Other
Scientific paper
Apr 2003
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2003eaeja.....5420c&link_type=abstract
EGS - AGU - EUG Joint Assembly, Abstracts from the meeting held in Nice, France, 6 - 11 April 2003, abstract #5420
Other
Scientific paper
A variety of observations e.g. Aa index, heliospheric magnetic field intensity and activity of cosmogenic 44Ti in meteorites suggest that the galactic cosmic ray (GCR) flux in the interplanetary space has decreased by a factor about two during the past two centuries [1]. The activity of 44Ti (T1/2 = 59.2 y) is small, about 1 dpm/kg , even in fresh meteorites and require highly sensitive and selective gamma ray spectrometers and long term counting for non destructive measurement of its daughter 44Sc.We have designed a hyperpure Ge-NaI(Tl) coincidence spectrometer operating under the Monte dei Cappuccini in Torino for these measurements [2]. It is however desirable to use an isotope pair such as 42Ar /44Ti , rather than a single isotope, since the ratio is largely independent of shielding depth but the activity of 42Ar (T1/2 = 33 y) is even smaller , expected to be 0.3 dpm/kg. To be able to measure 42Ar in meteorites via 1524 KeV gamma line of its daughter 42K , and to further improve upon statistical precision of 44Ti, we have set up a larger (581 cm3) hyperpure Ge detector operating in coincidence with a 100 kg NaI(Tl) crystal assembly. This system should allow us to confirm the results of decreasing GCR variations, mentioned above. In addition, if we can achieve low backgrounds, we may be able to measure some other radionuclides produced by neutron capture in meteorites and several cosmogenic radionuclides in small planetary samples like asteroids, comets and lunar rocks which may become available in the near future. We wish to acknowledge our deep gratitude to late Professor G. Bonino who designed and set up the new detector system. [1] G. Bonino, G. Cini Castagnoli, D. Cane, C. Taricco and N. Bhandari,Proc. XXVII Intern. Cosmic Ray Conf. (Hamburg, 2001) 3769-3772. [2] G. Bonino, N. Bhandari, G. Cini Castagnoli,Nuovo Cimento 15, 99-104, 1992
Bhandari Narendra
Cane Daniele
Castagnoli Cini G.
Taricco Carla
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