Abstract
The magnitude of a fusion reaction rate in a plasma depends strongly on the relative energy of the reacting plasma ions and less strongly on the ion number density. The ratio of two reaction rates, however, is less dependent on the relative velocities while retaining the linear dependence on the relative densities of the plasma ion species. In this manner, the ratio of t(d,n)α to d(d,n) 3He fusion reactions depends only on the ratio nt/nd, so that tritium levels in a deuterium plasma can be determined from the d–t/d–d reaction ratio (nd ≂ne). Similarly, the density of 3He can be determined in a deuterium plasma from the ratio of 3He (d, p)α to d(d,n) 3He fusion reactions. Such measurements of the 3He density are of interest since they relate to the alpha ash removal problem expected on a tokamak reactor.
Highlights
Determination of the particle transport, edge recycling, and convective heat flow of a plasma all require measurement of the plasma ion density
Nuclear techniques are reviewed which make use of the d (d,n) 3He, 3He(d, p)a, and t (d,n)a fusion reactions to measure the densities of deuterium, 3He, and tritium
When these nuclear techniques are applicable they have the advantages of using naturally occurring emissions from the plasma, of allowing good time resolution, and of preferentially detecting emissions from the plasma center. Initial applications of these nuclear techniques on the PLT and PDX tokamaks at Princeton include: (I) Determination of the deuterium density in discharges that follow a switch in the plasma working gas from deuterium to hydrogen
Summary
Determination of the particle transport, edge recycling, and convective heat flow of a plasma all require measurement of the plasma ion density. Nuclear techniques are reviewed which make use of the d (d,n) 3He, 3He(d, p)a, and t (d,n)a fusion reactions to measure the densities of deuterium, 3He, and tritium When these nuclear techniques are applicable they have the advantages of using naturally occurring emissions from the plasma (and are, nonperturbative), of allowing good time resolution, and of preferentially detecting emissions from the plasma center. (I) Determination of the deuterium density in discharges that follow a switch in the plasma working gas from deuterium to hydrogen These measurements indicate the fraction of plasma ions contributed by recycled gas and the rate of removal of deuterium from the vacuum vessel. (3) Planned determination of the tritium density following laser blow-off injection of trace quantities of tritium This experiment would be useful for determining tritium transport coefficients as well as for predicting the tritium inventory in d-t machines
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