13 research outputs found
First operation of the KATRIN experiment with tritium
Artículo escrito por un elevado número de autores, solo se referencian el que aparece en primer lugar, el nombre del grupo de colaboración, si le hubiere, y los autores pertenecientes a la UA
Precision measurement of the electron energy-loss function in tritium and deuterium gas for the KATRIN experiment
Artículo escrito por un elevado número de autores, solo se referencian el que aparece en primer lugar, el nombre del grupo de colaboración, si le hubiere, y los autores pertenecientes a la UAMThe 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 β-decay endpoint region with a sensitivity on mν of 0.2 eV /c 2 (90% CL). For this purpose, the β-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 18.6 keV. A dominant systematic effect of the response of the experimental setup is the energy loss of β -electrons from elastic and inelastic scattering off tritium molecules within the source. We determined the 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 2 gas mixture at 30 K, as used in the first KATRIN neutrino-mass analyses, as well as a D 2 gas mixture of 96% purity used in KATRIN commissioning runs. The achieved precision on the energy-loss function has abated the corresponding uncertainty of σ(mν2) < 10-2eV2 [1] in the KATRIN neutrino-mass measurement to a subdominant leve
Versatile Confocal Raman Imaging Microscope Built from Off-the-Shelf Opto-Mechanical Components
Confocal Raman microscopic (CRM) imaging has evolved to become a key tool for spatially resolved, compositional analysis and imaging, down to the μm-scale, and nowadays one may choose between numerous commercial instruments. That notwithstanding, situations may arise which exclude the use of a commercial instrument, e.g., if the analysis involves toxic or radioactive samples/environments; one may not wish to render an expensive instrument unusable for other uses, due to contamination. Therefore, custom-designed CRM instrumentation—being adaptable to hazardous conditions and providing operational flexibility—may be beneficial. Here, we describe a CRM setup, which is constructed nearly in its entirety from off-the-shelf optomechanical and optical components. The original aim was to develop a CRM suitable for the investigation of samples exposed to tritium. For increased flexibility, the CRM system incorporates optical fiber coupling to both the Raman excitation laser and the spectrometer. Lateral raster scans and axial profiling of samples are facilitated by the use of a motorized xyz-translation assembly. Besides the description of the construction and alignment of the CRM system, we also provide (i) the experimental evaluation of system performance (such as, e.g., spatial resolution) and (ii) examples of Raman raster maps and axial profiles of selected thin-film samples (such as, e.g., graphene sheets)
Improved eV-scale sterile-neutrino constraints from the second KATRIN measurement campaign
Artículo escrito por un elevado número de autores, solo se referencian el que aparece en primer lugar, el nombre del grupo de colaboración, si le hubiere, y los autores pertenecientes a la UAMWe present the results of the light sterile neutrino search from the second Karlsruhe Tritium Neutrino (KATRIN) measurement campaign in 2019. Approaching nominal activity, 3.76 × 106 tritium β-electrons are analyzed in an energy window extending down to 40 eV below the tritium end point at E0 = 18.57 keV. We consider the 3ν + 1 framework with three active and one sterile neutrino flavors. The analysis is sensitive to a fourth mass eigenstate m42 ≲ 1600 eV2 and active-to-sterile mixing |Ue4|2 ≳ 6 × 10-3. As no sterile-neutrino signal was observed, we provide improved exclusion contours on m42 and |Ue4|2 at 95% C.L. Our results supersede the limits from the Mainz and Troitsk experiments. Furthermore, we are able to exclude the large Δm412 solutions of the reactor antineutrino and gallium anomalies to a great extent. The latter has recently been reaffirmed by the BEST Collaboration and could be explained by a sterile neutrino with large mixing. While the remaining solutions at small Δm412 are mostly excluded by short-baseline reactor experiments, KATRIN is the only ongoing laboratory experiment to be sensitive to relevant solutions at large Δm412 through a robust spectral shape analysi
The Generation and Analysis of Tritium-substituted Methane
An unavoidable category of molecular species in large-scale tritium
applications, such as nuclear fusion, are tritium-substituted hydrocarbons;
these form by radiochemical reactions in the presence of (circulating) tritium
and carbon (mainly from the steel of vessels and tubing). Tritiumsubstituted
methane species, CQ (with Q = H , D , T), are often the precursor for
higher-order reaction chains, and thus are of particular interest. Here we
