Abstract
The Karlsruhe Tritium Neutrino (KATRIN) experiment is a large-scale effort to probe the absolute neutrino mass scale with a sensitivity of 0.2 eV (90% confidence level), via a precise measurement of the endpoint spectrum of tritium β-decay. This work documents several KATRIN commissioning milestones: the complete assembly of the experimental beamline, the successful transmission of electrons from three sources through the beamline to the primary detector, and tests of ion transport and retention. In the First Light commissioning campaign of autumn 2016, photoelectrons were generated at the rear wall and ions were created by a dedicated ion source attached to the rear section; in July 2017, gaseous 83mKr was injected into the KATRIN source section, and a condensed 83mKr source was deployed in the transport section. In this paper we describe the technical details of the apparatus and the configuration for each measurement, and give first results on source and system performance. We have successfully achieved transmission from all four sources, established system stability, and characterized many aspects of the apparatus.
Highlights
Twenty years ago, the definitive observation of neutrino flavor oscillation [1, 2] established that there are three distinct neutrino mass states ν1, ν2, ν3, each a coherent superposition of the neutrino flavor states νe, νμ, ντ
If the blocking potential is located in the center of the downstream pre-spectrometer magnet, blocked endpoint electrons have pitch angles greater than 85.8°. β-electrons with such large pitch angles are already excluded from the Karlsruhe Tritium Neutrino (KATRIN) acceptance via magnetic reflection, so this possible blocking potential will have no influence on the neutrino-mass measurements
There was no pumping in the Windowless Gaseous Tritium Source (WGTS) or Differential Pumping Section (DPS), so we investigated how the 83mKr decays were distributed between these sections
Summary
The definitive observation of neutrino flavor oscillation [1, 2] established that there are three distinct neutrino mass states ν1, ν2, ν3, each a coherent superposition of the neutrino flavor states νe, νμ, ντ. We successfully demonstrated the use of this source for the first time in the condensed 83mKr campaign (section 5), immediately following the measurements with gaseous 83mKr. The condensed 83mKr source illuminates a small region of the detector (section 5.1) with a high enough intensity to permit even the line scans of relatively weak conversion lines (section 5.2), and its stability (section 5.3) has been established. The condensed 83mKr source illuminates a small region of the detector (section 5.1) with a high enough intensity to permit even the line scans of relatively weak conversion lines (section 5.2), and its stability (section 5.3) has been established In these three measurement campaigns, we have established and studied electron and ion transport through the entire KATRIN beamline; commissioned and characterized both sources and detectors; and tested our data-taking and analysis methods in preparation for neutrino-mass measurements with tritium
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