scholarly journals Polar cap ion beams during periods of northward IMF: Cluster statistical results

2011 ◽  
Vol 29 (5) ◽  
pp. 771-787 ◽  
Author(s):  
R. Maggiolo ◽  
M. Echim ◽  
J. De Keyser ◽  
D. Fontaine ◽  
C. Jacquey ◽  
...  
Keyword(s):  
Electric Field ◽  
Ion Beam ◽  
Static Field ◽  
Ion Beams ◽  
Polar Cap ◽  
Isotropic Plasma ◽  
Polar Caps ◽  
Background Population ◽  
Auroral Arcs ◽  
Cluster Database

Abstract. Above the polar caps and during prolonged periods of northward IMF, the Cluster satellites detect upward accelerated ion beams with energies up to a few keV. They are associated with converging electric field structures indicating that the acceleration is caused by a quasi-static field-aligned electric field that can extend to altitudes higher than 7 RE (Maggiolo et al., 2006; Teste et al., 2007). Using the AMDA science analysis service provided by the Centre de Données de la Physique des Plasmas, we have been able to extract about 200 events of accelerated upgoing ion beams above the polar caps from the Cluster database. Most of these observations are taken at altitudes lower than 7 RE and in the Northern Hemisphere. We investigate the statistical properties of these ion beams. We analyze their geometry, the properties of the plasma populations and of the electric field inside and around the beams, as well as their dependence on solar wind and IMF conditions. We show that ~40 % of the ion beams are collocated with a relatively hot and isotropic plasma population. The density and temperature of the isotropic population are highly variable but suggest that this plasma originates from the plasma sheet. The ion beam properties do not change significantly when the isotropic, hot background population is present. Furthermore, during one single polar cap crossing by Cluster it is possible to detect upgoing ion beams both with and without an accompanying isotropic component. The analysis of the variation of the IMF BZ component prior to the detection of the beams indicates that the delay between a northward/southward turning of IMF and the appearance/disappearance of the beams is respectively ~2 h and 20 min. The observed electrodynamic characteristics of high altitude polar cap ion beams suggest that they are closely connected to polar cap auroral arcs. We discuss the implications of these Cluster observations above the polar cap on the magnetospheric dynamics and configuration during prolonged periods of northward IMF.

scholarly journals A multi-satellite study of accelerated ionospheric ion beams above the polar cap

2006 ◽  
Vol 24 (6) ◽  
pp. 1665-1684 ◽  
Author(s):  
R. Maggiolo ◽  
J. A. Sauvaud ◽  
D. Fontaine ◽  
A. Teste ◽  
E. Grigorenko ◽  
...  
Keyword(s):  
Electric Field ◽  
Potential Drop ◽  
Auroral Zone ◽  
Ion Beams ◽  
Distribution Functions ◽  
Convection Velocity ◽  
Polar Cap ◽  
Ion Energy ◽  
Polar Cusp ◽  
Oxygen Ions

Abstract. This paper presents a study of nearly field-aligned outflowing ion beams observed on the Cluster satellites over the polar cap. Data are taken at geocentric radial distances of the order of 5–9 RE. The distinction is made between ion beams originating from the polar cusp/cleft and beams accelerated almost along the magnetic field line passing by the spacecraft. Polar cusp beams are characterized by nearly field-aligned proton and oxygen ions with an energy ratio EO+ / EH+, of the order of 3 to 4, due to the ion energy repartition inside the source and to the latitudinal extension of the source. Rapid variations in the outflowing ion energy are linked with pulses/modifications of the convection electric field. Cluster data allow one to show that these perturbations of the convection velocity and the associated ion structures propagate at the convection velocity. In contrast, polar cap local ion beams are characterized by field-aligned proton and oxygen ions with similar energies. These beams show the typical inverted V structures usually observed in the auroral zone and are associated with a quasi-static converging electric field indicative of a field-aligned electric field. The field-aligned potential drop fits well the ion energy profile. The simultaneous observation of precipitating electrons and upflowing ions of similar energies at the Cluster orbit indicates that the spacecraft are crossing the mid-altitude part of the acceleration region. In the polar cap, the parallel electric field can thus extend to altitudes higher than 5 Earth radii. A detailed analysis of the distribution functions shows that the ions are heated during their parallel acceleration and that energy is exchanged between H+ and O+. Furthermore, intense electrostatic waves are observed simultaneously. These observations could be due to an ion-ion two-stream instability.

scholarly journals Polar cap arcs from the magnetosphere to the ionosphere: kinetic modelling and observations by Cluster and TIMED

