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学的许多领域都非常重要，并提供了各种实验室和天体物理等离子体的信息，包括例如磁约束托卡马克，激光产生的等离子体和日冕。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，包括例如能级、跃迁概率和电子碰撞激发截面。在贝尔法斯特女王大学（QUB），我们有一个非常富有成效的研究计划，在等离子体物理应用的原子数据的计算，使用我们的复杂的代码，如RMATRX。我们的计算主要是在2005年通过EPSRC设备赠款购买的18台个人电脑（PC）的集群上进行的。然而，该集群现已超出保修期，其中几台机器已不再运行。同样重要的是，由于CPU处理器技术和速度的快速发展，按照当前标准，工作站现在提供的处理能力很差。因此，我国原子物理研究方案的生产力和竞争力受到严重影响。因此，在本提案中，我们寻求适当的资金用于购买7台新的PC。昆士兰大学数学和物理学院将提供相应的资金，因此总共可以购买14台个人计算机，提供一个计算能力比我们现有集群高出一个数量级的集群。新的个人计算机集群将用于产生高度精确的原子数据，以支持一些主要的实验光谱计划，特别是涉及托卡马克的计划。这些都是磁约束等离子体设备已建成的研究和最终产生的核聚变。在英国，托卡马克实验在卡勒姆聚变能中心进行。这是几个托卡马克的所在地，包括世界上最大的欧洲联合环（JET）。我们将进行原子物理计算，以帮助模拟新的和创新的JET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α粒子产额。我们还将进行原子物理计算，以输入GALAXY和CLOUDY代码，在英国被广泛用于模拟光电离主导的实验室和天体物理等离子体。从代码的预测将进行比较，一个良好的诊断光电离为主的硅等离子体使用GEKKO-XII激光设施产生的X射线光谱。这反过来将使我们能够在类似于光电离主导的天文源，特别是活动星系核（包括类星体）中发现的物理条件下对云代码进行基准测试。我们还将能够在极端光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.