36086311
Space charge neutralization of high brightness ion beams
Experiments are under way to investigate the extent to which various space charge neutralization methods will allow one to exceed the space charge limited transport condition. Imperfect spatial neutralization will result in nonlinear fields which have the effect of diluting the phase space density of the beam, and thereby increasing the emittance. These experiments give quantitative results on the problem of vacuum neutralization in the final focus/transport for a heavy ion fusion reactor.
56163569
IPHI, the Saclay high-intensity proton injector project
High-power accelerators are being studied for several projects based on high-flux neutron sources driven by proton or deuteron beams. Since the front end is the most critical part of such accelerators, it has been decided to build a high-intensity proton injector (IPHI) designed to accelerate a CW 100 mA beam up to 11 MeV. The aim is to validate design codes, test technical choices, demonstrate operational reliability and measure the beam parameters in order to optimize the high-energy part of the accelerator. The design chosen for IPHI (ECR source, RFQ, DTL and diagnostic line) and the construction schedule are presented.
126312211
Status Report on Acceleration of Polarized Protons and Deuterons of the SATURNE Linac
119061387
Numerical Simulations of Space Charge Compensation in Intense nonrelativistic Proton Beams from a Physical Model
15641163
Highlights of Accelerator Activities in France on behalf of the Accelerator Division of the French Physics Society
The French Physics Society is an association the purpose of which is to promote physics and physicists. In this context, the accelerator physics and associated technology division is in charge of the promotion of accelerator activities in France. This paper presents the missions and actions of the division, highlighting those concerning young scientists. A brief presentation of the laboratories, institutes or facilities who are the main actors in the field will then be given. Significant projects which are underway or planned will be described, including medical applications. The major contribution of France to international projects will then be introduced. Finally the cultural and technical relations between industry and laboratories will be discussed.
59398810
Optical and infrared observations of the young SMC “ blob ” N 26 and its environment ?
1 LERMA, UMR 8112 du CNRS, Observatoire de Paris, 92195 Meudon, France e-mail: gerard.testor@obspm.fr 2 Department of Astronomy, University of Virginia , PO Box 400325, Charlottesville, VA 22904, USA 3 Max-Planck-Institut fur Radioastronomie, D-53121 Bonn, Germany 4 Université de Cergy-Pontoise, 95031 Cergy Cedex, France 5 The Johns Hopkins University, Department of Physics and Astronomy, 366 Bloomberg Center, 3400 N. Charles Street, Baltimore, MD 21218, USA 6 Space Science Institute, 4750 Walnut St. Suite 205, Boulder, CO 80301, USA
119306237
Half a Century of Kinetic Solar Wind Models
I outline the development of four generations of kinetic models, starting with Chamberlain’s solar breeze exospheric model. It is shown why this first kinetic model did not give apposite supersonic evaporation velocities, like early hydrodynamic models of the solar wind. When a self‐consistent polarization electric potential distribution is used in the coronal plasma, instead of the Pannekoek‐Rosseland’s one, supersonic bulk velocities are readily obtained in the second generation of kinetic models. It is outlined how the third and fourth generations of these models have improved the agreement with observations of slow and fast speed solar wind streams.
118184102
Determination of coronal temperatures from electron density profiles
The most popular method for determining coronal temperatures is the scale-height-method (shm). It is based on electron density profiles inferred from White Light (WL) brightness measurements of the corona during solar eclipses. This method has been applied to several published coronal electron density models. The calculated temperature distributions reach a maximum at r > 1.3 RS, and therefore do not satisfy one of the conditions for applying the shm method. Another method is the hydrostatic equilibrium method (hst), which enables coronal temperature distributions to be determined, providing solutions to the hydrostatic equilibrium equation. The temperature maximas using the hst method are almost equal to those obtained using the shm method, but the temperature peak is always at significantly lower altitude when the hst-method is used than when the shm-method is used. A third and more recently developed method, dyn, can be used for the same published electron density profiles. The temperature distributions obtained using the dyn method are regular solutions of the hydrodynamic equations. They depend on the expansion velocity of the coronal plasma considered as a free input parameter in the calculations. At the base of the solar corona, where the coronal bulk velocity is small (subsonic), the dyn and hst methods give similar temperature values. Larger differences are found at higher altitudes where the expansion velocity approaches and exceeds the velocity of sound. This paper shows also the effects of the flow tube geometry and ion temperatures on the electron temperature distributions. The dyn method is a generalization of the hst method, where the electron temperature distribution tends to zero at infinite radial distances. It is a new diagnostic tool for determining from WL coronal observations the range of radial distances where the coronal heating rate is at its maximum.
116897797
What Happens When the Geomagnetic Field Reverses
During geomagnetic field reversals the radiation belt high-energy proton populations become depleted. Their energy spectra become softer, with the trapped particles of highest energies being lost first, and eventually recovering after a field reversal. The radiation belts rebuild in a dynamical way with the energy spectra flattening on the average during the course of many millennia, but without ever reaching complete steady state equilibrium between successive geomagnetic storm events determined by southward turnings of the IMF orientation. Considering that the entry of galactic cosmic rays and the solar energetic particles with energies above a given threshold are strongly controlled by the intensity of the northward component of the interplanetary magnetic field, we speculate that at earlier epochs when the geomagnetic dipole was reversed, the entry of these energetic particles into the geomagnetic field was facilitated when the interplanetary magnetic field was directed northward. Unlike in other complementary work where intensive numerical simulations have been used, our demonstration is based on a simple analytical extension of Stormer's theory. The access of GCR and SEP beyond geomagnetic cut-off latitudes is enhanced during epochs when the Earth's magnetic dipole is reduced, as already demonstrated earlier.
118409391
A Review on Solar Wind Modeling: Kinetic and Fluid Aspects
The paper reviews the main advantages and limitations of the kinetic exospheric and fluid models of the solar wind (SW). The general theoretical background is outlined: the Boltzmann and Fokker–Planck equations, the Liouville and Vlasov equations, the plasma transport equations derived from an “equation of change”. The paper provides a brief history of the solar wind modeling. It discusses the hydrostatic model imagined by Chapman, the first supersonic hydrodynamic models published by Parker and the first generation subsonic kinetic model proposed by Chamberlain. It is shown that a correct estimation of the electric field, as in the second generation kinetic exospheric models developed by Lemaire and Scherer, provides a supersonic expansion of the corona, reconciling the hydrodynamic and the kinetic approach. The modern developments are also reviewed emphasizing the characteristics of several generations of kinetic exospheric and multi-fluid models. The third generation kinetic exospheric models consider kappa velocity distribution function (VDF) instead of a Maxwellian at the exobase and in addition they treat a non-monotonic variation of the electric potential with the radial distance; the fourth generation exospheric models include Coulomb collisions based on the Fokker–Planck collision term. Multi-fluid models of the solar wind provide a coarse grained description of the system and reproduce with success the spatio-temporal variation of SW macroscopic properties (density, bulk velocity). The main categories of multi-fluid SW models are reviewed: the 5-moment, or Euler, models, originally proposed by Parker to describe the supersonic SW expansion; the 8-moment and 16-moment fluid models, the gyrotropic approach with improved collision terms as well as the gyrotropic models based on observed VDFs. The outstanding problem of collisions, including the long range Coulomb encounters, is also discussed, both in the kinetic and multi-fluid context. Although for decades the two approaches have been seen as opposed, in this paper we emphasize their complementarity. The review of the kinetic and fluid models of the solar wind contributes also to a better evaluation of the open questions still existent in SW modeling and suggests possible future developments.