Yield of D-D and D-3He fusion reactions produced by the interaction of intense ultrafast laser pulses with molecular clusters, M. Barbui,  Cyclotron Institute, Texas A&M University, College Station, Texas USA − The interaction of intense ultrafast laser pulses with molecular clusters produces a Coulomb explosion of the clusters. In this process, the positive ions from the clusters might gain enough kinetic energy to drive nuclear reactions [1-3].  The ratio of the yields of two reactions, with different cross section, occurring simultaneously can be used to determine the average temperature of the ions at the time when the reactions occurred.

A first experiment to measure the yield of D-D and D-3He fusion reactions was performed at University of Texas Center for High Intensity Laser Science.  Laser pulses of energy ranging from 100 to 180 J and duration 150fs were delivered by the Petawatt laser. The experiment was divided in two parts.  In the first part, pure D2 clusters were used to optimize the yield of the D(D,n) 3He and D(D,p)T fusion reactions.  The temperature of the energetic deuterium ions was measured using a Faraday cup, whereas the yields of the D-D reactions were measured by detecting the characteristic 2.45 MeV neutrons and 3.02 MeV protons.  In the second part, different concentrations of D2 and 3He or CD4 and 3He were mixed in the gas jet target to allow the simultaneous measurement of 3He (D,p) 4He and D-D reactions.  The 2.45 MeV neutrons from the D(D,n) 3He  reaction were measured as well as the 14.7 MeV protons from the 3He(D,p) 4He reaction.  The Farday cup measurement showed no evidence of energetic 3He ions, suggesting that the clusters were made of D2 molecules and the 3He was in the surrounding gas.  We compared the temperature of the ions measured with the Faraday cup with the effective temperature obtained from the ratio of the yields assuming that the fast D ions interact with 3He at rest.  The preliminary results will be shown.

 

[1] T. Ditmire, J. Zweiback, V. P. Yanovsky, T. E. Cowan, G. Hays, and K. B. Wharton, Nature 398, 489 (1999).

[2] J. Zweiback, R. A. Smith, T. E. Cowan, G. Hays, K. B. Wharton, V.P. Yanovsky, and T. Ditmire, Phys. Rev. Lett. 84, 2634 (2000).