An understanding of fast (supra-thermal) ion behavior is of great importance in tokamak physics and is a subject studied from both theoretical and experimental perspectives. This paper investigates the spatial energy and density distributions of RF accelerated deuterons using the neutron camera at the tokamak JET. Using the 19 liquid scintillator detectors available in the neutron camera system, we obtain spatial information that cannot be accessed with a single sightline. We present a spectroscopic analysis method in which a spatially resolved model of the fast ion distribution is fitted to the pulse height spectra from all 19 detectors simultaneously. The fast ion distribution is parameterized in such a way that the density, energy, and pitch-angle parts are uncoupled. The energy part is composed of a Maxwellian distribution, characterized by an ‘RF tail temperature,’ and the spatial dependence is modeled as a two-dimensional Gaussian distribution on the poloidal plane of the tokamak. From this parameterized model, we can calculate the spectrum of fusion born neutrons originating from reactions involving RF accelerated deuterons, and by fitting this model to the measured neutron camera pulse height spectra, we obtain an estimate of the spatially resolved distribution of the fast deuterons. The method has been applied to three JET pulses using different RF heating schemes and is shown to identify several features of the fast ion distribution produced in the various scenarios. Hence, this method is able to provide quantitative information about the fast ion distribution resulting from different heating schemes, and can also be useful, e.g., to validate simulation results from RF modeling codes.

对快速（超热）离子行为的理解在托卡马克物理学中非常重要，并且是从理论和实验角度研究的主题。本文利用托卡马克JET上的中子相机研究了RF加速氘核的空间能量和密度分布。使用中子相机系统中可用的19个液体闪烁体探测器，我们获得了无法通过单个视线访问的空间信息。我们提出了一种光谱分析方法，其中快速离子分布的空间分辨模型同时应用于所有19个检测器的脉冲高度谱。快速离子分布的参数化方式是使密度，能量和螺距角部分不耦合。能量部分由麦克斯韦分布组成，其特征是“ RF尾部温度”，并且空间依赖性被建模为在托卡马克的极向面上的二维高斯分布。从该参数化模型中，我们可以计算源自涉及RF加速氘核反应的聚变中子的光谱，并将该模型与所测量的中子相机脉冲高度光谱拟合，可以估算出快速氘核的空间分辨分布。该方法已应用到使用不同的RF加热方案的三个JET脉冲中，并显示出该方法可识别在各种情况下产生的快速离子分布的几个特征。因此，该方法能够提供有关由不同加热方案产生的快速离子分布的定量信息，并且也很有用，例如，