Improvement of Contact-Less KID Design Using Multilayered Al/Ti Material for Resonator

The necessity to increase exposure in rare event search experiments by maintaining a low energy threshold and a good energy resolution leads to segmented detectors as in EDELWEISS (Dark Matter), CUORE (0 νββ ) or Ricochet (CENNS) for example. However, the large number of sub-elements can dramatically increase the complexity of such detector arrays. In this work we report on our progress towards designing a flexible detector technology based on Kinetic Inductance Detector (KID) resonators evaporated on massive target crystals readout by a contact-less feedline. Providing that we achieve 𝒪(100) eV energy threshold, such approach could easily be scaled to tens of kilogram detector arrays thanks to the intrinsic multiplexing capability of KIDs. Using a 30 g silicon target absorber with Al/Ti multi layers for the KID resonator, we report a significant improvement of our detector response exhibiting a keV-scale energy resolution combined with the absence of position dependence on the event location. Indeed, compared to our previous work, we are now able to properly identify calibration lines from surface (20 keV X-rays) and bulk events (60 keV gamma rays). This significant improvement is an important step towards a better understanding of phonons and quasiparticles dynamics, which is pivotal in optimizing this technology.