Experiments on the interaction of fast heavy ions with a laser-plasma target
ABSTRACT We have experimentally investigated the stopping power of a laser-ablated carbon plasma tested with a 225 keV/u oxygen beam. A dense plasma target was produced by irradiation of a graphite rod with a Q-switched Nd–glass laser. We have developed a diagnostics system for the target plasma using laser interferometry. The motion of the fringes was observed by a streak camera in order to obtain time-dependent electron density profiles. The maximum areal electron density of the carbon plasma reached nel=1×1018 cm−2. For the measurement of the energy loss of ions in the target, we developed a time-resolved magnetic spectrometer system with a plastic scintillator and an MCP. Using a streak camera we measured the shift of the beam spot on the MCP. The stopping power observed 40 ns after the laser was fired was 15 MeV/(mg/cm2). This value is enhanced by 50% compared to that in the cold equivalent.
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ABSTRACT: The basic physics of nonrelativistic and electromagnetic ion stopping in hot and ionized plasma targets is thoroughly updated. Corresponding projectile-target interactions involve enhanced projectile ionization and coupling with target free electrons leading to significantly larger energy losses in hot targets when contrasted to their cold homologues. Standard stoppping formalism is framed around the most economical extrapolation of high velocity stopping in cold matter. Further elaborations pay attention to target electron coupling and nonlinearities due to enhanced projectile charge state, as well. Scaling rules are then used to optimize the enhanced stopping of MeV/amu ions in plasmas with electron linear densities nel ~ 10 18 -10 20 cm -2 . The synchronous firing of dense and strongly ionized plasmas with the time structure of bunched and energetic multicharged ion beam then allow to probe, for the first time, the long searched enhanced plasma stopping and projectile charge at target exit. Laser ablated plasmas (SPQR1) and dense linear plasma columns (SPQR2) show up as targets of choice in providing accurate and on line measurements of plasma parameters. Corresponding stopping results are of a central significance in asserting the validity of intense ion beam scenarios for driving thermonuclear pellets. Other applications of note feature thorium induced fission, novel ion sources and specific material processing through low energy ion beams. Last but not least, the given ion beam-plasma target interaction physics is likely to pave a way to the production and diagnostics of warm dense matter (WDM).The Open Plasma Physics Journal 01/2010; 3:88-115.
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ABSTRACT: We tested an experimental setup for measurement of non-linear stopping of low-energy heavy ions in non-ideal plasmas. In this setup, we used a silicon surface-barrier charged-particle detector (SSBD), which could measure the energy of single ions. For synchronization between the plasma production and the injection of single projectiles, a fast beam kicker was installed in front of the plasma target. In order to test this setup, we used a laser-produced polyethylene plasma target instead of a shock-driven plasma device, which is under R&D process. Results of a preliminary energy loss measurement for low-speed heavy ions in the laser plasma are reported. Performance on the time resolution evaluated by using a carbon-foil target is also presented.Progress in Nuclear Energy. 01/2008;