2012 ◽  
Vol 30 (2) ◽  
pp. 283-302 ◽  
Author(s):  
R. Maggiolo ◽  
M. Echim ◽  
C. Simon Wedlund ◽  
Y. Zhang ◽  
D. Fontaine ◽  
...  
Keyword(s):  
Energy Spectrum ◽  
Electric Field ◽  
Large Scale ◽  
Kinetic Modelling ◽  
Ion Beam ◽  
Potential Drop ◽  
Coupling Model ◽  
Optical Observations ◽  
Topside Ionosphere ◽  
Polar Cap

Abstract. On 1 April 2004 the GUVI imager onboard the TIMED spacecraft spots an isolated and elongated polar cap arc. About 20 min later, the Cluster satellites detect an isolated upflowing ion beam above the polar cap. Cluster observations show that the ions are accelerated upward by a quasi-stationary electric field. The field-aligned potential drop is estimated to about 700 V and the upflowing ions are accompanied by a tenuous population of isotropic protons with a temperature of about 500 eV. The magnetic footpoints of the ion outflows observed by Cluster are situated in the prolongation of the polar cap arc observed by TIMED GUVI. The upflowing ion beam and the polar cap arc may be different signatures of the same phenomenon, as suggested by a recent statistical study of polar cap ion beams using Cluster data. We use Cluster observations at high altitude as input to a quasi-stationary magnetosphere-ionosphere (MI) coupling model. Using a Knight-type current-voltage relationship and the current continuity at the topside ionosphere, the model computes the energy spectrum of precipitating electrons at the top of the ionosphere corresponding to the generator electric field observed by Cluster. The MI coupling model provides a field-aligned potential drop in agreement with Cluster observations of upflowing ions and a spatial scale of the polar cap arc consistent with the optical observations by TIMED. The computed energy spectrum of the precipitating electrons is used as input to the Trans4 ionospheric transport code. This 1-D model, based on Boltzmann's kinetic formalism, takes into account ionospheric processes such as photoionization and electron/proton precipitation, and computes the optical and UV emissions due to precipitating electrons. The emission rates provided by the Trans4 code are compared to the optical observations by TIMED. They are similar in size and intensity. Data and modelling results are consistent with the scenario of quasi-static acceleration of electrons that generate a polar cap arc as they precipitate in the ionosphere. The detailed observations of the acceleration region by Cluster and the large scale image of the polar cap arc provided by TIMED are two different features of the same phenomenon. Combined together, they bring new light on the configuration of the high-latitude magnetosphere during prolonged periods of Northward IMF. Possible implications of the modelling results for optical observations of polar cap arcs are also discussed.

scholarly journals Invariability of relationship between the polar cap magnetic activity and geoeffective interplanetary electric field

2011 ◽  
Vol 29 (8) ◽  
pp. 1479-1489 ◽  
Author(s):  
O. A. Troshichev ◽  
N. A. Podorozhkina ◽  
A. S. Janzhura
Keyword(s):  
Solar Wind ◽  
Solar Activity ◽  
Electric Field ◽  
Solar Minimum ◽  
Solar Maximum ◽  
Magnetic Activity ◽  
Polar Cap ◽  
Polar Caps ◽  
The Relationship ◽  
Wind Energy Input

Abstract. The PC (polar cap) index characterizing the solar wind energy input into the magnetosphere is calculated with use of parameters α, β, and φ, determining the relationship between the interplanetary electric field (EKL) and the value of magnetic activity δF in the polar caps. These parameters were noted as valid for large and small EKL values, and as a result the suggestion was made (Troshichev et al., 2006) that the parameters should remain invariant irrespective of solar activity. To verify this suggestion, the independent sets of calibration parameters α, β, and φ were derived separately for the solar maximum (1998–2001) and solar minimum (1997, 2007–2009) epochs, with a proper choice of a quiet daily variation (QDC) as a level of reference for the polar cap magnetic activity value. The results presented in this paper demonstrate that parameters α, β, and φ, derived under conditions of solar maximum and solar minimum, are indeed in general conformity and provide consistent (within 10 % uncertainty) estimations of the PC index. It means that relationship between the geoeffective solar wind variations and the polar cap magnetic activity responding to these variations remains invariant irrespective of solar activity. The conclusion is made that parameters α, β, and φ derived in AARI#3 version for complete cycle of solar activity (1995–2005) can be regarded as forever valid.

