A low-cost computer cluster for the calculation of atomic data of importance in plasma physics

高分辨率光谱学在等离子体物理的许多领域具有重要意义，它提供了关于各种实验室和天体物理等离子体的信息，包括磁限制托卡马克、激光产生的等离子体和太阳日冕。对高分辨率光谱建模的一个重要要求是一系列原子物理参数和过程的准确数据，包括能级、跃迁几率和电子碰撞激发截面。在贝尔法斯特女王大学(QUB)，我们有一个卓有成效的研究计划，使用我们复杂的程序，如RMATRX，计算用于等离子体物理应用的原子数据。我们的计算主要是在2005年通过EPSRC设备赠款购买的18台个人计算机(PC)上进行的。然而，该集群现在已经过了保修期，有几台机器不再运行。同样重要的是，由于CPU处理器技术和速度的快速进步，按照目前的标准，工作站现在提供的处理能力很差。因此，我们的原子物理研究计划的生产率和竞争力正受到严重影响。因此，在这项提案中，我们寻求为购买7台新PC提供适度资金。这笔资金将由昆士兰大学的数学和物理学院匹配，因此总共可以购买14台PC，提供一个计算能力将比我们现有的群集大一个数量级以上的群集。新的PC群集将用于产生高精度的原子数据，以支持一些主要的实验光谱计划，特别是那些涉及托卡马克的计划。这些是为研究和最终产生核聚变而建造的磁约束等离子体设备。在英国，托卡马克实验在库勒姆聚变能源中心进行。这是几个托卡马克的所在地，包括世界上最大的联合欧洲环(JET)。我们将进行原子物理计算，以帮助模拟新的和创新的喷射实验，这将解决等离子体科学中的几个关键问题，包括(I)评估使用JET上的偏滤器提取杂质离子的效率，(Ii)诊断聚变过程中的阿尔法粒子产额。我们还将为输入到银河系和云计算程序进行原子物理计算，这两个程序在英国被广泛用于分别模拟以光致电离为主的实验室和天体物理等离子体。这些代码的预测将与利用GEKKO-XII激光设备产生的诊断良好的光电离主导的硅等离子体的X射线光谱进行比较。这反过来将允许我们在物理条件下对云代码进行基准测试，这些条件类似于以光致电离为主的天文来源，特别是活动星系核(包括类星体)。我们还将能够在极端光致电离条件下对实验室代码Galaxy进行基准测试。

High resolution spectroscopy is of major importance in many areas of plasma physics, and provides information on a diverse range of laboratory and astrophysical plasmas, including e.g. magnetically-confined tokamaks, laser-produced plasmas and the solar corona. A vital requirement for the modelling of high resolution spectra is accurate data for a range of atomic physics parameters and processes, including e.g. energy levels, transition probabilities and electron impact excitation cross sections. At Queen's University Belfast (QUB), we have a highly productive research programme on the calculation of atomic data for applications in plasma physics, using our sophisticated codes such as RMATRX. Our calculations have been undertaken primarily on a cluster of 18 personal computers (PCs), purchased in 2005 via an EPSRC equipment grant. However, the cluster is now out of warranty, with several machines no longer operational. Just as importantly, the workstations now provide, by current standards, poor processing power, due to the rapid advances in CPU processor technology and speed. As a consequence, the productivity and competitiveness of our atomic physics research programmes are being seriously affected. In this proposal we therefore seek modest funding for the purchase of 7 new PCs. This funding will be matched by the School of Mathematics and Physics at QUB, so that a total of 14 PCs can be purchased, providing a cluster which will have a computational power more than an order of magnitude greater than our existing cluster.The new PC cluster will be employed to produce highly accurate atomic data in support of a number of major experimental spectroscopic programmes, in particular those involving tokamaks. These are magnetically-confined plasma devices which have been built for the study and eventual generation of nuclear fusion. In the UK, tokamak experiments are undertaken at the Culham Centre for Fusion Energy. This is the site of several tokamaks, including the Joint European Torus (JET), the world's largest. We will undertake atomic physics calculations to help model new and innovative JET experiments, which will address several key issues in plasma science, including (i) assessing the efficiency of impurity ion extraction using the divertor on JET, (ii) diagnosing the alpha-particle yield during fusion.We will also undertake atomic physics calculations for input to the GALAXY and CLOUDY codes, widely used in the UK to model photoionisation-dominated laboratory and astrophysical plasmas, respectively. The predictions from the codes will be compared with an X-ray spectrum of a well-diagnosed photoionisation-dominated silicon plasma generated using the GEKKO-XII laser facility. This in turn will allow us to benchmark the CLOUDY code under physical conditions similar to those found in photoionisation-dominated astronomical sources, in particular active galactic nuclei (including quasars). We will also be able to benchmark the laboratory code GALAXY under extreme photoionisation conditions.