快重离子在高分子材料中的强电子激发效应研究

本文简要介绍了快重离子在固体材料，特别是在高分子材料和团簇材料中引起强电子激发效应研究的发展历史、研究现状和基本理论。重点描述了在兰州重离子加速器（HIRFL）上完成的2.1 GeV Kr离子辐照聚碳酸酷CPC）膜的实验和辐照样品的傅立叶变换红外光谱（FTIR )和紫外／可见光谱(UVIVIS )分析。FTIR分析结果表明，高能Kr离子在PC膜中引起的辐照效应主要是键的断裂和材料的降解。随着电子能损和辐照剂量的增大，材料逐渐碳化，同时有炔基生成。在UVNIS中，380, 450, 500nm波长处的吸光度之差（A－A_0）与剂量近似成线性关系，与电子能损呈确定的指数关系（指数分别为1.69,1.86和2.02）；与电子能量沉积密度也近似成指数关系。描述了在HIRFL上完成的2.0GeV Xe离子辐照C_(60)薄膜的实验和辐照样品的FTIR谱、拉曼谱(Raman)和X射线衍射谱（XRD）分析。分析结果表明：2.0 GeV Xe离子辐照C60薄膜引起的损伤过程主要取决于强电子激发，在特定电子能损处，损伤的部分恢复是由于强电子激发的退火效应引起的。快重离子辐照产生的物理化学改性不仅与离子的电子能损有关，还与离子的速度有关。在同样的电子能损下，速度越小，产生的效应就越明显。

利用HIRFL评估半导体器件单粒子效应敏感度的研究

用55MeV/u的~(40)Ar，离子对国内第一台专用的单粒子效应加速器模拟实验装置的注时探测器、能量探测器以及均匀度探测器进行了刻度。利用高能~(136)Xe离子获得了静态存储器IDT71256的单粒子翻转饱和截面和单粒子闭锁截面，在国内首次得到了该器件完整的G一LET曲线。并用改进的FONT方法预示了该器件以及其它常用宇航器件的在轨翻转率；用FOM公式、Barak经验公式和Lar叮模型推算这些器件的质子饱爪佩截而，少一仁对二种方法推算的结果进行了比较；探讨了利用HIRFL提供的高能~(12)C离子来模拟质子引起的单粒子效应的可能性；利用翻转截面与离子入射角度的关系估算了IDT71256敏感区的厚度以及聚酞亚胺膜的厚度，获得了截面与离子沉积能量的关系，临界沉积能量与临界LET值吻合，聚酞亚胺膜的厚度与对同类器件测量的结果一致；研究了离子入射角度对多位翻转的影响，在高LET值轰击下以及高能离子掠射的情况下，IDT71256多位翻转的比例可以高达70％，对于MBU敏感区中沉积的总能量及其分布范围是两个重要的参数；IDT71256单粒子翻转截面的角度效应主要是多位翻转的贡献；对实验中各种误差来源进行了分析。部分研究结果己经应用于星载七卜算机系统的抗辐射加固设计，建立的实验方法和理论模型为利用HIRFL开展宇航器件单粒子效应敏感度的评估奠定了坚实的基础。

