Bulletin of the American Physical Society
2005 APS April Meeting
Saturday–Tuesday, April 16–19, 2005; Tampa, FL
Session X4: Beam-Plasma Interactions and Applications |
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Sponsoring Units: DPP DPB Chair: Ronald Williams, Florida A&M Room: Marriott Tampa Waterside Grand Salon C/D |
Tuesday, April 19, 2005 10:45AM - 11:21AM |
X4.00001: Explosions of Femtosecond Laser Irradiated Heteronuclear Clusters Invited Speaker: In recent years, there has been quite substantial progress in the understanding of explosions of atomic clusters subject to intense laser irradiation. It is now well understood that single species clusters of low Z materials (such as hydrogen or deuterium) expand by a Coulomb explosion if they are irradiated with enough intensity. In this case, if irradiated with a pulse of sufficiently fast rise time and sufficiently high intensity to eject all free electrons from the cluster, the ejected ion energies will be simply the potential energy of the ions after ionization at their equilibrium position in the cluster. The picture is not as simple if the cluster contains a mixture of species, as occurs in a heteronuclear cluster such as a CH$_{4}$ or CD$_{4}$ cluster. Last and Jortner have studied numerically the explosions of such heteronuclear clusters and find that a dynamic enhancement of the light ions can occur [\textit{Phys. Rev. Lett}. \textbf{87}, 033401 (2001)]. We have experimentally studied this process by comparing the ion energies from laser irradiated methane and deuterated methane clusters. We find that the protons ejected from CH$_{4}$ clusters, irradiated by 35 fs pulses at intensity up to 10$^{18}$ W/cm$^{2}$ exhibit a higher energy than deuterons ejected from otherwise identically sized CD$_{4}$ clusters. This is consistent with the theory of Last and Jortner and promises to impact laser driven exploding cluster fusion experiments in the future. [Preview Abstract] |
Tuesday, April 19, 2005 11:21AM - 11:57AM |
X4.00002: Formation of Strong Shocks by Laser Pulses Invited Speaker: Ultra intense lasers ($ I > 10^{20} W/cm^2$) open a new path for the exploration of extreme scenarios. Laser matter interactions in this relativistic regime provide an excellent setting to test mechanisms present not only in the laboratory but also in astrophysical scenarios. Due to the nonlinear nature of the phenomena, massively parallel particle-in-cell simulations provide the ideal tool for exploration. I will examine the formation of strong shocks, and proton shock acceleration, in two scenarios: overdense targets, and clustered gases. The formation of high Mach number electrostatic shocks by laser pulses incident on overdense plasma slabs is observed, for a wide range of conditions. The shocks propagate undisturbed across the plasma, accelerating the protons to energies up to $300 \, \mathrm{MeV}$, with a clear signature in the ion spectrum. Shock structures can also be driven in the explosion of very large deuterium clusters. Small-scale shock shells in the expanding ion cloud are observed, and a technique to induce the formation of large shock shells inside a single cluster (increasing the probability of intra-cluster nuclear reactions) is proposed, and demonstrated. The possibility to control the shock dynamics is explored, allowing for the detailed study of the shock formation mechanisms, and ion shock acceleration. [Preview Abstract] |
Tuesday, April 19, 2005 11:57AM - 12:33PM |
X4.00003: Energy Gain Greater than 1GeV in Beam Driven Plasma Wakefield Accelerator Invited Speaker: |
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