Complexities of gamma-ray line intensities from the lunar surface

Abstract

Assuming different abundances of the Apollo lunar soil samples and the average spectrum of galactic cosmic ray protons, energy spectra of neutrons and gamma rays and emission rates of gamma-ray lines from major elements have been estimated by using the reviewed Monte Carlo simulation library Geant4 and nuclear data. Previously, such libraries were not able to reproduce gamma-ray lines properly for the planetary application. Results clearly show that the emission rate of gamma rays heavily depends not only on the chemical abundance but also neutron flux within the lunar subsurface. While the intensities of gamma-ray lines are mostly proportional to elemental abundances, the intensity per unit elemental abundance can vary. Such a complex correlation is attributed to the change in neutron flux within the lunar subsurface and petrological restriction of elemental variation.

Radiation Doses for Human Exposed to Galactic Cosmic Rays and Their Secondary Products on the Lunar Surface

“…Therefore, in this study, the γ ray dose from the natural radioactive isotopes was assumed to be the same as that on the Earth; it is 0.48 mSv/yr (United Nations Scientific Committee on the Effects of Atomic Radiation, 2000). The details of the dose calculation for neutron and γ ray are reported in Hayatsu et al (2007) and the further results from the simulation calculation for production and transportation of those secondaries is described in the paper (Yamashita et al, 2008). (Simpson, 1983) with the data from ACE/CRIS (Israel ., 2005).…”

“…(2-5) and with the parameters from Lal (1988) and McKinney et al (2006) as shown in Table 1, is isotropically irradiated to the central point on a surface of the cube. For the leakage fluxes of neutrons and γ rays, the difference between the GCR flux in this work and that in previous one shown in Table 1 is rather small in the estimate of dose on the lunar surface (Yamashita et al, 2008). The cube was made from average composition of soils found in Apollo 16 landing site (Heiken et al, 1991).…”

“…The intensities of GCR-induced neutrons and γ rays on the lunar surface were calculated numerically by simulating their production and transportation in the Moon using a Monte Carlo simulation library Geant4 release 8.0.p01 (Agostinelli et al, 2003) with the modified nuclear data library G4NDL3.9 (Yamashita et al, 2008) and the hadronic interaction model called QGSP_BERT_HP. In the Monte Carlo calculations, the lunar subsurface was modeled as 50 × 50 × 50 m 3 cubes, and GCR protons with an energy spectrum represented by Eq.…”

Gamma-ray spectrometer (GRS) for lunar polar orbiter SELENE

“…The energy and intensity of the lines identify the species of elements and their abundance in the lunar surface, respectively Reedy, 1978;Evans et al, 1993;Yamashita et al, 2008).…”

HZE Particle and Neutron Dosages from Cosmic Rays on the Lunar Surface

“…The fluences of GCR-produced neutrons and gamma rays on the lunar surface are calculated by using the Monte Carlo simulation library Geant4 release 8.0.p01 with the modified nuclear data library G4NDL3.9 12) and the hadronic interaction model called QGSP_BERT_HP. The lunar surface model is composed of materials with an averaged composition of soils brought back from the Apollo 16 landing site as the sample of highland and the Apollo 11 landing site as the sample of mare region.…”