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Description
The MKIDs are devices fabricated with superconducting thin film technology. The principle of operation is counting the number of quasiparticles excited by the interaction of a particle. In the case of a photon, this is absorbed producing a breaking of cooper pairs which change the density of quasiparticles of the detector. For other particles massive as neutrinos or WIMPS the quasiparticles come by the production of phonons of the crystal lattice of the superconductor. Each MKID makes up of hundreds of thousands of resonators (pixels), one resonator is capable of determining the position, arrival time, and energy of incoming particles.
In this work, we will show that, in spite of having high uniformity in the critical temperature of an MKID. We have a low population of generated quasiparticles when a photon is absorbed. First, the measurement of the critical temperature (We tested 2 MKID from one wafer and 2 from another wafer) is done through the fit of the fractional resonance frequency change. The results show that MKIDs from the same wafer has the same critical temperature. However, the resonance frequency and loaded quality factor show a clear discrepancy. The technics of characterization and results will be shown.
The process of absorption in a superconducting is explained through the energy downconversion process. The process describes the mechanism which is created quasiparticle and the principal losses of the energy in the system. This loss in energy in the downconversion process is counting by the efficiency η which has a constant value reported as 0.57. The origin of this value comes from a Monte Carlo simulation with parameters selected to match pure niobium, rather than our TiN mix.
The main objective of our work is the measurement of the efficiency of an MKID's resonators and how its value could be associated with the low values of resolution. The calibration was done in 2 MKIDs (A1, A2). One of this was covered with a silicon mask (A1) formed of holes (exposition of the inductor). Starting with the fundamental assumption, where the number of quasiparticles thermally generated and by photon absorption producing the same effect on the phase change of a resonator. The phase change of a resonator is calculated theoretically when a photon is absorbed. Having also assumed that the change of phase obtained in any given pixel is proportional to the square root of the number of incident photons (as governed by Poisson's statistics). Via this assumption, the gain of a resonator is obtained. By last, with the gain and the angle phase expect the efficiency of the system is calculated. The measurement of the efficiency in our devices shows a reduction of 98% (A2) and 99% (A1) respect to the simulation. In the same way, the characterization with the X-ray source shows a reduction of 99%.
