Extraction of volume produced H- or D- ions from a sheet plasma, 2

International Nuclear Information System (INIS)

Uramoto, Joshin.

1984-02-01

A development to large area H - or D - ion source is tried by using three extraction electrodes: The first electrode bias voltage is set near the wall potential (floating), the second electrode is set near 13 % of main extraction voltage and the third electrode is the main acceleration electrode. An ion current of 13 mA (3.3 mA/cm 2 ) for H - or 11 mA (2.8 mA/ cm 2 ) for D - at 3 KeV is extracted from 9 apertures of 6 mm phi in 4 cm 2 outside of the sheet plasma (14 cm wide and 1.0 cm thick) under a pressure of 7.7 x 10 -4 H2 or D2 gas and a weak magnetic field 50 gauss. Then, it is noted that the corresponding electron current is suppressed below 1/10 of the H - or D - ion current. (author)

MHD Ballooning Instability in the Plasma Sheet

International Nuclear Information System (INIS)

Cheng, C.Z.; Zaharia, S.

2003-01-01

Based on the ideal-MHD model the stability of ballooning modes is investigated by employing realistic 3D magnetospheric equilibria, in particular for the substorm growth phase. Previous MHD ballooning stability calculations making use of approximations on the plasma compressibility can give rise to erroneous conclusions. Our results show that without making approximations on the plasma compressibility the MHD ballooning modes are unstable for the entire plasma sheet where beta (sub)eq is greater than or equal to 1, and the most unstable modes are located in the strong cross-tail current sheet region in the near-Earth plasma sheet, which maps to the initial brightening location of the breakup arc in the ionosphere. However, the MHD beq threshold is too low in comparison with observations by AMPTE/CCE at X = -(8 - 9)R(sub)E, which show that a low-frequency instability is excited only when beq increases over 50. The difficulty is mitigated by considering the kinetic effects of ion gyrorad ii and trapped electron dynamics, which can greatly increase the stabilizing effects of field line tension and thus enhance the beta(sub)eq threshold [Cheng and Lui, 1998]. The consequence is to reduce the equatorial region of the unstable ballooning modes to the strong cross-tail current sheet region where the free energy associated with the plasma pressure gradient and magnetic field curvature is maximum

XUV laser-produced plasma sheet beam and microwave agile mirror

International Nuclear Information System (INIS)

Shen, W.; Scharer, J.E.; Porter, B.; Lam, N.T.

1994-01-01

An excimer-laser (λ = 193 nm) produced plasma in an organic gas (TMAE) has been generated and studied. These studies have determined the ion-electron recombination coefficient and the photon absorption cross-section, of the neutral gas. The dependences of wave transmission, reflection and absorption on plasma density are obtained. A new optical system with an array of cylindrical XUV coated lenses has been implemented to form a plasma sheet to study its usage as agile mirror microwave reflector. The lens system expands the incident laser beam in X direction and compresses it in Y direction to form a sheet beam. The expanded beam then passes through a vacuum chamber filled with TMAE at 50--500 nTorr to produce the plasma sheet. Space-time measurements of the plasma density and temperature as measured by a Langmuir probe are presented. XUV optical measurements of the laser beam as measured by a photodiode are presented. Initial experiments have generated a plasma sheet of 5--10 mm x 11 cm with peak plasma density of 5 x 10 13 cm -3 . A microwave source will be utilized to study the agile mirror character of the plasma sheet. Modeling of the microwave reflection from the plasma profile will also be discussed

A feature of negative hydrogen ion production in the Uramoto-type sheet plasma

Energy Technology Data Exchange (ETDEWEB)

Jimbo, Kouichi [Kyoto Univ., Uji (Japan). Inst. of Atomic Energy

1997-02-01

It seems that negative hydrogen ions H{sup -} are formed directly from atomic hydrogens H. When the chamber was biased more negative against the anode potential at constant are power, forming a much deeper electrostatic well in the Uramoto-type sheet plasma negative ion source, more negative hydrogen ion currents were extracted. The chamber potential V{sub B} was biased down to -100V in the 150V discharge. The negative ion current J{sup -} was evaluated by the JAERI-probe measurement. J{sup -} increases linearly with the chamber current I{sub B}. The largest J{sup -} value was obtained at absolute value of |V{sub prob,f}|=15V and absolute value of |V{sub B}|=100V; the discharge was not operated for absolute value of |V{sub B}|>100V. We speculate the following collisional (three-body) electron attachment to H as a possible production process for H{sup -}; e+e+H{yields}e+H{sup -}. This process may explain the linear increase of J{sup -} with absolute value of |V{sub prob,f}|. (S.Y.)

The lobe to plasma sheet boundary layer transition: Theory and observations

International Nuclear Information System (INIS)

Schriver, D.; Ashour-Abdalla, M.; Treumann, R.; Nakamura, M.; Kistler, L.M.

1990-01-01

The lobe and the plasma sheet boundary layer in the Earth's magnetotail are regions of different plasma conditions and share a common interface. The transition from the lobe to the plasma sheet boundary layer is examined here using AMPTE/IRM data. When the satellite crossed from the lobe to the plasma sheet boundary layer, intense narrow banded wave bursts at 1 kHz were observed an d then broadband electrostatic noise (BEN) immediately followed. Simultaneous with the onset of BEN, high energy earthward streaming proton beams at > 40 keV (> 2,700 km/s) were detected. These results are used as input into a numerical simulation to study ion beam instabilities in the PSBL

Distribution of energetic oxygen and hydrogen in the near-Earth plasma sheet

Science.gov (United States)

Kronberg, E. A.; Grigorenko, E. E.; Haaland, S. E.; Daly, P. W.; Delcourt, D. C.; Luo, H.; Kistler, L. M.; Dandouras, I.

2015-05-01

The spatial distributions of different ion species are useful indicators for plasma sheet dynamics. In this statistical study based on 7 years of Cluster observations, we establish the spatial distributions of oxygen ions and protons at energies from 274 to 955 keV, depending on geomagnetic and solar wind (SW) conditions. Compared with protons, the distribution of energetic oxygen has stronger dawn-dusk asymmetry in response to changes in the geomagnetic activity. When the interplanetary magnetic field (IMF) is directed southward, the oxygen ions show significant acceleration in the tail plasma sheet. Changes in the SW dynamic pressure (Pdyn) affect the oxygen and proton intensities in the same way. The energetic protons show significant intensity increases at the near-Earth duskside during disturbed geomagnetic conditions, enhanced SW Pdyn, and southward IMF, implying there location of effective inductive acceleration mechanisms and a strong duskward drift due to the increase of the magnetic field gradient in the near-Earth tail. Higher losses of energetic ions are observed in the dayside plasma sheet under disturbed geomagnetic conditions and enhanced SW Pdyn. These observations are in agreement with theoretical models.

Singular Sheet Etching of Graphene with Oxygen Plasma

Institute of Scientific and Technical Information of China (English)

Haider Al-Mumen; Fubo Rao; Wen Li; Lixin Dong

2014-01-01

This paper reports a simple and controllable post-synthesis method for engineering the number of graphene layers based on oxygen plasma etching. Singular sheet etching(SSE) of graphene was achieved with the optimum process duration of 38 seconds. As a demonstration of this SSE process, monolayer graphene films were produced from bilayer graphenes. Experimental investigations verified that the oxygen plasma etching removes a single layer graphene sheet in an anisotropic fashion rather than anisotropic mode. In addition,etching via the oxygen plasma at the ground electrodes introduced fewer defects to the bottom graphene layer compared with the conventional oxygen reactive ion etching using the powered electrodes. Such defects can further be reduced with an effective annealing treatment in an argon environment at 900-1000?C. These results demonstrate that our developed SSE method has enabled a microelectronics manufacturing compatible way for single sheet precision subtraction of graphene layers and a potential technique for producing large size graphenes with high yield from multilayer graphite materials.

Singular Sheet Etching of Graphene with Oxygen Plasma

Institute of Scientific and Technical Information of China (English)

Haider Al-Mumen; Fubo Rao; Wen Li; Lixin Dong

2014-01-01

This paper reports a simple and controllable post-synthesis method for engineering the number of graphene layers based on oxygen plasma etching. Singular sheet etching (SSE) of graphene was achieved with the optimum process duration of 38 seconds. As a demonstration of this SSE process, monolayer graphene films were produced from bilayer graphenes. Experimental investigations verified that the oxygen plasma etching removes a single layer graphene sheet in an anisotropic fashion rather than anisotropic mode. In addition, etching via the oxygen plasma at the ground electrodes introduced fewer defects to the bottom graphene layer compared with the conventional oxygen reactive ion etching using the powered electrodes. Such defects can further be reduced with an effective annealing treatment in an argon environment at 900-1000◦C. These results demonstrate that our developed SSE method has enabled a microelectronics manufacturing compatible way for single sheet precision subtraction of graphene layers and a potential technique for producing large size graphenes with high yield from multilayer graphite materials.

Acceleration of O+ from the cusp to the plasma sheet

Science.gov (United States)

Liao, J.; Kistler, L. M.; Mouikis, C. G.; Klecker, B.; Dandouras, I.

2015-02-01

Heavy ions from the ionosphere that are accelerated in the cusp/cleft have been identified as a direct source for the hot plasma in the plasma sheet. However, the details of the acceleration and transport that transforms the originally cold ions into the hot plasma sheet population are not fully understood. The polar orbit of the Cluster satellites covers the main transport path of the O+ from the cusp to the plasma sheet, so Cluster is ideal for tracking its velocity changes. However, because the cusp outflow is dispersed according to its velocity as it is transported to the tail, due to the velocity filter effect, the observed changes in beam velocity over the Cluster orbit may simply be the result of the spacecraft accessing different spatial regions and not necessarily evidence of acceleration. Using the Cluster Ion Spectrometry/Composition Distribution Function instrument onboard Cluster, we compare the distribution function of streaming O+ in the tail lobes with the initial distribution function observed over the cusp and reveal that the observations of energetic streaming O+ in the lobes around -20 RE are predominantly due to the velocity filter effect during nonstorm times. During storm times, the cusp distribution is further accelerated. In the plasma sheet boundary layer, however, the average O+ distribution function is above the upper range of the outflow distributions at the same velocity during both storm and nonstorm times, indicating that acceleration has taken place. Some of the velocity increase is in the direction perpendicular to the magnetic field, indicating that the E × B velocity is enhanced. However, there is also an increase in the parallel direction, which could be due to nonadiabatic acceleration at the boundary or wave heating.

Convective growth of broadband turbulence in the plasma sheet boundary layer

International Nuclear Information System (INIS)

Dusenbery, P.B.

1987-01-01

Convective growth of slow and fast beam acoustic waves in the plasma sheet boundary layer (PSBL) is investigated. It has been shown previously that a could ion population must be present in order to excite beam acoustic waves in the PSBL. However, growth rates are significantly enhanced when warm plasma sheet boundary layer ions are present. Net wave growth along a ray path is determined by convective growth. This quantity is calculated for particle distribution models consistent with the PSBL where the intensity of broadband turbulence is observed to peak. Total number density dependence on beam acoustic convective growth is evaluated, and it is found that even for low density conditions of ∼0.01 cm -3 , a measurable level of broadband turbulence is expected. Relative drift effects between cold and warm ion populations are also considered. In particular, it is found that slow mode convective growth can be enhanced when slowly streaming cold ions are present, compared to fast ion streams

Energetic O+ and H+ Ions in the Plasma Sheet: Implications for the Transport of Ionospheric Ions

Science.gov (United States)

Ohtani, S.; Nose, M.; Christon, S. P.; Lui, A. T.

2011-01-01

The present study statistically examines the characteristics of energetic ions in the plasma sheet using the Geotail/Energetic Particle and Ion Composition data. An emphasis is placed on the O+ ions, and the characteristics of the H+ ions are used as references. The following is a summary of the results. (1) The average O+ energy is lower during solar maximum and higher during solar minimum. A similar tendency is also found for the average H+ energy, but only for geomagnetically active times; (2) The O+ -to -H+ ratios of number and energy densities are several times higher during solar maximum than during solar minimum; (3) The average H+ and O+ energies and the O+ -to -H+ ratios of number and energy densities all increase with geomagnetic activity. The differences among different solar phases not only persist but also increase with increasing geomagnetic activity; (4) Whereas the average H+ energy increases toward Earth, the average O+ energy decreases toward Earth. The average energy increases toward dusk for both the H+ and O+ ions; (5) The O+ -to -H+ ratios of number and energy densities increase toward Earth during all solar phases, but most clearly during solar maximum. These results suggest that the solar illumination enhances the ionospheric outflow more effectively with increasing geomagnetic activity and that a significant portion of the O+ ions is transported directly from the ionosphere to the near ]Earth region rather than through the distant tail.

Substorms in the Inner Plasma Sheet

Science.gov (United States)

Le Contel, O.; Perraut, S.; Roux, A.; Pellat, R.; Korth, A.

Thin Current Sheets (TCS) are regularly formed prior to substorm breakup, even in the near-Earth plasma sheet, as close as the geostationary orbit. A self-consistent kinetic theory describing the response of the plasma sheet to an electromagnetic perturbation is given. This perturbation corresponds to an external forcing, for instance caused by the solar wind (not an internal instability). The equilibrium of the configuration of this TCS in the presence of a time varying perturbation is shown to produce a strong parallel thermal anisotropy (T∥ > T⊺) of energetic electrons and ions (E>50keV) as well as an enhanced diamagnetic current carried by low energy ions (Ecurrents tend to enhance the confinement of this current sheet near the magnetic equator. These results are compared with data gathered by GEOS-2 at the geostationary orbit, where the magnetic signatures of TCS, and parallel anisotropies are regularly observed prior to breakup. By ensuring quasi-neutrality everywhere we find, when low frequency electromagnetic perturbations are applied, that although the magnetic field line remains an equipotential to the lowest order in Te/Ti, a field-aligned potential drop exists to the next order in (Te/Ti). Thus the development of a TCS implies the formation of a field-aligned potential drop (~= few hundred volts) to ensure the quasi-neutrality everywhere. For an earthward directed pressure gradient, a field-aligned electric field, directed towards the ionosphere, is obtained, on the western edge of the perturbation (i.e. western edge of the current sheet). Thus field aligned beams of electrons are expected to flow towards the equatorial region on the western edge of the current sheet. We study the stability of these electron beams and show that they are unstable to ``High Frequency'' (HF) waves. These ``HF'' waves are regularly observed at frequencies of the order of the proton gyrofrequency (fH+) just before, or at breakup. The amplitude of these HF waves is so

Gas isotope separation method using plasma sheet

International Nuclear Information System (INIS)

Takayama, K.; Takagi, K.; Fukvi, R.

1988-03-01

A high frequency electric field is applied to a plasma sheet with a frequency equal to the cyclotronic frequency of the ions to be separated. Because of resonance the cyclotronic radius of the isotope has increased and the electric charge is eliminated by collision with a separator and the isotope is separated in neutral particles [fr

Particle pitch angle diffusion due to nonadiabatic effects in the plasma sheet

International Nuclear Information System (INIS)

Gray, P.C.; Lee, L.C.

1982-01-01

In order to understand certain aspects of the plasma sheet dynamics, a numerical study of the nonadiabatic behavior of particles in a model field geometry is performed. The particle's magnetic moment as a function of time is calculated for various initial parameters, corresponding to various particle energies and degrees of field curvature. It is shown that the magnetic moment changes as the particle passes through the plasma sheet and that the magnitude of the change is related to the curvature of the field at the middle of the plasma sheet. The relation of the magnitude of the change in magnetic moment to the particle's pitch and phase angles as it passes through the sheet is numerically resolved. The nature of the change may be considered as a mechanism for pitch angle diffusion, and the diffusion coefficient is calculated. This scattering mechanism is significant for plasma sheet ions (1--10 keV) as well as energetic electrons (>100 keV)

Spatial and Temporal Extent of Ion Spectral Structures at the Inner Edge of the Plasma Sheet

Science.gov (United States)

Ferradas, C.; Reeves, G. D.; Zhang, J.; Spence, H. E.; Kistler, L. M.; Larsen, B.; Skoug, R. M.; Funsten, H. O.

2017-12-01

Several ion spectral structures are observed near the inner edge of the plasma sheet and constitute the signatures of ion drift and loss in the highly dynamic environment of the inner magnetosphere. Their study helps us understand ion access and losses in this region. Several studies have found that these structures vary with geomagnetic activity, local time, and ion species, but their spatial and temporal extent remain undetermined. We use data from the Helium, Oxygen, Proton, and Electron (HOPE) mass spectrometers onboard the Van Allen Probes to analyze the spectral structures in the energy range of 1- 50 keV. HOPE measurements on both Van Allen Probes spacecraft enable us to resolve the extent of these ion structures in space and time. As the structures respond to changes in the convection electric field on a variety of time scales, the lapping of the two spacecraft on time scales of minutes to hours helps determine their spatial and temporal evolution.

The statistical studies of the inner boundary of plasma sheet

Directory of Open Access Journals (Sweden)

J. B. Cao

2011-02-01

Full Text Available The penetration of plasma sheet ions into the inner magnetosphere is very important to the inner magnetospheric dynamics since plasma sheet ions are one of the major particle sources of ring current during storm times. However, the direct observations of the inner boundary of the plasma sheet are fairly rare due to the limited number of satellites in near equatorial orbits outside 6.6 RE. In this paper, we used the ion data recorded by TC-1 from 2004 to 2006 to study the distribution of inner boundary of ion plasma sheet (IBIPS and for the first time show the observational distribution of IBIPS in the equatorial plane. The IBIPS has a dawn-dusk asymmetry, being farthest to the Earth in the 06:00 08:00 LT bin and closest to the Earth in the 18:00–20:00 LT bin. Besides, the IBIPS has also a day-night asymmetry, which may be due to the fact that the ions on the dayside are exposed more time to loss mechanisms on their drift paths. The radial distance of IBIPS decrease generally with the increase of Kp index. The mean radial distance of IBIPS is basically larger than 6.6 RE during quiet times and smaller than 6.6 RE during active times. When the strength of convection electric field increases, the inward shift of IBIPS is most significant on the night side (22:00–02:00 LT. For Kp ≤ 0+, only 16% of IBIPSs penetrate inside the geosynchronous orbit. For 2 ≤ Kp +, however, 70% of IBIPSs penetrate inside the geosynchronous orbit. The IBIPS has weak correlations with the AE and Dst indexes. The average correlation coefficient between Ri and Kp is −0.58 while the correlation coefficient between Ri and AE/Dst is only −0.29/0.17. The correlation coefficients are local time dependent. Particularly, Ri and Kp are highly correlated (r=−0.72 in the night sector, meaning that the radial distance of IBIPS Ri in the night sector has the good response to the Kp index These observations indicate that Kp plays a key role in determining the position of

Ion motion in the wake driven by long particle bunches in plasmas

International Nuclear Information System (INIS)

Vieira, J.; Silva, L. O.; Fonseca, R. A.; Mori, W. B.

2014-01-01

We explore the role of the background plasma ion motion in self-modulated plasma wakefield accelerators. We employ Dawson's plasma sheet model to derive expressions for the transverse plasma electric field and ponderomotive force in the narrow bunch limit. We use these results to determine the on-set of the ion dynamics and demonstrate that the ion motion could occur in self-modulated plasma wakefield accelerators. Simulations show the motion of the plasma ions can lead to the early suppression of the self-modulation instability and of the accelerating fields. The background plasma ion motion can nevertheless be fully mitigated by using plasmas with heavier plasmas

Equilibrium structure of the plasma sheet boundary layer-lobe interface

Science.gov (United States)

Romero, H.; Ganguli, G.; Palmadesso, P.; Dusenbery, P. B.

1990-01-01

Observations are presented which show that plasma parameters vary on a scale length smaller than the ion gyroradius at the interface between the plasma sheet boundary layer and the lobe. The Vlasov equation is used to investigate the properties of such a boundary layer. The existence, at the interface, of a density gradient whose scale length is smaller than the ion gyroradius implies that an electrostatic potential is established in order to maintain quasi-neutrality. Strongly sheared (scale lengths smaller than the ion gyroradius) perpendicular and parallel (to the ambient magnetic field) electron flows develop whose peak velocities are on the order of the electron thermal speed and which carry a net current. The free energy of the sheared flows can give rise to a broadband spectrum of electrostatic instabilities starting near the electron plasma frequency and extending below the lower hybrid frequency.

Complete plasma dropouts at Vela satellites during thinning of the plasma sheet

International Nuclear Information System (INIS)

Lui, A.T.Y.; Hones, E.W. Jr.; Venkatesan, D.; Akasofu, S.; Bame, S.J.

1975-01-01

Five satellite years of Vela data are examined for plasma sheet thinnings. Complete proton disappearances (plasma dropouts) are the main subject here. During such times, the Vela satellite is temporarily in the high-latitude tail lobe. The distribution of such plasma dropouts within the magnetotail suggests that the semithickness of the plasma sheet near midnight seldom reaches less than 1 R/sub E/ during substorms and that the dawn and dusk portions of the plasma sheet remain thicker than the midnight portion. But it is also shown that the plasma sheet occasionally becomes very thin near the dusk magnetopause. No such severe thinnings of the plasma sheet are found near the dawn magnetopause. Plasma dropouts can occur regardless of the sign of the Z component of the IMF, but their frequency of occurrence seems to be greater when the Z component is negative.Three plasma dropouts which occurred in the midnight sector at unusually large distances from the estimated position of the neutral sheet were observed during geomagnetic storms. It is likely that the midnight sector of the plasma sheet can become very thick (approx.18 R/sub E/) at certain times during the main phase of storms. Detailed measurements in the plasma sheet were obtained near the beginning of a geomagnetic storm whose sc triggered a substorm. A compression of the plasma sheet at X/sub SM/approx. =-15 R/sub E/ occurred about 10 min after the sc onset at the earth and about 5 min after the start of plasma sheet thinning associated with the sc-related substorm. If compression-thinning of the plasma sheet initiated this substorm, the triggering action must have occurred earthward of X/sub SM/approx. =-15 R/sub E/

Polar Plasma at Ganymede: Ionospheric outflow and discovery of the plasma sheet

Science.gov (United States)

Collinson, G.; Paterson, W.; Dorelli, J.; Glocer, A.; Sarantos, M.; Wilson, R. J.; Bard, C.

2017-12-01

On the 27th of June 1996, the NASA Galileo spacecraft made humanities first flyby of Jupiter's largest moon, Ganymede, discovering that it is unique to science in being the only moon known to possess an internally generated magnetic dynamo field. Although Galileo carried a plasma spectrometer, the Plasma Subsystem (PLS), converting its highly complex raw data stream into meaningful plasma moments (density, temperature, velocity) is extremely challenging, and was only ever performed for the second (out of six) Ganymede flybys. Resurrecting the original Galileo PLS data analysis software, we processed the raw PLS data from G01, and for the first time present the properties of plasmas encountered. Dense, cold ions were observed outflowing from the moon's north pole (presumed to be dominated by H+ from the icy surface), with more diffuse, warmer field-aligned outflows in the lobes. Dropouts in plasma density combined with velocity perturbations either side of this suggest that Galileo briefly crossed the cusps onto closed magnetic field lines. PLS observations show that upon entry into the magnetosphere, Galileo crossed through the plasma sheet, observing plasma flows consistent with reconnection-driven convection, highly energized 105 eV ions, and a reversal in the magnetic field. The densities of plasmas flowing upwards from Ganymede's ionosphere were higher on open "lobe" field lines than on closed field lines, suggesting that the ionospheric source of these plasmas may be denser at the poles, there may be additional acceleration mechanisms at play, or the balance of ions were outside the energy range of PLS.

Pressure balance between lobe and plasma sheet

International Nuclear Information System (INIS)

Baumjohann, W.; Paschmann, G.; Luehr, H.

1990-01-01

Using eight months of AMPTE/IRM plasma and magnetic field data, the authors have done a statistical survey on the balance of total (thermal and magnetic) pressure in the Earth's plasma sheet and tail lobe. About 300,000 measurements obtained in the plasma sheet and the lobe were compared for different levels of magnetic activity as well as different distances from the Earth. The data show that lobe and plasma sheet pressure balance very well. Even in the worst case they do not deviate by more than half of the variance in the data itself. Approximately constant total pressure was also seen during a quiet time pass when IRM traversed nearly the whole magnetotail in the vertical direction, from the southern hemisphere lobe through the neutral sheet and into the northern plasma sheet boundary layer

Plasma dynamics in current sheets

International Nuclear Information System (INIS)

Bogdanov, S.Yu.; Drejden, G.V.; Kirij, N.P.; AN SSSR, Leningrad

1992-01-01

Plasma dynamics in successive stages of current sheet evolution is investigated on the base of analysis of time-spatial variations of electron density and electrodynamic force fields. Current sheet formation is realized in a two-dimensional magnetic field with zero line under the action of relatively small initial disturbances (linear regimes). It is established that in the limits of the formed sheet is concentrated dense (N e ∼= 10 16 cm -3 ) (T i ≥ 100 eV, bar-Z i ≥ 2) hot pressure of which is balanced by the magnetic action of electrodynamic forces is carried out both plasma compression in the sheet limits and the acceleration along the sheet surface from a middle to narrow side edges

On Jovian plasma sheet structure

International Nuclear Information System (INIS)

Khurana, K.K.; Kivelson, M.G.

1989-01-01

The authors evaluate several models of Jovian plasma sheet structure by determining how well they organize several aspects of the observed Voyager 2 magnetic field characteristics as a function of Jovicentric radial distance. It is shown that in the local time sector of the Voyager 2 outbound pass (near 0300 LT) the published hinged-magnetodisc models with wave (i.e., models corrected for finite wave velocity effects) are more successful than the published magnetic anomaly model in predicting locations of current sheet crossings. They also consider the boundary between the plasma sheet and the magnetotail lobe which is expected to vary slowly with radial distance. They use this boundary location as a further test of the models of the magnetotail. They show that the compressional MHD waves have much smaller amplitude in the lobes than in the plasma sheet and use this criterion to refine the identification of the plasma-sheet-lobe boundary. When the locations of crossings into and out of the lobes are examined, it becomes evident that the magnetic-anomaly model yields a flaring plasma sheet with a halfwidth of ∼ 3 R J at a radial distance of 20 R J and ∼ 12 R J at a radial distance of 100 R J . The hinged-magnetodisc models with wave, on the other hand, predict a halfwidth of ∼ 3.5 R J independent of distance beyond 20 R J . New optimized versions of the two models locate both the current sheet crossings and lobe encounters equally successfully. The optimized hinged-magnetodisc model suggests that the wave velocity decreases with increasing radial distance. The optimized magnetic anomaly model yields lower velocity contrast than the model of Vasyliunas and Dessler (1981)

Transient, Small-Scale Field-Aligned Currents in the Plasma Sheet Boundary Layer During Storm Time Substorms

Science.gov (United States)

Nakamura, R.; Sergeev, V. A.; Baumjohann, W.; Plaschke, F.; Magnes, W.; Fischer, D.; Varsani, A.; Schmid, D.; Nakamura, T. K. M.; Russell, C. T.;

On the balance of stresses in the plasma sheet.

Science.gov (United States)

Rich, F. J.; Wolf, R. A.; Vasyliunas, V. M.

1972-01-01

The stress resulting from magnetic tension on the neutral sheet must, in a steady state, be balanced by any one or a combination of (1) a pressure gradient in the direction along the axis of the tail, (2) a similar gradient of plasma flow kinetic energy, and (3) the tension resulting from a pressure anisotropy within the plasma sheet. Stress balance in the first two cases requires that the ratios h/LX and BZ/BX be of the same order of magnitude, where h is the half-thickness of the neutral sheet, LX is the length scale for variations along the axis of the tail, and BZ and BX are the magnetic field components in the plasma sheet just outside the neutral sheet. The second case requires, in addition, that the plasma flow speed within the neutral sheet be of the order of or larger than the Alfven speed outside the neutral sheet. Stress balance in the third case requires that just outside the neutral sheet the plasma pressure obey the marginal firehose stability condition.

Relativistic current sheets in electron-positron plasmas

International Nuclear Information System (INIS)

Zenitani, S.

2008-01-01

The current sheet structure with magnetic field reversal is one of the fundamental structure in space and astrophysical plasmas. It draws recent attention in high-energy astrophysical settings, where relativistic electron-positron plasmas are considered. In this talk we will review the recent progress of the physical processes in the relativistic current sheet. The kinetic stability of a single current sheet, the nonlinear behavior of these instabilities, and recent challenges on the multi current sheet systems are introduced. We will also introduce some problems of magnetic reconnection in these relativistic environments. (author)

A route to explosive large-scale magnetic reconnection in a super-ion-scale current sheet

Directory of Open Access Journals (Sweden)

K. G. Tanaka

2009-01-01

Full Text Available How to trigger magnetic reconnection is one of the most interesting and important problems in space plasma physics. Recently, electron temperature anisotropy (αeo=Te⊥/Te|| at the center of a current sheet and non-local effect of the lower-hybrid drift instability (LHDI that develops at the current sheet edges have attracted attention in this context. In addition to these effects, here we also study the effects of ion temperature anisotropy (αio=Ti⊥/Ti||. Electron anisotropy effects are known to be helpless in a current sheet whose thickness is of ion-scale. In this range of current sheet thickness, the LHDI effects are shown to weaken substantially with a small increase in thickness and the obtained saturation level is too low for a large-scale reconnection to be achieved. Then we investigate whether introduction of electron and ion temperature anisotropies in the initial stage would couple with the LHDI effects to revive quick triggering of large-scale reconnection in a super-ion-scale current sheet. The results are as follows. (1 The initial electron temperature anisotropy is consumed very quickly when a number of minuscule magnetic islands (each lateral length is 1.5~3 times the ion inertial length form. These minuscule islands do not coalesce into a large-scale island to enable large-scale reconnection. (2 The subsequent LHDI effects disturb the current sheet filled with the small islands. This makes the triggering time scale to be accelerated substantially but does not enhance the saturation level of reconnected flux. (3 When the ion temperature anisotropy is added, it survives through the small island formation stage and makes even quicker triggering to happen when the LHDI effects set-in. Furthermore the saturation level is seen to be elevated by a factor of ~2 and large-scale reconnection is achieved only in this case. Comparison with two-dimensional simulations that exclude the LHDI effects confirms that the saturation level

Slow convection of a magnetized plasma and the earth plasma sheet

International Nuclear Information System (INIS)

Hruska, A.

1980-01-01

Stationary convection of an isotropic, infinitely conducting plasma in a magnetic field with non-trivial geometry is discussed under the assumption that the inertial term in the equation of motion may be ignored. The energy gained or lost by a volume element of plasma per unit time does not vary along the field-lines. Simple relations between the components of the current density, depending on the field-line geometry, exist. Similar relations hold for the components of the plasma velocity. The theoretical analysis is applied to the geomagnetically-quiet plasma sheet and a qualitative physical picture of the sheet is suggested. The observed structure of the sheet is compatible with Axford-Hines type of convection perhaps combined with a low-speed flow from a distant neutral point. The magnetic-field-aligned currents are driven by the deformations of the closed field-lines which are enforced by the solar wind. (orig.)

Distributions of the ion temperature, ion pressure, and electron density over the current sheet surface

International Nuclear Information System (INIS)

Kyrie, N. P.; Markov, V. S.; Frank, A. G.; Vasilkov, D. G.; Voronova, E. V.

2016-01-01

The distributions of the ion temperature, ion pressure, and electron density over the width (the major transverse dimension) of the current sheet have been studied for the first time. The current sheets were formed in discharges in argon and helium in 2D and 3D magnetic configurations. It is found that the temperature of argon ions in both 2D and 3D magnetic configurations is almost uniform over the sheet width and that argon ions are accelerated by the Ampère force. In contrast, the distributions of the electron density and the temperature of helium ions are found to be substantially nonuniform. As a result, in the 2D magnetic configuration, the ion pressure gradient across the sheet width makes a significant contribution (comparable with the Ampère force) to the acceleration of helium ions, whereas in the 3D magnetic configuration, the Ampère force is counterbalanced by the pressure gradient.

Distributions of the ion temperature, ion pressure, and electron density over the current sheet surface

Energy Technology Data Exchange (ETDEWEB)

Kyrie, N. P., E-mail: kyrie@fpl.gpi.ru; Markov, V. S., E-mail: natalya.kyrie@yandex.ru; Frank, A. G.; Vasilkov, D. G.; Voronova, E. V. [Russian Academy of Sciences, Prokhorov General Physics Institute (Russian Federation)

2016-06-15

The distributions of the ion temperature, ion pressure, and electron density over the width (the major transverse dimension) of the current sheet have been studied for the first time. The current sheets were formed in discharges in argon and helium in 2D and 3D magnetic configurations. It is found that the temperature of argon ions in both 2D and 3D magnetic configurations is almost uniform over the sheet width and that argon ions are accelerated by the Ampère force. In contrast, the distributions of the electron density and the temperature of helium ions are found to be substantially nonuniform. As a result, in the 2D magnetic configuration, the ion pressure gradient across the sheet width makes a significant contribution (comparable with the Ampère force) to the acceleration of helium ions, whereas in the 3D magnetic configuration, the Ampère force is counterbalanced by the pressure gradient.

Ion-Ion Plasmas Produced by Electron Beams

Science.gov (United States)

Fernsler, R. F.; Leonhardt, D.; Walton, S. G.; Meger, R. A.

2001-10-01

The ability of plasmas to etch deep, small-scale features in materials is limited by localized charging of the features. The features charge because of the difference in electron and ion anisotropy, and thus one solution now being explored is to use ion-ion plasmas in place of electron-ion plasmas. Ion-ion plasmas are effectively electron-free and consist mainly of positive and negative ions. Since the two ion species behave similarly, localized charging is largely eliminated. However, the only way to produce ion-ion plasmas at low gas pressure is to convert electrons into negative ions through two-body attachment to neutrals. While the electron attachment rate is large at low electron temperatures (Te < 1 eV) in many of the halogen gases used for processing, these temperatures occur in most reactors only during the afterglow when the heating fields are turned off and the plasma is decaying. By contrast, Te is low nearly all the time in plasmas produced by electron beams, and therefore electron beams can potentially produce ion-ion plasmas continuously. The theory of ion-ion plasmas formed by pulsed electron beams is examined in this talk and compared with experimental results presented elsewhere [1]. Some general limitations of ion-ion plasmas, including relatively low flux levels, are discussed as well. [1] See the presentation by D. Leonhardt et al. at this conference.

Contribution of energetic and heavy ions to the plasma pressure: The 27 September to 3 October 2002 storm

Science.gov (United States)

Kronberg, E. A.; Welling, D.; Kistler, L. M.; Mouikis, C.; Daly, P. W.; Grigorenko, E. E.; Klecker, B.; Dandouras, I.

2017-09-01

Magnetospheric plasma sheet ions drift toward the Earth and populate the ring current. The ring current plasma pressure distorts the terrestrial internal magnetic field at the surface, and this disturbance strongly affects the strength of a magnetic storm. The contribution of energetic ions (>40 keV) and of heavy ions to the total plasma pressure in the near-Earth plasma sheet is not always considered. In this study, we evaluate the contribution of low-energy and energetic ions of different species to the total plasma pressure for the storm observed by the Cluster mission from 27 September until 3 October 2002. We show that the contribution of energetic ions (>40 keV) and of heavy ions to the total plasma pressure is ≃76-98.6% in the ring current and ≃14-59% in the magnetotail. The main source of oxygen ions, responsible for ≃56% of the plasma pressure of the ring current, is located at distances earthward of XGSE ≃ -13.5 RE during the main phase of the storm. The contribution of the ring current particles agrees with the observed Dst index. We model the magnetic storm using the Space Weather Modeling Framework (SWMF). We assess the plasma pressure output in the ring current for two different ion outflow models in the SWMF through comparison with observations. Both models yield reasonable results. The model which produces the most heavy ions agrees best with the observations. However, the data suggest that there is still potential for refinement in the simulations.

Multi-scale magnetic field intermittence in the plasma sheet

Directory of Open Access Journals (Sweden)

Z. Vörös

2003-09-01

Full Text Available This paper demonstrates that intermittent magnetic field fluctuations in the plasma sheet exhibit transitory, localized, and multi-scale features. We propose a multifractal-based algorithm, which quantifies intermittence on the basis of the statistical distribution of the "strength of burstiness", estimated within a sliding window. Interesting multi-scale phenomena observed by the Cluster spacecraft include large-scale motion of the current sheet and bursty bulk flow associated turbulence, interpreted as a cross-scale coupling (CSC process.Key words. Magnetospheric physics (magnetotail; plasma sheet – Space plasma physics (turbulence

Interpretation of magnetosonic waves in the boundary regions of the plasma sheet as seen by the ISEE 3 spacecraft

International Nuclear Information System (INIS)

Smith, P.R.; Hopcraft, K.I.; Murphy, N.

1987-01-01

Recent calculations that derive the normal-mode spectrum of an idealized magnetic current sheet are discussed. The Harris neutral-sheet equilibrium is perturbed with an ideal MHD displacement. The longitudinal polarization of the fundamental modes is calculated as a function of the position in the sheet. Using data from the energetic-ion instrument aboard ISEE 3, the thickness of the plasma sheet in the deep geomagnetic tail is estimated. This parameter enables a quantitative comparison between the boundary oscillations reported by Tsurutani and Smith (1984) and the normal mode oscillations derived by Hopcraft and Smith (1985) to be performed. The normal-mode solutions are found to be consistent with observation. Further aspects of the MHD wave spectrum that may lead to an observable variation of the mode character across the boundary of the plasma sheet are pointed out. 12 references

The Interaction of C-Band Microwaves with Large Plasma Sheets

International Nuclear Information System (INIS)

Ding Liang; Huo Wenqing; Yang Xinjie; Xu Yuemin

2012-01-01

A large plasma sheet 60 cm×60 cm×2 cm in size was generated using a hollow cathode, and measurements were conducted for interactions including transmission, reflection and absorption. With different discharge parameters, plasma sheets can vary and influence microwave strength. Microwave reflection decreases when the discharge current rises, and the opposite occurs in transmission. The C-band microwave is absorbed when it is propagated through large plasma sheets at higher pressure. When plasma density and collision frequency are fitted with incident microwave frequency, a large amount of microwave energy is consumed. Reflection, transmission and absorption all exist simultaneously. Plasma sheets are an attractive alternative to microwave steering at low pressure, and the microwave reflection used in receiving radar can be altered by changing the discharge parameters.

Continuous liquid sheet generator for ion stripping

International Nuclear Information System (INIS)

Gavin, B.; Batson, P.; Leemann, B.; Rude, B.

1984-10-01

Many of the technical problems of generating a large thin liquid sheet from 0.02 to 0.20 μm thick (3 to 40 μgm/cm 2 ) have been solved. It is shown that this perennial sheet is stable and consonant in dimension. Several ion beam species from the SuperHILAC have been used for evaluation; at 0.11 MeV/n. In one of three modes this sheet serves as an equivalent substitute for a carbon foil. The second mode is characterized by a solid-like charge state distribution but with a varying fraction of unstripped ions. The third mode gives stripping performance akin to a vapor stripping medium. 9 references, 7 figures

Interaction of a charge with a thin plasma sheet

International Nuclear Information System (INIS)

Bordag, M.

2007-01-01

The interaction of the electromagnetic field with a two-dimensional plasma sheet intended to describe the pi-electrons of a carbon nanotube or a C 60 molecule is investigated. By first integrating out the displacement field of the plasma or the electromagnetic field, different representations for quantities like the Casimir energy are derived which are shown to be consistent with one another. Starting from the covariant gauge for the electromagnetic field, it is shown that the matching conditions to which the presence of the plasma sheet can be reduced are different from the commonly used ones. The difference in the treatments does not show up in the Casimir force between two parallel sheets, but it is present in the Casimir-Polder force between a charge or a neutral atom and a sheet. At once, since the plasma sheet is a regularization of the conductor boundary conditions, this sheds light on the difference in physics found earlier in the realization of conductor boundary conditions as 'thin' or 'thick' boundary conditions in Phys. Rev. D 70, 085010 (2004)

Spontaneous magnetic fluctuations and collisionless regulation of the Earth's plasma sheet

Science.gov (United States)

Moya, P. S.; Espinoza, C.; Stepanova, M. V.; Antonova, E. E.; Valdivia, J. A.

2017-12-01

Even in the absence of instabilities, plasmas often exhibit inherent electromagnetic fluctuations which are present due to the thermal motion of charged particles, sometimes called thermal (quasi-thermal) noise. One of the fundamental and challenging problems of laboratory, space, and astrophysical plasma physics is the understanding of the relaxation processes of nearly collisionless plasmas, and the resultant state of electromagnetic plasma turbulence. The study of thermal fluctuations can be elegantly addressed by using the Fluctuation-Dissipation Theorem that describes the average amplitude of the fluctuations through correlations of the linear response of the media with the perturbations of the equilibrium state (the dissipation). Recently, it has been shown that solar wind plasma beta and temperature anisotropy observations are bounded by kinetic instabilities such as the ion cyclotron, mirror, and firehose instabilities. The magnetic fluctuations observed within the bounded area are consistent with the predictions of the Fluctuation-Dissipation theorem even far below the kinetic instability thresholds, with an enhancement of the fluctuation level near the thresholds. Here, for the very first time, using in-situ magnetic field and plasma data from the THEMIS spacecraft, we show that such regulation also occurs in the Earth's plasma sheet at the ion scales and that, regardless of the clear differences between the solar wind and the magnetosphere environments, spontaneous fluctuation and their collisionless regulation seem to be fundamental features of space and astrophysical plasmas, suggesting the universality of the processes.

