Collisionless shock acceleration of narrow energy spread ion beams from mixed species plasmas using 1  μm lasers

Abstract

Collisionless shock acceleration of protons and C 6+ ions has been achieved by the interaction of a 10 20 W/cm 2 , 1 µm laser with a near-critical density plasma. Ablation of the initially solid density target by a secondary laser allowed for systematic control of the plasma profile. This enabled the production of beams with peaked spectra with energies of 10-18 MeV/a.m.u. and energy spreads of 10-20% with up to 3x10 9 particles within these narrow spectral features. The narrow energy spread and similar velocity of ion species with different charge-to-mass ratio are consistent with acceleration by the moving potential of a shock wave. Particle-in-cell simulations show shock accelerated beams of protons and C 6+ ions with energy distributions consistent with the experiments. Simulations further indicate the plasma profile determines the trade-off between the beam charge and energy and that with additional target optimization narrow energy spread beams exceeding 100 MeV/a.m.u. can be produced using the same laser conditions.

Collisionless shock acceleration of quasimonoenergetic ions in ultrarelativistic regime

“…The energy per carbon ion without radiation reaction is 324 MeV (27 MeV/u) with an energy spread (∆E/E) of about 4% at FWHM (full-width at half-maximum), while accounting for the RR force and pair plasma formation, it drops to 192 MeV (∼ 16 MeV/u) with 2.5% FWHM , and 168 MeV (∼ 14 MeV/u) with 2% FWHM, respectively. The obtained energies are similar to ones obtained recently at lower laser intensity but with higher energy spread [28]. The FWHM of the ion energy spectra become better on accounting for the RR force and PP production, which is extremely encouraging.…”

“…This scheme has also attracted significant attention as the formation dynamics of the collisionless shocks in laser-plasma interaction constitutes an important part of the newly developing area of research known as the laboratory astrophysics [29]. From the point of view of the laser-driven ion acceleration, the ion acceleration from electrostatic shocks in near-critical density plasmas is shown to provide a high-energy ion beam with a low energy spread [22,24,28,30].…”

High-flux high-energy ion beam production from stable collisionless shock acceleration by intense petawatt-picosecond laser pulses

“…Note that the near-critical plasma is now available via either using foams [38], cryogenic hydrogen microjet target [39], high-pressure gas jets [40] or exploding an ultrathin foil with nanosecond lasers [41]. We also notice that, very recently, a experiment using high-intensity 1 μm wavelength laser have successfully demonstrated the ability of CSA to efficiently accelerate ions with high yield and narrow distributions [42], where the ion energy (15-20 MeV) and particle number (3×10 9 ) in a 10 % energy width is comparable to the best results obtained experimentally by any other mechanism, including TNSA. However, we think it can be further improved by better resolving the above issues of upstream heating and transverse expansion.…”

Enhancement of collisionless shock ion acceleration by electrostatic ion two-stream instability in the upstream plasma

“…CSA experiments using a linearly polarized CO 2 laser with near-N cr gas-jet targets produced 20 MeV proton beam [15]. A number of experiments have been carried out over the last few years to understand and characterize ion acceleration via CSA [16][17][18][19][20][21]. One aspect of CSA that is currently not well understood for accelerating mono-energetic ions to high energies is the effect of the target material used.…”