Towards low gas consumption of muographic tracking detectors in field applications

TL;DR

This paper explores methods to significantly reduce gas consumption in outdoor muographic gaseous detectors by designing buffer volumes that mitigate temperature-induced density changes, enhancing field deployment practicality.

Contribution

It introduces a practical buffer volume design to minimize gas flow needs in outdoor gaseous detectors, addressing maintenance challenges in remote muography applications.

Findings

A 50 m long, 10 l buffer volume maintains gas quality over 36 days.

Flow rate of 3 l/day is sufficient with the buffer design.

Quantitative analysis of gas flow dynamics informs practical design guidelines.

Abstract

Gaseous detectors are widely used in high energy physics, and are attractive choices in tracking systems for cosmic muon imaging, also called muography. Such detectors offer high resolution and high efficiency at reasonable cost for large sizes, however, one of the drawbacks is that the gaseous detection medium must be prevented from contamination by outside air or internal outgassing. Standard systems work with a constant gas flow, leading to regular maintenance in the form of gas cylinder changes, which can be an issue for remote field applications. In this paper we discuss the practical possibilities to reduce gas consumption of an outdoor gaseous tracker, where particularly the gas density change from daily temperature cycling limits the input flow. Such "breathing" effect can be circumvented by well designed buffer volume, which must prevent external air contamination. A realistic MWPC tracking test system with 0.9 square meter area, total volume of 160 l, has been operated for 36 days with a flow of 3 l/day, confirming that the buffer volume, in this case a 50 m long and 10 l volume low diffusion tube, ensures sufficient gas quality. The key effects governing the gas flow dynamics, including diffusion and gas volume change, has been studied quantitatively, leading to practical design prescriptions.