Distortion of Thomson Parabolic-Like Proton Patterns Due to Electromagnetic Interference

Massimo De Marco,Jan Dostál,Filip Grepl,Josef Krása,Miroslav Pfeifer,Daniele Margarone,Andriy Velyhan

doi:10.3390/app11104484

Abstract

Intense electromagnetic pulses (EMPs) accompany the production of plasma when a high-intensity laser irradiates a solid target. The EMP occurs both during and long after the end of the laser pulse (up to hundreds of nanoseconds) within and outside the interaction chamber, and interferes with nearby electronics, which may lead to the disruption or malfunction of plasma diagnostic devices. This contribution reports a correlation between the frequency spectrum of the EMP and the distortion of Thomson parabola tracks of protons observed at the kJ-class PALS laser facility in Prague. EMP emission was recorded using a simple flat antenna. Ions accelerated from the front side of the target were simultaneously detected by a Thomson parabola ion spectrometer. The comparison of the two signals suggests that the EMP may be considered to be the source of parabolic track distortion.

Highlights

A traditional Thomson parabola ion spectrometer (TP) is a device that can distinguish ions propagating through it according to their charge-to-mass ratio and their kinetic energy [1]
This contribution reports a correlation between the frequency spectrum of the electromagnetic pulses (EMPs) and the distortion of Thomson parabola tracks of protons observed at the kJ-class PALS laser facility in Prague
Since the EMP affecting plasma diagnostics can be effectively detected by a simple antenna, and the recorded signal can be processed in the frequency domain [7,8], we compared the measured EMP signal with distorted parabolic tracks in order to investigate the effect of the EMP on the spectrometer, and to prove that the cause of track distortions at the PALS laser facility is the strong EMP generated in the target chamber

Summary

Introduction

A traditional Thomson parabola ion spectrometer (TP) is a device that can distinguish ions propagating through it according to their charge-to-mass ratio and their kinetic energy [1]. Ions with different energies experience varying electric-field strength, and their tracks on the detector plane are distorted. Faraday cage shielding around cables and the spectrometer can be used to mitigate this effect Another source of deviation from perfect tracks is attributed to the emission direction of the laser-accelerated proton beam itself at the the target surface (which is usually called “pointing”). Since the EMP affecting plasma diagnostics can be effectively detected by a simple antenna, and the recorded signal can be processed in the frequency domain [7,8], we compared the measured EMP signal with distorted parabolic tracks in order to investigate the effect of the EMP on the spectrometer, and to prove that the cause of track distortions at the PALS laser facility is the strong EMP generated in the target chamber

Experimental Arrangement and Measurement

Processing Antenna Signals and TP Snapshots

Correlation between Measured EMP and Captured Parabolic Track of Protons

Conclusions