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Spectrum study of defects induced by stored energy ions in wide band gap semiconductor materials
No full textGaN和SiC都是第三代半导体材料的典型代表。 它们具有耐高温、 抗辐射、 宽禁带、
高电子迁移率、高击穿电压、高饱和电子漂移速度、高热导率等优良的性质，因此SiC
被应用于高温抗辐射环境如聚变堆材料、航天探测，航空，卫星，汽车发动机等以及高
温、高频、大功率电子器件的制造，而 GaN 被用于制造短波发光二极管、紫外光电二
极管、紫外光探测器、大功率微波器件等。
高电荷态离子携带较高的势能， 在与固体表面碰撞时会通过瞬间释放势能而导致表
面原子的增强溅射，因而有可能在材料表面形成纳米量级的结构。实践应用方面，可以
为 X 射线激光，纳米刻蚀和小型纳米器件，表面分析技术，离子注入技术研制提供相
关参数和技术储备。本论文工作采用低速高电荷态Xe、Pb 离子辐照 GaN和 SiC，并做
了如下两方面的分析：
（1）对 Xe、Pb 离子辐照 GaN，对表面化学组成和元素化合态以及表面形貌进
行了 XPS 和 AFM 分析。XPS 实验结果表明：高电荷态离子辐照 GaN 样品造成样品表
面 Ga-N 键发生断裂，表面 N 缺乏而 Ga 富集；随着入射离子剂量和电荷态的增大，晶
格损伤增加，Ga-N键含量减小，形成的Ga-Ga 键相对含量增大；就 Ga-Ga 键相对含量
而言，本实验条件下在入射离子剂量、电荷态（势能） 、入射角这几个因素中，剂量因
素起主要作用，在剂量差别不大的情况下，电荷态（势能）起决定作用，而入射角的影
响相对较小； AFM 分析表明当离子电荷态达到某个值， 即所携带的势能达到某个阈值时，
材料表面会形成纳米蚀刻，若低于此阈值则表面形成肿胀。
（2）对 Xe 离子辐照的 SiC，对表面形貌和损伤进行了 AFM、FTIR 和 Raman分析。 实验采用600keV的Xe
18+和Xe26+离子， 剂量范围从1014ions/cm2到1016ions/cm2。在实验所用离子剂量范围内，实验结果表明：在AFM 测试中，对于 Xe18+离子，台阶高度和表面粗糙度随剂量增加而增加， 但对于Xe26+离子则先增加后减少； 在FTIR 测试中，只有在 Xe26+离子垂直入射情况下， 在大约 930cm-1处出现一个深的反射凹槽， 对于 Xe18+离子则没有；在拉曼谱图中，一些表征非晶 SiC 的展宽的谱带出现在 Xe26+离子辐照的样品中，但在 Xe18+离子辐照的样品中则出现了表征晶体的典型拉曼峰。因此两者都在表面造成了损伤，但只有 Xe26+离子在表面形成了非晶层
Investigation of mechanical properties of metals and binary alloys
No full text随着分子动力学模拟方法的发展，涨落方法成为一种新的计算材料力学性质的方法。和传统的理论方法相比，涨落公式能更有效的处理温度效应对材料力学性质的影响。本文以涨落公式为研究方法，系统的研究了金属Au、Pd、Ag、Pt和二元合金Au-Pd、Ag-Pt的力学性质。
文中采用的描述原子间的作用势为Finnis-Sinclair势。首次计算了Au3Pd、AuPd、AuPd3、Ag3Pt、AgPt和AgPt3 合金的晶格常数、结合能和弹性常数，并预测了它们的熔点。随温度的增加，金属和合金的晶格常数和结合能增大，弹性常数和体模量减小。通过比较合金和其组分金属的计算结果，Au3Pd、AuPd、AuPd3、Ag3Pt的晶格常数和弹性常数介于其组分金属之间，而AgPt、AgPt3的剪切模量和熔点高于其组分金属Ag和Pt。最后对涨落公式的组分Born项，涨落项和温度项进行了研究分析，其中贡献最大的是Born项，涨落项次之，温度项最小
SSC束流特性及传输效率的研究
No full text现在，物理实验对束流流强和品质的要求越来越高。从目前来看，兰州重离子加速器装置（HIRFL）所提供的束流要很好地满足物理实验的要求，需要对现有加速器系统进行一定的升级改造，而其中关键的环节就是HIRFL系统中的分离扇回旋加速器SSC。SSC对大部分束流的传输效率较低，其现有注入器SFC所能提供的束流强度有限，从而限制了整个加速器系统的束流强度。鉴于以上原因，中科院近代物理研究所计划给SSC新建一台直线注入器（SSC-LINAC），以使SSC束流向更重的离子和更高的流强发展，本文通过对SSC束流传输的模拟计算，为SSC-LINAC提供了重要的参数。另外，现在SSC的运行效率比较低，通过模拟计算发现了SSC运行效率低的主要原因，这将为进一步提高SSC的运行调束和升级改造提供依据
AXIAL INJECTION BEAM LINE OF A COMPACT CYCLOTRON*
No full textAxial injection beam line of the compact cyclotron is<br />presented. It is intended for transportation of the C5+ ion<br />beam obtained in the permanent magnet ion source. The<br />beam line is only 3.486 m from the ion source to the<br />entrance of spiral inflector, it consists of two glasser lens,<br />one double 90-degree bend magnet, one quadrupole and<br />two solenoid lens. The sinusoidal buncher, Faraday cap<br />and chopper are used respectively for increasing seizing<br />efficiency, beam diagnostics and choice of beam<br />utilizing time. The bend magnet and a slit collimator are<br />used for choice of C5+ ion beam
RECENT PROGRESS ON THE FACILITY UPGRADE FOR ACCELERATED RADIOACTIVE BEAMS AT TEXAS A&M *
No full textThe Cyclotron Institute at Texas A&M University is<br />involved in an upgrade, one goal of which is to provide<br />radioactive ion beams accelerated to intermediate<br />energies by the K500 superconducting cyclotron. The old<br />88” cyclotron, now the K150, has been refurbished to be<br />used as a driver and also to provide higher intensity, lowenergy,<br />primary beams for experiments. Two external ion<br />sources, an electron-cyclotron-resonance ion source<br />(ECRIS) and a multi-cusp negative ion source, have been<br />installed on a new axial line to inject beams into a<br />modified K150 central region. Acceleration of negative<br />ions of protons and deuterons with stripping for<br />extraction will be used in order to mitigate activation of<br />the K150. Beams from the K150 will be used to create<br />radioactive species via a light-ion guide and a heavy-ion<br />guide. Singly charged ions from either ion guide will be<br />transported to an ECRIS that is configured to capture<br />these ions and further ionize them. One charge-state from<br />this second ECRIS will be selected for subsequent<br />acceleration by the K500. Progress on the upgrade,<br />including the acceleration and extraction of both negative<br />and positive beams by the K150, is presented
