Comparative study of gas amplification and energy resolution in some argon-based mixtures

A mean gas amplification factor M in mixtures of argon with propane and DME at various pressures less than or equal to 50 kPa is studied. The deviatio ns from the linear dependence of gas gain on high voltage in a semi-log plo t are compared with those observed earlier in argon-isobutane mixtures. In all three kinds of mixtures, the magnitude M-0 of the gas gain where deviat ions start depends on the partial pressure of the admixture. Energy resolut ion at 5.9 keV has been measured in pure gases and in argon-based mixtures as a function of the gas gain. The best resolution has been obtained at low gas gains, similar to 100-200. At these gains better resolution is obtaine d for mixtures with lower partial pressure of the admixture. At high gas ga ins energy resolution depends strongly on the admixture partial pressure, a nd above M-0 it degrades much faster due to avalanche chain formation. (C) 2000 Elsevier Science B.V. All rights reserved.