Neutron production by 200 mJ ultrashort laser pulses

We report the observation of neutrons released from d(d,n)³He fusion reactions in the focus of 200 mJ, 160 fs Ti:sapphire laser pulses on a deuterated polyethylene target. Optimizing the fast electron and ion generation by applying a well-defined prepulse led to an average rate of 140 neutrons per shot. Furthermore, the production of a substantial number of MeV {γ} rays could be observed. The occurrence of neutrons and {γ} rays is attributed to the formation and explosion of a relativistic plasma channel in the laser focus, which is confirmed by numerical calculations.