Escaping Energetic Ion Measurement on Large Scale Magnetic Fusion Devices

Abstract

For escaping energetic ion measurements on magnetic fusion devices it is very important to get information on spatial distributions (poloidally and toroidally), pitch angle and energy distributions of escaping energetic ions. This paper presents two kinds of optical measurements of escaping energetic ions. The first is a scintilator-type probe which can resolve simultaneously both pitch angle and gyroradius of lost ions. The second is ceramic scintilator plates fixed on the first wall directly to survey spatial distribution of lost ions. There are difficulties in escaping energetic ion measurements in large scale magnetic fusion devices. For example, signal transportation is severe because loss points of fast ions are away from a port of a fusion device, especially on recent superconducting coils (SC) devices. We have studied these issues on Large Helical Device (LHD) and the signal was successfully transported by approaching an optical fiber close to a scintilator. Plans of lost alpha particle measurement on International Thermonuclear Experimental Reactor (ITER) using these optical techniques are also discussed in this paper.