重离子引起DNA损伤及其对细胞周期进程的影响

目的：木论文重点研究重离子不同剂量离子辐照后DNA损伤程度的变化，以及进而引起的细胞周期改变等现象。为重离子治癌的临床应用积累必要的基础数据。材料与方法：采用兰州重离子研究装置（HIRFL）加速的碳、氖等重离子辐照体外培养的贴璧肿瘤细胞，以单细胞电泳法（SCGE）检测DNA的损伤程度；以流式细胞技术（FCM）检测细胞的周期改变现象。结果：1．SMMC-7721月干癌细胞经重离子（氖、碳）辐照后，DNA损伤现象明显，表现为单细胞电泳中出现的普遍的拖尾现象（t-test，P<0.001，compared with control。2．80MeV／u 2ONe10＋辐照后立即检测发现：2Gy造成100％的细胞损伤：8Gy照射造成80％的细胞严重损伤：且彗尾拖尾长度随剂量增加早．指数关系增长，仔值为0.99058。3．辐照后12小时，若干不同剂量辐照的样品其彗尾长度趋于相同：如05协、Ic）和ZGy辐照样品的彗尾长度分别为132.3±12.8、132.9±9.5和133.1±11.7μm，24h，时为35.0±3.9、35.5±4.1和48.2±6.Oμm，这说明在一定剂量范围内（0.5-2Gy）的辐照下，随着修复时间的延长，细胞DNA的损伤程度将趋于相同。同时，细胞继续孵育12小时，对于0.55-2Gy辐照组来说DNA的损伤情况是24小时内操作最严重的。4．辐照后24小时，0.5-2Gy辐照组埙份明显修复，略高于对照，但是对于4Gy和SGy辐照组仍带有明显的损伤现魏。簇说眼熏离子辐照（>4Gy）所致DNA报伤的不足修复性。5，DNA的损伤将导致细胞通过一系列调节机制抑制细胞周期的进行，为DNA修复系统提供充足的时间进行DNA修复，从而造成明显的细胞周期阳．滞现琢，这在重离子辐照实验中同样得到证实，尤其是S期、G2／M期阻净带现象非常明显。

Atomic oxygen formation in a radio-frequency driven micro-atmospheric pressure plasma jet

Atomic oxygen formation in a radio-frequency driven micro-atmospheric pressure plasma jet is investigated using both advanced optical diagnostics and numerical simulations of the dynamic plasma chemistry. Laser spectroscopic measurements of absolute densities of ground state atomic oxygen reveal steep gradients at the interface between the plasma core and the effluent region. Spatial profiles resolving the interelectrode gap within the core plasma indicate that volume processes dominate over surface reactions. Details of the production and destruction processes are investigated in numerical simulations benchmarked by phase-resolved optical emission spectroscopy. The main production mechanisms are electron induced and hence most efficient in the vicinity of the plasma boundary sheath, where electrons are energized. The destruction is driven through chemical heavy particle reactions. The resulting spatial profile of atomic oxygen is relatively flat. The power dependence of the atomic oxygen density obtained by the numerical simulation is in very good agreement with the laser spectroscopic measurements.

Radiation-Pressure Acceleration of Ion Beams from Nanofoil Targets: The Leaky Light-Sail Regime

A new ion radiation-pressure acceleration regime, the "leaky light sail," is proposed which uses sub-skin-depth nanometer foils irradiated by circularly polarized laser pulses. In the regime, the foil is partially transparent, continuously leaking electrons out along with the transmitted laser field. This feature can be exploited by a multispecies nanofoil configuration to stabilize the acceleration of the light ion component, supplementing the latter with an excess of electrons leaked from those associated with the heavy ions to avoid Coulomb explosion. It is shown by 2D particle-in-cell simulations that a monoenergetic proton beam with energy 18 MeV is produced by circularly polarized lasers at intensities of just 10(19) W/cm(2). 100 MeV proton beams are obtained by increasing the intensities to 2 x 10(20) W/cm(2).

Investigations of DNA damage induction and repair resulting from cellular exposure to high dose-rate pulsed proton beams

