Content area
Abstract
Products of fusion reactions have been used to diagnose fusion plasmas in TFTR and PLT.
In TFTR, pellet injection was used to determine time evolution of the triton tail present after neutral beam injection into low-density plasmas. Results show that for some plasmas, after the beam-injected deuterium ions have slowed down, the neutron emission can be dominated by the burnup of fusion-produced tritons.
Neutron emission transients seen at the onset of the q-mode were studied and determined to be caused by an increase in the deuterium density at the transition. The subsequent decrease in electron temperature then led to a reduced neutron emission.
A study of neutron sawteeth during neutral beam heating on TFTR was done to determine the effect of sawteeth on fast ion confinement. The neutron emission was observed to drop on a time scale of a few tens to a few hundred microseconds. The magnitude of the drop scaled with the sawtooth period and depended on $q\sb{c}$.
A method for measuring the birth profile of alpha particles in a tokamak using solid state nuclear track detectors was developed and used to make the first measurements of escaping alpha particles from a tokamak. The results show that during ICRH heating, the birth distribution of the alphas is peaked at the resonance layer and not necessarily at the center of the plasma.
The feasibility of measuring the products of fusion reactions in coincidence was evaluated. Initial tests of the method were performed using reactions between beam deuterium ions and the background gas in the neutralizer region of a TFTR neutral beam. No coincidences were detected indicating the difficulty of measuring the neutron and $\sp{3}$He ion in coincidence, due mostly to problems in sufficiently collimating the neutrons.
An experiment to measure the diffusion of electron-mass particles by depositing positrons in a plasma by ionization of a positronium beam was simulated taking into account the relevant atomic physics of positronium. In this experiment, the diffusion of the positrons to the limiters would be monitored by measuring the 511-keV annihilation radiation as the positrons annihilated in the limiters.
