Lj. Čonkić

Evaluation of bremsstrahlung spectra generated by a 4‐MeV linear accelerator

A modified method for the evaluation of bremsstrahlung spectra on the basis of transmission measurements is presented. The method is tested for two 4 MeV therapy accelerators. The calculated spectra are compared with other experimental results and Monte Carlo simulation.

De-excitation of 180mTa by 60Co Gamma Rays

The 180mTa (c, c@) 180Ta reaction was induced by gamma rays from a strong 60Co source. Population of the ground state was observed (eUective cross section 0.12 ^ 0.02 kbarns) with an integrated cross section of 0.13 ^ 0.04 kbarns MeV through mediating levels assumed near 1 MeV. Transition multi- polarities and astrophysical consequences are discussed. Subject headings: gamma rays: observationsnuclear reactions, nucleosynthesis, abundances

BREMSSTRAHLUNG ENDPOINT ENERGY MONITORING BY 115IN ACTIVATION DETECTOR

Abstract It is shown that ratio of 116m In and 115m In activities, simultaneously produced by neutron capture and photoexcitation of 115m In, could be very sensitive index for control of the end-point energy of therapy accelerator X-ray beams. The presented method can be used from 7 MeV where begins production of photoneutrons.

Study of Active Shielding for γ ‐ Spectrometers

The features of the ground located gamma ray spectrometer shielded passively with 12 cm of lead and actively by five 0.5m × 0.5m × 0.05m plastic veto shields are described. The detector mass related background was 0.345 C/kg s. The 511 keV annihilation line was reduced by the factor of 7 by the anticoincidence gate. It is shown that the plastic shields increase the neutron capture gamma line intensities due to neutron thermalization.