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Bonn J.,Johannes Gutenberg University Mainz | Eitel K.,Karlsruhe Institute of Technology | Gluck F.,Karlsruhe Institute of Technology | Gluck F.,Research Institute for Nuclear and Particle Physics | And 4 more authors.
Physics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics | Year: 2011

The aim of the KArlsruhe TRItium Neutrino experiment KATRIN is the determination of the absolute neutrino mass scale down to 0.2 eV, with essentially smaller model dependence than from cosmology and neutrinoless double beta decay. For this purpose, the integral electron energy spectrum is measured close to the endpoint of molecular tritium beta decay. The endpoint, together with the neutrino mass, should be fitted from the KATRIN data as a free parameter. The right-handed couplings change the electron energy spectrum close to the endpoint, therefore they have some effect also to the precise neutrino mass determination. The statistical calculations show that, using the endpoint as a free parameter, the unaccounted right-handed couplings constrained by many beta decay experiments can change the fitted neutrino mass value, relative to the true neutrino mass, by not larger than about 5-10%. Using, incorrectly, the endpoint as a fixed input parameter, the above change of the neutrino mass can be much larger, order of 100%, and for some cases it can happen that for large true neutrino mass value the fitted neutrino mass squared is negative. Publications using fixed endpoint and presenting large right-handed coupling effects to the neutrino mass determination are not relevant for the KATRIN experiment. © 2011 Elsevier B.V. Source


Mertens S.,Karlsruhe Institute of Technology | Drexlin G.,Karlsruhe Institute of Technology | Frankle F.M.,Karlsruhe Institute of Technology | Frankle F.M.,University of North Carolina at Chapel Hill | And 10 more authors.
Astroparticle Physics | Year: 2013

The KATRIN experiment is designed to measure the absolute neutrino mass scale with a sensitivity of 200 meV at 90% C.L. by high resolution tritium b-spectroscopy. A low background level of 10-2 counts per second (cps) at the b-decay endpoint is required in order to achieve the design sensitivity. In this paper we discuss a novel background source arising from magnetically trapped keV electrons in electrostatic retarding spectrometers. The main sources of these electrons are a-decays of the radon isotopes 219,220Rn as well as α-decays of tritium in the volume of the spectrometers. We characterize the expected background signal by extensive MC simulations and investigate the impact on the KATRIN neutrino mass sensitivity. From these results we refine design parameters for the spectrometer vacuum system and propose active background reduction methods to meet the stringent design limits for the overall background rate. © 2012 Elsevier B.V. All rights reserved. Source


Mertens S.,Karlsruhe Institute of Technology | Beglarian A.,Karlsruhe Institute of Technology | Bornschein L.,Karlsruhe Institute of Technology | Drexlin G.,Karlsruhe Institute of Technology | And 12 more authors.
Journal of Instrumentation | Year: 2012

The primary objective of the KATRIN experiment is to probe the absolute neutrino mass scale with a sensitivity of 200meV (90% C.L.) by precision spectroscopy of tritium b -decay. To achieve this, a low background of the order of 10-2 cps in the region of the tritium b -decay endpoint is required. Measurements with an electrostatic retarding spectrometer have revealed that electrons, arising from nuclear decays in the volume of the spectrometer, are stored over long time periods and thereby act as a major source of background exceeding this limit. In this paper we present a novel active background reduction method based on stochastic heating of stored electrons by the well-known process of electron cyclotron resonance (ECR). A successful proof-of-principle of the ECR technique was demonstrated in test measurements at the KATRIN pre-spectrometer, yielding a large reduction of the background rate. In addition, we have carried out extensive Monte Carlo simulations to reveal the potential of the ECR technique to remove all trapped electrons in a few ms with negligible loss of measurement time in the main spectrometer. This would allow the KATRIN experiment attaining its full physics potential. © 2012 IOP Publishing Ltd and Sissa Medialab srl. Source


Wandkowsky N.,Karlsruhe Institute of Technology | Drexlin G.,Karlsruhe Institute of Technology | Frankle F.M.,Karlsruhe Institute of Technology | Frankle F.M.,University of North Carolina at Chapel Hill | And 5 more authors.
Journal of Physics G: Nuclear and Particle Physics | Year: 2013

The Karlsruhe Tritium Neutrino (KATRIN) experiment investigating tritium β-decay close to the endpoint with unprecedented precision has stringent requirements on the background level of less than 10-2 counts per second. Electron emission during the α-decay of 219, 220Rn atoms in the electrostatic spectrometers of KATRIN is a serious source of background exceeding this limit. In this paper we compare extensive simulations of Rn-induced background to specific measurements with the KATRIN pre-spectrometer to fully characterize the observed Rn-background rates and signatures and determine generic Rn emanation rates from the pre-spectrometer bulk material and its vacuum components. © 2013 IOP Publishing Ltd. Source


Wandkowsky N.,Karlsruhe Institute of Technology | Drexlin G.,Karlsruhe Institute of Technology | Frankle F.M.,Karlsruhe Institute of Technology | Frankle F.M.,University of North Carolina at Chapel Hill | And 5 more authors.
New Journal of Physics | Year: 2013

Electrostatic spectrometers utilized in high-resolution β-spectroscopy studies such as in the Karlsruhe Tritium Neutrino (KATRIN) experiment have to operate with a background level of less than 10-2 counts per second. This limit can be exceeded by even a small number of 219,220Rn atoms being emanated into the volume and undergoing α-decay there. In this paper we present a detailed model of the underlying background-generating processes via electron emission by internal conversion, shake-off and relaxation processes in the atomic shells of the 215,216Po daughters. The model yields electron energy spectra up to 400 keV and electron multiplicities of up to 20 which are compared to experimental data. © IOP Publishing and Deutsche Physikalische Gesellschaft. Source

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