<title>High-resolution gamma-ray spectrometers using bulk absorbers coupled to Mo/Cu multilayer superconducting transition-edge sensors</title>

Abstract

In x-ray and gamma-ray spectroscopy, it is desirable to have detectors with high energy resolution and high absorption efficiency. At LLNL, we have developed superconducting tunnel junction-based single photon x-ray detectors with thin film absorbers that have achieved these goals for photon energies up to 1 keV. However, for energies above 1 keV, the absorption efficiency of these thin-film detectors decreases drasti:a fly. We are developing the use of high-purity superconducting bulk materiats as microcatorimetcr absorbers for high-energy x-rays and gamma rays. The increase in absorber temperature due to incident photons is sensed by a superconducting tramition-edge sensor (TES) composed of a MoICU multilayer lti" film. Filmr of MO and Cu are mutuafty insoluble and therefore very stable and can be annealed. The multilayer stmcture allows scaling in thickness to optimize heat capacity and normal state resistance. We measured an energy resolution of 70 eV for 60 keV incident gamma-rays with a 1 x I x 0.25 mm3 Sn absorber. We present x-ray and ganum-my results from this detector design with a Sn absorber. We also propose tie use of an active negative feedback vottage bias to improve tbe per fonmmce of our detector and show prelimimry res"ks.

Review of superconducting transition-edge sensors for x-ray and gamma-ray spectroscopy

“…The need for useful detection efficiencies has catalyzed the development of two-body sensors in which a bulk absorber is attached to a much smaller thermometer. For gamma-ray detection, early success was achieved with semiconducting thermistors and superconducting tin absorbers [15] and tin absorbers subsequently worked well with TES thermometers [152]. The degradation of calorimeter energy resolution with increased heat capacity has so far limited the area of individual calorimeters designed for the 40-200 keV range to a few mm 2 .…”

IXO TES Microcalorimeters: from Focal Plane instruments to Anticoincidence Detectors

“…Enabling simultaneous observations of high resolution line emission in the keV range with correlated features in the hard X-ray range is an important scientific opportunity. TES-based single pixel and small array detectors working at 60-100 keV have been already produced [16,17]. In our case, a solution with a minimum impact (n. of pixels, complexity of the design) on the system is in order.…”

Gamma-ray spectrometers using superconducting transition edge sensors with external active feedback bias

“…A TES is a supaconducting film with a very narrow transition between zero resistance md normat resistance s.cb that small changes in temperature cause kuge changes in resistance. A silicm nitride (SiN) membrane substrate sewes as the weak thenm.1 link to the cold bath with typical thernd conductivity Grti -0.25 nW/K at a bath temperamre of 70 mK [8]. The bulk Sn is strongly coupled m the TES GOI a small amount of Stycast epoxy.…”

“…Knowledge of the superconducting transition [8] allows us to infer the change in temperature of the TES in both modes ( fig. 3).…”