MPR Neutron Spectrometry at JET and its Next Step Implications

Abstract

The first MPR (magnetic proton recoil) spectrometer for fusion neutron measurements has been constructed and recently installed in a diagnostic system at the Joint European Torus (JET) of EURATOM. The MPR on JET experiment1 has been in production operation since December 1996 and is used to measure the neutron emission from plasmas of both pure deuterium (D) and mixed deuterium-tritium (DT). The objectives are to perform plasma diagnostic studies and to exploit the unique characteristics of the new technique to push back the observational limits of fusion neutron spectrometry. At the same time, it is important to acquire operating experience and to check the diagnostic performance as projected from instrumental specifications against the results obtained. The latter is motivated by the need for input to the ongoing work on the new generation neutron diagnostics for the next step fusion experiments entailing burning plasmas with high neutron fluxes2. In this perspective, the MPR on JET experiment, which will be discussed here, represents neutron spectrometry under flux conditions approaching those of pre-ignition plasmas. As the MPR method can be used with enhanced performance also at the highest fluxes foreseen for burning tokamak plasmas3,4, the results are relevant for the diagnostic planning for the International Thermonuclear Experimental Reactor (ITER).