This paper describes the performances of a large volume drift chamber with
complete digitization of the output pulses. The electronics used in this te
st include wide-band (700 MHz) amplifiers and fast (1 Gsample/s) digitizers
. The gas mixture selected for drift chamber operation (80% He-20% CH4) and
the signal processing mentioned above allow the measurement of the primary
ionization clusters. The improvement in the (wire) impact parameter evalua
tion of the primary particle is sizeable. (C) 1999 Elsevier Science B.V. Al
l rights reserved.