Novel ion detector for fusion plasma diagnostics

Abstract

A novel thin silicon detector for the neutral particle analyzers (NPA) of the joint European Torus (JET) is introduced for studying plasma characteristics during the fusion experiments. The new ion detector would replace the presently used very thin scintillator - photomultiplier tube combination. The proposed new NPA detector is based on direct conversion of charge in silicon and approximate matching of the detector thickness with the ranges of the observed ions. A thin silicon detector is only weakly sensitive to photon and neutron backgrounds but detects highly ionizing ions efficiently. Even high energy gammas deposit only little energy in the thin detector allowing effective background discrimination through pulse- height-analysis. Thin silicon strip detectors have been fabricated by using the silicon-on-insulator (SOI) technology. Fabricated detectors have 6 or 26 mum thick high resistive silicon bonded on a conductive silicon support. The thinner detectors are designed to be used for the low energy NPA and the thicker ones for the high energy NPA. The presentation comprises a short introduction to the fabricated detector structures, TCAD simulations and results of the electrical and spectroscopic characterizations.