A Source of Hard X-rays Based on the Low-Threshold Excitation of Instabilities in a Laser Plasma. II. An Effect of a Laser Prepulse

An investigation is presented of the role of a laser prepulse in the generation of hard X-ray radiation possessing a multispike structure (HXRMS) in the plasma heated by a long pulse of gain-switched CO(2)-laser generation at low intensity pumping radiation (q less than or similar to 10(10) W.cm(-2)). The generation of HXRMS has already been revealed by the authors. In the first part of this work, the authors showed the experimental possibility of applying the principle of low-threshold generation of hard X-ray radiation (HXR) in a single-spike operation resulting from the development of parametric instability in a homogeneous plasma. In this paper, it is shown that the generation of HXRMS increases the HXR yield 10-fold or even more per laser pulse, at the expense of additional spikes in the HXR signal in optimal conditions.