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 detector）可用于测量磁约束聚变等离子体中的逃逸快离子。这类多层探测器不仅可获取总逃逸离子产率，还能解析逃逸离子的能量分布。此前的探测器多由离散箔片与绝缘片组装而成。本文概述了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目标。该方法制备的探测器将应用于JET与NSTX-U。该探测器将由铝与二氧化硅交替沉积的多层结构构成，层厚可通过精准调控以分离目标能量区间的离子。相较于传统制备工艺，薄膜沉积法的结构更为简单、机械稳定性更强，同时可实现膜厚的精确控制。此外，该沉积制备工艺可使各层之间实现紧密的热接触，从而实现层内离子沉积热的三维传导与耗散；而传统的离散箔片堆叠结构仅能实现基本的二维热传导。