describe the controlled production of CQ carried out in the CAPER facility
of the Tritium Laboratory Karlsruhe (TLK), exploiting catalytic reactions and
species-enrichment via the CAPER-integral permeator. CQ4 was generated in
substantial quantity (>1000 cm at ~850 mbar, with CQ - content of up to
~20 %). These samples were analyzed using laser Raman and mass spectrometry, to
determine the relative isotopologue composition and to trace the generation of
tritiated chain-hydrocarbons.Comment: 10 pages, 4 figures. This article has been accepted for publication
in Fusion Science and Technology, published by Taylor & Franci
Improving the Detection Limit in a Capillary Raman System for In Situ Gas Analysis by Means of Fluorescence Reduction
Raman spectroscopy for low-pressure or trace gas analysis is rather challenging, in particular in process control applications requiring trace detection and real-time response; in general, enhancement techniques are required. One possible enhancement approach which enjoys increasing popularity makes use of an internally-reflective capillary as the gas cell. However, in the majority of cases, such capillary systems were often limited in their achievable sensitivity by a significant fluorescence background, which is generated as a consequence of interactions between the laser light and optical glass components in the setup. In order to understand and counteract these problems we have investigated a range of fluorescence-reducing measures, including the rearrangement of optical elements, and the replacement of glass components--including the capillary itself--by metal alternatives. These studies now have led to a capillary setup in which fluorescence is practically eliminated and substantial signal enhancement over standard Raman setups is achieved. With this improved (prototype) setup, detection limits of well below 1 mbar could be obtained in sub-second acquisition times, demonstrating the potential of capillary Raman spectroscopy for real-time, in situ gas sensing and process control applications, down to trace level concentrations
First observation of tritium adsorption on graphene
In this work, we report on the first-ever studies of graphene exposed to
tritium gas in a controlled environment. The single layer graphene on
/Si substrate was exposed to 400 mbar of for a
total time of ~55 h. The resistivity of the graphene sample was measured
in-situ during tritium exposure using the Van der Pauw method. After the
exposure, the samples were scanned with a confocal Raman microscope to study
the effect of tritium on the graphene structure as well as the homogeneity of
spectral modifications. We found that the sheet resistance increases by three
orders of magnitude during the exposure. By Raman microscopy, we demonstrate
that the graphene film can withstand the bombardment from the beta-decay of
tritium, and primary and secondary ions. Additionally, the Raman spectra after
tritium exposure are comparable with previously observed results in
hydrogen-loading experiments carried out by other groups. By thermal annealing
we could demonstrate, using Raman spectral analysis, that the structural
changes were partially reversible. Considering all observations, we conclude
that the graphene film was at least partially tritiated during the tritium
exposure.Comment: Submitted to Nanoscale Advances (RSC), 14 pages, 4 figure
Versatile Confocal Raman Imaging Microscope Built from Off-the-Shelf Opto-Mechanical Components
Confocal Raman microscopic (CRM) imaging has evolved to become a key tool for spatially resolved, compositional analysis and imaging, down to the μm-scale, and nowadays one may choose between numerous commercial instruments. That notwithstanding, situations may arise which exclude the use of a commercial instrument, e.g., if the analysis involves toxic or radioactive samples/environments; one may not wish to render an expensive instrument unusable for other uses, due to contamination. Therefore, custom-designed CRM instrumentation—being adaptable to hazardous conditions and providing operational flexibility—may be beneficial. Here, we describe a CRM setup, which is constructed nearly in its entirety from off-the-shelf optomechanical and optical components. The original aim was to develop a CRM suitable for the investigation of samples exposed to tritium. For increased flexibility, the CRM system incorporates optical fiber coupling to both the Raman excitation laser and the spectrometer. Lateral raster scans and axial profiling of samples are facilitated by the use of a motorized xyz-translation assembly. Besides the description of the construction and alignment of the CRM system, we also provide (i) the experimental evaluation of system performance (such as, e.g., spatial resolution) and (ii) examples of Raman raster maps and axial profiles of selected thin-film samples (such as, e.g., graphene sheets)