A. Del Guerra

A compilation of n-p and n-C cross sections and their use in a Monte Carlo program to calculate the neutron detection efficiency in plastic scintillator in the energy range 1–300 MeV

Abstract A compilation of n-p and n-C cross sections is presented, with the purpose of giving useful information to compute the efficiency of neutron counters used in high energy physics experiments. Particular consideration is given to the cross sections for neutrons of kinetic energy up to 300 MeV. The results of a Monte Carlo program, in which these cross sections were used, are presented and compared with the experimental data on neutron counter efficiencies available in the literature. A very good agreement between experimental results and Monte Carlo predictions, on average much better than 10%, has been obtained.

Threshold π+ electroproduction at high-momentum transfer: A determination of the nucleon axial vector form factor

Abstract Threshold π+ electroproduction has been measured at momentum transfers ‖k2‖ of 0.45, 0.58 and 0.88 (GeV/c)2, extending the range of earlier measurements. Using PCAC and current algebra-based models we have deduced the axial vector form factor of the nucleon GA(k2), and find that the dipole parametrisation is favoured over the monopole. The value of MA in the dipole parametrisation is, in a weak PCAC model, 0.96 ± 0.03 GeV, in excellent agreement with neutrino measurements. The threshold cross section is also in excellent agreement with the predictions of a fixed-t dispersion relation model.

Measurements of threshold π+ electroproduction at low momentum transfer

Abstract The reaction e− + p → e− + π+ + n has been studied near threshold at momentum transfer |k2| of 0.078, 0.155, 0.233 and 0.311 (GeV/c)2. The slope of the total cross section evaluated at threshold has been compared with models based on PCAC and current algebra to deduce the axial vector form factor of the nucleon, GA(k2). In the dipole parametrisation GA(k2)/GA(0) = (1 + |k2|/MA2)−2 we find that the models give values of MA ranging between 1.0 and 1.2 GeV. The π+n angular distributions are compared with fixed t dispersion relations and with a pseudovector Born approximation and are found to be in good agreement.

Comparison of two dedicated 'in beam' PET systems via simultaneous imaging of (12)C-induced beta(+)-activity.

The selective energy deposition of hadrontherapy has led to a growing interest in quality assurance techniques such as in-beam PET. Due to the current lack of commercial solutions, dedicated detectors need to be developed. In this paper, we compare the performances of two different in-beam PET systems which were simultaneously operated during and after low energy carbon ion irradiation of PMMA phantoms at GSI Darmstadt. The results highlight advantages and drawbacks of a novel in-beam PET prototype against a long-term clinically operated tomograph for ion therapy monitoring.

Efficiency and spatial resolution measurements of a modular neutron detector in the kinetic energy range 15–120 MeV

Abstract The detection efficiency of a 3 × 3 matrix of NE 110 scintillator blocks, 153 × 153 × 270 mm long, has been measured in the neutron kinetic energy range 15–120 MeV for several thresholds, ranging from 2.80 to 15.75 MeV equivalent electron energy, and for various thicknesses of lead shielding in front of the counter. The probabilities of detecting a neutron in a block different from the one struck by the beam (‘mixing’) and in more than one block (‘multifiring’) have also been measured as a function of threshold and shielding. Comparisons have been made with a Monte Carlo program which accounts for the modular structure of the counter. The efficiency and the spatial resolution of a very large matrix have been obtained, using both experimental and Monte Carlo results.

Measurements of shadowing in low |Q2| electroproduction on nuclei

Measurements of inelastic electron scattering have been made in the range 2.2 < ν < 3.8 GeV and 0.1 < |Q2| < 0.3 (GeV/c)2, on a selection of nuclei ranging from hydrogen and deuterium to uranium, by measuring the scattered electron only. Detailed calculations have been made of the contribution of radiative tails to the measured yield. The results show a small ‘shadowing’ consistent with other electroproduction experiments, and also with photoproduction experiments in this ν range, but the shadowing decreases rapidly as |Q2| increases.

Some Aspects of the Construction of HISPET: A High Spatial Resolution Positron Emission Tomograp

We describe the improvements achieved toward the construction of a large solid angle Positron Camera, made of six dense drift space MWPC modules, arranged to form the lateral surface of a hexagonal prism. The tomograph will have an intrinsic spatial resolution of ¿4.5 mm (FWHM) and a volume sensitivity of ~100000 c/s per 0.1 ¿Ci/ml, for a signal to noise of 3:1.

Calibration of a modular plastic scintillator neutron detector in the kinetic energy range 100–500 MeV

Abstract We describe the calibration of a modular neutron counter for neutrons and protons of between 100 and 500 MeV kinetic energy. We present results for the detection efficiency, time and spatial resolution, and multifiring. We emphasise the necessity of calibrating the crosstalk between neutron and photon identification.

A MWPC with a cathode coupled delay line read-out as radioactivity detector for DNA repair studies

A non selective method for the isolation of DNA repair-deficient mutants in mammalian cells is discussed. The method requires radioactive labelling of the short DNA sequences synthesized during repair of damaged regions. Mutants should be recognized by the absence of radioactive incorporation into thier DNA. A multiwire proportional chamber (MWPC) is proposed as a suitable radioactivity detector. The performance of a MWPC prototype with a cathode coupled delay line read-out is described and is shown to be adequate for this application. The main avaantages of a MWPC are reviewed with respect to other methods used for β− radioactivity counting of biological samples, such as liquid scintillators or autoradiography: the proposed detection method is non destructive for the cells, which are being kept alive for further biological studies; furthermore many cell clones can be screened within a reasonable time.

A Large Aperture Neutron Time-Of-Flight Spectrometer

Abstract We describe a large aperture 2 m × 2 m neutron time-of-flight spectrometer, consisting of 145 plastic scintillator blocks, each 270 mm deep and 153 × 153 mm 2 in area. We present details of the design, the construction and the on-line data acquisition and monitoring system. We briefly summarise its performance: detection efficiency ≳20%, time-of-flight and spatial resolution (standard deviation) ∼1.1 ns and ∼ 0.9 blocks respectively. The counter operated successfully for four years in conjuction with a high resolution electron spectrometer to measure electroproduction processes with a nucleon in the final state. Although it was designed for the detection of neutrons of kinetic energy between 30 and 500 MeV, it was well suited also for the detection of high energy protons.