MAGNET DESIGN OF 70 MEV SEPARATED SECTOR CYCLOTRON (KORIA)*
No full text<p>A K=100 separated sector cyclotron is being designed in SKKU in South Korea, this cyclotron is considered the<br />main drive for ISOL to produce ~ 70MeV proton beam<br />and 35 MeV deuteron beam for production of radioactive<br />material as a basic nuclear research.<br />In this paper we will describe CST numerical<br />simulation for determining the basic magnet parameters,<br />magnet material, deformation, imperfection fields and<br />preliminary ion beam dynamics study for verifying the<br />focusing properties of the designed magnet.</p>IMP;Chinese Academy of Science
ADVOCACY FOR A DEDICATED 70 MEV PROTON THERAPY FACILITY
No full textSince 1998 we treated more then 1500 patients with eye
tumours at the HZB cyclotron with a 68 MeV proton
beam.
The 5 years follow up shows a tumour control rate of
more then 96%. The combination of a CT/MRT based
planning and excellent physical beam conditions like
2 nA in the scattered proton beam, a 0.94 mm distal dose
falloff and a dose penumbra of 2.1 mm offers the
opportunity to keep side effects on a lowest level.
However all new medical proton facilities are equipped
with accelerators delivering beams of 230 MeV and more.
While this is needed for deep seated tumours, a lot of
physical and medical compromises have to be accepted
for the treatment of shallow seated tumours like eye
melanomas.
Hence, we suggest a 70 MeV proton therapy facility. It
should be equipped with a horizontal beam line and can
have optionally a vertical line for more complicated cases
under anaesthetics or for biological experiments. By the
use of PBO-Lab and MCNPX beam line concepts and a
radio-protecting architecture are designed.IMP;Chinese Academy of Science
DESIGN STUDY OF AVF MAGNET FOR COMPACT CYCLOTRON
No full textK=100 separated sector cyclotron and its injector
cyclotron design is started on April, 2010 at
Sungkyunkwan University. The main purpose of the
K=100 separated sector cyclotron is producing proton and
deuteron beam for ISOL which generate rare isotopes to
accelerate RI beam for basic science research. In K=100
separated sector cyclotron facilities, two 8MeV sector
focused cyclotrons will be used as an injector cyclotron
for the main cyclotron.
In this paper, an Azimuthally Varying Field (AVF)
magnet for the 8MeV injector cyclotron is designed to
produce 8MeV proton beam and 4MeV deuteron beam.
All field simulations have been performed by OPERA-3D
TOSCA for 3D magnetic field simulation. The
assignments of these injector cyclotrons are generating
8MeV, 1mA proton beam and 4MeV deuteron beam that
inject to the main cyclotron.IMP;Chinese Academy of Science
TOWARDS THE 2 MW CYCLOTRON AND LATEST DEVELOPMENTS AT PSI
No full textPSI operates a cyclotron based high intensity proton
accelerator routinely at an average beam power of 1.3MW.
With this power the facility is at the worldwide forefront
of high intensity proton accelerators. An upgrade program
is under way to ensure high operational reliability and
push the intensity to even higher levels. The beam current
is practically limited by losses at extraction and the
resulting activation of accelerator components. Further
intensity upgrades are only possible if the relative losses
can be lowered in proportion, thus keeping absolute losses
at a constant level. The basic upgrade path involves the
reduction of space charge induced extraction losses by
implementing improved RF systems and resonators in
both cyclotrons. The paper describes the ongoing upgrade
program, achievements that were realized since the last
cyclotron conference and several operational experiences
and difficulties that were observed during routine
operation.IMP;Chinese Academy of Science