Modeling the effect of doping on the catalyst-assisted growth and field emission properties of plasma-grown graphene sheet

International Nuclear Information System (INIS)

Gupta, Neha; Sharma, Suresh C.; Sharma, Rinku

2016-01-01

A theoretical model describing the effect of doping on the plasma-assisted catalytic growth of graphene sheet has been developed. The model accounts the charging rate of the graphene sheet, kinetics of all the plasma species, including the doping species, and the growth rate of graphene nuclei and graphene sheet due to surface diffusion, and accretion of ions on the catalyst nanoparticle. Using the model, it is observed that nitrogen and boron doping can strongly influence the growth and field emission properties of the graphene sheet. The results of the present investigation indicate that nitrogen doping results in reduced thickness and shortened height of the graphene sheet; however, boron doping increases the thickness and height of the graphene sheet. The time evolutions of the charge on the graphene sheet and hydrocarbon number density for nitrogen and boron doped graphene sheet have also been examined. The field emission properties of the graphene sheet have been proposed on the basis of the results obtained. It is concluded that nitrogen doped graphene sheet exhibits better field emission characteristics as compared to undoped and boron doped graphene sheet. The results of the present investigation are consistent with the existing experimental observations.

Modeling the effect of doping on the catalyst-assisted growth and field emission properties of plasma-grown graphene sheet

Energy Technology Data Exchange (ETDEWEB)

Gupta, Neha; Sharma, Suresh C.; Sharma, Rinku [Department of Applied Physics, Delhi Technological University (DTU), Shahbad Daulatpur, Bawana Road, Delhi-110042 (India)

2016-08-15

A theoretical model describing the effect of doping on the plasma-assisted catalytic growth of graphene sheet has been developed. The model accounts the charging rate of the graphene sheet, kinetics of all the plasma species, including the doping species, and the growth rate of graphene nuclei and graphene sheet due to surface diffusion, and accretion of ions on the catalyst nanoparticle. Using the model, it is observed that nitrogen and boron doping can strongly influence the growth and field emission properties of the graphene sheet. The results of the present investigation indicate that nitrogen doping results in reduced thickness and shortened height of the graphene sheet; however, boron doping increases the thickness and height of the graphene sheet. The time evolutions of the charge on the graphene sheet and hydrocarbon number density for nitrogen and boron doped graphene sheet have also been examined. The field emission properties of the graphene sheet have been proposed on the basis of the results obtained. It is concluded that nitrogen doped graphene sheet exhibits better field emission characteristics as compared to undoped and boron doped graphene sheet. The results of the present investigation are consistent with the existing experimental observations.

Thermal catastrophe in the plasma sheet boundary layer

International Nuclear Information System (INIS)

Smith, R.A.; Goertz, C.K.; Grossmann, W.

1986-01-01

This letter presents a first step towards a substorm model including particle heating and transport in the plasma sheet boundary layer (PSBL). The heating mechanism discussed is resonant absorption of Alfven waves. For some assumed MHD perturbation incident from the tail lobes onto the plasma sheet, the local heating rate in the PSBL has the form of a resonance function of the one-fluid plasma temperature. Balancing the local heating by convective transport of the heated plasma toward the central plasma sheet, and ''equation of state'' is found for the steady-state PSBL whose solution has the form of a mathematical catastrophe: at a critical value of a parameter containing the incident power flux, the local density, and the convection velocity, the equilibrium temperature jumps discontinuously. Associating this temperature increase with the abrupt onset of the substorm expansion phase, the catastrophe model indicates at least three ways in which the onset may be triggered. Several other consequences related to substorm dynamics are suggested by the simple catastrophe model

Modeling of plasma-sheet convection: implications for substorms

International Nuclear Information System (INIS)

Erickson, G.M.

1985-01-01

An answer is suggested to the question of why plasma and magnetic energy accumulate in the Earth's magnetotail to be released in sporadic events, namely substorms. It is shown that the idea of steady convection is inconsistent with the idea of slow, approximately lossless, plasma convection in a long, closed-field-line region that extends into a long magnetotail, such as occurs during Earthward convection in the Earth's plasma sheet. This inconsistency is argued generally and demonstrated specifically using several quantitative models of the Earth's magnetospheric magnetic field. These results suggest that plasma-sheet convection is necessarily time dependent. If flux tubes are to convect adiabatically earthward, the confining magnetic pressure in the tail lobes must increase with time, and the magnetotail must evolve into a more stretched configuration. Eventually, the magnetosphere must find some way to release plasma from inner-plasma-sheet flux tubes. This suggests an obvious role for the magnetospheric substorm in the convection process. To probe this process further, a two-dimensional, self-consistent, quasi-static convection model was developed. This model self consistently includes a dipole field and can reasonably account for the effects of inner-magnetospheric shielding

Radial evolution of the finite-width plasma sheet in a z-pinch: A parametric analysis based on conservation laws

International Nuclear Information System (INIS)

Sherar, A.G.

1996-01-01

A simple method that allows to estimate the macroscopic variables (width, temperature, density, radial velocity, etc.) of the plasma sheet in the first compression of a z-pinch, is presented. Following the snow-plow model, the radial compression is assumed as a process in which the mass is swept by a sheet of finite width. Very high pressures can be reached inside the sheet due to magnetic compression, higher than the filling gas pressure. A quasi-equilibrium hypothesis for the pressure of the layer is defined. From this assumption the thickness of the dense plasma sheet can be estimated. A set of MHD equations that include a term to compute total energy losses is used. The system of equations is written in the interface reference system in which the internal boundary of the sheet is at rest. In this early stage of the compression, the plasma temperature is mainly due to heavy particles. The results obtained using this model can explain ionic temperatures measured in cold plasmas which cannot be explained from electron-ion collisions. From an analytical study of the formation solution, a well-defined range of validity for each parameter of the model has been found. Based on physical conditions, these ranges of validity give a criterion to understanding the necessary conditions to build and maintain a moving plasma sheet. Using this model, other geometries besides the cylindrical one can be analyzed in the future

On contribution of energetic and heavy ions to the plasma pressure: Storm Sept 27 - Oct 4, 2002

Science.gov (United States)

Kronberg, E. A.; Mouikis, C.; Kistler, L. M.; Dandouras, I. S.; Daly, P. W.; Welling, D. T.; Grigorenko, E. E.

2015-12-01

Contribution of the energetic ions (>> 40 keV) and of heavy ions into the total plasma pressure is often neglected. In this study we evaluate the contribution of these components for the storm observed from September 27 to October 4 in 2002. The thermal component of the pressure for the protons, helium and oxygen at 0--40 keV/q is measured by the Cluster/CIS/CODIF sensor. The contribution of the energetic ions at energies >> 40 keV is calculated from the Cluster/RAPID/IIMS observations. The results show that before the storm has initiated, the contribution of the energetic ions in to the total pressure is indeed negligible in the tail plasma sheet, less than ˜1%. However, with the storm development contribution of the energetic part becomes significant, up to ˜30%, towards the recovery phase and cannot be neglected. Heavy ions contribute to the 27% of the total pressure and half of them are energetic. The contribution of energetic ions to the pressure of the ring current (L≃5) is significant. The heavy ions play a dominant role in the plasma pressure, about 62% during the main phase of the magnetic storm. Half of them are energetic ions. The SWMF/BATS-R-US MHD model underestimates the contribution of the energetic and heavy ions in to the ion distribution in the magnetotail plasma sheet and the ring current. The ring current plasma pressure distorts the terrestrial internal magnetic field and defines magnetic storm. Therefore, it is essential to take in to account the contribution of the energetic and heavy ions.

Geomagnetic activity effects on plasma sheet energy conversion

Directory of Open Access Journals (Sweden)

M. Hamrin

2010-10-01

Full Text Available In this article we use three years (2001, 2002, and 2004 of Cluster plasma sheet data to investigate what happens to localized energy conversion regions (ECRs in the plasma sheet during times of high magnetospheric activity. By examining variations in the power density, E·J, where E is the electric field and J is the current density obtained by Cluster, we have studied the influence on Concentrated Load Regions (CLRs and Concentrated Generator Regions (CGRs from variations in the geomagnetic disturbance level as expressed by the Kp, the AE, and the Dst indices. We find that the ECR occurrence frequency increases during higher magnetospheric activities, and that the ECRs become stronger. This is true both for CLRs and for CGRs, and the localized energy conversion therefore concerns energy conversion in both directions between the particles and the fields in the plasma sheet. A higher geomagnetic activity hence increases the general level of energy conversion in the plasma sheet. Moreover, we have shown that CLRs live longer during magnetically disturbed times, hence converting more electromagnetic energy. The CGR lifetime, on the other hand, seems to be unaffected by the geomagnetic activity level. The evidence for increased energy conversion during geomagnetically disturbed times is most clear for Kp and for AE, but there are also some indications that energy conversion increases during large negative Dst. This is consistent with the plasma sheet magnetically mapping to the auroral zone, and therefore being more tightly coupled to auroral activities and variations in the AE and Kp indices, than to variations in the ring current region as described by the Dst index.

Effects of the IMF on the plasma sheet

International Nuclear Information System (INIS)

Akasofu, S.-I.; Meng, C.-I.

1986-01-01

It is suggested that the IMF Bsub(z) component controls partially the geometry of the cross-section (y-z plane) of the plasma sheet. Our vacuum superposition model suggests that the cross-section has a dumbbell shape for te IMF Bsub(z) O. It is also suggested that the thinning and subsequent expansion of the plasma sheet during magnetospheric substorms are partially due to a direct effect of the IMF Bsub(z). (author)

Electrodynamic forces and plasma conductivity inside the current sheet

International Nuclear Information System (INIS)

Bogdanov, S.Yu.; Frank, A.G.; Markov, V.S.

1985-01-01

The process of accumulation and explosive release of magnetic energy was studied in a current sheet of plasma of a high-current linear discharge. The distribution of current density and of electrodynamic forces were measured and the time evolution of these quantities was determined. The evolution of the plasma conductivity was also obtained. The measured and calculated electrodynamic forces may explain the plasma acceleration up to the velocities about 3x10 4 m/s only near the sheet edges. (D.Gy.)

Statistical study of plasma sheet dynamics using ISEE 1 and 2 energetic particle flux data

International Nuclear Information System (INIS)

Dandouras, J.; Reme, H.; Saint-Marc, A.; Sauvaud, J.A.; Parks, G.K.; Anderson, K.A.; Lin, R.P.

1986-01-01

During magnetospheric substorms, satellites embedded in the plasma sheet often detect transient dropouts of plasma and energetic particle fluxes, a phenomemon generally interpreted as indicating the exit of the satellite into the magnetospheric lobe due to a plasma sheet thinning. In order to determine the large-scale dynamics of the near-earth plasma sheet during substorms, three satellite years of ISEE 1 and 2 energetic particle flux data (1.5 and 6 keV), corresponding to 461 particle flux dropouts, have been analyzed. The principal results show that flux dropouts can be observed anywhere in the nightside plasma sheet, independent of the satellite's geocentric distance (for R>12R/sub E/), magnetic local time (except near the magnetospheric flanks) and estimated distance to the neutral sheet. Furthermore, flux dropouts can be observed for any combination of the AE index value and the satellite's distance to the neutral sheet, which shows that the plasma sheet is dynamic even during weak magnetospheric disturbances. Substorms during which the satellites, though situated in the plasma sheet, did not detect any flux dropout, have also been examined, and it is found that the plasma sheet thickness can locally remain unaffected by substorm development for AE index values up to at least 1000 nT. The predictions of the two major plasma sheet thinning models, i.e., the near-tail X-type magnetic neutral line formation model and the MHD rarefaction wave propagation model, are compared to the experimental results, and it is concluded that neither model can account for all of the observations; plasma sheet dynamics are more complex. Phenomenologically, this study suggests that multiple pinching of the plasma sheet and/or large-amplitude three-dimensional plasma sheet oscillations are important in plasma sheet dynamics

Energy-dispersed ions in the plasma sheet boundary layer and associated phenomena: Ion heating, electron acceleration, Alfvén waves, broadband waves, perpendicular electric field spikes, and auroral emissions

Directory of Open Access Journals (Sweden)

A. Keiling

2006-10-01

Full Text Available Recent Cluster studies reported properties of multiple energy-dispersed ion structures in the plasma sheet boundary layer (PSBL that showed substructure with several well separated ion beamlets, covering energies from 3 keV up to 100 keV (Keiling et al., 2004a, b. Here we report observations from two PSBL crossings, which show a number of identified one-to-one correlations between this beamlet substructure and several plasma-field characteristics: (a bimodal ion conics (<1 keV, (b field-aligned electron flow (<1 keV, (c perpendicular electric field spikes (~20 mV/m, (d broadband electrostatic ELF wave packets (<12.5 Hz, and (e enhanced broadband electromagnetic waves (<4 kHz. The one-to-one correlations strongly suggest that these phenomena were energetically driven by the ion beamlets, also noting that the energy flux of the ion beamlets was 1–2 orders of magnitude larger than, for example, the energy flux of the ion outflow. In addition, several more loosely associated correspondences were observed within the extended region containing the beamlets: (f electrostatic waves (BEN (up to 4 kHz, (g traveling and standing ULF Alfvén waves, (h field-aligned currents (FAC, and (i auroral emissions on conjugate magnetic field lines. Possible generation scenarios for these phenomena are discussed. In conclusion, it is argued that the free energy of magnetotail ion beamlets drove a variety of phenomena and that the spatial fine structure of the beamlets dictated the locations of where some of these phenomena occurred. This emphasizes the notion that PSBL ion beams are important for magnetosphere-ionosphere coupling. However, it is also shown that the dissipation of electromagnetic energy flux (at altitudes below Cluster of the simultaneously occurring Alfvén waves and FAC was larger (FAC being the largest than the dissipation of beam kinetic energy flux, and thus these two energy carriers contributed more to the energy transport on PSBL field lines

Nonadiabatic heating of the central plasma sheet at substorm onset

International Nuclear Information System (INIS)

Huang, C.Y.; Frank, L.A.; Rostoker, G.; Fennell, J.; Mitchell, D.G.

1992-01-01

Heating events in the plasma sheet boundary layer and central plasma sheet are found to occur at the onset of expansive phase activity. The main effect is a dramatic increase in plasma temperature, coincident with a partial dipolarization of the magnetic field. Fluxes of energetic particles increase without dispersion during these events which occur at all radial distances up to 23 R E , the apogee of the ISEIE spacecraft. A major difference between these heating events and those observed at geosynchronous distances lies in the heating mechanism which is nonadiabatic beyond 10 R E but may be adiabatic closer to Earth. The energy required to account for the increase in plasma thermal energy is comparable with that required for Joule heating of the ionosphere. The plasma sheet must be considered as a major sink in the energy balance of substorm. The authors estimate lobe magnetic pressures during these events. Changes in lobe pressure are generally not correlated with onsets or intensifications of expansive phase activity

Electron energization in the geomagnetic tail current sheet

International Nuclear Information System (INIS)

Lyons, L.R.

1984-01-01

Electron motion in the distant tail current sheet is evaluated and found to violate the guiding center approximation at energies > or approx. =100 eV. Most electrons within the energy range approx.10 -1 -10 2 keV that enter the current sheet become trapped within the magnetic field reversal region. These electrons then convect earthward and gain energy from the cross-tail electric field. If the energy spectrum of electrons entering the current sheet is similar to that of electrons from the boundary layer surrounding the magnetotail, the energy gain from the electric field produces electron energy spectra comparable to those observed in the earth's plasma sheet. Thus current sheet interactions can be a significant source of particles and energy for plasma sheet electrons as well as for plasma sheet ions. A small fraction of electrons within the current sheet has its pitch angles scattered so as to be ejected from the current sheet within the atmospheric loss cone. These electrons can account for the electron precipitation near the high-latitude boundary of energetic electrons, which is approximately isotropic in pitch angle up to at least several hundred keV. Current sheet interaction should cause approximately isotropic auroral precipitation up to several hundred keV energies, which extends to significantly lower latitudes for ions than for electrons in agreement with low-altitude satellite observations. Electron precipitation associated with diffuse aurora generally has a transition at 1-10 keV to anisotropic pitch angle distributions. Such electron precipitation cannot be explained by current sheet interactions, but it can be explained by pitch angle diffusion driven by plasma turbulence

Upper Hybrid Resonance of Microwaves with a Large Magnetized Plasma Sheet

International Nuclear Information System (INIS)

Huo Wenqing; Guo Shijie; Ding Liang; Xu Yuemin

2013-01-01

A large magnetized plasma sheet with size of 60 cm × 60 cm × 2 cm was generated by a linear hollow cathode discharge under the confinement of a uniform magnetic field generated by a Helmholtz Coil. The microwave transmission characteristic of the plasma sheet was measured for different incident frequencies, in cases with the electric field polarization of the incident microwave either perpendicular or parallel to the magnetic field. In this measurement, parameters of the plasma sheet were changed by varying the discharge current and magnetic field intensity. In the experiment, upper hybrid resonance phenomena were observed when the electric field polarization of the incident wave was perpendicular to the magnetic field. These resonance phenomena cannot be found in the case of parallel polarization incidence. This result is consistent with theoretical consideration. According to the resonance condition, the electron density values at the resonance points are calculated under various experimental conditions. This kind of resonance phenomena can be used to develop a specific method to diagnose the electron density of this magnetized plasma sheet apparatus. Moreover, it is pointed out that the operating parameters of the large plasma sheet in practical applications should be selected to keep away from the upper hybrid resonance point to prevent signals from polarization distortion

Bulk ion acceleration and particle heating during magnetic reconnection in a laboratory plasma

Energy Technology Data Exchange (ETDEWEB)

Yoo, Jongsoo; Yamada, Masaaki; Ji, Hantao; Jara-Almonte, Jonathan; Myers, Clayton E. [Center for Magnetic Self-Organization, Princeton Plasma Physics Laboratory, Princeton, New Jersey 08543 (United States)

2014-05-15

Bulk ion acceleration and particle heating during magnetic reconnection are studied in the collisionless plasma of the Magnetic Reconnection Experiment (MRX). The plasma is in the two-fluid regime, where the motion of the ions is decoupled from that of the electrons within the ion diffusion region. The reconnection process studied here is quasi-symmetric since plasma parameters such as the magnitude of the reconnecting magnetic field, the plasma density, and temperature are compatible on each side of the current sheet. Our experimental data show that the in-plane (Hall) electric field plays a key role in ion heating and acceleration. The electrostatic potential that produces the in-plane electric field is established by electrons that are accelerated near the electron diffusion region. The in-plane profile of this electrostatic potential shows a “well” structure along the direction normal to the reconnection current sheet. This well becomes deeper and wider downstream as its boundary expands along the separatrices where the in-plane electric field is strongest. Since the in-plane electric field is 3–4 times larger than the out-of-plane reconnection electric field, it is the primary source of energy for the unmagnetized ions. With regard to ion acceleration, the Hall electric field causes ions near separatrices to be ballistically accelerated toward the outflow direction. Ion heating occurs as the accelerated ions travel into the high pressure downstream region. This downstream ion heating cannot be explained by classical, unmagnetized transport theory; instead, we conclude that ions are heated by re-magnetization of ions in the reconnection exhaust and collisions. Two-dimensional (2-D) simulations with the global geometry similar to MRX demonstrate downstream ion thermalization by the above mechanisms. Electrons are also significantly heated during reconnection. The electron temperature sharply increases across the separatrices and peaks just outside of the

Fast Fermi acceleration in the plasma sheet boundary layer

International Nuclear Information System (INIS)

Wu, C.S.; Lui, A.T.Y.

1989-01-01

A longstanding question in the field of magnetospheric physics is the source of the energetic particles which are commonly observed along the plasma sheet boundary layer (PSBL). Several models have been suggested for the acceleration of these particles. We suggest a means by which the fast Fermi acceleration mechanism [Wu, 1984] can accelerate electrons at the plasma sheet and perhaps account for some of the observations. We propose the following: A localized hydromagnetic disturbance propagating through the tail lobe region impinges upon the PSBL deforming it and displacing it in towards the central plasma sheet. The boundary layer can then act like a moving magnetic mirror. If the disturbance is propagating nearly perpendicular to the layer then its velocity projected parallel to the layer (and the magnetic field) can be very large resulting in significant acceleration of reflected particles. copyright American Geophysical Union 1989

Associations of geomagnetic activity with plasma sheet thinning and expansion: A statistical study

International Nuclear Information System (INIS)

Hones, E.W. Jr.; Pytte, T.; West, H.I. Jr.

1984-01-01

Associations of geomagnetic activity in the auroral zone with thinnings and expansions of the magnetotail plasma sheet are examined statistically in this paper. We first identified many plasma sheet thinnings and expansions in plasma and particle data from VELA satellites and from OGO 5 without reference to the ground magnetic data. These events were grouped according to the location of the detecting satellite in the magnetotail. For each such group the times of thinning or expansion were then used as fiducial times in a superposed-epoch analysis of the geomagnetic AL index values that were recorded in 8-hour intervals centered on the event times. The results show that many plasma sheet thinnings and expansions are related to discrete negative bay structures that are the classical signature of substorms. Furthermore, they support earlier findings that plasma sheet thinning and expansion at the VELA orbit (rroughly-equal18 R/sub E/) tend to be associated with the onset of the auroral zone negative bay and the beginning of its subsidence, respectively. Earthward of rroughly-equal13-15 R/sub E/, plasma sheet expansion occurs near the time of the onset of the negative bay, again in agreement with earlier findings. A large fraction of plasma sheet expansions to half thicknesses of > or approx. =6 R/sub E/ at the VELA orbit are associated not with a baylike geomagnetic disturbance but with subsidence of a prolonged interval of disturbance. The study also shows that many plasma sheet expansions are related simply to generally enhanced geomagnetic activity showing no baylike or other distinctive features

Production of free radical by magnetized sheet plasma with vertical gas-flow

International Nuclear Information System (INIS)

Tonegawa, Akira; Takatori, Masahiko; Kawamura, Kazutaka

1995-01-01

Free radicals play an important role in plasma processing, environment problem, and space plasma and so on because of their outstanding physical properties. Although much work has been done on the free radicals in the reactive plasma, very little is known about the production mechanism of the free radicals against various plasma parameters. To overcome this problem, we have proposed to do a new system of a magnetized sheet plasma with vertical gas-flow. The sheet plasma is a special type of strongly magnetized highly ionized slab plasma. This system is controlled to the parameters of radicals and plasma independently. Therefore, it is possible to make a quantitative analysis of free radicals as the simple one. In this paper, we describe the magnetized sheet plasma with vertical gas-flow system and report the preliminary results of production of the free radical. In particular, we show to produce and control the OH free radical which has been the most commonly studied combustion species

Plasma immersion surface modification with metal ion plasma

International Nuclear Information System (INIS)

Brown, I.G.; Yu, K.M.; Godechot, X.

1991-04-01

We describe here a novel technique for surface modification in which metal plasma is employed and by which various blends of plasma deposition and ion implantation can be obtained. The new technique is a variation of the plasma immersion technique described by Conrad and co-workers. When a substrate is immersed in a metal plasma, the plasma that condenses on the substrate remains there as a film, and when the substrate is then implanted, qualitatively different processes can follow, including' conventional' high energy ion implantation, recoil implantation, ion beam mixing, ion beam assisted deposition, and metallic thin film and multilayer fabrication with or without species mixing. Multiple metal plasma guns can be used with different metal ion species, films can be bonded to the substrate through ion beam mixing at the interface, and multilayer structures can be tailored with graded or abrupt interfaces. We have fabricated several different kinds of modified surface layers in this way. 22 refs., 4 figs

Gyrokinetic Electron and Fully Kinetic Ion Particle Simulation of Collisionless Plasma Dynamics

Energy Technology Data Exchange (ETDEWEB)

Yu Lin; Xueyi Wang; Liu Chen; Zhihong Lin

2009-08-11

Fully kinetic-particle simulations and hybrid simulations have been utilized for decades to investigate various fundamental plasma processes, such as magnetic reconnection, fast compressional waves, and wave-particle interaction. Nevertheless, due to disparate temporal and spatial scales between electrons and ions, existing fully kinetic-particle codes have to employ either unrealistically high electron-to-ion mass ratio, me/mi, or simulation domain limited to a few or a few ten's of the ion Larmor radii, or/and time much less than the global Alfven time scale in order to accommodate available computing resources. On the other hand, in the hybrid simulation, the ions are treated as fully kinetic particles but the electrons are treated as a massless fluid. The electron kinetic effects, e.g., wave-particle resonances and finite electron Larmor radius effects, are completely missing. Important physics, such as the electron transit time damping of fast compressional waves or the triggering mechanism of magnetic reconnection in collisionless plasmas is absent in the hybrid codes. Motivated by these considerations and noting that dynamics of interest to us has frequencies lower than the electron gyrofrequency, we planned to develop an innovative particle simulation model, gyrokinetic (GK) electrons and fully kinetic (FK) ions. In the GK-electron and FK-ion (GKe/FKi) particle simulation model, the rapid electron cyclotron motion is removed, while keeping finite electron Larmor radii, realistic me/mi ratio, wave-particle interactions, and off-diagonal components of electron pressure tensor. The computation power can thus be significantly improved over that of the full-particle codes. As planned in the project DE-FG02-05ER54826, we have finished the development of the new GK-electron and FK-ion scheme, finished its benchmark for a uniform plasma in 1-D, 2-D, and 3-D systems against linear waves obtained from analytical theories, and carried out a further convergence

Gyrokinetic Electron and Fully Kinetic Ion Particle Simulation of Collisionless Plasma Dynamics

International Nuclear Information System (INIS)

Lin, Yu; Wang, Xueyi; Chen, Liu; Lin, Zhihong

2009-01-01

Fully kinetic-particle simulations and hybrid simulations have been utilized for decades to investigate various fundamental plasma processes, such as magnetic reconnection, fast compressional waves, and wave-particle interaction. Nevertheless, due to disparate temporal and spatial scales between electrons and ions, existing fully kinetic-particle codes have to employ either unrealistically high electron-to-ion mass ratio, me/mi, or simulation domain limited to a few or a few ten's of the ion Larmor radii, or/and time much less than the global Alfven time scale in order to accommodate available computing resources. On the other hand, in the hybrid simulation, the ions are treated as fully kinetic particles but the electrons are treated as a massless fluid. The electron kinetic effects, e.g., wave-particle resonances and finite electron Larmor radius effects, are completely missing. Important physics, such as the electron transit time damping of fast compressional waves or the triggering mechanism of magnetic reconnection in collisionless plasmas is absent in the hybrid codes. Motivated by these considerations and noting that dynamics of interest to us has frequencies lower than the electron gyrofrequency, we planned to develop an innovative particle simulation model, gyrokinetic (GK) electrons and fully kinetic (FK) ions. In the GK-electron and FK-ion (GKe/FKi) particle simulation model, the rapid electron cyclotron motion is removed, while keeping finite electron Larmor radii, realistic me/mi ratio, wave-particle interactions, and off-diagonal components of electron pressure tensor. The computation power can thus be significantly improved over that of the full-particle codes. As planned in the project DE-FG02-05ER54826, we have finished the development of the new GK-electron and FK-ion scheme, finished its benchmark for a uniform plasma in 1-D, 2-D, and 3-D systems against linear waves obtained from analytical theories, and carried out a further convergence test

Experiments on Ion-Ion Plasmas From Discharges

Science.gov (United States)

Leonhardt, Darrin; Walton, Scott; Blackwell, David; Murphy, Donald; Fernsler, Richard; Meger, Robert

2001-10-01

Use of both positive and negative ions in plasma processing of materials has been shown to be advantageous[1] in terms of better feature evolution and control. In this presentation, experimental results are given to complement recent theoretical work[2] at NRL on the formation and decay of pulsed ion-ion plasmas in electron beam generated discharges. Temporally resolved Langmuir probe and mass spectrometry are used to investigate electron beam generated discharges during the beam on (active) and off (afterglow) phases in a variety of gas mixtures. Because electron-beam generated discharges inherently[3] have low electron temperatures (<0.5eV in molecular gases), negative ion characteristics are seen in the active as well as afterglow phases since electron detachment increases with low electron temperatures. Analysis of temporally resolved plasma characteristics deduced from these measurements will be presented for pure O_2, N2 and Ar and their mixtures with SF_6. Oxygen discharges show no noticeable negative ion contribution during the active or afterglow phase, presumably due to the higher energy electron attachment threshold, which is well above any electron temperature. In contrast, SF6 discharges demonstrate ion-ion plasma characteristics in the active glow and are completely ion-ion in the afterglow. Comparison between these discharges with published cross sections and production mechanisms will also be presented. [1] T.H. Ahn, K. Nakamura & H. Sugai, Plasma Sources Sci. Technol., 5, 139 (1996); T. Shibyama, H. Shindo & Y. Horiike, Plasma Sources Sci. Technol., 5, 254 (1996). [2] See presentation by R. F. Fernsler, at this conference. [3] D. Leonhardt, et al., 53rd Annual GEC, Houston, TX.

Lower hybrid drift instability in modified Harris current sheet with negative ions

International Nuclear Information System (INIS)

Huang Feng; Chen, Y-H; Shi Guifen; Hu, Z-Q; Yu, M Y

2008-01-01

The lower hybrid drift instability (LHDI) in a Harris current sheet with negative ions is investigated using the kinetic theory. Numerical results show that the negative ions have considerable effect on the LHDI. With increase of the negative-ion concentration, the growth rate of the LHDI increases and its real frequency decreases for any wave length. The Harris current sheet can thus be significantly modified

Experimental investigation of possible geomagnetic feedback from energetic (0.1 to 16 keV) terrestrial O(+) ions in the magnetotail current sheet

Science.gov (United States)

Lennartsson, O. W.; Klumpar, D. M.; Shelley, E. G.; Quinn, J. M.

1994-01-01

Data from energetic ion mass spectrometers on the ISEE 1 and AMPTE/CCE spacecraft are combined with geomagnetic and solar indices to investigate, in a statistical fashion, whether energized O(+) ions of terrestrial origin constitute a source of feedback which triggers or amplifies geomagnetic activity as has been suggested in the literature, by contributing a destabilizing mass increase in the magnetotail current sheet. The ISEE 1 data (0.1-16 keV/e) provide in situ observations of the O(+) concentration in the central plasma sheet, inside of 23 R(sub E), during the rising and maximum phases of solar cycle 21, as well as inner magnetosphere data from same period. The CCE data (0.1-17 keV/e) taken during the subsequent solar minimum all within 9 R(sub E). provide a reference for long-term variations in the magnetosphere O(+) content. Statistical correlations between the ion data and the indices, and between different indices. all point in the same direction: there is probably no feedback specific to the O(+) ions, in spite of the fact that they often contribute most of the ion mass density in the tail current sheet.

Current sheets with inhomogeneous plasma temperature: Effects of polarization electric field and 2D solutions

International Nuclear Information System (INIS)

Catapano, F.; Zimbardo, G.; Artemyev, A. V.; Vasko, I. Y.

2015-01-01

We develop current sheet models which allow to regulate the level of plasma temperature and density inhomogeneities across the sheet. These models generalize the classical Harris model via including two current-carrying plasma populations with different temperature and the background plasma not contributing to the current density. The parameters of these plasma populations allow regulating contributions of plasma density and temperature to the pressure balance. A brief comparison with spacecraft observations demonstrates the model applicability for describing the Earth magnetotail current sheet. We also develop a two dimensional (2D) generalization of the proposed model. The interesting effect found for 2D models is the nonmonotonous profile (along the current sheet) of the magnetic field component perpendicular to the current sheet. Possible applications of the model are discussed

Current sheets with inhomogeneous plasma temperature: Effects of polarization electric field and 2D solutions

Energy Technology Data Exchange (ETDEWEB)

Catapano, F., E-mail: menacata3@gmail.com; Zimbardo, G. [Dipartimento di Fisica, Università della Calabria, Rende, Cosenza (Italy); Artemyev, A. V., E-mail: ante0226@gmail.com; Vasko, I. Y. [Space Research Institute, RAS, Moscow (Russian Federation)

2015-09-15

We develop current sheet models which allow to regulate the level of plasma temperature and density inhomogeneities across the sheet. These models generalize the classical Harris model via including two current-carrying plasma populations with different temperature and the background plasma not contributing to the current density. The parameters of these plasma populations allow regulating contributions of plasma density and temperature to the pressure balance. A brief comparison with spacecraft observations demonstrates the model applicability for describing the Earth magnetotail current sheet. We also develop a two dimensional (2D) generalization of the proposed model. The interesting effect found for 2D models is the nonmonotonous profile (along the current sheet) of the magnetic field component perpendicular to the current sheet. Possible applications of the model are discussed.

Tunable electronic, electrical and optical properties of graphene oxide sheets by ion irradiation

Science.gov (United States)

Jayalakshmi, G.; Saravanan, K.; Panigrahi, B. K.; Sundaravel, B.; Gupta, Mukul

2018-05-01

The tunable electronic, electrical and optical properties of graphene oxide (GO) sheets were investigated using a controlled reduction by 500 keV Ar+-ion irradiation. The carbon to oxygen ratio of the GO sheets upon the ion beam reduction has been estimated using resonant Rutherford backscattering spectrometry analyses and its effect on the electrical and optical properties of GO sheets has been studied using sheet resistance measurements and photoluminescence (PL) measurements. The restoration of sp 2-hybridized carbon atoms within the sp 3 matrix is found to be increases with increasing the Ar+-ion fluences as evident from Fourier transform infrared, and x-ray absorption near-edge structure measurements. The decrease in the number of disorder-induced local density of states (LDOSs) within the π-π* gap upon the reduction causes the shifting of PL emission from near infra-red to blue region and decreases the sheet resistance. The improved electrical and optical properties of GO sheets were correlated to the decrease in the number of LDOSs within the π-π* gap. Our experimental investigations suggest ion beam irradiation is one of an effective approaches to reduce GO to RGO and to tailor its electronic, electrical and optical properties.

Dispersive O+ conics observed in the plasma-sheet boundary layer with CRRES/LOMICS during a magnetic storm

Directory of Open Access Journals (Sweden)

M. Wüest

1996-06-01

Full Text Available We present initial results from the Low-energy magnetospheric ion composition sensor (LOMICS on the Combined release and radiation effects satellite (CRRES together with electron, magnetic field, and electric field wave data. LOMICS measures all important magnetospheric ion species (H+, He++, He+, O++, O+ simultaneously in the energy range 60 eV to 45 keV, as well as their pitch-angle distributions, within the time resolution afforded by the spacecraft spin period of 30 s. During the geomagnetic storm of 9 July 1991, over a period of 42 min (0734 UT to 0816 UT the LOMICS ion mass spectrometer observed an apparent O+ conic flowing away from the southern hemisphere with a bulk velocity that decreased exponentially with time from 300 km/s to 50 km/s, while its temperature also decreased exponentially from 700 to 5 eV. At the onset of the O+ conic, intense low-frequency electromagnetic wave activity and strong pitch-angle scattering were also observed. At the time of the observations the CRRES spacecraft was inbound at L~7.5 near dusk, magnetic local time (MLT, and at a magnetic latitude of –23°. Our analysis using several CRRES instruments suggests that the spacecraft was skimming along the plasma sheet boundary layer (PSBL when the upward-flowing ion conic arrived. The conic appears to have evolved in time, both slowing and cooling, due to wave-particle interactions. We are unable to conclude whether the conic was causally associated with spatial structures of the PSBL or the central plasma sheet.

Ion acoustic waves in one- and two-negative ion species plasmas

International Nuclear Information System (INIS)

Ichiki, Ryuta; Shindo, Masako; Yoshimura, Shinji; Watanabe, Tsuguhiro; Kawai, Yoshinobu

2001-01-01

Ion acoustic waves in multi-ion plasmas including two negative ion species are investigated both numerically and experimentally. Numerically, the kinetic dispersion relation in two-negative ion plasmas is investigated. There are three modes of the ion acoustic waves in two-negative ion plasmas. In an Ar + -F - -SF 6 - plasma, only one of the three modes is dominant, regardless of the values of the electron and the ion temperatures. In a Xe + -F - -SF 6 - plasma, on the other hand, two modes can be important for a certain range of the electron-ion temperature ratio. The results also imply the possibility of the coexistence of the fast mode and the slow mode in one-negative ion plasmas. Experimentally, ion acoustic waves are observed in an Ar + -F - -SF 6 - plasma and are found to show a mode transition that agrees with the theoretical prediction for one of the three ion acoustic modes

Cross-tail velocity component in the plasma sheet fast flows

Directory of Open Access Journals (Sweden)

N. P. Dmitrieva

2008-06-01

Full Text Available The flux transfer in the magnetotail plasma sheet is mainly provided by the tail-aligned fast plasma flows (Bursty Bulk Flows – BBFs. In this paper we study the events with a large cross-tail velocity component, including their occurrence and relationship to the standard BBFs. We found out that a significant part of large Vy events are a subgroup connected with the BBFs propagation. The maximal deviation of the velocity vector from the X direction (about 40–50 degrees, on average is observed near the BBFs' leading front in the sheath, where the fast flow interacts with surrounding plasma. The average variation of the velocity direction in the vicinity of the BBF resembles a plasma vortex. Our results support the model, in which the BBF represents a polarized, bubble-like flux tube, propagating through the plasma sheet.

Energetic particle beams in the plasma sheet boundary layer following substorm expansion - Simultaneous near-earth and distant tail observations

Science.gov (United States)

Scholer, M.; Baker, D. N.; Gloeckler, G.; Ipavich, F. M.; Galvin, A. B.; Klecker, B.; Terasawa, T.; Tsurutani, B. T.

1986-01-01

Simultaneous observations of ions and electron beams in the near-earth and deep magnetotail following the onset of substorm are analyzed in terms of the substorm neutral line model. The observations were collected on March 20, 1983 with ISSE 1 and 3. Energy fluxes and intensity-time profiles of protons and electrons are studied. The data reveal that the reconnection at the near-earth neutral line produces ions and electrons for the plasma sheet boundary layer. The maximum electric potential along the neutral line is evaluated.

Deposition Rate and Energy Enhancements of TiN Thin-Film in a Magnetized Sheet Plasma Source

OpenAIRE

Hamdi Muhyuddin D. Barra; Henry J. Ramos

2011-01-01

Titanium nitride (TiN) has been synthesized using the sheet plasma negative ion source (SPNIS). The parameters used for its effective synthesis has been determined from previous experiments and studies. In this study, further enhancement of the deposition rate of TiN synthesis and advancement of the SPNIS operation is presented. This is primarily achieved by the addition of Sm-Co permanent magnets and a modification of the configuration in the TiN deposition process. The ...

Thinning and functionalization of few-layer graphene sheets by CF4 plasma treatment

KAUST Repository

Shen, Chao

2012-05-24

Structural changes of few-layer graphene sheets induced by CF4 plasma treatment are studied by optical microscopy and Raman spectroscopy, together with theoretical simulation. Experimental results suggest a thickness reduction of few-layer graphene sheets subjected to prolonged CF4 plasma treatment while plasma treatment with short time only leads to fluorine functionalization on the surface layer by formation of covalent bonds. Raman spectra reveal an increase in disorder by physical disruption of the graphene lattice as well as functionalization during the plasma treatment. The F/CF3 adsorption and the lattice distortion produced are proved by theoretical simulation using density functional theory, which also predicts p-type doping and Dirac cone splitting in CF4 plasma-treated graphene sheets that may have potential in future graphene-based micro/nanodevices.

Plasma sheet behavior during substorms

International Nuclear Information System (INIS)

Hones, E.W. Jr.

1983-01-01

Auroral or magnetic substorms are periods of enhanced auroral and geomagnetic activity lasting one to a few hours that signify increased dissipation of energy from the magnetosphere to the earth. Data acquired during the past decade from satellites in the near-earth sector of the magnetotail have suggested that during a substorm part of the plasma sheet is severed from earth by magnetic reconnection, forming a plasmoid, i.e., a body of plasma and closed magnetic loops, that flows out of the tail into the solar wind, thus returning plasma and energy that have earlier been accumulated from the solar wind. Very recently this picture has been dramatically confirmed by observations, with the ISEE 3 spacecraft in the magnetotail 220 R/sub E/ from earth, of plasmoids passing that location in clear delayed response to substorms. It now appears that plasmoid release is a fundamental process whereby the magnetosphere gives up excess stored energy and plasma, much like comets are seen to do, and that the phenomena of the substorm seen at earth are a by-product of that fundamental process

Superposed epoch analysis of pressure and magnetic field configuration changes in the plasma sheet

International Nuclear Information System (INIS)

Kistler, L.M.; Moebius, E.; Baumjohann, W.; Nagai, T.

1993-01-01

The authors report on an analysis of pressure and magnetic configuration within the plasma sheet following the initiation of substorm events. They have constructed this time dependent picture by using an epoch analysis of data from the AMPTE/IRM spacecraft. This analysis procedure can be used to construct a unified picture of events, provided they are reproducible, from a statistical analysis of a series of point measurements. The authors first determine the time dependent pressure changes in the plasma sheet. With some simplifying assumptions they then determine the z dependence of the pressure profiles, and from this distribution determine how field lines in the plasma sheet map to the neutral sheet

Ion source with plasma cathode

International Nuclear Information System (INIS)

Yabe, E.

