Optimization for deuterium ion acceleration in foam targets by ultra-intense lasers
| Autor: | Wei-Min Wang, G. Shabbir Naz, Z.M. Sheng, M A Bari, Mohammed A. Gondal, M. Salahuddin, J. Zhang, Y.T. Li, M. H. Nasim |
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| Rok vydání: | 2010 |
| Předmět: | |
| Zdroj: | Laser and Particle Beams. 28:333-341 |
| ISSN: | 1469-803X 0263-0346 |
| DOI: | 10.1017/s0263034610000285 |
| Popis: | In this article, we investigate the effects of foam target composition and laser parameters on deuterium ion energy spectrawith particle-in-cell simulations. We findthat localized electrostatic fieldswith multi peaksaroundthe surfaces of lamellarlayersinsidefoamtargetareinduced.Thesefieldsacceleratedeuteriumionsfromthinfoamlayersbyrestrictingtheflowofhot electrons. This mechanism of ion acceleration called as bulk ion acceleration generates large number of high energydeuteriumions. Deuteronsinside foam target are accelerated upto 126 MeVin case ofobliqueoptimal angle of308 whereit is much greater than the normal laser incidence energy of 88 MeV.Keywords: Bulk ion acceleration; Deuteron acceleration; Foam target; Intense laser; Laser-produced plasma INTRODUCTIONWith the achievement of laser intensities well above10 18 Wcm 22 , fast moving ions with kinetic energiesapproaching several tens of MeV have been observed(Clark et al., 2000; Snavely et al., 2000; Hatchett et al.,2000). The striking features of laser-produced ions havealready actuated a broad variety of studies concerning theunderlying physical processes and possible applicationslike proton radiography (Mackinnon et al., 2006), isochoricheating of matter (Patel et al., 2003), and cancer therapy(Malka et al., 2009). The fast ignition concept pertainingto inertial confinement fusion (ICF) also enhances interestsin laser-driven ion acceleration (Tabak et al., 1994; Rothet al., 2001; Eliezer et al., 2007; Hora, 2007; Winterberg,2008; Naumova et al., 2009).In the interaction of femtosecond laser pulses with solidselectron beams are generated and accelerated to highly rela-tivistic energies. The laser pondermotive force pushes thesehot electrons out of the laser focus. The expelled electronsformanelectricfieldattargetfrontsurfaceduetochargesep-aration of electrons and ions. Ions produced at the frontsurface are accelerated inside the target. This mechanism ofion acceleration is called front side acceleration. Fastelectrons also propagate away from laser irradiated surfacetoward the vacuum forming an electrostatic sheath whichresults in ion acceleration in front of the target (Temporalet al., 2002). A significant number of laser-driven hot elec-trons propagate through the target and emerge from targetrear surface. Space-charge separation at target rear surfaceforms an electrostatic filed sufficient for ionizing atoms andcauses strong acceleration of ions along the target normal.This mechanism of ion acceleration is called TargetNormal Sheath Acceleration (TNSA) (Wilks et al., 2001;Brambrink et al., 2006; Limpouch et al., 2008). At moderatelaser intensities, a collisionless electrostatic shock wave isformed in thin foils, which can accelerate ions to highenergy (Chen et al., 2007; Liu et al., 2009). This mechanismof ion acceleration exists widely in space and astrophysicalplasmas. At high laser intensities ( 10 |
| Databáze: | OpenAIRE |
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