G. Puddu

Performances of the OBELIX time of flight system

Abstract The characteristics and performances of a large time of flight detector which is composed by two scintillator barrels, installed between the poles of an axial field magnet as part of the OBELIX spectrometer, are described. The associated electronics, data acquisition system and analysis technique used in the system are discussed in details. The importance of the detector for trigger purposes and for the comprehension of the full event is shown.

Measurement of the Annihilation Cross-Section for Antineutrons on Fe from 100 to 531 MeV/c

The cross-section for annihilation on Fe from 100 to 531 MeV/c was measured by means of a layered absorption detector. The cross-sections are related to the free N annihilation cross-sections by a simple A2/3 scaling law, indicating a surface process.

A low momentum tagged antineutron beam

The operating performances of a low-momentum (< 270 MeV/c) tagged n beam are reported. The n beam is obtained by means of the charge exchange reaction pp → nn on a liquid hydrogen target. The neutron associated to the n in the two-body reaction is used for the determination of the n energy and direction. The measured total rate of tagged n is 8.02 ± 0.03 × 10−5 per incident p at 300 MeV/c.

A Study of the bar n Production on Nuclei by bar p of 550 MeV/c

Inclusive spectra produced at 0° by the interaction of 550 MeV/c s on C, Al, Cu and Pb targets were measured. The results are discussed in the framework of simple models on incoherent particle production by complex nuclei.

On the Limits of the Performances of Time-of-Flight Scintillator Hodoscopes Saving the Number of Photomultipliers

Results of measurements of the performances of a prototype of a time-of-flight scintillator hodoscope suited for neutron detection are described. The hodoscope will have a configuration that allows the use of a reduced number of photomultipliers. The scheme was already used for the detection of charged particles and the measurements show that the good performances are maintained even with the continuous pulse height spectra produced by neutrons.

A Large Area, Fine Grained Neutron Hodoscope

Results of measurements of the performances of a time-of-flight neutron hodoscope consisting of 50 slabs of plastic scintillator, 100 × 2 × 5 cm3 each, are described. The efficiency and the spatial localization properties along a slab were studied with a variable energy (2.4 to 16.4 MeV) neutron beam. The hodoscope was finally used in the experiment PS 178 at the LEAR facility at CERN.

A high energy physics run control system based on an object oriented approach

The run control system developed for the Obelix experiment at the Low-Energy Antiproton Ring of CERN is described. The approach adopted is based on a state manager developed as a part of the MODEL project. The state manager incorporates a model for the different activities and for the way they must be organized. An object-oriented decomposition of the online system is performed. A clean separation of control, logic, and operating tasks is achieved. Remote procedure call techniques are employed to cope with the problems of a distributed system architecture. >

A Systematic Study of A Large Aperture Gas Cherenkov Counter

Abstract The performance of a simple low-pressure, large aperture gas Cherenkov counter of reduced length is described. It gives a uniform efficiency larger than 99% over an entrance area of ≈ 700 cm 2 and for angles of divergence of the particles up to 12°.

The Zero Degree Calorimeter Readout Card for ALICE

ALICE at the CERN LHC will investigate the physics of strongly interacting matter at extreme energy densities where the formation of the Quark Gluon Plasma is expected. Its properties can be studied from observations like the production of mesons with charm and beauty quarks. These observations have to be studied as a function of energy density which is determined by the centrality of collisions. The energy carried by the spectator nucleons, related to the centrality, is measured by the Zero Degree Calorimeters (ZDC). The ZDC readout consists of a VME system with a ZDC Readout Card, a VME Processor, Discriminators, a ZDC Trigger Card, scalers, QDCs and TDCs. The system was successfully tested during the 2009 ALICE data taking and is currently operational at the LHC. This paper describes the ZDC Readout Card which forms an important part of the ZDC readout system.

A Method for Calculating the Efficiency of Large Aperture Gas Cherenkov Counters

A method for calculating the efficiency of large aperture gas Cherenkov counters is presented. It is based on a careful Monte Carlo simulation of the geometrical response of the apparatus and on the measurement of the number of photoelectrons detected by the photomultipliers for some selected directions of the particles traversing the radiating volume. An application to a counter whose efficiency was systematically measured with great care is presented. The results are very satisfactory.