Design of Faraday cup ion detectors built by thin film deposition

Thin film Faraday cup detectors can provide measurements of fast ion loss from magnetically confined fusion plasmas. These multilayer detectors can resolve the energy distribution of the lost ions in addition to giving the total loss rate. Prior detectors were assembled from discrete foils and insulating sheets. Outlined here is a design methodology for creating detectors using thin film deposition that are suited to particular scientific goals. The intention is to use detectors created by this method on JET and NSTX-U. The detectors will consist of alternating layers of aluminum and silicon dioxide, with layer thicknesses chosen to isolate energies of interest. Thin film deposition offers the advantage of relatively simple and more mechanically robust construction compared to other methods, as well as allowing precise control of film thickness. Furthermore, this depositional fabrication technique places the layers in intimate thermal contact, providing for three-dimensional conduction and dissipation of the ion-produced heating in the layers, rather than the essentially two-dimensional heat conduction in the discrete foil stack implementation.薄膜法拉第杯探测器（Thin film Faraday cup detectors）可实现磁约束聚变等离子体的快离子损失测量。此类多层探测器不仅可获取总损失率，还能解析损失离子的能量分布。此前的探测器均采用分立箔片与绝缘片组装制备。本文提出一种基于薄膜沉积工艺的探测器设计方法，可适配特定科学研究需求。该方法制备的探测器将应用于JET与NSTX-U装置。探测器结构为铝与二氧化硅交替沉积的多层膜系，通过优化层厚以分离目标能量区间。相较于传统制备工艺，薄膜沉积法不仅结构更简洁、机械稳定性更佳，还可实现膜层厚度的精准调控。此外，该沉积制备工艺可使各层间实现紧密热接触，能够完成层内离子辐照产热的三维传导与耗散；而分立箔片堆叠结构仅能实现基本的二维热传导。