# High repetition rate (>= kHz) targets and optics from liquid microjets for the study and application of high intensity laser-plasma interactions

## TL;DR

This paper introduces liquid microjets as high-repetition-rate targets and optics for laser-plasma interactions, enabling high-power applications with minimal debris and precise control.

## Contribution

It presents a novel nozzle assembly for generating liquid microjets compatible with high repetition rates and demonstrates a liquid sheet plasma mirror with high reflectivity at 1 kHz.

## Key findings

- Liquid microjets produce minimal debris and are precisely controllable.
- A liquid sheet plasma mirror achieves 69% reflectivity at 1 kHz.
- Estimated maximum repetition rate exceeds 10 kHz.

## Abstract

High intensity laser-plasma interactions produce a wide array of energetic particles and beams with promising applications. Unfortunately, high repetition rate and high average power requirements for many applications are not satisfied by the lasers, optics, targets, and diagnostics currently employed. Here, we address the need for high repetition rate targets and optics through the use of liquids. A novel nozzle assembly is used to generate high-velocity, laminar-flowing liquid microjets which are compatible with a low-vacuum environment, generate little to no debris, and exhibit precise positional and dimensional tolerances. Jets, droplets, submicron thick sheets, and other configurations are characterized with pump-probe shadowgraphy to evaluate their use as targets. To demonstrate a high repetition rate, consumable liquid optical element, we present a plasma mirror created by a submicron thick liquid sheet. This plasma mirror provides etalon-like anti-reflection properties in the low-field of 0.1% and high reflectivity as a plasma, 69%, at a repetition rate of 1 kHz. Practical considerations of fluid compatibility, in-vacuum operation, and estimates of maximum repetition rate, in excess of 10 kHz, are addressed. The targets and optics presented here enable the use of relativistically intense lasers at high average power and make possible many long proposed applications.