Cryogenic sheet jet targets produced from liquid hydrogen for high repetition rate experiments

Cryogenic jet targets are attracting growing attention in scientific fields investigated at x-ray free electron laser and high power laser facilities, e.g. in high energy density science exploring extreme states of matter or in relativistic laser plasma interactions aiming to develop novel ion accelerators.
A key advantage of cryogenic target is the unique capability to deliver ultra-pure samples at solid density using chemical elements that under ambient conditions exist in the gas phase (e.g. hydrogen) and to generate replenishing, free-standing, debris free targets at high repetition rates.
Novel sheet-like jets geometries enable wider target with adjustable thickness, which is e.g. of interest for the study of different acceleration mechanisms in laser-plasma experiment.
In this talk, we present experimental studies on the characterization of sheet jets for different nozzle types and under various operation conditions. Unlike cylindrical geometries, the shape of the planar target is significantly altered by surface tension until the liquid motion is stopped by solidification. The underlining fluid dynamics and thermodynamics are discussed and compared with computational fluid dynamic simulations.