Eur. Phys. J. C (2019) 79: 807
https://doi.org/10.1140/epjc/s10052-019-7320-4

Regular Article - Experimental Physics

Gamma-induced background in the KATRIN main spectrometer

¹ Technische Universität München, James-Franck-Str. 1, 85748, Garching, Germany
² IRFU, CEA, Université Paris-Saclay, 91191, Gif-sur-Yvette, France
³ Helmholtz-Institut für Strahlen- und Kernphysik, Rheinische Friedrich-Wilhelms Universität Bonn, Nussallee 14-16, 53115, Bonn, Germany
⁴ Karlsruhe Institute of Technology (KIT), Institute of Experimental Particle Physics (ETP), Wolfgang-Gaede-Str. 1, 76131, Karlsruhe, Germany
⁵ Institut für Physik, Johannes-Gutenberg-Universität Mainz, 55099, Mainz, Germany
⁶ Karlsruhe Institute of Technology (KIT), Institute for Data Processing and Electronics (IPE), Postfach 3640, 76021, Karlsruhe, Germany
⁷ Karlsruhe Institute of Technology (KIT), Institute for Nuclear Physics (IKP), Postfach 3640, 76021, Karlsruhe, Germany
⁸ Institut für Kernphysik, Westfälische Wilhelms-Universität Münster, Wilhelm-Klemm-Str. 9, 48149, Münster, Germany
⁹ Institute for Nuclear Research of Russian Academy of Sciences, 60th October Anniversary Prospect 7a, 117312, Moscow, Russia
¹⁰ Karlsruhe Institute of Technology (KIT), Institute for Technical Physics (ITeP), Postfach 3640, 76021, Karlsruhe, Germany
¹¹ Max-Planck-Institut für Kernphysik, Saupfercheckweg 1, 69117, Heidelberg, Germany
¹² Max-Planck-Institut für Physik, Föhringer Ring 6, 80805, Munich, Germany
¹³ Laboratory for Nuclear Science, Massachusetts Institute of Technology, 77 Massachusetts Ave, Cambridge, MA, 02139, USA
¹⁴ Center for Experimental Nuclear Physics and Astrophysics, and Dept. of Physics, University of Washington, Seattle, WA, 98195, USA
¹⁵ Nuclear Physics Institute of the CAS, v. v. i., CZ-250 68, Řež, Czech Republic
¹⁶ Department of Physics, Faculty of Mathematics und Natural Sciences, University of Wuppertal, Gauss-Str. 20, 42119, Wuppertal, Germany
¹⁷ Department of Physics, Carnegie Mellon University, Pittsburgh, PA, 15213, USA
¹⁸ Universidad Complutense de Madrid, Instituto Pluridisciplinar, Paseo Juan XXIII, no 1, 28040, Madrid, Spain
¹⁹ Department of Physics and Astronomy, University of North Carolina, Chapel Hill, NC, 27599, USA
²⁰ Triangle Universities Nuclear Laboratory, Durham, NC, 27708, USA
²¹ Institute for Nuclear and Particle Astrophysics and Nuclear Science Division, Lawrence Berkeley National Laboratory, Berkeley, CA, 94720, USA
²² University of Applied Sciences (HFD) Fulda, Leipziger Str. 123, 36037, Fulda, Germany
²³ Department of Physics, Case Western Reserve University, Cleveland, OH, 44106, USA
²⁴ Institut für Physik, Humboldt-Universität zu Berlin, Newtonstr. 15, 12489, Berlin, Germany
²⁵ Karlsruhe Institute of Technology (KIT), Project, Process, and Quality Management (PPQ), Postfach 3640, 76021, Karlsruhe, Germany
²⁶ Oak Ridge National Laboratory, Oak Ridge, TN, 37831, USA

^* e-mail: lkippenb@uw.edu

Received: 5 March 2019
Accepted: 19 September 2019
Published online: 28 September 2019

Abstract

The KATRIN experiment aims to measure the effective electron antineutrino mass with a sensitivity of using a gaseous tritium source combined with the MAC-E filter technique. A low background rate is crucial to achieving the proposed sensitivity, and dedicated measurements have been performed to study possible sources of background electrons. In this work, we test the hypothesis that gamma radiation from external radioactive sources significantly increases the rate of background events created in the main spectrometer (MS) and observed in the focal-plane detector. Using detailed simulations of the gamma flux in the experimental hall, combined with a series of experimental tests that artificially increased or decreased the local gamma flux to the MS, we set an upper limit of  (90% C.L.) from this mechanism. Our results indicate the effectiveness of the electrostatic and magnetic shielding used to block secondary electrons emitted from the inner surface of the MS.