Author/Authors :
Gatu Johnson، نويسنده , , M. and Giacomelli، نويسنده , , L. and Hjalmarsson، نويسنده , , A. and Kنllne، نويسنده , , J. and Weiszflog، نويسنده , , M. and Andersson Sundén، نويسنده , , E. and Conroy، نويسنده , , S. and Ericsson، نويسنده , , G. and Hellesen، نويسنده , , C. and Ronchi، نويسنده , , E. and Sjِstrand، نويسنده , , H. and Gorini، نويسنده , , G. and Tardocchi، نويسنده , , M. and Combo، نويسنده , , A. and Cruz، نويسنده , , S. N. de Sousa، نويسنده , , J. and Popovichev، نويسنده , , S.، نويسنده ,
Abstract :
A time-of-flight (TOF) spectrometer for measurement of the 2.5-MeV neutron emission from fusion plasmas has been developed and put into use at the JET tokamak. It has been optimized for operation at high rates (TOFOR) for the purpose of performing advanced neutron emission spectroscopy (NES) diagnosis of deuterium plasmas with a focus on the fuel ion motional states for different auxiliary heating scenarios. This requires operation over a large dynamic range, including high rates of >100 kHz with a maximum value of 0.5 MHz for the TOFOR design. This paper describes the design principles and their technical realization. The performance is illustrated with recent neutron TOF spectra recorded for plasmas subjected to different heating scenarios. A true event count rate of 39 kHz has been achieved at about a tenth of the expected neutron yield limit of JET, giving a projected maximum of 400 kHz at peak JET plasma yield. This means that the count rate capability for NES diagnosis of D plasmas has been improved more than an order of magnitude. Another important performance factor is the spectrometer bandwidth, where data have been acquired and analyzed successfully with a response function for neutrons over the energy range 1 to >5 MeV. The implications of instrumental advancement represented by TOFOR are discussed.
