Tokamak Fusion Test Reactor charge exchange atom spectrometry using a natural diamond detector

Abstract

Natural diamond detectors (NDD) developed in Russia were used for fast charge exchange H0 atom spectrometry and flux dynamic measurements during Tokamak Fusion Test Reactor (TFTR) H+ minority ion cyclotron resonance heating (ICRH) experiments in deuterium plasma. For selected NDDs, the high energy resolution (∼2%–3%) and radiation resistance (5×1014 n/cm2) and low sensitivity to neutrons and gammas enable spectrometry of fast (0.2–3 MeV) atoms in TFTR radiation conditions. The NDD compact housing (∼2 cm+3) allowed noninterfering insertion into the particle charge exchange flight tube giving both systems similar views which allows comparison of their spectra and fluxes. A small NDD was chosen to limit count rates to 7×105 s−1. A spectroscopy amplifier operating with pileup inspection at such rates was developed, enabling measurement of the dependence of fast perpendicular proton energy spectra on ICRH heating power during sawtooth-free and sawtooth-crash times. The results agree with a model developed for sawtooth redistribution of fast particles.