Development of Hard X-Ray and Gamma-Ray Spectrometer Using Superconducting Transition Edge Sensor

Superconducting transition edge sensors (TES) are used for high-resolution X-ray spectroscopy. In our group, we have developed Ir/Au-TESs. We have recently started to develop a high-resolution X-ray and gamma-ray spectrometer using our Ir/Au-TES. In this study, we plan to accelerate the response time of the detector system, thus we have designed a new Sn-absorber coupled TES detector system by improving the thermal contact between the TES and the absorber. A superconducting tin absorber is coupled to an Ir/Au superconducting film with a gold (Au) bump post, instead of an epoxy post, which is used conventionally. The pulse height signal, which we obtained from the Au bump post TES, is more than twice as large as that from the epoxy post system, and the slow component of the decay time constant improved to 8.0 ms from 22.0 ms. The energy resolution of the 59.5 keV photoelectron peak is 280 eV FWHM, which is currently dominated by the mechanical vibration of our pulse-tube refrigerator.