Improving the efficiency of a thermonuclear DD reaction in a femtosecond laser plasma using structured low-average-density targets

An increase in the yield of fast neutrons is experimentally demonstrated by exciting a nuclear DD reaction in the interaction of a relativistically intense (over 1018 W cm-2) ultrashort laser pulse with a deuterated low-average-density target volume-structured at the wavelength scale. It is shown that decreasing the average target density from 0.78 to 0.35 g cm-3 doubles the neutron flux, which reaches 7 × 104 particles per 1 J of input energy. The effect may be associated with an increase in the number of accelerated deuterium ions due to the three dimensional expansion of individual elements of the target structure.