Absolute keV X-ray yield and conversion efficiency in over dense Si petawatt laser plasma

TL;DR

This study measures the absolute X-ray yield and conversion efficiency from a silicon plasma created by a petawatt laser, providing detailed spectral data and comparing results with simulations to understand emission mechanisms.

Contribution

It presents the first broad spectral range absolute measurements of X-ray emission from laser-produced silicon plasma and compares these with particle-in-cell simulations for detailed analysis.

Findings

Good agreement between experimental and simulated bremsstrahlung conversion efficiencies.

Spectral data includes line transitions and broadband emission from recombination and free-free processes.

Simulations help distinguish bremsstrahlung and synchrotron contributions.

Abstract

Laser-produced plasmas are bright, short sources of X-rays often used for time-resolved imaging and spectroscopy. Absolute measurement requires accurate knowledge of laser-to-x-ray conversion efficiencies, spectrum, photon yield and angular distribution. Here we report on soft X-ray emission from a thin Si foil irradiated by a sub-PW picosecond laser pulse. These absolute measurements cover a continuous and broad spectral range that extends from 4.75 to 7.5 Angstroms (1.7-2.6 keV). The X-ray spectrum consists of spectral line transitions from highly charged ions and broadband emission with contributions from recombination, and free-free processes that occur as electrons decelerate in plasma electromagnetic fields. These quantitative measurements are compared to particle-in-cell simulations allowing us to distinguish bremsstrahlung and synchrotron contributions to the free-free emission. We found that experiment and simulation estimations of laser-to-bremsstrahlung conversion efficiency are in a good agreement. This agreement illustrates the accuracy of experiment and physical interpretation of the measurements.