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We are developing micro-fabricated x-ray microcalorimeter arrays that show great promise for use in future x-ray spectroscopy missions. In each pixel we sense the magnetization change due to the heat input of an absorbed x-ray using a meander-shaped superconducting pickup trace that is on a substrate that is separate from the low noise 2-stage SQUID read-out. We report on the results from our prototype arrays that have achieved an energy resolution of 3.3 eV at 6 keV, and are progressing future arrays towards the goal of demonstrating sub-eV energy resolution. The results from studies of the thermalization of gold and gold-bismuth absorbers on sub-microsecond timescales will be presented. We will also present the results of comparisons of the magnetization and heat capacity of micro-fabricated devices to those of larger hand-constructed devices. [ABSTRACT FROM AUTHOR]

Metallic magnetic calorimeter (MMC) is one of the most promising x-ray detector technologies for providing the very high energy resolution needed for future astronomical x-ray imaging spectroscopy. For this purpose, we have developed micro-fabricated 5×5 arrays of MMC of which each individual pixel has excellent energy resolution as good as 3.4 eV at 6 keV x-ray. Here we report on the fabrication techniques developed to achieve good resolution and high efficiency. These include: processing of a thin insulation layer for strong magnetic coupling between the AuEr sensor film and the niobium pick-up coil; production of overhanging absorbers for enhanced efficiency of x-ray absorption; fabrication on SiN membranes to minimize the effects on energy resolution from athermal phonon loss. We have also improved the deposition of the magnetic sensor film such that the film magnetization is nearly completely that is expected from the AuEr sputter target bulk material. In addition, we have included a study of a positional sensitive design, the Hydra design, which allows thermal coupling of four absorbers to a common MMC sensor and circuit. [ABSTRACT FROM AUTHOR]

We are developing arrays of position-sensitive magnetic calorimeter (PoSM) X-ray detectors for future astronomy missions. The PoSM consists of multiple absorbers thermally coupled to one magnetic sensor. Each absorber element has a different thermal coupling to the sensor. This results in a distribution of different pulse shapes and enables position discrimination between the absorber elements. PoSMs are motivated by the desire to achieve the largest possible focal plane area with the fewest number of readout channels without compromising on spatial sampling. Optimizing the performance of PoSMs requires careful design of key parameters such as the thermal conductances between the absorbers, magnetic sensor and the heat sink, as well as the absorber heat capacities. We report on the first experimental results from four-absorber PoSMs, each absorber consisting of a two layer composite of bismuth and gold. The measured energy resolution (FWHM) was less than 5 eV for 6 keV X-rays into all four absorbers. Straightforward position discrimination by means of rise-time is also demonstrated. [ABSTRACT FROM AUTHOR]