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Kinetic Inductance Detectors (KIDs)

Kinetic Inductance Detectors (KIDs) are superconducting microresonator devices (in the most simple picture, an RLC circuit made of superconductor), with very high Q factors (104-106). When resonators are coupled to transmission line, the interaction of a photon or a phonon with the detector breaks Cooper Pairs (CPs) and modify the resonator transmission (S21). The resonant frequency typically ranges between 0.1-10 GHz.

The key features of KIDs consist in the excellent intrinsic energy resolution, and in the possibility of easily tuning each detector to a diff.erent resonant frequency. This natural aptitude to frequency multiplexed read-out allows to operate hundreds or thousands of KIDs with two cryogenic cables and one cryogenic amplifier. In addition, since the electronics is located at room temperature, the installation of KIDs arrays on detectors would only require minor modifications to the pre-existing cryogenic facilities.

Experimentally the signal is obtained by exciting the circuit at the resonant frequency, and by measuring the phase (inductance) and amplitude (resistance) variations induced by energy releases. Many KIDs can be coupled to the same
feedline, and can be multiplexed by making them resonate at slightly diff.erent frequencies. The resonant frequency of each resonator can be easily varied by slightly changing the layout of the capacitor and/or inductor of the circuit.

From their first applications in photon detection, KIDs became rapidly subject
of several research activities in different physics sectors such as astrophysics, x ray sciences, particle physics; proving to be very versatile devices.

Current projects:

CALDER (particle physics)

OLIMPO (astrophysics)

PNRA KID (astrophysics)

MOBIKID (cosmology)

Incoming:  cooming soon


d.ssa Maria Gabriella Castellano

(a) Photons with hν>2Δ absorbed in the superconductor film (the inductor) producing quasiparticles

(a) Photons with hν>2Δ absorbed in the su perconductor film (the inductor) producing quasiparticles. (b) Equivalent circuit to measure these quasiparticles

Power (c) and phase (d) of a microwave excitation signal sent trough the resonator before (straight line) and after (dotted line) an energy absorption

Photons absorption : the resonance shift to low frequency and get shallower