Irradiation tests performed on the Herschel/Pacs bolometer arrays

TL;DR

This study evaluates the radiation effects on Herschel/Pacs bolometer arrays through irradiation tests, demonstrating their suitability for space applications and highlighting the need for software correction of radiation-induced signal perturbations.

Contribution

The paper presents the first irradiation testing of Herschel/Pacs bolometers, analyzing radiation effects and proposing methods for signal correction to ensure space operation reliability.

Findings

Gamma ray irradiation did not degrade detector performance significantly.

Impact location influences signal perturbation shape, requiring software deglitching.

Detector parameters like crosstalk and thermal time constants were measured.

Abstract

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.