Preparation of TEM samples by focused ion beams

1995 ◽  
Vol 53 ◽  
pp. 518-519
Author(s):  
John F. Walker ◽  
J C Reiner ◽  
C Solenthaler
Keyword(s):  
Integrated Circuit ◽  
Polycrystalline Silicon ◽  
Field Effect Transistor ◽  
High Spatial Resolution ◽  
Ion Beam ◽  
Ion Beams ◽  
Focused Ion Beams ◽  
Precise Location ◽  
Effect Transistor ◽  
Circuit Technology

The high spatial resolution available from TEM can be used with great advantage in the field of microelectronics to identify problems associated with the continually shrinking geometries of integrated circuit technology. In many cases the location of the problem can be the most problematic element of sample preparation. Focused ion beams (FIB) have previously been used to prepare TEM specimens, but not including using the ion beam imaging capabilities to locate a buried feature of interest. Here we describe how a defect has been located using the ability of a FIB to both mill a section and to search for a defect whose precise location is unknown. The defect is known from electrical leakage measurements to be a break in the gate oxide of a field effect transistor. The gate is a square of polycrystalline silicon, approximately 1μm×1μm, on a silicon dioxide barrier which is about 17nm thick. The break in the oxide can occur anywhere within that square and is expected to be less than 100nm in diameter.

Atomic force microscopy (AFM) of the topography of silicon surfaces exposed to ion beams

1992 ◽  
Vol 50 (2) ◽  
pp. 1132-1133
Author(s):  
Mark Denker ◽  
Jennifer Wall ◽  
Mark Ray ◽  
Richard Linton
Keyword(s):  
Secondary Ion Mass Spectrometry ◽  
Incidence Angle ◽  
Ion Beam ◽  
Depth Profiling ◽  
Depth Resolution ◽  
Ion Beams ◽  
Scanning Tunneling ◽  
Tunneling Microscopy ◽  
Trace Impurities ◽  
Energy Dose

Reactive ion beams such as O2+ and Cs+ are used in Secondary Ion Mass Spectrometry (SIMS) to analyze solids for trace impurities. Primary beam properties such as energy, dose, and incidence angle can be systematically varied to optimize depth resolution versus sensitivity tradeoffs for a given SIMS depth profiling application. However, it is generally observed that the sputtering process causes surface roughening, typically represented by nanometer-sized features such as cones, pits, pyramids, and ripples. A roughened surface will degrade the depth resolution of the SIMS data. The purpose of this study is to examine the relationship of the roughness of the surface to the primary ion beam energy, dose, and incidence angle. AFM offers the ability to quantitatively probe this surface roughness. For the initial investigations, the sample chosen was <100> silicon, and the ion beam was O2+.Work to date by other researchers typically employed Scanning Tunneling Microscopy (STM) to probe the surface topography.

Chemical Precursors for GaAs Etching with low Energy ion Beams: Chlorine adsorption on GaAs(100)

1991 ◽  
Vol 223 ◽  
Author(s):  
Richard B. Jackman ◽  
Glenn C. Tyrrell ◽  
Duncan Marshall ◽  
Catherine L. French ◽  
John S. Foord
Keyword(s):  
Ion Beam ◽  
Ion Beams ◽  
Low Energy ◽  
Ion Beam Etching ◽  
Chlorine Adsorption

ABSTRACTThis paper addresses the issue of chlorine adsorption on GaAs(100) with respect to the mechanisms of thermal and ion-enhanced etching. The use of halogenated precursors eg. dichloroethane is also discussed in regard to chemically assisted ion beam etching (CAIBE).

scholarly journals Yttrium Oxide Freeze-Casts: Target Materials for Radioactive Ion Beams

Materials ◽  
2021 ◽  
Vol 14 (11) ◽  
pp. 2864
Author(s):  
Eva Kröll ◽  
Miriana Vadalà ◽  
Juliana Schell ◽  
Simon Stegemann ◽  
Jochen Ballof ◽  
...  
Keyword(s):  
Pore Structure ◽  
Yttrium Oxide ◽  
Ion Beam ◽  
Isotope Separation ◽  
Target Material ◽  
Ion Beams ◽  
Radioactive Isotopes ◽  
Solid Loading ◽  
Radioactive Ion Beams ◽  
Freeze Casting