1987-01-01

A long lifetime ion source with plasma cathode has been developed for use in ion implantation. In this ion source, a plasma of a nonreactive working gas serves as a cathode in place of a thermionic tungsten filament used in the Freeman ion source. In an applied magnetic field, the plasma is convergent, i.e., filamentlike; in zero magnetic field, it turns divergent and spraylike. In the latter case, the plasma exhibits a remarkable ability when the working gas has an ionization potential larger than the feed gas. By any combination of a working gas of either argon or neon and a feed gas of AsF 5 or PF 5 , the lifetime of this ion source was found to be more than 90 h with an extraction voltage of 40 kV and the corresponding ion current density 20 mA/cm 2 . Mass spectrometry results show that this ion source has an ability of generating a considerable amount of As + and P + ions from AsF 5 and PF 5 , and hence will be useful for realizing a fully cryopumped ion implanter system. This ion source is also eminently suitable for use in oxygen ion production

Plasma Immersion Ion Implantation in Radio Frequency Plasma

International Nuclear Information System (INIS)

Bora, B.; Bhuyan, H.; Wyndham, E.

2013-01-01

Plasma immersion ion implantation (PIII) has attracted wide interests since it emulates conventional ion-beam ion implantation (IBII) in niche applications. For instance, the technique has very high throughput, the implantation time is independent of the sample size, and samples with an irregular shape can be implanted without complex beam scanning or sample manipulation. For uniform ion implantation and deposition on to different substrates, like silicon, stainless steel etc., a capacitive coupled Radio frequency (RF), 13.6 MHz, plasma is used. During the PIII process, the physical parameters which are expected to play crucial rule in the deposition process like RF power, Negative pulse voltage and pulse duration, gas type and gas mixture, gas flow rates and the implantation dose are studied. The ion dose is calculated by dynamic sheath model and the plasma parameters are calculated from the V-I characteristic and power balance equation by homogeneous model of rf plasma discharge considering Ohmic as well as Stochastic heating. The correlations between the yield of the implantation process and the physical parameters as well as plasma parameters are discussed. (author)

Simultaneous Measurements of Substorm-Related Electron Energization in the Ionosphere and the Plasma Sheet

Science.gov (United States)

Sivadas, N.; Semeter, J.; Nishimura, Y.; Kero, A.

2017-10-01

On 26 March 2008, simultaneous measurements of a large substorm were made using the Poker Flat Incoherent Scatter Radar, Time History of Events and Macroscale Interactions during Substorm (THEMIS) spacecraft, and all sky cameras. After the onset, electron precipitation reached energies ≳100 keV leading to intense D region ionization. Identifying the source of energetic precipitation has been a challenge because of lack of quantitative and magnetically conjugate measurements of loss cone electrons. In this study, we use the maximum entropy inversion technique to invert altitude profiles of ionization measured by the radar to estimate the loss cone energy spectra of primary electrons. By comparing them with magnetically conjugate measurements from THEMIS-D spacecraft in the nightside plasma sheet, we constrain the source location and acceleration mechanism of precipitating electrons of different energy ranges. Our analysis suggests that the observed electrons ≳100 keV are a result of pitch angle scattering of electrons originating from or tailward of the inner plasma sheet at 9RE, possibly through interaction with electromagnetic ion cyclotron waves. The electrons of energy 10-100 keV are produced by pitch angle scattering due to a potential drop of ≲10 kV in the auroral acceleration region (AAR) as well as wave-particle interactions in and tailward of the AAR. This work demonstrates the utility of magnetically conjugate ground- and space-based measurements in constraining the source of energetic electron precipitation. Unlike in situ spacecraft measurements, ground-based incoherent scatter radars combined with an appropriate inversion technique can be used to provide remote and continuous-time estimates of loss cone electrons in the plasma sheet.

Survey of Galileo Plasma Observations in Jupiter's Plasma Sheet

Science.gov (United States)

Bagenal, Fran; Wilson, Robert J.; Siler, Scott; Paterson, William R.; Kurth, William S.

2016-01-01

The plasma science (PLS) Instrument on the Galileo spacecraft (orbiting Jupiter from December 1995 to September 2003) measured properties of the ions that were trapped in the magnetic field. The PLS data provide a survey of the plasma properties between approx. 5 and 30 Jupiter radii [R(sub J)] in the equatorial region. We present plasma properties derived via two analysis methods: numerical moments and forward modeling. We find that the density decreases with radial distance by nearly 5 orders of magnitude from approx. 2 to 3000 cm(exp.-3) at 6R(sub j) to approx. 0.05cm(sub -3) at 30 R(sub j). The density profile did not show major changes from orbit to orbit, suggesting that the plasma production and transport remained constant within about a factor of 2. The radial profile of ion temperature increased with distance which implied that contrary to the concept of adiabatic cooling on expansion, the plasma heats up as it expands out from Io's orbit (where TI is approx.60-80 eV) at approx. 6R(sub j) to a few keV at 30R(sub j).There does not seem to be a long-term, systematic variation in ion temperature with either local time or longitude. This latter finding differs from earlier analysis of Galileo PLS data from a selection of orbits. Further examination of all data from all Galileo orbits suggests that System Ill variations are transitory on timescales of weeks, consistent with the modeling of Cassini Ultraviolet Imaging Spectrograph observations. The plasma flow is dominated by azimuthal flow that is between 80% and 100% of corotation out to 25 R(sub j).

Drift wave in pair-ion plasma

Indian Academy of Sciences (India)

ion plasma are discussed. It is shown that the temperature and/or mass difference of both species could produce drift wave in a pair-ion plasma. The results are discussed in the context of the fullerene pair-ion plasma experiment.

Electron magnetic reconnection without ion coupling in Earth's turbulent magnetosheath

Science.gov (United States)

Phan, T. D.; Eastwood, J. P.; Shay, M. A.; Drake, J. F.; Sonnerup, B. U. Ö.; Fujimoto, M.; Cassak, P. A.; Øieroset, M.; Burch, J. L.; Torbert, R. B.; Rager, A. C.; Dorelli, J. C.; Gershman, D. J.; Pollock, C.; Pyakurel, P. S.; Haggerty, C. C.; Khotyaintsev, Y.; Lavraud, B.; Saito, Y.; Oka, M.; Ergun, R. E.; Retino, A.; Le Contel, O.; Argall, M. R.; Giles, B. L.; Moore, T. E.; Wilder, F. D.; Strangeway, R. J.; Russell, C. T.; Lindqvist, P. A.; Magnes, W.

2018-05-01

Magnetic reconnection in current sheets is a magnetic-to-particle energy conversion process that is fundamental to many space and laboratory plasma systems. In the standard model of reconnection, this process occurs in a minuscule electron-scale diffusion region1,2. On larger scales, ions couple to the newly reconnected magnetic-field lines and are ejected away from the diffusion region in the form of bi-directional ion jets at the ion Alfvén speed3-5. Much of the energy conversion occurs in spatially extended ion exhausts downstream of the diffusion region6. In turbulent plasmas, which contain a large number of small-scale current sheets, reconnection has long been suggested to have a major role in the dissipation of turbulent energy at kinetic scales7-11. However, evidence for reconnection plasma jetting in small-scale turbulent plasmas has so far been lacking. Here we report observations made in Earth's turbulent magnetosheath region (downstream of the bow shock) of an electron-scale current sheet in which diverging bi-directional super-ion-Alfvénic electron jets, parallel electric fields and enhanced magnetic-to-particle energy conversion were detected. Contrary to the standard model of reconnection, the thin reconnecting current sheet was not embedded in a wider ion-scale current layer and no ion jets were detected. Observations of this and other similar, but unidirectional, electron jet events without signatures of ion reconnection reveal a form of reconnection that can drive turbulent energy transfer and dissipation in electron-scale current sheets without ion coupling.

Energized Oxygen : Speiser Current Sheet Bifurcation

Science.gov (United States)

George, D. E.; Jahn, J. M.

2017-12-01

A single population of energized Oxygen (O+) is shown to produce a cross-tail bifurcated current sheet in 2.5D PIC simulations of the magnetotail without the influence of magnetic reconnection. Treatment of oxygen in simulations of space plasmas, specifically a magnetotail current sheet, has been limited to thermal energies despite observations of and mechanisms which explain energized ions. We performed simulations of a homogeneous oxygen background, that has been energized in a physically appropriate manner, to study the behavior of current sheets and magnetic reconnection, specifically their bifurcation. This work uses a 2.5D explicit Particle-In-a-Cell (PIC) code to investigate the dynamics of energized heavy ions as they stream Dawn-to-Dusk in the magnetotail current sheet. We present a simulation study dealing with the response of a current sheet system to energized oxygen ions. We establish a, well known and studied, 2-species GEM Challenge Harris current sheet as a starting point. This system is known to eventually evolve and produce magnetic reconnection upon thinning of the current sheet. We added a uniform distribution of thermal O+ to the background. This 3-species system is also known to eventually evolve and produce magnetic reconnection. We add one additional variable to the system by providing an initial duskward velocity to energize the O+. We also traced individual particle motion within the PIC simulation. Three main results are shown. First, energized dawn- dusk streaming ions are clearly seen to exhibit sustained Speiser motion. Second, a single population of heavy ions clearly produces a stable bifurcated current sheet. Third, magnetic reconnection is not required to produce the bifurcated current sheet. Finally a bifurcated current sheet is compatible with the Harris current sheet model. This work is the first step in a series of investigations aimed at studying the effects of energized heavy ions on magnetic reconnection. This work differs

Plasma source ion implantation

International Nuclear Information System (INIS)

Conrad, J.R.; Forest, C.

1986-01-01

The authors' technique allows the ion implantation to be performed directly within the ion source at higher currents without ion beam extraction and transport. The potential benefits include greatly increased production rates (factors of 10-1000) and the ability to implant non-planar targets without rastering or shadowing. The technique eliminates the ion extractor grid set, beam raster equipment, drift space and target manipulator equipment. The target to be implanted is placed directly within the plasma source and is biased to a large negative potential so that plasma ions gain energy as they accelerate through the potential drop across the sheath that forms at the plasma boundary. Because the sheath surrounds the target on all sides, all surfaces of the target are implanted without the necessity to raster the beam or to rotate the target. The authors have succeeded in implanting nitrogen ions in a silicon target to the depths and concentrations required for surface treatment of materials like stainless steel and titanium alloys. They have performed ESCA measurements of the penetration depth profile of a silicon target that was biased to 30 kV in a nitrogen discharge plasma. Nitrogen ions were implanted to a depth of 700A at a peak concentration of 30% atomic. The measured profile is quite similar to a previously obtained profile in titanium targets with conventional techniques

Sawtooth events and O+ in the plasma sheet and boundary layer: CME- and SIR-driven events

Science.gov (United States)

Lund, E. J.; Nowrouzi, N.; Kistler, L. M.; Cai, X.; Liao, J.

2017-12-01

The role of ionospheric ions in sawtooth events is an open question. Simulations[1,2,3] suggest that O+ from the ionosphere produces a feedback mechanism for driving sawtooth events. However, observational evidence[4,5] suggest that the presence of O+ in the plasma sheet is neither necessary nor sufficient. In this study we investigate whether the solar wind driver of the geomagnetic storm has an effect on the result. Building on an earlier study[4] that used events for which Cluster data is available in the plasma sheet and boundary layer, we perform a superposed epoch analysis for coronal mass ejection (CME) driven storms and streaming interaction region (SIR) driven storms separately, to investigate the hypothesis that ionospheric O+ is an important contributor for CME-driven storms but not SIR-driven storms[2]. [1]O. J. Brambles et al. (2011), Science 332, 1183.[2]O. J. Brambles et al. (2013), JGR 118, 6026.[3]R. H. Varney et al. (2016), JGR 121, 9688.[4]J. Liao et al. (2014), JGR 119, 1572.[5]E. J. Lund et al. (2017), JGR, submitted.

Experimental Investigation of the Neutral sheet Profile During Magnetic Reconnection

International Nuclear Information System (INIS)

Trintchouk, F.; Ji, H.; Yamada, M.; Kulsrud, R.; Hsu, S.; Carter, T.

1999-01-01

During magnetic reconnection, a ''neutral sheet'' current is induced, heating the plasma. The resultant plasma thermal pressure forms a stationary equilibrium with the opposing magnetic fields. The reconnection layer profile holds significant clues about the physical mechanisms which control reconnection. On the Magnetic Reconnection Experiment [M. Yamada et al., Phys. Plasmas 4, 1936 (1997)], a quasi steady-state and axisymmetric neutral sheet profile has been measured precisely using a magnetic probe array with spatial resolution equal to one quarter of the ion gyro-radius. It was found that the reconnecting field profile fits well with a Harris-type profile [E. G. Harris, Il Nuovo Cimento 23, 115 (1962)], B(x) approximately tanh(x/delta). This agreement is remarkable since the Harris theory does not take into account reconnection and associated electric fields and dissipation. An explanation for this agreement is presented. The sheet thickness delta is found to be approximately 0.4 times the ion skin depth, which agrees with a generalized Harris theory incorporating non-isothermal electron and ion temperatures and finite electric field. The detailed study of additional local features of the reconnection region is also presented

High-beta plasma blobs in the morningside plasma sheet

Directory of Open Access Journals (Sweden)

G. Haerendel

1999-12-01

Full Text Available Equator-S frequently encountered, i.e. on 30% of the orbits between 1 March and 17 April 1998, strong variations of the magnetic field strength of typically 5–15-min duration outside about 9RE during the late-night/early-morning hours. Very high-plasma beta values were found, varying between 1 and 10 or more. Close conjunctions between Equator-S and Geotail revealed the spatial structure of these "plasma blobs" and their lifetime. They are typically 5–10° wide in longitude and have an antisymmetric plasma or magnetic pressure distribution with respect to the equator, while being altogether low-latitude phenomena  (≤ 15°. They drift slowly sunward, exchange plasma across the equator and have a lifetime of at least 15–30 min. While their spatial structure may be due to some sort of mirror instability, little is known about the origin of the high-beta plasma. It is speculated that the morningside boundary layer somewhat further tailward may be the source of this plasma. This would be consistent with the preference of the plasma blobs to occur during quiet conditions, although they are also found during substorm periods. The relation to auroral phenomena in the morningside oval is uncertain. The energy deposition may be mostly too weak to generate a visible signature. However, patchy aurora remains a candidate for more disturbed periods.Key words. Magnetospheric physics (plasma convection; plasma sheet; plasma waves and instabilities

The gridless plasma ion source (GIS) for plasma ion assisted optical coating

International Nuclear Information System (INIS)

You Dawei; Li Xiaoqian; Wang Yu; Lin Yongchang

2004-01-01

High-quality optical coating is a key technology for modern optics. Ion-assisted deposition technology was used to improve the vaporized coating in 1980's. The GIS (gridless ion source), which is an advanced plasma source for producing a high-quality optical coating in large area, can produce a large area uniformity>1000 mm (diameter), a high ion current density ∼0.5 mA/cm 2 , 20 eV-200 eV energetic plasma ions and can activate reactive gas and film atoms. Now we have developed a GIS system. The GIS and the plasma ion-assisted deposition technology are investigated to achieve a high-quality optical coating. The GIS is a high power and high current source with a power of 1 kW-7.5 kW, a current of 10 A- 70 A and an ion density of 200 μA/cm 2 -500 μA/cm 2 . Because of the special magnetic structure, the plasma-ion extraction efficiency has been improved to obtain a maximum ion density of 500 μA/cm 2 in the medium power (∼4 kW) level. The GIS applied is of a special cathode structure, so that the GIS operation can be maintained under a rather low power and the lifetime of cathode will be extended. The GIS has been installed in the LPSX-1200 type box coating system. The coated TiO 2 , SiO 2 films such as antireflective films with the system have the same performance reported by Leybold Co, 1992, along with a controllable refractive index and film structure. (authors)

Ion-acoustic plasma turbulence

International Nuclear Information System (INIS)

Bychenkov, V.Y.; Silin, V.P.

1982-01-01

A theory is developed of the nonlinear state that is established in a plasma as a result of development of ion-acoustic instability. Account is taken simultaneously of the linear induced scattering of the waves by the ions and of the quasilinear relaxation of the electrons by the ion-acoustic pulsations. The distribution of the ion-acoustic turbulence in frequency and in angle is obtained. An Ohm's law is established and expressions are obtained for the electronic heat flux and for the relaxation time of the electron temperature in a turbulent plasma. Anomalously large absorption and scattering of the electromagnetic waves by the ion-acoustic pulsations is predicted

Temporal Evolution of Ion Spectral Structures During a Geomagnetic Storm: Observations and Modeling

Science.gov (United States)

Ferradas, C. P.; Zhang, J.-C.; Spence, H. E.; Kistler, L. M.; Larsen, B. A.; Reeves, G. D.; Skoug, R. M.; Funsten, H. O.

2018-01-01

Using the Van Allen Probes/Helium, Oxygen, Proton, and Electron mass spectrometer, we perform a case study of the temporal evolution of ion spectral structures observed in the energy range of 1 to 50 keV throughout the geomagnetic storm of 2 October 2013. The ion spectral features are observed near the inner edge of the plasma sheet and are signatures of fresh transport from the plasma sheet into the inner magnetosphere. We find that the characteristics of the ion structures are determined by the intensity of the convection electric field. Prior to the beginning of the storm, the plasma sheet inner edge exhibits narrow nose spectral structures that vary little in energy across L values. Ion access to the inner magnetosphere during these times is limited to the nose energy bands. As convection is enhanced and large amounts of plasma are injected from the plasma sheet during the main phase of the storm, ion access occurs at a wide energy range, as no nose structures are observed. As the magnetosphere recovers from the storm, single noses and then multiple noses are observed once again. We use a model of ion drift and losses due to charge exchange to simulate the ion spectra and gain insight into the main observed features.

A review on ion–ion plasmas created in weakly magnetized electronegative plasmas

International Nuclear Information System (INIS)

Aanesland, A; Bredin, J; Chabert, P

2014-01-01

Ion–Ion plasmas are electronegative plasmas where the electron density is several orders of magnitude lower than the negative ion density. These plasmas have been scarcely observed and investigated since the 1960s and are formed as a transient state of pulsed plasmas or in separate regions in magnetized plasmas. In this review we focus on the latter case of continuous formation of ion–ion plasmas created at the periphery of magnetized plasma columns or downstream localized magnetic barriers. We bring together and review experimental results already published elsewhere and complement them with new results to illustrate the physics important in ion–ion plasma formation and highlight in particular unanswered questions. We show that with a good design the density in the ion–ion region is dropping only by a factor of 2–3 from the initial plasma density. These plasmas can therefore be well suited for various ion source applications when both fluxes or beams of positive and negative ions are desired, and when electrons can cause harmful effects. (paper)

Beam-plasma discharge in a Kyoto beam-plasma-ion source

International Nuclear Information System (INIS)

Ishikawa, J.; Takagi, T.

1983-01-01

A beam-plasma type ion source employing an original operating principle has been developed by the present authors. The ion source consists of an ion extraction region with an electron gun, a thin long drift tube as the plasma production chamber, and a primary electron beam collector. An electron beam is effectively utilized for the dual purpose of high density plasma production as a result of beam-plasma discharge, and high current ion beam extraction with ion space-charge compensation. A high density plasma of the order of 10 11 --10 13 cm -3 was produced by virtue of the beam-plasma discharge which was caused by the interaction between a space-charge wave on the electron beam and a high frequency plasma wave. The plasma density then produced was 10 2 --10 3 times the density produced only by collisional ionization by the electron beam. In order to obtain a stable beam-plasma discharge, a secondary electron beam emitted from the electron collector should be utilized. The mechanism of the beam-plasma discharge was analyzed by use of a linear theory in the case of the small thermal energy of the electron beam, and by use of a quasilinear theory in the case of the large thermal energy. High current ion beams of more than 0.1 A were extracted even at a low extraction voltage of 1--5 kV

Thermomechanical processing of plasma sprayed intermetallic sheets

Science.gov (United States)

Hajaligol, Mohammad R.; Scorey, Clive; Sikka, Vinod K.; Deevi, Seetharama C.; Fleischhauer, Grier; Lilly, Jr., A. Clifton; German, Randall M.

2001-01-01

A powder metallurgical process of preparing a sheet from a powder having an intermetallic alloy composition such as an iron, nickel or titanium aluminide. The sheet can be manufactured into electrical resistance heating elements having improved room temperature ductility, electrical resistivity, cyclic fatigue resistance, high temperature oxidation resistance, low and high temperature strength, and/or resistance to high temperature sagging. The iron aluminide has an entirely ferritic microstructure which is free of austenite and can include, in weight %, 4 to 32% Al, and optional additions such as .ltoreq.1% Cr, .gtoreq.0.05% Zr .ltoreq.2% Ti, .ltoreq.2% Mo, .ltoreq.1% Ni, .ltoreq.0.75% C, .ltoreq.0.1% B, .ltoreq.1% submicron oxide particles and/or electrically insulating or electrically conductive covalent ceramic particles, .ltoreq.1% rare earth metal, and/or .ltoreq.3% Cu. The process includes forming a non-densified metal sheet by consolidating a powder having an intermetallic alloy composition such as by roll compaction, tape casting or plasma spraying, forming a cold rolled sheet by cold rolling the non-densified metal sheet so as to increase the density and reduce the thickness thereof and annealing the cold rolled sheet. The powder can be a water, polymer or gas atomized powder which is subjecting to sieving and/or blending with a binder prior to the consolidation step. After the consolidation step, the sheet can be partially sintered. The cold rolling and/or annealing steps can be repeated to achieve the desired sheet thickness and properties. The annealing can be carried out in a vacuum furnace with a vacuum or inert atmosphere. During final annealing, the cold rolled sheet recrystallizes to an average grain size of about 10 to 30 .mu.m. Final stress relief annealing can be carried out in the B2 phase temperature range.

Experimental investigation of a 1 kA/cm² sheet beam plasma cathode electron gun.

Science.gov (United States)

Kumar, Niraj; Pal, Udit Narayan; Pal, Dharmendra Kumar; Prajesh, Rahul; Prakash, Ram

2015-01-01

In this paper, a cold cathode based sheet-beam plasma cathode electron gun is reported with achieved sheet-beam current density ∼1 kA/cm(2) from pseudospark based argon plasma for pulse length of ∼200 ns in a single shot experiment. For the qualitative assessment of the sheet-beam, an arrangement of three isolated metallic-sheets is proposed. The actual shape and size of the sheet-electron-beam are obtained through a non-conventional method by proposing a dielectric charging technique and scanning electron microscope based imaging. As distinct from the earlier developed sheet beam sources, the generated sheet-beam has been propagated more than 190 mm distance in a drift space region maintaining sheet structure without assistance of any external magnetic field.

Plasma sheet fast flows and auroral dynamics during substorm: a case study

Directory of Open Access Journals (Sweden)

N. L. Borodkova

2002-03-01

Full Text Available Interball-1 observations of a substorm development in the mid-tail on 16 December 1998 are compared with the auroral dynamics obtained from the Polar UV imager. Using these data, the relationship between plasma flow directions in the tail and the location of the auroral activation is examined. Main attention is given to tailward and earth-ward plasma flows, interpreted as signatures of a Near Earth Neutral Line (NENL. It is unambiguously shown that in the mid-plasma sheet the flows were directed tailward when the auroral bulge developed equatorward of the spacecraft ionospheric footprint. On the contrary, when active auroras moved poleward of the Interball-1 projection, earthward fast flow bursts were observed. This confirms the concept that the NENL (or flow reversal region is the source of auroras forming the poleward edge of the auroral bulge. The observed earthward flow bursts have all typical signatures of Bursty Bulk Flows (BBFs, described by Angelopolous et al. (1992. These BBFs are related to substorm activations starting at the poleward edge of the expanded auroral bulge. We interpret the BBFs as a result of reconnection pulses occurring tail-ward of Interball-1. In addition, some non-typically observed phenomena were detected in the plasma sheet during this substorm: (i tailward/earthward flows were superimposed on a very strong duskward flow, and (ii wavy structures of both magnetic field and plasma density were registered. The latter observation is probably linked to the filamentary structure of the current sheet.Key words. Magnetospheric physics (auroral phenomena; plasma sheet; storms and substorms

Heavy-ion dominance near Cluster perigees

Science.gov (United States)

Ferradas, C. P.; Zhang, J.-C.; Kistler, L. M.; Spence, H. E.

2015-12-01

Time periods in which heavy ions dominate over H+ in the energy range of 1-40 keV were observed by the Cluster Ion Spectrometry (CIS)/COmposition DIstribution Function (CODIF) instrument onboard Cluster Spacecraft 4 at L values less than 4. The characteristic feature is a narrow flux peak at around 10 keV that extends into low L values, with He+ and/or O+ dominating. In the present work we perform a statistical study of these events and examine their temporal occurrence and spatial distribution. The observed features, both the narrow energy range and the heavy-ion dominance, can be interpreted using a model of ion drift from the plasma sheet, subject to charge exchange losses. The narrow energy range corresponds to the only energy range that has direct drift access from the plasma sheet during quiet times. The drift time to these locations from the plasma sheet is > 30 h, so that charge exchange has a significant impact on the population. We show that a simple drift/loss model can explain the dependence on L shell and MLT of these heavy-ion-dominant time periods.

High-beta plasma blobs in the morningside plasma sheet

Directory of Open Access Journals (Sweden)

G. Haerendel

Full Text Available Equator-S frequently encountered, i.e. on 30% of the orbits between 1 March and 17 April 1998, strong variations of the magnetic field strength of typically 5–15-min duration outside about 9R_E during the late-night/early-morning hours. Very high-plasma beta values were found, varying between 1 and 10 or more. Close conjunctions between Equator-S and Geotail revealed the spatial structure of these "plasma blobs" and their lifetime. They are typically 5–10^° wide in longitude and have an antisymmetric plasma or magnetic pressure distribution with respect to the equator, while being altogether low-latitude phenomena 
(≤ 15^°. They drift slowly sunward, exchange plasma across the equator and have a lifetime of at least 15–30 min. While their spatial structure may be due to some sort of mirror instability, little is known about the origin of the high-beta plasma. It is speculated that the morningside boundary layer somewhat further tailward may be the source of this plasma. This would be consistent with the preference of the plasma blobs to occur during quiet conditions, although they are also found during substorm periods. The relation to auroral phenomena in the morningside oval is uncertain. The energy deposition may be mostly too weak to generate a visible signature. However, patchy aurora remains a candidate for more disturbed periods.

Key words. Magnetospheric physics (plasma convection; plasma sheet; plasma waves and instabilities

Large area ion and plasma beam sources

Energy Technology Data Exchange (ETDEWEB)

Waldorf, J. [IPT Ionen- und Plasmatech. GmbH, Kaiserslautern (Germany)

1996-06-01

In the past a number of ion beam sources utilizing different methods for plasma excitation have been developed. Nevertheless, a widespread use in industrial applications has not happened, since the sources were often not able to fulfill specific demands like: broad homogeneous ion beams, compatibility with reactive gases, low ion energies at high ion current densities or electrical neutrality of the beam. Our contribution wants to demonstrate technical capabilities of rf ion and plasma beam sources, which can overcome the above mentioned disadvantages. The physical principles and features of respective sources are presented. We report on effective low pressure plasma excitation by electron cyclotron wave resonance (ECWR) for the generation of dense homogeneous plasmas and the rf plasma beam extraction method for the generation of broad low energy plasma beams. Some applications like direct plasma beam deposition of a-C:H and ion beam assisted deposition of Al and Cu with tailored thin film properties are discussed. (orig.).

Large area ion and plasma beam sources

International Nuclear Information System (INIS)

Waldorf, J.

1996-01-01

In the past a number of ion beam sources utilizing different methods for plasma excitation have been developed. Nevertheless, a widespread use in industrial applications has not happened, since the sources were often not able to fulfill specific demands like: broad homogeneous ion beams, compatibility with reactive gases, low ion energies at high ion current densities or electrical neutrality of the beam. Our contribution wants to demonstrate technical capabilities of rf ion and plasma beam sources, which can overcome the above mentioned disadvantages. The physical principles and features of respective sources are presented. We report on effective low pressure plasma excitation by electron cyclotron wave resonance (ECWR) for the generation of dense homogeneous plasmas and the rf plasma beam extraction method for the generation of broad low energy plasma beams. Some applications like direct plasma beam deposition of a-C:H and ion beam assisted deposition of Al and Cu with tailored thin film properties are discussed. (orig.)

Motion of the plasma critical layer during relativistic-electron laser interaction with immobile and comoving ion plasma for ion acceleration

International Nuclear Information System (INIS)

Sahai, Aakash A.

2014-01-01

We analyze the motion of the plasma critical layer by two different processes in the relativistic-electron laser-plasma interaction regime (a 0 >1). The differences are highlighted when the critical layer ions are stationary in contrast to when they move with it. Controlling the speed of the plasma critical layer in this regime is essential for creating low-β traveling acceleration structures of sufficient laser-excited potential for laser ion accelerators. In Relativistically Induced Transparency Acceleration (RITA) scheme, the heavy plasma-ions are fixed and only trace-density light-ions are accelerated. The relativistic critical layer and the acceleration structure move longitudinally forward by laser inducing transparency through apparent relativistic increase in electron mass. In the Radiation Pressure Acceleration (RPA) scheme, the whole plasma is longitudinally pushed forward under the action of the laser radiation pressure, possible only when plasma ions co-propagate with the laser front. In RPA, the acceleration structure velocity critically depends upon plasma-ion mass in addition to the laser intensity and plasma density. In RITA, mass of the heavy immobile plasma-ions does not affect the speed of the critical layer. Inertia of the bared immobile ions in RITA excites the charge separation potential, whereas RPA is not possible when ions are stationary

A Modified Porous Titanium Sheet Prepared by Plasma-Activated Sintering for Biomedical Applications

Directory of Open Access Journals (Sweden)

Yukimichi Tamaki

2010-01-01

Full Text Available This study aimed to develop a contamination-free porous titanium scaffold by a plasma-activated sintering within an originally developed TiN-coated graphite mold. The surface of porous titanium sheet with or without a coated graphite mold was characterized. The cell adhesion property of porous titanium sheet was also evaluated in this study. The peak of TiC was detected on the titanium sheet processed with the graphite mold without a TiN coating. Since the titanium fiber elements were directly in contact with the carbon graphite mold during processing, surface contamination was unavoidable event in this condition. The TiC peak was not detectable on the titanium sheet processed within the TiN-coated carbon graphite mold. This modified plasma-activated sintering with the TiN-coated graphite mold would be useful to fabricate a contamination-free titanium sheet. The number of adherent cells on the modified titanium sheet was greater than that of the bare titanium plate. Stress fiber formation and the extension of the cells were observed on the titanium sheets. This modified titanium sheet is expected to be a new tissue engineering material in orthopedic bone repair.

Consideration of beam plasma ion-source

International Nuclear Information System (INIS)

Sano, Fumimichi; Kusano, Norimasa; Ishida, Yoshihiro; Ishikawa, Junzo; Takagi, Toshinori

1976-01-01

Theoretical and experimental analyses and their comparison were made on the plasma generation and on the beam extraction for the beam plasma ion-source. The operational principle and the structure of the ion-source are explained in the first part. Considerations are given on the electron beam-plasma interaction and the resulting generation of high frequency or microwaves which in turn increases the plasma density. The flow of energy in this system is also explained in the second part. The relation between plasma density and the imaginary part of frequency is given by taking the magnetic flux density, the electron beam energy, and the electron beam current as parameters. The relations between the potential difference between collector and drift tube and the plasma density or the ion-current are also given. Considerations are also given to the change of the plasma density due to the change of the magnetic flux density at drift tube, the change of the electron beam energy, and the change of the electron beam current. The third part deals with the extraction characteristics of the ion beam. The structure of the multiple-aperture electrode and the relation between plasma density and the extracted ion current are explained. (Aoki, K.)

Transition of ion-acoustic perturbations in multicomponent plasma with negative ions

International Nuclear Information System (INIS)

Sharma, Sumita Kumari; Devi, Kavita; Adhikary, Nirab Chandra; Bailung, Heremba

2008-01-01

Evolution of ion-acoustic compressive (positive) and rarefactive (negative) perturbations in a multicomponent plasma with negative ions has been investigated in a double plasma device. Transition of compressive solitons in electron-positive ion plasma, into a dispersing train of oscillations in a multicomponent plasma, when the negative ion concentration r exceeds a critical value r c , has been observed. On the other hand, an initial rarefactive perturbation initially evolves into a dispersing train of oscillations in electron-positive ion plasma and transforms into rarefactive solitons in a multicomponent plasma when the negative ion concentration is higher than the critical value. The Mach velocity and width of the compressive and rarefactive solitons are measured. The compressive solitons in the range 0 c and the rarefactive solitons in the range r>r c have different characteristics than the Korteweg-de Vries (KdV) solitons at r=0 and modified KdV solitons at r=r c . A nonlinear differential equation having two terms to account for the lower and higher order nonlinearity has been used to explain the observed results

Observations of strong ion-ion correlations in dense plasmas

Energy Technology Data Exchange (ETDEWEB)

Ma, T.; Fletcher, L.; Pak, A.; Chapman, D. A.; Falcone, R. W.; Fortmann, C.; Galtier, E.; Gericke, D. O.; Gregori, G.; Hastings, J.; Landen, O. L.; Le Pape, S.; Lee, H. J.; Nagler, B.; Neumayer, P.; Turnbull, D.; Vorberger, J.; White, T. G.; Wünsch, K.; Zastrau, U.; Glenzer, S. H.; Döppner, T.

2014-05-01

Using simultaneous spectrally, angularly, and temporally resolved x-ray scattering, we measure the pronounced ion-ion correlation peak in a strongly coupled plasma. Laser-driven shock-compressed aluminum at ~3× solid density is probed with high-energy photons at 17.9 keV created by molybdenum He-α emission in a laser-driven plasma source. The measured elastic scattering feature shows a well-pronounced correlation peak at a wave vector of k=4k=4Å-1. The magnitude of this correlation peak cannot be described by standard plasma theories employing a linear screened Coulomb potential. Advanced models, including a strong short-range repulsion due to the inner structure of the aluminum ions are however in good agreement with the scattering data. These studies have demonstrated a new highly accurate diagnostic technique to directly measure the state of compression and the ion-ion correlations. We have since applied this new method in single-shot wave-number resolved S(k) measurements to characterize the physical properties of dense plasmas.

Adaptation of metal arc plasma source to plasma source ion implantation

International Nuclear Information System (INIS)

Shamim, M.M.; Fetherston, R.P.; Conrad, J.R.

1995-01-01

In Plasma Source Ion Implantation (PSII) a target is immersed in a plasma and a train of high negative voltage pulses is applied to accelerate ions into the target and to modify the properties in the near surface region. In PSII, until now the authors have been using gaseous species to generate plasmas. However metal ion plasma may be used to modify the surface properties of material for industrial applications. Conventionally the ion implantation of metal ions is performed using beam line accelerators which have complex engineering and high cost. The employment of a metal arc source to PSII has tremendous potential due to its ability to process the conformal surfaces, simple engineering and cost effectiveness. They have installed metal arc source for generation of titanium plasma. Currently, they are investigating the properties of titanium plasma and material behavior of titanium implanted aluminum and 52100 steel. The recent results of this investigation are presented

Plasma-based ion implantation and deposition: A review of physics,technology, and applications

Energy Technology Data Exchange (ETDEWEB)

Pelletier, Jacques; Anders, Andre

2005-05-16

After pioneering work in the 1980s, plasma-based ion implantation (PBII) and plasma-based ion implantation and deposition (PBIID) can now be considered mature technologies for surface modification and thin film deposition. This review starts by looking at the historical development and recalling the basic ideas of PBII. Advantages and disadvantages are compared to conventional ion beam implantation and physical vapor deposition for PBII and PBIID, respectively, followed by a summary of the physics of sheath dynamics, plasma and pulse specifications, plasma diagnostics, and process modeling. The review moves on to technology considerations for plasma sources and process reactors. PBII surface modification and PBIID coatings are applied in a wide range of situations. They include the by-now traditional tribological applications of reducing wear and corrosion through the formation of hard, tough, smooth, low-friction and chemically inert phases and coatings, e.g. for engine components. PBII has become viable for the formation of shallow junctions and other applications in microelectronics. More recently, the rapidly growing field of biomaterial synthesis makes used of PBII&D to produce surgical implants, bio- and blood-compatible surfaces and coatings, etc. With limitations, also non-conducting materials such as plastic sheets can be treated. The major interest in PBII processing originates from its flexibility in ion energy (from a few eV up to about 100 keV), and the capability to efficiently treat, or deposit on, large areas, and (within limits) to process non-flat, three-dimensional workpieces, including forming and modifying metastable phases and nanostructures. We use the acronym PBII&D when referring to both implantation and deposition, while PBIID implies that deposition is part of the process.

Current sheets and pressure anisotropy in the reconnection exhaust

International Nuclear Information System (INIS)

Le, A.; Karimabadi, H.; Roytershteyn, V.; Egedal, J.; Ng, J.; Scudder, J.; Daughton, W.; Liu, Y.-H.

2014-01-01

A particle-in-cell simulation shows that the exhaust during anti-parallel reconnection in the collisionless regime contains a current sheet extending 100 inertial lengths from the X line. The current sheet is supported by electron pressure anisotropy near the X line and ion anisotropy farther downstream. Field-aligned electron currents flowing outside the magnetic separatrices feed the exhaust current sheet and generate the out-of-plane, or Hall, magnetic field. Existing models based on different mechanisms for each particle species provide good estimates for the levels of pressure anisotropy. The ion anisotropy, which is strong enough to reach the firehose instability threshold, is also important for overall force balance. It reduces the outflow speed of the plasma

Current sheets and pressure anisotropy in the reconnection exhaust

Energy Technology Data Exchange (ETDEWEB)

Le, A.; Karimabadi, H.; Roytershteyn, V. [SciberQuest, Inc., Del Mar, California 92014 (United States); Egedal, J. [University of Wisconsin–Madison, Madison, Wisconsin 53706 (United States); Ng, J. [PPPL, Princeton University, Princeton, New Jersey 08543 (United States); Scudder, J. [University of Iowa, Iowa City, Iowa 52242 (United States); Daughton, W.; Liu, Y.-H. [Los Alamos National Laboratory, Los Alamos, New Mexico 87545 (United States)

2014-01-15

A particle-in-cell simulation shows that the exhaust during anti-parallel reconnection in the collisionless regime contains a current sheet extending 100 inertial lengths from the X line. The current sheet is supported by electron pressure anisotropy near the X line and ion anisotropy farther downstream. Field-aligned electron currents flowing outside the magnetic separatrices feed the exhaust current sheet and generate the out-of-plane, or Hall, magnetic field. Existing models based on different mechanisms for each particle species provide good estimates for the levels of pressure anisotropy. The ion anisotropy, which is strong enough to reach the firehose instability threshold, is also important for overall force balance. It reduces the outflow speed of the plasma.

Study of single and binary ion plasma expansion into laboratory-generated plasma wakes

International Nuclear Information System (INIS)

Wright, K.H. Jr.

1988-02-01

Plasma expansion into the wake of a large rectangular plate immersed in a collisionless, supersonic plasma was investigated in laboratory experiments. The experimental conditions address both single ion and binary ion plasma flows for the case of a body whose size is large in comparison with the Debye length, when the potential difference between the body and the plasma is relatively small. A new plasma source was developed to generate equi-velocity, binary ion plasma flows, which allows access to new parameter space that have previously been unavailable for laboratory studies. Specifically, the new parameters are the ionic mass ratio and the ionic component density ratio. In a series of experiments, a krypton-neon plasma is employed where the ambient density ratio of neon to krypton is varied more than an order of magnitude. The expansion in both the single ion and binary ion plasma cases is limited to early times, i.e., a few ion plasma periods, by the combination of plasma density, plasma drift speed, and vacuum chamber size, which prevented detailed comparison with self-similar theory

Dynamics of plasma ions motion in ultra-intense laser-excited plasma wakes

International Nuclear Information System (INIS)

Zhou Suyun; Li Jing

2013-01-01

The effects of heavy ions and protons motion in an ultra-intense laser-driven plasma wake are compared by rebuilding a plasma wake model. It is shown that with the same laser and plasma background electron density n 0 , the heavy ions' motion suppresses wake-field resonant excitation less than the protons' motion in their own plasma wake. Though heavy ions obtain more kinetic energy from the plasma wake, its energy density is less than that of the protons due to the ion density being far less than the proton density. As a result, the total energy of heavy ions obtained from the wake-field is far less than that of protons. The dependence of the kinetic energy and the energy density of protons and heavy ions on n 0 is discussed. (paper)

Helicon plasma ion temperature measurements and observed ion cyclotron heating in proto-MPEX

Science.gov (United States)

Beers, C. J.; Goulding, R. H.; Isler, R. C.; Martin, E. H.; Biewer, T. M.; Caneses, J. F.; Caughman, J. B. O.; Kafle, N.; Rapp, J.

2018-01-01

The Prototype-Material Plasma Exposure eXperiment (Proto-MPEX) linear plasma device is a test bed for exploring and developing plasma source concepts to be employed in the future steady-state linear device Material Plasma Exposure eXperiment (MPEX) that will study plasma-material interactions for the nuclear fusion program. The concept foresees using a helicon plasma source supplemented with electron and ion heating systems to reach necessary plasma conditions. In this paper, we discuss ion temperature measurements obtained from Doppler broadening of spectral lines from argon ion test particles. Plasmas produced with helicon heating alone have average ion temperatures downstream of the Helicon antenna in the range of 3 ± 1 eV; ion temperature increases to 10 ± 3 eV are observed with the addition of ion cyclotron heating (ICH). The temperatures are higher at the edge than the center of the plasma either with or without ICH. This type of profile is observed with electrons as well. A one-dimensional RF antenna model is used to show where heating of the plasma is expected.

