  A new concept of bolometer arrays is used for the imager of PACS, one of the
three instruments aboard the future Herschel space observatory. Within the
framework of PACS photometer characterization, irradiation tests were performed
on a dedicated bolometer array in order to study long-term and short-term
radiation effects. The main objective was to study particles impacts on the
detectors applicable to future observations in orbit and possible hard and/or
soft curing to restore its performances. Cobalt-60 gamma ray irradiations did
not show significant degradation, so we mainly focused on single events effects
(SEE). Protons and alphas irradiations were then performed at the Van de Graaf
tandem accelerator at the Institut de Physique Nucleaire (IPN, Orsay, France),
respectively at 20MeV and 30MeV. Observation showed that the shape of signal
perturbations clearly depends on the location of the impacts either on the
detector itself or the read-out circuit. Software curing has then to be
anticipated in order to deglitch the signal. This test gives also a unique
opportunity to measure some parameters of the detector: electrical crosstalk
and thermo- electrical time constant. However a detailed bolometer model is
necessary to understand the contribution of the thermal response in relation
with the electrical response. It will be the second step of our study. Finally
the complete radiation evaluation proved that this detector can be used in
spatial experiments.

Instrumentation and Methods for Astrophysics