The paper treats recent experiments measuring the endpoint region of tritium β-decay with high resolution, sensitivity and background rejection, using an electrostatic filter with adiabatic magnetic ...collimation. The spectra are analysed with respect to the neutrino mass. These results form the primary source for the present upper limit of the neutrino mass
m
ν
< 2 eV quoted by the particle data group. Particular attention is paid to the decisive influence which atomic and molecular physics effects take on the results. A brief outlook on future experiments is given.
We obtained very long relaxation times
T
1 of up to 120 h for the nuclear polarization of an optically pumped helium 3 gas. The glass containers were internally coated with metallic films such as ...bismuth or cesium. These findings will have applications in the field of helium magnetometers and polarized targets.
The goal of the KArlsruhe TRItrium Neutrino (KATRIN) experiment is the determination of the effective electron antineutrino mass with a sensitivity of 0.2eV/c2 at 90% C.L.11C.L. - confidence level.. ...This goal can only be achieved with a very low background level in the order of 10mcps22mcps - milli count per second. in the detector region of interest. A possible background source are α-decays on the inner surface of the KATRIN Main Spectrometer. Rydberg atoms, produced in sputtering processes accompanying the α-decays, are not influenced by electric or magnetic fields and freely propagate inside the vacuum of the Main Spectrometer. Here, they can be ionized by thermal radiation and the released electrons directly contribute to the KATRIN background. Two α-sources, 223Ra and 228Th, were installed at the Main Spectrometer with the purpose of temporarily increasing the background in order to study α-decay induced background processes. In this paper, we present a possible background generation mechanism and measurements performed with these two radioactive sources. Our results show a clear correlation between α-activity on the inner spectrometer surface and background from the volume of the spectrometer. Two key characteristics of the Main Spectrometer background – the dependency on the inner electrode offset potential, and the radial distribution – could be reproduced with this artificially induced background. These findings indicate a high contribution of α-decay induced events to the residual KATRIN background.
In the paper the ionization state of molecular tritium and electric potentials in a Windowless Gas Tritium Source (WGTS) of tritium β-decay experiment KATRIN are considered. The ionization processes ...in WGTS are sustained by β-electrons and so-called "secondary electrons", arising from inelastic and ionization collisions of "primary" β-electrons with tritium molecules. As a result in the WGTS tritium gas volume acts as a low-temperature and slightly ionized gas steady state close to quasi neutrality (the Debye length is small in comparison with the setup characteristical sizes). On the basis of an one-dimensional self-consistent model the WGTS plasma steady state is described and the influence of plasma phenomena on neutrino mass measuring process is discussed. It is found that electric potentials in a main plasma volume can not significantly make worse the measurement process. At the same time the nonequilibrium electron spectrum and fast plasma flow at the end of the tube can result in instabilities which are able to spoil slightly the β-electron spectrum endpoint. This problem must be carefully investigated further. For more reliable conclusions more detailed consideration is required that will include kinetic effects in the WGTS plasma.
► Development of a new BIXS-system for activity monitoring of gaseous tritium sources. ► High sensitivity by use of an low-noise easy to operate silicon drift detector. ► Gas-species independent ...tritium monitoring.
For monitoring and control of gaseous tritium sources in fuel circulation systems of fusion reactors beta induced X-ray spectrometry (BIXS) seems to be an applicable method. The characteristics of a BIXS monitoring setup built at TLK were examined. A low-noise silicon drift detector (SDD) was used together with two thin beryllium windows evaporated with gold films of 100nm for efficient X-ray production. The measured X-ray intensity was proportional to the tritium partial pressure and the average detection efficiency was evaluated as 32.6×10−8cps/Bq. A tritium memory effect was revealed. From the results it was concluded that such a monitoring system would be a useful complement for tritium analytics devices if well designed in terms of memory effect suppression.
We describe a
3
He magnetometer capable to measure high magnetic fields (
B
> 0.1 T) with a relative accuracy of better than 10
-12
. Our approach is based on the measurement of the free induction ...decay of gaseous, nuclear spin polarized
3
He following a resonant radio frequency pulse excitation. The measurement sensitivity can be attributed to the long coherent spin precession time T
2
∗
being of order minutes which is achieved for spherical sample cells in the regime of “motional narrowing” where the disturbing influence of field inhomogeneities is strongly suppressed. The
3
He gas is spin polarized in situ using a new, non-standard variant of the metastability exchange optical pumping. We show that miniaturization helps to increase T
2
∗
further and that the measurement sensitivity is not significantly affected by temporal field fluctuations of order 10
-4
.
To assess the feasibility of helium-3 magnetic resonance (MR) imaging with a three-dimensional fast low-angle shot (FLASH) sequence, He-3 gas (volume, 300 mL; pressure, 3 x 10(5) Pa; polarized up to ...45% by means of optimal pumping) was inhaled by five healthy volunteers and five patients with pulmonary diseases. All breath-hold examinations (22-42 seconds) were completed successfully. Normal ventilation was depicted with homogeneous high signal intensity, lesions were depicted as causing defects, and obstructive lung disease was depicted with severely inhomogeneous signal intensity.
We present results of laser spectroscopic high voltage measurements on the 5 ppm relative uncertainty level using a pump and probe scheme on Ca+ ions. With the two-stage laser interaction and with a ...reference measurement we can eliminate systematic effects like differences in contact potentials of electrode materials, thermo-electric voltages, and the unknown starting potential of the ions in the ion source. Our measurements are compatible with the 5 ppm precision limits of the high voltage dividers used for comparison and demonstrate an unprecedented increase in the accuracy of laser-based high voltage measurements by a factor of 20.
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