Magnetospheric Multiscale Mission Observations of Magnetic Flux Ropes in the Earth's Plasma Sheet

Science.gov (United States)

Slavin, J. A.; Akhavan-Tafti, M.; Poh, G.; Le, G.; Russell, C. T.; Nakamura, R.; Baumjohann, W.; Torbert, R. B.; Gershman, D. J.; Pollock, C. J.; Giles, B. L.; Moore, T. E.; Burch, J. L.

2017-12-01

A major discovery by the Cluster mission and the previous generation of science missions is the presence of earthward and tailward moving magnetic flux ropes in the Earth's plasma sheet. However, the lack of high-time resolution plasma measurements severely limited progress concerning the formation and evolution of these reconnection generated structures. We use high-time resolution magnetic and electric field and plasma measurements from the Magnetospheric Multiscale mission's first tail season to investigate: 1) the distribution of flux rope diameters relative to the local ion and electron inertial lengths; 2) the internal force balance sustaining these structures; and 3) the magnetic connectivity of the flux ropes to the Earth and/or the interplanetary medium; 4) the specific entropy of earthward moving flux ropes and the possible effect of "buoyancy" on how deep they penetrate into the inner magnetosphere; and 5) evidence for coalescence of adjacent flux ropes and/or the division of existing flux ropes through the formation of secondary X-lines. The results of these initial analyses will be discussed in terms of their implications for reconnection-driven magnetospheric dynamics and substorms.

Ion-beam Plasma Neutralization Interaction Images

Energy Technology Data Exchange (ETDEWEB)

Igor D. Kaganovich; Edward Startsev; S. Klasky; Ronald C. Davidson

2002-04-09

Neutralization of the ion beam charge and current is an important scientific issue for many practical applications. The process of ion beam charge and current neutralization is complex because the excitation of nonlinear plasma waves may occur. Computer simulation images of plasma neutralization of the ion beam pulse are presented.

Ion-beam Plasma Neutralization Interaction Images

International Nuclear Information System (INIS)

Igor D. Kaganovich; Edward Startsev; S. Klasky; Ronald C. Davidson

2002-04-01

Neutralization of the ion beam charge and current is an important scientific issue for many practical applications. The process of ion beam charge and current neutralization is complex because the excitation of nonlinear plasma waves may occur. Computer simulation images of plasma neutralization of the ion beam pulse are presented

The plasma sheet and boundary layers under northward IMF: A multi-point and multi-instrument perspective

Czech Academy of Sciences Publication Activity Database

Taylor, M. G. G. T.; Lavraud, B.; Escoubet, C. P.; Milan, S.E.; Nykyri, K.; Dunlop, M. W.; Davies, J.A.; Friedel, R.H.W.; Frey, H.; Bogdanova, Y.V.; Asnes, A.; Laakso, H.; Trávníček, Pavel M.; Masson, A.; Opgenoorth, H.; Vallat, C.; Fazakerley, A. N.; Lahiff, A.; Owen, C. J.; Pitout, F.; Pu, Y.; Shen, C.; Zong, Q.-G.; Rème, H.; Scudder, J. D.; Zhang, T. L.

2008-01-01

Roč. 41, č. 10 (2008), s. 1619-1629 ISSN 0273-1177 Institutional research plan: CEZ:AV0Z10030501 Keywords : plasma sheet * magnetopshere * cold dense plasma sheet Subject RIV: BN - Astronomy, Celestial Mechanics, Astrophysics Impact factor: 0.860, year: 2008

Nonlinear Plasma Waves Excitation by Intense Ion Beams in Background Plasma

International Nuclear Information System (INIS)

Kaganovich, Igor D.; Startsev, Edward A.; Davidson, Ronald C.

2004-01-01

Plasma neutralization of an intense ion pulse is of interest for many applications, including plasma lenses, heavy ion fusion, cosmic ray propagation, etc. An analytical electron fluid model has been developed to describe the plasma response to a propagating ion beam. The model predicts very good charge neutralization during quasi-steady-state propagation, provided the beam pulse duration τ b is much longer than the electron plasma period 2π/ω p , where ω p = (4πe 2 n p /m) 1/2 is the electron plasma frequency and n p is the background plasma density. In the opposite limit, the beam pulse excites large-amplitude plasma waves. If the beam density is larger than the background plasma density, the plasma waves break. Theoretical predictions are compared with the results of calculations utilizing a particle-in-cell (PIC) code. The cold electron fluid results agree well with the PIC simulations for ion beam propagation through a background plasma. The reduced fluid description derived in this paper can provide an important benchmark for numerical codes and yield scaling relations for different beam and plasma parameters. The visualization of numerical simulation data shows complex collective phenomena during beam entry and exit from the plasma

Nonlinear plasma waves excitation by intense ion beams in background plasma

International Nuclear Information System (INIS)

Kaganovich, Igor D.; Startsev, Edward A.; Davidson, Ronald C.

2004-01-01

Plasma neutralization of an intense ion pulse is of interest for many applications, including plasma lenses, heavy ion fusion, cosmic ray propagation, etc. An analytical electron fluid model has been developed to describe the plasma response to a propagating ion beam. The model predicts very good charge neutralization during quasi-steady-state propagation, provided the beam pulse duration τ b is much longer than the electron plasma period 2π/ω p , where ω p =(4πe 2 n p /m) 1/2 is the electron plasma frequency, and n p is the background plasma density. In the opposite limit, the beam pulse excites large-amplitude plasma waves. If the beam density is larger than the background plasma density, the plasma waves break. Theoretical predictions are compared with the results of calculations utilizing a particle-in-cell (PIC) code. The cold electron fluid results agree well with the PIC simulations for ion beam propagation through a background plasma. The reduced fluid description derived in this paper can provide an important benchmark for numerical codes and yield scaling relations for different beam and plasma parameters. The visualization of numerical simulation data shows complex collective phenomena during beam entry and exit from the plasma

Plasma focus as an heavy ion source in the problem of heavy ion fusion

International Nuclear Information System (INIS)

Gribkov, V.A.; Dubrovskij, A.V.; Kalachev, N.V.; Krokhin, O.N.; Silin, P.V.; Nikulin, V.Ya.; Cheblukov, Yu.N.

1984-01-01

Results of experiments on the ion flux formation in a plasma focus (PF) to develop a multicharged ion source for thermonuclear facility driver are presented. In plasma focus accelerating section copper ions were injected. Advantages of the suggested method of ion beam formation are demonstrated. Beam emittance equalling < 0.1 cmxmrad is obtained. Plasma focus ion energy exceeds 1 MeV. Plasma focus in combination with a neodymium laser is thought to be a perspective ion source for heavy ion fusion

Energization of the Ring Current through Convection of Substorm Enhancements of the Plasma Sheet Source.

Science.gov (United States)

Menz, A.; Kistler, L. M.; Mouikis, C.; Spence, H. E.; Henderson, M. G.; Matsui, H.

2017-12-01

It has been shown that electric field strength and night-side plasma sheet density are the two best predictors of the adiabatic energy gain of the ring current during geomagnetic storms (Liemohn and Khazanov, 2005). While H+ dominates the ring current during quiet times, O+ can contribute substantially during geomagnetic storms. Substorm activity provides a mechanism to enhance the energy density of O+ in the plasma sheet during geomagnetic storms, which is then convected adiabatically into the inner-magnetosphere. Using the Van Allen Probes data in the the plasma sheet source region (defined as L>5.5 during storms) and the inner magnetosphere, along with LANL-GEO data to identify substorm injection times, we show that adiabatic convection of O+ enhancements in the source region can explain the observed enhancements in the inner magnetosphere. We use the UNH-IMEF electric field model to calculate drift times from the source region to the inner magnetosphere to test whether enhancements in the inner-magnetosphere can be explained by dipolarization driven enhancements in the plasma sheet source hours before.

The quiet evening auroral arc and the structure of the growth phase near-Earth plasma sheet

Science.gov (United States)

Coroniti, F. V.; Pritchett, P. L.

2014-03-01

The plasma pressure and current configuration of the near-Earth plasma sheet that creates and sustains the quiet evening auroral arc during the growth phase of magnetospheric substorms is investigated. We propose that the quiet evening arc (QEA) connects to the thin near-Earth current sheet, which forms during the development of the growth phase enhancement of convection. The current sheet's large polarization electric fields are shielded from the ionosphere by an Inverted-V parallel potential drop, thereby producing the electron precipitation responsible for the arc's luminosity. The QEA is located in the plasma sheet region of maximal radial pressure gradient and, in the east-west direction, follows the vanishing of the approximately dawn-dusk-directed gradient or fold in the plasma pressure. In the evening sector, the boundary between the Region1 and Region 2 current systems occurs where the pressure maximizes (approximately radial gradient of the pressure vanishes) and where the approximately radial gradient of the magnetic flux tube volume also vanishes in an inflection region. The proposed intricate balance of plasma sheet pressure and currents may well be very sensitive to disruption by the arrival of equatorward traveling auroral streamers and their associated earthward traveling dipolarization fronts.

Occurrence and location of concentrated load and generator regions observed by Cluster in the plasma sheet

Directory of Open Access Journals (Sweden)

M. Hamrin

2009-11-01

Full Text Available Here, and in a companion paper by Hamrin et al. (2009 [Scale size and life time of energy conversion regions observed by Cluster in the plasma sheet], we investigate localized energy conversion regions (ECRs in the Earth's plasma sheet. In total we have studied 151 ECRs within 660 h of plasma sheet data from the summer and fall of 2001 when Cluster was close to apogee at an altitude of about 15–20 R_E. Cluster offers appropriate conditions for the investigation of energy conversion by the evaluation of the power density, E·J, where E is the electric field and J the current density. From the sign of the power density, we have identified more than three times as many Concentrated Load Regions (CLRs as Concentrated Generator Regions (CGRs. We also note that the CLRs appear to be stronger. To our knowledge, these are the first in situ observations confirming the general notion of the plasma sheet, on the average, behaving as a load. At the same time the plasma sheet appears to be highly structured, with energy conversion occurring in both directions between the fields and the particles. From our data we also find that the CLRs appear to be located closer to the neutral sheet, while CGRs prefer locations towards the plasma sheet boundary layer (PSBL. For both CLRs and CGRs, E and J in the GSM y (cross-tail direction dominate the total power density, even though the z contribution occasionally can be significant. The prevalence of the y-direction seems to be weaker for the CGRs, possibly related to a higher fluctuation level near the PSBL.

On plasma ion beam formation in the Advanced Plasma Source

International Nuclear Information System (INIS)

Harhausen, J; Foest, R; Hannemann, M; Ohl, A; Brinkmann, R P; Schröder, B

2012-01-01

The Advanced Plasma Source (APS) is employed for plasma ion-assisted deposition (PIAD) of optical coatings. The APS is a hot cathode dc glow discharge which emits a plasma ion beam to the deposition chamber at high vacuum (p ≲ 2 × 10 −4 mbar). It is established as an industrial tool but to date no detailed information is available on plasma parameters in the process chamber. As a consequence, the details of the generation of the plasma ion beam and the reasons for variations of the properties of the deposited films are barely understood. In this paper the results obtained from Langmuir probe and retarding field energy analyzer diagnostics operated in the plasma plume of the APS are presented, where the source was operated with argon. With increasing distance to the source exit the electron density (n e ) is found to drop by two orders of magnitude and the effective electron temperature (T e,eff ) drops by a factor of five. The parameters close to the source region read n e ≳ 10 11 cm −3 and T e,eff ≳ 10 eV. The electron distribution function exhibits a concave shape and can be described in the framework of the non-local approximation. It is revealed that an energetic ion population leaves the source region and a cold ion population in the plume is build up by charge exchange collisions with the background neutral gas. Based on the experimental data a scaling law for ion beam power is deduced, which links the control parameters of the source to the plasma parameters in the process chamber. (paper)

A study of single and binary ion plasma expansion into laboratory-generated plasma wakes

Science.gov (United States)

Wright, Kenneth Herbert, Jr.

1988-01-01

Plasma expansion into the wake of a large rectangular plate immersed in a collisionless, supersonic plasma was investigated in laboratory experiments. The experimental conditions address both single ion and binary ion plasma flows for the case of a body whose size is large in comparison with the Debye length, when the potential difference between the body and the plasma is relatively small. A new plasma source was developed to generate equi-velocity, binary ion plasma flows, which allows access to new parameter space that have previously been unavailable for laboratory studies. Specifically, the new parameters are the ionic mass ratio and the ionic component density ratio. In a series of experiments, a krypton-neon plasma is employed where the ambient density ratio of neon to krypton is varied more than an order of magnitude. The expansion in both the single ion and binary ion plasma cases is limited to early times, i.e., a few ion plasma periods, by the combination of plasma density, plasma drift speed, and vacuum chamber size, which prevented detailed comparison with self-similar theory.

Ion plasma electron gun

International Nuclear Information System (INIS)

Wakalopulos, G.

1976-01-01

In the disclosed electron gun positive ions generated by a hollow cathode plasma discharge in a first chamber are accelerated through control and shield grids into a second chamber containing a high voltage cold cathode. These positive ions bombard a surface of the cathode causing the cathode to emit secondary electrons which form an electron beam having a distribution adjacent to the cathode emissive surface substantially the same as the distribution of the ion beam impinging upon the cathode. After passing through the grids and the plasma discharge chamber, the electron beam exits from the electron gun via a foil window. Control of the generated electron beam is achieved by applying a relatively low control voltage between the control grid and the electron gun housing (which resides at ground potential) to control the density of the positive ions bombarding the cathode

Understanding the anisotropic ion distributions within magnetotail dipolarizing flux bundles

Science.gov (United States)

Zhou, X.; Runov, A.; Angelopoulos, V.; Birn, J.

2017-12-01

Dipolarizing flux bundles (DFBs), earthward-propagating structures with enhanced northward magnetic field (Bz) component, are usually believed to carry a different plasma population from that in the ambient magnetotail plasma sheet. The ion distribution functions within the DFB, however, are recently found to be largely controlled by the ion adiabaticity parameter κ in the ambient plasma sheet outside the DFBs. According to these observations, the ambient κ values of 2-3 usually correspond to a strong perpendicular anisotropy of suprathermal ions within the DFBs, whereas for lower κ values the ions inside the DFBs become more isotropic. Here we utilize a simple, test-particle model to explore the nature of the anisotropy and its dependence on the ambient κ values. We find that the ion anisotropy originates from successive ion reflections and reentries to the DFBs, during which the ions can be consecutively accelerated in the perpendicular direction by the DFB-carried electric field. This acceleration process may be interrupted, however, when the magnetic field lines are highly curved in the ambient plasma sheet. In this case, the ion trajectories are most stochastic outside the DFB region, which makes the reflected ions less likely to return to the DFBs for another cycle of acceleration; as a consequence, the perpendicular ion anisotropy does not appear. Given that the DFB ions are a free energy source for instabilities when they are injected towards Earth, our simple model (that reproduces most observational features on the anisotropic DFB ion distributions) may shed new lights on the coupling process between the magnetotail and the inner magneosphere.

Turbulent ion heating in TCV Tokamak plasmas

International Nuclear Information System (INIS)

Schlatter, Ch.

2009-08-01

The Tokamak à configuration variable (TCV) features the highest electron cyclotron wave power density available to resonantly heat (ECRH) the electrons and to drive noninductive currents in a fusion grade plasma (ECCD). In more than 15 years of exploitation, much effort has been expended on real and velocity space engineering of the plasma electron energy distribution function and thus making electron physics a major research contribution of TCV. When a plasma was first subjected to ECCD, a surprising energisation of the ions, perpendicular to the confining magnetic field, was observed on the charge exchange spectrum measured with the vertical neutral particle analyser (VNPA). It was soon concluded that the ion acceleration was not due to power equipartition between electrons and ions, which, due to the absence of direct ion heating on TCV, has thus far been considered as the only mechanism heating the ions. However, although observed for more than ten years, little attention was paid to this phenomenon, whose cause has remained unexplained to date. The key subject of this thesis is the experimental study of this anomalous ion acceleration, the characterisation in terms of relevant parameters and the presentation of a model simulation of the potential process responsible for the appearance of fast ions. The installation of a new compact neutral particle analyser (CNPA) with an extended high energy range (≥ 50 keV) greatly improved the fast ion properties diagnosis. The CNPA was commissioned and the information derived from its measurement (ion temperature and density, isotopic plasma composition) was validated against other ion diagnostics, namely the active carbon charge exchange recombination spectroscopy system (CXRS) and a neutron counter. In ohmic plasmas, where the ion heating agrees with classical theory, the radial ion temperature profile was successfully reconstructed by vertically displacing the plasma across the horizontal CNPA line of sight. Active

Electric force on plasma ions and the momentum of the ion-neutrals flow

Science.gov (United States)

Makrinich, G.; Fruchtman, A.; Zoler, D.; Boxman, R. L.

2018-05-01

The electric force on ions in plasma and the momentum flux carried by the mixed ion-neutral flow were measured and found to be equal. The experiment was performed in a direct-current gas discharge of cylindrical geometry with applied radial electric field and axial magnetic field. The unmagnetized plasma ions, neutralized by magnetized electrons, were accelerated radially outward transferring part of the gained momentum to neutrals. Measurements were taken for various argon gas flow rates between 13 and 100 Standard Cubic Centimeter per Minute, for a discharge current of 1.9 A and a magnetic field intensity of 136 G. The plasma density, electron temperature, and plasma potential were measured at various locations along the flow. These measurements were used to determine the local electric force on the ions. The total electric force on the plasma ions was then determined by integrating radially the local electric force. In parallel, the momentum flux of the mixed ion-neutral flow was determined by measuring the force exerted by the flow on a balance force meter (BFM). The maximal plasma density was between 6 × 1010 cm-3 and 5 × 1011 cm-3, the maximal electron temperature was between 8 eV and 25 eV, and the deduced maximal electric field was between 2200 V/m and 5800 V/m. The force exerted by the mixed ion-neutral flow on the BFM agreed with the total electric force on the plasma ions. This agreement showed that it is the electric force on the plasma ions that is the source of the momentum acquired by the mixed ion-neutral flow.

Some properties of ion and cluster plasma

International Nuclear Information System (INIS)

Gudzenko, L.I.; Derzhiev, V.I.; Yakovlenko, S.I.

1982-01-01

The aggregate of problems connected with the physics of ion and cluster plasma is qualitatively considered. Such a plasma can exist when a dense gas is ionized by a hard ionizer. The conditions for the formation of an ion plasma and the difference between its characteristics and those of an ordinary electron plasma are discussed; a solvated-ion model and the distribution of the clusters with respect to the number of solvated molecules are considered. The recombination rate of the positively and negatively charged clusters is roughly estimated. The parameters of a ball-lightning plasma are estimated on the basis of the cluster model

Current control for magnetized plasma in direct-current plasma-immersion ion implantation

International Nuclear Information System (INIS)

Tang Deli; Chu, Paul K.

2003-01-01

A method to control the ion current in direct-current plasma-immersion ion implantation (PIII) is reported for low-pressure magnetized inductively coupled plasma. The ion current can be conveniently adjusted by applying bias voltage to the conducting grid that separates plasma formation and implantation (ion acceleration) zones without the need to alter the rf input power, gas flux, or other operating conditions. The ion current that diminishes with an increase in grid bias in magnetized plasmas can be varied from 48 to 1 mA by increasing the grid voltage from 0 to 70 V at -50 kV sample bias and 0.5 mTorr hydrogen pressure. High implantation voltage and monoenergetic immersion implantation can now be achieved by controlling the ion current without varying the macroscopic plasma parameters. The experimental results and interpretation of the effects are presented in this letter. This technique is very attractive for PIII of planar samples that require on-the-fly adjustment of the implantation current at high implantation voltage but low substrate temperature. In some applications such as hydrogen PIII-ion cut, it may obviate the need for complicated sample cooling devices that must work at high voltage

Suprathermal ion transport in turbulent magnetized plasmas

International Nuclear Information System (INIS)

Bovet, A. D.

2015-01-01

Suprathermal ions, which have an energy greater than the quasi-Maxwellian background plasma temperature, are present in many laboratory and astrophysical plasmas. In fusion devices, they are generated by the fusion reactions and auxiliary heating. Controlling their transport is essential for the success of future fusion devices that could provide a clean, safe and abundant source of electric power to our society. In space, suprathermal ions include energetic solar particles and cosmic rays. The understanding of the acceleration and transport mechanisms of these particles is still incomplete. Basic plasma devices allow detailed measurements that are not accessible in astrophysical and fusion plasmas, due to the difficulty to access the former and the high temperatures of the latter. The basic toroidal device TORPEX offers an easy access for diagnostics, well characterized plasma scenarios and validated numerical simulations of its turbulence dynamics, making it the ideal platform for the investigation of suprathermal ion transport. This Thesis presents three-dimensional measurements of a suprathermal ion beam injected in turbulent TORPEX plasmas. The combination of uniquely resolved measurements and first principle numerical simulations reveals the general non-diffusive nature of the suprathermal ion transport. A precise characterization of their transport regime shows that, depending on their energies, suprathermal ions can experience either a super diffusive transport or a subdiffusive transport in the same background turbulence. The transport character is determined by the interaction of the suprathermal ion orbits with the turbulent plasma structures, which in turn depends on the ratio between the ion energy and the background plasma temperature. Time-resolved measurements reveal a clear difference in the intermittency of suprathermal ions time-traces depending on the transport regime they experience. Conditionally averaged measurements uncover the influence of

Compressional wave events in the dawn plasma sheet observed by Interball-1

Directory of Open Access Journals (Sweden)

O. Verkhoglyadova

1999-09-01

Full Text Available Compressional waves with periods greater than 2 min (about 10-30 min at low geomagnetic latitudes, namely compressional Pc5 waves, are studied. The data set obtained with magnetometer MIF-M and plasma analyzer instrument CORALL on board the Interball-1 are analyzed. Measurements performed in October 1995 and October 1996 in the dawn plasma sheet at -30 RE ≤ XGSM and |ZGSM| ≤ 10 RE are considered. Anti-phase variations of magnetic field and ion plasma pressures are analyzed by searching for morphological similarities in the two time series. It is found that longitudinal and transverse magnetic field variations with respect to the background magnetic field are of the same order of magnitude. Plasma velocities are processed for each time period of the local dissimilarity in the pressure time series. Velocity disturbances occur mainly transversely to the local field line. The data reveal the rotation of the velocity vector. Because of the field line curvature, there is no fixed position of the rotational plane in the space. These vortices are localized in the regions of anti-phase variations of the magnetic field and plasma pressures, and the vortical flows are associated with the compressional Pc5 wave process. A theoretical model is proposed to explain the main features of the nonlinear wave processes. Our main goal is to study coupling of drift Alfven wave and magnetosonic wave in a warm inhomogeneous plasma. A vortex is the partial solution of the set of the equations when the compression is neglected. A compression effect gives rise to a nonlinear soliton-like solution.Key words. Magnetosphere physics (magnetotail · Space plasma physics (kinetic and MHD theory; non-linear phenomena

Ion species stratification within strong shocks in two-ion plasmas

Science.gov (United States)

Keenan, Brett D.; Simakov, Andrei N.; Taitano, William T.; Chacón, Luis

2018-03-01

Strong collisional shocks in multi-ion plasmas are featured in many environments, with Inertial Confinement Fusion (ICF) experiments being one prominent example. Recent work [Keenan et al., Phys. Rev. E 96, 053203 (2017)] answered in detail a number of outstanding questions concerning the kinetic structure of steady-state, planar plasma shocks, e.g., the shock width scaling by the Mach number, M. However, it did not discuss shock-driven ion-species stratification (e.g., relative concentration modification and temperature separation). These are important effects since many recent ICF experiments have evaded explanation by standard, single-fluid, radiation-hydrodynamic (rad-hydro) numerical simulations, and shock-driven fuel stratification likely contributes to this discrepancy. Employing the state-of-the-art Vlasov-Fokker-Planck code, iFP, along with multi-ion hydro simulations and semi-analytics, we quantify the ion stratification by planar shocks with the arbitrary Mach number and the relative species concentration for two-ion plasmas in terms of ion mass and charge ratios. In particular, for strong shocks, we find that the structure of the ion temperature separation has a nearly universal character across ion mass and charge ratios. Additionally, we find that the shock fronts are enriched with the lighter ion species and the enrichment scales as M4 for M ≫ 1.

Ion mobility: its role in plasma chromatography

International Nuclear Information System (INIS)

Mason, E.A.

1984-01-01

This paper is a review of the basic physical theory underlying plasma chromatography. Essentially, plasma chromatography simply measures ion mobility. The new feature of plasma chromatography, as compared to aqueous electrophoresis, is the existence of a highly-developed and accurate body of theory that connects gaseous ion mobility and diffusion to the ion molecule interactions in the drift tube. Attention is restricted to phenomena occurring in the drift tube portion of the apparatus

Ion-acoustic double layers in multi-species plasmas maintained by negative ions

International Nuclear Information System (INIS)

Verheest, F.

1989-01-01

A study is made of ion-acoustic double layers in a plasma consisting of any number of cold positive and negative ion (and cold electron) species in addition to one isothermal electron population. The Sagdeev potential is obtained in general, together with limits on both compressive and rarefactive solutions for ion-acoustic double layers and/or solitons. Weak ion-acoustic double layers are described by a modified Korteweg-de Vries equation. Such double layers are not possible in plasmas with only positive ion species and one electron population. When one or more negative ion and/or cold electron species are included above a certain threshold density, rarefactive ion-acoustic double layers occur, but no compressive ones. The double-layer form of the potential is given, together with an application to a plasma with one positive and one negative ion component. It is shown that there is indeed such a threshold density for the negative ion density, depending on the charge-to-mass ratios of both types of ions. The threshold density is determined numerically for a range of such ratios and discussed in view of possible relevance to auroral and experimental plasmas. In the discussion, cold electrons can play the role of the negative ion species. (author)

Negative ion surface plasma source development for plasma trap injectors in Novosibirsk

International Nuclear Information System (INIS)

Bel'chenko, Yu.I.; Dimov, G.I.; Dudnikov, V.G.; Kupriyanov, A.S.

1989-01-01

Work on high-current ion sources carried out at the Novosibirsk Institute of Nuclear Physics (INP) is presented. The INP investigations on ''pure plasma'' planotron and ''pure surface'' secondary emission systems of H - generation, which preceded the surface-plasma concept developed in Novosibirsk, are described. The physical basis of the surface-plasma method of negative-ion production is considered. The versions and operating characteristics of different surface-plasma sources including the multi-ampere (approx-gt 10A) source are discussed. Research on efficient large-area (∼10 2 cm 2 ) negative ion surface-plasma emitters is described. The INP long-pulse multiaperture surface- plasma generators, with a current of about 1A, are described. 38 refs., 17 figs

Tailored ion energy distributions on plasma electrodes

International Nuclear Information System (INIS)

Economou, Demetre J.

2013-01-01

As microelectronic device features continue to shrink approaching atomic dimensions, control of the ion energy distribution on the substrate during plasma etching and deposition becomes increasingly critical. The ion energy should be high enough to drive ion-assisted etching, but not too high to cause substrate damage or loss of selectivity. In many cases, a nearly monoenergetic ion energy distribution (IED) is desired to achieve highly selective etching. In this work, the author briefly reviews: (1) the fundamentals of development of the ion energy distribution in the sheath and (2) methods to control the IED on plasma electrodes. Such methods include the application of “tailored” voltage waveforms on an electrode in continuous wave plasmas, or the application of synchronous bias on a “boundary electrode” during a specified time window in the afterglow of pulsed plasmas

Ion-beam plasma and propagation of intense compensated ion beams

Energy Technology Data Exchange (ETDEWEB)

Gabovich, M D [AN Ukrainskoj SSR, Kiev. Inst. Fiziki

1977-02-01

Discussed are the results of investigation of plasma properties received by neutralization of intense ion beam space charge. Considered is the process of ion beam compensation by charges, formed as a result of gas ionization by this beam or by externally introduced ones. Emphasis is placed on collective phenomena in ion-beam plasma, in particular on non-linear effects limiting amplitude of oscillations. It is shown that not only dynamic decompensation but the Coulomb collisions of ions with electrons as well as other collective oscillations significantly affects the propagation of compensated ion beams. All the processes are to be taken into account in solving the problem of obtaining ''superdense'' compensated beams.

Ion-beam plasma and propagation of intense compensated ion beams

International Nuclear Information System (INIS)

Gabovich, M.D.

1977-01-01

Discussed are the results of investigation of plasma properties recieved by neutralization of intensive ion beam space charge. Considered is the process of ion beam compensation by charges, formed as a result of gas ionization by this beam or by externally introduced ones. Emphasis is placed on collective phenomena in ion-beam plasma, in particular on non-linear effects limiting amplitude of oscillations. It is shown, that not only dinamic decompensation but the Coulomb collisions of ions with electrons as well as other collective oscillations significantly affects the propagation of compensated ion beams. All the processes are to be taken into account at solving the problem of obtaining ''superdense'' compensated beams

Scale size and life time of energy conversion regions observed by Cluster in the plasma sheet

Directory of Open Access Journals (Sweden)

M. Hamrin

2009-11-01

Full Text Available In this article, and in a companion paper by Hamrin et al. (2009 [Occurrence and location of concentrated load and generator regions observed by Cluster in the plasma sheet], we investigate localized energy conversion regions (ECRs in Earth's plasma sheet. From more than 80 Cluster plasma sheet crossings (660 h data at the altitude of about 15–20 RE in the summer and fall of 2001, we have identified 116 Concentrated Load Regions (CLRs and 35 Concentrated Generator Regions (CGRs. By examining variations in the power density, E·J, where E is the electric field and J is the current density obtained by Cluster, we have estimated typical values of the scale size and life time of the CLRs and the CGRs. We find that a majority of the observed ECRs are rather stationary in space, but varying in time. Assuming that the ECRs are cylindrically shaped and equal in size, we conclude that the typical scale size of the ECRs is 2 RE≲ΔSECR≲5 RE. The ECRs hence occupy a significant portion of the mid altitude plasma sheet. Moreover, the CLRs appear to be somewhat larger than the CGRs. The life time of the ECRs are of the order of 1–10 min, consistent with the large scale magnetotail MHD simulations of Birn and Hesse (2005. The life time of the CGRs is somewhat shorter than for the CLRs. On time scales of 1–10 min, we believe that ECRs rise and vanish in significant regions of the plasma sheet, possibly oscillating between load and generator character. It is probable that at least some of the observed ECRs oscillate energy back and forth in the plasma sheet instead of channeling it to the ionosphere.

Sausage mode instability of thin current sheets as a cause of magnetospheric substorms

Directory of Open Access Journals (Sweden)

J. Büchner

Full Text Available Observations have shown that, prior to substorm explosions, thin current sheets are formed in the plasma sheet of the Earth's magnetotail. This provokes the question, to what extent current-sheet thinning and substorm onsets are physically, maybe even causally, related. To answer this question, one has to understand the plasma stability of thin current sheets. Kinetic effects must be taken into account since particle scales are reached in the course of tail current-sheet thinning. We present the results of theoretical investigations of the stability of thin current sheets and about the most unstable mode of their decay. Our conclusions are based upon a non-local linear dispersion analysis of a cross-magnetic field instability of Harris-type current sheets. We found that a sausage-mode bulk current instability starts after a sheet has thinned down to the ion inertial length. We also present the results of three-dimensional electromagnetic PIC-code simulations carried out for mass ratios up to M_i / m_e=64. They verify the linearly predicted properties of the sausage mode decay of thin current sheets in the parameter range of interest.

Key words. Magnetospheric physics (plasma waves and instabilities; storms and substorms · Space plasma physics (magnetic reconnection

Dynamic plasma screening effects on electron capture process in hydrogenic ion fully stripped ion collisions in dense plasmas

International Nuclear Information System (INIS)

Jung, Y.

1997-01-01

In dense plasmas, dynamic plasma screening effects are investigated on electron capture from hydrogenic ions by past fully stripped ions. The classical Bohr Lindhard model has been applied to obtain the electron capture probability. The interaction potential in dense plasmas is represented in terms of the longitudinal dielectric function. The classical straight-line trajectory approximation is applied to the motion of the projectile ion in order to visualize the electron capture probability as a function of the impact parameter, projectile energy, and plasma parameters. The electron capture probability including the dynamic plasma screening effect is always greater than that including the static plasma screening effect. When the projectile velocity is smaller than the electron thermal velocity, the dynamic polarization screening effect becomes the static plasma screening effect. When the projectile velocity is greater than the plasma electron thermal velocity, the interaction potential is almost unshielded. The difference between the dynamic and static plasma screening effects is more significant for low energy projectiles. It is found that the static screening formula obtained by the Debye Hueckel model overestimates the plasma screening effects on the electron capture processes in dense plasmas. copyright 1997 American Institute of Physics

Plasma immersion ion implantation into insulating materials

International Nuclear Information System (INIS)

Tian Xiubo; Yang Shiqin

2006-01-01

Plasma immersion ion implantation (PIII) is an effective surface modification tool. During PIII processes, the objects to be treated are immersed in plasmas and then biased to negative potential. Consequently the plasma sheath forms and ion implantation may be performed. The pre-requirement of plasma implantation is that the object is conductive. So it seems difficult to treat the insulating materials. The paper focuses on the possibilities of plasma implantation into insulting materials and presents some examples. (authors)

Studies of electron cyclotron resonance ion source plasma physics

International Nuclear Information System (INIS)

Tarvainen, O.

2005-01-01

This thesis consists of an introduction to the plasma physics of electron cyclotron resonance ion sources (ECRIS) and a review of the results obtained by the author and co-workers including discussion of related work by others. The thesis begins with a theoretical discussion dealing with plasma physics relevant for the production of highly charged ions in ECR ion source plasmas. This is followed by an overview of different techniques, such as gas mixing and double frequency heating, that can be used to improve the performance of this type of ion source. The experimental part of the work consists of studies related to ECRIS plasma physics. The effect of the gas mixing technique on the production efficiency of different ion beams was studied with both gaseous and solid materials. It was observed that gas mixing improves the confinement of the heavier element while the confinement of the lighter element is reduced. When the effect of gas mixing on MIVOC-plasmas was studied with several mixing gases it was observed that applying this technique can reduce the inevitable carbon contamination by a significant factor. In order to understand the different plasma processes taking place in ECRIS plasmas, a series of plasma potential and emittance measurements was carried out. An instrument, which can be used to measure the plasma potential in a single measurement without disturbing the plasma, was developed for this work. Studying the plasma potential of ECR ion sources is important not only because it helps to understand different plasma processes, but also because the information can be used as an input parameter for beam transport simulations and ion source extraction design. The experiments performed have revealed clear dependencies of the plasma potential on certain source parameters such as the amount of carbon contamination accumulated on the walls of the plasma chamber during a MIVOC-run. It was also observed that gas mixing affects not only the production efficiency

Non-Uniformity of Ion Implantation in Direct-Current Plasma Immersion Ion Implantation

International Nuclear Information System (INIS)

Cheng-Sen, Liu; Yu-Jia, Fan; Nan, Zhang; Li, Guan; Yuan, Yao; De-Zhen, Wang

2010-01-01

A particle-in-cell simulation is developed to study dc plasma immersion ion implantation. Particular attention is paid to the influence of the voltage applied to the target on the ion path, and the ion flux distribution on the target surface. It is found that the potential near the aperture within the plasma region is not the plasma potential, and is impacted by the voltage applied to the implanted target. A curved equipotential contour expands into the plasma region through the aperture and the extent of the expansion depends on the voltage. Ions accelerated by the electric field in the sheath form a beam shape and a flux distribution on the target surface, which are strongly dependent on the applied voltage. The results of the simulations demonstrate the formation mechanism of the grid-shadow effect, which is in agreement with the result observed experimentally. (physics of gases, plasmas, and electric discharges)

Ion acceleration in the plasma source sheath

International Nuclear Information System (INIS)

Birdsall, C.K.

1986-01-01

This note is a calculation of the potential drop for a planar plasma source, across the source sheath, into a uniform plasma region defined by vector E = 0 and/or perhaps ∂ 2 PHI/∂ x 2 = 0. The calculation complements that of Bohm who obtained the potential drop at the other end of a plasma, at a planar collector sheath. The result is a relation between the source ion flux and the source sheath potential drop and the accompanying ion acceleration. This planar source sheath ion acceleration mechanism (or that from a distributed source) can provide the pre-collector-sheath ion acceleration as found necessary by Bohm. 3 refs

A triggering of solar flare by magnetosonic waves in a neutral sheet plasma

International Nuclear Information System (INIS)

Sakai, Jun-ichi; Washimi, Haruichi.

1981-09-01

A theoretical model of the triggering of a solar flare by magnetosonic waves in a neutral sheet plasma is discussed. It is shown that the ponderomotive force due to the magnetosonic waves strongly excites the plasma convection flow in the magnetic neutral sheet which in turn enhances the tearing instability. The system of basic equations for the tearing mode including the time-averaged nonlinear effects due to the magnetosonic waves is derived and the boundary value problem is solved. The results show that the growth time of the instability is shortened to about 100 sec for reasonable magnetosonic wave intensity. (author)

The difference between the metal ion extracted from the R.F. ion source by applying plasma chemistry reaction and by non-plasma range chemistry reaction

International Nuclear Information System (INIS)

Bai Gui Bin

1987-01-01

The paper introduced the difference between using plasma chemistry reaction draw metal ion and non-plasma range chemistry reaction in the R.F. ion source. By using of the plasma chemistry reaction draw metal ion higher percentage than non-plasma range chemistry reaction in the R.F. ion source. The authors plasma chemistry reaction to R.F. ion source and implanter successfully. The effect is very well, it has its own characteristic

Design of a helicon plasma source for ion–ion plasma production

Energy Technology Data Exchange (ETDEWEB)

Sharma, N., E-mail: narayan.sharma@cppipr.res.in; Chakraborty, M.; Neog, N.K.; Bandyopadhyay, M.

2017-04-15

Highlights: • Development of a helicon plasma system to carry out ion–ion plasma studies in electronegative gases such as Hydrogen, Oxygen and Chlorine. • Determination of initial parameters of helicon plasma source for ion–ion plasma by using dispersion relation of bounded helicon waves. • Design and development of solenoid with magnetic field strength production capability of ∼ 600 G along the axis of the chamber. • Optimization of the chamber parameters using Helic codes and estimation of optimum attainable density. • Estimation of RF power requirements for various gases. - Abstract: A helicon plasma system is being designed and developed at CPP-IPR. The design parameters of the system are deduced from the dispersion relation of bounded helicon waves and the required magnetic fields are simulated by using Poisson Superfish code. The Helic code is used to simulate the power deposition profile for various conditions and to investigate the optimum values of chamber parameters for effective coupling of radio frequency (RF) power to plasma. The helicon source system is aimed at carrying out ion–ion plasma studies in electronegative gases such as Hydrogen, Oxygen and Chlorine. The system mainly consists of a source chamber in which helicon plasma will be produced by injecting RF power at a frequency of 13.56 MHz through a right helical antenna in presence of a DC magnetic field followed by an expansion chamber in which it is expected to produce negative ions along with the positive ions. Installation of the various parts of the system is in progress. The details of the design and development of the system is presented in this article.

Relativistic electromagnetic waves in an electron-ion plasma

Science.gov (United States)

Chian, Abraham C.-L.; Kennel, Charles F.

1987-01-01

High power laser beams can drive plasma particles to relativistic energies. An accurate description of strong waves requires the inclusion of ion dynamics in the analysis. The equations governing the propagation of relativistic electromagnetic waves in a cold electron-ion plasma can be reduced to two equations expressing conservation of energy-momentum of the system. The two conservation constants are functions of the plasma stream velocity, the wave velocity, the wave amplitude, and the electron-ion mass ratio. The dynamic parameter, expressing electron-ion momentum conversation in the laboratory frame, can be regarded as an adjustable quantity, a suitable choice of which will yield self-consistent solutions when other plasma parameters were specified. Circularly polarized electromagnetic waves and electrostatic plasma waves are used as illustrations.

Mn2C sheet as an electrode material for lithium-ion battery: A first-principles prediction

International Nuclear Information System (INIS)

Zhou, Yungang; Zu, Xiaotao

2017-01-01

Graphical abstract: Combined with strong Li bond, low Li diffusion barrier, superior electrical conductivity and high theoretical capacity, Mn 2 C Sheet is found to be a new promising electrode material for Lithium-Ion Battery. - Highlights: • Li atom bind strongly with Mn 2 C sheet with a very low adsorption energy. • Pristine Mn 2 C sheet exhibits metallic character. • Li atom can easily and freely migrate on the Mn 2 C sheet. • Lithiation to a high content is feasible. • Theoretical capacity of Mn 2 C sheet arrives at 879 mAhg −1 . - Abstract: A search for high-efficiency electrode materials is crucial for the application of Li-ion batteries (LIBs). Using density functional theory (DFT), we assess the Mn 2 C sheet, a new MXene, as a suitable electrode material. Our studies show that Li atoms can bind strongly to the Mn 2 C sheet, with low adsorption energy of −1.93 eV. A pristine Mn 2 C sheet exhibits metallic characteristic, offering an intrinsic advantage for the transportation of electrons in material. A very low energy barrier of 0.05 eV is predicted, showing that Li ion can easily and freely migrate on the Mn 2 C sheet. In addition, with the increase of Li content, adsorption energy varies minimally within a range of energy that spans only 0.27 eV, showing that lithiation to a high content is feasible. Furthermore, we found that, because of the bilayer adsorptions on both sides of the Mn 2 C sheet, the theoretical capacity of the Mn 2 C sheet is 879 mAhg −1 , which is greater than that of most two-dimentional (2D) electrode materials. All these results reveal a new promising MXene material for LIBs. We also studied the effects of oxidation and fluorination on the electrochemical properties of the Mn 2 C sheet and found that oxidation and fluorination will fade the electrochemical properties of the Mn 2 C sheet in general.

