34 research outputs found
Design of plasma shutters for improved heavy ion acceleration by ultra-intense laser pulses
In this work, we investigate the application of the plasma shutters for heavy
ion acceleration driven by a high-intensity laser pulse. We use
particle-in-cell (PIC) and hydrodynamic simulations. The laser pulse,
transmitted through the opaque shutter, gains a steep-rising front and its peak
intensity is locally increased at the cost of losing part of its energy. These
effects have a direct influence on subsequent ion acceleration from the
ultrathin target behind the shutter. In our 3D simulations of silicon nitride
plasma shutter and a silver target, the maximal energy of high-Z ions increases
significantly when the shutter is included for both linearly and circularly
polarized laser pulses. Moreover, application of the plasma shutter for
linearly polarized pulse results in focusing of ions towards the laser axis in
the plane perpendicular to the laser polarization. The generated high energy
ion beam has significantly lower divergence compared to the broad ion cloud,
generated without the shutter. The effects of prepulses are also investigated
assuming a double plasma shutter. The first shutter can withstand the assumed
sub-ns prepulse (treatment of ns and ps prepulses by other techniques is
assumed) and the pulse shaping occursvia interaction with the second shutter.
On the basis of our theoretical findings, we formulated an approach towards
designing a double plasma shutter for high-intensity and high-power laser
pulses and built a prototype.Comment: 30 pages 13 figure
Evidence of resonant surface wave excitation in the relativistic regime through measurements of proton acceleration from grating targets
The interaction of laser pulses with thin grating targets, having a periodic
groove at the irradiated surface, has been experimentally investigated.
Ultrahigh contrast () pulses allowed to demonstrate an enhanced
laser-target coupling for the first time in the relativistic regime of
ultra-high intensity >10^{19} \mbox{W/cm}^{2}. A maximum increase by a factor
of 2.5 of the cut-off energy of protons produced by Target Normal Sheath
Acceleration has been observed with respect to plane targets, around the
incidence angle expected for resonant excitation of surface waves. A
significant enhancement is also observed for small angles of incidence, out of
resonance.Comment: 5 pages, 5 figures, 2nd version implements final correction
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Controllable Laser Ion Acceleration
In this paper a future laser ion accelerator is discussed to make the laser-based ion accelerator compact and controllable. Especially a collimation device is focused in this paper. The future laser ion accelerator should have an ion source, ion collimators, ion beam bunchers, and ion post acceleration devices [Laser Therapy 22, 103(2013)]: the ion particle energy and the ion energy spectrum are controlled to meet requirements for a future compact laser ion accelerator for ion cancer therapy or for other purposes. The energy efficiency from the laser to ions is improved by using a solid target with a fine sub-wavelength structure or a near-critical density gas plasma. The ion beam collimation is performed by holes behind the solid target or a multi-layered solid target. The control of the ion energy spectrum and the ion particle energy, and the ion beam bunching would be successfully realized by a multistage laser-target interaction
Monoenergetic ion beams from ultrathin foils irradiated by ultrahigh-contrast circularly polarized laser pulses
Acceleration of ions from ultrathin foils irradiated by intense circularly polarized laser pulses is investigated using one- and two-dimensional particle simulations. A circularly polarized laser wave heats the electrons much less efficiently than the wave of linear polarization and the ion acceleration process takes place on the front side of the foil. The ballistic evolution of the foil becomes important after all ions contained in the foil have been accelerated. In the ongoing acceleration process, the whole foil is accelerated as a dense compact bunch of quasineutral plasma implying that the energy spectrum of ions is quasimonoenergetic. Because of the ballistic evolution, the velocity spread of an accelerated ion beam is conserved while the average velocity of ions may be further increased. This offers the possibility to control the parameters of the accelerated ion beam. The ion acceleration process is described by the momentum transfer from the laser beam to the foil and it might be fairly efficient in terms of the energy transferred to the heavy ions even if the foil contains a comparable number of light ions or some surface contaminants. Two-dimensional simulations confirm the formation of the quasimonoenergetic spectrum of ions and relatively good collimation of the ion bunch, however the spatial distribution of the laser intensity poses constraints on the maximum velocity of the ion beam. The present ion acceleration mechanism might be suitable for obtaining a dense high energy beam of quasimonoenergetic heavy ions which can be subsequently applied in nuclear physics experiments. Our simulations are complemented by a simple theoretical model which provides the insights on how to control the energy, number, and energy spread of accelerated ions
Laser ion acceleration in a mass limited targets
Laser interactions with mass-limited targets (MLT) are studied via 2D3V relativistic electromagnetic PIC simulations. Analytical estimates are derived to clarify the simulation results. MLT limit undesirable spread of absorbed laser energy out of the interaction zone. MLT, such as droplets, are shown here to enhance the achievable fast ion energy significantly. For given target dimensions, the existence is demonstrated of an optimum laser beam diameter when ion acceleration is efficient and geometrical energy losses are still acceptable. Ion energy also depends on target geometrical form and shaped targets are found to be preferable for high ion energy
Laser ion acceleration in a mass limited targets
Laser interactions with mass-limited targets (MLT) are studied via 2D3V relativistic electromagnetic PIC simulations. Analytical estimates are derived to clarify the simulation results. MLT limit undesirable spread of absorbed laser energy out of the interaction zone. MLT, such as droplets, are shown here to enhance the achievable fast ion energy significantly. For given target dimensions, the existence is demonstrated of an optimum laser beam diameter when ion acceleration is efficient and geometrical energy losses are still acceptable. Ion energy also depends on target geometrical form and shaped targets are found to be preferable for high ion energy