75 research outputs found
An active transverse energy filter to differentiate low energy particles with large pitch angles in a strong magnetic field
We present the idea and proof of principle measurements for an angular-selective active filter for charged particles. The motivation for the setup arises from the need to distinguish background electrons from signal electrons in a spectrometer of MAC-E filter type. While a large fraction of the background electrons exhibit predominantly small angles relative to the magnetic guiding field (corresponding to a low amount of kinetic energy in the motion component transverse to the field lines, in the following referred to as transverse energy) and pass the filter mostly unhindered, signal electrons from an isotropically emitting source interact with the active filter and are detected. The concept is demonstrated using a microchannel plate (MCP) as an active filter element. When correctly aligned with the magnetic field, electrons with a small transverse energy pass the channels of the MCP without interaction while electrons with large transverse energies hit the channel walls and trigger an avalanche of secondary electrons that is subsequently detected. Due to several drawbacks of MCPs for an actual transverse energy filter, an alternative detection technique using microstructured Si-PIN diodes is proposed
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Improved Upper Limit on the Neutrino Mass from a Direct Kinematic Method by KATRIN.
We report on the neutrino mass measurement result from the first four-week science run of the Karlsruhe Tritium Neutrino experiment KATRIN in spring 2019. Beta-decay electrons from a high-purity gaseous molecular tritium source are energy analyzed by a high-resolution MAC-E filter. A fit of the integrated electron spectrum over a narrow interval around the kinematic end point at 18.57 keV gives an effective neutrino mass square value of (-1.0_{-1.1}^{+0.9}) eV^{2}. From this, we derive an upper limit of 1.1 eV (90% confidence level) on the absolute mass scale of neutrinos. This value coincides with the KATRIN sensitivity. It improves upon previous mass limits from kinematic measurements by almost a factor of 2 and provides model-independent input to cosmological studies of structure formation
Reduction of stored-particle background by a magnetic pulse method at the KATRIN experiment
The KATRIN experiment aims to determine the effective electron neutrino mass with a sensitivity of 0.2 eV/c2 (%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 219Rn and 220Rn, 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
Reduction of stored-particle background by a magnetic pulse method at the KATRIN experiment
The KATRIN experiment aims to determine the effective electron neutrino mass with a sensitivity of 0.2 eV/c2 (%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 219Rn and 220Rn, 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
Precision measurement of the electron energy-loss function in tritium and deuterium gas for the KATRIN experiment
The KATRIN experiment is designed for a direct and model-independent
determination of the effective electron anti-neutrino mass via a high-precision
measurement of the tritium -decay endpoint region with a sensitivity on
of 0.2eV/c (90% CL). For this purpose, the -electrons
from a high-luminosity windowless gaseous tritium source traversing an
electrostatic retarding spectrometer are counted to obtain an integral spectrum
around the endpoint energy of 18.6keV. A dominant systematic effect of the
response of the experimental setup is the energy loss of -electrons from
elastic and inelastic scattering off tritium molecules within the source. We
determined the \linebreak energy-loss function in-situ with a pulsed
angular-selective and monoenergetic photoelectron source at various
tritium-source densities. The data was recorded in integral and differential
modes; the latter was achieved by using a novel time-of-flight technique.
We developed a semi-empirical parametrization for the energy-loss function
for the scattering of 18.6-keV electrons from hydrogen isotopologs. This model
was fit to measurement data with a 95% T gas mixture at 30K, as used in
the first KATRIN neutrino mass analyses, as well as a D gas mixture of 96%
purity used in KATRIN commissioning runs. The achieved precision on the
energy-loss function has abated the corresponding uncertainty of
[arXiv:2101.05253] in the KATRIN
neutrino-mass measurement to a subdominant level.Comment: 12 figures, 18 pages; to be submitted to EPJ
Analysis methods for the first KATRIN neutrino-mass measurement
We report on the dataset, data handling, and detailed analysis techniques of the first neutrino-mass measurement by the Karlsruhe Tritium Neutrino (KATRIN) experiment, which probes the absolute neutrino-mass scale via the β-decay kinematics of molecular tritium. The source is highly pure, cryogenic T2 gas. The β electrons are guided along magnetic field lines toward a high-resolution, integrating spectrometer for energy analysis. A silicon detector counts β electrons above the energy threshold of the spectrometer, so that a scan of the thresholds produces a precise measurement of the high-energy spectral tail. After detailed theoretical studies, simulations, and commissioning measurements, extending from the molecular final-state distribution to inelastic scattering in the source to subtleties of the electromagnetic fields, our independent, blind analyses allow us to set an upper limit of 1.1 eV on the neutrino-mass scale at a 90% confidence level. This first result, based on a few weeks of running at a reduced source intensity and dominated by statistical uncertainty, improves on prior limits by nearly a factor of two. This result establishes an analysis framework for future KATRIN measurements, and provides important input to both particle theory and cosmology
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