S. Serci

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.

On the detection of low energy γ-rays with plastic scintillators

Abstract An energy limit of 3–4 keV is achieved for the detection of γ-rays with plastic scintillators.

A Low Energy Antineutron Detector

A detector for antineutrons in the momentum range 0.1 - 1 Gev/c, to be used at LEAR faci= lity at CERN, is described. The antineutrons are detected by means of the charged pions produced in an annihilation event and their energy is determined by a time of flight mea= surement. The detector consist of 10 equal modules; each one contains: an iron slab (the converter) of 20×20×1 cm , a scintillation of the same dimensions for T.O.F. measurements, an iron sheet of 100×100×0.2 cm that stops the low energy high ionizing particles and finally a plane of limited streamer tubes with 1 cm pitch and read-out on both horizontal and vertical cohordinates. Principal features of the detector are: T.O.F. resolution of 0.5 ns, spatial resolution of 1 cm in both vertical and horizontal directions, estimated efficien= cy of 0.65.

A Time-of-Flight Hodoscope Saving the Number of Photomultipliers

Results of measurements of the performances of a time-of-flight hodoscope consisting of 16 slabs of plastic scintillator, 90×4×1 cm3 each, viewed by only 8 (instead of 32) photomultipliers are described. The slabs are coupled to the photomultipliers in such a way that they are considered as the elements of a square matrix of rank 4. Thus only 2×4 photomultipliers are needed to identify unambiguously each of the 16 slabs, if only a particle at a time has to be detected. By means of a very simple electronics we obtained a local time-of-flight resolution of 570 ps fwhm and a spatial resolution along each slab of 5 cm fwhm. The cross-talk due to unrecognized events was less than 5%.

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 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°.