Characterization of discharge capillaries via benchmarked hydrodynamic plasma simulations

TL;DR

This paper presents validated hydrodynamic plasma simulations of discharge capillaries, offering insights into plasma formation, energy deposition, and potential measurement challenges for improved plasma accelerator systems.

Contribution

It introduces a validated simulation model for discharge capillaries, enabling detailed analysis of plasma behavior and aiding future accelerator design.

Findings

Discharge deposits 178mJ of energy at 20 kV and 8.7mbar.

Simulation validated with experimental measurements.

Discusses challenges in Hα emission spectroscopy measurements.

Abstract

Plasma accelerators utilize strong electric fields in plasma waves to accelerate charged particles, making them a compact alternative to radiofrequency technologies. Discharge capillaries are plasma sources used in plasma accelerator research to provide acceleration targets, or as plasma lenses to capture or focus accelerated beams. They have applications for beam-driven and laser-driven plasma accelerators and can sustain high repetition rates for extended periods of time. Despite these advantages, high-fidelity simulations of discharge capillaries remain challenging due to the range of mechanisms involved and the difficulty to diagnose them in experiments. In this work, we utilize hydrodynamic plasma simulations to examine the discharge process of a plasma cell and discuss implications for future accelerator systems. The simulation model is validated with experimental measurements in a 50-mm-long, 1-mm-wide plasma capillary operating a 12-27 kV discharge at 2-12mbar hydrogen pressure. For 20 kV at 8.7mbar the discharge is shown to deposit 178mJ of energy in the plasma. Potential difficulties with the common density measurement method using H{\alpha} emission spectroscopy are discussed. This simulation model enables investigations of repeatability, heat flow management and fine tailoring of the plasma profile with discharges.