Mass Measurements and the Bound--Electron g Factor

The accurate determination of atomic masses and the high-precision measurement of the bound-electron g factor are prerequisites for the determination of the electron mass, which is one of the fundamental constants of nature. In the 2002 CODATA adjustment [P. J. Mohr and B. N. Taylor, Rev. Mod. Phys. 77, 1 (2005)], the values of the electron mass and the electron-proton mass ratio are mainly based on g factor measurements in combination with atomic mass measurements. In this paper, we briefly discuss the prospects for obtaining other fundamental information from bound-electron g factor measurements, we present some details of a recent investigation of two-loop binding corrections to the g factor, and we also investigate the radiative corrections in the limit of highly excited Rydberg S states with a long lifetime, where the g factor might be explored using a double resonance experiment.Comment: 13 pages, LaTeX; dedicated to Prof. H.-J. Kluge on the occasion of his 65th birthday, to appear in Int. J. Mass. Spectrometr

Techniques in Analytic Lamb Shift Calculations

Quantum electrodynamics has been the first theory to emerge from the ideas of regularization and renormalization, and the coupling of the fermions to the virtual excitations of the electromagnetic field. Today, bound-state quantum electrodynamics provides us with accurate theoretical predictions for the transition energies relevant to simple atomic systems, and steady theoretical progress relies on advances in calculational techniques, as well as numerical algorithms. In this brief review, we discuss one particular aspect connected with the recent progress: the evaluation of relativistic corrections to the one-loop bound-state self-energy in a hydrogenlike ion of low nuclear charge number, for excited non-S states, up to the order of alpha (Zalpha)^6 in units of the electron mass. A few details of calculations formerly reported in the literature are discussed, and results for 6F, 7F, 6G and 7G states are given.Comment: 16 pages, LaTe

Multi-wavelength analysis of high energy electrons in solar flares: a case study of August 20, 2002 flare

A multi-wavelength spatial and temporal analysis of solar high energy electrons is conducted using the August 20, 2002 flare of an unusually flat (gamma=1.8) hard X-ray spectrum. The flare is studied using RHESSI, Halpha, radio, TRACE, and MDI observations with advanced methods and techniques never previously applied in the solar flare context. A new method to account for X-ray Compton backscattering in the photosphere (photospheric albedo) has been used to deduce the primary X-ray flare spectra. The mean electron flux distribution has been analysed using both forward fitting and model independent inversion methods of spectral analysis. We show that the contribution of the photospheric albedo to the photon spectrum modifies the calculated mean electron flux distribution, mainly at energies below 100 keV. The positions of the Halpha emission and hard X-ray sources with respect to the current-free extrapolation of the MDI photospheric magnetic field and the characteristics of the radio emission provide evidence of the closed geometry of the magnetic field structure and the flare process in low altitude magnetic loops. In agreement with the predictions of some solar flare models, the hard X-ray sources are located on the external edges of the Halpha emission and show chromospheric plasma heated by the non-thermal electrons. The fast changes of Halpha intensities are located not only inside the hard X-ray sources, as expected if they are the signatures of the chromospheric response to the electron bombardment, but also away from them.Comment: 26 pages, 9 figures, accepted to Solar Physic

Cristal trapézoïdal en spectroscopie X d'implosion par laser

Elastically bent, trapezoidal crystals for Bragg diffraction of X-rays allow designing broadband spectrometers with flat field, normal incidence and high resolution. This is applied to study microballoon implosions driven by six laser beams.En courbant élastiquement un cristal trapézoïdal pour la diffraction de Bragg des rayons X, on réalise un spectrographe à champ plan, large bande et haute résolution, sous incidence normale. Grâce à lui, on étudie des implosions de microballons par un laser à six faisceaux

ÉTUDE EXPÉRIMENTALE DU CHAUFFAGE D'UN PLASMA AU MOYEN D'UN LASER DE PUISSANCE

La production et le chauffage par laser de plasmas de fusion nécessitent une bonne connaissance de l'interaction d'un faisceau laser de puissance avec un plasma dense. La densité électronique doit être proche de la densité critique pour laquelle la fréquence de l'onde est voisine de la fréquence plasma électronique. Nous décrivons quelques résultats obtenus dans ces conditions lorsque l'on focalise sur un plasma dense le faisceau d'un laser CO2. Le plasma cible a une densité de 8 à 9 × 1018 e/cm-3 et une température initiale de 10 eV. On étudie l'absorption et les variations de température du plasma en fonction du flux lumineux. Dans le régime des faibles flux (inférieurs à 1010 W/cm2), les résultats sont en accord avec le mécanisme classique de Bremsstrahlung inverse. Pour des flux plus élevés, les calculs montrent que, dans l'expérience proposée, l'absorption aura essentiellement pour origine les mécanismes anormaux dus aux instabilités paramétriques et que les conditions expérimentales se prêtent à l'observation des processus de rétrodiffusion prévus par Rosenbluth. La mise en évidence expérimentale se poursuit et nécessite le développement de lasers plus puissants qui sont actuellement en cours de réalisation.The realisation of laser produced and heated fusion plasma requires a good knowledge of the interaction of high power laser beam with plasmas near critical density where the plasma frequency is equal to the frequency of the laser. We present some results obtained under these conditions where a CO2 laser is focussed in a high, density plasma. The target plasma has an electronic number density of 8-9 × 1018 e/cm-3 and an initial temperature of 10 eV. We study absorption and temperature variation as a function of laser flux in the plasma. In the low flux regime (< 1010 W/cm2) the experimental results are in agreement with absorption due to Inverse Bremsstrahlung. For higher flux calculations show that in the proposed experiment absorption will be significant only in the case of an anomalous mecanism due to the onset of parametric instabilities induced by the laser. Experimental conditions will permit also the observation of back scattering as predicted by Rosenbluth when sufficiently high laser flux will be reached

INTERACTION AVEC UN CHAMP MAGNETIQUE D'UN PLASMA CREE PAR IRRADIATION LASER DE SOLIDE

Nous présentons les résultats de l'étude expérimentale de l'interaction avec un champ magnétique d'un plasma de laser. L'accord est assez bon avec les prévisions théoriques pour l'arrêt de l'expansion d'un plasma de conductivité électrique élevée.We present some results of the experimental investigation of the interaction with a magnetic field of a laser produced plasma. A reasonably good agreement is found with the theoretical prediction for a high conductivity expanding plasma

Corrélation entre le rayonnement x et l'émission d'ions rapides dans l'interaction laser CO2-cible

We present correlated measurements of the soft X ray continuum and of ion emission during the interaction of an intense CO2 laser with a slab of polyethylene, for laser fluxes varying from 109 W/cm 2 to 2 x 1012 W/cm2. These two émissions show that a superthermal component coexists with the main part of the plasma which remains thermal. Différent mechanisms for superthermal electron and fast ion production are discussed.Nous présentons des mesures corrélées du rayonnement X mou continu et de l'émission d'ions produits par l'interaction d'un faisceau laser à CO2 intense avec une cible plane de polyéthylène pour des flux lasers variant entre 199 et 2 x 1012 W/cm 2. Ces deux émissions montrent la présence d'une composante suprathermique qui coexiste avec l'ensemble du plasma qui reste thermique. Différents mécanismes de production d'électrons suprathermiques et ions rapides sont discutés