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 targets 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.
Sheet jets in particular, due to their extended width and an adjustable thickness, are of special interest for parametric studies, e.g. the investigation of different acceleration mechanisms in laser driven plasmas.
In this talk, we present experimental studies on the characterization of hydrogen sheet jets ejected from split nozzles under various operation conditions. The jet, which forms leafed sheets altered by the surface tension, solidifies within a millimeter due to strong evaporative cooling upon which the sheet width and thickness is conserved further downstream yielding constant target conditions. The respective fluid dynamic and thermodynamic behaviour is discussed and compared with computational fluid dynamic simulations.
Understanding of the flow and the solidification of free-flowing liquids will help to design specialized nozzles for the generation of jet targets with tailorable parameters.