First results of a cryogenic optical photon-counting imaging spectrometer using a DROID array

Abstract

Context. We present the first system test in which we demonstrate the concept of using an array of Distributed Read Out Imaging Devices (DROIDs) for optical photon detection. Aims. After the successful S-Cam 3 detector, the next step in the development of a cryogenic optical photon counting imaging spectrometer under the S-Cam project is to increase the field of view using DROIDs. With this modification the field of view of the camera has been increased by a factor of five in a given area while keeping the number of readout channels the same. Methods. The test has been performed using the flexible S-Cam 3 system and exchanging the 10 × 12 Superconducting Tunnel Junction array for a 3 × 20 DROID array. The extra data reduction needed with DROIDs is performed offline. Results. We show that, although the responsivity (number of tunnelled quasiparticles per unit of absorbed photon energy, e − /eV) of the current array is too low for direct astronomical applications, the imaging quality is already good enough for pattern detection and will improve further with increasing responsivity. Conclusions. The obtained knowledge can be used to optimise the system for the use of DROIDs.

Visible/Infrared Imaging Spectroscopy and Energy-Resolving Detectors

“…The instrument successfully carried out observations of transiting exoplanets (Stankov et al 2007), eclipsing white dwarfs (eclipse-timing and mapping), and pulsating white dwarfs as well as the fast variability properties of black hole candidates, neutron stars, and pulsars. As the final step in the development of the S-Cam instrument family, an STJ array formed by three 20-element DROID detectors (see Section 4.1.1) was developed and tested (Hijmering et al 2010). The active region of each DROID was divided into virtual pixels, effectively resulting in a 33 × 20-pixel array and providing a field of view of 20 arcsec × 30 arcsec on the WHT with an average resolving power of ∼6 at 400 nm.…”