The KArlsruhe TRItium Neutrino experiment (KATRIN) aims to measure the effective electron anti-neutrino mass with an unprecedented sensitivity of 0.2eV/c2, using β-electrons from tritium decay. The ...electrons are guided magnetically by a system of superconducting magnets through a vacuum beamline from the windowless gaseous tritium source through differential and cryogenic pumping sections to a high resolution spectrometer and a segmented silicon pin detector. At the same time tritium gas has to be prevented from entering the spectrometer. Therefore, the pumping sections have to reduce the tritium flow by more than 14 orders of magnitude. This paper describes the measurement of the reduction factor of the differential pumping section performed with high purity tritium gas during the first measurement campaigns of the KATRIN experiment. The reduction factor results are compared with previously performed simulations, as well as the stringent requirements of the KATRIN experiment.
•Measurement of tritium gas flow reduction in differential pumping in KATRIN.•Reduction of gas flow by more than 7 orders of magnitude.•Excellent agreement between measurement and simulations.•Regeneration interval of KATRIN cryogenic pump longer than 60 days possible.
The KArlsruhe TRItium Neutrino (KATRIN) experiment aims to determine the effective anti-electron neutrino mass with a sensitivity of 0.2eV/c2 by using the kinematics of tritium β-decay. It is crucial ...to have a high signal rate which is achieved by a windowless gaseous tritium source producing 1011β-electrons per second. These are guided adiabatically to the spectrometer section where their energy is analyzed. In order to maintain a low background rate below 0.01cps, one essential criteria is to permanently reduce the flow of neutral tritium molecules between the source and the spectrometer section by at least 14 orders of magnitude. A differential pumping section downstream from the source reduces the tritium flow by seven orders of magnitude, while at least another factor of 107 is achieved by the cryogenic pumping section where tritium molecules are adsorbed on an approximately 3K cold argon frost layer. In this paper, the results of the cryogenic pumping section commissioning measurements using deuterium are discussed. The cryogenic pumping section surpasses the requirement for the flow reduction of 107 by more than one order of magnitude. These results verify the predictions of previously published simulations.
•Measurement of the reduction factor of KATRIN’s cryogenic pumping section with deuterium.•Safe tritium retention can be concluded.•More than 108 gas flow reduction.
In this work we present a keV-scale sterile-neutrino search with a low-tritium-activity data set of the KATRIN experiment, acquired in a commissioning run in 2018. KATRIN performs a spectroscopic ...measurement of the tritium
β
-decay spectrum with the main goal of directly determining the effective electron anti-neutrino mass. During this commissioning phase a lower tritium activity facilitated the measurement of a wider part of the tritium spectrum and thus the search for sterile neutrinos with a mass of up to
1.6
keV
. We do not find a signal and set an exclusion limit on the sterile-to-active mixing amplitude of
sin
2
θ
<
5
×
10
-
4
(
95
%
C.L.) at a mass of 0.3 keV. This result improves current laboratory-based bounds in the sterile-neutrino mass range between 0.1 and 1.0 keV.
The KArlsruhe TRItium Neutrino experiment (KATRIN) aims to measure the effective electron anti-neutrino mass with an unprecedented sensitivity of 0.2 eV/c2, using β-electrons from tritium decay. ...Superconducting magnets will guide the electrons through a vacuum beamline from the windowless gaseous tritium source through differential and cryogenic pumping sections to a high resolution spectrometer. At the same time tritium gas has to be prevented from entering the spectrometer. Therefore, the pumping sections have to reduce the tritium flow by at least 14 orders of magnitude. This paper describes various simulation methods in the molecular flow regime used to determine the expected gas flow reduction in the pumping sections for deuterium (commissioning runs) and for radioactive tritium. Simulations with MolFlow+ and with an analytical model are compared with each other, and with the stringent requirements of the KATRIN experiment.
•Simulation of the gas flow of D2 and T2 in differential and the cryogenic pumping in the KATRIN experiment.•The total gas flow is reduced by more than 14 orders of magnitude with the combined pumping systems.•Tritium migration along the beam line due to the sojourn time on Ar-frost and β-induced desorption are investigated.•Two simulation methods are compared; TPMC simulation with MolFlow+, and a custom-made C++ code.
The KATRIN experiment aims to measure the effective electron antineutrino mass
m
ν
¯
e
with a sensitivity of
0.2
eV
/
c
2
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
0.006
count
/
s
(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.
The KATRIN experiment aims to determine the effective electron neutrino mass with a sensitivity of
0.2
eV/c
2
(%90 CL) by precision measurement of the shape of the tritium
β
-spectrum in the endpoint ...region. The energy analysis of the decay electrons is achieved by a MAC-E filter spectrometer. A common background source in this setup is the decay of short-lived isotopes, such as
219
Rn
and
220
Rn
, in the spectrometer volume. Active and passive countermeasures have been implemented and tested at the KATRIN main spectrometer. One of these is the magnetic pulse method, which employs the existing air coil system to reduce the magnetic guiding field in the spectrometer on a short timescale in order to remove low- and high-energy stored electrons. Here we describe the working principle of this method and present results from commissioning measurements at the main spectrometer. Simulations with the particle-tracking software
Kassiopeia
were carried out to gain a detailed understanding of the electron storage conditions and removal processes.
The neutrino mass experiment KATRIN requires a stability of 3 ppm for the retarding potential at − 18.6 kV of the main spectrometer. To monitor the stability, two custom-made ultra-precise ...high-voltage dividers were developed and built in cooperation with the German national metrology institute Physikalisch-Technische Bundesanstalt (PTB). Until now, regular absolute calibration of the voltage dividers required bringing the equipment to the specialised metrology laboratory. Here we present a new method based on measuring the energy difference of two 83mKr conversion electron lines with the KATRIN setup, which was demonstrated during KATRIN’s commissioning measurements in July 2017. The measured scale factor M=1972.449(10) of the high-voltage divider K35 is in agreement with the last PTB calibration 4 years ago. This result demonstrates the utility of the calibration method, as well as the long-term stability of the voltage divider.
Abstract The neutrino mass experiment KATRIN requires a stability of 3 ppm for the retarding potential at − 18.6 kV of the main spectrometer. To monitor the stability, two custom-made ultra-precise ...high-voltage dividers were developed and built in cooperation with the German national metrology institute Physikalisch-Technische Bundesanstalt (PTB). Until now, regular absolute calibration of the voltage dividers required bringing the equipment to the specialised metrology laboratory. Here we present a new method based on measuring the energy difference of two $$^{83{\mathrm{m}}}$$ 83m Kr conversion electron lines with the KATRIN setup, which was demonstrated during KATRIN’s commissioning measurements in July 2017. The measured scale factor $$M=1972.449(10)$$ M=1972.449(10) of the high-voltage divider K35 is in agreement with the last PTB calibration 4 years ago. This result demonstrates the utility of the calibration method, as well as the long-term stability of the voltage divider.
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