The precision of existing decay data of radionuclides for activity determination is often a limitation for actual applications in science, society and industry. For this reason, the EMPIR project PrimA-LTD aims to introduce an advanced primary activity standardization technique that is based on magnetic microcalorimeters (MMCs) and that will offer very low energy threshold of few eV and a decay scheme-independent detection efficiency close to 100 %. As a proof of concept, we developed two MMC-based detector types in order to standardize an -decaying, a -decaying and an electron capture decaying isotope. One detector type aims to introduce a reusable detector setup, while the other aims to provide highly accurate decay spectra by high-resolution measurements with high statistics. We present the designs, fabrication status and first characterization measurements of both detectors types and outline next steps
