Study on mutual interaction between high energy ion beams and carbon materials related to interstellar material

本研究使用安装在UTTAC（筑波大学串联加速器中心）束流线上的新设计的“可调温度试样辐照室”进行。对于辐照试样，由于结构简单，首先采用石墨、煤、人工合成和天然金刚石等简单碳材料代替星际尘埃类碳材料如多环芳烃等。用不同能量和电流的质子束照射梯状标本架上的标本。在实验过程中，观察到金刚石样品的发光现象。我们将质子束轰击引起的金刚石离子发光作为本研究的一部分，因为目前关于离子发光现象的报道很少，而且这种发光是检测晶体结构缺陷形成和改变的一种非常灵敏的探针。在接近液氮的温度下获得离子发光光谱，并与阴极发光光谱进行比较。在开始的时候，光谱与阴极发光的光谱基本一致，但在辐照后期出现了几个新峰。PIXE和离子发光相结合的分析将是分析缺陷中杂质种类和结构的有效方法。采用FTIR、拉曼光谱、ESCA等光学方法对辐照后的样品进行了研究。结果表明，虽然观察到石墨结构向非晶碳的分解，以及从非晶到石墨的蚀变生长，但在本研究中没有发现其他相向金刚石结构的转变。然而，陨石中的钻石和高U含量煤中的钻石，可能与宇宙射线或U的辐射有关，都是埃级的，可以想象，这种转变只能稳定在埃级。如果金刚石是埃级的，本研究中使用的光学方法无法检测到如此小尺寸的相。目前，我们正在对辐照碳样品中的石墨和非晶相进行抽吸实验，用过氧化氯浓缩辐照实验中可能产生的金刚石相。用透射电镜和扫描电镜观察了本次抽吸实验的残留物。这种观察现在正在进行中。我们将继续这项研究，并将样品扩展到其他碳材料，如多环芳烃。少

This study was carried out using a newly designed "Temperature adjustable specimen irradiation chamber" installed on a beam line in the UTTAC (University of Tsukuba Tandem Accelerator Center). For the irradiation specimen, simple carbon materials such as graphite, coal, and synthetic and natural diamonds were firstly employed instead of interstellar dust like carbon materials such as PAH because of their simple structures. The specimens on a ladder like specimen holder were irradiated by proton beams of different energies and currents. During the experiments, luminescence was observed on the diamond specimens. We investigated this ion-luminescence of diamond caused by the proton beam bombardment as the part of this study, because there are very few reports on the ion-luminescence phenomena, and the luminescence is a very sensitive probe on the detection of the formation and alteration of the structural defect in crystal. The ion-luminescence spectra were taken at near the liquid nitrog … More en temperature and were compared with those of cathode luminescence spectra. The spectra were almost similar to those of cathode luminescence at the beginning, but several new peaks were observed at the late stage of the irradiation. The combination analysis of PIXE and the ion-luminescence will be an effective method for analyzing the species and the structures of impurities in the defect.The irradiated specimens were investigated by the optical methods such as FTIR,Raman spectrometry, ESCA,etc. As the results, although the break down of graphite structure to amorphous carbon, and the alteration growth from amorphous to graphite were observed, transformation to the diamond structure from other phases was not detected in this investigation. However, all the diamonds in meteorites and the diamond found in coal with high U content, which may be related with irradiation of cosmic-ray or radiation of U,are in Angstrom size, and it is conceivable that this transformation can be stabilized only in the Angstrom size. If diamond is Angstrom size, optical methods used in this study are not able to detect such a small size phases. We are now carrying out evacuation experiment of the graphite and amorphous phases in the irradiated carbon specimens using chlorine peroxide for concentrating the possible diamond phase occurred by the irradiation experiments. The residues of this evacuation experiments are observed by TEM and SEM.This observation is now on the way. We will continue this study and extend the specimen to other carbon materials such as PAH. Less