Nuclear Instruments and Methods in Physics Research, Section A: Accelerators, Spectrometers, Detectors and Associated Equipment (2015)
© 2016. This paper describes the conceptual steps in reaching the design of the AWAKE experiment currently under construction at CERN. We start with an introduction to plasma wakefield acceleration and the motivation for using proton drivers. We then describe the self-modulation instability - a key to an early realization of the concept. This is then followed by the historical development of the experimental design, where the critical issues that arose and their solutions are described. We conclude with the design of the experiment as it is being realized at CERN and some words on the future outlook. A summary of the AWAKE design and construction status as presented in this conference is given in Gschwendtner et al. .
Novel Type of inertial actuator for satellite attitude control system basis on concept of reaction sphere-ELSA project
Annual Review of Earth and Planetary Sciences 24 (2015) 85-92
© Springer International Publishing Switzerland 2015.Magnetically levitated reaction sphere systems are considered as a new type of actuator dedicated for satellites ACS system. Inertial Attitude Control Systems used in spacecrafts, traditionally consists of one to four reaction wheels (RW) or control moment gyroscopes (CMG). In a principle, the attitude of the satellite can be changed by the reaction to the acceleration of the appropriate wheel. In practice, for optimization, redundancy purposes and ability to three-axis attitude stabilization, four or five wheels are common. Another approach, which states a general base for this work, assumes use of a single reaction sphere which can be accelerated in any direction instead of set of reaction wheels. The sphere can be accelerated in any direction by a three dimensional (3D) motor. Because of its unparalleled symmetry, a hollow sphere delivers constantly a maximum inertia independently of its current rotation axis. A solution investigated here consists in a rotating permanent magnet spherical rotor enclosed in a multi-coil stator. In opposition to conventional ball bearing momentum exchange devices, rotor in this solution levitates magnetically what results in absence of friction and increase of performance. The sphere can be accelerated in any direction by a three dimensional (3D) motor, making the three axes of the spacecraft controllable by just a single device. Furthermore, a hollow sphere has the natural optimal multi axis inertiato- mass and-volume ratios.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY 447 (2015) 2479-2496
Nature communications 6 (2015) 8905-
High-intensity lasers can be used to generate shockwaves, which have found applications in nuclear fusion, proton imaging, cancer therapies and materials science. Collisionless electrostatic shocks are one type of shockwave widely studied for applications involving ion acceleration. Here we show a novel mechanism for collisionless electrostatic shocks to heat small amounts of solid density matter to temperatures of ∼keV in tens of femtoseconds. Unusually, electrons play no direct role in the heating and it is the ions that determine the heating rate. Ions are heated due to an interplay between the electric field of the shock, the local density increase during the passage of the shock and collisions between different species of ion. In simulations, these factors combine to produce rapid, localized heating of the lighter ion species. Although the heated volume is modest, this would be one of the fastest heating mechanisms discovered if demonstrated in the laboratory.
Identification of the dominant ULF wave mode and generation mechanism for obliquely propagating waves in the Earth's foreshock
Geophysical Research Letters 42 (2015) 5109-5116
© 2015. American Geophysical Union. All Rights Reserved.We discuss mechanisms of the generation of ultralow frequency (ULF) upstream waves in the terrestrial foreshock that are essential for the acceleration of ions in space plasmas. The analysis is based on global hybrid kinetic simulations of the magnetosphere that provide realistic environment for the growth of the ULF waves in a quasi-radial configuration of the interplanetary magnetic field. We focus on a long-debated problem of the generation mechanism of oblique and parallel ULF waves and provide quantitative arguments in favor of the ion/ion cyclotron resonant instability. We also show that parallel propagating waves are predominantly generated in this configuration, but geometrical effects related to the phase space density in wave vector space lead to apparent predominance of obliquely propagating waves. Correspondence between the results outlined above and previously published experimental claims is thoroughly discussed and our results are shown to be consistent with spacecraft measurements. Key Points Parallel mode of ULF waves in the Earth's foreshock dominates over oblique mode Oblique mode is generated by oblique branch of the ion-ion resonant instability Kinetic simulations of foreshock ULF waves are consistent with observations.
