Optimization of drift gases for accuracy in pressurized drift tubes

TL;DR

This paper investigates optimal gas mixtures for pressurized drift tubes in detectors, focusing on nitrogen and carbon dioxide to improve linearity and accuracy in particle tracking.

Contribution

It introduces new gas mixtures with minimal non-linearity and provides scaling laws for various pressures and magnetic fields, enhancing detector precision.

Findings

Identified nitrogen and carbon dioxide mixtures with near-linear space-time relationships

Provided scaling laws for different pressures and magnetic fields

Improved accuracy in drift tube measurements

Abstract

Modern detectors such as ATLAS use pressurized drift tubes to minimize diffusion and achieve high coordinate accuracy. However, the coordinate accuracy depends on the exact knowledge of converting measured times into coordinates. Linear space-time relationships are best for reconstruction, but difficult to achieve in the $E \propto \frac{1}{r}$ field. Previous mixtures, which contained methane or other organic quenchers, are disfavored because of ageing problems. From our studies of nitrogen and carbon dioxide, two mixtures with only small deviations from linearity were determined and measured. Scaling laws for different pressures and magnetic fields are also given.