A FAST BIDIMENSIONAL DRIFT CHAMBER WITH 80-PERCENT CF4 PLUS 20-PERCENT ISOBUTANE MIXTURE OPERATING IN A MAGNETIC-FIELD OF 10 KG

This paper presents the characteristics of a bidimensional narrow-gap (2 min) drift chamber filled with CF4/isobutane (80/20) and operating in a magnetic field of 10 kG. The measurements were performed under a 50-MeV/c secondary pi(mu, e) beam at the TRIUMF accelerator (Canada). The drift of the ionization electrons in a magnetic field perpendicula r to the chamber plane was studied. The maximum drift time and was sim ilar or equal to 220 mu m, irrespective of the magnetic field. The cha mber's X-coordinate resolution was derived by analyzing the signals in duced on the cathode plane was similar or equal to 150 mu m at zero ma gnetic field. Taking into account the drift effect yields the same Y-c oordinate resolution (similar or equal to 150 mu m) as is obtainable a t zero magnetic field.