RECENT EXPANSION OF THE TFTR MULTICHANNEL NEUTRON COLLIMATOR

Radial neutron emission profiles from TFTR DT plasmas are generally na rrow and highly peaked. In the past, the neutron profile monitor provi ded inadequate coverage of the plasma core for these peaked profiles. Four new sight Lines were added to improve the view in the central reg ion and better evaluate parameters such as global neutron yields and n eutron peakedness and to localize neutron MHD activity. The new sightl ines utilize plastic scintillators instead of the original ZnS based N E451 detectors. These new detectors have larger volumes and increased solid angles as compared to the NE451 detectors in order to increase t he incident neutron flux, in order to reduce statistical ''shot noise' ' on the signal traces and improve the frequency response. The increas ed detection capabilities along with recent upgrades in the fast ampli fiers and wave form digitizers have extended the frequency response to >50 kHz which allows the study of high frequency MI-ID activity. Data from DT plasmas illustrating the enhanced spatial and temporal resolu tion with the new channels are presented. (C) 1997 American Institute of Physics.