Studies regarding the radiobiological effects of low dose radiation, microbeam irradiation services have been developed in the world and today laser acceleration of protons and heavy ions may be used in radiation therapy. The application of different facilities is essential for studying bystander effects and relating signalling phenomena in different cells or tissues. In particular the use of ion beams results advantageous in cancer radiotherapy compared to more commonly used X-rays, since the ability of ions in delivering lethal amount of doses into the target tumour avoiding or limiting damage to the contiguous healthy tissues. At the INFN-LNS in Catania, a multidisciplinary radiobiology group is strategically structured aimed to develop radiobiological research, finalised to therapeutic applications, compatible with the use of high dose laser-driven ion beams. The characteristic non-continuous dose rates with several orders of magnitude of laser-driven ion beams makes this facility very interesting in the cellular systems' response to ultra-high dose rates with non-conventional pulse time intervals cellular studies. Our group have projected to examine the effect of high dose laser-driven ion beams on two cellular types: foetal fibroblasts (normal control cells) and DU145 (prostate cancer cells), studying the modulation of some different bio-molecular parameters, in particular cell proliferation and viability, DNA damage, redox cellular status, morphological alterations of both the cytoskeleton components and some cell organelles and the possible presence of apoptotic or necrotic cell death. Our group performed preliminary experiments with high energy (60 MeV), dose rate of 10 Gy/min, doses of 1, 2, 3 Gy and LET 1 keV/µm on human foetal fibroblasts (control cells). We observed that cell viability was not influenced by the characteristics of the beam, the irradiation conditions or the analysis time. Conversely, DNA damage was present at time 0, immediately following irradiation in a dose-dependent manner. The analysis of repair capability showed that the cells irradiated with 1 and 2 Gy almost completely recovered from the damage, but not, however, 3 Gy treated cells in which DNA damage was not recovered. In addition, the results indicate the importance of the use of an appropriate control in radiobiological in vitro analysis.

Alpha particles induce pan-nuclear phosphorylation of H2AX in primary human lymphocytes mediated through ATM

The use of high linear energy transfer radiations in the form of carbon ions in heavy ion beam lines or alpha particles in new radionuclide treatments has increased substantially over the past decade and will continue to do so due to the favourable dose distributions they can offer versus conventional therapies. Previously it has been shown that exposure to heavy ions induces pan-nuclear phosphorylation of several DNA repair proteins such as H2AX and ATM in vitro. Here we describe similar effects of alpha particles on ex vivo irradiated primary human peripheral blood lymphocytes. Following alpha particle irradiation pan-nuclear phosphorylation of H2AX and ATM, but not DNA-PK and 53BP1, was observed throughout the nucleus. Inhibition of ATM, but not DNA-PK, resulted in the loss of pan-nuclear phosphorylation of H2AX in alpha particle irradiated lymphocytes. Pan-nuclear gamma-H2AX signal was rapidly lost over 24h at a much greater rate than foci loss. Surprisingly, pan-nuclear gamma-H2AX intensity was not dependent on the number of alpha particle induced double strand breaks, rather the number of alpha particles which had traversed the cell nucleus. This distinct fluence dependent damage signature of particle radiation is important in both the fields of radioprotection and clinical oncology in determining radionuclide biological dosimetry and may be indicative of patient response to new radionuclide cancer therapies.

Photoluminescence studies on RF plasma-polymerized thin films

Conjugated polymers in the form of thin films play an important role in the field of materials science due to their interesting properties. Polymer thin films find extensive applications in the fabrication of devices, such as light emitting devices, rechargeable batteries, super capacitors, and are used as intermetallic dielectrics and EMI shieldings. Polymer thin films prepared by plasma-polymerization are highly cross-linked, pinhole free, and their permittivity lie in the ultra low k-regime. Electronic and photonic applications of plasma-polymerized thin films attracted the attention of various researchers. Modification of polymer thin films by swift heavy ions is well established and ion irradiation of polymers can induce irreversible changes in their structural, electrical, and optical properties. Polyaniline and polyfurfural thin films prepared by RF plasmapolymerization were irradiated with 92MeV silicon ions for various fluences of 1×1011 ions cm−2, 1×1012 ions cm−2, and 1×1013 ions cm−2. FTIR have been recorded on the pristine and silicon ion irradiated polymer thin films for structural evaluation. Photoluminescence (PL) spectra were recorded for RF plasma-polymerized thin film samples before and after irradiation. In this paper the effect of swift heavy ions on the structural and photoluminescence spectra of plasma-polymerized thin films are investigated.

