The first magnetic proton recoil type neutron spectrometer has been put to
use for diagnosing tokamak plasmas of high neutron yield rates (the range Y
-n = 10(15)- 6 x 10(18) n/s). The spectrometer principles along with the di
agnostic installation are presented. Performance and diagnostic capabilitie
s are illustrated based on results obtained at Joint European Torus. The im
plications for neutron spectrometry diagnostics on the next step tokamak fo
r burning plasmas (Y-n --> 10(22) n/s) are discussed. (C) 1999 American Ins
titute of Physics. [S0034-6748(99)59401-X].