  Skipper CCDs are a mature detector technology that has been suggested for
future space telescope instruments requiring sub-electron readout noise in the
near-ultraviolet to the near-infrared. While modern skipper CCDs inherit from
the radiation-tolerant p-channel detectors developed by LBNL, the effects of
high doses of ionizing radiation on skipper CCDs (such as those expected in
space) remains largely unmeasured. We report preliminary results on the
performance of p-channel skipper CCDs following irradiation with 217-MeV
protons at the Northwestern Medicine Proton Center. The total nonionizing
energy loss (NIEL) experienced by the detectors exceeds 6 years at the
Sun-Earth Lagrange Point 2 (L2). We demonstrate that the skipper amplifier
continues to function as expected following this irradiation. Owing to the low
readout noise of these detectors, controlled irradiation tests can be used to
sensitively characterize the charge transfer inefficiency, dark current, and
the density and time constants of charge traps as a function of proton fluence.
We conclude with a brief outlook toward future tests of these detectors at
other proton and gamma-ray facilities.
