FANO FACTOR AND THE MEAN ENERGY PER ION PAIR IN COUNTING GASES, AT LOW X-RAY ENERGIES

摘要

The mean energy per ion-pair (Wi) and the Fano factor (F) are provided with high accuracy (2 and 3-4, respectively), in C2H6, C3H8, i-C4H10, CH4, DME, Ar/C2H6(20:80), Ar/i-C4H10(20: 80) Ar/DME (20:80) and Ar/Xe/i-C4H10(66.6/16.7/16.7), in the x-ray energy range of 0.11-1.5 keV. These parameters were extracted from precise measurements of the number and temporal distribution of x-ray induced electrons, accompanied by extended simulations of the detection process. A decrease in these parameters with increasing x-ray energy was observed, accompanied by sharp increases at x-ray energies just above some atomic shells. The effect is discussed in relation to Auger electron emission. A Penning process in Ar/C2H6(20:80) and Ar/i-C4H10 (20:80) is observed on the basis of comparative measurements of Wi and F in these mixtures and in the pure hydrocarbons. Ways are proposed for further improving the accuracy provided by the electron counting technique to better than 1. (C) 1997 American Institute of Physics. References: 45