Abstract
The KArlsruhe TRItium Neutrino experiment (KATRIN) aims to determine the effective electron (anti)-neutrino mass with a sensitivity of 0.2eV/c^2 by precisely measuring the endpoint region of the tritium beta -decay spectrum. It uses a tandem of electrostatic spectrometers working as magnetic adiabatic collimation combined with an electrostatic (MAC-E) filters. In the space between the pre-spectrometer and the main spectrometer, creating a Penning trap is unavoidable when the superconducting magnet between the two spectrometers, biased at their respective nominal potentials, is energized. The electrons accumulated in this trap can lead to discharges, which create additional background electrons and endanger the spectrometer and detector section downstream. To counteract this problem, “electron catchers” were installed in the beamline inside the magnet bore between the two spectrometers. These catchers can be moved across the magnetic-flux tube and intercept on a sub-ms time scale the stored electrons along their magnetron motion paths. In this paper, we report on the design and the successful commissioning of the electron catchers and present results on their efficiency in reducing the experimental background.
Highlights
The KArlsruhe TRItium Neutrino experiment (KATRIN) [1] at the Karlsruhe Institute of Technology is aiming to determine the average electronneutrino mass with a sensitivity of 0.2eV/c2 (90% CL) [2] in a direct, model-independent way using a precision measurement of the tritium β-decay spectrum near the endpoint
The former upper limit of m(νe) 2eV/c2 on direct mass measurements have been set by the Mainz [3] and Troitsk [4,5] which has been recently improved by the KATRIN experiment by almost a factor of two: m(νe) < 1.1eV/c2 [6]
In the center of the main spectrometer, the magnetic field can be fine-tuned by a low-field correction system (LFCS) consisting of vertical air coils surrounding the main spectrometer vessel, and by additional horizontal coils to compensate the Earth magnetic field (EMCS) [9]. β-electrons enter a spectrometer from the source side and follow the magnetic field lines in cyclotron motion into the spectrometer
Summary
The KArlsruhe TRItium Neutrino experiment (KATRIN) [1] at the Karlsruhe Institute of Technology is aiming to determine the average electron (anti)neutrino mass with a sensitivity of 0.2eV/c2 (90% CL) [2] in a direct, model-independent way using a precision measurement of the tritium β-decay spectrum near the endpoint. The observable in this case is an incoherent sum over the mass eigenstates contributing to the electron (anti)neutrino νe, given by m2(νe) = |Uei |2m2(νi ),. Its retarding potential is scanned around the endpoint energy within a range between about − 18.5 kV and − 18.6kV
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