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TT: Fachverband Tiefe Temperaturen

TT 82: Cryogenic Detectors and Sensors

TT 82.3: Vortrag

Donnerstag, 12. März 2026, 15:30–15:45, HSZ/0103

High resolution measurement of the ⁶⁵Zn spectrum with magnetic microcalorimeters (MMCs) — •Michael Paulsen¹, Philipp Ranitzsch^2,3, Jörn Beyer¹, Alexander Göggelmann², Sebastian Kempf^4,5, Karsten Kossert², Ole Nähle², Constantin Schuster^1,2, Mariia Sidorova^1,2, and Mathias Wegner^5,4 — ¹Physikalisch-Technische Bundesanstalt (PTB) Berlin — ²PTB Braunschweig — ³DLR e.V., Hamburg — ⁴IMS, Karlsruhe Institute of Technology (KIT) — ⁵IPE, KIT

MMCs have proven to be among the best spectrometers for beta transitions and electron capturing (EC) radionuclides. To achieve a high energy resolution, the sensor and absorber heat capacities are kept as low as possible. Thus, the absorber dimensions are very small, yet simultaneously large enough to ensure that a sufficient detection efficiency is achieved. This is challenging when studying EC radionuclides, such as ⁶⁵Zn since the emission energies range from 0 to over 1 MeV for high-intensity gamma rays. We present a high-resolution spectrum of ⁶⁵Zn featuring K, L and M peaks below 10 keV. For the β⁺ branch (E_max = 329.9 keV), additional complications arise. Each emitted positron typically annihilates with an electron in the absorber and generates gamma rays with a combined energy of 1022 keV. These additional events cannot be time resolved by the detector due to the very short lifetimes of the positrons (∼ 100 ps). This yields a distorted beta spectrum with a substantial number of counts above E_max. We consider how this relates to the issue of detector efficiency and how to unfold such spectra using Monte-Carlo based simulation methods.

Keywords: Cryogenic particle detector; Magnetic microcalorimeter; Radionuclide metrology