79 research outputs found
Solid electron sources for the energy scale monitoring in the KATRIN experiment
Das Ziel des Tritium Beta-Zerfallsexperiments KATRIN ist die direkte modellunabhängige Bestimmung der Elektron-Antineutrinomasse. Es werden Elektronenspektrometer vom Typ MAC-E-Filter verwendet, für die eine sehr hohe Stabilität des Filterpotenzials erforderlich ist. Diese Arbeit testet erfolgreich 83Rb/83mKr Festkörperkalibrationsquellen, die für die kontinuierliche Überwachung des Filterpotenzials des Hauptspektrometers mit einem zusätzlichen Spektrometer auf derselben Hochspannung vermessen werden. Die Kalibrationsquellen basieren auf Konversionselektronen von 83mKr aus dem 83Rb Zerfall. Es wird gezeigt dass die K-32 Konversionselektronenlinie (kinetische Energie 17,8 keV, Linienbreite 2,7 eV) den Anspruch des KATRIN-Experiments von ±1,6 ppm pro Monat an die relative Energiestabilität erfüllt. Die ionenimplantierten 83Rb/83mKr-Quellen können als das Standardwerkzeug für die kontinuierliche Überwachung der KATRIN-Energieskalastabilität mit sub-ppm Präzision empfohlen werden. The KATRIN experiment aims at the direct model-independent determination
of the electron antineutrino mass via the measurement of the endpoint
region of tritium beta-decay spectrum. The electron spectrometer of the
MAC-E filter type is used, requiring very high stability of the
filtering potential. This work successfully proves the feasibility of
solid 83Rb/83mKr calibration electron source which is utilized in the
additional monitor spectrometer sharing the high voltage with the main
spectrometer. This way the filtering potential of KATRIN is continuously
monitored. The calibration source employs conversion electrons of 83mKr
which is generated by 83Rb. The K-32 conversion electron line (kinetic
energy 17.8 keV, line width 2.7 eV) is shown to fulfill the KATRIN
requirement of the relative energy stability of ±1.6 ppm per month. The
ion-implanted 83Rb/83mKr sources are recommended as a standard tool for
continuous monitoring of KATRIN energy scale stability with the sub-ppm
precision
Ultra-stable implanted 83Rb/83mKr electron sources for the energy scale monitoring in the KATRIN experiment
The KATRIN experiment aims at the direct model-independent determination of
the average electron neutrino mass via the measurement of the endpoint region
of the tritium beta decay spectrum. The electron spectrometer of the MAC-E
filter type is used, requiring very high stability of the electric filtering
potential. This work proves the feasibility of implanted 83Rb/83mKr calibration
electron sources which will be utilised in the additional monitor spectrometer
sharing the high voltage with the main spectrometer of KATRIN. The source
employs conversion electrons of 83mKr which is continuously generated by 83Rb.
The K-32 conversion line (kinetic energy of 17.8 keV, natural line width of 2.7
eV) is shown to fulfill the KATRIN requirement of the relative energy stability
of +/-1.6 ppm/month. The sources will serve as a standard tool for continuous
monitoring of KATRIN's energy scale stability with sub-ppm precision. They may
also be used in other applications where the precise conversion lines can be
separated from the low energy spectrum caused by the electron inelastic
scattering in the substrate.Comment: 30 pages, 10 figures, 1 table, minor revision of the preprint,
accepted by JINST on 5.2.201
Melting of Partially Fluorinated Graphene: From Detachment of Fluorine Atoms to Large Defects and Random Coils
The melting of fluorographene is very unusual and depends strongly on the
degree of fluorination. For temperatures below 1000 K, fully fluorinated
graphene (FFG) is thermo-mechanically more stable than graphene but at
T2800 K FFG transits to random coils which is almost twice lower
than the melting temperature of graphene, i.e. 5300 K. For fluorinated graphene
(PFG) up to 30 % ripples causes detachment of individual F-atoms around 2000 K
while for 40-60 % fluorination, large defects are formed beyond 1500 K and
beyond 60% of fluorination F-atoms remain bonded to graphene until melting. The
results agree with recent experiments on the dependence of the reversibility of
the fluorination process on the percentage of fluorination.Comment: 16 pages, 6 figure
On-Surface Synthesis of Gold Porphyrin Derivatives via a Cascade of Chemical Interactions: Planarization, Self-Metalation, and Intermolecular Coupling
A UV LED-based fast-pulsed photoelectron source for time-of-flight studies
We report on spectroscopy and time-of-flight measurements using an 18 keV
fast-pulsed photoelectron source of adjustable intensity, ranging from single
photoelectrons per pulse to 5 photoelectrons per microsecond at pulse
repetition rates of up to 10 kHz. Short pulses between 40 ns and 40
microseconds in length were produced by switching light emitting diodes with
central output wavelengths of 265 nm and 257 nm, in the deep ultraviolet (or
UV-C) regime, at kHz frequencies. Such photoelectron sources can be useful
calibration devices for testing the properties of high-resolution electrostatic
spectrometers, like the ones used in current neutrino mass searches.Comment: 16 pages, 11 figure
Effect of a sweeping conductive wire on electrons stored in the Penning trap between the KATRIN spectrometers
The KATRIN experiment is going to search for the mass of the electron
antineutrino down to 0.2 eV/c^2. In order to reach this sensitivity the
background rate has to be understood and minimised to 0.01 counts per second.
