[en] Differential cross sections for the /sup 2/H(γ,p)n reaction were measured at five laboratory angles, from 32⁰ to 130⁰, for photon energies between 100 and 250 MeV. The LEALE quasi-monochromatic photon beam, obtained at Frascati by positron annihilation on liquid hydrogen target, was used; the photon beam spectrum was measured on-line by a pair spectrometer. Preliminary values of angular distributions and total cross sections at three laboratory photon energies are presented

[en] A sensitive profile and position monitor for low intensity positron (approx.= 10^-₉ A) and photon (approx.= 10₈ ν/s) beams is described. It consists of a multiwire chamber with two sensitive planes and additional electronic circuits. The display of the beam profiles, which appears on a standard oscilloscope, is live and quantitative, the effect of adjustments of the beam transport is immediately and continuously visible. (orig.)

[en] The determination of photonuclear cross sections requires a knowledge of the primary photon spectrum. The intensity and the energy spectrum of the Frascati positron annihilation photon beam have been measured by a Komar et al. type quantameter and a pair spectrometer. The present paper concerns the study and the design of the pair spectrometer. In section 2 the general layout of the facility is reported. In section 3 the main characteristics of the magnet are given. Section 4 is concerned with the optical properties of the spectrometer. The detection system, with the associated electronics, is described in section 5. In section 6 the calculation of the spectrometer response function is reported. In section 7 the experimental photon energy spectrum, at positron energy Esub(+) = 200 MeV, compared with the calculated one, is given. (orig.)

[en] All the ²H(γ,p)n data in the energy range 20--440 MeV have been fitted to a simple phenomenological function. All differential cross-section data were used: The bremsstrahlung data were normalized to the total cross-section values obtained by fitting data provided by monochromatic photon beams. The results obtained give a good representation of the experimental points

[en] All existing data on the level densities, decay widths and lifetimes of excited nuclei have been analyzed in the framework of the statistical model in order to better determine the parameters of the phenomenological systematics of the nuclear level density. Data on level densities of several hundred nuclides obtained in the excitation energy range from 2 up to 20 MeV were used. The level densities of nuclei with large deformation (at the saddle point) have been studied by analyzing the data on the neutron emission and fission partial width ratio Γ_n/Γ_f, and the values of the fission barrier heights B_f, the level density parameters ratio a_f/a_n and the saddle point shell corrections δW_s.p. have been extracted. The influence of shell and collective effects on the level density and the decay widths of nuclei which have different excitation energies and deformations has been studied. (orig.)

[en] A Monte Carlo computing program has been used to calculate the photon spectrum and emittance from positron annihilation and bremsstrahlung. The positron energy spread, the energy loss and the multiple scattering in the annihilation target have been taken into account. Moreover, the positron emittance, the positron incidence angle and the finite angular acceptance of the photon collimation channel have been explicitly considered. Experimental results, obtained with a pair spectrometer and a beam profile monitor are in good agreement with calculations. In particular, it is shown that the positron emittance has a crucial influence on the shape of the photon spectrum and on the absolute value of the photon flux. (orig.)

[en] The best experimental conditions to perform photofission measurements in the energy range 100-300 MeV by using the Frascati annihilation photon beam are deduced. For nuclei with very low fission threshold energies it is shown to be advantageous to collect the photon beam at an angle deltasub(ν) > 1₀. For nuclei with high fission threshold energies, the annihilation photon contribution to the yield already pre-dominates for 0.5₀ <= deltasub(ν) <= 1₀. (orig.)

[en] The measurement of the response of the large-angle electromagnetic shower calorimeter (LAC) of the CLAS detector to minimum ionizing particles is reported. The experimental set-up and the adopted procedures are described. The results of the light attenuation length in the calorimeter, the light output and the resolution of the interaction point reconstruction are discussed. The performances of the LAC match well with those required

[en] We describe the performance of the readout of the Jet-Target internal tagging system. The apparatus and methods to test signal transmission and time dispersion of 3.5 m fiber optic light guides, and time drift, gain measurement and rate effect of the phototubes are presented. (orig.)

[en] Differential cross sections for the d(γ,p)n reaction were measured at five laboratory angles, from 32deg to 130deg, and for seven photon energies (100, 120, 140, 180, 200, 220 and 255 MeV). A quasi-monochromatic photon beam was used and the photon spectrum was measured on-line with a pair spectrometer. The absolute normalization uncertainty is within ±5%. Data agree, taking into account total errors, with results of recent experiments with monochromatic photons. (author)