Background model of Phoswich X-ray detector on board small balloon

TL;DR

This paper models the background noise in a Phoswich X-ray detector on a small balloon using Monte Carlo simulations, accounting for cosmic rays, atmospheric interactions, and detector materials, matching observed data.

Contribution

It introduces a detailed 3D Monte Carlo simulation approach to accurately estimate background counts in balloon-borne X-ray detectors, considering various environmental and material factors.

Findings

Simulation matches observed background at 30 km altitude.

Cosmic rays and detector radioactivity are major background sources.

Atmospheric and geomagnetic modeling improves background estimation.

Abstract

We performed a detailed modelling of the background counts observed in a phoswich scintillator X-ray detector at balloon altitude, used for astronomical observations, on board small scientific balloon. We used Monte Carlo simulation technique in Geant4 simulation environment, to estimate the detector background from various plausible sources. High energy particles and radiation generated from the interaction of Galactic Cosmic Rays with the atmospheric nuclei is a major source of background counts (under normal solar condition) for such detectors. However, cosmogenic or induced radioactivity in the detector materials due to the interaction of high energy particles and natural radioactive contamination present in the detector can also contribute substantially to the detector background. We considered detailed 3D modelling of the earth's atmosphere and magnetosphere to calculate the radiation environment at the balloon altitude and deployed a proper mass model of the detector to calculate the background counts in it. The calculation satisfactorily explains the observed background in the detector at 30 km altitude (atmospheric depth: 11.5 $g/cm^{2}$) during the balloon flight experiment from a location near 14.5$^{\circ}$N geomagnetic latitude.