Experimental determination of the induced activity in activation detectors of a complex geometric shape

The paper presents the results of experimental determination of the induced activity in copper-/aluminum-based activation detectors when irradiated with neutrons with energies of about 14 MeV. The activation detectors were square-shaped metal plates with a thickness from 1.0 to 1.5 mm and a side size about 5.0 cm. These dimensions significantly exceed those of the detectors that are used in the research of high-intensity neutron fluxes. The detectors described in this work can be used for studying low-intensity neutron fluxes (with a flux density of up to 106 n/cm2∙s). It is shown that, when working with such detectors, it is possible to apply the usual methods for calculating the induced activity in thin activation detectors, with corrections that take into account the emerging features of the ‘neutron source - activation detector’ and ‘activation detector - secondary radiation detector’ geometries. The effects of absorption of primary and secondary radiation by the detector substance are also revealed. The Geant4 tools were used for calculating the geometric factors and theoretical induced activity. The study confirms the applicability of such activation detectors for solving the problem of determining the yield of neutrons with energies of about 14 MeV from a neutron generator target. The results of the experiments coincide, within the margin of error, with the results of simulations performed using the Geant4 tools.

Application of fluorine-based threshold activation detector for neutron flux calculation from D-T neutron generator

In this paper we propose a method of fast neutron flux estimation from a pulsed D-T neutron generator with application of single CaF2 scintillation crystal. The analysis method relies on 19F(n, α)16N threshold activation reaction having neutron energy threshold at 1.6 MeV. As a result, the 16N undergo β− decay with half-life of 7.1 s, emitting β particles with endpoint up to 10.4 MeV in the scintillator medium. Integration of the β distribution curve, preceded by calculation of (n, α) rate on F with Monte Carlo N-Particle Transport Code v6 (MCNP6) for fixed geometry, allows to estimate the neutron flux in 4π per second within few minutes.

Electron fluence determination per Monitor Unit of a linear accelerator used for radiation therapy

About 20% of patients in Greece undergoing radiotherapy were irradiated by electron beams with energies ranged between 4 to 20 MeV. The correct determination of electron beam, leads to the proper treatment planning. In this study electron fluence at the isocenter was determined for a linear accelerator ELECTA SL 20 for nominal electron energy of 20 MeV. Two methods have been applied using (a) an ionization chamber in the frame of monthly quality assurance and activation detector (238U). The experimental estimated electron flux, which was in good agreement with the applied calculations using the data of irradiation procedure, ranged between 3.5 up to 4.3 x 108 electrons per cm 2 per sec or 6.1 ±0.7 x 10^7 e.cm-2 per MU.

New experimental research stand SVICKA neutron field analysis using neutron activation detector technique

Knowledge of neutron energy spectra is very important because neutrons with various energies have a different material impact or a biological tissue impact. This paper presents basic results of the neutron flux distribution inside the new experimental research stand SVICKA which is located at Brno University of Technology in Brno, Czech Republic. The experiment also focused on the investigation of the sandwich biological shielding quality that protects staff against radiation effects. The set of indium activation detectors was used to the investigation of neutron flux distribution. The results of the measurement provide basic information about the neutron flux distribution inside all irradiation channels and no damage or cracks are present in the experimental research stand biological shielding.