强流高电荷态难熔金属离子的产生

发布时间:2019-01-09 11:32
【摘要】:自上世纪的80年代末,ECR离子源为核物理及重离子加速器等领域做出了突出的贡献,此后世界各地的科学家们纷纷开展了对ECR离子源的研究。ECR离子源得到不断发展,其种类从早期的第一代离子源装置演变到如今以超导离子源技术为代表的第三代装置,其所能产生的离子类型也已从早期的几种气体如氮气、氧气等的中低电荷态离子,到现在从H到U的所有金属或非金属原子的高电荷态离子。大部分金属元素在自然界中处于固态,需要将其气态化才能进入ECR离子源中产生对应的元素离子,且气态化的金属原子(或簇团)数量需达到一定值。当前,在ECR离子源中产生这些在常温常压下只以固态形式存在的元素气态主要有以下几种方法:炉子加热法、直接等离子体加热法、等离子体溅射法、激光熔融技术以及挥发性化合物金属离子(MIVOC,Metallic ion from volatile compound)法等,其中炉子加热法具有束流强度高、稳定性好的特点。炉子加热法按其工作温区主要分为低温炉、高温炉,其中高温炉主要针对熔点1500 ℃以上的金属元素如钴、钛、钒、铂、铀等的强流离子束产生。本论文课题设计一种目标工作在1800~2000 ℃的高温金属炉,通过ANSYS仿真模拟分析了直流加热电阻炉中钽坩埚的温度分布及其在ECR离子源工作环境的强磁场中所受的洛伦兹力,并对坩埚高温下所受热应力进行模拟分析。根据模拟分析结果研制了直流加热电阻炉的结构,并对其进行了离线测试,实验中钽坩埚在1800 ℃以上发生的形变与ANSYS模拟结果相符,根据模拟分析给出了改进方案。改进后的电阻式加热高温炉能在1500 ℃时稳定维持48小时以上,而在1846 ℃时稳定维持6小时以上。对直流加热电阻炉进行了在线测试,得到了 25 eμA的Ni19+以及185 eμA的Pb28+,验证所设计的高温炉能在ECR离子源强磁场的环境中工作,同时针对出现的问题分析了影响高温炉稳定运行的因素。与此同时,研制了高频加热感应炉及电子束加热蒸发炉,并对两者进行了离线测试,结果表明两者均能使坩埚温度达到1800℃以上。对电子束加热蒸发炉进行了在线测试,结果表明电子束加热蒸发炉受ECR离子源弧腔内强磁场洛伦兹力的作用而无法正常工作,有待改进。
[Abstract]:Since the late 1980s, ECR ion sources have made outstanding contributions to nuclear physics and heavy ion accelerators. Since then, scientists all over the world have carried out research on ECR ion sources. ECR ion sources have been continuously developed. Its species evolved from the early generation ion source devices to the third generation devices represented by the superconducting ion source technology, and the ion types it can produce have also changed from the low charge state ions of several gases such as nitrogen and oxygen. The highly charged state ions of all metal or non-metallic atoms from H to U up to now. Most metal elements are in solid state in nature, and they need to be gaseous to enter the ECR ion source to produce corresponding element ions, and the number of gaseous metal atoms (or clusters) should reach a certain value. At present, there are several methods to produce the gaseous state of these elements in ECR ion source only in solid state at room temperature and atmospheric pressure: furnace heating, direct plasma heating, plasma sputtering, and so on. Laser melting technology and volatile compound metal ions (MIVOC,Metallic ion from volatile compound) method, the furnace heating method has the characteristics of high beam intensity and good stability. The furnace heating method is mainly divided into low temperature furnace and high temperature furnace according to its working temperature region. The high temperature furnace is mainly used to produce high current ion beam of metal elements such as cobalt, titanium, vanadium, platinum, uranium and so on, whose melting point is above 1500 鈩,

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