Development of a cryogenic hydrogen microjet for high-intensity, high-repetition rate experiments

Abstract

The advent of high-intensity, high-repetition-rate lasers has led to the need for replenishing targets of interest for high energy density sciences. We describe the design and characterization of a cryogenic microjet source, which can deliver a continuous stream of liquid hydrogen with a diameter of a few microns. The jet has been imaged at 1 μm resolution by shadowgraphy with a short pulse laser. The pointing stability has been measured at well below a mrad, for a stable free-standing filament of solid-density hydrogen.

High-intensity laser-accelerated ion beam produced from cryogenic micro-jet target

“…Similar results can be achieved when using any pure gas compatible with the cryogenic source. 13 For instance, a pure deuteron beam has been produced at SLAC National Accelerator Laboratory from a pure deuterium cryogenic target. 16 We notice that maximum proton energy and flux are relatively low compared to what can be obtained using standard metallic foils under identical laser conditions.…”

“…The hydrogen target propagates into vacuum at a velocity of ∼50-100 m/s, thus minimizing the mass loss due to sublimation at the laser interaction point typically located <20 mm away from the nozzle. 13 Ultra-high intensity laser pulses are typically focused to a few to 10 µm focal spot diameter (full width at half-maximum (FWHM)) on a Rayleigh length of a few tens to 100 µm. The limited size of the hydrogen target in two dimensions makes stability and precision of alignment mandatory, especially for a low-shot rate laser system such as Titan.…”

Reaching high flux in laser-driven ion acceleration

“…As such an idealized target, for hole boring, light sail, and Coulomb explosion acceleration we model targets consisting entirely or in parts of a macroscopic layer composed exclusively of hydrogen. As such pure hydrogen targets are challenging to produce at solid densities, we simulate a low target density consistent with novel cryogenic solid hydrogen jet targets [56], which are expected to give major benefits for the operation of laser-proton accelerators and whose operation was already successfully demonstrated [57]. For TNSA, the modeled hydrogen layer on the backside of a low-density target consisting of heavy ions can be realized, e.g., by a natural water vapor contamination on the backside of a foam target [58], homogenized by ionization due to the laser's prepulse.…”

A sensitive EUV Schwarzschild microscope for plasma studies with sub-micrometer resolution

“…2 With each laser-matter interaction requiring a fresh target, this calls for high repetition-rate target delivery such as micrometer-thin liquid or cryogenic jets. Recently, it has been demonstrated that cryogenic hydrogen jets 3 allow for studies of electron-ion equilibration 4 and the generation of pulsed proton beams. [5][6][7] The reliable shot-to-shot characterization of jet thickness, pointing jitter, relative alignment with tiny laser foci and potentially the time-resolved probing of the hydrodynamic plasma expansion, calls for high-resolution a) ulf.zastrau@xfel.eu single-shot imaging with sub-micrometer resolution.…”