Effect of the surface temperature on surface morphology, deuterium retention and erosion of EUROFER steel exposed to low-energy, high-flux deuterium plasma

Samples of EUFROFER, a reduced activation ferritic martensitic steel, were exposed in the linear plasma device Pilot-PSI to a deuterium (D) plasma with incident ion energy of similar to 40 eV and incident D flux of 2-6 x10(23) D/m(2) s to fluences up to 10 27 D/m(2) at surface temperatures ranging from 400 K to 950 K. The main focus of the study lays on the surface morphology changes dependent on the surface temperature and the surface composition evolution, e.g., the enrichment in tungsten; but also the erosion and the D retention are studied. The created surface morphology varies strongly with surface temperature from needle-like to corral-like structures. The visible lateral length scale of the formed structures is in the range of tens of nanometres to above 1 mu m and exhibits two thermal activated regimes below and above similar to 770 K with activation energies of 0.2 eV and 1.3 eV, respectively. The lateral variation of the enrichment of heavy elements on the surface is correlated to this surface morphology at least in the high temperature regime, independent of the origin of the enrichment (intrinsic from the sample or deposited by the plasma). Also the erosion exhibits temperature dependence at least above similar to 770 K as well as a fluence dependence. The amount of deuterium retained in the top 500 nm is almost independent of the exposure temperature and is of the order of 10(18) D/m(2), which would correspond to a sub-monolayer D coverage on the surface. The retained D in the volume summing up over the complete samples exceeds the D retained close to the surface by one order of magnitude. (C) 2017 The Authors. Published by Elsevier Ltd. This is an open access article under the CC BY-NC-ND license

Generating quantizing pseudomagnetic fields by bending graphene ribbons

We analyze the mechanical deformations that are required to create uniform pseudomagnetic fields in graphene. It is shown that, if a ribbon is bent in-plane into a circular arc, this can lead to fields exceeding 10 T, which is sufficient for the observation of pseudo-Landau quantization. The arc geometry is simpler than those suggested previously and, in our opinion, has much better chances to be realized experimentally soon. The effects of a scalar potential induced by dilatation in this geometry is shown to be negligible.F.G. acknowledges support from MICINN Spain through Grants No. FIS2008-00124 and No. CONSOLIDER CSD2007-00010, and by the Comunidad de Madrid, through CITECNOMIK. M.I.K. acknowledges support from FOM the Netherlands. This work was also supported by EPSRC U.K., ONR, AFOSR, and the Royal Society. We are thankful to Y.-W. Son for useful insights concerning Ref. 17 and related work.Peer reviewe

All-Optical Nonzero-Field Vector Magnetic Sensor For Magnetoencephalography

We present the concept and the results of an investigation of an all-optical vector magnetic field sensor scheme developed for biological applications such as non-zero field magnetoencephalography and magnetocardiography. The scheme differs from the classical two-beam Bell-Bloom scheme in that the detecting laser beam is split into two beams, which are introduced into the cell in orthogonal directions, and the ratio of the amplitudes of the magnetic resonance signals in these beams and their phase difference are measured; strong optical pumping from the lower hyperfine level of the ground state ensures the resonance line narrowing, and detection in two beams is carried out in a balanced schemes by measuring the beam polarization rotation. The proposed sensor is compact, resistant to variations of parameters of laser radiation and highly sensitive to the angle of deflection of the magnetic field vector - with an estimated scalar sensitivity of the order of 16 fT/Hz1/2 in 8x8x8 mm3 cell, an angular sensitivity of 4x10-7 rad, or 0.08'', was demonstrated

Resonant excitations of the 't Hooft-Polyakov monopole

The spherically symmetric magnetic monopole in an SU(2) gauge theory coupled to a massless Higgs field is shown to possess an infinite number of resonances or quasinormal modes. These modes are eigenfunctions of the isospin 1 perturbation equations with complex eigenvalues, $E_n=\omega_n-i\gamma_n$, satisfying the outgoing radiation condition. For $n\to\infty$, their frequencies $\omega_n$ approach the mass of the vector boson, $M_W$, while their lifetimes $1/\gamma_n$ tend to infinity. The response of the monopole to an arbitrary initial perturbation is largely determined by these resonant modes, whose collective effect leads to the formation of a long living breather-like excitation characterized by pulsations with a frequency approaching $M_W$ and with an amplitude decaying at late times as $t^{-5/6}$.Comment: 4 page

Mitigation of nonlinear transmission effects for OFDM 16-QAM optical signal using adaptive modulation

The impact of the fiber Kerr effect on error statistics in the nonlinear (high power) transmission of the OFDM 16-QAM signal over a 2000 km EDFA-based link is examined. We observed and quantified the difference in the error statistics for constellation points located at three power-defined rings. Theoretical analysis of a trade-off between redundancy and error rate reduction using probabilistic coding of three constellation power rings decreasing the symbol-error rate of OFDM 16-QAM signal is presented. Based on this analysis, we propose to mitigate the nonlinear impairments using the adaptive modulation technique applied to the OFDM 16-QAM signal. We demonstrate through numerical modelling the system performance improvement by the adaptive modulation for the large number of OFDM subcarriers (more than 100). We also show that a similar technique can be applied to single carrier transmission

New Path Equations in Absolute Parallelism Geometry

The Bazanski approach, for deriving the geodesic equations in Riemannian geometry, is generalized in the absolute parallelism geometry. As a consequence of this generalization three path equations are obtained. A striking feature in the derived equations is the appearance of a torsion term with a numerical coefficients that jumps by a step of one half from equation to another. This is tempting to speculate that the paths in absolute parallelism geometry might admit a quantum feature.Comment: 4 pages Latex file Journal Reference: Astrophysics and space science 228, 273, (1995

Phonon cooling and lasing with nitrogen-vacancy centers in diamond

We investigate the strain-induced coupling between a nitrogen-vacancy impurity and a resonant vibrational mode of a diamond nanoresonator. We show that under near-resonant laser excitation of the electronic states of the impurity, this coupling can modify the state of the resonator and either cool the resonator close to the vibrational ground state or drive it into a large-amplitude coherent state. We derive a semiclassical model to describe both effects and evaluate the stationary state of the resonator mode under various driving conditions. In particular, we find that by exploiting resonant single- and multiphonon transitions between near-degenerate electronic states, the coupling to high-frequency vibrational modes can be significantly enhanced and dominate over the intrinsic mechanical dissipation. Our results show that a single nitrogen-vacancy impurity can provide a versatile tool to manipulate and probe individual phonon modes in nanoscale diamond structures.Physic