Construction of monoenergetic neutron calibration fields using 45Sc(p, n)45Ti reaction at JAEA

Abstract

The 8 and 27 keV monoenergetic neutron calibration fields have been developed by using (45)Sc(p, n)(45)Ti reaction. Protons from a 4-MV Pelletron accelerator are used to bombard a thin scandium target evaporated onto a platinum disc. The proton energies are finely adjusted to the resonance to generate the 8 and 27 keV neutrons by applying a high voltage to the target assemblies. The neutron energies were measured using the time-of-flight method with a lithium glass scintillation detector. The neutron fluences at a calibration point located at 50 cm from the target were evaluated using Bonner spheres. A long counter was placed at 2.2 m from the target and at 60 degrees to the direction of the proton beam in order to monitor the fluence at the calibration point. Fluence and dose equivalent rates at the calibration point are sufficient to calibrate many types of the neutron survey metres.

Neutron fluence monitoring system in mono-energetic neutron fields at FRS / JAEA

“…The calibration coefficients K were determined for every energy point by measuring the reference neutron fluence at the calibration point using neutron detectors such as a Bonner sphere, a proton recoil proportional counter and a semiconductor detector with a polyethylene convertor [1][2][3]. The correction factor S is determined for every calibration by measuring the ratio of monitor counts with and without the instruments and their supporting materials.…”

“…For the 8 and 27 keV fields, the aimed neutron can be produced by adjusting the proton energy to the resonance peak of the 45 Sc(p,n) 45 Ti reaction with a target voltage control system [2].…”

“…Mono-energetic neutron calibration fields were developed at the Facility of Radiation Standards (FRS) in the Japan Atomic Energy Agency (JAEA) using a 4MV Pelletron accelerator [1][2][3]. The neutron energies shown in Figure 1 are available for determining energy responses of neutron dosemeters.…”

Development of the Neutron Calibration Fields using Accelerators at FRS and TIARA of JAEA

“…The position among several positions available from the arrangement in the room was determined to make the contribution of inscattered neutrons from the devices to be calibrated and their supporting materials small as possible. Calibration coefficients K LC , which are used to calculate the reference neutron fluence at a calibration point from the counts of the LC N LC , were determined from the fluence measured by using the detectors mentioned in the following sections 1,2) .…”

“…Therefore, such monoenergetic neutron calibration fields below 20 MeV have been developed as the secondary standard fields using a 4 MV Van-de-Graaf accelerator at the Facility of Radiation Standards (FRS) of the Japan Atomic Energy Agency (JAEA) 1,2) . The calibration fields of 8, 144, 250, 565 keV, 5.0 and 14.8 MeV neutrons are available at FRS (Fig.…”