On the Acceleration and Anisotropy of Ions Within Magnetotail Dipolarizing Flux Bundles

Science.gov (United States)

Zhou, Xu-Zhi; Runov, Andrei; Angelopoulos, Vassilis; Artemyev, Anton V.; Birn, Joachim

2018-01-01

Dipolarizing flux bundles (DFBs), earthward propagating structures with enhanced northward magnetic field Bz, are usually believed to carry a distinctly different plasma population from that in the ambient magnetotail plasma sheet. The ion distribution functions within the DFB, however, have been recently found to be largely controlled by the ion adiabaticity parameter κ in the ambient plasma sheet outside the DFB. According to these observations, the ambient κ values of 2-3 usually correspond to a strong perpendicular anisotropy of suprathermal ions within the DFB, whereas for lower κ values the DFB ions become more isotropic. Here we utilize a simple, test particle model to explore the nature of the anisotropy and its dependence on the ambient κ values. We find that the anisotropy originates from successive ion reflections and reentries to the DFB, during which the ions are consecutively accelerated in the perpendicular direction by the DFB-associated electric field. This consecutive acceleration may be interrupted, however, when magnetic field lines are highly curved in the ambient plasma sheet. In this case, the ion trajectories become stochastic outside the DFB, which makes the reflected ions less likely to return to the DFB for another cycle of acceleration; as a consequence, the perpendicular ion anisotropy does not appear. Given that the DFB ions are a free energy source for instabilities when they are injected toward Earth, our simple model (that reproduces most observational features on the anisotropic DFB ion distributions) may shed new lights on the coupling process between magnetotail and inner magnetosphere.

DC plasma ion implantation in an inductively coupled RF plasma

International Nuclear Information System (INIS)

Silawatshananai, C.; Matan, N.; Pakpum, C.; Pussadee, N.; Srisantitam, P.; Davynov, S.; Vilaithong, T.

2004-01-01

Various modes of plasma ion implantation have been investigated in a small inductively coupled 13.6 MHz RF plasma source. Plasma ion implantation with HVDC(up to -10 kV bias) has been investigated in order to incorporate with the conventional implantation of diamond like carbon. In this preliminary work, nitrogen ions are implanted into the stainless steel sample with a dose of 5.5 x 10 -2 cm for a short implanting time of 7 minutes without target cooling. Surface properties such as microhardness, wear rate and the friction coefficient have been improved. X-ray and SEM analyses show distinct structural changes on the surface. A combination of sheath assisted implantation and thermal diffusion may be responsible for improvement in surface properties. (orig.)

Plasma-surface interaction in negative hydrogen ion sources

Science.gov (United States)

Wada, Motoi

2018-05-01

A negative hydrogen ion source delivers more beam current when Cs is introduced to the discharge, but a continuous operation of the source reduces the beam current until more Cs is added to the source. This behavior can be explained by adsorption and ion induced desorption of Cs atoms on the plasma grid surface of the ion source. The interaction between the ion source plasma and the plasma grid surface of a negative hydrogen ion source is discussed in correlation to the Cs consumption of the ion source. The results show that operation with deuterium instead of hydrogen should require more Cs consumption and the presence of medium mass impurities as well as ions of the source wall materials in the arc discharge enlarges the Cs removal rate during an ion source discharge.

Wave Model Development in Multi-Ion Plasmas

Directory of Open Access Journals (Sweden)

Sung-Hee Song

1999-06-01

Full Text Available Near-earth space is composed of plasmas which embed a number of plasma waves. Space plasmas consist of electrons and multi-ion that determine local wave propagation characteristics. In multi-ion plasmas, it is di cult to find out analytic solution from the dispersion relation in general. In this work, we have developed a model with an arbitrary magnetic field and density as well as multi-ion plasmas. This model allows us to investigate how plasma waves behave when they propagate along realistic magnetic field lines, which are assumed by IGRF(International Geomagnetic Reference Field. The results are found to be useful for the analysis of the in situ observational data in space. For instance, if waves are assumed to propagate into the polar region, from the equatorial region, our model quantitatively shows how polarization is altered along earth travel path.

Plasma properties of a modified beam-plasma type ion source

International Nuclear Information System (INIS)

Ishikawa, Junzo; Sano, Fumimichi; Tsuji, Hiroshi; Ektessabi, A.M.; Takagi, Toshinori

1978-01-01

The properties of the plasma produced by beam-plasma discharge were experimentally investigated. The ion source used for this work consists of three parts, that is, the ion-extracting region with an electron gun, the drift space and the collector region. Primary and secondary electron beams are injected in to the drift tube. The interaction between plasma and these electron beams causes production of high density plasma by virtue of the beam-plasma discharge. The gas inlet is located in the middle of the drift tube, so that the gas conductance is high. The energy of the primary and secondary electron beams is transferred to that microwaves through beam-plasma interaction. The microwaves heat the plasma electrons by the cyclotron resonance or other mechanism. The amount of the energetic plasma electrons is much larger than that of the beam electrons, so that neutral gas is ionized. The density of the produced plasma is 10 2 or 10 3 times as large as the plasma produced by impact ionization. With a probe located in the middle of the drift tube, the plasma density and the electron temperature can be measured, and the power and spectra of the microwaves can be detected. The microwave oscillation, the primary electron beam characteristics, and the gas pressure characteristics were studied. Larger current of the high energy primary of secondary electron beam is required for the effective discharge. The ion source has to be operated at the minimum gas pressure. The length of beam-plasma interaction and the magnetic field intensity in the drift tube are also important parameters. (Kato, T.)

Scale size and life time of energy conversion regions observed by Cluster in the plasma sheet

Directory of Open Access Journals (Sweden)

M. Hamrin

2009-11-01

Full Text Available In this article, and in a companion paper by Hamrin et al. (2009 [Occurrence and location of concentrated load and generator regions observed by Cluster in the plasma sheet], we investigate localized energy conversion regions (ECRs in Earth's plasma sheet. From more than 80 Cluster plasma sheet crossings (660 h data at the altitude of about 15–20 R_E in the summer and fall of 2001, we have identified 116 Concentrated Load Regions (CLRs and 35 Concentrated Generator Regions (CGRs. By examining variations in the power density, E·J, where E is the electric field and J is the current density obtained by Cluster, we have estimated typical values of the scale size and life time of the CLRs and the CGRs. We find that a majority of the observed ECRs are rather stationary in space, but varying in time. Assuming that the ECRs are cylindrically shaped and equal in size, we conclude that the typical scale size of the ECRs is 2 R_E≲ΔS_ECR≲5 R_E. The ECRs hence occupy a significant portion of the mid altitude plasma sheet. Moreover, the CLRs appear to be somewhat larger than the CGRs. The life time of the ECRs are of the order of 1–10 min, consistent with the large scale magnetotail MHD simulations of Birn and Hesse (2005. The life time of the CGRs is somewhat shorter than for the CLRs. On time scales of 1–10 min, we believe that ECRs rise and vanish in significant regions of the plasma sheet, possibly oscillating between load and generator character. It is probable that at least some of the observed ECRs oscillate energy back and forth in the plasma sheet instead of channeling it to the ionosphere.

Perspective on the Role of Negative Ions and Ion-Ion Plasmas in Heavy Ion Fusion Science, Magnetic Fusion Energy,and Related Fields

International Nuclear Information System (INIS)

Grisham, L.R.; Kwan, J.W.

2008-01-01

Some years ago it was suggested that halogen negative ions could offer a feasible alternative path to positive ions as a heavy ion fusion driver beam which would not suffer degradation due to electron accumulation in the accelerator and beam transport system, and which could be converted to a neutral beam by photodetachment near the chamber entrance if desired. Since then, experiments have demonstrated that negative halogen beams can be extracted and accelerated away from the gas plume near the source with a surviving current density close to what could be achieved with a positive ion of similar mass, and with comparable optical quality. In demonstrating the feasibility of halogen negative ions as heavy ion driver beams, ion - ion plasmas, an interesting and somewhat novel state of matter, were produced. These plasmas, produced near the extractor plane of the sources, appear, based upon many lines of experimental evidence, to consist of almost equal densities of positive and negative chlorine ions, with only a small component of free electrons. Serendipitously, the need to extract beams from this plasma for driver development provides a unique diagnostic tool to investigate the plasma, since each component - positive ions, negative ions, and electrons - can be extracted and measured separately. We discuss the relevance of these observations to understanding negative ion beam extraction from electronegative plasmas such as halogens, or the more familiar hydrogen of magnetic fusion ion sources. We suggest a concept which might improve negative hydrogen extraction by the addition of a halogen. The possibility and challenges of producing ion - ion plasmas with thin targets of halogens or, perhaps, salt, is briefly addressed.

Perspective on the Role of Negative Ions and Ion-Ion Plasmas in Heavy Ion Fusion Science, Magnetic Fusion Energy, and Related Fields

International Nuclear Information System (INIS)

Grisham, L.R.; Kwan, J.W.

2008-01-01

Some years ago it was suggested that halogen negative ions (1)could offer a feasible alternative path to positive ions as a heavy ion fusion driver beam which would not suffer degradation due to electron accumulation in the accelerator and beam transport system, and which could be converted to a neutral beam by photodetachment near the chamber entrance if desired. Since then, experiments have demonstrated that negative halogen beams can be extracted and accelerated away from the gas plume near the source with a surviving current density close to what could be achieved with a positive ion of similar mass, and with comparable optical quality. In demonstrating the feasibility of halogen negative ions as heavy ion driver beams, ion-ion plasmas, an interesting and somewhat novel state of matter, were produced. These plasmas, produced near the extractor plane of the sources, appear, based upon many lines of experimental evidence, to consist of almost equal densities of positive and negative chlorine ions, with only a small component of free electrons. Serendipitously, the need to extract beams from this plasma for driver development provides a unique diagnostic tool to investigate the plasma, since each component--positive ions, negative ions, and electrons--can be extracted and measured separately. We discuss the relevance of these observations to understanding negative ion beam extraction from electronegative plasmas such as halogens, or the more familiar hydrogen of magnetic fusion ion sources. We suggest a concept which might improve negative hydrogen extraction by the addition of a halogen. The possibility and challenges of producing ion-ion plasmas with thin targets of halogens or, perhaps, salt, is briefly addressed

Ion extraction from positively biased laser-ablation plasma

International Nuclear Information System (INIS)

Isono, Fumika; Nakajima, Mitsuo; Hasegawa, Jun; Horioka, Kazuhiko

2016-01-01

Ions were extracted through a grounded grid from a positively biased laser-ablation plasma and the behaviors were investigated. Since the plasma was positively biased against the grounded wall, we could extract the ions without insulated gap. We confirmed formation of a virtual anode when we increased the distance between the grid and the ion collector. Results also indicated that when the ion flux from the ablation plasma exceeded a critical value, the current was strongly suppressed to the space charge limited level due to the formation of virtual anode.

Frequency-dependent absorbance of broadband terahertz wave in dense plasma sheet

Science.gov (United States)

Peng, Yan; Qi, Binbin; Jiang, Xiankai; Zhu, Zhi; Zhao, Hongwei; Zhu, Yiming

2018-05-01

Due to the ability of accurate fingerprinting and low-ionization for different substances, terahertz (THz) technology has a lot of crucial applications in material analysis, information transfer, and safety inspection, etc. However, the spectral characteristic of atmospheric gas and ionized gas has not been widely investigated, which is important for the remote sensing application. Here, in this paper, we investigate the absorbance of broadband terahertz wave in dense plasma sheet generated by femtosecond laser pulses. It was found that as the terahertz wave transmits through the plasma sheet formed, respectively, in carbon dioxide, oxygen, argon and nitrogen, spectrum presents completely different and frequency-dependent absorbance. The reasons for these absorption peaks are related to the molecular polarity, electric charge, intermolecular and intramolecular interactions, and collisional absorption of gas molecules. These results have significant implications for the remote sensing of gas medium.

Localized fast flow disturbance observed in the plasma sheet and in the ionosphere

Directory of Open Access Journals (Sweden)

R. Nakamura

2005-02-01

Full Text Available An isolated plasma sheet flow burst took place at 22:02 UT, 1 September 2002, when the Cluster footpoint was located within the area covered by the Magnetometers-Ionospheric Radars-All-sky Cameras Large Experiment (MIRACLE. The event was associated with a clear but weak ionospheric disturbance and took place during a steady southward IMF interval, about 1h preceding a major substorm onset. Multipoint observations, both in space and from the ground, allow us to discuss the temporal and spatial scale of the disturbance both in the magnetosphere and ionosphere. Based on measurements from four Cluster spacecraft it is inferred that Cluster observed the dusk side part of a localized flow channel in the plasma sheet with a flow shear at the front, suggesting a field-aligned current out from the ionosphere. In the ionosphere the equivalent current pattern and possible field-aligned current location show a pattern similar to the auroral streamers previously obtained during an active period, except for its spatial scale and amplitude. It is inferred that the footpoint of Cluster was located in the region of an upward field-aligned current, consistent with the magnetospheric observations. The entire disturbance in the ionosphere lasted about 10min, consistent with the time scale of the current sheet disturbance in the magnetosphere. The plasma sheet bulk flow, on the other hand, had a time scale of about 2min, corresponding to the time scale of an equatorward excursion of the enhanced electrojet. These observations confirm that localized enhanced convection in the magnetosphere and associated changes in the current sheet structure produce a signature with consistent temporal and spatial scale at the conjugate ionosphere.

Observation of ion-acoustic rarefaction solitons in a multicomponent plasma with negative ions

International Nuclear Information System (INIS)

Ludwig, G.O.; Ferreira, J.L.; Nakamura, Y.

1984-01-01

The propagation of ion-acoustic solitons in a plasma with negative ions has been observed. For sufficiently large concentration of negative ions, applied rarefactive (negative) voltage pulses break up into solitons, whereas compressive pulses evolve into wave trains, with exactly the opposite behavior as that for a plasma composed only of positive ions. There is a critical value of the negative-ion concentration for which a finite-amplitude pulse propagates without steepening

Reactor aspects of counterstreaming-ion tokamak plasmas

International Nuclear Information System (INIS)

Jassby, D.L.

1975-06-01

Toroidal DT plasmas in which the D and T ions make up two distinct, quasi-thermal velocity distributions, oppositely displaced in velocity along the magnetic axis, are discussed. Such counterstreaming distributions can be set up by introducing all ions by tangential injection of neutral beams, and by removing ions from the plasma shortly after they have decelerated to an energy approximate to or less than 2T/sub e/ by Coulomb drag on the plasma electrons. A simple physical model for counterstreaming-ion operation is postulated, which allows one to deduce the ion velocity distributions and required energy and particle confinement times that are in good agreement with the results of previous Fokker-Planck calculations. The variations of fusion reactivity, power gain, and power density with injection energy and electron temperature are presented. The practical problems of implementing counter-streaming operation in a tokamak, such as charge-exchange losses, the prompt removal of cold ions, and the effect of impurities are discussed. (U.S.)

Ion accelerator based on plasma vircator

CERN Document Server

Onishchenko, I N

2001-01-01

The conception of a collective ion accelerator is proposed to be developed in the frameworks of STCU project 1569 (NSC KIPT, Ukraine) in coordination with the ISTC project 1629 (VNIEF, Russia). The main processes of acceleration are supposed to be consisted of two stages.First one is the plasma assistance virtual cathode (VC) in which plasma ions are accelerated in a potential well of VC. Along with ion acceleration the relaxation oscillations, caused by diminishing the potential well due to ion compensation, arise that provides the low-frequency (inverse ion transit time) temporal modulation of an intense relativistic electron beam (IREB) current. At the second stage temporally modulated IREB is injected into the spatially periodic magnetic field. The further ion acceleration is realized by the slow space charge wave that arises in IREB due to its simultaneous temporal and spatial modulation.

Aligned carbon nanotube-silicon sheets: a novel nano-architecture for flexible lithium ion battery electrodes.

Science.gov (United States)

Fu, Kun; Yildiz, Ozkan; Bhanushali, Hardik; Wang, Yongxin; Stano, Kelly; Xue, Leigang; Zhang, Xiangwu; Bradford, Philip D

2013-09-25

Aligned carbon nanotube sheets provide an engineered scaffold for the deposition of a silicon active material for lithium ion battery anodes. The sheets are low-density, allowing uniform deposition of silicon thin films while the alignment allows unconstrained volumetric expansion of the silicon, facilitating stable cycling performance. The flat sheet morphology is desirable for battery construction. © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Effects of Energetic Ion Outflow on Magnetospheric Dynamics

Science.gov (United States)

Kistler, L. M.; Mouikis, C.; Lund, E. J.; Menz, A.; Nowrouzi, N.

2016-12-01

There are two dominant regions of energetic ion outflow: the nightside auroral region and the dayside cusp. Processes in these regions can accelerate ions up to keV energies. Outflow from the nightside has direct access to the plasma sheet, while outflow from the cusp is convected over the polar cap and into the lobes. The cusp population can enter the plasma sheet from the lobe, with higher energy ions entering further down the tail than lower energy ions. During storm times, the O+ enhanced plasma sheet population is convected into the inner magnetosphere. The plasma that does not get trapped in the inner magnetosphere convects to the magnetopause where reconnection is taking place. An enhanced O+ population can change the plasma mass density, which may have the effect of decreasing the reconnection rate. In addition O+ has a larger gyroradius than H+ at the same velocity or energy. Because of this, there are larger regions where the O+ is demagnetized, which can lead to larger acceleration because the O+ can move farther in the direction of the electric field. In this talk we will review results from Cluster, Van Allen Probes, and MMS, on how outflow from the two locations affects magnetospheric dynamics. We will discuss whether enhanced O+ from either population has an effect on the reconnection rate in the tail or at the magnetopause. We will discuss how the two populations impact the inner magnetosphere during storm times. And finally, we will discuss whether either population plays a role in triggering substorms, particularly during sawtooth events.

Nonlinear interaction of an ion flux with plasma

International Nuclear Information System (INIS)

Ivanov, A.A.; Krasheninnikov, S.I.; Pistunovich, V.I.; Soboleva, T.K.; Yushamanov, P.N.

The present report discusses the interaction of an ion beam, formed during the charge exchange of injected neutral atoms, with a plasma. Methods of analytical study by means of quasi-linear equations as well as two-dimensional numerical modelling are used. It is shown that at a beam velocity U 0 /C/sub s/ approximately less than 1 / 2 , the relaxation process may be described by using the theory of quasi-linear relaxation of electron beams, at U 0 /C/sub s/ approximately greater than 10; one can neglect the slowing down of the ion beam and consider only the angular spread. An analytical dependence of the spread angle on time was obtained. On the basis of the ion beam relaxation theory evolved, experiments on charge exchange of plasma fluxes on a gas target are analyzed. It is shown that the anomalous scattering of the plasma flux observed in a series of experiments may be explained by the interaction of ions of the flux with ion-acoustic oscillations of the target plasma. Consideration of damping of ion-acoustic noise by the plasma electrons and ions leads to a limitation of the relaxation of the angular distribution function. The relationships obtained are in good agreement with the experimental results

Ion-acoustic Gardner solitons in a four-component nonextensive multi-ion plasma

Energy Technology Data Exchange (ETDEWEB)

Jannat, N., E-mail: nilimajannat74@gmail.com; Ferdousi, M.; Mamun, A. A. [Jahangirnagar University, Department of Physics (Bangladesh)

2016-07-15

The nonlinear propagation of ion-acoustic (IA) solitary waves (SWs) in a four-component non-extensive multi-ion plasma system containing inertial positively charged light ions, negatively charged heavy ions, as well as noninertial nonextensive electrons and positrons has been theoretically investigated. The reductive perturbation method has been employed to derive the nonlinear equations, namely, Korteweg−deVries (KdV), modified KdV (mKdV), and Gardner equations. The basic features (viz. polarity, amplitude, width, etc.) of Gardner solitons are found to exist beyond the KdV limit and these IA Gardner solitons are qualitatively different from the KdV and mKdV solitons. It is observed that the basic features of IA SWs are modified by various plasma parameters (viz. electron and positron nonextensivity, electron number density to ion number density, and electron temperature to positron temperature, etc.) of the considered plasma system. The results obtained from this theoretical investigation may be useful in understanding the basic features of IA SWs propagating in both space and laboratory plasmas.

Ion-acoustic Gardner solitons in a four-component nonextensive multi-ion plasma

International Nuclear Information System (INIS)

Jannat, N.; Ferdousi, M.; Mamun, A. A.

2016-01-01

The nonlinear propagation of ion-acoustic (IA) solitary waves (SWs) in a four-component non-extensive multi-ion plasma system containing inertial positively charged light ions, negatively charged heavy ions, as well as noninertial nonextensive electrons and positrons has been theoretically investigated. The reductive perturbation method has been employed to derive the nonlinear equations, namely, Korteweg−deVries (KdV), modified KdV (mKdV), and Gardner equations. The basic features (viz. polarity, amplitude, width, etc.) of Gardner solitons are found to exist beyond the KdV limit and these IA Gardner solitons are qualitatively different from the KdV and mKdV solitons. It is observed that the basic features of IA SWs are modified by various plasma parameters (viz. electron and positron nonextensivity, electron number density to ion number density, and electron temperature to positron temperature, etc.) of the considered plasma system. The results obtained from this theoretical investigation may be useful in understanding the basic features of IA SWs propagating in both space and laboratory plasmas.

Nonlinear electrostatic structures in homogeneous and inhomogeneous pair-ion plasmas

International Nuclear Information System (INIS)

Mahmood, S.; Ur-Rehman, H.; Shah, A.; Haque, Q.

2012-01-01

The nonlinear electrostatic structures such as solitons, shocks were studied in homogeneous, unmagnetized pair-ion plasma. The dissipation in the system was taken through kinematic viscosities of both pair-ion species. The one dimensional (Korteweg-de Vries-Burgers) KdVB equation was derived using reductive perturbation method. The analytical solution of KdVB equation was obtained using tanh method. It was found that solitons and monotonic shocks structures were formed in such type of plasmas depending on the value of dissipation in the system. Both compressive and refractive structures of solitons and monotonic shocks were obtained depending on the temperatures of negative and positive ions. The oscillatory shock structures in pair-ion plasmas were also obtained and its necessary conditions of formation were discussed. The acoustic solitons were also investigated in inhomogeneous unmagnetized pair-ion plasmas. The Korteweg-de Vries (KdV) like equation with an additional term due to density gradients was obtained by employing the reductive perturbation technique. It was found that amplitude of both compressive and refractive solitons was found to be enhanced as the density gradient parameter was increased. The Landau damping rates of electrostatic ion waves were studied for non-Maxwellian or Lorentzian pair-ion plasmas. The Val sov equation was solved analytically for weak damping effects in pair-ion plasma. It was found that Landau damping rate of ion plasma wave was increased in Lorentzian case in comparison with Maxwellian pair-ion plasmas. The numerical results were obtained by taking into account the parameters of pair-ion plasmas produced in laboratory experiments in Japan. (orig./A.B.)

Magnetized relativistic electron-ion plasma expansion

Science.gov (United States)

Benkhelifa, El-Amine; Djebli, Mourad

2016-03-01

The dynamics of relativistic laser-produced plasma expansion across a transverse magnetic field is investigated. Based on a one dimensional two-fluid model that includes pressure, enthalpy, and rest mass energy, the expansion is studied in the limit of λD (Debye length) ≤RL (Larmor radius) for magnetized electrons and ions. Numerical investigation conducted for a quasi-neutral plasma showed that the σ parameter describing the initial plasma magnetization, and the plasma β parameter, which is the ratio of kinetic to magnetic pressure are the key parameters governing the expansion dynamics. For σ ≪ 1, ion's front shows oscillations associated to the break-down of quasi-neutrality. This is due to the strong constraining effect and confinement of the magnetic field, which acts as a retarding medium slowing the plasma expansion.

Communication through a plasma sheet around a fast moving vehicle

Science.gov (United States)

Sotnikov, V. I.; Mudaliar, S.; Genoni, T.; Rose, D.; Oliver, B. V.; Mehlhorn, T. A.

2011-10-01

Investigation of the complicated problem of scattering of electromagnetic waves on turbulent pulsations induced by a sheared flow inside a plasma sheath is important for many applications including communication with hypersonic and re-entry vehicles. Theoretical and computational work aimed at improving the understanding of electromagnetic wave scattering processes in such turbulent plasmas is presented. We analyze excitation of low frequency ion-acoustic type oscillations in a compressible plasma flow with flow velocity shear and influence of such turbulent pulsations on scattering of high frequency electromagnetic waves used for communication purposes. We have appropriately included in our analysis the presence of electron and ion collisions with neutrals as well as electron - ion collisions. Results of numerical solutions for plasma density and electric field perturbations for different velocity profiles have been used in the derived expressions for scattered wave energy and scattering cross section. Work supported by the Air Force Research Laboratory and Air Force Office Of Scientific Research Sandia is a multiprogram laboratory operated by Sandia Corporation, A Lockheed Martin Company, under contract DE-AC04-94AL85000.

Impulsive ion acceleration in earth's outer magnetosphere

International Nuclear Information System (INIS)

Baker, D.N.; Belian, R.D.

1985-01-01

Considerable observational evidence is found that ions are accelerated to high energies in the outer magnetosphere during geomagnetic disturbances. The acceleration often appears to be quite impulsive causing temporally brief (10's of seconds), very intense bursts of ions in the distant plasma sheet as well as in the near-tail region. These ion bursts extend in energy from 10's of keV to over 1 MeV and are closely associated with substorm expansive phase onsets. Although the very energetic ions are not of dominant importance for magnetotail plasma dynamics, they serve as an important tracer population. Their absolute intensity and brief temporal appearance bespeaks a strong and rapid acceleration process in the near-tail, very probably involving large induced electric fields substantially greater than those associated with cross-tail potential drops. Subsequent to their impulsive acceleration, these ions are injected into the outer trapping regions forming ion ''drift echo'' events, as well as streaming tailward away from their acceleration site in the near-earth plasma sheet. Most auroral ion acceleration processes occur (or are greatly enhanced) during the time that these global magnetospheric events are occurring in the magnetotail. A qualitative model relating energetic ion populations to near-tail magnetic reconnection at substorm onset followed by global redistribution is quite successful in explaining the primary observational features. Recent measurements of the elemental composition and charge-states have proven valuable for showing the source (solar wind or ionosphere) of the original plasma population from which the ions were accelerated

Shunting arc plasma source for pure carbon ion beam

Energy Technology Data Exchange (ETDEWEB)

Koguchi, H.; Sakakita, H.; Kiyama, S.; Shimada, T.; Sato, Y.; Hirano, Y. [Energy Technology Research Institute, National Institute of Advanced Industrial Science and Technology (AIST), 1-1-1 Umezono, Tsukuba, Ibaraki 305-8568 (Japan)

2012-02-15

A plasma source is developed using a coaxial shunting arc plasma gun to extract a pure carbon ion beam. The pure carbon ion beam is a new type of deposition system for diamond and other carbon materials. Our plasma device generates pure carbon plasma from solid-state carbon material without using a hydrocarbon gas such as methane gas, and the plasma does not contain any hydrogen. The ion saturation current of the discharge measured by a double probe is about 0.2 mA/mm{sup 2} at the peak of the pulse.

Shunting arc plasma source for pure carbon ion beam.

Science.gov (United States)

Koguchi, H; Sakakita, H; Kiyama, S; Shimada, T; Sato, Y; Hirano, Y

2012-02-01

A plasma source is developed using a coaxial shunting arc plasma gun to extract a pure carbon ion beam. The pure carbon ion beam is a new type of deposition system for diamond and other carbon materials. Our plasma device generates pure carbon plasma from solid-state carbon material without using a hydrocarbon gas such as methane gas, and the plasma does not contain any hydrogen. The ion saturation current of the discharge measured by a double probe is about 0.2 mA∕mm(2) at the peak of the pulse.

Laser-plasma booster for ion post acceleration

Directory of Open Access Journals (Sweden)

Satoh D.

2013-11-01

Full Text Available A remarkable ion energy increase is demonstrated for post acceleration by a laser-plasma booster. An intense short-pulse laser generates a strong current by high-energy electrons accelerated, when this intense short-pulse laser illuminates a plasma target. The strong electric current creates a strong magnetic field along the high-energy electron current in plasma. During the increase phase in the magnetic field, a longitudinal inductive electric field is induced for the forward ion acceleration by the Faraday law. Our 2.5-dimensional particle-in-cell simulations demonstrate a remarkable increase in ion energy by several tens of MeV.

Double-layer ion acceleration triggered by ion magnetization in expanding radiofrequency plasma sources

International Nuclear Information System (INIS)

Takahashi, Kazunori; Charles, Christine; Boswell, Rod W.; Fujiwara, Tamiya

2010-01-01

Ion energy distribution functions downstream of the source exit in magnetically expanding low-pressure plasmas are experimentally investigated for four source tube diameters ranging from about 5 to 15 cm. The magnetic-field threshold corresponding to a transition from a simple expanding plasma to a double layer-containing plasma is observed to increase with a decrease in the source tube diameter. The results demonstrate that for the four geometries, the double layer and the accelerated ion beam form when the ion Larmour radius in the source becomes smaller than the source tube radius, i.e., when the ions become magnetized in the source tube.

Nonlinear waves in plasma with negative ion

International Nuclear Information System (INIS)

Saito, Maki; Watanabe, Shinsuke; Tanaca, Hiroshi.

1984-01-01

The propagation of nonlinear ion wave is investigated theoretically in a plasma with electron, positive ion and negative ion. The ion wave of long wavelength is described by a modified K-dV equation instead of a K-dV equation when the nonlinear coefficient of the K-dV equation vanishes at the critical density of negative ion. In the vicinity of the critical density, the ion wave is described by a coupled K-dV and modified K-dV equation. The transition from a compressional soliton to a rarefactive soliton and vice versa are examined by the coupled equation as a function of the negative ion density. The ion wave of short wavelength is described by a nonlinear Schroedinger equation. In the plasma with a negative ion, the nonlinear coefficient of the nonlinear Schroedinger equation changes the sign and the ion wave becomes modulationally unstable. (author)

Estimates of magnetic flux, and energy balance in the plasma sheet during substorm expansion

Science.gov (United States)

Hesse, Michael; Birn, Joachim; Pulkkinen, Tuija

1996-01-01

The energy and magnetic flux budgets of the magnetotail plasma sheet during substorm expansion are investigated. The possible mechanisms that change the energy content of the closed field line region which contains all the major dissipation mechanisms of relevance during substorms, are considered. The compression of the plasma sheet mechanism and the diffusion mechanism are considered and excluded. It is concluded that the magnetic reconnection mechanism can accomplish the required transport. Data-based empirical magnetic field models are used to investigate the magnetic flux transport required to account for the observed magnetic field dipolarizations in the inner magnetosphere. It is found that the magnetic flux permeating the current sheet is typically insufficient to supply the required magnetic flux. It is concluded that no major substorm-type magnetospheric reconfiguration is possible in the absence of magnetic reconnection.

Ion Motion in a Plasma Interacting with Strong Magnetic Fields

International Nuclear Information System (INIS)

Weingarten, A.; Grabowski, C.; Chakrabarti, N.; Maron, Y.; Fruchtmant, A.

1999-01-01

The interaction of a plasma with strong magnetic fields takes place in many laboratory experiments and astrophysical plasmas. Applying a strong magnetic field to the plasma may result in plasma displacement, magnetization, or the formation of instabilities. Important phenomena in plasma, such as the energy transport and the momentum balance, take a different form in each case. We study this interaction in a plasma that carries a short-duration (80-ns) current pulse, generating a magnetic field of up to 17 kG. The evolution of the magnetic field, plasma density, ion velocities, and electric fields are determined before and during the current pulse. The dependence of the plasma limiting current on the plasma density and composition are studied and compared to theoretical models based on the different phenomena. When the plasma collisionality is low, three typical velocities should be taken into consideration: the proton and heavier-ion Alfven velocities (v A p and v A h , respectively) and the EMHD magnetic-field penetration velocity into the plasma (v EMHD ). If both Alfven velocities are larger than v EMHD the plasma is pushed ahead of the magnetic piston and the magnetic field energy is dissipated into ion kinetic energy. If v EMHD is the largest of three velocities, the plasma become magnetized and the ions acquire a small axial momentum only. Different ion species may drift in different directions along the current lines. In this case, the magnetic field energy is probably dissipated into electron thermal energy. When vs > V EMHD > vi, as in the case of one of our experiments, ion mass separation occurs. The protons are pushed ahead of the piston while the heavier-ions become magnetized. Since the plasma electrons are unmagnetized they cannot cross the piston, and the heavy ions are probably charge-neutralized by electrons originating from the cathode that are 'born' magnetized

Collective ion acceleration by relativistic electron beams in plasmas

International Nuclear Information System (INIS)

Galvez, M.; Gisler, G.

1991-01-01

A two-dimensional fully electromagnetic particle-in-cell code is used to simulate the interaction of a relativistic electron beam injected into a finite-size background neutral plasma. The simulations show that the background electrons are pushed away from the beam path, forming a neutralizing ion channel. Soon after the beam head leaves the plasma, a virtual cathode forms which travels away with the beam. However, at later times a second, quasi-stationary, virtual cathode forms. Its position and strength depends critically on the parameters of the system which critically determines the efficiency of the ion acceleration process. The background ions trapped in the electrostatic well of the virtual cathode are accelerated and at later times, the ions as well as the virtual cathode drift away from the plasma region. The surfing of the ions in the electrostatic well produces an ion population with energies several times the initial electron beam energy. It is found that optimum ion acceleration occurs when the beam-to-plasma density ratio is near unity. When the plasma is dense, the beam is a weak perturbation and accelerates few ions, while when the plasma is tenuous, the beam is not effectively neutralized, and a virtual cathode occurs right at the injection plane. The simulations also show that, at the virtual cathode position, the electron beam is pinched producing a self-focusing phenomena

Plasma and ion beam processing at Los Alamos

International Nuclear Information System (INIS)

Rej, D.J.; Davis, H.A.; Henins, I.

1994-01-01

Efforts are underway at Los Alamos National Laboratory to utilize plasma and intense ion beam science and technology of the processing of advanced materials. A major theme involves surface modification of materials, e.g., etching, deposition, alloying, and implantation. In this paper, we concentrate on two programs, plasma source ion implantation and high-intensity pulsed ion beam deposition

Fast ions and momentum transport in JET tokamak plasmas

International Nuclear Information System (INIS)

Salmi, A.

2012-01-01

Fast ions are an inseparable part of fusion plasmas. They can be generated using electromagnetic waves or injected into plasmas as neutrals to heat the bulk plasma and to drive toroidal rotation and current. In future power plants fusion born fast ions deliver the main heating into the plasma. Understanding and controlling the fast ions is of crucial importance for the operation of a power plant. Furthermore, fast ions provide ways to probe the properties of the thermal plasma and get insight of its confinement properties. In this thesis, numerical code packages are used and developed to simulate JET experiments for a range of physics issues related to fast ions. Namely, the clamping fast ion distribution at high energies with RF heating, fast ion ripple torque generation and the toroidal momentum transport properties using NBI modulation technique are investigated. Through a comparison of numerical simulations and the JET experimental data it is shown that the finite Larmor radius effects in ion cyclotron resonance heating are important and that they can prevent fast ion tail formation beyond certain energy. The identified mechanism could be used for tailoring the fast ion distribution in future experiments. Secondly, ASCOT simulations of NBI ions in a ripple field showed that most of the reduction of the toroidal rotation that has been observed in the JET enhanced ripple experiments could be attributed to fast ion ripple torque. Finally, fast ion torque calculations together with momentum transport analysis have led to the conclusion that momentum transport in not purely diffusive but that a convective component, which increases monotonically in radius, exists in a wide range of JET plasmas. Using parameter scans, the convective transport has been shown to be insensitive to collisionality and q-profile but to increase strongly against density gradient. (orig.)

Fast ions and momentum transport in JET tokamak plasmas

Energy Technology Data Exchange (ETDEWEB)

Salmi, A.

2012-07-01

Fast ions are an inseparable part of fusion plasmas. They can be generated using electromagnetic waves or injected into plasmas as neutrals to heat the bulk plasma and to drive toroidal rotation and current. In future power plants fusion born fast ions deliver the main heating into the plasma. Understanding and controlling the fast ions is of crucial importance for the operation of a power plant. Furthermore, fast ions provide ways to probe the properties of the thermal plasma and get insight of its confinement properties. In this thesis, numerical code packages are used and developed to simulate JET experiments for a range of physics issues related to fast ions. Namely, the clamping fast ion distribution at high energies with RF heating, fast ion ripple torque generation and the toroidal momentum transport properties using NBI modulation technique are investigated. Through a comparison of numerical simulations and the JET experimental data it is shown that the finite Larmor radius effects in ion cyclotron resonance heating are important and that they can prevent fast ion tail formation beyond certain energy. The identified mechanism could be used for tailoring the fast ion distribution in future experiments. Secondly, ASCOT simulations of NBI ions in a ripple field showed that most of the reduction of the toroidal rotation that has been observed in the JET enhanced ripple experiments could be attributed to fast ion ripple torque. Finally, fast ion torque calculations together with momentum transport analysis have led to the conclusion that momentum transport in not purely diffusive but that a convective component, which increases monotonically in radius, exists in a wide range of JET plasmas. Using parameter scans, the convective transport has been shown to be insensitive to collisionality and q-profile but to increase strongly against density gradient. (orig.)

The solar wind plasma density control of night-time auroral particle precipitation

Directory of Open Access Journals (Sweden)

V. G. Vorobjev

2004-03-01

Full Text Available DMSP F6 and F7 spacecraft observations of the average electron and ion energy, and energy fluxes in different night-time precipitation regions for the whole of 1986 were used to examine the precipitation features associated with solar wind density changes. It was found that during magnetic quietness |AL|<100nT, the enhancement of average ion fluxes was observed at least two times, along with the solar wind plasma density increase from 2 to 24cm–3. More pronounced was the ion flux enhancement that occurred in the b2i–b4s and b4s–b5 regions, which are approximately corresponding to the statistical auroral oval and map to the magnetospheric plasma sheet tailward of the isotropy boundary. The average ion energy decrease of about 2–4kev was registered simultaneously with this ion flux enhancement. The results verify the occurrence of effective penetration of the solar wind plasma into the magnetospheric tail plasma sheet. Key words. Ionosphere (auroral ionosphere, particle precipitation – Magnetospheric physics (solar windmagnetosphere interaction

Ion-acoustic cnoidal wave and associated non-linear ion flux in dusty plasma

Energy Technology Data Exchange (ETDEWEB)

Jain, S. L. [Poornima Group of Institution, Sitapura, Jaipur 302022 (India); Tiwari, R. S. [Regional College for Education, Research and Technology, Jaipur 302022 (India); Mishra, M. K. [Department of Physics, University of Rajasthan, Jaipur 302004 (India)

2012-10-15

Using reductive perturbation method with appropriate boundary conditions, coupled evolution equations for first and second order potentials are derived for ion-acoustic waves in a collisionless, un-magnetized plasma consisting of hot isothermal electrons, cold ions, and massive mobile charged dust grains. The boundary conditions give rise to renormalization term, which enable us to eliminate secular contribution in higher order terms. Determining the non secular solution of these coupled equations, expressions for wave phase velocity and averaged non-linear ion flux associated with ion-acoustic cnoidal wave are obtained. Variation of the wave phase velocity and averaged non-linear ion flux as a function of modulus (k{sup 2}) dependent wave amplitude are numerically examined for different values of dust concentration, charge on dust grains, and mass ratio of dust grains with plasma ions. It is found that for a given amplitude, the presence of positively (negatively) charged dust grains in plasma decreases (increases) the wave phase velocity. This behavior is more pronounced with increase in dust concentrations or increase in charge on dust grains or decrease in mass ratio of dust grains. The averaged non-linear ion flux associated with wave is positive (negative) for negatively (positively) charged dust grains in the plasma and increases (decreases) with modulus (k{sup 2}) dependent wave amplitude. For given amplitude, it increases (decreases) as dust concentration or charge of negatively (positively) charged dust grains increases in the plasma.

Nonlinear dust-ion-acoustic waves in a multi-ion plasma with ...

Indian Academy of Sciences (India)

The basic features of such dust-ion-acoustic solitary and shock waves have been ... ion plasmas because of its vital role in understanding different types of ... cannot support the usual ion-acoustic waves, but can support the DIA waves of ...

Spectroscopic measurements of anode plasma with cryogenic pulsed ion sources

International Nuclear Information System (INIS)

Yoneda, H.; Urata, T.; Ohbayashi, K.; Kim, Y.; Horioka, K.; Kasuya, K.

