Fast ion physics studies on MAST Upgrade with a neutron diagnostic

带有中子诊断的 MAST 升级的快离子物理研究

• 批准号: 2820006
• 金额: --
• 依托单位: Durham University
• 依托单位国家: 英国
• 项目类别: Studentship
• 财政年份: 2022
• 资助国家: 英国
• 起止时间: 2022 至 无数据
• 项目状态: 未结题
• 来源: https://gtr.ukri.org/projects?ref=studentship-2820006
• 关键词: Fast; ion; physics; studies; MAST

In fusion plasmas, fast ions have energies much higher than the thermal plasma background. Fast ions are generated by external auxiliary heating such as Neutral Beam Injection (NBI) and Ion Cyclotron Resonance Heating (ICRH) or by the fusion reactions themselves. In the former cases, fast ions are hydrogen isotopes with energies in the range from tens of keVs up to a few MeVs. Fusion reactions produce, in addition to hydrogen isotopes, alpha particles with energies in the MeV range.Fast ions play an important role in heating the plasma, maintaining the high temperatures necessary to sustain the fusion reactions and crucial in achieving a burning plasma. NBI heating is also important for current drive, that is for long pulse operation of tokamaks beyond the inductive regime and therefore for the realization of a fusion reactor.Confining fast ions in the plasma for time long enough so that they can transfer their energy to the background plasma is therefore crucial for achieving the goal of a power plant based on thermonuclear fusion reactions. However, fast ion confinement is degraded by plasma instabilities some of which are triggered by the fast ion themselves. In this case, energy exchange between the fast ions and the instabilities result in the redistribution and loss of fast ions, ultimately reducing the performances of fusion reactors. Furthermore, the loss of fast ions in the plasma can result in the damage of the reactor first wall, an issue particularly for the very energetic alpha particles that will be produced in ITER and DEMO.MAST Upgrade unique capabilities provide the opportunity to study the interplay between fast ions and plasma instabilities in a wide range of plasma scenarios that are not achievable in other present day conventional tokamaks. The combination of broader NBI power deposition profiles and low magnetic field allows the study of the behavior and confinement properties of super-Alfvénic fast ions. MAST Upgrade is equipped with a wide range of diagnostics dedicated to the study of fast ions: an upgraded neutron camera, a fast ion loss detector, a fast ion D-alpha monitor, a compact neutral particle analyzer and a charged fusion product detector. Combined, these diagnostic will provide the most exhaustive description of fast ion confinement in spherical tokamak to date and will enable the benchmarking and development of the simulations codes that are used to design fusion reactor operating scenarios extrapolating from present day devices.The project will focus on the analysis and modelling of the recently installed 6-channels neutron measurements in the presence of a wide range of instabilities such as sawteeth, fishbones, toroidal Alfvén eigenmodes, long-lived modes and edge localized modes, as well as assessing the role of on-axis and off-axis NBI heating in suppressing the drive of energetic particle modes and in driving plasma current non-inductively. This is mainly an experimental project which includes participation to experiments at MAST Upgrade at CCFE and data analysis and modelling at Durham University. Modelling will be carried out using the codes TRANSP and NUBEAM which, in combination with synthetic diagnostics simulation codes, are used to compare experimental and simulations observations.

在聚变等离子体中，快离子具有比热等离子体背景高得多的能量。快离子是由外部辅助加热产生的，如中性束注入（NBI）和离子回旋共振加热（ICRH）或由聚变反应本身产生。在前一种情况下，快离子是氢同位素，其能量范围从几十keV到几MeV。聚变反应除了产生氢同位素外，还产生能量在MeV范围内的α粒子。快离子在加热等离子体、维持维持聚变反应所需的高温以及实现燃烧等离子体方面发挥着重要作用。NBI加热对于电流驱动也很重要，即托卡马克在感应区之外的长脉冲运行，因此对于实现聚变反应堆也很重要。因此，将快离子限制在等离子体中足够长的时间，使它们能够将能量转移到背景等离子体中，对于实现基于热核聚变反应的发电厂的目标至关重要。然而，快离子约束退化的等离子体不稳定性，其中一些是由快离子本身触发。在这种情况下，快离子之间的能量交换和不稳定性导致快离子的重新分布和损失，最终降低聚变反应堆的性能。此外，等离子体中快离子的损失可能会导致反应堆第一壁的损坏，这对于ITER和DEMO中将产生的高能α粒子来说尤其是一个问题。MAST升级的独特功能提供了在广泛的等离子体场景中研究快离子和等离子体不稳定性之间相互作用的机会，这在其他当今传统托卡马克中是无法实现的。更广泛的NBI功率沉积剖面和低磁场的组合允许超Alfvénic快离子的行为和约束特性的研究。MAST升级配备了广泛的诊断专用于快离子的研究：升级的中子相机，快离子损失探测器，快离子D-α监测器，紧凑的中性粒子分析仪和带电聚变产物探测器。综合起来，这些诊断将提供迄今为止球形托卡马克中快离子约束的最详尽的描述，并将使用于设计聚变反应堆操作方案的模拟代码的基准测试和开发成为可能。通道中子测量存在广泛的不稳定性，如锯齿，鱼骨，环形Alfvén本征模式，长寿命模式和边缘局域模式，以及评估轴上和离轴NBI加热在抑制高能粒子模式驱动和非感应驱动等离子体电流中的作用。这主要是一个实验项目，包括参与CCFE的MAST升级实验和达勒姆大学的数据分析和建模。将使用代码TRANSP和NUBEAM进行建模，这些代码与合成诊断模拟代码相结合，用于比较实验和模拟观察结果。