Hard bremsstrahlung from a high-voltage atmospheric discharge and its anisotropy

TL;DR

This study investigates hard gamma radiation emitted during high-voltage atmospheric discharges, revealing multi-beam patterns, bursts, and needle-like radiation indicating electron acceleration in plasma channels.

Contribution

It provides experimental data on the angular distribution and energy of gamma radiation during high-voltage discharges, highlighting anisotropic emission patterns and electron acceleration mechanisms.

Findings

Multi-beam radiation patterns observed in each shot

Hard radiation with energies up to or exceeding maximum electron energy

Needle-like radiation patterns indicating electron acceleration in plasma channels

Abstract

The results of the experiments on recording hard gamma radiation and measurements of its angular distribution at the initial stage of a laboratory high-voltage atmospheric discharge are presented. The experiments were performed on an ERG installation at a voltage of $\sim 1$ MV, an atmospheric discharge current of up to 12 kA, and a gap of 0.55 m. The duration of the voltage pulse was about 1~$\mu$s with a pulse rise time of 150-200 ns. The radiation was recorded by an assembly of 10 identical scintillation detectors installed each 10$^\circ$ around the circumference of a quarter of a circle with a curvature of 1 m. In order to separate the radiation with energies from 20 keV to 1.5 MeV, Al and Pb filters of different thicknesses were used. The obtained results show that, as a rule, a multi-beam radiation pattern and several bursts of radiation (each with a directional pattern) are recorded in each shot. In a considerable number of "shots", hard radiation with photon energies comparable to or exceeding the maximum electron energy corresponding to the applied voltage is recorded. In these cases, a needle-like radiation pattern is observed, including at large angles to the axis of the discharge. This may indicate the acceleration of electrons in different plasma channels.