Gamma-calibration of NE 213 scintillation counters

A cubic EJ-309 liquid scintillator of 10 cm width has been characterized for its response to γ -rays and neutrons. Response functions to γ -rays were measured with calibrated radionuclide γ -ray sources in the energy range from 400 keV to 6 MeV. Response functions for neutrons were obtained from measurements at the PTB Van de Graaff accelerator with quasi-monoenergetic neutron beams in the energy range from 500 keV to 2.7 MeV, and at the PTB cyclotron with time-of-flight (TOF) measurements in the energy range from 2.5 to 14 MeV. The light output and resolution functions for electrons and protons were derived by a least squares adjustment to experimental data using theoretical response functions determined with Monte Carlo simulations. The simulated response function for neutron was validated by results of measurements with an AmBe neutron source which was characterized for its total neutron intensity. The results indicate that the cubic EJ-309 detector is suitable for use in mixed γ -ray and neutron fields.

Characterization of a cubic EJ-309 liquid scintillator detector

/pdf/scintillation-detectors-for-fast-neutrons-2zd1z7uff0.pdf

Scintillation detectors for fast neutrons

The recoil proton energy response has been measured by exposing cylindrical cells, filled with BC501A BICRON liquid scintillator, to mono-energetic neutron reference fields. We determine the required calibration parameters and report the detailed procedures for the experimental data handling. A dedicated Monte Carlo simulation of the detector response and efficiency has been performed. It showed good agreement with the measured quantities. The results from this calibration are necessary for a detailed study of the neutron spectrum at the underground Gran Sasso Laboratory, with a neutron detector made of 32 liquid scintillator cells, like those used during the calibration.

Calibration of BC501A liquid scintillator cells with monochromatic neutron beams

When using an organic liquid scintillator such as NE213 for neutron spectrometry, the light output as a function of proton energy is needed in order to unfold the neutron spectrum from the scintillator's pulse height distribution. We have measured this function for several detectors over the range 1.5–16 MeV approximately, using monoenergetic neutrons from the Harwell 5 MV Van de Graaff accelerator. Results were obtained for a wide variety of sizes and shapes of the scintillator cell, and were found to be essentially in agreement within errors. The results were also compared with those of several other workers (amongst whom there is considerable disagreement). Below 10 MeV, there is excellent agreement with one worker and moderate or poor agreement with others; above 10 MeV, agreement is moderate in all cases. We conclude that workers wishing to unfold neutron spectra from NE213 pulse height distributions would be advised to make measurements with their own particular detector configuration, rather than use published functions.

Measurements of the proton light output function of the organic liquid scintillator NE213 in several detectors

An accurate energy calibration of organic scintillation counters by means of γ-rays is described. The position of the Compton edge has been precisely determined comparing measured with calculated spectra. The calculation includes wall and light pipe effects and the influence of channel dependent pulse height resolution. Relations are given for the position of the maximum and the half maximum of a Compton spectrum as a function of the incident photon energy and the resolution of the detector. Results are given with uncertainties smaller than 1 %.

G. Dietze

Papers

Energy calibration of NE-213 scintillation counters by δ-rays