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T: Fachverband Teilchenphysik

T 18: Neutrino physics without accelerators I

T 18.3: Vortrag

Montag, 15. März 2021, 16:35–16:50, Tr

Absolute energy scale of the KATRIN experiment — •Manuel Klein and Rudolf Sack for the KATRIN collaboration — Karlsruhe Institute of Technology (KIT), IAP, Hermann-von-Helmholtz-Platz 1, 76344 Eggenstein-Leopoldshafen

The KArlsruhe TRItium Neutrino (KATRIN) experiment performs a model-independent measurement of the electron neutrino mass. It is designed for a neutrino mass sensitivity of 0.2 eV (90% CL) after three full years of measurement time. KATRIN measures near the endpoint of the tritium beta-decay spectrum with a MAC-E filter, which relies on Magnetic Adiabatic Collimation of the beta electrons and an Electrostatic retarding potential: at the main spectrometer, the high voltage of about −18.6 kV is monitored with a precision of 2 ppm, and in the the tritium source, the electron start potential is provided by a weakly-ionised plasma created from the self-ionising source gas.

For the neutrino mass analysis, the endpoint is fitted from the high voltage of the main spectrometer as one of four free parameters. Nevertheless, the absolute energy scale is also relevant: a) in order to compare with the Q value of tritium, which serves as a precision benchmark for the retardation energy scale and b) because any time-dependence of the energy scale induces a broadening of the measured spectrum, which has to be considered in the analysis. A key aspect here is the effective electron start potential in the strongly-magnetised source plasma. This contribution shows that the systematic effect from drifts of the energy scale is not negligible but well within the uncertainty budget.

Supported by BMBF (Ø05A17VK2) and the Helmholtz Association.