FAST PARTICLE DIAGNOSTICS AT JET: STATUS AND PLANS

摘要

A comprehensive set of fast particle diagnostics is routinely used at JET. Some are in the process of being upgraded and others, completely new, are being prepared for use during the forthcoming tritium experiments. For fusion product studies, the strength and profile of the charged particle birth distribution is obtained by measuring the neutron emission with three pairs of absolutely calibrated fission chambers and a two-camera profile monitor. Information on the DD neutron energy spectrum is deduced from a time-of-flight neutron spectrometer. Neutrons of 14 MeV energy from triton burnup are measured using silicon diodes and a high energy branch of the profile monitor. Absolute calibration is obtained with an activation system. A prototype lost alpha particle detector (Faraday cup) has been tested in the laboratory and has been installed inside JET so that its noise immunity can be tested. Two 14 MeV neutron spectrometers are under commissioning and a third is under construction. A high energy neutral particle analyser is routinely used to diagnose fast RF driven particles and will also be available for alpha particle studies. The intensity of RF driven fast particles is also deduced by the spectroscopy of gamma rays emitted in reactions with impurity ions in the plasma. The gamma ray measuring branch of the neutron profile monitor adds spatial resolution to the measurement. A new antenna for measuring ion cyclotron emission (ICE) and a gyrotron for alpha particle scattering experiments are in the process of being commissioned. Active charge exchange spectroscopy to investigate the low energy range of the alpha particle population is being considered. Where appropriate, information gathered with these systems is presented to illustrate their performance.