Development of Dose Monitoring System Applicable to Various Radiations with Wide Energy Ranges

Abstract

A new inventive radiation dose monitor, designated as DARWIN (Dose monitoring system Applicable to various Radiations with WIde energy raNges), has been developed for monitoring doses in workspaces and surrounding environments of high energy accelerator facilities. DARWIN is composed of a phoswitch-type scintillation detector, which consists of liquid organic scintillator BC501A coupled with ZnS(Ag) scintillation sheets doped with 6 Li, and a data acquisition system based on a Digital-Storage-Oscilloscope. Scintillations from the detector induced by thermal and fast neutrons, photons and muons were discriminated by analyzing their waveforms, and their light outputs were directly converted into the corresponding doses by applying the G-function method. Characteristics of DARWIN were studied by both calculation and experiment. The calculated results indicate that DARWIN gives reasonable estimations of doses in most radiation fields. It was found from the experiment that DARWIN has an excellent property of measuring doses from all particles that significantly contribute to the doses in surrounding environments of accelerator facilities-neutron, photon and muon with wide energy ranges. The experimental results also suggested that DARWIN enables us to monitor small fluctuation of neutron dose rates near the background-level owing to its high sensitivity.

Development of a light-weight portable neutron survey meter

“…To improve the deviation, which mentioned above, of neutron energy response from h*(10), we are now applying the G-function method [10] using the actual neutron field spectra at nuclear facilities [11] in the energy region below 400 keV.…”

Measurement of Response Functions of a Liquid Organic Scintillator for Neutrons up to 800 MeV

“…We have developed a new dose-monitoring system applicable to various types of radiation over a wide energy range (DARWIN) 3) for monitoring doses from neutrons, photons, and muons in the workspaces and surrounding environments of accelerator facilities. A BC501A liquid organic scintillator was employed as a radiation detector for neutrons above 1.2 MeV as well as for photons and muons in DARWIN, because this scintillator has a high detection efficiency and a good capability of distinguishing neutrons and photons.…”

“…The neutron dose is assessed from the light output by applying the G-function 4) that is derived from a set of the response functions of the BC501A scintillator and the dose conversion coefficients. The performance of DARWIN has been verified in the energy region from thermal to 80 MeV 3,[5][6][7] in various neutron fields. The upper energy limit is determined by the available response function for the scintillator using SCINFUL code, 8) which evaluates the response function for neutrons from 0.1 to 80 MeV based on a multibodybreakup model.…”