Study of the Influence of the Source Quality on the Determination of the Shape Factor of Beta Spectra

We are developing metallic magnetic calorimeters for beta spectrometry with the aim of determining the shape factors of beta spectra. The beta emitter is enclosed inside the detector absorber and the absorber size is chosen such that the detection efficiency is close to 100% for the entire spectrum. The nature of the deposit of the beta emitter is critical for precise measurement. A dependence of the shape of the spectrum on the quality of the source has been observed, supposedly due to interactions between the electrons and the deposit itself. We chose for this comparative study a nuclide with an allowed transition whose theoretical spectrum is relatively well-known, ⁶³Ni, a pure beta emitter with an endpoint energy of 66.98?keV. Results of measurements of ⁶³Ni deposited with different techniques are presented and compared to each other and to the theoretical spectrum.