arXiv subjects

Michael Ehret

Publications and source records attributed to Michael Ehret.

5 recordsLinked to original sources

arXiv2024

Laser Interactions with Gas Jets: EMP Emission and Nozzle Damage

Understanding the physics of electromagnetic pulse emission and nozzle damage is critical for the long-term operation of laser experiments with gas targets, particularly at facilities looking to produce stable sources of radiation at high repetition rate. We present a theoretical model of plasma formation and electrostatic charging when high-power lasers are focused inside gases. The model can be used to estimate the amplitude of gigahertz electromagnetic pulses (EMPs) produced by the laser and the extent of damage to the gas jet nozzle. Looking at a range of laser and target properties relevant to existing high-power laser systems, we find that EMP fields of tens to hundreds of kV/m can be generated several metres from the gas jet. Model predictions are compared with measurements of EMP, plasma formation and nozzle damage from two experiments on the VEGA-3 laser and one experiment on the Vulcan Petawatt laser.

physics.plasm-ph↗

arXiv2024

Currents from relativistic laser-plasma interaction as novel metrology for system stability of high-repetition-rate laser secondary sources

This work shows for the first time experimentally the close relation between return currents from relativistic laser-driven target polarization and the quality of the relativistic laser plasma interaction for laser driven secondary sources. Such currents rise in all interaction schemes where targets of any kind are charged by escaping laser-accelerated relativistic electrons. Therefore, return currents can be used as a metrological online tool in the optimization of many laser-driven secondary sources and for diagnosing their stability. We demonstrate the destruction free measurement of return currents at the example of a tape target system irradiated by the 1 PW VEGA3 laser at CLPU at its maximum capabilities for laser-driven ion acceleration. Such endeavour paves the ground for feedback systems that operate at the high-repetition-rate of PW-class laser systems.

physics.plasm-ph↗

arXiv2023

High-repetition-rate source of nanosecond duration kA-current pulses driven by relativistic laser pulses

We report the first high-repetition rate generation and simultaneous characterization of nanosecond-scale return currents of kA-magnitude issued by the polarization of a target irradiated with a PW-class high-repetition-rate Ti:Sa laser system at relativistic intensities. We present experimental results obtained with the VEGA-3 laser at intensities from 5e18 - 1.3e20 W/cm2. A non-invasive inductive return-current monitor is adopted to measure the derivative of return-currents on the order of kA/ns and analysis methodology is developed to derive return-currents. We compare the current for copper, aluminium and Kapton targets at different laser energies. The data shows the stable production of current peaks and clear prospects for the tailoring of the pulse shape, promising for future applications in high energy density science, e.g. electromagnetic interference stress tests, high-voltage pulse response measurements, and charged particle beam lensing. We compare the target discharge of the order of hundreds of nC with theoretical predictions and a good agreement is found.

physics.plasm-ph↗

arXiv2023

High-repetition-rate solid tape target delivery system for ultra-intense laser-matter interaction at CLPU

The VEGA-3 laser system at the Centro de L\'{a}seres Pulsados (CLPU) delivers laser pulses up to 1PW at 1Hz repetition rate, focused to intensities up to 2.5e20W/cm2. A versatile and compact targetry solution suitable for this repetition rate is presented. The system can operate in the challenging petawatt laser environment close to the laser-plasma interaction. Strips are spooled in a tape target system to deliver a solid density target to the laser focus for every shot. Results are presented for different tape materials and thicknesses. Experimental ion spectra are recorded by a Thomson Parabola Ion Spectrometer coupled with a scintillator screen; and an antenna array is used for the characterization of electromagnetic pulses. The results of both diagnostics show a good shot-to-shot stability of the system.

physics.plasm-ph↗

arXiv2022

Ablation Holes in Tape Targets Induced by Ultra-Intense Laser Pulses

We present a theoretical modelling able to predict the dimensions of mm-sized through-holes produced in interactions of the 1 PW high-power 30fs Ti:Sa laser VEGA-3 with tape targets. We find that sizes of through-holes can be calculated by assuming that the full heat transferred from the laser-heated electron population to the target by electron-electron collisions drives the evaporation of target material. We demonstrate the good reproduction of experimental results.

physics.plasm-ph↗