Measurement and reduction of low-level radon background in the KATRIN experiment

Journal Article · Thu Aug 08 00:00:00 EDT 2013 · AIP Conference Proceedings

DOI:https://doi.org/10.1063/1.4818087· OSTI ID:22218163

Fränkle, F. M. ^[1]

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1. F.M. Fränkle Department of Physics and Astronomy, University of North Carolina, Chapel Hill, NC (United States)

The KArlsruhe TRItium Neutrino (KATRIN) experiment is a next generation, model independent, large scale experiment to determine the mass of the electron anti-neutrino by investigating the kinematics of tritium beta decay with a sensitivity of 200 meV/c{sup 2}. The measurement setup consists of a high luminosity windowless gaseous molecular tritium source (WGTS), a differential and cryogenic pumped electron transport and tritium retention section, a tandem spectrometer section (pre-spectrometer and main spectrometer) for energy analysis, followed by a detector system for counting transmitted beta decay electrons. Measurements performed at the KATRIN pre-spectrometer test setup showed that the decay of radon (Rn) atoms in the volume of the KATRIN spectrometers is a major background source. Rn atoms from low-level radon emanation of materials inside the vacuum region of the KATRIN spectrometers are able to penetrate deep into the magnetic flux tube so that the alpha decay of Rn contributes to the background. Of particular importance are electrons emitted in processes accompanying the Rn alpha decay, such as shake-off, internal conversion of excited levels in the Rn daughter atoms and Auger electrons. Lowenergy electrons (< 100 eV) directly contribute to the background in the signal region. High-energy electrons can be stored magnetically inside the volume of the spectrometer and are able to create thousands of secondary electrons via subsequent ionization processes with residual gas molecules. In order to reduce the Rn induced background different active and passive counter measures were developed and tested. This proceeding will give an overview on Rn sources within the KATRIN spectrometer, describes how Rn decays inside the spectrometer produce background events at the detector and presents different counter measures to reduce the Rn induced background.

• OSTI ID: 22218163
• Journal Information: AIP Conference Proceedings, Vol. 1549, Issue 1; Conference: LRT 2013: 4. international workshop on low radioactivity techniques, Assergi (Italy), 10-12 Apr 2013; Other Information: (c) 2013 AIP Publishing LLC; Country of input: International Atomic Energy Agency (IAEA); ISSN 0094-243X
• Country of Publication: United States
• Language: English

Related Subjects

73 NUCLEAR PHYSICS AND RADIATION PHYSICS
46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND TECHNOLOGY
ALPHA DECAY
BETA DECAY
CHARGED PARTICLE DETECTION
CRYOGENICS
ELECTRONS
EXCITED STATES
INTERNAL CONVERSION
MAGNETIC FLUX
MAGNETIC SPECTROMETERS
MEV RANGE
NEUTRINO DETECTION
NEUTRINOS
RADON
SENSITIVITY
TANDEM ELECTROSTATIC ACCELERATORS
TRANSPORT THEORY
TRITIUM