Search results for "electron density"
showing 10 items of 428 documents
Plasma heating power dissipation in low temperature hydrogen plasmas
2015
A theoretical framework for power dissipation in low temperature plasmas in corona equilibrium is developed. The framework is based on fundamental conservation laws and reaction cross sections and is only weakly sensitive to plasma parameters, e.g., electron temperature and density. The theory is applied to low temperature atomic and molecular hydrogen laboratory plasmas for which the plasma heating power dissipation to photon emission, ionization, and chemical potential is calculated. The calculated photon emission is compared to recent experimental results.
Higher-order Kerr effects improve quantitative modelling of harmonics generation and laser filamentation
2013
The consideration of the higher-order Kerr effect (HOKE) drastically improves the quantitative agreement between measured and simulated harmonic yield as well as intensity and electron density in laser filaments generated by pulses below a few hundreds of fs. In longer pulses, the plasma defocusing plays a much more important role.
Experimental Stark-broadening studies of the NI multiplet $\mathsf{(^{1}D) 3s^{2}D - (^{1}D)3p^{2}P^{o}}$ at 7904.5 �
2004
Experimental Stark-broadening studies of the NI multiplet $(^{1}{\rm D})3s$ $^{2}{\rm D} - (^{1}{\rm D})3p$ $^{2}{\rm P}^{\rm o}$ are reported. Line shape measurements were performed using a wall-stabilized arc operated at atmospheric pressure in helium with small amounts of nitrogen and hydrogen. The radiation of the plasma emitted from nearly homogeneous plasma layers in end-on direction was measured using a grating spectrometer equipped with a charge-coupled device (CCD) detector. The arc current was varied from 35 to 50 A in order to obtain different plasma conditions (electron densities and temperatures). The so-called j(x) profiles of Griem, convoluted with the corresponding Doppler a…
Tuning the exciton luminescence in an acoustically depleted two-dimensional electron gas
2007
Standing-wave piezoelectric fields can be used to vary spatially and temporally charge conditions in $\mathrm{Ga}\mathrm{As}∕\mathrm{Al}\mathrm{Ga}\mathrm{As}$ quantum wells (QWs), offering a versatile tool to control the two-dimensional electron gas (2DEG) density in the well. A $\mathrm{Li}\mathrm{Nb}{\mathrm{O}}_{3}$ piezoelectric resonator imparts a MHz-frequency oscillating piezoelectric field with a controllable ratio of the in-plane and the vertical field components to a 2DEG placed in close proximity to the plate surface. This allows us to dynamically tune the charge state in the plane of the QW and to influence the photoluminescence spectra. It is found that spatially distributed r…
Rotational and vibrational spectra of quantum rings
2000
One can confine the two-dimensional electron gas in semiconductor heterostructures electrostatically or by etching techniques such that a small electron island is formed. These man-made ``artificial atoms'' provide the experimental realization of a text-book example of many-particle physics: a finite number of quantum particles in a trap. Much effort was spent on making such "quantum dots" smaller and going from the mesoscopic to the quantum regime. Far-reaching analogies to the physics of atoms, nuclei or metal clusters were obvious from the very beginning: The concepts of shell structure and Hund's rules were found to apply -- just as in real atoms! In this Letter, we report the discovery…
Magnus expansion and the two-neutrino oscillations in matter
1990
We show that the Magnus expansion can help to deal with the problem of matter-neutrino oscillations in the nonadiabatic regime of the two-neutrino-flavor case. An analytic result for the electron-neutrino survival probability is derived in a quite simple way without reference to any particular electron density.
X-ray spectroscopy of the Hertzsprung-gap giant star 31 Com, observed with XMM-Newton
2003
We have analysed the XMM-Newton X-ray spectra of the yellow giant 31 Com with the aim of deriving information on the coronal structures of this archetypical Hertzsprung-gap star. To determine the emission measure distribution vs. temperature, EM(T), and the elemental abundances of the coronal plasma, with an accurate line-based approach, we have developed a new method for simple and accurate line measurements, based on rebinning and co-adding the two RGS spectra. We have reconstructed the EM(T) independently with both APED and CHIANTI atomic databases in order to investigate possible differences in the final outcome of the analysis, and we have obtained consistent results. The derived emiss…
A status report of the multipurpose superconducting electron cyclotron resonance ion source
2007
Intense heavy ion beam production with electron cyclotron resonance (ECR) ion sources is a common requirement for many of the accelerators under construction in Europe and elsewhere. An average increase of about one order of magnitude per decade in the performance of ECR ion sources was obtained up to now since the time of pioneering experiment of R. Geller at CEA, Grenoble, and this trend is not deemed to get the saturation at least in the next decade, according to the increased availability of powerful magnets and microwave generators. Electron density above 1013 cm(-3) and very high current of multiply charged ions are expected with the use of 28 GHz microwave heating and of an adequate …
X-ray emission from MP Muscae: an old classical T Tauri star
2007
We study the properties of X-ray emitting plasma of MP Mus, an old classical T Tauri star. We aim at checking whether an accretion process produces the observed X-ray emission and at deriving the accretion parameters and the characteristics of the shock-heated plasma. We compare the properties of MP Mus with those of younger classical T Tauri stars to test whether age is related to the properties of the X-ray emission plasma. XMM-Newton X-ray spectra allows us to measure plasma temperatures, abundances, and electron density. In particular the density of cool plasma probes whether X-ray emission is produced by plasma heated in the accretion process. X-ray emission from MP Mus originates from…
Amplitude modulation technique for designing metalenses with apodized and enhanced resolution focal spots
2017
Abstract In this paper we show that engineering both phase and amplitude of the scattered light can be employed in designing metalenses with either higher resolution or apodized focal spots. C-shaped split-ring micro-resonators (CSRRs) with different geometrical parameters are selected to have a full control of amplitude and phase. While phase engineering is necessary for light focusing, amplitude modulation of the scattered wave can be applied to characterize the focal point properties such as resolution gain and sidelobe level. We show that both axial and transverse resolution improvement or apodization is possible in the far-field region by applying proper amplitude function. Amplitude m…