Effect of Target Composition on Proton Energy Spectra in Ultraintense Laser-Solid Interactions

Abstract

We study how the proton density in a target irradiated by an ultraintense laser affects the proton spectrum, with analytical models and Vlasov simulations. A low relative proton density gives rise to peaks in the energy spectrum. Furthermore, a target with the protons confined to a thin, low density layer produces a quasimonoenergetic spectrum. This is a simple technique for producing proton beams with a narrow energy spread for proton radiography of laser-plasma interactions.

Laser‐Based Particle Acceleration

“…Similar to the TNSA process at the proton front, the light protons from the low energy part of the spectrum are efficiently accelerated across the carbon boundary by the second sheath field, whereupon they immediately enter the zerofield region and remain in a state of motion of uniform ballistic flow. Note that the potential of charge separation for the spectral modulation of laser-accelerated ion beams had been identified in earlier works already (Tikhonchuk et al, 2005;Robinson et al, 2006). The confined TNSA scheme has been confirmed for the first time experimentally by our group Pfotenhauer et al, 2008).…”

Multispecies plasma expansion into vacuum: The role of secondary ions and suprathermal electrons

“…Interestingly, secondary ions (rather than electrons) have recently been argued to contribute to ultrafast collisional plasma heating by electrostatic shocks [57]. The role of a minority secondary ion population on plasma expansion was investigated earlier in a number of studies [31,[58][59][60][61]. Our work at hand aims at generalizing those earlier models by considering a nonthermal (non-Maxwellian) plasma environment and a finite (arbitrary) admixture of ion components.…”

“…Our work at hand aims at generalizing those earlier models by considering a nonthermal (non-Maxwellian) plasma environment and a finite (arbitrary) admixture of ion components. From first principles, the presence of secondary ions in an expanding plasma is manifested in the appearance of spectral peaks, which are of interest both in experimental diagnostics and for application purposes [31,59]. As a simplifying hypothesis, one may assume that the plasma doesn't change its shape during the expansion process and that there is no charge separation.…”

Controllability of intense-laser ion acceleration

“…On the other hand, ion beams are useful for medical ion cancer therapy, basic particle physics, controlled nuclear fusion, high-energy sources, and so on [1][2][3][4][5][6][7][8][9][10] . The energy of ions, which are accelerated in an interaction between an intense laser pulse and a gas target, is over a few tens of MeV [11][12][13][14][15][16][17][18][19][20][21][22][23][24][25] . The issues in laser ion acceleration include ion beam collimation [10,11,15] , ion energy spectrum control, ion production efficiency [24,25] , ion energy control, and ion beam bunching.…”