Ph. Martin

WHISPER, A Resonance Sounder and Wave Analyser: Performances and Perspectives for the Cluster Mission

The WHISPER sounder on the Cluster spacecraft is primarily designed to provide an absolute measurement of the total plasma density within the range 0.2–80 cm-3. This is achieved by means of a resonance sounding technique which has already proved successful in the regions to be explored. The wave analysis function of the instrument is provided by FFT calculation. Compared with the swept frequency wave analysis of previous sounders, this technique has several new capabilities. In particular, when used for natural wave measurements (which cover here the 2–80 kHz range), it offers a flexible trade-off between time and frequency resolutions. In the basic nominal operational mode, the density is measured every 28 s, the frequency and time resolution for the wave measurements are about 600 Hz and 2.2 s, respectively. Better resolutions can be obtained, especially when the spacecraft telemetry is in burst mode. Special attention has been paid to the coordination of WHISPER operations with the wave instruments, as well as with the low-energy particle counters. When operated from the multi-spacecraft Cluster, the WHISPER instrument is expected to contribute in particular to the study of plasma waves in the electron foreshock and solar wind, to investigations about small-scale structures via density and high-frequency emission signatures, and to the analysis of the non-thermal continuum in the magnetosphere.

Coulomb Systems at Low Density: A Review

Results on the correlations of low-density classical and quantum Coulomb systems at equilibrium in three dimensions are reviewed. The exponential decay of particle correlations in the classical Coulomb system, Debye–Hückel screening, is compared and contrasted with the quantum case, where strong arguments are presented for the absence of exponential screening. Results and techniques for detailed calculations that determine the asymptotic decay of correlations for quantum systems are discussed. Theorems on the existence of molecules in the Saha regime are reviewed. Finally, new combinatoric formulas for the coefficients of Mayer expansions are presented and their role in proofs of results on Debye–Hückel screening is discussed.

Elastic and inelastic scattering of carbon ions at intermediate energies

Abstract Elastic and inelastic scattering have been measured at E lab = 360 MeV and 1016 MeV for the 12 C + 12 C system, as well as elastic scattering for 13 C + 208 Pb at 390 MeV. An optical-model analysis is reported and nuclear surface transparency effects are discussed, together with the energy dependence of the nuclear potential. A DWBA analysis of data on the 2 + , 4.4 MeV state of 12 C is reported and trends in the energy dependence of mean-field excitations are deduced.

Sum rules for inhomogeneous Coulomb systems

Using the stationary equilibrium BBGKY hierarchy and some weak spatial decay properties of the correlations, we derive exact sum rules for the equilibrium distribution functions of ionic systems. Our results apply to both homogeneous and nonuniform systems. They show that when there is decay in such systems, then the total excess charge in the vicinity of a given number of fixed ions is zero, and that this excess charge has no dipole nor quadrupole moment. The implications for the static structure factor and for the dielectric tensor are discussed.

Exact statistical properties of the Burgers equation

The one-dimensional Burgers equation in the inviscid limit with white noise initial condition is revisited. The one- and two-point distributions of the Burgers field as well as the related distributions of shocks are obtained in closed analytical forms. In particular, the large distance behaviour of spatial correlations of the field is determined. Since higher-order distributions factorize in terms of the one- and two-point functions, our analysis provides an explicit and complete statistical description of this problem

Energy linearity and resolution of the ATLAS electromagnetic barrel calorimeter in an electron test-beam

A module of the ATLAS electromagnetic barrel liquid argon calorimeter was exposed to the CERN electron test-beam at the H8 beam line upgraded for precision momentum measurement. The available energies of the electron beam ranged from 10 to 245 GeV. The electron beam impinged at one point corresponding to a pseudo-rapidity of eta=0.687 and an azimuthal angle of phi=0.28 in the ATLAS coordinate system. A detailed study of several effects biasing the electron energy measurement allowed an energy reconstruction procedure to be developed that ensures a good linearity and a good resolution. Use is made of detailed Monte Carlo simulations based on Geant which describe the longitudinal and transverse shower profiles as well as the energy distributions. For electron energies between 15 GeV and 180 GeV the deviation of the measured incident electron energy over the beam energy is within 0.1%. The systematic uncertainty of the measurement is about 0.1% at low energies and negligible at high energies. The energy resolution is found to be about 10% sqrt(E) for the sampling term and about 0.2% for the local constant term.

Elastic and inelastic scattering of 1.03 GeV 12C projectiles

Abstract Elastic scattering cross sections of 86 MeV/N 12C ions on 12C, NATCa, 89Y and 208Pb targets has been measured together with inelastic scattering to the 4.4 MeV state of 12C. There is some indication for giant (quadrupole) resonance excitation in 40Ca. Optical model and DWBA analyses are reported. Nuclear transparency effect is discussed.

Conduction electrons in wide-bandgap oxides: a subpicosecond time-resolved optical study

Abstract Optical methods based on instantaneous measurements of the optical refractive index and of the absorption coefficient allow observation in real time, with a resolution of 10−13 s, of the evolution of an electron gas injected into the conduction band of a wide-bandgap insulator. In particular, the ultrafast dynamics of charge trapping, excitonic processes and point defect creation can be studied in this way.

Optical properties of relativistic plasma mirrors

The advent of ultrahigh-power femtosecond lasers creates a need for an entirely new class of optical components based on plasmas. The most promising of these are known as plasma mirrors, formed when an intense femtosecond laser ionizes a solid surface. These mirrors specularly reflect the main part of a laser pulse and can be used as active optical elements to manipulate its temporal and spatial properties. Unfortunately, the considerable pressures exerted by the laser can deform the mirror surface, unfavourably affecting the reflected beam and complicating, or even preventing, the use of plasma mirrors at ultrahigh intensities. Here we derive a simple analytical model of the basic physics involved in laser-induced deformation of a plasma mirror. We validate this model numerically and experimentally, and use it to show how such deformation might be mitigated by appropriate control of the laser phase.

A sum rule for an inhomogeneous electrolyte

We obtain a new sum rule for the density profile of an electrolyte in contact with a charged flat hard (nonconducting) wall. This, in turn, strongly implies that the decay of the pair correlation near the wall is not faster than (distance)−d−1, where d is the dimension of the system. (AIP)