CONCERTO: Digital processing for finding and tuning LEKIDs
Résumé
We describe the on-line algorithms developed to probe Lumped
Element Kinetic Inductance Detectors (LEKID) in this paper. LEKIDs
are millimeter wavelength detectors for astronomy. LEKID arrays are
currently operated in different instruments as: NIKA2 at the IRAM
telescope in Spain, KISS at the Teide Observatory telescope in
Tenerife, and CONCERTO at the APEX 12-meter telescope in
Chile. LEKIDs are superconducting microwave resonators able to
detect the incoming light at millimeter wavelengths and they are
well adapted for frequency multiplexing (currently up to 360 pixels
on a single microwave guide). Nevertheless, their use for
astronomical observations requires specific readout and acquisition
systems both to deal with the instrumental and multiplexing
complexity, and to adapt to the observational requirements (e.g. fast sampling rate, background variations, on-line calibration,
photometric accuracy, etc). This paper presents the different steps
of treatment from identifying the resonance frequency of each LEKID
to the continuous automatic control of drifting LEKID resonance
frequencies induced by background variations.