For simultaneous spectrometry of neutrons and photons in mixed fields, a spectrometer with the liquid scintillator NE213 is used. The separation of the events induced by photons and neutrons is carried out by fast analog pulse shape analysis of the measurement signals which are detected using a multiparameter data acquisition system. The further analysis takes place separately for photon and neutron events in the energy ranges
0.1 MeV to
10 MeV for photons and
1 MeV to
20 MeV for neutrons.
One prerequisite for spectrometry is the exact knowledge of the response of the spectrometer to the two kinds of radiation. With the calculated energy-dependent response (using Monte Carlo methods: NRESP for neutrons, PHRESP for photons) and the measured pulse height spectra of the neutrons and photons, the spectral fluences are determined by mathematical deconvolution methods based on different principles.
The scintillation spectrometer is employed, among other things, to characterize the mixed radiation fields from radionuclide sources. The measured fluences and the energy-dependent fluence-to-dose conversion coefficients yield the dose fractions for the neutrons and photons of these radiation fields which are used for the calibration of neutron area dosemeters and for irradiations of neutron personal dosemeters.
Literature:
H. Klein, S. Neumann: Neutron and photon spectrometry with liquid scintillation detectors in mixed fields, Nucl. Instrum. Meth. (in print)
M. Matzke: Unfolding of Pulse Height Spectra: The HEPRO Program System, PTB-Bericht, N-19, 1994
Contact
Dr. Andreas Zimbal
Phone: +49 (0) 531-592-6530
e-mail: Andreas.Zimbal@ptb.de
