Cosmogenic activation of materials

Abstract

Experiments looking for rare events like the direct detection of dark matter particles, neutrino interactions or the nuclear double beta decay are operated deep underground to suppress the effect of cosmic rays. But the production of radioactive isotopes in materials due to previous exposure to cosmic rays is an hazard when ultra-low background conditions are required. In this context, the generation of long-lived products by cosmic nucleons has been studied for many detector media and for other materials commonly used. Here, the main results obtained on the quantification of activation yields on the Earth's surface will be summarized, considering both measurements and calculations following different approaches. The isotope production cross sections and the cosmic ray spectrum are the two main ingredients when calculating this cosmogenic activation; the different alternatives for implementing them will be discussed. Activation that can take place deep underground mainly due to cosmic muons will be briefly commented too. Presently, the experimental results for the cosmogenic production of radioisotopes are scarce and discrepancies between different calculations are important in many cases, but the increasing interest on this background source which is becoming more and more relevant can help to change this situation.

Production rate measurement of Tritium and other cosmogenic isotopes in Germanium with CDMSlite

“…Several competing parameterizations of the sea-level neutron flux exist, as noted in Ref. [29]. We adopt the model of Gordon [43] for consistency with other recent estimates [32,34,35].…”

“…For a review of cosmogenic production rates in various materials, including germanium, see Ref. [29]. As Table 2 demonstrates, the different published calculations are not always in agreement with one another or with the sparse experimental results.…”

Low background techniques in bolometers for double-beta decay search

“…in. 53,[131][132][133] Concerning materials of interest for bolometric ββ experiments, cosmogenic radioisotopes of Co are common for copper, 92, 93, 124 65 Zn is often registered in Zn-containing detectors, 87, 134-137 75 Se was observed in ZnSe, 136 116 CdWO 4 exhibits 110m Ag, 76 isotopes of Sb and metastable Te isotopes are typical for TeO 2 . 82,83,124,138,139 In order to point out possible cosmogenic activation issues, we used the program COSMO 140 to calculate the production rates after one month of exposure and same time of de-activation (cooling).…”

Naturally occurring 32Si and low-background silicon dark matter detectors

“…32 Si) in natural silicon, unlike many other detector materials of interest to the astroparticle physics community (e.g. 68 Ge in germanium crystals and 39 Ar in argon gas [10]). In Ref.…”

“…rock and dirt). However, 32 Si is not typically suggested as a radio-tracer from terrestrial production and does not appear to have been studied along with the five radionuclides commonly used for tracing materials of terrestrial origin: 10 Be, 14 C, 26 Al, 36 Cl and 39 Ar [19,20]. For this reason, we do not consider this potential terrestrial source vector for 32 Si.…”