The generation and amplification of intergalactic magnetic fields in analogue laboratory experiments with high power lasers
PHYSICS REPORTS-REVIEW SECTION OF PHYSICS LETTERS 601 (2015) 1-34
Self-consistent inclusion of classical large-angle Coulomb collisions in plasma Monte Carlo simulations
Journal of Computational Physics 299 (2015) C
PHYSICS OF EVOLVED STARS: A CONFERENCE DEDICATED TO THE MEMORY OF OLIVIER CHESNEAU 71-72 (2015) 81-86
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY 454 (2015) 1818-1839
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY 453 (2015) 849-867
PLASMA PHYSICS AND CONTROLLED FUSION 57 (2015) ARTN 014014
PHYSICAL REVIEW SPECIAL TOPICS-ACCELERATORS AND BEAMS 18 (2015) ARTN 081302
Journal of Plasma Physics 81 (2015)
© 2014 Cambridge University Press.A linearised kinetic equation describing electrostatic perturbations of a Maxwellian equilibrium in a weakly collisional plasma forced by a random source is considered. The problem is treated as a kinetic analogue of the Langevin equation and the corresponding fluctuation-dissipation relations are derived. The kinetic fluctuation-dissipation relation reduces to the standard fluid one in the regime where the Landau damping rate is small and the system has no real frequency; in this case the simplest possible Landau-fluid closure of the kinetic equation coincides with the standard Langevin equation. Phase mixing of density fluctuations and emergence of fine scales in velocity space is diagnosed as a constant flux of free energy in Hermite space; the fluctuation-dissipation relations for the perturbations of the distribution function are derived, in the form of a universal expression for the Hermite spectrum of the free energy. Finite-collisionality effects are included. This work is aimed at establishing the simplest fluctuation-dissipation relations for a kinetic plasma, clarifying the connection between Landau and Hermite-space formalisms, and setting a benchmark case for a study of phase mixing in turbulent plasmas.
JOURNAL OF PHYSICS B-ATOMIC MOLECULAR AND OPTICAL PHYSICS 48 (2015) ARTN 224004
Physical review. E, Statistical, nonlinear, and soft matter physics 92 (2015) 053106-
It is shown that the filamentation instability of relativistically intense laser pulses in plasmas can be mitigated in the case where the laser beam has an elliptically distributed beam profile. A high-power elliptical Gaussian laser beam would break up into a regular filamentation pattern-in contrast to the randomly distributed filaments of a circularly distributed laser beam-and much more laser power would be concentrated in the central region. A highly elliptically distributed laser beam experiences anisotropic self-focusing and diffraction processes in the plasma channel ensuring that the unstable diffractive rings of the circular case cannot be produced. The azimuthal modulational instability is thereby suppressed. These findings are verified by three-dimensional particle-in-cell simulations.
Editorial Special issue: Macroscopic randomness in astrophysical plasmas: The legacy and vision of Ya. B. Zeldovich
JOURNAL OF PLASMA PHYSICS 81 (2015) ARTN 391810403
Laboratory measurements of resistivity in warm dense plasmas relevant to the microphysics of brown dwarfs.
Nature communications 6 (2015) 8742-
Since the observation of the first brown dwarf in 1995, numerous studies have led to a better understanding of the structures of these objects. Here we present a method for studying material resistivity in warm dense plasmas in the laboratory, which we relate to the microphysics of brown dwarfs through viscosity and electron collisions. Here we use X-ray polarimetry to determine the resistivity of a sulphur-doped plastic target heated to Brown Dwarf conditions by an ultra-intense laser. The resistivity is determined by matching the plasma physics model to the atomic physics calculations of the measured large, positive, polarization. The inferred resistivity is larger than predicted using standard resistivity models, suggesting that these commonly used models will not adequately describe the resistivity of warm dense plasma related to the viscosity of brown dwarfs.
HIGH ENERGY DENSITY PHYSICS 17 (2015) 24-31