. Specimens of MA956 oxide dispersion strengthened steel together with a 9% Cr ferritic/martensitic steel, e.g., Grade 92 steel were irradiated simultaneously with 20Ne-ions (with 122 MeV) to successively increasing damage levels of 1, 5 and 10 dpa at the damage peak at 440 C and 570 C, respectively. Cross-sectional microstructures of the specimens were investigated with transmission electron microscopy. MA956 oxide dispersion strengthened steel showed a higher resistance to void swelling especially to void growth at the grain boundaries than the ferritic/martensitic steel, e.g., Grade 92 steel did, and thus exhibited a prominence for an application in the situation of a high He production at high temperatures. The suppression of the growth of voids especially at the grain boundaries in MA956 is ascribed to an enhanced recombination of the point defects and a trapping of Ne atoms at the interfaces of the yttrium–aluminum oxide particles and the matrix.

Quasi-Elastic Scattering of C-16 from C-12 at 47.5 MeV/Nucleon

Differential cross sections for the quasi-elastic scattering of C-16 at 47.5 MeV/nucleon from C-12 target are measured. Coupled-channels calculations are carried out and the optical potential parameters are obtained by fitting the experimental angular distribution.

Modification of Fe/Cu Multilayers under 2-MeV Xe20+ Irradiation

Multilayers with a structure of Si/[Fe(10 nm)/CU(10 nm)](5) were deposited on Si(100) substrates and then irradiated at room temperature by using 2-MeV Xe20+. The modifications of the multilayers were characterized using a depth profile analysis of the Auger electron spectroscopy (AES) data and the evolution of crystallite structures of the multilayers were analyzed by using X-ray diffraction (XRD). The AES depth profiles indicated that de-mixing of the Fe and the Cu layers was observed at low ion fluences, but inter-mixing of the Fe and the Cu layers was found at high ion fluences and destroyed the layered structure of the multilayers. The obtained XRD patterns showed that, after irradiation by 2-MeV Xe20+ at; 2 x 10(16) ions/cm(2), the peaks of the multilayers related to a Cu-based fee solid solution and an Fe-based bee solid solution phase became visible, which implied that the inter-mixing at the Fe/Cu interface resulted in the formation of new phases. A possible mechanism of modification in the Fe/Cu multilayers induced by ion irradiation is briefly discussed.

Effect of 80.55 MeV/u(12)C(6+) ions on radiosensitivity and cell cycle of human hepatoma cell lines

In this paper, the relationship between radiosensitivity, cell cycle alteration and the change of apoptosis in different human hepatoma cell lines irradiated by heavy ions were studied with the aim of building up the base data for clinical therapy. Exponentially growing hepatoma cell lines were irradiated by 80.55 MeV/u(12)C(6+) ions at a dose of 0 Gy, 0.5 Gy, 1 Gy, 2 Gy, 4 Gy and 8 Gy. The radiosensitivity was assessed by means of the colony-forming assay. The DNA content, the percentage of each cell-cycle phase and the apoptosis rate were obtained with flow cytometry methods. After the irradiation, the SF2 (survival fraction at 2 gray) of SMMC-7721 cells were evidently lower than that of HepG2 cells. The S phase arrest, G2/M phase arrest delay and the apoptosis in the two hepatoma cell lines varied with the increase of the dose and repair time. The heavy ions could obviously kill the human hepatoma cell lines. Compared to HepG2 cells, SMMC-7721 cells were more radiosensitive to C-12(6+) ions.

Production cross-section of Ra-230 in the reaction of 60 MeV/u O-18 ions with U-238

A thick natural uranium target was bombarded with a 60 MeV/u O-18 beam. The neutron-rich isotope Ra-230 as the target residue was produced through the multinucleon transfer reaction (U-238-4p-4n). The barium and radium fraction as BaCl2 precipitate were radiochemically separated first from the mixture of uranium and reaction products. Then, the radium fraction was separated from BaCl2 precipitate by using cation exchange technique. The gamma-ray spectra of the Ra fraction were measured using an HPGe detector. The production cross sections of Ra-230 were obtained by a combination of the radiochemical separation technique and off-line gamma-ray spectroscopy. The cross section of Ra-230 has been determined to be 66 +/- 20 mu b.