1987-01-01

In ion beam diodes, electromagnetic wave is coupled to ion beam. Ion is extracted from anode plasma, which is produced early in the power pulse. However, exact mechanism of anode plasma production, expansion and ion extraction process is unknown. In particularly, anode plasma expansion is seemed to be one of the reasons of rapid impedance collapse of the diode, which is serious problem in high power experiments. Some experimental results showed that anode plasma expansion velocity was about 5 times larger than that inferred from simple thermal velocity. Several explanations for these results were proposed; for example, electron collisionarity in anode plasma, fast neutral gas particle, diamagnetism. To solve this question, it is necessary to measure the characteristic of anode plasma with space and time resolution. The authors made spectroscopic measurements to investigate variety of electron temperature, electron density, expansion velocity of anode plasma with various ion sources

Nonlinear equilibrium structure of thin currents sheets: influence of electron pressure anisotropy

Directory of Open Access Journals (Sweden)

L. M. Zelenyi

2004-01-01

Full Text Available Thin current sheets represent important and puzzling sites of magnetic energy storage and subsequent fast release. Such structures are observed in planetary magnetospheres, solar atmosphere and are expected to be widespread in nature. The thin current sheet structure resembles a collapsing MHD solution with a plane singularity. Being potential sites of effective energy accumulation, these structures have received a good deal of attention during the last decade, especially after the launch of the multiprobe CLUSTER mission which is capable of resolving their 3D features. Many theoretical models of thin current sheet dynamics, including the well-known current sheet bifurcation, have been developed recently. A self-consistent 1D analytical model of thin current sheets in which the tension of the magnetic field lines is balanced by the ion inertia rather than by the plasma pressure gradients was developed earlier. The influence of the anisotropic electron population and of the corresponding electrostatic field that acts to restore quasi-neutrality of the plasma is taken into account. It is assumed that the electron motion is fluid-like in the direction perpendicular to the magnetic field and fast enough to support quasi-equilibrium Boltzmann distribution along the field lines. Electrostatic effects lead to an interesting feature of the current density profile inside the current sheet, i.e. a narrow sharp peak of electron current in the very center of the sheet due to fast curvature drift of the particles in this region. The corresponding magnetic field profile becomes much steeper near the neutral plane although the total cross-tail current is in all cases dominated by the ion contribution. The dependence of electrostatic effects on the ion to electron temperature ratio, the curvature of the magnetic field lines, and the average electron magnetic moment is also analyzed. The implications of these effects on the fine structure of thin current sheets

Radiative Recombination and Photoionization Data for Tungsten Ions. Electron Structure of Ions in Plasmas

Directory of Open Access Journals (Sweden)

Malvina B. Trzhaskovskaya

2015-05-01

Full Text Available Theoretical studies of tungsten ions in plasmas are presented. New calculations of the radiative recombination and photoionization cross-sections, as well as radiative recombination and radiated power loss rate coefficients have been performed for 54 tungsten ions for the range W6+–W71+. The data are of importance for fusion investigations at the reactor ITER, as well as devices ASDEX Upgrade and EBIT. Calculations are fully relativistic. Electron wave functions are found by the Dirac–Fock method with proper consideration of the electron exchange. All significant multipoles of the radiative field are taken into account. The radiative recombination rates and the radiated power loss rates are determined provided the continuum electron velocity is described by the relativistic Maxwell–Jüttner distribution. The impact of the core electron polarization on the radiative recombination cross-section is estimated for the Ne-like iron ion and for highly-charged tungsten ions within an analytical approximation using the Dirac–Fock electron wave functions. The effect is shown to enhance the radiative recombination cross-sections by ≲20%. The enhancement depends on the photon energy, the principal quantum number of polarized shells and the ion charge. The influence of plasma temperature and density on the electron structure of ions in local thermodynamic equilibrium plasmas is investigated. Results for the iron and uranium ions in dense plasmas are in good agreement with previous calculations. New calculations were performed for the tungsten ion in dense plasmas on the basis of the average-atom model, as well as for the impurity tungsten ion in fusion plasmas using the non-linear self-consistent field screening model. The temperature and density dependence of the ion charge, level energies and populations are considered.

Investigations of electrostatic ion waves in a collisionless plasma

International Nuclear Information System (INIS)

Michelsen, P.

1980-06-01

The author reviews a series of publications concerning theoretical and experimental investigations of electrostatic ion waves in a collisionless plasma. The experimental work was performed in the Risoe Q-machine under various operational conditions. Besides a description of this machine and the diagnostic techniques used for the measurements, two kinds of electrostatic waves are treated, namely, ion-acoustic waves and ion-cyclotron waves. Due to the relative simplicity of the ion-acoustic waves, these were treated in detail in order to get a more general understanding of the behaviour of the propagation properties of electrostatic waves. The problem concerning the difficulties in describing waves excited at a certain position and propagating in space by a proper mathematical model was especially considered in depth. Furthermore, ion-acoustic waves were investigated which propagated in a plasma with a density gradient, and afterwards in a plasma with an ion beam. Finally, a study of the electrostatic ion-cyclotron waves was undertaken, and it was shown that these waves were unstable in a plasma traversed by an ion beam. (Auth.)

New developments in metal ion implantation by vacuum arc ion sources and metal plasma immersion

International Nuclear Information System (INIS)

Brown, I.G.; Anders, A.; Anders, S.

1996-01-01

Ion implantation by intense beams of metal ions can be accomplished using the dense metal plasma formed in a vacuum arc discharge embodied either in a vacuum arc ion source or in a metal plasma immersion configuration. In the former case high energy metal ion beams are formed and implantation is done in a more-or-less conventional way, and in the latter case the substrate is immersed in the plasma and repetitively pulse-biased so as to accelerate the ions at the high voltage plasma sheath formed at the substrate. A number of advances have been made in the last few years, both in plasma technology and in the surface modification procedures, that enhance the effectiveness and versatility of the methods, including for example: controlled increase of the in charge states produced; operation in a dual metal-gaseous ion species mode; very large area beam formation; macroparticle filtering; and the development of processing regimes for optimizing adhesion, morphology and structure. These complementary ion processing techniques provide the plasma tools for doing ion surface modification over a very wide parameter regime, from pure ion implantation at energies approaching the MeV level, through ion mixing at energies in the ∼1 to ∼100 keV range, to IBAD-like processing at energies from a few tens of eV to a few keV. Here the authors review the methods, describe a number of recent developments, and outline some of the surface modification applications to which the methods have been put. 54 refs., 9 figs

Ion acoustic solitons/double layers in two-ion plasma revisited

International Nuclear Information System (INIS)

Lakhina, G. S.; Singh, S. V.; Kakad, A. P.

2014-01-01

Ion acoustic solitons and double layers are studied in a collisionless plasma consisting of cold heavier ion species, a warm lighter ion species, and hot electrons having Boltzmann distributions by Sagdeev pseudo-potential technique. In contrast to the previous results, no double layers and super-solitons are found when both the heavy and lighter ion species are treated as cold. Only the positive potential solitons are found in this case. When the thermal effects of the lighter ion species are included, in addition to the usual ion-acoustic solitons occurring at M > 1 (where the Mach number, M, is defined as the ratio of the speed of the solitary wave and the ion-acoustic speed considering temperature of hot electrons and mass of the heavier ion species), slow ion-acoustic solitons/double layers are found to occur at low Mach number (M < 1). The slow ion-acoustic mode is actually a new ion-ion hybrid acoustic mode which disappears when the normalized number density of lighter ion species tends to 1 (i.e., no heavier species). An interesting property of the new slow ion-acoustic mode is that at low number density of the lighter ion species, only negative potential solitons/double layers are found whereas for increasing densities there is a transition first to positive solitons/double layers, and then only positive solitons. The model can be easily applicable to the dusty plasmas having positively charged dust grains by replacing the heavier ion species by the dust mass and doing a simple normalization to take account of the dust charge

Ion beam extraction from a matrix ECR plasma source by discrete ion-focusing effect

DEFF Research Database (Denmark)

Stamate, Eugen; Draghici, Mihai

2010-01-01

-ECR plasma source [3] with transversal magnetic filter for electron temperature control. 12 ECR plasma cells are placed 7.5 cm apart on the top of a cubic chamber 40x40x40 cm3. Each cell can be controlled independently by tuning the injected microwave power. The discharge is operated at pressures below 1 m......Positive or negative ion beams extracted from plasma are used in a large variety of surface functionalization techniques such as implantation, etching, surface activation, passivation or oxidation. Of particular importance is the surface treatment of materials sensitive to direct plasma exposure...... due to high heath fluxes, the controllability of the ion incidence angle, and charge accumulation when treating insulating materials. Despite of a large variety of plasma sources available for ion beam extraction, there is a clear need for new extraction mechanisms that can make available ion beams...

Dense sheet Z-pinches

International Nuclear Information System (INIS)

Tetsu, Miyamoto

1999-01-01

The steady state and quasi-steady processes of infinite- and finite-width sheet z-pinches are studied. The relations corresponding to the Bennett relation and Pease-Braginskii current of cylindrical fiber z-pinches depend on a geometrical factor in the sheet z-pinches. The finite-width sheet z-pinch is approximated by a segment of infinite-width sheet z-pinch, if it is wide enough, and corresponds to a number of (width/thickness) times fiber z-pinch plasmas of the diameter that equals the sheet thickness. If the sheet current equals this number times the fiber current, the plasma created in the sheet z-pinches is as dense as in the fiber z-pinches. The total energy of plasma and magnetic field per unit mass is approximately equal in both pinches. Quasi-static transient processes are different in several aspects from the fiber z-pinch. No radiation collapse occurs in the sheet z-pinch. The stability is improved in the sheet z-pinches. The fusion criterions and the experimental arrangements to produce the sheet z-pinches are also discussed. (author)

Current disruptions in the near-earth neutral sheet region

International Nuclear Information System (INIS)

Liu, A.T.Y.; Anderson, B.J.; Takahashi, K.; Zanetti, L.J.; McEntire, R.W.; Potemra, T.A.; Lopez, R.E.; Klumpar, D.M.; Greene, E.M.; Strangeway, R.

1992-01-01

Observations from the Charge Composition Explorer in 1985 and 1986 revealed fifteen current disruption events in which the magnetic field fluctuations were large and their onsets coincided well with ground onsets of substorm expansion or intensification. Over the disruption interval, the local magnetic field can change by as much as a factor of ∼7. In general, the stronger the current buildup and the closer the neutral sheet, the larger the resultant field change. There is also a tendency for a larger subsequent enhancement in the AE index with a stronger current buildup prior to current disruption. For events with good pitch angle coverage and extended observation in the neutral sheet region the authors find that the particle pressure increases toward the disruption onset and decreases afterward. Just prior to disruption, either the total particle pressure is isotropic, or the perpendicular component (P perpendicular ) dominates the parallel component (P parallel ), the plasma beta is seen to be as high as ∼70, and the observed plasma pressure gradient at the neutral sheet is large along the tail axis. The deduced local current density associated with pressure gradient is ∼27-80 n/Am 2 and is ∼85-105 mA/m when integrated over the sheet thickness. They infer from these results that just prior to the onset of current disruption, (1) an extremely thin current sheet requiring P parallel > P perpendicular for stress balance does not develop at these distances, (2) the thermal ion orbits are in the chaotic or Speiser regime while the thermal electrons are in the adiabatic regime and, in one case, exhibit peaked fluxes perpendicular to the magnetic field, thus implying no electron orbit chaotization to possibly initiate ion tearing instability, and (3) the neutral sheet is in the unstable regime specified by the cross-field current instability

Confinement of laser plasma by solenoidal field for laser ion source

International Nuclear Information System (INIS)

Okamura, M.; Kanesue, T.; Kondo, K.; Dabrowski, R.

2010-01-01

A laser ion source can provide high current, highly charged ions with a simple structure. However, it was not easy to control the ion pulse width. To provide a longer ion beam pulse, the plasma drift length, which is the distance between laser target and extraction point, has to be extended and as a result the plasma is diluted severely. Previously, we applied a solenoid field to prevent reduction of ion density at the extraction point. Although a current enhancement by a solenoid field was observed, plasma behavior after a solenoid magnet was unclear because plasma behavior can be different from usual ion beam dynamics. We measured a transverse ion distribution along the beam axis to understand plasma motion in the presence of a solenoid field.

A one-dimensional collisional model for plasma-immersion ion implantation

International Nuclear Information System (INIS)

Vahedi, V.; Lieberman, M.A.; Alves, M.V.; Verboncoeur, J.P.; Birdsall, C.K.

1991-01-01

Plasma-immersion ion implantation (also known as plasma-source ion implantation) is a process in which a target is immersed in a plasma and a series of large negative-voltage pulses are applied to it to extract ions from the plasma and implant them into the target. A general one-dimensional model is developed to study this process in different coordinate systems for the case in which the pressure of the neutral gas is large enough that the ion motion in the sheath can be assumed to be highly collisional

Ion acoustic waves and double-layers in electronegative expanding plasmas

International Nuclear Information System (INIS)

Plihon, Nicolas; Chabert, Pascal

2011-01-01

Ion acoustic waves and double-layers are observed in expanding plasmas in electronegative gases, i.e., plasmas containing an appreciable fraction of negative ions. The reported experiments are performed in argon gas with a variable amount of SF 6 . When varying the amount of SF 6 , the negative ion fraction increases and three main regimes were identified previously: (i) the plasma smoothly expands at low negative ion fraction, (ii) a static double-layer (associated with an abrupt potential drop and ion acceleration) forms at intermediate negative ion fraction, (iii) double-layers periodically form and propagate (in the plasma expansion direction) at high negative ion fraction. In this paper, we show that transition phases exist in between these regimes, where fluctuations are observed. These fluctuations are unstable slow ion acoustic waves, propagating in the direction opposite to the plasma expansion. These fluctuations are excited by the most unstable eigenmodes and display turbulent features. It is suggested that the static double layer forms when the ion acoustic fluctuations become non-linearly unstable: the double layer regime being a bifurcated state of the smoothly expanding regime. For the highest negative ion fraction, a coexistence of (upstream propagating) slow ion acoustic fluctuations and (downstream) propagating double layers was observed.

Highly Supersonic Ion Pulses in a Collisionless Magnetized Plasma

DEFF Research Database (Denmark)

Juul Rasmussen, Jens; Schrittwieser, R.

1982-01-01

The initial transient response of a collisionless plasma to a high positive voltage step is investigated. Four different pulses are observed. An electron plasma wave pulse is followed by an ion burst. The latter is overtaken and absorbed by a highly supersonic ion pulse. Thereafter, an ion...

Electrostatic shock structures in dissipative multi-ion dusty plasmas

Science.gov (United States)

Elkamash, I. S.; Kourakis, I.

2018-06-01

A comprehensive analytical model is introduced for shock excitations in dusty bi-ion plasma mixtures, taking into account collisionality and kinematic (fluid) viscosity. A multicomponent plasma configuration is considered, consisting of positive ions, negative ions, electrons, and a massive charged component in the background (dust). The ionic dynamical scale is focused upon; thus, electrons are assumed to be thermalized, while the dust is stationary. A dissipative hybrid Korteweg-de Vries/Burgers equation is derived. An analytical solution is obtained, in the form of a shock structure (a step-shaped function for the electrostatic potential, or an electric field pulse) whose maximum amplitude in the far downstream region decays in time. The effect of relevant plasma configuration parameters, in addition to dissipation, is investigated. Our work extends earlier studies of ion-acoustic type shock waves in pure (two-component) bi-ion plasma mixtures.

Confinement of multiply charged ions in an ECRH mirror plasma

International Nuclear Information System (INIS)

Petty, C.C.

1989-06-01

This thesis is an experimental study of multiply charged ions in the Constance B mirror experiment. By measuring the ion densities, end loss fluxes and ion temperatures, the parallel confinement times for the first five charge states of oxygen and neon plasmas are determined. The parallel ion confinement times increase with charge state and peak on axis, both indications of an ion-confining potential dip created by the hot electrons. The radial profile of ion end loss is usually hollow due to large ion radial transport (τ paralleli ∼ τ perpendiculari ), with the peak fluxes occurring at the edge of the electron cyclotron resonance zone. Several attempts are made to increase the end loss of selected ion species. Using minority ICRH, the end loss flux of resonant ions increases by 20% in cases when radial transport induced by ICRH is not too severe. A large antenna voltage can also extinguish the plasma. By adding helium to an oxygen plasma, the end loss of O 6+ increases by 80% due to decreased ion radial transport. An ion model is developed to predict the ion densities, end loss fluxes and confinement times in the plasma center using the ion particle balance equations, the quasineutrality condition and theoretical confinement time formulas. The model generally agrees with the experimental data for oxygen and neon plasmas to within experimental error. Under certain conditions spatial diffusion appears to determine the parallel ion confinement time of the highest charge states. For oxygen plasmas during ICRH, the measured parallel confinement time of the resonant ions is much shorter than their theoretical value, probably due to rf diffusion of the ions into the loss cone. 58 refs., 101 figs., 16 tabs

Improved planar radio frequency inductively coupled plasma configuration in plasma immersion ion implantation

International Nuclear Information System (INIS)

Tang, D.L.; Fu, R.K.Y.; Tian, X.B.; Chu, P.K.

2003-01-01

Plasmas with higher density and better uniformity are produced using an improved planar radio frequency (rf) inductively coupled plasma configuration in plasma immersion ion implantation (PIII). An axial magnetic field is produced by external electromagnetic coils outside the discharge chamber. The rf power can be effectively absorbed by the plasma in the vicinity of the electron gyrofrequency due to the enhanced resonant absorption of electromagnetic waves in the whistler wave range, which can propagate nearly along the magnetic field lines thus greatly increases the plasma density. The plasma is confined by a longitudinal multipolar cusp magnetic field made of permanent magnets outside the process chamber. It can improve the plasma uniformity without significantly affecting the ion density. The plasma density can be increased from 3x10 9 to 1x10 10 cm -3 employing an axial magnetic field of several Gauss at 1000 W rf power and 5x10 -4 Torr gas pressure. The nonuniformity of the plasma density is less than 10% and can be achieved in a process chamber with a diameter of 600 mm. Since the plasma generation and process chambers are separate, plasma extinction due to the plasma sheath touching the chamber wall in high-energy PIII can be avoided. Hence, low-pressure, high-energy, and high-uniformity ion implantation can be accomplished using this setup

Ion trapping within the dust grain plasma sheath

International Nuclear Information System (INIS)

Jovanovic, D.; Shukla, P.K.

2002-01-01

One of the most important and still unresolved problems in the physics of dusty plasmas is the determination of the dust charge. The grains are not directly accessible to measurements and it is necessary to have a reliable theoretical model of the electron and ion dynamics inside the Debye sphere for the interpretation of the relevant experimental data, which include also the effects of the surrounding electron and ion clouds. Recent computer simulations [6] and laboratory experiments [9] indicate that the plasma sheath is dominated by trapped ions, orbiting the grain on closed trajectories at distances smaller than the Debye radius, that cannot be accounted for by the classical theories. We present the first analytical, fully self-consistent, calculations of the electrostatic shielding of a charged dust grain in a collisional plasma. In the regime when the mean free path for the ion-dust collisions is larger than that for the ion-neutral collisions, we solve the kinetic equation for the ions, coupled with Boltzmann distributed electrons and Poisson's equation. The ion velocity distribution function, in the form of a spherically symmetric ion hole, is found to be anisotropic in the presence of charge-exchange collisions. The number of trapped ions and their spatial distribution are determined from the interplay between the collective plasma interaction and the collisional trapping/de-trapping. The stationary state results from the self-tuning of the trapped ion density by the feedback based on the nonlocality of the collisional integral, and on the ion mixing in the radial direction along elongated orbits. Our results confirm the existence of a strong Debye shielding of the dust charge, allowing also the over-population of the trapped ion distribution (ion hump)

Solitons in a relativistic plasma with negative ions--

International Nuclear Information System (INIS)

Das, G.C.; Karmakar, B.; Ibohanbi Singh, KH.

1990-01-01

The interaction of the nonlinearity and the dispersiveness causing the solitary waves are studied in a relativistic plasma with negative ions through the derivation of a nonlinear partial differential equation known as the Korteweg-Devries (K-DV) equation. The negative ions play a salient feature on the existence and behavior of the solitons and could be of interest in laboratory plasmas. First, the observations are made in a nonisothermal plasma, and later the reduction to the nonisothermality of the plasma shows entirely different characteristics as compared to the solitons in the isothermal plasmas. A comparison with the various solutions has been emphasized

Dispersion surfaces and ion wave instabilities in space plasmas

International Nuclear Information System (INIS)

Andre, M

1985-08-01

In this thesis, the dispersion relation of linear waves in a non-relativistic, collisionless and homogeneous plasma in a uniform magnetic field, is solved numerically. Both electrostatic and elecromagnetic waves with frequencies from below the ion gyrofrequency to above the electron gyrofrequency are studied for all angles of propagation. Modes occurring in a cold plasma as well as waves dependent on thermal effects are included. Dispersion surfaces, that is plots of frequency versus wavevector components, are presented for some models of space plasmas. Waves with frequencies of the order of the ion gyrofrequency (ion waves), are well known to exist in space plasmas. In this thesis, the generation of ion waves by ion distributions with loss-cones or temperature anisotropies, or by beams of charged particles, is investigated by numerical methods. Effects of heavy ions are considered. Dispersion surfaces and analytical arguments are used to clarify the results. It is shown that particle beams and ion loss-cone distributions can generate electrostatic ion waves, even when a significant amount of the electrons are cool. These calculations are in agreement with simultaneous observatons of waves and particles obtained by a satellite on auroral field lines. (author)

Charging of dust grains in a plasma with negative ions

International Nuclear Information System (INIS)

Kim, Su-Hyun; Merlino, Robert L.

2006-01-01

The effect of negative ions on the charging of dust particles in a plasma is investigated experimentally. A plasma containing a very low percentage of electrons is formed in a single-ended Q machine when SF 6 is admitted into the vacuum system. The relatively cold Q machine electrons (T e ≅0.2 eV) readily attach to SF 6 molecules to form SF 6 - negative ions. Calculations of the dust charge indicate that for electrons, negative ions, and positive ions of comparable temperatures, the charge (or surface potential) of the dust can be positive if the positive ion mass is smaller than the negative ion mass and if ε, the ratio of the electron to positive ion density, is sufficiently small. The Q machine plasma is operated with K + positive ions (mass 39 amu) and SF 6 - negative ions (mass 146 amu), and also utilizes a rotating cylinder to dispense dust into the plasma column. Analysis of the current-voltage characteristics of a Langmuir probe in the dusty plasma shows evidence for the reduction in the (magnitude) of the negative dust charge and the transition to positively charged dust as the relative concentration of the residual electrons is reduced. Some remarks are offered concerning experiments that could become possible in a dusty plasma with positive grains

Slowing-down of non-relativistic ions in a hot dense plasma

International Nuclear Information System (INIS)

Maynard, G.

1982-01-01

The parameter γ (action of the free-electrons of the plasma) was investigated: calculation of the mean value of γ for a great number of monokinetic incident ions and of the dispersion about this mean value, using the random phase approximation; and calculation of the dielectric function. The contribution of the plasma ions to the stopping power was studied and the description of the ion-plasma interaction improved. The slowing-down of an ion at large distance by the bound electrons of an atom was calculated. This study is applied to the ion-plasma interaction in the ion-beam inertial confinement [fr

Intense ion beam neutralization using underdense background plasma

Energy Technology Data Exchange (ETDEWEB)

Berdanier, William [Department of Physics, The University of Texas at Austin, Austin, Texas 78712 (United States); Princeton Plasma Physics Laboratory, Princeton University, Princeton, New Jersey 08543 (United States); Roy, Prabir K. [Lawrence Berkeley National Laboratory, Berkeley, California 94720 (United States); Kaganovich, Igor [Princeton Plasma Physics Laboratory, Princeton University, Princeton, New Jersey 08543 (United States)

2015-01-15

Producing an overdense background plasma for neutralization purposes with a density that is high compared to the beam density is not always experimentally possible. We show that even an underdense background plasma with a small relative density can achieve high neutralization of intense ion beam pulses. Using particle-in-cell simulations, we show that if the total plasma electron charge is not sufficient to neutralize the beam charge, electron emitters are necessary for effective neutralization but are not needed if the plasma volume is so large that the total available charge in the electrons exceeds that of the ion beam. Several regimes of possible underdense/tenuous neutralization plasma densities are investigated with and without electron emitters or dense plasma at periphery regions, including the case of electron emitters without plasma, which does not effectively neutralize the beam. Over 95% neutralization is achieved for even very underdense background plasma with plasma density 1/15th the beam density. We compare results of particle-in-cell simulations with an analytic model of neutralization and find close agreement with the particle-in-cell simulations. Further, we show experimental data from the National Drift Compression experiment-II group that verifies the result that underdense plasma can neutralize intense heavy ion beams effectively.

Development of intense pulsed heavy ion beam diode using gas puff plasma gun as ion source

International Nuclear Information System (INIS)

Ito, H.; Higashiyama, M.; Takata, S.; Kitamura, I.; Masugata, K.

2006-01-01

A magnetically insulated ion diode with an active ion source of a gas puff plasma gun has been developed in order to generate a high-intensity pulsed heavy ion beam for the implantation process of semiconductors and the surface modification of materials. The nitrogen plasma produced by the plasma gun is injected into the acceleration gap of the diode with the external magnetic field system. The ion diode is operated at diode voltage approx. =200 kV, diode current approx. =2 kA and pulse duration approx. =150 ns. A new acceleration gap configuration for focusing ion beam has been designed in order to enhance the ion current density. The experimental results show that the ion current density is enhanced by a factor of 2 and the ion beam has the ion current density of 27 A/cm 2 . In addition, the coaxial type Marx generator with voltage 200 kV and current 15 kA has been developed and installed in the focus type ion diode. The ion beam of ion current density approx. =54 A/cm 2 is obtained. To produce metallic ion beams, an ion source by aluminum wire discharge has been developed and the aluminum plasma of ion current density ∼70 A/cm 2 is measured. (author)

Light-induced ion-acoustic instability of rarefied plasma

International Nuclear Information System (INIS)

Krasnov, I.V.; Sizykh, D.V.

1987-01-01

A new method of ion-acoustic instability excitation under the effect of coherent light, resonance to ion quantum transitions on collisionless plasma, is suggested. The light-induced ion-acoustic instability (LIIAI) considered is based on the induced progressive nonequilibrium resonance particles in the field of travelling electromagnetic wave. Principal possibility to use LIIAI in high-resolution spectroscopy and in applied problems of plasma physics, related to its instability, is pointed out

Faraday cup for analyzing multi-ion plasma

International Nuclear Information System (INIS)

Fujita, Takao

1987-01-01

A compact and convenient ion analyzer (a kind of a Faraday cup) is developed in order to analyze weakly ionized multi-ion plasmas. This Faraday cup consists of three mesh electrodes and a movable ion collector. With a negative gate pulse superimposed on the ion retarding bias, ions are analyzed by means of time-of-flight. The identification of ion species and measurements of ion density and ion temperature are studied. (author)

Modulation instability of ion thermal waves in a pair-ion plasma containing charged dust impurities

International Nuclear Information System (INIS)

Sabry, R.

2008-01-01

Modulation instability of ion thermal waves (ITWs) is investigated in a plasma composed of positive and negative ions as well as a fraction of stationary charged (positive or negative) dust impurities. For this purpose, a linear dispersion relation and a nonlinear Schroedinger equation are derived. The latter admits localized envelope solitary wave solutions of bright (pulses) and dark (holes, voids) type. The envelope soliton depends on the intrinsic plasma parameters. It is found that modulation instability of ITWs is significantly affected by the presence of positively/negatively charged dust grains. The findings of this investigation should be useful in understanding the stable electrostatic wave packet acceleration mechanisms in pair-ion plasma, and also enhances our knowledge on the occurrence of instability associated to the existence of charged dust impurities in pair-ion plasmas. Our results should be of relevance for laboratory plasmas.

Influence of plasma density and plasma sheath dynamics on the ion implantation by plasma immersion technique

OpenAIRE

Ensinger, Wolfgang

1996-01-01

Influence of plasma density and plasma sheath dynamics on the ion implantation by plasma immersion technique / B. Rauschenbach ... - In: Nuclear instruments and methods in physics research. B. 113. 1996. S. 266-269

Absorption of calcium ions on oxidized graphene sheets and study its dynamic behavior by kinetic and isothermal models

Directory of Open Access Journals (Sweden)

Mahmoud Fathy

2016-07-01

Full Text Available Abstract Sorption of calcium ion from the hard underground water using novel oxidized graphene (GO sheets was studied in this paper. Physicochemical properties and microstructure of graphene sheets were investigated using Raman spectrometer, thermogravimetry analyzer, transmission electron microscope, scanning electron microscope. The kinetics adsorption of calcium on graphene oxide sheets was examined using Lagergren first and second orders. The results show that the Lagergren second-order was the best-fit model that suggests the conception process of calcium ion adsorption on the Go sheets. For isothermal studies, the Langmuir and Freundlich isotherm models were used at temperatures ranging between 283 and 313 K. Thermodynamic parameters resolved at 283, 298 and 313 K indicating that the GO adsorption was exothermic spontaneous process. Finally, the graphene sheets show high partiality toward calcium particles and it will be useful in softening and treatment of hard water.

Effect of multi-ions on electromagnetic ion-cyclotron waves with a hot plasma around the polar cusp

International Nuclear Information System (INIS)

Patel, Soniya; Varma, P; Tiwari, M S

2011-01-01

Electromagnetic ion cyclotron (EMIC) instabilities with an isotropic ion beam and general loss-cone distribution of hot core plasmas are discussed. The growth rate of the wave, perpendicular heating of ions, parallel resonant energy and marginal instability of the EMIC waves in homogeneous plasmas are obtained using the dispersion relation for hot plasmas consisting of H + , He + ,O + ions and electrons. The wave is assumed to propagate parallel to the static magnetic field. The whole plasma is considered to consist of resonant and non-resonant particles permeated by the isotropic ion beam. It is assumed that the resonant particles and the ion beam participate in energy exchange with the wave, whereas the non-resonant particles support the oscillatory motion of the wave. We determined the variation in energies and growth rate in hot plasmas by the energy conservation method with a general loss-cone distribution function. We also discuss the effect of positive and negative ion beam velocity on the growth rate of the wave. The thermal anisotropy of the ions of the core plasma acts as a source of free energy for EMIC waves and enhances the growth rate. Heating of ions perpendicular to the magnetic field is discussed along with EMIC wave emission in the polar cusp region.

High-frequency heating of plasma with two ion species

International Nuclear Information System (INIS)

Klima, R.; Longinov, A.V.; Stepanov, K.N.

1975-01-01

The authors consider the penetration of electromagnetic waves with a frequency of the order of the ion cyclotron frequencies and with a fixed longitudinal wave number ksub(long), so that Nsub(long)=ksub(long)c/ω>>1 deep into an inhomogeneous plasma with two ion species. The propagation of two kinds of waves (fast and slow) with widely differing polarization and transverse refraction index is possible. For both types of waves there is an evanescence region at the plasma periphery. The evanescence region is narrow for slow waves and they easily penetrate the plasma. In a dense plasma they become electrostatic and can reach the ion-ion hybrid resonance region. However, the damping of these waves due to Cherenkov interaction with electrons in a high-temperature plasma is strong and therefore they are not suitable for heating plasma of large dimensions, as they are absorbed at the plasma periphery. The fast waves have a wider evanescence region and can be excited effectively only if N 2 is not too high. These waves can be completely absorbed in the plasma (due to Cherenkov interaction with electrons) if xi approximately (v 2 sub(Ti)/v 2 sub(A))Zsub(e)(ωsub(pi)a/c)exp(-Zsub(e) 2 ) > 1, where a is the plasma radius and Zsub(e) = ω/(√2 ksub(long)vsub(Te)). Fast waves can also reach the region where they are transformed into slow waves. In this region their damping increases considerably. It is shown that the transformation region in an inhomogeneous plasma with two ion species in a non-uniform magnetic field may be at the centre of the plasma. Fast waves can be used effectively for heating plasma of large dimensions. (author)

Charging of dust grains in a plasma with negative ions

Science.gov (United States)

Kim, Su-Hyun; Merlino, Robert L.

2006-05-01

The effect of negative ions on the charging of dust particles in a plasma is investigated experimentally. A plasma containing a very low percentage of electrons is formed in a single-ended SF6 is admitted into the vacuum system. The relatively cold (Te≈0.2eV ) readily attach to SF6 molecules to form SF6- negative ions. Calculations of the dust charge indicate that for electrons, negative ions, and positive ions of comparable temperatures, the charge (or surface potential) of the dust can be positive if the positive ion mass is smaller than the negative ion mass and if ɛ, the ratio of the electron to positive ion density, is sufficiently small. The K+ positive ions (mass 39amu) and SF6- negative ions (mass 146amu), and also utilizes a rotating cylinder to dispense dust into the plasma column. Analysis of the current-voltage characteristics of a Langmuir probe in the dusty plasma shows evidence for the reduction in the (magnitude) of the negative dust charge and the transition to positively charged dust as the relative concentration of the residual electrons is reduced. Some remarks are offered concerning experiments that could become possible in a dusty plasma with positive grains.

Ion irradiated graphite exposed to fusion-relevant deuterium plasma

International Nuclear Information System (INIS)

Deslandes, Alec; Guenette, Mathew C.; Corr, Cormac S.; Karatchevtseva, Inna; Thomsen, Lars; Ionescu, Mihail; Lumpkin, Gregory R.; Riley, Daniel P.

2014-01-01

Graphite samples were irradiated with 5 MeV carbon ions to simulate the damage caused by collision cascades from neutron irradiation in a fusion environment. The ion irradiated graphite samples were then exposed to a deuterium plasma in the linear plasma device, MAGPIE, for a total ion fluence of ∼1 × 10 24 ions m −2 . Raman and near edge X-ray absorption fine structure (NEXAFS) spectroscopy were used to characterize modifications to the graphitic structure. Ion irradiation was observed to decrease the graphitic content and induce disorder in the graphite. Subsequent plasma exposure decreased the graphitic content further. Structural and surface chemistry changes were observed to be greatest for the sample irradiated with the greatest fluence of MeV ions. D retention was measured using elastic recoil detection analysis and showed that ion irradiation increased the amount of retained deuterium in graphite by a factor of four

The ionization length in plasmas with finite temperature ion sources

Science.gov (United States)

Jelić, N.; Kos, L.; Tskhakaya, D. D.; Duhovnik, J.

2009-12-01

The ionization length is an important quantity which up to now has been precisely determined only in plasmas which assume that the ions are born at rest, i.e., in discharges known as "cold ion-source" plasmas. Presented here are the results of our calculations of the ionization lengths in plasmas with an arbitrary ion source temperature. Harrison and Thompson (H&T) [Proc. Phys. Soc. 74, 145 (1959)] found the values of this quantity for the cases of several ion strength potential profiles in the well-known Tonks-Langmuir [Phys. Rev. 34, 876 (1929)] discharge, which is characterized by "cold" ion temperature. This scenario is also known as the "singular" ion-source discharge. The H&T analytic result covers cases of ion sources proportional to exp(βΦ) with Φ the normalized plasma potential and β =0,1,2 values, which correspond to particular physical scenarios. Many years following H&T's work, Bissell and Johnson (B&J) [Phys. Fluids 30, 779 (1987)] developed a model with the so-called "warm" ion-source temperature, i.e., "regular" ion source, under B&J's particular assumption that the ionization strength is proportional to the local electron density. However, it appears that B&J were not interested in determining the ionization length at all. The importance of this quantity to theoretical modeling was recognized by Riemann, who recently answered all the questions of the most advanced up-to-date plasma-sheath boundary theory with cold ions [K.-U. Riemann, Phys. Plasmas 13, 063508 (2006)] but still without the stiff warm ion-source case solution, which is highly resistant to solution via any available analytic method. The present article is an extension of H&T's results obtained for a single point only with ion source temperature Tn=0 to arbitrary finite ion source temperatures. The approach applied in this work is based on the method recently developed by Kos et al. [Phys. Plasmas 16, 093503 (2009)].

Electrostatic solitons in unmagnetized hot electron-positron-ion plasmas

International Nuclear Information System (INIS)

Mahmood, S.; Ur-Rehman, H.

2009-01-01

Linear and nonlinear electrostatic waves in unmagnetized electron-positron-ion (e-p-i) plasmas are studied. The electrons and positrons are assumed to be isothermal and dynamic while ions are considered to be stationary to neutralize the plasma background only. It is found that both upper (fast) and lower (slow) Langmuir waves can propagates in such a type of pair (e-p) plasma in the presence of ions. The small amplitude electrostatic Korteweg-de Vries (KdV) solitons are also obtained using reductive perturbation method. The electrostatic potential hump structures are found to exist when the temperature of the electrons is larger than the positrons, while the electrostatic potential dips are obtained in the reverse temperature conditions for electrons and positrons in e-p-i plasmas. The numerical results are also shown for illustration. The effects of different ion concentration and temperature ratios of electrons and positrons, on the formation of nonlinear electrostatic potential structures in e-p-i plasmas are also discussed.

Direct measurement of the plasma response to electrostatic ion waves

International Nuclear Information System (INIS)

Sarfaty, M.; DeSouza-Machado, S.; Skiff, F.

1995-01-01

Plasma wave-wave and wave-particle interactions are studied in a linear magnetized plasma. The relatively quiet plasma is produced by an argon gas-discharge. The plasma density is n e ≅ 10 9 cm -3 and the electron/ion temperatures are T e ≅ 5eV and T i = 0.05eV. A grid and a four ring antenna, both mounted on a scanning carriage, are used to launch electrostatic ion waves in the plasma. Laser Induced Fluorescence measurements of both the linear and the nonlinear plasma response to the wave fields are presented. The Vlasov-Poisson equations are used to explain the measured zero, first and second order terms of the ion distribution function in the presence of wave fields. In addition to the broadening (heating) of the ion distribution as the authors increase the wave amplitudes, induced plasma flows are observed both along and across the magnetic field

Behavior of lithium ions in the turbulent near-wall tokamak plasma under heating of ions and electrons of the main plasma

International Nuclear Information System (INIS)

Shurygin, R. V.; Morozov, D. Kh.

2014-01-01

Turbulent dynamics of the near-wall tokamak plasma is simulated by numerically solving the nonlinear reduced Braginskii magnetohydrodynamic equations with allowance for a lithium ion admixture. The effects of turbulence and radiation of the admixture are analyzed in the framework of a self-consistent approach. The radial distributions of the radiative loss power and the density of Li 0 atoms and Li +1 ions are obtained as functions of the electron and ion temperatures of the main plasma in the near-wall layer. The results of numerical simulations show that supply of lithium ions into the low-temperature near-wall plasma substantially depends on whether the additional power is deposited into the electron or ion component of the main plasma. If the electron temperature in the layer increases (ECR heating), then the ion density drops. At the same time, an increase in the temperature of the main ions (ICR heating) leads to an increase in the density of Li +1 ions. The results of numerical simulations are explained by the different influence of the electron and ion temperatures on the atomic processes governing the accumulation and loss of particles in the balance equations for neutral Li 0 atoms and Li +1 ions in the admixture. The radial profile of the electron temperature and the corresponding distribution of the radiative loss power for different densities of neutral Li 0 atoms on the wall are obtained. The calculations show that the presence of Li +1 ions affects turbulent transport of the main ions. In this case, the electron heat flux increases by 20–30% with increasing Li +1 density, whereas the flux of the main ions drops by nearly the same amount. The radial profile of the turbulent flux of lithium ions is obtained. It is demonstrated that the appearance of the pinch effect is related to the positive density gradient of lithium ions across the calculation layer. For the parameters of the T-10 tokamak, the effect of radiative cooling of the near-wall plasma

Solar wind contribution to the average population of energetic He+ and He++ ions in the Earth's magnetosphere

Directory of Open Access Journals (Sweden)

G. Kremser

1994-01-01

Full Text Available Measurements with the ion charge-energy-mass spectrometer CHEM on the AMPTE/CCE spacecraft were used to investigate the origin of energetic He+ and He++ ions observed in the equatorial plane at 3 ≤ L ≤ 9. Special emphasis was laid on the dependence of long-term average distributions on magnetic local time (MLT and the geomagnetic activity index Kp. The observations are described in terms of the phase space densities f1 (for He+ and f2 (for He++. They confirm preliminary results from a previous study: f1 is independent of MLT, whereas f2 is much larger on the nightside than on the dayside. They show, furthermore, that f1 increases slightly with Kp on intermediate drift shells, but decreases on high drift shells (L ≥ 7. f2 increases with Kp on all drift shells outside the premidnight sector. Within this sector a decrease is observed on high drift shells. A simple ion tracing code was developed to determine how and from where the ions move into the region of observations. It provides ion trajectories as a function of the ion charge, the magnetic moment and Kp. The ion tracing enables a distinction between regions of closed drift orbits (ring current and open convection trajectories (plasma sheet. It also indicates how the outer part of the observation region is connected to different parts of the more distant plasma sheet. Observations and tracing show that He++ ions are effectively transported from the plasma sheet on convection trajectories. Their distribution in the observation region corresponds to the distribution of solar wind ions in the plasma sheet. Thus, energetic He++ ions most likely originate in the solar wind. On the other hand, the plasma sheet is not an important source of energetic He+ ions. Convection trajectories more likely constitute a sink for He+ ions, which may diffuse onto them from closed drift orbits and then get lost through the magnetopause. An ionospheric origin of energetic He+ ions is unlikely as well, since

Ion acoustic waves in pair-ion plasma: Linear and nonlinear analyses

International Nuclear Information System (INIS)

Saeed, R.; Mushtaq, A.

