  We revisit calculations of the cosmogenic production rates for several
long-lived isotopes that are potential sources of background in searching for
rare physics processes such as the detection of dark matter and neutrinoless
double-beta decay. Using updated cosmic-ray neutron flux measurements, we use
TALYS 1.0 to investigate the cosmogenic activation of stable isotopes of
several detector targets and find that the cosmogenic isotopes produced inside
the target materials and cryostat can result in large backgrounds for dark
matter searches and neutrinoless double-beta decay. We use previously published
low-background HPGe data to constrain the production of $^{3}H$ on the surface
and the upper limit is consistent with our calculation. We note that cosmogenic
production of several isotopes in various targets can generate potential
backgrounds for dark matter detection and neutrinoless double-beta decay with a
massive detector, thus great care should be taken to limit and/or deal with the
cosmogenic activation of the targets.
