A.A. Popov

A study of the detection accuracy of proportional chambers with cathode read-out

Abstract Results are presented of a study of the accuracy in detecting relativistic particle coordinates in proportional chambers using the cathode information read-out. The width of the cathode strips was 2 mm and the anode to cathode distance 4 mm. For the tracks perpendicular to the chamber plane the detection accuracy was 50 μm. Two methods of calculation of the centre of the induced charge distribution on the cathode strips are described: by the centre of gravity and by fitting this distribution by a special formula. It is shown that for single-particle events the change of the width of the induced charge distribution does not exceed 1.2%.

The DISTO data acquisition system at SATURNE

The DISTO collaboration has built a large-acceptance magnetic spectrometer designed to provide broad kinematic coverage of multiparticle final states produced in pp scattering. The spectrometer has been installed in the polarized proton beam of the Saturne accelerator in Saclay to study polarization observables in the p/spl I.oarr/p/spl rarr/pK/sup +/Y/spl I.oarr/ (Y=/spl Lambda/,/spl Sigma//sup 0/ or Y*) reaction and vector meson production (/spl phi/,/spl omega/ and /spl rho/) in pp collisions. The data acquisition system is based on a VME 68030 CPU running the OS/9 operating system, housed in a single VME crate together with the CAMAC interface, the triple port ECL memories, and four RISC R3000 CPU. The digitization of signals from the detectors is made by PCOS III and FERA front-end electronics. Data of several events belonging to a single Saturne extraction are stored in VME triple-port ECL memories using a hardwired fast sequencer. The buffer, optionally filtered by the RISC R3000 CPU, is recorded on a DLT cassette by DAQ CPU using the on-board SCSI interface during the acceleration cycle. Two UNIX workstations are connected to the VME CPUs through a fast parallel bus and the Local Area Network. They analyze a subset of events for on-line monitoring. The data acquisition system is able to read and record 3500 eV/burst in the present configuration with a dead time of 15%.

The DISTO first level trigger at SATURNE

The DISTO collaboration has built a large-acceptance magnetic spectrometer designed to provide broad kinematic coverage of multi-particle final states produced in pp scattering. The spectrometer has been installed in the polarized proton beam of the Saturne accelerator in Saclay to study polarization observables in the p/spl I.oarr/p/spl rarr/pK/sup +/Y/spl I.oarr/ (Y=/spl Lambda/, /spl Sigma//sup 0/ or Y*) reaction and vector meson production (/spl phi/, /spl omega/, and /spl rho/) in pp collisions. The common signature of such events is the multiplicity of four charged particles in the final state. A flexible 1st level trigger which uses topological information from fast detectors (scintillating fibers and hodoscope) has been built. It is completely software programmable through a menu-driven user interface and allows switching between production and monitor triggers on successive beam spills.