Neutron spectrometry for plasma rotation

The principles of neutron spectrometry for determination of the toroidal rotation velocity (V-t) of the plasma in tokamaks are discussed. Comparison is made with photon spectroscopy which shows that neutron spectroscopy can be used as a rotation diagnostic and that its applicability depends on the availability of high neutron fluxes and the development of methods to measure the neutron energy with very high precision. It is found that neutron spectroscopy could be a feasible rotation diagnostic for burning fusion plasmas to be produced in the next generation tokamaks such as ITER. It is' proposed that V-t should be derived from the difference spectrum obtained from the simultaneous measurement of neutrons emitted tangentially in two opposite directions. The problems connected with the calibration and stability requirements on the neutron spectrometer system for V-t measurements are illustrated and possible technical solutions discussed. (C) 1997 American Institute of Physics.