2009-01-01

Linear and nonlinear properties of low frequency ion acoustic wave (IAW) in pair-ion plasma in the presence of electrons are investigated. The dispersion relation and Kadomtsev-Petviashvili equation for linear/nonlinear IAW are derived from sets of hydrodynamic equations where the ion pairs are inertial while electrons are Boltzmannian. The dispersion curves for various concentrations of electrons are discussed and compared with experimental results. The predicted linear IAW propagates at the same frequencies as those of the experimentally observed IAW if n e0 ∼10 4 cm -3 . It is found that nonlinear profile of the ion acoustic solitary waves is significantly affected by the percentage ratio of electron number density and temperature. It is also determined that rarefactive solitary waves can propagate in this system. It is hoped that the results presented in this study would be helpful in understanding the salient features of the finite amplitude localized ion acoustic solitary pulses in a laboratory fullerene plasma.

Energetic atomic and molecular ions of ionospheric origin observed in distant magnetotail flow-reversal events

Science.gov (United States)

Christon, S. P.; Gloeckler, G.; Williams, D. J.; Mukai, T.; Mcentire, R. W.; Jacquey, C.; Angelopoulos, V.; Lui, A. T. Y.; Kokubun, S.; Fairfield, D. H.

1994-01-01

Energetic atomic (O(+1) and N(+1)) and molecular (O2(+1), NO(+1), and N2(+1)) ions of ionospheric origin were observed in Earth's magnetotail at X approximately -146 R(sub E) during two plasma sheet sunward/tailward flow-reversal events measured by instruments on the GEOTAIL spacecraft. These events were associated with concurrent ground-measured geomagnetic disturbance intensification at auroral-and mid-latitudes (Kp = 7(-)). Energetic ions in the sunward-component and tailward flows were from both the solar wind and ionosphere. Plasma and energetic ions participated in the flows. During tailward flow, ionospheric origin ion abundance ratios at approximately 200-900 km/s in the rest frame were N(+1)/O(+1) = approximately 25-30% and ((O2(+1), NO(+1), and N2(+1))/O(+1) = approximately 1-2%. We argue that tailward flow most likely initiated approximately 80-100 R(sub E) tailward of Earth and molecular ions were in the plasma sheet prior to geomagnetic intensification onset.

Spatial structure of the plasma sheet boundary layer at distances greater than 180 RE as derived from energetic particle measurements on GEOTAIL

Directory of Open Access Journals (Sweden)

T. Yamamoto

Full Text Available We have analyzed the onsets of energetic particle bursts detected by the ICS and STICS sensors of the EPIC instrument on board the GEOTAIL spacecraft in the deep magnetotail (i.e., at distances greater than 180 RE. Such bursts are commonly observed at the plasma-sheet boundary layer (PSBL and are highly collimated along the magnetic field. The bursts display a normal velocity dispersion (i.e., the higher-speed particles are seen first, while the progressively lower speed particles are seen later when observed upon entry of the spacecraft from the magnetotail lobes into the plasma sheet. Upon exit from the plasma sheet a reverse velocity dispersion is observed (i.e., lower-speed particles disappear first and higher-speed particles disappear last. Three major findings are as follows. First, the tailward-jetting energetic particle populations of the distant-tail plasma sheet display an energy layering: the energetic electrons stream along open PSBL field lines with peak fluxes at the lobes. Energetic protons occupy the next layer, and as the spacecraft moves towards the neutral sheet progressively decreasing energies are encountered systematically. These plasma-sheet layers display spatial symmetry, with the plane of symmetry the neutral sheet. Second, if we consider the same energy level of energetic particles, then the H+ layer is confined within that of the energetic electron, the He++ layer is confined within that of the proton, and the oxygen layer is confined within the alpha particle layer. Third, whenever the energetic electrons show higher fluxes inside the plasma sheet as compared to those at the boundary layer, their angular distribution is isotropic irrespective of the Earthward or tailward character of fluxes, suggesting a closed field line topology.

Spatial structure of the plasma sheet boundary layer at distances greater than 180 RE as derived from energetic particle measurements on GEOTAIL

Directory of Open Access Journals (Sweden)

D. V. Sarafopoulos

1997-10-01

Full Text Available We have analyzed the onsets of energetic particle bursts detected by the ICS and STICS sensors of the EPIC instrument on board the GEOTAIL spacecraft in the deep magnetotail (i.e., at distances greater than 180 RE. Such bursts are commonly observed at the plasma-sheet boundary layer (PSBL and are highly collimated along the magnetic field. The bursts display a normal velocity dispersion (i.e., the higher-speed particles are seen first, while the progressively lower speed particles are seen later when observed upon entry of the spacecraft from the magnetotail lobes into the plasma sheet. Upon exit from the plasma sheet a reverse velocity dispersion is observed (i.e., lower-speed particles disappear first and higher-speed particles disappear last. Three major findings are as follows. First, the tailward-jetting energetic particle populations of the distant-tail plasma sheet display an energy layering: the energetic electrons stream along open PSBL field lines with peak fluxes at the lobes. Energetic protons occupy the next layer, and as the spacecraft moves towards the neutral sheet progressively decreasing energies are encountered systematically. These plasma-sheet layers display spatial symmetry, with the plane of symmetry the neutral sheet. Second, if we consider the same energy level of energetic particles, then the H+ layer is confined within that of the energetic electron, the He++ layer is confined within that of the proton, and the oxygen layer is confined within the alpha particle layer. Third, whenever the energetic electrons show higher fluxes inside the plasma sheet as compared to those at the boundary layer, their angular distribution is isotropic irrespective of the Earthward or tailward character of fluxes, suggesting a closed field line topology.

Ion deceleration in interpenetrating plasma jets

International Nuclear Information System (INIS)

Renner, O.; Krousky, E.; Larroche, O.; Liska, R.

2010-01-01

Complete text of publication follows. Inertial and magnetic confinement fusion schemes involve collisions of high-temperature plasma jets and their interaction with solid surfaces (the so-called plasma-wall interaction, PWI). A fundamental understanding of the PWI effects requires a detailed characterization of the transient collisional phenomena occurring in the interaction region. In this paper we discuss a PWI experiment with double-foil Al/Mg targets fielded at the PALS laser system. An energetic plasma jet was created at the rear (non-irradiated) side of the 0.8-μm-thick Al foil exploded by the main laser beam (50-200 J, 0.44/1.315 μm, 0.25-0.3 ns, 16 W/cm 2 ). This plasma jet streamed towards the 2-μm-thick Mg foil, where the secondary plasma was created either by an auxiliary 5 J laser beam or by the main laser radiation transmitted through the Al foil, together with radiation and particles emitted from the Al foil. The environmental conditions in the plasma were diagnosed by means of high-resolution x-ray spectroscopy and temporally-resolved x-ray imaging. For the first time, the deceleration of the incident Al ions in the near-wall region was directly observed and quantitatively characterized from the Doppler shift of the J-satellite from the Al Lyα spectral group. The interaction scenario was numerically modeled by two concerted codes, namely, i) the Prague Arbitrary Lagrangian Eulerian 2-D code PALE, which solves the Lagrangian mesh distortions by smoothing and conservative remapping of conserved quantities, and ii) the multispecies 1.5-D code MULTIF which models the hydrodynamics of an arbitrary number of interpenetrating ion species in a single space dimension while assuming self-similar plasma expansion in the other directions, and taking into account detailed Coulombian collisional processes. PALE was used to model two counter-streaming Al/Mg plasma plumes until the beginning of their interaction, and the resulting plasma state was then used as

Study of the negative ion extraction mechanism from a double-ion plasma in negative ion sources

International Nuclear Information System (INIS)

Goto, I.; Nishioka, S.; Hatayama, A.; Miyamoto, K.

2015-01-01

We have developed a 2D3V-PIC model of the extraction region, aiming to clarify the basic extraction mechanism of H − ions from the double-ion plasma in H − negative ion sources. The result shows the same tendency of the H − ion density n H − as that observed in the experiments, i.e.,n H − in the upstream region away from the plasma meniscus (H − emitting surface) has been reduced by applying the extraction voltage. At the same time, relatively slow temporal oscillation of the electric potential compared with the electron plasma frequency has been observed in the extraction region. Results of the systematic study using a 1D3V-PIC model with the uniform magnetic field confirm the result that the electrostatic oscillation is identified to be lower hybrid wave. The effect of this oscillation on the H − transport will be studied in the future

Study of the negative ion extraction mechanism from a double-ion plasma in negative ion sources

Energy Technology Data Exchange (ETDEWEB)

Goto, I.; Nishioka, S.; Hatayama, A. [Graduate school of Science and Technology, Keio University, 3-14-1 Hiyoshi, Kohoku-ku, Yokohama 223-8522 (Japan); Miyamoto, K. [Naruto University of Education, 748 Nakashima, Takashima, Naruto-cho, Naruto-shi, Tokushima 772-8502 (Japan)

2015-04-08

We have developed a 2D3V-PIC model of the extraction region, aiming to clarify the basic extraction mechanism of H{sup −} ions from the double-ion plasma in H{sup −} negative ion sources. The result shows the same tendency of the H{sup −} ion density n{sub H{sup −}} as that observed in the experiments, i.e.,n{sub H{sup −}} in the upstream region away from the plasma meniscus (H{sup −} emitting surface) has been reduced by applying the extraction voltage. At the same time, relatively slow temporal oscillation of the electric potential compared with the electron plasma frequency has been observed in the extraction region. Results of the systematic study using a 1D3V-PIC model with the uniform magnetic field confirm the result that the electrostatic oscillation is identified to be lower hybrid wave. The effect of this oscillation on the H{sup −} transport will be studied in the future.

Average energetic ion flux variations associated with geomagnetic activity from EPIC/STICS on Geotail

Science.gov (United States)

Christon, S. P.; Gloeckler, G.; Eastman, T. E.; McEntire, R. W.; Roelef, E. C.; Lui, A. T. Y.; Williams, D. J.; Frank, L. A.; Paterson, W. R.; Kokubun, S.;

Microwave plasma source having improved switching operation from plasma ignition phase to normal ion extraction phase

International Nuclear Information System (INIS)

Sakudo, N.; Abe, K.; Koike, H.; Okada, O.; Tokiguchi, K.

1985-01-01

In a microwave plasma source, a discharge space supplied with a microwave electric field is supplied with a DC magnetic field. A material to be ionized is introduced into the discharge space to produce plasma, whereby ions are extracted through an ion extracting system. A switch is provided for effecting through switching operation the change-over of the magnetic field applied to the discharge space from the intensity for the ignition of plasma to the intensity for ion extraction in succession to completion of the plasma ignition

Ion Streaming Instabilities in Pair Ion Plasma and Localized Structure with Non-Thermal Electrons

Science.gov (United States)

Nasir Khattak, M.; Mushtaq, A.; Qamar, A.

2015-12-01

Pair ion plasma with a fraction of non-thermal electrons is considered. We investigate the effects of the streaming motion of ions on linear and nonlinear properties of unmagnetized, collisionless plasma by using the fluid model. A dispersion relation is derived, and the growth rate of streaming instabilities with effect of streaming motion of ions and non-thermal electrons is calculated. A qausi-potential approach is adopted to study the characteristics of ion acoustic solitons. An energy integral equation involving Sagdeev potential is derived during this process. The presence of the streaming term in the energy integral equation affects the structure of the solitary waves significantly along with non-thermal electrons. Possible application of the work to the space and laboratory plasmas are highlighted.

Ion streaming instabilities in pair ion plasma and localized structure with non-thermal electrons

Energy Technology Data Exchange (ETDEWEB)

Khattak, M. Nasir; Qamar, A., E-mail: mnnasirphysics@gmail.com [Department of Physics, University of Peshawar (Pakistan); Mushtaq, A. [Department of Physics, Abdul Wali Khan University Mardan, National Center for Physics, Mardan (Pakistan)

2015-12-15

Pair ion plasma with a fraction of non-thermal electrons is considered. We investigate the effects of the streaming motion of ions on linear and nonlinear properties of unmagnetized, collisionless plasma by using the fluid model. A dispersion relation is derived, and the growth rate of streaming instabilities with effect of streaming motion of ions and non-thermal electrons is calculated. A quasi-potential approach is adopted to study the characteristics of ion acoustic solitons. An energy integral equation involving Sagdeev potential is derived during this process. The presence of the streaming term in the energy integral equation affects the structure of the solitary waves significantly along with non-thermal electrons. Possible application of the work to the space and laboratory plasmas are highlighted. (author)

Ion Distribution Measurement In Plasma Focus

International Nuclear Information System (INIS)

Suryadi; Sunardi; Usada, Widdi; Purwadi, Agus; Zaenuri, Akhmad

1996-01-01

Measurement of the Argon ion distribution in plasma focus by using Faraday cup has been done. The intensity of ion beam followed the I Rn rule, n=1,02. In the operation condition of 0,8 mbar and 12,5 kV the current sheath spen 2.2 to 2.4 μsecond in the rundown phase. Cu ion was also been observed in the Faraday cup

Preliminary scaling laws for plasma current, ion kinetic temperature, and plasma number density in the NASA Lewis bumpy torus plasma

Science.gov (United States)

Roth, J. R.

1976-01-01

Parametric variation of independent variables which may affect the characteristics of bumpy torus plasma have identified those which have a significant effect on the plasma current, ion kinetic temperature, and plasma number density, and those which do not. Empirical power law correlations of the plasma current, and the ion kinetic temperature and number density were obtained as functions of potential applied to the midplane electrode rings, the background neutral gas pressure, and the magnetic field strength. Additional parameters studied included the type of gas, the polarity of the midplane electrode rings, the mode of plasma operation, and the method of measuring the plasma number density. No significant departures from the scaling laws appear to occur at the highest ion kinetic temperatures or number densities obtained to date.

Ion sampling and transport in Inductively Coupled Plasma Mass Spectrometry

Science.gov (United States)

Farnsworth, Paul B.; Spencer, Ross L.

2017-08-01

Quantitative accuracy and high sensitivity in inductively coupled plasma mass spectrometry (ICP-MS) depend on consistent and efficient extraction and transport of analyte ions from an inductively coupled plasma to a mass analyzer, where they are sorted and detected. In this review we examine the fundamental physical processes that control ion sampling and transport in ICP-MS and compare the results of theory and computerized models with experimental efforts to characterize the flow of ions through plasma mass spectrometers' vacuum interfaces. We trace the flow of ions from their generation in the plasma, into the sampling cone, through the supersonic expansion in the first vacuum stage, through the skimmer, and into the ion optics that deliver the ions to the mass analyzer. At each stage we consider idealized behavior and departures from ideal behavior that affect the performance of ICP-MS as an analytical tool.

Multispecies Weibel Instability for Intense Ion Beam Propagation Through Background Plasma

CERN Document Server

Davidson, Ronald C; Kaganovich, Igor D; Qin, Hong; Startsev, Edward

2005-01-01

In application of heavy ion beams to high energy density physics and fusion, background plasma is utilized to neutralize the beam space charge during drift compression and/or final focus of the ion beam. It is important to minimize the deleterious effects of collective instabilities on beam quality associated with beam-plasma interactions. Plasma electrons tend to neutralize both the space charge and current of the beam ions. It is shown that the presence of the return current greatly modifies the electromagnetic Weibel instability (also called the filamentation instability), i.e., the growth rate of the filamentation instability greatly increases if the background ions are much lighter than the beam ions and the plasma density is comparable to the ion beam density. This may preclude using underdense plasma of light gases in heavy ion beam applications. It is also shown that the return current may be subject to the fast electrostatic two-stream instability.

Collisionless current sheet equilibria

Science.gov (United States)

Neukirch, T.; Wilson, F.; Allanson, O.

2018-01-01

Current sheets are important for the structure and dynamics of many plasma systems. In space and astrophysical plasmas they play a crucial role in activity processes, for example by facilitating the release of magnetic energy via processes such as magnetic reconnection. In this contribution we will focus on collisionless plasma systems. A sensible first step in any investigation of physical processes involving current sheets is to find appropriate equilibrium solutions. The theory of collisionless plasma equilibria is well established, but over the past few years there has been a renewed interest in finding equilibrium distribution functions for collisionless current sheets with particular properties, for example for cases where the current density is parallel to the magnetic field (force-free current sheets). This interest is due to a combination of scientific curiosity and potential applications to space and astrophysical plasmas. In this paper we will give an overview of some of the recent developments, discuss their potential applications and address a number of open questions.

Development of long lifetime-high current plasma cathode ion source

International Nuclear Information System (INIS)

Yabe, Eiji; Takayama, Kazuo; Fukui, Ryota.

1987-01-01

A long lifetime ion source with plasma cathode has been developed for use in ion implantation. In this ion source, a plasma of a nonreactive working gas serves as a cathode in place of a thermionic tungsten filament used in the Freeman ion source. In an applied magnetic field, the plasma cathode is convergent, i.e. filament-like; in zero magnetic field, it turns divergent and spray-like. In the latter case, the plasma exhibits a remarkable ability when the working gas has an ionization potential larger than the feed gas. By any combination of a working gas of either argon or neon and a feed gas of AsF 5 or PF 5 , the lifetime of this ion source was found to be more than 90 hours with an extraction voltage of 40 kV and the corresponding ion current density 20 mA/cm 2 . Mass spectrometry results show that this ion source has an ability of generating a considerable amount of As + and P + ions from AsF 5 and PF 5 , and hence will be useful for realizing a fully cryopumped ion implanter system. This ion source is eminently suitable for use in oxygen ion production. (author)

Generation mechanism of the whistler-mode waves in the plasma sheet prior to magnetic reconnection

Czech Academy of Sciences Publication Activity Database

Wei, X. H.; Cao, J. B.; Zhou, G. C.; Fu, H. S.; Santolík, Ondřej; Reme, H.; Dandouras, I.; Cornilleau, N.; Fazakerley, A.

2013-01-01

Roč. 52, č. 1 (2013), s. 205-210 ISSN 0273-1177 Institutional support: RVO:68378289 Keywords : whistler-mode waves * electron temperature anisotropy * Reconnection * the plasma sheet Subject RIV: BL - Plasma and Gas Discharge Physics Impact factor: 1.238, year: 2013 http://www.sciencedirect.com/science/article/pii/S0273117713001221

Energetic ion emission in a positive polarity nanosecond plasma opening switch

Energy Technology Data Exchange (ETDEWEB)

Sarfaty, M [Univ. of Wisconsin, Madison, WI (United States); Krasik, Ya E; Weingarten, A; Fruchtman, A; Maron, Y [Weizmann Institute of Science, Rehovot (Israel). Department of Physics

1997-12-31

The emission was studied of energetic ions from the plasma in a coaxial Plasma Opening Switch (POS) powered by a 300 kV, 15 kA, 90 ns positive polarity pulse. Fluxes lasting 2 - 3 ns of ions flowing radially onto the cathode were observed at all axial locations of the switch plasma within 5 ns of the beginning of the upstream POS current. It is suggested that the termination of this ion flux is due to the formation of a cathode plasma, which is consistent with our spectroscopic measurements. Later in the pulse, longer duration (100 ns) ion fluxes were observed radially, first appearing in the generator side of the switch plasma. Fluxes 30 - 40 ns long of ions flowing axially towards the POS load at velocities (2{+-}1) x 10{sup 8} cm/s were also observed. The dependences of the start time of the axial ion flow, of the ion velocities, and of the ion flux on the POS operation parameters were studied. (author). 6 figs., 5 refs.

Energetic ion emission in a positive polarity nanosecond plasma opening switch

International Nuclear Information System (INIS)

Sarfaty, M.; Krasik, Ya.E.; Weingarten, A.; Fruchtman, A.; Maron, Y.

1996-01-01

The emission was studied of energetic ions from the plasma in a coaxial Plasma Opening Switch (POS) powered by a 300 kV, 15 kA, 90 ns positive polarity pulse. Fluxes lasting 2 - 3 ns of ions flowing radially onto the cathode were observed at all axial locations of the switch plasma within 5 ns of the beginning of the upstream POS current. It is suggested that the termination of this ion flux is due to the formation of a cathode plasma, which is consistent with our spectroscopic measurements. Later in the pulse, longer duration (100 ns) ion fluxes were observed radially, first appearing in the generator side of the switch plasma. Fluxes 30 - 40 ns long of ions flowing axially towards the POS load at velocities (2±1) x 10 8 cm/s were also observed. The dependences of the start time of the axial ion flow, of the ion velocities, and of the ion flux on the POS operation parameters were studied. (author). 6 figs., 5 refs

Quasi-adiabatic particle acceleration in a magnetic field reversals and the formation of the plasma sheet boundary layer in the earth's magnetotail

International Nuclear Information System (INIS)

Zelenyi, L.M.; Vogin, D.V.; Buechner, J.

1989-01-01

Two types of regularity exist for the particle motion in the two-dimensional magnetic field reversals (MFR) with the strongly curves magnetic field lines - the usual adiabatic and another one which we called 'quasiadiabatic'. Here we consider the acceleration of MFR particles in stationary and homogeneous electric field induced by the motion of MFR through the ambient plasma (i.e. solar wind). Assuming that the time scale of acceleration is slow in comparison with the period of orbital motion we introduce the new longitudinal invariant I κ . This enables to describe the process of acceleration in a closed form and to obtain for the first time the laws governing the quasiadiabatic ion acceleration in the Earth's mangetotail. The similarities and differences in adiabatic and quasiadiabatic acceleration mechanisms are discussed. The obtained results give and important insights to the problem of the particle heating in hte Earth's magnetotail and to the formation of accelerated plasma streams along the edges of the plasma sheet. (author). 17 refs.; 7 figs

Observation of enhanced electric field in an RF-plugged sheet plasma in the RFC-XX-M open-ended machine

International Nuclear Information System (INIS)

Oda, T.; Takiyama, K.; Kadota, K.

1987-12-01

We report nonperturbing observation of the electric field in the sheet plasma for RF end-plugging on the RFC XX-M open-ended machine by using the Stark effect with a combined technique of beam-probe and laser-induced fluorescence. Under the optimum condition for the RF plugging, enhanced electric field is found in the sheet plasma by about 2.5 times with respect to the electric field when no plasma is produced. The field spatial profile is also measured, which is discussed in connection with the electrostatic eigenmode. (author)

Numerical simulation of plasma processes driven by transverse ion heating

Science.gov (United States)

Singh, Nagendra; Chan, C. B.

1993-01-01

The plasma processes driven by transverse ion heating in a diverging flux tube are investigated with numerical simulation. The heating is found to drive a host of plasma processes, in addition to the well-known phenomenon of ion conics. The downward electric field near the reverse shock generates a doublestreaming situation consisting of two upflowing ion populations with different average flow velocities. The electric field in the reverse shock region is modulated by the ion-ion instability driven by the multistreaming ions. The oscillating fields in this region have the possibility of heating electrons. These results from the simulations are compared with results from a previous study based on a hydrodynamical model. Effects of spatial resolutions provided by simulations on the evolution of the plasma are discussed.

Integrated heat transport simulation of high ion temperature plasma of LHD

International Nuclear Information System (INIS)

Murakami, S.; Yamaguchi, H.; Sakai, A.

2014-10-01

A first dynamical simulation of high ion temperature plasma with carbon pellet injection of LHD is performed by the integrated simulation GNET-TD + TASK3D. NBI heating deposition of time evolving plasma is evaluated by the 5D drift kinetic equation solver, GNET-TD and the heat transport of multi-ion species plasma (e, H, He, C) is studied by the integrated transport simulation code, TASK3D. Achievement of high ion temperature plasma is attributed to the 1) increase of heating power per ion due to the temporal increase of effective charge, 2) reduction of effective neoclassical transport with impurities, 3) reduction of turbulence transport. The reduction of turbulence transport is most significant contribution to achieve the high ion temperature and the reduction of the turbulent transport from the L-mode plasma (normal hydrogen plasma) is evaluated to be a factor about five by using integrated heat transport simulation code. Applying the Z effective dependent turbulent reduction model we obtain a similar time behavior of ion temperature after the C pellet injection with the experimental results. (author)

Drift wave in pair-ion plasma

Indian Academy of Sciences (India)

of charged particles in electromagnetic fields. The linear and nonlinear collective modes in electron-positron plasma have been investigated theoretically [3–6]. Recently, Oohara and Hatakeyama [7] have developed a novel method for generating a pair plasma con- sisting of only negative and positive ions with equal mass ...

Modes of spheroidal ion plasmas at the Brillouin limit

International Nuclear Information System (INIS)

Tinkle, M.D.; Greaves, R.G.; Surko, C.M.

1996-01-01

The confinement properties and collective modes of single-component plasmas are investigated in a quadrupole Penning trap. Brillouin-density pure ion plasmas are generated by electron-beam ionization of a low-pressure gas. Large, spheroidal, steady-state plasmas are produced, extending out to contact one or more of the trap electrodes. With the density fixed at the Brillouin limit by the high ion production rate, the electrode potentials determine the plasma shape. The frequencies of azimuthally propagating cyclotron and diocotron modes are found to vary significantly with the plasma aspect ratio. For oblate plasmas, the frequencies are in good agreement with a simple fluid model. copyright 1996 American Institute of Physics

Carbon-wrapped MnO nanodendrites interspersed on reduced graphene oxide sheets as anode materials for lithium-ion batteries

Energy Technology Data Exchange (ETDEWEB)

Liu, Boli; Li, Dan; Liu, Zhengjiao; Gu, Lili; Xie, Wenhe; Li, Qun; Guo, Pengqian; Liu, Dequan; He, Deyan, E-mail: hedy@lzu.edu.cn

2017-02-01

Highlights: • The C-MnO/rGO composites were anchored on nickel foam by a facile vacuum filtration and a subsequent thermal treatment. • The novel architecture of anodes effectively improved the electrochemical performance of lithium ion battery. • The active MnO nanodendrites became smaller nanoparticles still wrapped in graphene sheets after cycles. - Abstract: Carbon-wrapped MnO nanodendrites interspersed on reduced graphene oxide sheets (C-MnO/rGO) were prepared on nickel foam by a facile vacuum filtration and a subsequent thermal treatment. As a binder-free anode of lithium-ion battery, the nanodendritic structure of C-MnO accommodates the huge volume expansion and shortens the diffusion length for lithium ion and electron, rGO sheets prevent C-MnO nanodendites from aggregation and offer a good electronic conduction. As a result, the electrode with such a novel architecture delivers superior electrochemical properties including high reversible capacity, excellent rate capability and cycle stability. Moreover, MnO nanodendrites change to nanoparticles wrapped in graphene sheets during the lithiation/delithiation process, which is a more beneficial microstructure to further increase the specific capacity and cycle life of the electrode.

Acoustic nonlinear periodic waves in pair-ion plasmas

Science.gov (United States)

Mahmood, Shahzad; Kaladze, Tamaz; Ur-Rehman, Hafeez

2013-09-01

Electrostatic acoustic nonlinear periodic (cnoidal) waves and solitons are investigated in unmagnetized pair-ion plasmas consisting of same mass and oppositely charged ion species with different temperatures. Using reductive perturbation method and appropriate boundary conditions, the Korteweg-de Vries (KdV) equation is derived. The analytical solutions of both cnoidal wave and soliton solutions are discussed in detail. The phase plane plots of cnoidal and soliton structures are shown. It is found that both compressive and rarefactive cnoidal wave and soliton structures are formed depending on the temperature ratio of positive and negative ions in pair-ion plasmas. In the special case, it is revealed that the amplitude of soliton may become larger than it is allowed by the nonlinear stationary wave theory which is equal to the quantum tunneling by particle through a potential barrier effect. The serious flaws in the earlier published results by Yadav et al., [PRE 52, 3045 (1995)] and Chawla and Misra [Phys. Plasmas 17, 102315 (2010)] of studying ion acoustic nonlinear periodic waves are also pointed out.

Transition from the constant ion mobility regime to the ion-atom charge-exchange regime for bounded collisional plasmas

International Nuclear Information System (INIS)

Poggie, Jonathan; Sternberg, Natalia

2005-01-01

A numerical and analytical study of a planar, collisional, direct-current, plasma-wall problem is presented. The fluid model for the problem is first validated by comparing numerical solutions with experimental data for low-pressure (∼0.1 Pa) electrode sheaths with wall potentials on the order of -100 V. For electric potential, ion number density, and ion velocity, good agreement was found between theory and experiment from within the sheath out to the bulk plasma. The frictional drag resulting from ion-neutral collisions is described by a model incorporating both linear and quadratic velocity terms. In order to study the transition from the constant ion mobility regime (linear friction) to the ion-atom charge-exchange collision regime (quadratic friction), the theoretical model was examined numerically for a range of ion temperatures and ion-neutral collision rates. It was found that the solution profiles in the quasineutral plasma depend on the ion temperature. For low ion temperatures they are governed mainly by the ion-atom charge-exchange regime, whereas for high temperatures they are governed by the constant ion mobility regime. Quasineutral plasma models corresponding to these two limiting cases were solved analytically. In particular, an analytical plasma solution is given for the ion-atom charge exchange regime that includes the effects of ion inertia. In contrast to the quasineutral plasma, the sheath is always governed for low to moderate collision rates by the ion-atom charge-exchange regime, independent of the ion temperature. Varying the collision rate, it was shown that when the wall potential is sufficiently high, the sheath cannot be considered collisionless, even if the collision rate is quite small

Ion accumulation in an electron plasma confined on magnetic surfaces

International Nuclear Information System (INIS)

Berkery, John W.; Marksteiner, Quinn R.; Pedersen, Thomas Sunn; Kremer, Jason P.

2007-01-01

Accumulation of ions can alter and may destabilize the equilibrium of an electron plasma confined on magnetic surfaces. An analysis of ion sources and ion content in the Columbia Non-neutral Torus (CNT) [T.S. Pedersen, J.P. Kremer, R.G. Lefrancois, Q. Marksteiner, N. Pomphrey, W. Reiersen, F. Dahlgreen, and X. Sarasola, Fusion Sci. Technol. 50, 372 (2006)] is presented. In CNT ions are created preferentially at locations of high electron temperature, near the outer magnetic surfaces. A volumetric integral of n e ν iz gives an ion creation rate of 2.8x10 11 ions/s. This rate of accumulation would cause neutralization of a plasma with 10 11 electrons in about half a second. This is not observed experimentally, however, because currently in CNT ions are lost through recombination on insulated rods. From a steady-state balance between the calculated ion creation and loss rates, the equilibrium ion density in a 2x10 -8 Torr neutral pressure, 7.5x10 11 m -3 electron density plasma in CNT is calculated to be n i =6.2x10 9 m -3 , or 0.8%. The ion density is experimentally measured through the measurement of the ion saturation current on a large area probe to be about 6.0x10 9 m -3 for these plasmas, which is in good agreement with the predicted value

Modes of spheroidal ion plasmas at the Brillouin limit

International Nuclear Information System (INIS)

Tinkle, M. D.; Greaves, R. G.; Surko, C. M.

1995-01-01

Brillouin-density pure ion plasmas have been generated in a quadrupole Penning tray by electron-beam ionization of a low-pressure gas. Large, spheroidal, steady-state plasmas are produced that extend to one of the trap electrodes. With the density fixed at the Brillouin limit by the high ion production rate, the electrode potentials determine the plasma shape. The frequencies of azimuthally propagating cyclotron and diocotron modes are found to vary significantly with the plasma aspect ratio. For oblate plasmas, we are able to test theoretical predictions of a simple fluid model, and the frequencies are in good agreement

Ferroelectric Plasma Source for Heavy Ion Beam Charge Neutralization

CERN Document Server

Efthimion, Philip; Gilson, Erik P; Grisham, Larry; Logan, B G; Waldron, William; Yu, Simon

2005-01-01

Plasmas are employed as a medium for charge neutralizing heavy ion beams to allow them to focus to a small spot size. Calculations suggest that plasma at a density of 1-100 times the ion beam density and at a length ~ 0.1-1 m would be suitable. To produce 1 meter plasma, large-volume plasma sources based upon ferroelectric ceramics are being considered. These sources have the advantage of being able to increase the length of the plasma and operate at low neutral pressures. The source will utilize the ferroelectric ceramic BaTiO3 to form metal plasma. The drift tube inner surface of the Neutralized Drift Compression Experiment (NDCX) will be covered with ceramic. High voltage (~ 1-5 kV) is applied between the drift tube and the front surface of the ceramic by placing a wire grid on the front surface. A prototype ferroelectric source 20 cm long produced plasma densities ~ 5x1011 cm-3. The source was integrated into the experiment and successfully charge neutralized the K ion beam. Presently, the 1 meter source ...

A collisional model for plasma immersion ion implantation

International Nuclear Information System (INIS)

Vahedi, V.; Lieberman, M.A.; Alves, M.V.; Verboncoeur, J.P.; Birdsall, C.K.

1990-01-01

In plasma immersion ion implantation, a target is immersed in a plasma and a series of negative short pulses are applied to it to implant the ions. A new analytical model is being developed for the high pressure regimes in which the motion of the ions is highly collisional. The model provides values for ion flux, average ion velocity at the target, and sheath edge motion as a function of time. These values are being compared with those obtained from simulation and show good agreement. A review is also given (for comparison) of the earlier work done at low pressures, where the motion of ions in the sheath is collisionless, also showing good agreement between analysis and simulation. The simulation code is PDP1 which utilizes particle-in-cell techniques plus Monte-Carlo simulation of electron-neutral (elastic, excitation and ionization) and ion-neutral (scattering and charge-exchange) collisions

ASYMMETRIC MAGNETIC RECONNECTION IN WEAKLY IONIZED CHROMOSPHERIC PLASMAS

International Nuclear Information System (INIS)

Murphy, Nicholas A.; Lukin, Vyacheslav S.

2015-01-01

Realistic models of magnetic reconnection in the solar chromosphere must take into account that the plasma is partially ionized and that plasma conditions within any two magnetic flux bundles undergoing reconnection may not be the same. Asymmetric reconnection in the chromosphere may occur when newly emerged flux interacts with pre-existing, overlying flux. We present 2.5D simulations of asymmetric reconnection in weakly ionized, reacting plasmas where the magnetic field strengths, ion and neutral densities, and temperatures are different in each upstream region. The plasma and neutral components are evolved separately to allow non-equilibrium ionization. As in previous simulations of chromospheric reconnection, the current sheet thins to the scale of the neutral–ion mean free path and the ion and neutral outflows are strongly coupled. However, the ion and neutral inflows are asymmetrically decoupled. In cases with magnetic asymmetry, a net flow of neutrals through the current sheet from the weak-field (high-density) upstream region into the strong-field upstream region results from a neutral pressure gradient. Consequently, neutrals dragged along with the outflow are more likely to originate from the weak-field region. The Hall effect leads to the development of a characteristic quadrupole magnetic field modified by asymmetry, but the X-point geometry expected during Hall reconnection does not occur. All simulations show the development of plasmoids after an initial laminar phase

Pulsed, Inductively Generated, Streaming Plasma Ion Source for Heavy Ion Fusion Linacs

International Nuclear Information System (INIS)

Steven C. Glidden; Howard D Sanders; John B. Greenly; Daniel L. Dongwoo

2006-01-01

This report describes a compact, high current density, pulsed ion source, based on electrodeless, inductively driven gas breakdown, developed to meet the requirements on normalized emittance, current density, uniformity and pulse duration for an ion injector in a heavy-ion fusion driver. The plasma source produces >10 (micro)s pulse of Argon plasma with ion current densities >100 mA/cm2 at 30 cm from the source and with strongly axially directed ion energy of about 80 eV, and sub-eV transverse temperature. The source has good reproducibility and spatial uniformity. Control of the current density during the pulse has been demonstrated with a novel modulator coil method which allows attenuation of the ion current density without significantly affecting the beam quality. This project was carried out in two phases. Phase 1 used source configurations adapted from light ion sources to demonstrate the feasibility of the concept. In Phase 2 the performance of the source was enhanced and quantified in greater detail, a modulator for controlling the pulse shape was developed, and experiments were conducted with the ions accelerated to >40 kV

Correlated ion stopping in plasmas

International Nuclear Information System (INIS)

Zwicknagel, G.; Deutsch, C.

1997-01-01

The basic features of correlated ion stopping in plasmas are demonstrated by employing two opposite extremes of cluster structures, a statistical model with a spatial ion distribution of Gaussian shape and the highly regular configuration of N-ion chains and cubic boxes. In the case of the ion chains the resonant character of correlated stopping due to the interference of the excited wake fields is discussed in detail. The general behavior of correlation effects is summarized and its dependence on the ratio of cluster size and interion spacing to the screening length in the plasma, as well as the ratio of the cluster velocity to the mean electron velocity in the target, is stressed out. The validity and applicability of the dielectric response formalism used for describing correlated stopping is critically reviewed. A scheme is presented to extend the linear formalism to weak nonlinear situations that occur, in particular, for small highly charged clusters at moderate or low velocities. For the Gaussian cluster a fit formula is given, which allows a fast and accurate calculation of the enhancement of stopping due to correlation effects and applies for all degrees of degeneracy of the electrons and arbitrary cluster velocities. copyright 1997 The American Physical Society

Atomic collisions in fusion plasmas involving multiply charged ions

International Nuclear Information System (INIS)

Salzborn, E.

1980-01-01

A short survey is given on atomic collisions involving multiply charged ions. The basic features of charge transfer processes in ion-ion and ion-atom collisions relevant to fusion plasmas are discussed. (author)

Plasma kinetics around a dust grain in an ion flow

International Nuclear Information System (INIS)

Maiorov, S.A.; Vladimirov, S.V.; Cramer, N.F.

2000-01-01

Full text: In a typical laboratory discharge, dust particles are negatively charged and usually levitate in the sheath or pre-sheath region under the balance of gravitational, electrostatic (due to the sheath electric field) and plasma (such as the ion drag) forces. The ion flow provides not only a direct (dragging) influence, but is also responsible for the generation of associated collective plasma processes which can strongly affect the vertical arrangement of the dust grains. The complete problem of the plasma dynamics around a macroscopic body in the presence of plasma flows is highly nonlinear and therefore its numerical analysis is of major importance. Among various numerical methods, direct integration of the equations of motion of the plasma particles represents a numerical experiment whose significance approaches experiments in the laboratory. Here, we present for the first time the results of a self-consistent molecular dynamics (MD) three-dimensional (3D) simulation of the kinetics of plasma particles (electrons and ions) around a dust grain, taking into account the dust charging. The core of the method includes consideration of the time evolution of the system consisting of positively ('ions') and negatively ('electrons') charged particles confined in a simulation box together with a macroscopic absorbing grain ('dust particle') with infinite mass and an initial (negative) charge. The ions are introduced in the system as a uniform flow defined by its Mach number and the ion temperature. The paths of the ions and electrons are determined through numerical integration of the equations of motion. We demonstrate that the plasma kinetics around a dust grain in the presence of an ion flow involves a strong ion focusing behind the grain. We have also confirmed that the most important of the processes involved is the ion time-scale; the kinetics of the electrons follows a Boltzmann distribution with good agreement. We note that the time constraints involved

Interaction of energetic ions with high-density plasmas

International Nuclear Information System (INIS)

Gericke, D.O.; Edie, D.; Grinenko, A.; Vorberger, J.

2010-01-01

Complete text of publication follows. The talk will review the importance of energetic ions in different inertial confinement fusion scenarios: i) heavy ion beams are very efficient drivers that can deliver the energy for compression in indirect as well as direct drive approaches; ii) the interaction of α-particles, that are created in a burning plasma, with the surrounding cold plasma is essential for creating a burn wave; iii) laser-produced ion beams are also a strong candidate to create the hot spot needed for fast ignition. In all applications the ions interact with dense matter that is characterized by strongly coupled ions and (possibly) partially degenerate electrons. Moreover, the coupling between beam ions and target electrons can be strong as well. Under these conditions, standard approaches for the beam-plasma interactions process are known to fail. The presentation will demonstrate how advanced models for the energy loss of ions in dense plasmas can resolve the issues mentioned above. These models are largely built on quantum kinetic theory that is able to describe degeneracy and strong coupling in a systematic way. In particular, strong interactions require a quantum description for electron-ion collisions in dense plasma environments, which is done by direct solutions of the Schroedinger equation. Degeneracy and collective excitations can be included via the Lenard-Balescu description where strong interactions may be included via a pseudo-potential approach. Finally, results are shown for all three fusion applications described above. The effects related to strong coupling and degeneracy mainly concern the end of the stopping range where the beam ion dose not have enough energy to excite all possible degrees of freedom and, thus, certain processes are frozen out. However, we also find a significant reduction of the range for swift heavy ions in the GeV-range when stopping in dense matter is considered. The stopping range of α-particles in the

Planar and nonplanar ion acoustic shock waves in relativistic degenerate astrophysical electron-positron-ion plasmas

Energy Technology Data Exchange (ETDEWEB)

Ata-ur-Rahman,; Qamar, A. [Institute of Physics and Electronics, University of Peshawar, Peshawar 25000 (Pakistan); National Centre for Physics, QAU Campus, Shahdrah Valley Road, Islamabad 44000 (Pakistan); Ali, S. [National Centre for Physics, QAU Campus, Shahdrah Valley Road, Islamabad 44000 (Pakistan); Mirza, Arshad M. [Theoretical Plasma Physics Group, Physics Department, Quaid-i-Azam University, Islamabad 45320 (Pakistan)

2013-04-15

We have studied the propagation of ion acoustic shock waves involving planar and non-planar geometries in an unmagnetized plasma, whose constituents are non-degenerate ultra-cold ions, relativistically degenerate electrons, and positrons. By using the reductive perturbation technique, Korteweg-deVries Burger and modified Korteweg-deVries Burger equations are derived. It is shown that only compressive shock waves can propagate in such a plasma system. The effects of geometry, the ion kinematic viscosity, and the positron concentration are examined on the ion acoustic shock potential and electric field profiles. It is found that the properties of ion acoustic shock waves in a non-planar geometry significantly differ from those in planar geometry. The present study has relevance to the dense plasmas, produced in laboratory (e.g., super-intense laser-dense matter experiments) and in dense astrophysical objects.

