Nuclear Instruments and Methods 204 (1982) 65-72 65 North-Holland Publishing Company EXPERIENCES WITH A PROPORTIONAL INCLINED CHAMBER AT THE EUROPEAN HYBRID SPECTROMETER Alessandro BETTINI, Donatella PASCOLI and Pierluigi ZO'ITO lstituto di Fisica dell'UniversitgJ and Istituto Nazionale di Fisica Nucleare, Sezione di Padova, Via Marzolo 8, 35100 Padova, Italy Manfred PERNICKA Institut fiir Hoehenergiephysik, Osterreichisehe Akademie der Wissenschaften, Nikolsdorfergasse 18, 1050 Vienna, Austria Received 8 April 1982 A new detector of ionizing particles, the Proportional Inclined Chamber, is described. The detector provides a resolution better than 100 p,m in the measured coordinate, independent in first approximation of drift velocity variations. It has good, about 300 btm two-track resolution and gives a rough measurement of the angle of the track with a resolution of about 1°. Results obtained with PIC in physics experiments at the European Hybrid Spectrometer are reported. 1. Introduction PIC is a multiwire proportional chamber inclined with respect to the average direction of the tracks. When the angle a between the normal to the chamber and the line of flight of a particle increases, its track in the chamber is projected on an increasing number of sense wires [1]. Fig. 1 shows a sketch of the lines of field in a section of the chamber perpendicular to the wires; the electrons produced by ionization drift in a first approximation along the field lines with saturated veloc- ity and we detect the first electron reaching each wire. To help the reader to understand the situation we display in fig. 1 the shortest path for each cell (i.e. for each sense wire). The number N of wires affected by the passage of the particle is an increasing function of the inclination angle a and of the gap width G, and a decreasing function of the pitch d of the sense wires. By measuring the drift times of the first electron reaching each wire, we obtain N measurements of the sense wire signals times in respect to the track time. Due to the redundancy of information obtained, that allows one to calibrate the chamber with only internal information, the main advantages of PIC are the follow- ing: a) It provides good resolution, better than 100 /zm in one coordinate plane, improving when the angle of the track with the normal increases. This is not only due to the increase in the number of hit wires, but also to the decrease of the fluctuations of the drift times due to the statistics of the primary ionization acts. b) The impact point measurement is at first order inde- Fig. 1. Drift paths of the first electrons. 0167-5087/82/0000-0000/$02.75 © 1982 North-Holland