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).