One of the background sources is the unavoidable Penning trap for electrons due
to the combination of the electric and magnetic fields between the pre- and the
main spectrometer at KATRIN. In this article we will show that by sweeping a
conducting wire periodically through such a particle trap stored particles can
be removed, an ongoing discharge in the trap can be stopped, and the count rate
measured with a detector looking at the trap is reduced.Comment: Final version published in EPJ A, 14 pages, 19 figures (21 files
Stochastic Heating by ECR as a Novel Means of Background Reduction in the KATRIN Spectrometers
The primary objective of the KATRIN experiment is to probe the absolute
neutrino mass scale with a sensitivity of 200 meV (90% C.L.) by precision
spectroscopy of tritium beta-decay. To achieve this, a low background of the
order of 10^(-2) cps in the region of the tritium beta-decay endpoint is
required. Measurements with an electrostatic retarding spectrometer have
revealed that electrons, arising from nuclear decays in the volume of the
spectrometer, are stored over long time periods and thereby act as a major
source of background exceeding this limit. In this paper we present a novel
active background reduction method based on stochastic heating of stored
electrons by the well-known process of electron cyclotron resonance (ECR). A
successful proof-of-principle of the ECR technique was demonstrated in test
measurements at the KATRIN pre-spectrometer, yielding a large reduction of the
background rate. In addition, we have carried out extensive Monte Carlo
simulations to reveal the potential of the ECR technique to remove all trapped
electrons within negligible loss of measurement time in the main spectrometer.
This would allow the KATRIN experiment attaining its full physics potential
Hematene: A sustainable 2D conductive platform for visible-light-driven photocatalytic ammonia decomposition
The emerging class of 2D non-van der Waals (n-vdW) materials, including 2D iron oxides, possesses unique
properties and high applicability, making them attractive for various technological applications. However, the
synthesis of these materials through a scalable and eco-friendly method remains a challenge, as most known
chemical exfoliation processes require toxic organic solvents. In this study, we report a green synthesis of 2D
hematene (α-Fe2O3) using an ultrasound-supported exfoliation method of earth-abundant iron oxide ore in a pure
aqueous solution. The resulting hematene sheets, only a few nanometers thick, exhibit superior electrochemical
performance in terms of charge transfer processes, making them ideal for photocatalytic applications. By doping
a conductive hematene substrate with ruthenium, we demonstrate a synergistic effect for generating electrons
and holes under visible light irradiation. Using this approach, we successfully decomposed ammonia into
hydrogen and nitrogen, highlighting the potential of this novel class of environmentally-friendly photocatalysts
for clean energy production. Overall, our water-assisted scalable synthesis of hematene offers a promising
strategy for producing efficient and sustainable photocatalysts.Web of Science34art. no. 10188
Graphene-based metal-organic framework hybrids for applications in catalysis, environmental, and energy technologies
Current energy and environmental challenges demand the development and design of multifunctional porous materials with tunable properties for catalysis, water purification, and energy conversion and storage. Because of their amenability to de novo reticular chemistry, metal-organic frameworks (MOFs) have become key materials in this area. However, their usefulness is often limited by low chemical stability, conductivity and inappropriate pore sizes. Conductive two-dimensional (2D) materials with robust structural skeletons and/or functionalized surfaces can form stabilizing interactions with MOF components, enabling the fabrication of MOF nanocomposites with tunable pore characteristics. Graphene and its functional derivatives are the largest class of 2D materials and possess remarkable compositional versatility, structural diversity, and controllable surface chemistry. Here, we critically review current knowledge concerning the growth, structure, and properties of graphene derivatives, MOFs, and their graphene@MOF composites as well as the associated structure- property-performance relationships. Synthetic strategies for preparing graphene@MOF composites and tuning their properties are also comprehensively reviewed together with their applications in gas storage/separation, water purification, catalysis (organo-, electro-, and photocatalysis), and electrochemical energy storage and conversion. Current challenges in the development of graphene@MOF hybrids and their practical applications are addressed, revealing areas for future investigation. We hope that this review will inspire further exploration of new graphene@MOF hybrids for energy, electronic, biomedical, and photocatalysis applications as well as studies on previously unreported properties of known hybrids to reveal potential "diamonds in the rough".Web of Science12224173381724
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