maXs: Microcalorimeter Arrays for High-Resolution X-Ray Spectroscopy at GSI/FAIR

Abstract

Highly-charged heavy ions like U 91+ provide unique conditions for the investigation of relativistic and quantum electrodynamical effects in strong electromagnetic fields. We present two X-ray detectors developed for high-resolution spectroscopy on highly-charged heavy ions. Both detectors consist of metallic magnetic calorimeters (MMCs) forming linear eight-pixel arrays. The first detector, maXs-20, is developed for the detection of X-rays up to 20 keV with an energy resolution below 3 eV. The second device, maXs-200, is designed for X-ray energies up to 200 keV with an energy resolution of 40 eV. The results of characterization measurements of single detectors of both arrays will be shown and discussed. In both cases, the performance of the detectors agrees well with their design values. Furthermore, we present a prototype MMC for soft X-rays with improved magnetic flux coupling. In first characterization measurements the energy resolution of this device was 2.0 eV (FWHM) for X-rays up to 6 keV.

The electron capture in 163Ho experiment – ECHo

“…As discussed in more detail in Section 4, the detectors that are used for the ECHo experiment, metallic magnetic calorimeters (MMCs) [47,48], have already demonstrated an intrinsic rise time shorter than 100 ns at 30 mK [49]. This makes MMCs today by far the fastest microcalorimeter technology available at temperatures below 100 mK and therefore these constitute the best possible choice for the ECHo experiment in this respect.…”

“…Figure 7 shows the two geometries which presently are most commonly used, the so called meander-shape geometry and the sandwich geometry. Both of these design are based on planar temperature sensor to make possible the microfabrication of large and dense-packed arrays [49]. Scheme (a) is based on two planar meander-shaped pickup-coils, each having inductance L connected in parallel to the input coil of the front-end SQUID, with inductance L i .…”

“…This unwanted effect can be reduced by minimizing the contact area between the gold absorber and the Au:Er sensor. Such a MMC detector design has been successfully developed and it was used to prepare a 1×16 array based on the maXs-20 sandwich design [49] for a second 163 Ho ion-implantation (MMC-ECHo-1). The implantation onto the MMC-ECHo-1 detector array was performed at ISOLDE-CERN in an off-line process using a chemically purified 163 Ho source.…”

Development of MMC Gamma Detectors for Nuclear Analysis

“…In order to demonstrate the feasibility of the Pu measurement with an MMC we installed an 241 Am source in front of a Heidelberg maXs-200 MMC in a 18 mK dilution fridge operated at the Kirchhoff Institute for Physics 7 . This design uses a Au:Er sensor deposited on top of a 0.5 mm x 2 mm meander of Nb, which is used to both apply the field and readout the signal.…”

“…This performance shows that it should be possible to directly measure the 242 Pu line using this device even in sub-optimal operating conditions. Under optimal conditions this device has been shown to achieve an energy resolution of 60 eV FWHM at 60 keV 7 . We are currently working on attaining similar resolution.…”