Experimental study of a small-cell drift chamber operated with helium-based gases

The performance of a small-cell drift chamber operated with two helium-based gas mixtures, He/C3H8(60/40) and He/CH4(60/40), was studied using cosmic rays, respectively. The gas mixture Ar/CO2/CH4(89/10/1) was also tested for comparison. The spatial resolution and dE/dx resolution of the helium-based gases are better than those of Ar/CO2/CH4(89/10/1). A good spatial resolution of 110 mu m and a dE/dx resolution of 6%-7% with 30-40 samples were obtained with He/C3H8(60/40).