Propagation of gamma rays and production of free electrons in air

TL;DR

This paper analyzes how gamma rays from radioactive materials produce free electrons in air, potentially enabling remote detection of concealed radioactive sources through air breakdown induced by high-power electromagnetic beams.

Contribution

It introduces a detailed analysis of free electron production by gamma rays, supporting a new remote detection method for concealed radioactive materials using air breakdown.

Findings

Free electrons from gamma rays can exceed natural background ionization within 100 meters.

Electrons produced during a 10 microsecond gyrotron pulse can seed air breakdown.

This process enables detection of concealed radioactive sources via plasma formation.

Abstract

A new concept of remote detection of concealed radioactive materials has been recently proposed \cite{Gr.Nusin.2010}-\cite{NusinSprangle}. It is based on the breakdown in air at the focal point of a high-power beam of electromagnetic waves produced by a THz gyrotron. To initiate the avalanche breakdown, seed free electrons should be present in this focal region during the electromagnetic pulse. This paper is devoted to the analysis of production of free electrons by gamma rays leaking from radioactive materials. Within a hundred meters from the radiation source, the fluctuating free electrons appear with the rate that may exceed significantly the natural background ionization rate. During the gyrotron pulse of about 10 microsecond length, such electrons may seed the electric breakdown and create sufficiently dense plasma at the focal region to be detected as an unambiguous effect of the concealed radioactive material.