Abstract
Recent advances in high-intensity laser-produced plasmas have demonstrated their potential as compact charge particle accelerators. Unlike conventional accelerators, transient quasi-static charge separation acceleration fields in laser produced plasmas are highly localized and orders of magnitude larger. Manipulating these ion accelerators, to convert the fast ions to neutral atoms with little change in momentum, transform these to a bright source of MeV atoms. The emittance of the neutral atom beam would be similar to that expected for an ion beam. Since intense laser-produced plasmas have been demonstrated to produce high-brightness-low-emittance beams, it is possible to envisage generation of high-flux, low-emittance, high energy neutral atom beams in length scales of less than a millimeter. Here, we show a scheme where more than 80% of the fast ions are reduced to energetic neutral atoms and demonstrate the feasibility of a high energy neutral atom accelerator that could significantly impact applications in neutral atom lithography and diagnostics.
Highlights
Generating and analyzing a beam of high energy neutral atoms is a challenge that is important for many technological applications[1,2,3]
If the velocity of the projectile is close to the orbital velocity of the bound electron in the target atom, the electron capture cross-section increases
Dielectronic recombination is the process by which the capture of a free electron leads to excitation of a bound electron in the host ion
Summary
Defocusing brings about two crucial changes: (a) the electron temperature of the pre-plasma is lowered dramatically with much smaller changes in electron density, and (b) the average charge states of the accelerated (by the main pulse) Cu ions are expected to be lower as the laser pulse intensity is decreased. The computations show peaks in electron density due to the formation of shock waves driven by the laser pre-pulse leading to a rarefaction wave into the target As ions traverse this plasma profile, neutralization occurs and to fully capture the charge reduction dynamics, we have used the ATOMIC code developed at the Los Alamos National Laboratory, USA. Ions formed at the target surface are accelerated in the sheath electric field and second, electron recombination, dominated by three body recombination, results in charge reduction and neutralization without any significant change in momentum. The emittance of the neutral atom remains the same as the ions and the neutral atoms emanate from a spot of approximately 100 μm diameter (corresponding laser intensity is of the order of 1016 W/cm2), expanding normal to the target in a 15° cone
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