Nuclear Instruments and Methods in Physics Research最新文献

The error resulting from a commonly used formula in nuclear reaction kinematics is pointed out in this paper.

The energy resolution and the throughput rate of a quasi-trapezoidal filter, based on a modified version of the DL-RC circuit, have been studied as a function of the counting rate up to ∼10⁵ counts per second.

The performance of the modified DL-RC circuit is compared with that of a semi-Gaussian active filter and that of a quasi-trapezoidal gated integrator.

The design, development, and balloon-flight verification of a payload for observations of gamma-ray emission from solar flares are reported here. The payload incorporates a high-purity germanium semiconductor detector, standard NIM and CAMAC electronics modules, a thermally stabilized pressure housing, and regulated battery power supplies. The flight system is supported on the ground with interactive data-handling equipment comprised of similar electronics hardware. The modularity and flexibility of the payload, together with the resolution and stability obtained throughout a 30 h flight, make it readily adaptable for high-sensitivity, long-duration balloon flight applications.

The evaluation of 42 MeV bremsstrahlung spectra from a clinical betatron by using the photoactivation method is described. Photonuclear reactions, mainly of the (γ, n) type, are used as activation detectors. After measurements of photon-induced activities from residual nuclei are performed, the spectral distribution of photons is evaluated by solving the unfolding problem. The latter is carried out through the use of two independent methods, orthonormal expansion and Monte Carlo. In both cases prior conditions to the solution are imposed. Spectra evaluated by both methods and making use of two different size flattening filters are presented. An empirical method to estimate the “effective” thickness of the Pt target is described.

Corrections to the Z² dependence of ion chamber and Cherenkov response due to the Mott cross section are calculated for the HEAO-3 Heavy Cosmic Ray Experiment. The effect of the production and escape of high energy secondary electrons on detector response is accounted for by numerical calculations. These secondary electron effects are shown to influence the size of the non-Z² effects and thus affect the charge-assignments and detector resolution. The Bloch and relativistic Bloch corrections are not included in the results presented here but may be combined with the Mott corrections when the Bloch corrections are properly evaluated.

A vertex detector is proposed for charm and beauty experiments using a simple arrangement of scintillating optical fibres to provide high resolution (∼10 μm) in a plane transverse to the event axis. Experience with the high resolution bubble chambers shows that this is optimal for the detection of heavy flavour decays in complex events. The aim is to provide a high rate triggerable charm/beauty track and vertex detector for fixed target or collider experiments.

A Monte Carlo program has been developed to simulate the γ-ray spectral response of semiconductor detectors. Calculations have been carried out for HgI₂. Photons in the range from 5 keV to 1 MeV are considered as emitted from a source of zero thickness aligned to the crystal axis and followed until their complete energy loss of their escape from the crystal. The program allows the optimization of important parameters in a semiconductor detector, the study of their influence on the spectra obtained and the determination of performance parameters, such as energy resolution and efficiency. Some results have been compared with experimental data.

A heavy ion gas detector system consisting of a Bragg-curve spectroscopy ionization chamber for particle identification and a multiwire proportional chamber as position sensitive fast trigger device is described. The Bragg IC has been tested with several beams up to Z = 36 to investigate some aspects of the BCS method. Results are reported on energy resolution and linearity, Z resolving power and mass sensitivity. The energy resolution is well below 1%. The Bragg-peak amplitude is fairly independent of the energy in a wide energy range and single elements are identified up to Z = 38 with a resolving power Z/ΔZ − 50-80. Isotope identification by range measurement is limited by the straggling in the ionization process and the mass resolving power is M/ΔM ∼ 20–26 for S and Si isotopes. The MWPC allows subnanosecond time resolution and position identification along the in-plane coordinate within ±0.5 mm.

Partial summation is a very efficient method in curve fitting.