Highly porous yttrium oxide is fabricated as ion beam target material in order to produce radioactive ion beams via the Isotope Separation On Line (ISOL) method. Freeze casting allows the formation of an aligned pore structure in these target materials to improve the isotope release. Aqueous suspensions containing a solid loading of 10, 15, and 20 vol% were solidified with a unidirectional freeze-casting setup. The pore size and pore structure of the yttrium oxide freeze-casts are highly affected by the amount of solid loading. The porosity ranges from 72 to 84% and the crosslinking between the aligned channels increases with increasing solid loading. Thermal aging of the final target materials shows that an operation temperature of 1400 °C for 96 h has no significant effect on the microstructure. Thermo-mechanical calculation results, based on a FLUKA simulation, are compared to measured compressive strength and forecast the mechanical integrity of the target materials during operation. Even though they were developed for the particular purpose of the production of short-lived radioactive isotopes, the yttria freeze-cast scaffolds can serve multiple other purposes, such as catalyst support frameworks or high-temperature fume filters.

scholarly journals Production of ion beams in high-power laser–plasma interactions and their applications

2004 ◽  
Vol 22 (1) ◽  
pp. 19-24 ◽  
Author(s):  
F. PEGORARO ◽  
S. ATZENI ◽  
M. BORGHESI ◽  
S. BULANOV ◽  
T. ESIRKEPOV ◽  
...  
Keyword(s):  
Laser Pulse ◽  
Medical Physics ◽  
Ion Beam ◽  
Laser Pulses ◽  
Ion Beams ◽  
Laser Plasma Interactions ◽  
Physical Mechanisms ◽  
Short Laser Pulses ◽  
Laser Pulse Intensity ◽  
Target Design

Energetic ion beams are produced during the interaction of ultrahigh-intensity, short laser pulses with plasmas. These laser-produced ion beams have important applications ranging from the fast ignition of thermonuclear targets to proton imaging, deep proton lithography, medical physics, and injectors for conventional accelerators. Although the basic physical mechanisms of ion beam generation in the plasma produced by the laser pulse interaction with the target are common to all these applications, each application requires a specific optimization of the ion beam properties, that is, an appropriate choice of the target design and of the laser pulse intensity, shape, and duration.

Applications of Energy Beams in Material and Device Processing

1983 ◽  
Vol 23 ◽  
Author(s):  
G.J. Galvin ◽  
L.S. Hung ◽  
J.W. Mayer ◽  
M. Nastasi
Keyword(s):  
Ion Beam ◽  
High Energy ◽  
Ion Beams ◽  
Traditional Role ◽  
Near Surface ◽  
Device Processing ◽  
Composition Modification ◽  
Directed Energy ◽  
Transistor Fabrication

ABSTRACTEnergetic ion beams used outside the traditional role of ion implantation are considered for semiconductor applications involving interface modification for self-aligned silicide contacts, composition modification for formation of buried oxide layers in Si on insulator structures and reduced disorder in high energy ion beam annealing for buried collectors in transistor fabrication. In metals, aside from their use in modification of the composition of near surface regions, energetic ion beams are being investigated for structural modification in crystalline to amorphous transitions. Pulsed beams of photons and electrons are used as directed energy sources in rapid solidification. Here, we consider the role of temperature gradients and impurities in epitaxial growth of silicon.

scholarly journals Surface Analysis by MeV Ion Beams and Microscopy

2009 ◽  
Vol 15 (S3) ◽  
pp. 87-88
Author(s):  
José A. R. Pacheco de Carvalho ◽  
Cláudia F. F. P. R. Pacheco ◽  
António D. Reis
Keyword(s):  
Surface Analysis ◽  
Nuclear Reactions ◽  
Ion Beam ◽  
Ion Beams ◽  
Analysis Method ◽  
Analysis Techniques ◽  
Target Composition ◽  
Nuclear Techniques ◽  
Surface Analysis Techniques ◽  
Wide Range

AbstractMaterial analysis, specially surface analysis of materials, has been increasingly important. A wide range of surface analysis techniques is available. The techniques are, generally, complementary. There are nuclear and non-nuclear techniques, e.g. microscopy. Nuclear techniques, which are nondestructive, permit analysis for a few microns near the surface. They have been applied to areas such as scientific, technologic, industry, arts and medicine, using MeV ion beams. Nuclear reactions permit to achieve high sensitivities for detection of light elements in heavy substrates and also discrimination of isotopes. We use ion-ion nuclear reactions, elastic scattering and the energy analysis method, where an energy spectrum is obtained of ions from the target for a chosen energy of the incident ion beam. The target composition and concentration profile information contained in the spectrum is computationally obtained through a computer program that has been developed for predicting such energy spectra. Predicted spectra obtained for variations of target parameters are compared with experimental data, giving that information. SEM and TEM are also used.

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