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Register a new userNm-sized cryogenic hydrogen clusters for a laser-driven proton source
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A continuous cryogenic hydrogen cluster-jet target has been developed for laser-plasma interaction studies, in particular as a source for the acceleration of protons. Major advantages of the cluster-jet target are the compatibility with pulsed high repetition lasers and the absence of debris. The cluster-jet target was characterized using the Mie-scattering technique allowing to determine the cluster size and to compare it with an empirical prediction. In addition, an estimation of the cluster beam density was performed. The system was implemented at the high power laser system ARCTURUS and first successful measurements show the acceleration of protons after irradiation by high intensity laser pulses with a repetition rate of five Hertz.
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We show efficient laser driven proton acceleration up to 14MeV from a 50 $mu$m thick cryogenic hydrogen ribbon. Pulses of the short pulse laser ELFIE at LULI with a pulse length of $approx$ 350 fs at an energy of 8 J per pulse are directed onto the target. The results are compared to proton spectra from metal and plastic foils with different thicknesses and show a similar good performance both in maximum energy as well as in proton number. Thus, this target type is a promising candidate for experiments with high repetition rate laser systems.
Bright Ar K-shell x-ray with very little background has been generated using an Ar clustering gas jet target irradiated with an 800 mJ, 30 fs ultra-high contrast laser, with the measured flux of 1.1 x 10^4 photons/mrad^2/pulse. This intense x-ray source critically depends on the laser contrast and the laser energy and the optimization of this source with interaction is addressed. Electron driven by laser electric field directly via nonlinear resonant is proved in simulation, resulting in effective electron heating and the enhancement of x-ray emission. The x-ray pulse duration is demonstrated to be only 10 fs, as well as a source size of 20 um, posing great potential application for single-shot ultrafast x-ray imaging.
Owing to the rapid progress in laser technology, very high-contrast femtosecond laser pulses of relativistic intensities become available. These pulses allow for interaction with micro-structured solid-density plasma without destroying the structure by parasitic pre-pulses. This opens a new realm of possibilities for laser interaction with micro- and nano-scales photonic materials at the relativistic intensities. Here we demonstrate, for the first time, that when coupling with a readily available 1.8 Joule laser, a micro-plasma-waveguide (MPW) may serve as a novel compact x-ray source. Electrons are extracted from the walls and form a dense self-organized helical bunch inside the channel. These electrons are efficiently accelerated and wiggled by the waveguide modes in the MPW, which results in a bright, well-collimated emission of hard x-rays in the range of 1~100 keV.
By using multi-dimensional particle-in-cell simulation, we present a new regime of stable proton beam acceleration which takes place when a two-specie shaped foil is illuminated by a circularly polarized laser pulse. It is observed that the lighter protons are nearly-instantaneously separated from the heavier carbon ions due to the charge-to-mass ratio difference. The heavy-ions layer extensively expands in space and acts to buffer the proton layer from the Rayleigh-Taylor-like (RT) instability that would have otherwise degraded the proton beam acceleration. A simple three-interface model is formulated to qualitatively explain the stabilization of the light-ions acceleration. Due to the absence of the RT-like instability, the produced high quality mono-energetic proton bunch can be well maintained even after the laser-foil interaction concludes.
We report a laser-driven neutron source with high yield ($>10^8$/J) and high peak flux ($>10^{25}$/cm$^2$/s) derived from high-temperature deuteron-deuteron fusion reactions. The neutron yield and the fusion temperature ($sim 200$ keV) in our experiment are respectively two orders of magnitude and one order of magnitude higher than any previous laser-induced D-D fusion reaction. The high-temperature plasma is generated from thin ($sim 2,mu$m), solid-density deuterium targets, produced by a cryogenic jet, irradiated by a 140 fs, 130 J petawatt laser with an F/3 off-axis parabola and a plasma mirror achieving fast volumetric heating of the target. The fusion temperature and neutron fluxes achieved here suggest future laser experiments can take advantage of neutrons to diagnose the plasma conditions and come closer to laboratory study of astrophysically-relevant nuclear physics.
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