We propose a plasma channel scheme to obtain an improved table-top laser driven fusion neutron yield as a result of explosions of large deuterium clusters irradiated by an intense laser pulse. A cylindrical plasma channel is created by two moderate intensity laser prepulses at the edge of a deuterium cluster jet along which an intense main laser pulse propagates several nanoseconds later. With the aid of this plasma channel, the main laser pulse will be allowed to deposit its energy into the central region of the deuterium gas jet where the cluster sizes are larger and the atomic density is higher. The plasma channel formation and its impact on the deuterium ion energy spectrum and the consequent fusion neutron yield have been investigated. The calculated results show that a remarkable increase of the table-top laser driven fusion neutron yield would be expected.
The pure Coulomb explosions of the methane clusters (CA4)n, (light atom A = H or D) have been investigated by a simplified electrostatic model for both a single cluster and an ensemble of clusters with a given cluster size distribution. The dependence of the energy of ions produced from the explosions on cluster size and the charge state of the carbon ions has been analysed. It is found that, unlike the average proton energy which increases with the charge q of the carbon ions, the average deuteron energy tends to saturate as q becomes larger than 4. This implies that when the laser intensity is sufficiently high for the (CD4)n to be ionized to a charge state of (C4+D+4)n, the neutron yield from a table-top laser-driven Coulomb explosion of deuterated methane clusters (CD4)n could be increased significantly by increasing the interaction volume rather than by increasing the laser intensity to produce the higher charge state (C6+D+4)n. The flight-time spectra of the carbon ions and the light ions have also been studied.Print publication: Issue 10 (28 May 2008)Received 2 November 2007, in final form 14 April 2008Published 6 May 2008