Development of a beta spectrometry setup using metallic magnetic calorimeters

The precise knowledge of beta spectrum shapes is relevant in radionuclide metrology, e.g. when determining the activity of samples containing beta emitting isotopes, as well as in fundamental research or applications such as nuclear medicine. We present a newly developed beta spectrometer that utilizes Metallic Magnetic Calorimeters (MMCs) which have 4 pi absorbers and operates at temperatures < 100 mK. Microfabricated MMC detectors designed for five beta energy intervals enable the measurement of beta spectra with endpoint energies E-max ranging from a few tens of keV up to approximate to 1 MeV. The different detector types are read out by Superconducting QUantum Interference Device (SQUID) current sensors with compatible input inductances. In particular, we discuss the MMC detector design, absorber/source preparation, data acquisition and handling of the relatively large measurement data sets. The realized setup allows for high resolution beta spectrometry, which was shown via a test measurement of Tc-99 (E-max = 293.8 keV) using an external photon-emitting Am-241 calibration source.