Coupling of (ultra-)relativistic atomic nuclei with photons

The coupling of photons with (ultra-) relativistic atomic nuclei is presented in two particular circumstances: very high electromagnetic fields and very short photon pulses. We consider a typical situation where the (bare) nuclei (fully stripped of electrons) are accelerated to energies ~1TeV per nucleon (according to the state of the art at LHC, for instance) and photon sources like petawatt lasers \simeq1eV -radiation (envisaged by ELI-NP project, for instance), or free-electron laser ~10keV -radiation, or synchrotron sources, etc. In these circumstances the nuclear scale energy can be attained, with very high field intensities. In particular, we analyse the nuclear transitions induced by the radiation, including both one- and two-photon processes, as well as the polarization-driven transitions which may lead to giant dipole resonances. The nuclear (electrical) polarization concept is introduced. It is shown that the perturbation theory for photo-nuclear reactions is applicable, although the field intensity is high, since the corresponding interaction energy is low and the interaction time (pulse duration) is short. It is also shown that the description of the giant nuclear dipole resonance requires the dynamics of the nuclear electrical polarization degrees of freedom.Comment: 15 page

RADIATION KINETICS AND CHEMICAL REACTIVITY OF BARRIER DISCHARGES IN HUMID ARGON

International audienceThe technique of spatially resolved cross-correlation spectroscopy was used to record two-dimensional luminosity distributions for the selected spectral bands of molecular nitrogen (λ=337.1 nm), OH-radical (λ=308 nm), and two spectral lines of excited Ar (λ=750.4 nm and λ=763.5 nm) emitted by the microdischarges of the barrier discharge in flowing humid argon at atmospheric pressure. Concentrations of two stable reaction products of H2O decomposition (H2 and O2) in argon plasma were determined experimentally as functions of humidity. Comparison of these results with the corresponding measurements of radiation kinetics permitted a detailed analysis of the influence of the discharge mechanism on its chemical reactivity in humid argon to be accomplished

Generation of Porous Alumina Layers in a Polydimethylsiloxane/Hydrogen Peroxide Medium on Aluminum Substrate in Corona Discharges

The porous alumina (Al2O3) layer obtained at the interface between polydimethylsiloxane/hydrogen peroxide medium and aluminum substrate under charged and neutral species injection produced in negative corona discharges in air at atmospheric pressure is analyzed by different methods in this paper. The scanning electron microscopy investigations showed the uniform distribution of the pores formed in the alumina layer and their columnar structures. Both energy dispersive X-ray spectroscopy (EDS) and X-ray photoelectron spectroscopy (XPS) measurements indicate that during the anodization process of the aluminum in the polydimethylsiloxane/hydrogen peroxide medium in corona discharge the incorporation of silicon in the structure of the alumina layer is possible

Design requirements for the Wide-field Infrared Transient Explorer (WINTER)

The Wide-field Infrared Transient Explorer (WINTER) is a 1x1 degree infrared survey telescope under devel- opment at MIT and Caltech, and slated for commissioning at Palomar Observatory in 2021. WINTER is a seeing-limited infrared time-domain survey and has two main science goals: (1) the discovery of IR kilonovae and r-process materials from binary neutron star mergers and (2) the study of general IR transients, including supernovae, tidal disruption events, and transiting exoplanets around low mass stars. We plan to meet these science goals with technologies that are relatively new to astrophysical research: hybridized InGaAs sensors as an alternative to traditional, but expensive, HgCdTe arrays and an IR-optimized 1-meter COTS telescope. To mitigate risk, optimize development efforts, and ensure that WINTER meets its science objectives, we use model-based systems engineering (MBSE) techniques commonly featured in aerospace engineering projects. Even as ground-based instrumentation projects grow in complexity, they do not often have the budget for a full-time systems engineer. We present one example of systems engineering for the ground-based WINTER project, featuring software tools that allow students or staff to learn the fundamentals of MBSE and capture the results in a formalized software interface. We focus on the top-level science requirements with a detailed example of how the goal of detecting kilonovae flows down to WINTER’s optical design. In particular, we discuss new methods for tolerance simulations, eliminating stray light, and maximizing image quality of a fly’s-eye design that slices the telescope’s focus onto 6 non-buttable, IR detectors. We also include a discussion of safety constraints for a robotic telescope

Coherent polarization driven by external electromagnetic fields

The coherent interaction of the electromagnetic radiation with an ensemble of polarizable, identical particles with two energy levels is investigated in the presence of external electromagnetic fields. The coupled non-linear equations of motion are solved in the stationary regime and in the limit of small coupling constants. It is shown that an external electromagnetic field may induce a macroscopic occupation of both the energy levels of the particles and the corresponding photon states, governed by a long-range order of the quantum phases of the internal motion (polarization) of the particles. A lasing effect is thereby obtained, controlled by the external field. Its main characteristics are estimated for typical atomic matter and atomic nuclei. For atomic matter the effect may be considerable (for usual external fields), while for atomic nuclei the effect is extremely small (practically insignificant), due to the great disparity in the coupling constants. In the absence of the external field, the solution, which is non-analytic in the coupling constant, corresponds to a second-order phase transition (super-radiance), which was previously investigated

Source compacte de rayons X

Des dispositifs miniatures peuvent produire des flashs intenses de rayons X. Ils mettent en jeu un faisceau d'électrons de haute densité de courant obtenu dans des décharges transitoires à cathode creuse. L'étude de ce faisceau a démontré son aptitude à être auto collimaté, permettant ainsi l'interaction ponctuelle avec une cible solide située a l'intérieur du tube à décharge. Nous présentons un dispositif compact utilisant un tube de quartz scellé rempli de Xe a 0,3 Torr. Des impulsions de haute tension (30 à 40 kV, 20 ns, 1-200 Hz) induisent par couplage capacitif la décharge transitoire et le faisceau d'électrons associé. Un aimant extérieur défléchit le faisceau vers la paroi interne du tube, côté anode, domant une source X quasi-ponctuelle qui est observée à travers la paroi (0.5 mm d'épaisseur) à la fois avec un scintillateur et un détecteur dosimétrique