The influence of anisotropic F region ion velocity distributions on ionospheric ion outflows into the magnetosphere

The contribution to the field-aligned ionospheric ion momentum equation, due to coupling between pressure anisotropy and the inhomogeneous geomagnetic field, is investigated. We term this contribution the “hydrodynamic mirror force” and investigate its dependence on the ion drift and the resulting deformations of the ion velocity distribution function from an isotropic form. It is shown that this extra upforce increases rapidly with ion drift relative to the neutral gas but is not highly dependent on the ion-neutral collision model employed. An example of a burst of flow observed by EISCAT, thought to be the ionospheric signature of a flux transfer event at the magnetopause, is studied in detail and it is shown that the nonthermal plasma which results is subject to a hydrodynamic mirror force which is roughly 10% of the gravitational downforce. In addition, predictions by the coupled University College London-Sheffield University model of the ionosphere and thermosphere show that the hydrodynamic mirror force in the auroral oval is up to 3% of the gravitational force for Kp of about 3, rising to 10% following a sudden increase in cross-cap potential. The spatial distribution of the upforce shows peaks in the cusp region and in the post-midnight auroral oval, similar to that of observed low-energy heavy ion flows from the ionosphere into the magnetosphere. We suggest the hydrodynamic mirror force may modulate these outflows by controlling the supply of heavy ions to regions of ion acceleration and that future simulations of the effects of Joule heating on ion outflows should make allowance for it.

D (sJ) (2317) meson production at RHIC

We study the production of D (sJ) (2317) mesons in relativistic heavy ion collisions using the quark coalescence model. The predicted D (sJ) (2317) abundance depends sensitively on the quark structure of the D (sJ) (2317) meson. We have also evaluated the absorption cross sections of the D (sJ) (2317) meson by pi, rho, kaon and K* in a phenomenological hadronic model. We find that the final yield of D (sJ) (2317) mesons remains sensitive to its initial number produced from the quark-gluon plasma, providing thus the possibility of studying the quark structure of the D (sJ) (2317) meson and its production mechanism in relativistic heavy ion collisions.

Study of bulk matter properties through strange quark hadrons with the STAR experiment

Relativistic heavy ion collisions are the ideal experimental tool to explore the QCD phase diagram. Several results show that a very hot medium with a high energy density and partonic degrees of freedom is formed in these collisions, creating a new state of matter. Measurements of strange hadrons can bring important information about the bulk properties of such matter. The elliptic flow of strange hadrons such as phi, K(S)(0), Lambda, Xi and Omega shows that collectivity is developed at partonic level and at intermediate p(T) the quark coalescence is the dominant mechanism of hadronization. The nuclear modification factor is an another indicator of the presence of a very dense medium. The comparison between measurements of Au+Au and d+Au collisions, where only cold nuclear matter effects are expected, can shed more light on the bulk properties. In these proceedings, recent results from the STAR experiment on bulk matter properties are presented.

System size dependence of associated yields in hadron-triggered jets STAR Collaboration

We present results on the system size dependence of high transverse momentum di-hadron correlations at root s(NN) = 200 GeV as measured by STAR at RHIC. Measurements in d + Au, Cu + Cu and Au + Au collisions reveal similar jet-like near-side correlation yields (correlations at small angular separation Delta phi similar to 0, Delta eta similar to 0) for all systems and centralities. Previous measurements have shown Chat the away-side (Delta phi similar to pi) yield is suppressed in heavy-ion collisions. We present measurements of the away-side Suppression as a function of transverse momentum and centrality in Cu + Cu and Au + Au collisions. The suppression is found to be similar in Cu + Cu and An + An collisions at a similar number of participants. The results are compared to theoretical calculations based on the patron quenching model and the modified fragmentation model. The observed differences between data and theory indicate that the correlated yields presented here will further constrain dynamic energy loss models and provide information about the dynamic density profile in heavy-ion collisions. (C) 2009 Elsevier B.V. All rights reserved.