The Design and Characterization of Dielectric Microcalorimeters for X-ray Photon Detection

The dielectric micro calorimeter (DMC) is a novel radiation detector utilizing a GHz resonator with dielectric thermometer (Sekiya et al. in J Low Temp Phys 167:435, 2012). The advantage of using a DMC is that the detection mechanism is based on a phonon mediation without Johnson noise and quasi-particle decay process. A large format array of DMCs can be easily multiplexed by a resonator circuit in the readout at GHz band width. We describe the design of a DMC as an X-ray photon counter. It is optimized to detect photon at 5.9 keV energy. We consider ¹⁸O-doped SrTiO₃ (STO18) and Nb-doped KTa_{( 1 - x )}Nb_xO₃ (KTN) as a candidate of dielectric thermometer. Dielectric materials which have sensitivity α(= dlog C_el/ dlog T) are also ideal for our application. We check that both STO18 and KTN have α∼ 10 ³ at 100 mK. If we assume a DMC resonator operating at 100 mK, we need a Q value of a resonator to be 2000 for X-ray detection.