Tokamak Fusion Test Reactor neutron source strength measurements instrumentation and results

The Tokamak Fusion Test Reactor (TFTR) at Princeton University has been designed 1) to reach power break-even, Q approx. = 1 (Q = fusion power/heating power), in neutral-beam-injected, two-energy-component D-T plasmas, where the density confinement time requirement is less stringent than that for maxwellian, one-energy-component plasmas, and 2) to provide the physics understanding of reactor-like plasmas required for the development of tokamak reactors. TFTR has now been in operation for more than two years. Nearly 15,000 individual high power plasma discharges have been produced. Deuterium plasmas with ohmic heating currents up to 2.5 MA, deuterium neutral beam injection (NBI) with beam powers up to 6.3 MW (28 MW projected for 1986) and 80 KeV energy (120 KeV projected), deuterium pellet injection and adiabatic deuterium plasma compression have been investigated. The neutron source strength of a fusion plasma is a direct indicator of the fusion power generated. However, its measurement is complicated for a number of reasons. 1) The neutron source is extended and time varying. 2) It is surrounded by large, fixed scatterers near both source and detectors. 3) The dynamic range of interest in present experiments covers some ten orders of magnitude. In Section II the authors discuss briefly the plasma, its properties, the detectors, their useful ranges and limitations and their calibration. Section II contains some of the neutron measurement results obtained so far