Search results for "electromagnetic"
showing 10 items of 1595 documents
Electromagnetically induced transparency with standing-wave drive in the frequency up-conversion regime
2003
We study Electromagnetically Induced Transparency in Doppler-broadened three-level media for probe to drive field frequency ratio R<1 and moderate drive intensities. We show that in this regime a standing-wave drive is more efficient than a travelling-wave one, specially when R is close to half integer values.
Combination of 3 Different Measurements: Branching Fractions, Radiative Lifetimes, and Absorption Oscillator Strengths- a Good Opportunity for the An…
2021
We present the method and setup for determination and self-testing of atomic radiative constants: transition probabilities, oscillator strengths and natural lifetimes. We describe how it works in simple 4 level scheme, present our experimental setup, and preliminary results for As I branching fractions, and discuss some aspects of future development. This method can be valuable for analyzing the results from different experiments performed by various authors and methods without directly re-measuring them. For example, in astrophysics is very important to select correct oscillator strengths for evaluation element abundances in stars and interstellar media since inaccurate data lead to uncert…
Comparison of Hinode/XRT and RHESSI detection of hot plasma in the non-flaring solar corona
2009
We compare observations of the non-flaring solar corona made simultaneously with Hinode/XRT and with RHESSI. The analyzed corona is dominated by a single active region on 12 November 2006. The comparison is made on emission measures. We derive emission measure distributions vs temperature of the entire active region from multifilter XRT data. We check the compatibility with the total emission measure values estimated from the flux measured with RHESSI if the emission come from isothermal plasma. We find that RHESSI and XRT data analyses consistently point to the presence of a minor emission measure component peaking at log T ~ 6.8-6.9. The discrepancy between XRT and RHESSI results is withi…
Normal-state bubbles and lamellae in type-I superconductors
2005
International audience; We report an extensive study of the formation of normal-state domains in type-I superconductors. Domain patterns are first considered theoretically. The magnetic interaction between domains is described in the framework of the ``current-loop'' model: the intermediate state is modeled by a set of loops of screening current encircling the domains and interacting as in the free space. This system is shown to be formally equivalent to a set of uniformly magnetized domains. An extension of the current-loop model is proposed to take into account the constraint of the magnetic shielding by the superconducting regions. We determine the free energy of a hexagonal array of cyl…
Spectral broadening by incomplete thermalization of the energy in X-ray microcalorimeters with superconducting absorber and NTD-Ge thermal sensor
2004
Abstract We present a model of the response of a cryogenic microcalorimeter with superconducting absorber and phonon sensitive thermal sensor to the absorption of X-ray photons. The model is based on the main microscopic processes responsible for the thermalization of the deposited energy. We use a system of rate equations to describe the energy downconversion in the superconductor and transport to the thermal sensor. The model is a tool to investigate the thermalization efficiency with respect to the device characteristics (i.e. absorber material, geometry), in order to optimize the performances of these detectors. As a first case study, we report results of simulations for a microcalorime…
Dyakonons in hyperbolic metamaterials
2013
We have analyzed surface-wave propagation that takes place at the boundary between an isotropic medium and a semi-infinite metal-dielectric periodic medium cut normally to the layers. In the range of frequencies where the periodic medium shows hyperbolic space dispersion, hybridization of surface waves (dyakonons) occurs. At low to moderate frequencies, dyakonons enable tighter confinement near the interface in comparison with pure SPPs. On the other hand, a distinct regime governs dispersion of dyakonons at higher frequencies. Full Text: PDF References Z. Ruan, M. Qiu, "Slow electromagnetic wave guided in subwavelength region along one-dimensional periodically structured metal surface", Ap…
Near-field optics theories
1996
The development of near-field optics theory is reviewed. We first recall that near-field optics is not limited to near-field microscopy. Broadly speaking, it concerns phenomena involving evanescent electromagnetic waves. The importance of such waves was ignored for a long time in optical and surface physics until the emergence of scanning near-field optical microscopes. Taking evanescent waves into account prevents the use of any simple approximation in the set of Maxwell's equations. The various theoretical approaches of near-field optics are discussed from the point of view of their ability to assess evanescent electromagnetic waves. We discuss the main results of the application of the v…
To the theory of high-power gyrotrons with uptapered resonators
2010
In high-power gyrotrons it is desirable to combine an optimal resonator length with the optimal value of the resonator quality factor. In resonators with the constant radius of the central part, the possibilities of this combination are limited because the quality factor of the resonator sharply increases with its length. Therefore the attempts to increase the length for maximizing the efficiency leads to such increase in the quality factor which makes the optimal current too small. Resonators with slightly uptapered profiles offer more flexibility in this regard. In such resonators, one can separate optimization of the interaction length from optimization of the quality factor because the …
3-D Shielding Analyses of the Vertical and Mid-Plane Ports in ITER
1996
A three dimensional (3-D) shielding analysis of the International Thermonuclear Experimental Reactor (ITER) has been performed with the aim of calculating the nuclear heating on the magnet system, correlating it to the existing vertical and horizontal ports. When these openings are left unshielded, more than 50 kW are calculated for the upper half of Toroidal Field Coil system and two of the Poloidal Field Coils. A simple plug, with same thickness as of the vacuum vessel can lower the heating to meet the imposed requirements. 5 refs., 6 figs., 4 tabs.
A Ioffe Trap Magnet for the Project 8 Atom Trapping Demonstrator
2020
The goal of the Project 8 experiment (B. Monreal and J. Formaggio, 2009) is to measure the absolute neutrino mass using tritium, which involves precisely measuring the energies of the beta-decay electrons in the high-energy tail of the spectrum (A. A. Esfahani et al. , 2017). The experimental installation of Project 8 Atom Trapping Demonstrator requires a magnet with rather unusual field properties. The magnet has to contain within the cold mass a large volume enclosed by a continuous, uninterrupted boundary higher than 2 T, whereas the field in a substantial volume inside this boundary has to be of the order of 10−4 T or less. A 1-T solenoid field provides the background field necessary fo…