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Manuscript Title: COSMO: a program to estimate spallation radioactivity produced in a pure substance by exposure to cosmic radiation on the earth.
Authors: C.J. Martoff, P.D. Lewin
Program title: COSMO
Catalogue identifier: ACJN_v1_0
Distribution format: gz
Journal reference: Comput. Phys. Commun. 72(1992)96
Programming language: Fortran.
Computer: 80C88 MICROCOMPUTER.
Operating system: DOS 3.31.
Keywords: Spallation, Cosmogenesis, Cosmic rays, Radiation, Radiati.
Classification: 21.1.

Nature of problem:
Particularly in low-level counting applications (design of Dark Matter and neutrinoless-beta beta decay experiments), it is important to have estimates of the cosmogenic activity produced in detector and cryostat materials by interaction of cosmic rays. With straightforward modifications, program would also be useful in computing induced radioactivity in accelerator components exposed to nucleon beams of energy greater than 50-100 MeV.

Solution method:
The variation of spallation, evaporation, fission, and peripheral reaction cross sections with nucleon energy and target and product charge and mass numbers have been fitted to relatively simple analytic forms by Silberberg and Tsao. The program COSMO augments these with approximations of (p,xn) reactions from work of Church, as well as a table containing all product radionuclides with lifetimes between 25 days and 5 million years. An approximate energy spectrum for cosmic ray nucleons in the earth's atmosphere from the work of Lal and Peters is used. The program permits the user to choose between three modes of calculation: an excitation curve showing production of any specified nuclide from any specified target nuclide as a function of beam energy; a mass yield curve showing total production of nuclides of a given mass number from a given target nuclide at a specified beam energy; or a list of all radionuclide activities produced from a specified target nuclide exposed to the approximate cosmic ray spectrum, for specified exposure time and decay time since exposure ended.

Restrictions:
Only targets with atomic number less than 83 and mass number less than 210 are treated completely. Production of boron isotopes is not well represented by the Silberberg and Tsao fits. The treatment of (p,xn) reactions is based on very limited data. Overall accuracy of the Silberberg and Tsao fits for beam energies above 100 MeV is expected to be of the order of 20 percent in the cross section, with the above noted exceptions. The assumption of charge independence is used to calculate production by cosmic ray neutrons using spallation cross sections for proton induced reactions. This assumption is valid at the 25 percent level for beam energies above 75-100 MeV.

Running time:
On an 80C88 microcomputer running at 8 MHz under DOS3.31, with Microsoft optimizing FORTRAN 77 compiler, about 2 seconds for each medium mass product nuclide and each energy point.