Study of terrestrial γ-ray background in presence of variable radioactivity from rain water |
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| Institution: | 1. Tata Institute of Fundamental Research, Mumbai 400005, India;2. GRAPES-3 Experiment, Cosmic Ray Laboratory, Raj Bhavan, Ooty 643001, India;3. J.C. Bose Institute, 93/1, A.P.C. Road, Kolkata 700009, India;1. KTH Royal Institute of Technology, Department of Physics, 106 91 Stockholm, Sweden;2. The Oskar Klein Centre for Cosmoparticle Physics, AlbaNova University Centre, 106 91 Stockholm, Sweden;3. Hiroshima University, Department of Physical Science, Hiroshima 739-8526, Japan;4. Max-Planck-Institut für Physik, D-80805 München, Germany;1. Gran Sasso Science Institute, viale Francesco Crispi, 7 L’Aquila 67100 (AQ), Italy;2. Institute for Space Sciences (CSIC/IEEC), Barcelona E-08193, Spain;3. Dublin Institute of Advanced Studies, 10 Burlington Road, Dublin 4, Ireland;4. Max-Planck-Institut für Kernphysik, Saupfercheckweg 1, Heidelberg D-69117, Germany;1. Instituto de Física Teórica, Universidade Estadual Paulista, Rua Dr. Bento Teobaldo Ferraz 271, 01140-070 São Paulo, SP, Brazil;2. Astrophysics Science Division, NASA Goddard Space Flight Center, Greenbelt, MD 20771, United States;1. Institute for Nuclear Research, 60th October Anniversary pr. 7A, Moscow 117312, Russia;2. Joint Institute for Nuclear Research, Dubna 141980, Russia;3. Irkutsk State University, Irkutsk 664003, Russia;4. Skobeltsyn Institute of Nuclear Physics MSU, Moscow 119991, Russia;5. Nizhni Novgorod State Technical University, Nizhni Novgorod 603950, Russia;6. St. Petersburg State Marine University, St. Petersburg 190008, Russia;7. EvoLogics GmbH, Berlin, Germany;1. Institute of Nuclear Physics PAN, Kraków, Poland;2. Institute for Nuclear Physics (IKP), Karlsruhe Institute of Technology, Karlsruhe, Germany;3. Argelander Institute for Astronomy (AIfA), Bonn, Germany;1. Instituto de Ciência e Tecnologia, Universidade Federal de Alfenas, Rodovia José Aurélio Vilela, 11999, Cidade Universitária, CEP 37715-400, Poços de Caldas, MG, Brazil;2. Escola de Ciência e Tecnologia, Universidade Federal do Rio Grande do Norte, Campus Universitário, s/n, CEP 59072-970, Natal, Brazil |
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| Abstract: | A number of groups have reported significant reduction in the flux of low energy (0.1–3 MeV) γ-rays in observations carried out during the past total solar eclipses. However, the contribution of the radon induced radioactivity to the overall γ-ray background can become substantial, especially during episodes of rain. Depending upon the pattern of the rainfall radon induced γ-ray background may vary significantly on time scales of ∼10 min, making the interpretation of the data in terms of an extraterrestrial effect such as a total solar eclipse rather difficult. A reliable estimate of the low energy terrestrial γ-ray (TGR) background is necessary before attempting to measure the possible contribution of any extraterrestrial phenomenon. The knowledge of the precise energies and branching ratios of radon and other radio-isotope induced γ-rays was exploited to accurately reproduce the TGR background, even in the presence of a large and variable contribution from radon induced radioactivity from fresh rain water. The measurement of the TGR background has paved the way for studying the variation of the soft γ-ray flux during the long duration total solar eclipse that occurred on 22 July 2009 in the middle of the Monsoon season in India. |
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