| Abstrakt: |
Gaseous detectors are widely used in high energy physics and are an attractive choice in tracking systems for cosmic muon imaging, also called muography. Such detectors offer high resolution and high efficiency at a 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 the gas consumption of an outdoor gaseous tracker, where particularly the gas density change from daily temperature cycling limits the input flow. Such a "breathing" effect can be circumvented by a well designed buffer volume, which must prevent external air contamination. A realistic multi-wire proportional chamber tracking test system with 0.9 m 2 area and a total volume of 160 l has been operated for 36 days with a flow of 3 l/day, confirming the buffer volume; in this case, a 50 m long and 10 l volume low diffusion tube ensures the sufficient gas quality. The key effects governing the gas flow dynamics, including diffusion and gas volume change, have been studied quantitatively, leading to practical design prescriptions. [ABSTRACT FROM AUTHOR] |
