Spectrometry using the PTB neutron multisphere spectrometer (NEMUS) at flight altitudes and at ground level

Evaluation of Geomagnetic Latitude Dependence of the Cosmic-ray Induced Environmental Neutrons in Japan

“…14) The average neutron dose equivalent rate of 8.5 nSv h À1 has been derived from the measurement at the Physikalisch-Technische Bundesanstalt (PTB) site. 6) These values are overestimated in low geomagnetic latitude areas, since smaller neutron fluence and dose rate were obtained in our former study in Japan than those obtained in high geomagnetic latitude. 13) Detailed information is required on total fluence rate and energy spectrum of the cosmic-ray induced neutrons with respect to the geomagnetic latitude, in order to assess the natural neutron dose rates at sea level in Japan.…”

“…These values were lower than those obtained by other works performed in the higher geomagnetic latitude area for fitting curve (H*(10)) fitting curve in isotropic geometry Fig. 6 Geomagnetic latitude variation of the cosmic-ray neutron ambient dose equivalent rate and neutron effective dose rate in isotropic geometry 118 example, 0.0122 n cm À2 s À1 and 9.3 nSvÁh À1 in the United States, 4) 8.5 nSv h À1 in Germany, 6) and 0.013 n cm À2 s À1 , and 9.0 nSvÁh À1 estimated by UNSCEAR 2000. 14) 3.…”

“…[1][2][3][4][5][6][7] Very few results on cosmic-ray neutrons at sea level in Japan have been available. 8) In recent years, several experiments have been performed at low geomagnetic latitudes.…”

Influence of Bonner sphere response functions above 20 MeV on unfolded neutron spectra and doses

“…The differences observed are discussed in terms of neutron fluence rates obtained below 0.4 eV (thermal neutrons), between 0.4 eV and 100 keV (epithermal neutrons), between 100 keV and 20 MeV (evaporation neutrons), and above 20 MeV (cascade neutrons). These four energy regions typically describe secondary neutrons from cosmic radiation (e.g., Wiegel et al, 2002;Leuthold et al, 2007;Rühm et al, 2009a,b) or those present behind shieldings of high-energy particle accelerators (Mitaroff and Silari, 2002;Wiegel et al, 2009). The observed differences are also discussed in terms of ambient dose equivalent for these energy regions.…”

Measurements of Cosmic-Ray Neutron Energy Spectra from Thermal to 15 MeV with Bonner Ball Neutron Detector in Aircraft

“…[2][3][4][5][6][7][8][9][10][11] However, only one neutron spectrum measurement on board was performed in the low cutoff rigidity region over Japan on Feb. 27,1985, by Nakamura et al 12) A multimoderator spectrometer, the so-called Bonner ball detector, is the standard neutron spectrometer used for radiological protection and environmental measurements, where the neutron energy range is below 15 MeV. In most aircraft measurements of the cosmic neutron energy spectrum, [2][3][4]6) a specially constructed Bonner ball spectrometer, to which a metal shell converter was added, was used to extend the energy range over 1 GeV. However, the accuracy of this instrument is insufficient for measuring the cosmic neutron spectrum and evaluating the exposure dose at aviation altitude in the energy region above 15 MeV with the Bonner ball, due to the absence of verification by other neutron spectrometers.…”