Search results for "Cathode"
showing 10 items of 296 documents
A spin rotator for producing a longitudinally polarized electron beam with MAMI
1993
Abstract The design and performance characteristics of a full 4 π-space spin rotator for 100 keV electrons are described. The spin rotator was developed as part of the acceleration scheme for polarized electrons in the MAINZ race track microtron cascade MAMI [1]. It allows to orientate the polarization vector in any direction before injection. Thus it is possible to optimize the longitudinal polarization component, required for experiments with polarized high energy electrons, at target position. With this scheme various experimental halls can be supplied with longitudinally polarized electrons in the full energy range of MAMI between 180 and 855 MeV.
Future Experimental Developments for Few-Body Physics at Mainz
1986
The racetrack microtron MAMI B [1] now under construction at Mainz will provide a high-intensity electron beam with energies up to 840 MeV. The 100% duty factor, high-quality beam is considered to be ideal for the investigation of the nucleus in the medium energy region. Coincidence experiments with the detection of the scattered electron and the hadronic reaction products will become possible in a wide kinematical range yielding the information about the response of the nucleus to the transferred energy and momentum. By the method of bremsstrahlung tagging intense secondary photon beams with high monochromacity and well known fluxes will be available for photonuclear research work. Further…
Expansion cone for the 3-inch PMTs of the KM3NeT optical modules
2013
[EN] Detection of high-energy neutrinos from distant astrophysical sources will open a new window on the Universe. The detection principle exploits the measurement of Cherenkov light emitted by charged particles resulting from neutrino interactions in the matter containing the telescope. A novel multi-PMT digital optical module (DOM) was developed to contain 31 3-inch photomultiplier tubes (PMTs). In order to maximize the detector sensitivity, each PMT will be surrounded by an expansion cone which collects photons that would otherwise miss the photocathode. Results for various angles of incidence with respect to the PMT surface indicate an increase in collection efficiency by 30% on average…
Ab initio study of phase competition in (La1−c,Src)CoO3 solid solutions
2013
Abstract (La 1 − c ,Sr c )CoO 3 (LSC) solid solutions are promising materials for high temperature electrochemical cells and cathodes of solid oxide fuel cells. The Density Functional Theory (DFT) was applied to calculate the energies of the different superstructures in LSC which are stable with respect to formation of anti-phase domains. The energy parameters determining the relative stability of the cubic superstructures (phases) are extracted from these calculations. Using the Concentration Wave formalism and the energy parameters for different phases from DFT calculations, the temperature dependences of the long-range order parameters were obtained characterizing the order–disorder tran…
Electrode–Electrolyte Compatibility in Solid-Oxide Fuel Cells: Investigation of the LSM–LNC Interface with X-ray Microspectroscopy
2015
Ca:LaNbO4 (LNC) constitutes the last real breakthrough in high-temperature proton conductors, with better chemical and mechanical stability with respect to cerate and zirconate perovskites. However, the low amount of bivalent dopant that can be hosted in the LaNbO4 matrix poses a limit to the proton concentration in the electrolyte. Using synchrotron X-ray microspectroscopy, we investigated the compatibility of annealed LNC/LSM electrolyte/cathode bilayers for proton-conducting SOFCs. The element maps are complemented by microEXAFS and microXANES, giving information on the fate of different cations after diffusion. The X-ray microspectroscopy approach described here is applied for the first…
On the Origin of Light Emission in Silicon Rich Oxide Obtained by Low-Pressure Chemical Vapor Deposition
2012
Silicon Rich Oxide (SRO) has been considered as a material to overcome the drawbacks of silicon to achieve optical functions. Various techniques can be used to produce it, including Low-Pressure Chemical Vapor Deposition (LPCVD). In this paper, a brief description of the studies carried out and discussions of the results obtained on electro-, cathode-, and photoluminescence properties of SRO prepared by LPCVD and annealed at 1,100°Care presented. The experimental results lead us to accept that SRO emission properties are due to oxidation state nanoagglomerates rather than to nanocrystals. The emission mechanism is similar to Donor-Acceptor decay in semiconductors, and a wide emission spectr…
Dynamic doping in planar ionic transition metal complex-based light-emitting electrochemical cells
2013
Using a planar electrode geometry, the operational mechanism of iridium(III) ionic transition metal complex (iTMC)-based light-emitting electrochemical cells (LECs) is studied by a combination of fluorescence miscroscopy and scanning Kelvin probe microscopy (SKPM). Applying a bias to the LECs leads to the quenching of the photoluminescence (PL) in between the electrodes and to a sharp drop of the electrostatic potential in the middle of the device, far away from the contacts. The results shed light on the operational mechanism of iTMC-LECs and demonstrate that these devices work essentially the same as LECs based on conjugated polymers do, i.e., according to an electrochemical doping mechan…
Photoemission of spin-polarized electrons from negative electron affinity GaAsP
1979
GaAs0.62P0.38 activated to negative electron affinity and irradiated with circularly polarized light of a wavelength shorter than approximately 680 nm emits electrons whose spins are mainly oriented antiparallel to the photon spins. At 650 nm a degree of electron spin polarization around 40% is observed. The spectrum of spin polarization of the photoelectrons is similar to that known from GaAs cathodes but is shifted to shorter wavelengths. 25 μA current of spin-polarized electrons were achieved with a 5 mW He-Ne laser.
First transmission of electrons and ions through the KATRIN beamline
2018
The Karlsruhe Tritium Neutrino (KATRIN) experiment is a large-scale effort to probe the absolute neutrino mass scale with a sensitivity of 0.2 eV (90% confidence level), via a precise measurement of the endpoint spectrum of tritium β-decay. This work documents several KATRIN commissioning milestones: the complete assembly of the experimental beamline, the successful transmission of electrons from three sources through the beamline to the primary detector, and tests of ion transport and retention. In the First Light commissioning campaign of autumn 2016, photoelectrons were generated at the rear wall and ions were created by a dedicated ion source attached to the rear section; in July 2017, …
Reducing the contribution of the photoemission process to the unwanted beam in photoelectron sources at accelerators
2017
Negative electron affinity (NEA) GaAs photocathodes show different pulse responses depending on the wavelength of photoexcitation. The pulse response at 800 nm shows a long and relatively intense tail, whereas at 400 nm, a tail of similar shape but with an intensity lower by around two orders of magnitude is observed. We explain this behavior with the specific properties of NEA photocathodes and compare it with the response of a positive electron affinity photocathode.