Small Size Transition-Edge Sensors for Future X-Ray Applications

Abstract

Large arrays of transition edge sensors (TESs) are the baseline for a number of future space observatories. For instance, the X-ray integral field unit (X-IFU) instrument on board the ATHENA space telescope will consist of $$\sim$$ ∼ 3000 TESs with high energy resolution ($$2\,{\mathrm{eV}}$$ 2 eV at X-ray energies up to 7 keV). In this contribution we report on the development of an X-ray TES array as a backup detector technology for X-IFU. The baseline readout technology for this mission is time domain multiplexing where the detectors are DC biased. Specifically, we report on the characterization of four different Ti/Au TESs with the following dimensions ($$\hbox {L}\times \hbox {W}$$ L × W ): $$30\times 15$$ 30 × 15 , $$30\times 30$$ 30 × 30 , $$50\times 25$$ 50 × 25 and $$50\times 50\,\mu \hbox {m}^2$$ 50 × 50 μ m 2 , all of which are coupled to a $$2.3\,\mu \hbox {m}$$ 2.3 μ m thick Au absorber of area $$240\times 240\,\mu \hbox {m}^2$$ 240 × 240 μ m 2 . We have performed our characterization using our standard frequency domain multiplexing readout connecting only pixels at low frequencies, where nonlinear effects due to the AC biasing are negligible. Promising energy resolution has been obtained, for instance $$1.78\pm 0.10\,\hbox {eV}$$ 1.78 ± 0.10 eV and $$1.75\pm 0.10\,\hbox {eV}$$ 1.75 ± 0.10 eV at 5.9 keV for the $$50\times 25$$ 50 × 25 and $$50\times 50\,\mu \hbox {m}^2$$ 50 × 50 μ m 2 detectors respectively. Uniformity over a kilo-pixel array (of detectors with the same geometry) has been also studied, confirming the high quality of our fabrication process.

Performance of the SRON Ti/Au transition edge sensor x-ray calorimeters

“…The energy resolution for the 50×25 µm 2 is slightly worse than that of the higher resistance devices. This originates from the mismatch between these low resistance devices and the AC-biased FDM readout [17,36], as well as a too small ratio between the effective shunt resistance and the TES resistance in the bias point, reducing the stiffness of the voltage bias. This degradation is therefore not related to the properties of the detector.…”

“…At SRON, we have historically focused on the development of TES detectors intended for FDM which favors detectors with a high resistance ( 100 mΩ) [15,16]. However, due to the recent decision to use TDM in the X-IFU instrument, we have also started to develop detector more suitable for TDM which performs better using low resistance devices [17].…”