Temperature Measurements of Fusion Plasmas Produced by Petawatt-Laser-Irradiated D2-3He or CD4-3He Clustering Gases

Two different methods have been employed to determine the plasma temperature in a laser-cluster fusion experiment on the Texas Petawatt laser. In the first, the temperature was derived from time-of-flight data of deuterium ions ejected from exploding D-2 or CD4 clusters. In the second, the temperature was measured from the ratio of the rates of two different nuclear fusion reactions occurring in the plasma at the same time: D(d, He-3)n and He-3(d, p)He-4. The temperatures determined by these two methods agree well, which indicates that (i) the ion energy distribution is not significantly distorted when ions travel in the disassembling plasma; (ii) the kinetic energy of deuterium ions, especially the "hottest part" responsible for nuclear fusion, is well described by a near-Maxwellian distribution.