Impact of particles on the Planck HFI detectors: Ground-based measurements and physical interpretation

¹ Laboratoire de Physique Subatomique et de Cosmologie, CNRS/IN2P3, Université Joseph Fourier Grenoble I, Institut National Polytechnique de Grenoble, 53 rue des Martyrs, 38026 Grenoble Cedex, France
e-mail: catalano@lpsc.in2p3.fr
² School of Physics and Astronomy, Cardiff University, Queens Buildings, The Parade, Cardiff, CF24 3AA, UK
³ Institut d’Astrophysique Spatiale, CNRS (UMR 8617) Université Paris-Sud 11, Bâtiment 121, 91405 Orsay, France
⁴ Institut Néel, CNRS, Université Joseph Fourier Grenoble I, 25 rue des Martyrs, 38042 Grenoble, France
⁵ Astroparticule et Cosmologie, CNRS (UMR 7164), Université Denis Diderot Paris 7, Bâtiment Condorcet, 10 rue A. Domon et Léonie Duquet, 75205 Paris, France
⁶ California Institute of Technology, Pasadena, California, USA
⁷ Jet Propulsion Laboratory, California Institute of Technology, 4800 Oak Grove Drive, Pasadena, California, USA
⁸ IPN: Institut de Physique Nucléaire, CNRS/IN2P3, Université Paris-Sud 11, 91406 Orsay cedex, France
⁹ LERMA, CNRS, Observatoire de Paris, 61 avenue de l’Observatoire, 75014 Paris, France
¹⁰ IPAG: Institut de Planétologie et d’Astrophysique de Grenoble, Université Joseph Fourier, Grenoble 1/CNRS-INSU, UMR 5274, 38041 Grenoble, France
¹¹ European Space Agency, ESTEC, Keplerlaan 1, 2201 AZ Noordwijk, The Netherlands
¹² Department of Physics, Princeton University, Princeton, New Jersey, USA
¹³ CNRS, IRAP, 9 Av. colonel Roche, BP 44346, 31028 Toulouse Cedex 4, France

Received: 22 March 2014
Accepted: 12 August 2014

Abstract

The Planck High Frequency Instrument (HFI) surveyed the sky continuously from August 2009 to January 2012. Its noise and sensitivity performance were excellent (from 11 to 40 aW Hz^-1), but the rate of cosmic-ray impacts on the HFI detectors was unexpectedly higher than in other instruments. Furthermore, collisions of cosmic rays with the focal plane produced transient signals in the data (glitches) with a wide range of characteristics and a rate of about one glitch per second. A study of cosmic-ray impacts on the HFI detector modules has been undertaken to categorize and characterize the glitches, to correct the HFI time-ordered data, and understand the residual effects on Planck maps and data products. This paper evaluates the physical origins of glitches observed by the HFI detectors. To better understand the glitches observed by HFI in flight, several ground-based experiments were conducted with flight-spare HFI bolometer modules. The experiments were conducted between 2010 and 2013 with HFI test bolometers in different configurations using varying particles and impact energies. The bolometer modules were exposed to 23 MeV protons from the Orsay IPN Tandem accelerator, and to ²⁴¹Am and ²⁴⁴Cm α-particle and ⁵⁵Fe radioactive X-ray sources. The calibration data from the HFI ground-based preflight tests were used to further characterize the glitches and compare glitch rates with statistical expectations under laboratory conditions. Test results provide strong evidence that the dominant family of glitches observed in flight are due to cosmic-ray absorption by the silicon die substrate on which the HFI detectors reside. Glitch energy is propagated to the thermistor by ballistic phonons, while thermal diffusion also contributes. The average ratio between the energy absorbed, per glitch, in the silicon die and thatabsorbed in the bolometer is equal to 650. We discuss the implications of these results for future satellite missions, especially those in the far-infrared to submillimeter and millimeter regions of the electromagnetic spectrum.