Perspectives of New Scintillators for Planetary Gamma-ray Spectroscopy
- Paper number
IAC-05-A3.P.21
- Author
Mr. Benoit Pirard, Centre d Etude Spatiale des Rayonnements (CESR - CNRS/UPS), France
- Coauthor
Dr. Claude d Uston, Centre d Etude Spatiale des Rayonnements (CESR - CNRS/UPS), France
- Coauthor
Dr. Sylvestre Maurice, Centre d Etude Spatiale des Rayonnements (CESR - CNRS/UPS), France
- Coauthor
Dr. Olivier Gasnault, Centre d Etude Spatiale des Rayonnements (CESR - CNRS/UPS), France
- Year
2005
- Abstract
Since the beginning of planetary missions, gamma-ray spectroscopy has been widely used in the study of planetary bodies (with tenuous atmospheres) such as the Moon, Mars and some asteroids. The technique consists in measuring fluxes of gamma-rays emitted from the surface by elements naturally radioactive or activated by cosmic-ray particles bombardment. The detection of a lot of lines at specific energies in the spectrum reveals the presence of some elements in the surface such as O, Fe, Si, Ti, Mg, Al, H, C, U, Th, K, etc. For a given chemical element, the abundance can be estimated from the intensities of the corresponding lines. Provided that the detection statistics is high enough (which requires a high spectral resolution, a high efficiency and a long observation time), it is even possible to map abundance distribution for several elements. A lot of new scintillation materials have been developed in the last decade, especially for a use in high energy physics and medical imaging (Positron Emission Tomography). Some of them, in particular Cerium doped Lanthanum Bromide (LaBr3:Ce), would present interesting properties for gamma-ray spectroscopy. Coupled with low noise readout devices and highly reflective coatings, these scintillators will certainly replace conventional scintillation materials (NaI:Tl, CsI:Tl) in the coming years and, in some cases, they will compete with semiconductor detectors (CdZnTe, HPGe). Although they have a poorer energy resolution than high-purity Germanium detectors, they do not require cooling systems and could be envisaged for future planetary missions where resources (mass, power) are limited. The present study gives an evaluation of the advantages and performance limits of these new scintillators for a use in planetary exploration. Highlight is put on their detection performances (especially on their spectral resolution) with respect to conventional scintillators and Germanium detectors. Although these promising materials remain at the state of small experimental prototypes, they present a particular potential for future planetary gamma-ray spectroscopy, provided that some critical technical issues are answered. They will not replace Germanium detectors (giving the best science return) for complete investigations of planetary bodies but they will certainly increase the limited number of detected lines with respect to conventional scintillators and will be therefore particularly attractive to study unexplored planetary bodies.
- Abstract document