219 research outputs found
Modeling of electron emission processes accompanying Radon--decays within electrostatic spectrometers
Electrostatic spectrometers utilized in high-resolution beta-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 Rn-219 or Rn-220 atoms being
emanated into the volume and undergoing alpha-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 Po-215 and Po-216 daughters. The model yields electron
energy spectra up to 400 keV and electron multiplicities of up to 20 which are
compared to experimental data.Comment: 7 figure
Modelling of gas dynamical properties of the KATRIN tritium source and implications for the neutrino mass measurement
The KATRIN experiment aims to measure the effective mass of the electron
antineutrino from the analysis of electron spectra stemming from the beta-decay
of molecular tritium with a sensitivity of 200 meV. Therefore, a daily
throughput of about 40 g of gaseous tritium is circulated in a windowless
source section. An accurate description of the gas flow through this section is
of fundamental importance for the neutrino mass measurement as it significantly
influences the generation and transport of beta-decay electrons through the
experimental setup. In this paper we present a comprehensive model consisting
of calculations of rarefied gas flow through the different components of the
source section ranging from viscous to free molecular flow. By connecting these
simulations with a number of experimentally determined operational parameters
the gas model can be refreshed regularly according to the measured operating
conditions. In this work, measurement and modelling uncertainties are
quantified with regard to their implications for the neutrino mass measurement.
We find that the systematic uncertainties related to the description of gas
flow are represented by eV,
and that the gas model is ready to be used in the analysis of upcoming KATRIN
data.Comment: 28 pages, 13 figure
Validation of a model for Radon-induced background processes in electrostatic spectrometers
The Karlsruhe Tritium Neutrino (KATRIN) experiment investigating tritium
beta-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 alpha-decay of Rn-219 and Rn-220 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.Comment: 10 figure
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