Argon-based Gas Research Articles

Studies of helium gas mixtures in drift chambers

Some properties of gas mixtures composed predominately of helium and lesser amounts of CO 2 and isobutane were measured in a prototype drift chamber. The studies are motivated by the desire to reduce the multiple scattering inside the drift chamber at future high-luminosity, low-energy facilities such as φ factories, τ/charm factories, and B factories. The low atomic number of helium greatly reduces the multiple scattering contribution to the momentum resolution compared to an argon-based gas mixture. The position resolution, pulse height, efficiency, and breakdown characteristics were measured for various gas mixtures. A mixture of 83% He, 10% CO 2, and 7% isobutane gives comparable results to that of an argon-based gas commonly used in drift chambers.

Study of argon-based penning gas mixtures for use in proportional counters

Results from an experimental investigation of three Penning gas mixtures, namely argon-acetylene (Ar-C 2H 2), argon-xenon (Ar-Xe) and argon-xenon-trimethylamine (Ar-Xe-TMA), are reported. The measurements, carried out in cylindrical geometry as well as parallel plate geometry detectors, demonstrate that the Ar-C 2H 2 mixtures show a significant Penning effect even at an acetylene concentration of 10% and provide the best energy resolution among all the argon-based gas mixtures (≤13% FWHM at 5.9 keV and 6.7% at 22.2 keV). In the parallel plate detector the Ar-C 2H 2 fillings provide a resolution of ≈ 7% FWHM at 22.2 keV up to a gas gain of at least ⋍10 4 . The nonmetastable Penning mixture Ar-Xe provides the highest gas gain among all the argon-based gas mixtures and is well suited for use in long-duration space-based experiments. Best results are obtained with 5% and 20% Xe in Ar, the energy resolution being ⋍ 7% FWHM at 22.2 keV and ⋍ 4.5% at 59.6 keV for gas gain ⪅10 3. Addition of ≥1% TMA to an 80% Ar-20% Xe mixture produces a dramatic increase in gas gain but the energy resolution remains unaffected (≈ 7% FWHM at 22.2 keV). This increase in gas gain is attributed to the occurrence of a Penning effect between Xe and TMA, the ionization potential of TMA being 8.3 eV, just below the xenon metastable potential of 8.39 eV.