18 research outputs found
Minimal and complete set of descriptors for IR-absorption spectra of liquid H2âD2 mixtures
The IR spectra of liquid hydrogen isotopologues (Q = H, D, T, HD, HT, DT) are dominated by the interaction induced absorption. Therefore, the complexity tremendously increases with the number of different isotopologues in the sample. As we aim for a system independent calibration of IR absorption spectroscopy against all six isotopologues and three orthoâpara ratios, we need a minimal and complete set of descriptors to predict the spectra and to decrease the needed calibration effort. For this, we grouped the absorption lines into three groups: absorption on monomers, phonons, and molecular dimers. In particular, molecular dimers contribute to the absolute number of absorption lines in the spectra of mixed isotopologues. To develop and test the set of descriptors, we make use of three spectra: a pure H sample, a pure D sample, and a mixed HâD sample. We show a detailed analysis of these three spectra in the first and second vibrational branch in the range from 2000 cm to 9000 cm. The set of descriptors found within this work can be used to identify and predict all lines in this range for liquid HâD mixtures
Minimal and complete set of descriptors for IR-absorption spectra of liquid H2âD2 mixtures
The IR spectra of liquid hydrogen isotopologues (Q = H, D, T, HD, HT, DT) are dominated by the interaction induced absorption. Therefore, the complexity tremendously increases with the number of different isotopologues in the sample. As we aim for a system independent calibration of IR absorption spectroscopy against all six isotopologues and three orthoâpara ratios, we need a minimal and complete set of descriptors to predict the spectra and to decrease the needed calibration effort. For this, we grouped the absorption lines into three groups: absorption on monomers, phonons, and molecular dimers. In particular, molecular dimers contribute to the absolute number of absorption lines in the spectra of mixed isotopologues. To develop and test the set of descriptors, we make use of three spectra: a pure H sample, a pure D sample, and a mixed HâD sample. We show a detailed analysis of these three spectra in the first and second vibrational branch in the range from 2000 cm to 9000 cm. The set of descriptors found within this work can be used to identify and predict all lines in this range for liquid HâD mixtures
Kilogram scale throughput performance of the KATRIN tritium handling system
The Karlsruhe Tritium Neutrino (KATRIN) experiment aims to determine the effective mass of the electron antineutrino by investigating the tritium ÎČ-spectrum close to the energetic endpoint. To achieve this, there are stringent and challenging requirements on the stability of the gaseous tritium source. The tritium loop system has the task to provide the 95 %. KATRIN started full tritium operation in early 2019. This paper focusses on the observed radiochemical effects and confirms that non-negligible quantities during initial tritium operation have to be expected
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 ÎŒm-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 instrumentationâbeing adaptable to hazardous conditions and providing operational flexibilityâmay 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)
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
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
Photography-based taxonomy is inadequate, unnecessary, and potentially harmful for biological sciences
The question whether taxonomic descriptions naming new animal species without type specimen(s) deposited in collections should be accepted for publication by scientific journals and allowed by the Code has already been discussed in Zootaxa (Dubois & NemĂ©sio 2007; Donegan 2008, 2009; NemĂ©sio 2009aâb; Dubois 2009; Gentile & Snell 2009; Minelli 2009; Cianferoni & Bartolozzi 2016; Amorim et al. 2016). This question was again raised in a letter supported
by 35 signatories published in the journal Nature (Pape et al. 2016) on 15 September 2016. On 25 September 2016, the following rebuttal (strictly limited to 300 words as per the editorial rules of Nature) was submitted to Nature, which on
18 October 2016 refused to publish it. As we think this problem is a very important one for zoological taxonomy, this text is published here exactly as submitted to Nature, followed by the list of the 493 taxonomists and collection-based
researchers who signed it in the short time span from 20 September to 6 October 2016
Untersuchung systematischer Effekte und erste Tritiummessungen mit dem verbesserten Mainzer Neutrinomassenexperiment
Das Mainzer Neutrinomassenexperiment untersucht dasBetaspektrum von Tritium in der Naehe des Endpunktes undbestimmt daraus die Ruhemasse des Elektronantineutrinos. DieMessungen werden mit einem integrierenden, elektrostatischenGegenfeldspektrometer durchgefuehrt, bei dem das Prinzip dermagnetischen adiabatischen Kollimation angewandt wird, umgleichzeitig hohe Raumwinkelakzeptanz (bis maximal 2Pi) undeine sehr gute Energieaufloesung (E/dE=4000) zu erreichen.Als Tritiumquellen werden schockkondensierte Tritiumfilmeeingesetzt.Der Schwerpunkt dieser Arbeit bestand darin, das MainzerExperiment in entscheidenden Punkten zu verbessern. Das Zielwar, die Sensitivitaet auf die Neutrinomasse zu erhoehen unddie von der Troitskgruppe berichtete Anomalie imTritium-Betaspektrum zu ueberpruefen. Diese beschreibt
einemonoenergetische Line variabler Amplitude einige eVunterhalb des Betaendpunktes, deren Positioin mit einerHalbjahresperiode variiert.Nach dem Umbau 1995-1997 wurde der Endpunktsbereich desTritium-Betaspektrums bis Ende 1998 in 4 Messphasen ueberjeweils 1 Monat vermessen. Die erreichte Sensitivitaet derMainzer Daten war ausreichend, um die Troitsk Hypothese zuueberpruefen. Eine der 3 im Jahr 1998 durchgefuehrtenMessungen unterstuetzt die Hypothese, die Daten einer 6Monate spaeter durchgefuehrten Messung dagegen nicht. Somitstehen die Ergebnisse im Widerspruch zur postuliertenHalbjahresperiode.Die neuen Messungen zeigen bei Vergroesserung desAuswerteintervalls keinen Trend zu unphysikalisch negativenMassenquadraten. Es kann eine neue Neutrinomassenobergerenzevon 3.0 eV/c/c abgeleitet werden
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)