Dynamical chaos of plasma ions in electrostatic waves

International Nuclear Information System (INIS)

Fasoli, A.; Kleiber, R.; Tran, M.Q.; Paris, P.J.; Skiff, F.

1992-09-01

Chaos generated by the interaction between charged particles and electrostatic plasma waves has been observed in a linear magnetized plasma. The macroscopic wave properties, the kinetic ion dielectric response and the microscopic heating mechanisms have been investigated via optical diagnostic techniques based on laser induced fluorescence. Observations of test-particle dynamical evolution indicate an exponential separation of initially close ion trajectories. (author) 5 figs., 20 refs

Measurements of ion temperature and flow of pulsed plasmas produced by a magnetized coaxial plasma gun device using an ion Doppler spectrometer

Science.gov (United States)

Kitagawa, Y.; Sakuma, I.; Iwamoto, D.; Kikuchi, Y.; Fukumoto, N.; Nagata, M.

2012-10-01

It is important to know surface damage characteristics of plasma-facing component materials during transient heat and particle loads such as type I ELMs. A magnetized coaxial plasma gun (MCPG) device has been used as transient heat and particle source in ELM simulation experiments. Characteristics of pulsed plasmas produced by the MCPG device play an important role for the plasma material interaction. In this study, ion temperature and flow velocity of pulsed He plasmas were measured by an ion Doppler spectrometer (IDS). The IDS system consists of a light collection system including optical fibers, 1m-spectrometer and a 16 channel photomultiplier tube (PMT) detector. The IDS system measures the width and Doppler shift of HeII (468.58 nm) emission line with the time resolution of 1 μs. The Doppler broadened and shifted spectra were measured with 45 and 135 degree angles with respect to the plasmoid traveling direction. The observed emission line profile was represented by sum of two Gaussian components to determine the temperature and flow velocity. The minor component at around the wavelength of zero-velocity was produced by the stationary plasma. As the results, the ion velocity and temperature were 68 km/s and 19 eV, respectively. Thus, the He ion flow energy is 97 eV. The observed flow velocity agrees with that measured by a time of flight technique.

Beam-plasma instability in charged plasma in the absence of ions

Energy Technology Data Exchange (ETDEWEB)

Dubinov, Alexander E. [National Research Nuclear University “MEPhI,” Kashirskoe Highway, 31, Moscow 115409, Russia and Sarov State Institute of Physics and Technology (SarFTI) of National Research Nuclear University “MEPhI,” Dukhova Str., 6, Sarov, Nizhni Novgorod Region 607186 (Russian Federation); Petrik, Alexey G. [Saratov State Technical University, Politechnicheskaja 77, Saratov 410028 (Russian Federation); Kurkin, Semen A.; Frolov, Nikita S.; Koronovskii, Alexey A.; Hramov, Alexander E., E-mail: hramovae@gmail.com [Saratov State Technical University, Politechnicheskaja 77, Saratov 410028 (Russian Federation); Saratov State University, Astrakhanskaja 83, Saratov 410012 (Russian Federation)

2016-04-15

We report on the possibility of the beam-plasma instability development in the system with electron beam interacting with the single-component hot electron plasma without ions. As considered system, we analyse the interaction of the low-current relativistic electron beam (REB) with squeezed state in the high-current REB formed in the relativistic magnetically insulated two-section vircator drift space. The numerical analysis is provided by means of 3D electromagnetic simulation in CST Particle Studio. We have conducted an extensive study of characteristic regimes of REB dynamics determined by the beam-plasma instability development in the absence of ions. As a result, the dependencies of instability increment and wavelength on the REB current value have been obtained. The considered process brings the new mechanism of controlled microwave amplification and generation to the device with a virtual cathode. This mechanism is similar to the action of the beam-plasma amplifiers and oscillators.

Plasma and Ion Assistance in Physical Vapor Deposition: A Historical Perspective

International Nuclear Information System (INIS)

Anders, Andre

2007-01-01

Deposition of films using plasma or plasma-assist can be traced back surprisingly far, namely to the 18th century for arcs and to the 19th century for sputtering. However, only since the 1960s the coatings community considered other processes than evaporation for large scale commercial use. Ion Plating was perhaps the first important process, introducing vapor ionization and substrate bias to generate a beam of ions arriving on the surface of the growing film. Rather independently, cathodic arc deposition was established as an energetic condensation process, first in the former Soviet Union in the 1970s, and in the 1980s in the Western Hemisphere. About a dozen various ion-based coating technologies evolved in the last decades, all characterized by specific plasma or ion generation processes. Gridded and gridless ion sources were taken from space propulsion and applied to thin film deposition. Modeling and simulation have helped to make plasma and ions effects to be reasonably well understood. Yet--due to the complex, often non-linear and non-equilibrium nature of plasma and surface interactions--there is still a place for the experience plasma 'sourcerer'

Effects of the instability enhanced friction on relative ion densities in a two-ion species low-temperature plasma

Science.gov (United States)

Vukovic, Mirko

2011-10-01

The instability enhanced friction theory of Baalrud & Hegna (Phys. Plasmas 18, 023505 (2011)) predicts that for comparable ion densities the ions nearly reach a common velocity near the sheath edge in a low temperature plasma. The theory was experimentally confirmed by Yip, Hershkowitz, & Severn (Phys. Rev. Letters 104, 225003 (2010)). We will explore the effects of the theory on relative ion densities in a numerical simulation of an Ar/Xe plasma. Results for a 0D plasma model (Lieberman, Lichtenberg, Principles of Plasma Discharges and Materials Processing, 2005) will be presented.

Plasma and Ion Assistance in Physical Vapor Deposition: AHistorical Perspective

Energy Technology Data Exchange (ETDEWEB)

Anders, Andre

2007-02-28

Deposition of films using plasma or plasma-assist can betraced back surprisingly far, namely to the 18th century for arcs and tothe 19th century for sputtering. However, only since the 1960s thecoatings community considered other processes than evaporation for largescale commercial use. Ion Plating was perhaps the first importantprocess, introducing vapor ionization and substrate bias to generate abeam of ions arriving on the surface of the growing film. Ratherindependently, cathodic arc deposition was established as an energeticcondensation process, first in the former Soviet Union in the 1970s, andin the 1980s in the Western Hemisphere. About a dozen various ion-basedcoating technologies evolved in the last decades, all characterized byspecific plasma or ion generation processes. Gridded and gridless ionsources were taken from space propulsion and applied to thin filmdeposition. Modeling and simulation have helped to make plasma and ionseffects to be reasonably well understood. Yet--due to the complex, oftennon-linear and non-equilibrium nature of plasma and surfaceinteractions--there is still a place for the experience plasma"sourcerer."

Computer-controlled system for plasma ion energy auto-analyzer

International Nuclear Information System (INIS)

Wu Xianqiu; Chen Junfang; Jiang Zhenmei; Zhong Qinghua; Xiong Yuying; Wu Kaihua

2003-01-01

A computer-controlled system for plasma ion energy auto-analyzer was technically studied for rapid and online measurement of plasma ion energy distribution. The system intelligently controls all the equipments via a RS-232 port, a printer port and a home-built circuit. The software designed by LabVIEW G language automatically fulfils all of the tasks such as system initializing, adjustment of scanning-voltage, measurement of weak-current, data processing, graphic export, etc. By using the system, a few minutes are taken to acquire the whole ion energy distribution, which rapidly provide important parameters of plasma process techniques based on semiconductor devices and microelectronics

Compressional Pc5 type pulsations in the morningside plasma sheet

Directory of Open Access Journals (Sweden)

A. Vaivads

Full Text Available We study compressional pulsations in Pc5 frequency range observed in the dawn-side at distances of about 10 RE , close to the magnetic equator. We use data obtained during two events of conjunctions between Equator-S and Geotail: 1000–1700 UT on 9 March 1998, and 0200–0600 UT on 25 April 1998. In both events, pulsations are observed after substorm activity. The pulsations are antisymmetric with respect to the equatorial plane (even mode, and move eastward with phase velocity close to plasma velocity. The pulsations tend to be pressure balanced. We also discuss possible generation mechanisms of the pulsations.

Key words. Magnetospheric physics (magnetospheric configuration and dynamics; MHD waves and instabilities; plasma sheet

Compressional Pc5 type pulsations in the morningside plasma sheet

Directory of Open Access Journals (Sweden)

A. Vaivads

2001-03-01

Full Text Available We study compressional pulsations in Pc5 frequency range observed in the dawn-side at distances of about 10 RE , close to the magnetic equator. We use data obtained during two events of conjunctions between Equator-S and Geotail: 1000–1700 UT on 9 March 1998, and 0200–0600 UT on 25 April 1998. In both events, pulsations are observed after substorm activity. The pulsations are antisymmetric with respect to the equatorial plane (even mode, and move eastward with phase velocity close to plasma velocity. The pulsations tend to be pressure balanced. We also discuss possible generation mechanisms of the pulsations.Key words. Magnetospheric physics (magnetospheric configuration and dynamics; MHD waves and instabilities; plasma sheet

Ion enhanced deposition by dual titanium and acetylene plasma immersion ion implantation

Science.gov (United States)

Zeng, Z. M.; Tian, X. B.; Chu, P. K.

2003-01-01

Plasma immersion ion implantation and deposition (PIII-D) offers a non-line-of-sight fabrication method for various types of thin films on steels to improve the surface properties. In this work, titanium films were first deposited on 9Cr18 (AISI440) stainless bearing steel by metal plasma immersion ion implantation and deposition (MePIII-D) using a titanium vacuum arc plasma source. Afterwards, carbon implantation and carbon film deposition were performed by acetylene (C2H2) plasma immersion ion implantation. Multiple-layered structures with superior properties were produced by conducting Ti MePIII-D + C2H2 PIII successively. The composition and structure of the films were investigated employing Auger electron spectroscopy and Raman spectroscopy. It is shown that the mixing for Ti and C atoms is much better when the target bias is higher during Ti MePIII-D. A top diamond-like carbon layer and a titanium oxycarbide layer are formed on the 9Cr18 steel surface. The wear test results indicate that this dual PIII-D method can significantly enhance the wear properties and decrease the surface friction coefficient of 9Cr18 steel.

Ion enhanced deposition by dual titanium and acetylene plasma immersion ion implantation

International Nuclear Information System (INIS)

Zeng, Z.M.; Tian, X.B.; Chu, P.K.

2003-01-01

Plasma immersion ion implantation and deposition (PIII-D) offers a non-line-of-sight fabrication method for various types of thin films on steels to improve the surface properties. In this work, titanium films were first deposited on 9Cr18 (AISI440) stainless bearing steel by metal plasma immersion ion implantation and deposition (MePIII-D) using a titanium vacuum arc plasma source. Afterwards, carbon implantation and carbon film deposition were performed by acetylene (C 2 H 2 ) plasma immersion ion implantation. Multiple-layered structures with superior properties were produced by conducting Ti MePIII-D + C 2 H 2 PIII successively. The composition and structure of the films were investigated employing Auger electron spectroscopy and Raman spectroscopy. It is shown that the mixing for Ti and C atoms is much better when the target bias is higher during Ti MePIII-D. A top diamond-like carbon layer and a titanium oxycarbide layer are formed on the 9Cr18 steel surface. The wear test results indicate that this dual PIII-D method can significantly enhance the wear properties and decrease the surface friction coefficient of 9Cr18 steel

Electron backscatter diffraction applied to lithium sheets prepared by broad ion beam milling.

Science.gov (United States)

Brodusch, Nicolas; Zaghib, Karim; Gauvin, Raynald

2015-01-01

Due to its very low hardness and atomic number, pure lithium cannot be prepared by conventional methods prior to scanning electron microscopy analysis. Here, we report on the characterization of pure lithium metallic sheets used as base electrodes in the lithium-ion battery technology using electron backscatter diffraction (EBSD) and X-ray microanalysis using energy dispersive spectroscopy (EDS) after the sheet surface was polished by broad argon ion milling (IM). No grinding and polishing were necessary to achieve the sufficiently damage free necessary for surface analysis. Based on EDS results the impurities could be characterized and EBSD revealed the microsctructure and microtexture of this material with accuracy. The beam damage and oxidation/hydration resulting from the intensive use of IM and the transfer of the sample into the microscope chamber was estimated to be effect on the surface temperature. However, a cryo-stage should be used if available during milling to guaranty a heating artefact free surface after the milling process. © 2014 Wiley Periodicals, Inc.

Solar wind contribution to the average population of energetic He(+) and He(++) ions in the Earth's magnetosphere

Science.gov (United States)

Kremser, G.; Rasinkangas, R.; Tanskanen, P.; Wilken, B.; Gloeckler, G.

1994-01-01

Measurements with the ion charge-energy-mass spectrometer CHEM on the AMPTE/CCE spacecraft were used to investigate the origin of energetic He(+) and He(++) ions observed in the equatorial plane at 3 less than or equal to L less than or equal to 9. Special emphasis was laid on the dependence of long-term average distributions on magnetic local time (MLT) and the geomagnetic activity index K(sup p). The observations are described in terms of the phase space densities f(sub 1) (for He(+)) and f(sub 2) (for He(++)). They confirm preliminary results from a previous study f(sub 1) is independent of MLT, whereas f(sub 2) is much larger on the nightside than on the dayside. They show, furthermore, that f(sub 1) increases slightly with K(sub p) on intermediate drift shells, but decreases on high drift shells (L greater than or equal to 7). f(sub 2) increases with K(sub p) on all drift shells outside the premidnight sector. Within this sector a decrease is observed on high drift shells. A simple ion tracing code was developed to determine how and from where the ions move into the region of observations. It provides ion trajectories as a function of the ion charge, the magnetic moment and K(sub p). The ion tracing enables a distinction between regions of closed drift orbits (ring current) and open convection trajectories (plasma sheet). It also indicates how the outer part of the observation region is connected to different parts of the more distant plasma sheet. Observations and tracing show that He(++) ions are effectively transported from the plasma sheet on convection trajectories. Their distribution in the observation region corresponds to the distribution of solar wind ions in the plasma sheet. Thus, energetic He(++) ions most likely originate in the solar wind. On the other hand, the plasma sheet is not an important source of energetic He(+) ions. Convection trajectories more likely constitute a sink for He(+) ions, which may diffuse onto them from closed drift orbits

Drift mode in a bounded plasma having two-ion species

International Nuclear Information System (INIS)

Ahmad, Ali; Sajid, M.; Saleem, H.

2008-01-01

The drift wave is investigated in a two-ion species plasma in several different cases. The global drift mode is studied in a plasma bounded in a cylinder having Gaussian density profile corresponding to different poloidal wavenumbers. The frequency of the mode becomes a little larger when it is investigated without including the ion cyclotron wave dynamics. The effect of magnetic shear on the wave propagation along the density gradient is studied in a Cartesian geometry assuming absorbing boundary. It is found that the wave amplitude is reduced when two-ion species are present (with the same concentration) compared to pure electron-ion plasma

Investigation of metal ions in fusion plasmas using emission spectroscopy

International Nuclear Information System (INIS)

Tale, I.

2005-01-01

Full text: The Latvian and Portugal Associations are performing development of advanced plasma - facing system using the liquid metal limiter. The objectives of this project require study of the influence of the liquid metal limiter on the main plasma parameters, including concentration of evaporated metal atoms in plasma. The fusion plasmas are related to the dense hot plasmas. The required average ion temperature according to the ITER project (International Thermonuclear Experimental Reactor) is 8,0 keV (9,3 x 10 7 0 K), the average electron temperature - 8,9 keV (1,04 x 10 8 0 K). Plasma temperature operated in the research tokamak ISSTOK, involved in testing of liquid metal limiter concept is considerably less, being of order of 10 50 K. The ionization degree of metal atoms considerably depends on the plasma ion temperature. Density of metal vapours in plasma can be estimated using the following two spectroscopic methods: The fluorescence of the multiple ionised metal ions in steady state concentration; The charge exchange emission during ionisation of evaporated metal ions. In the first step of development of testing system of metal vapours the equipment and instrumentation for charge exchange spectroscopy of Ga and In has been elaborated taking into account the following features of plasma emission. The Ga emission lines occur on the background high temperature plasma black body emission and stray light. Radial distribution of Ga in plasma in the facing plane of Ga flux is desirable

Drift waves and counter rotating vortices in pair-ion plasmas

Energy Technology Data Exchange (ETDEWEB)

Haque, Q., E-mail: qamar_haque@hotmail.co [Theoretical Plasma Physics Division, PINSTECH P.O. Nilore, Islamabad (Pakistan)

2010-07-19

Linear dispersion relation has been found for drift and acoustic waves in pair-ion-electron plasmas. The stationary solution in the form of counter rotating vortices has been obtained in the presence of equilibrium potential profile. It is noticed that the speed of nonlinear structures is reduced with the increase of electrons concentration in pair-ion plasmas. Linear instability condition has also been found in the presence of shear flow. It is pointed out that the present results can be useful for future pair-ion plasma experiments.

Two-dimensional hydrodynamics of uniform ion plasma in electrostatic field

International Nuclear Information System (INIS)

Mahdieh, M. H.; Gavili, A.

2005-01-01

Two-dimensional hydrodynamics of ion extraction from uniform quasi-neutral plasma, in electrostatic field has been simulated numerically. Experimentally, tunable pulsed lasers produce non-uniform plasma through stepwise photo-excitation and photo-ionization or multi-photo-ionization processes. Poisson's equation was solved simultaneously with the equations of mass, and momentum, assuming the Maxwell-Boltzmann distribution for electrons. In the calculation, the initial density profile at the boundaries has been assumed to be very steep for the ion plasma. In these calculations dynamics of electric potential and the ions density were assessed. The ion extraction time was also estimated from the calculation. The knowledge of spatial distribution of the ions across the cathode is very important for the practical purposes. In this simulation, the spatial distribution of the ion current density across the cathode as well as its temporal distribution was calculated

Plasma synthesis of hard materials with energetic ions

International Nuclear Information System (INIS)

Monteiro, Othon R.

1999-01-01

Recent developments in plasma synthesis of hard materials using metal plasma immersion ion implantation and deposition are described. We have produced and characterized a variety of films including doped and undoped DLC (diamond-like carbon) and metal carbides. By using multiple plasma sources operated either synchronously or asynchronously, different metal plasma species can be either blended or linked so as to form mixed-composition films or multilayer structures, and by control of the depositing ion energy, interfaces can be made sharp or graded and the film morphology and microstructure can be widely tailored. Plasma compositional uniformity is important to produce homogeneous films, and therefore effective mixing of plasma streams produced by the filtered cathodic vacuum arcs is very important. Specific systems described here include amorphic diamond, and TiC. We outline the deposition technique employed in this investigation, and summarize the results of the characterization of the films

Ion collection by probing objects in flowing magnetized plasmas

International Nuclear Information System (INIS)

Kyu-Sun, Chung.

1989-04-01

A new one-dimensional collisionless kinetic model is developed for the flow of ions to probing structures in drifting plasmas. The cross-field flow into the presheath is modelled by accounting consistently for particle exchange between the collection flux tube and the outer plasma. Numerical solutions of the self-consistent plasma/sheath equations are obtained with arbitrary external ion temperature and parallel plasma flow velocity. Results are presented of the spatial dependence of the ion distribution function as well as its moments (density, particle flux, temperature, and power flux). The ion current to the probe is obtained and the ratio of the upstream to downstream currents is found to be well represented by the form R = exp[Ku d ], where K = 1.66 for T i = T e and u d is the drift velocity in units of (T e /m i ) 1/2 . The results agree well with comparable recent fluid calculations but show substantial deviations from other models which ignore particle exchange out of the presheath. No evidence is found of the formation of shocks in the downstream wake, contrary to the implications of some fluid theories. We have also extended the previous kinetic model by generalizing cross-field transport and adding ionization to the source of the Boltzmann equation along the presheath. Ion sheath current density and ratio(R) of upstream to downstream current are obtained as a function of plasma drift velocity, equivalent viscosity, ion temperature, and ionization rate. Constants(K) in the form R = exp[Ku d ] are obtained in terms of viscosity, ion temperature, and ionization rate. The effect of an electrical bias applied to the object on the presheath characteristics is discussed

Ion acceleration in non-equilibrium plasmas driven by fast drifting electron

Energy Technology Data Exchange (ETDEWEB)

Castro, G. [INFN- Laboratori Nazionali del Sud, via S.Sofia 62, 95123 Catania (Italy); Università degli Studi di Catania, Dipartimento di Fisica e Astronomia, V. S.Sofia 64, 95123 Catania (Italy); Di Bartolo, F., E-mail: fdibartolo@unime.it [Università di Messina, V.le F. Stagno D’Alcontres 31, 98166, Messina (Italy); Gambino, N. [INFN- Laboratori Nazionali del Sud, via S.Sofia 62, 95123 Catania (Italy); Università degli Studi di Catania, Dipartimento di Metodologie Fisiche e Chimiche per L’ingegneria, Viale A.Doria 6, 95125 Catania (Italy); Mascali, D. [INFN- Laboratori Nazionali del Sud, via S.Sofia 62, 95123 Catania (Italy); CSFNSM, Viale A. Doria 6, 95125 Catania (Italy); Romano, F.P. [INFN- Laboratori Nazionali del Sud, via S.Sofia 62, 95123 Catania (Italy); CNR-IBAM Via Biblioteca 4, 95124 Catania (Italy); Anzalone, A.; Celona, L.; Gammino, S. [INFN- Laboratori Nazionali del Sud, via S.Sofia 62, 95123 Catania (Italy); Di Giugno, R. [INFN- Laboratori Nazionali del Sud, via S.Sofia 62, 95123 Catania (Italy); Università degli Studi di Catania, Dipartimento di Fisica e Astronomia, V. S.Sofia 64, 95123 Catania (Italy); Lanaia, D. [INFN- Laboratori Nazionali del Sud, via S.Sofia 62, 95123 Catania (Italy); Miracoli, R. [INFN- Laboratori Nazionali del Sud, via S.Sofia 62, 95123 Catania (Italy); Università degli Studi di Catania, Dipartimento di Fisica e Astronomia, V. S.Sofia 64, 95123 Catania (Italy); Serafino, T. [CSFNSM, Viale A. Doria 6, 95125 Catania (Italy); Tudisco, S. [INFN- Laboratori Nazionali del Sud, via S.Sofia 62, 95123 Catania (Italy); CSFNSM, Viale A. Doria 6, 95125 Catania (Italy)

2013-05-01

We hereby present results on ion acceleration mechanisms in non equilibrium plasmas generated by microwaves or high intensity laser pulses. Experiments point out that in magnetized plasmas X–B conversion takes place for under resonance values of the magnetic field, i.e. an electromagnetic mode is converted into an electrostatic wave. The strong self-generated electric field, of the order of 10{sup 7} V/m, causes a E × B drift which accelerates both ions and electrons, as it is evident by localized sputtering in the plasma chamber. These fields are similar (in magnitude) to the ones obtainable in laser generated plasmas at intensity of 10{sup 12} W/cm{sup 2}. In this latter case, we observe that the acceleration mechanism is driven by electrons drifting much faster than plasma bulk, thus generating an extremely strong electric field ∼10{sup 7} V/m. The two experiments confirm that ions acceleration at low energy is possible with table-top devices and following complementary techniques: i.e. by using microwave-driven (producing CW beams) plasmas, or non-equilibrium laser-driven plasmas (producing pulsed beams). Possible applications involve ion implantation, materials surface modifications, ion beam assisted lithography, etc.

Spatial Distribution and Semiannual Variation of Cold-Dense Plasma Sheet

Science.gov (United States)

Bai, Shichen; Shi, Quanqi; Tian, Anmin; Nowada, Motoharu; Degeling, Alexander W.; Zhou, Xu-Zhi; Zong, Qiu-Gang; Rae, I. Jonathan; Fu, Suiyan; Zhang, Hui; Pu, Zuyin; Fazakerly, Andrew N.

2018-01-01

The cold-dense plasma sheet (CDPS) plays an important role in the entry process of the solar wind plasma into the magnetosphere. Investigating the seasonal variation of CDPS occurrences will help us better understand the long-term variation of plasma exchange between the solar wind and magnetosphere, but any seasonal variation of CDPS occurrences has not yet been reported in the literature. In this paper, we investigate the seasonal variation of the occurrence rate of CDPS using Geotail data from 1996 to 2015 and find a semiannual variation of the CDPS occurrences. Given the higher probability of solar wind entry under stronger northward interplanetary magnetic field (IMF) conditions, 20 years of IMF data (1996-2015) are used to investigate the seasonal variation of IMF Bz under northward IMF conditions. We find a semiannual variation of IMF Bz, which is consistent with the Russell-McPherron (R-M) effect. We therefore suggest that the semiannual variation of CDPS may be related to the R-M effect.

Linear and nonlinear ion beam instabilities in a double plasma device

International Nuclear Information System (INIS)

Lee, S.G.; Diebold, D.; Hershkowitz, N.

1994-01-01

Ion beam instabilities in the double plasma device DOLI-1 were found to be quite sensitive to the difference between the source and target chamber plasma potentials when those potentials were within an electron temperature T e /e or so of each other. When the target chamber plasma potential of DOLI-1 was ≤ T e /e more positive than the source chamber plasma potential, a global ion beam-ion beam instability was observed. On the other hand, when the maximum target potential was between approximately 0.5 T e /e and 2.0 T e /e below the source potential, an ion-ion beam instability and a soliton associated with it were observed. This soliton is unique in that it is not launched but rather is self generated by the plasma and beam. When the target potential was less than source potential by more than two or so T e /e, the plasma was quite quiescent, which allowed small amplitude wave packet launched by Langmuir probe to be detected

Thin current sheets observation by MMS during a near-Earth's magnetotail reconnection event

Science.gov (United States)

Nakamura, R.; Varsani, A.; Nakamura, T.; Genestreti, K.; Plaschke, F.; Baumjohann, W.; Nagai, T.; Burch, J.; Cohen, I. J.; Ergun, R.; Fuselier, S. A.; Giles, B. L.; Le Contel, O.; Lindqvist, P. A.; Magnes, W.; Schwartz, S. J.; Strangeway, R. J.; Torbert, R. B.

2017-12-01

During summer 2017, the four spacecraft of the Magnetospheric Multiscale (MMS) mission traversed the nightside magnetotail current sheet at an apogee of 25 RE. They detected a number of flow reversal events suggestive of the passage of the reconnection current sheet. Due to the mission's unprecedented high-time resolution and spatial separation well below the ion scales, structure of thin current sheets is well resolved both with plasma and field measurements. In this study we examine the detailed structure of thin current sheets during a flow reversal event from tailward flow to Earthward flow, when MMS crossed the center of the current sheet . We investigate the changes in the structure of the thin current sheet relative to the X-point based on multi-point analysis. We determine the motion and strength of the current sheet from curlometer calculations comparing these with currents obtained from the particle data. The observed structures of these current sheets are also compared with simulations.

Nonlinear modulation of ion acoustic waves in a magnetized plasma

International Nuclear Information System (INIS)

Bharuthram, R.; Shukla, P.K.

1987-01-01

The quasistatic plasma slow response to coherent ion acoustic waves in a magnetized plasma is considered. A multidimensional cubic nonlinear Schroedinger equation is derived. It is found that the ion acoustic waves remain modulationally stable against oblique perturbations

Laser-induced fluorescence measurements of argon and xenon ion velocities near the sheath boundary in 3 ion species plasmas

Energy Technology Data Exchange (ETDEWEB)

Yip, Chi-Shung; Hershkowitz, Noah [Department of Engineering Physics, University of Wisconsin-Madison, Madison, Wisconsin 53706 (United States); Severn, Greg [Department of Physics, University of San Diego, San Diego, California 92110 (United States); Baalrud, Scott D. [Department of Physics and Astronomy, University of Iowa, Iowa City, Iowa 52242 (United States)

2016-05-15

The Bohm sheath criterion is studied with laser-induced fluorescence in three ion species plasmas using two tunable diode lasers. Krypton is added to a low pressure unmagnetized DC hot filament discharge in a mixture of argon and xenon gas confined by surface multi-dipole magnetic fields. The argon and xenon ion velocity distribution functions are measured at the sheath-presheath boundary near a negatively biased boundary plate. The potential structures of the plasma sheath and presheath are measured by an emissive probe. Results are compared with previous experiments with Ar–Xe plasmas, where the two ion species were observed to reach the sheath edge at nearly the same speed. This speed was the ion sound speed of the system, which is consistent with the generalized Bohm criterion. In such two ion species plasmas, instability enhanced collisional friction was demonstrated [Hershkowitz et al., Phys. Plasmas 18(5), 057102 (2011).] to exist which accounted for the observed results. When three ion species are present, it is demonstrated under most circumstances the ions do not fall out of the plasma at their individual Bohm velocities. It is also shown that under most circumstances the ions do not fall out of the plasma at the system sound speed. These observations are also consistent with the presence of the instabilities.

Electric sheath and presheath in a collisionless, finite ion temperature plasma

International Nuclear Information System (INIS)

Emmert, G.A.; Wieland, R.M.; Mense, A.T.; Davidson, J.N.

1980-01-01

The plasma-sheath equation for a collisionless plasma with arbitrary ion temperature in plane geometry is formulated. Outside the sheath, this equation is approximated by the plasma equation, for which an analytic solution for the electrostatic potential is obtained. In addition, the ion distribution function, the wall potential, and the ion energy and particle flux into the sheath are explicitly calculated. The plasma-sheath equation is also solved numerically with no approximation of the Debye length. The numerical results compare well with the analytical results when the Debye length is small

Ion acceleration by laser hole-boring into plasmas

International Nuclear Information System (INIS)

Pogorelsky, I. V.; Dover, N. P.; Babzien, M.; Bell, A. R.; Dangor, A. E.; Horbury, T.; Palmer, C. A. J.; Polyanskiy, M.; Schreiber, J.; Schwartz, S.; Shkolnikov, P.; Yakimenko, V.; Najmudin, Z.

2012-01-01

By experiment and simulations, we study the interaction of an intense CO 2 laser pulse with slightly overcritical plasmas of fully ionized helium gas. Transverse optical probing is used to show a recession of the front plasma surface with an initial velocity >10 6 m/s driven by hole-boring by the laser pulse and the resulting radiation pressure driven electrostatic shocks. The collisionless shock propagates through the plasma, dissipates into an ion-acoustic solitary wave, and eventually becomes collisional as it slows further. These observations are supported by PIC simulations which prove the conclusion that monoenergetic protons observed in our earlier reported experiment with a hydrogen jet result from ion trapping and reflection from a shock wave driven through the plasma.

Energy loss of heavy ion beams in plasma

Energy Technology Data Exchange (ETDEWEB)

Okada, T; Hotta, T [Tokyo Univ. of Agriculture and Technology, Koganei (Japan). Faculty of Technology

1997-12-31

The energy loss of heavy-ion beams (HIB) is studied by means of Vlasov theory and Particle-in-Cell (PIC) simulations in a plasma. The interaction of HIB with a plasma is of central importance for inertial confinement fusion (ICF). A number of studies on the HIB interaction with target plasma have been published. It is important for heavy-ion stopping that the effects of the non-linear interaction of HIB within the Vlasov theory are included. Reported are results of a numerical study of nonlinear effects to the stopping power for HIB in plasma. It is shown that the PIC simulations of collective effects of the stopping power are in a good agreement with the Vlasov theory. (author). 2 tabs., 1 fig., 5 refs.

Ion acceleration in multi-species cathodic plasma jet

Science.gov (United States)

Krasov, V. I.; Paperny, V. L.

2016-05-01

A general expression for ion-ion coupling in a multi-species plasma jet was obtained. The expression is valid for any value of the inter-species velocity. This expression has enabled us to review a hydrodynamic problem of expanding the cathodic plasma microjet with two ion species within the respective charge states Z1 = +1 and Z2 = +2 into a vacuum. We were able to illustrate that in scenario when the initial (i.e., acquired during a process of emission from cathode's surface) difference for ion's species velocity exceeds a threshold value, the difference remains noticeable (roughly about 10% of the average jet's velocity) at a distance of a few centimeters from the emission center. At this point, it can be measured experimentally.

Properties of plasma sheath with ion temperature in magnetic fusion devices

International Nuclear Information System (INIS)

Liu Jinyuan; Wang Feng; Sun Jizhong

2011-01-01

The plasma sheath properties in a strong magnetic field are investigated in this work using a steady state two-fluid model. The motion of ions is affected heavily by the strong magnetic field in fusion devices; meanwhile, the effect of ion temperature cannot be neglected for the plasma in such devices. A criterion for the plasma sheath in a strong magnetic field, which differs from the well-known Bohm criterion for low temperature plasma sheath, is established theoretically with a fluid model. The fluid model is then solved numerically to obtain detailed sheath information under different ion temperatures, plasma densities, and magnetic field strengths.

Ion Acoustic Waves in the Presence of Electron Plasma Waves

DEFF Research Database (Denmark)

Michelsen, Poul; Pécseli, Hans; Juul Rasmussen, Jens

1977-01-01

Long-wavelength ion acoustic waves in the presence of propagating short-wavelength electron plasma waves are examined. The influence of the high frequency oscillations is to decrease the phase velocity and the damping distance of the ion wave.......Long-wavelength ion acoustic waves in the presence of propagating short-wavelength electron plasma waves are examined. The influence of the high frequency oscillations is to decrease the phase velocity and the damping distance of the ion wave....

The Origin of the Near-Earth Plasma Population During a Substorm on November 24, 1996

Science.gov (United States)

Ashour-Abdalla, M.; El-Alaoui, M.; Peroomian, V.; Walker, R. J.; Raeder, J.; Frank, L. A.; Paterson, W. R.

1999-01-01

We investigate the origins and the transport of ions observed in the near-Earth plasma sheet during the growth and expansion phases of a magnetospheric substorm that occurred on November 24, 1996. Ions observed at Geotail were traced backward in time in time-dependent magnetic and electric fields to determine their origins and the acceleration mechanisms responsible for their energization. Results from this investigation indicate that, during the growth phase of the substorm, most of the ions reaching Geotail had origins in the low latitude boundary layer (LLBL) and had already entered the magnetosphere when the growth phase began. Late in the growth phase and in the expansion phase a higher proportion of the ions reaching Geotail had their origin in the plasma mantle. Indeed, during the expansion phase more than 90% of the ions seen by Geotail were from the mantle. The ions were accelerated enroute to the spacecraft; however, most of the ions' energy gain was achieved by non-adiabatic acceleration while crossing the equatorial current sheet just prior to their detection by Geotail. In general, the plasma mantle from both southern and northern hemispheres supplied non-adiabatic ions to Geotail, whereas the LLBL supplied mostly adiabatic ions to the distributions measured by the spacecraft. Distribution functions computed at the ion sources indicate that ionospheric ions reaching Geotail during the expansion phase were significantly heated. Plasma mantle source distributions indicated the presence of a high-latitude reconnection region that allowed ion entry into the magnetosphere when the IMF was northward. These ions reached Geotail during the expansion phase. Ions from the traditional plasma mantle had access to the spacecraft throughout the substorm.

Study on laser plasma as an ion source for the controlled fasion with heavy ions

International Nuclear Information System (INIS)

Barabash, L.Z.; Bykovskij, Yu.A.; Golubev, A.A.; Kozyrev, Yu.P.; Krechet, K.I.; Lapitskij, Yu.Ya.; Sharkov, B.Yu.

1981-01-01

The results of experimental investigations of Pb 208 multiply- charged lead ions, obtained in the course of CO 2 laser radiation effect on a solid target are presented. The experimental installation, the basic units of which are CO 2 - laser with transverse discharge, ion source chamber, time- of-flight space, 9-channel electrostatic mirror type mass-analyser with a detection unit, is described. Physical characteristics of a freely spreading laser plasma, ion distribution over energies, velocities and Z charges from Z=+1 to Z=+10 are investigated. Absolute values of ion number of each charge property as well as absolute values of currents are obtained, the laser plasma temperature is estimated. The analysis of time distribution of ion quantity permits to point out the following regularities: with Z increase the ion current duration decreases according to the Δt approximately Z -1 law, with Z increase, the moment of the ion pulse beginning approaches to the moment of target irradiation which testifies that multiply-charged ions have high velocities and energies. The velocity distribution analysis permits to obtain ion velocity dependence in the field of maximum distribution on charge properties. The results presented are obtained at the temperature of hot unspreaded plasma about 60 eV. The data obtained are a basis for development of a real laser forinjector for the problems of the controlled fusion with heavy ions [ru

Numerical simulations of plasma equilibrium in a one-dimensional current sheet with a nonzero normal magnetic field component

International Nuclear Information System (INIS)

Mingalev, O. V.; Mingalev, I. V.; Malova, Kh. V.; Zelenyi, L. M.

2007-01-01

The force balance in a thin collisionless current sheet in the Earth's magnetotail with a given constant magnetic field component B z across the sheet is numerically studied for the first time in a self-consistent formulation of the problem. The current sheet is produced by oppositely directed plasma flows propagating from the periphery of the sheet toward the neutral plane. A substantially improved version of a macroparticle numerical model is used that makes it possible to simulate on the order of 10 7 macroparticles even with a personal computer and to calculate equilibrium configurations with a sufficiently low discrete noise level in the first-and second-order moments of the distribution function, which determine the stress tensor elements. Quasisteady configurations were calculated numerically for several sets of plasma parameters in some parts of the magnetotail. The force balance in the sheet was checked by calculating the longitudinal and transverse pressures as well as the elements of the full stress tensor. The stress tensor in the current sheet is found to be nondiagonal and to differ appreciably from the gyrotropic stress tensor in the Chew-Goldberger-Low model, although the Chew-Goldberger-Low theory and numerical calculations yield close results for large distances from the region of reversed magnetic field

Images of Complex Interactions of an Intense Ion Beam with Plasma Electrons

International Nuclear Information System (INIS)

Kaganovich, Igor D.; Startsev, Edward; Davidson, Ronald C.

2004-01-01

Ion beam propagation in a background plasma is an important scientific issue for many practical applications. The process of ion beam charge and current neutralization is complex because plasma electrons move in strong electric and magnetic fields of the beam. Computer simulation images of plasma interaction with an intense ion beam pulse are presented

Nonlinear propagation of ion-acoustic solitary waves in relativistic ion-beam plasma with negative ions

International Nuclear Information System (INIS)

Singh, Kh.I.; Das, G.C.

1993-01-01

Soliton propagations are studied in a relativistic multicomponent ion-beam plasma through the derivation of Korteweg-deVries (K-dV) and modified K-dV (mK-dV) equations. A generalization of the mK-dV equation involving higher order nonlinearities gives a transitive link between the K-dV and mK-dV equations for isothermal plasma, and the validity of this generalized equation throughout the whole range of negative ion concentrations is investigated through the derivation of Sagdeev potential. Parallel discussion of various K-dV solitons enlightening the experimental implications is also made. (author). 22 refs

Cluster ion formation during sputtering processes: a complementary investigation by ToF-SIMS and plasma ion mass spectrometry

International Nuclear Information System (INIS)

Welzel, T; Ellmer, K; Mändl, S

2014-01-01

Plasma ion mass spectrometry using a plasma process monitor (PPM) and time-of-flight secondary ion mass spectrometry (ToF-SIMS) have been complementarily employed to investigate the sputtering and ion formation processes of Al-doped zinc oxide. By comparing the mass spectra, insights on ion formation and relative cross-sections have been obtained: positive ions as measured during magnetron sputtering by PPM are originating from the plasma while those in SIMS start at the surface leading to large differences in the mass spectra. In contrast, negative ions originating at the surface will be accelerated through the plasma sheath. They arrive at the PPM after traversing the plasma nearly collisionless as seen from the rather similar spectra. Hence, it is possible to combine the high mass resolution of ToF-SIMS to obtain insight for separating cluster ions, e.g. Zn x and ZnO y , and the energy resolution of PPM to find fragmentation patterns for negative ions. While the ion formation processes during both experiments can be assumed to be similar, differences may arise due to the lower volume probed by SIMS. In the latter case, there is a chance of small target inhomogeneities being able to be enhanced and lower surface temperatures leading to less outgassing and, thus, retention of volatile compounds. (paper)

Field reversing magnetotail current sheets: earth, Venus, and Comet Giacobini-Zinner

International Nuclear Information System (INIS)

McComas, D.J.

1986-09-01

This dissertation examines the field reversing magnetotail current sheets at the earth, Venus, and Comet Giacobini-Zinner. In the near earth study a new analysis technique is developed to calculate the detailed current density distributions within the cross tail current sheet for the first time. This technique removes the effects of a variable sheet velocity by inverting intersatellite timings between the co-orbiting satellites ISEE-1 and -2. Case studies of three relatively geomagnetically quiet crossings are made; sheet thicknesses and peak current densities are ∼1-5 x 10 4 km and ∼5-50 nA/m 2 . Current density distributions reveal a high density central region, lower density shoulders, and considerable fine structure throughout. In the Venus study another new analysis technique is developed to reconstruct the average tail configuration from a correlation between field magnitude and draping angle in a large statistical data set. In the comet study, high resolution magnetic field and plasma electron data from the ICE traversal of Giacobini-Zinner are combined for the first time to determine the tail/current sheet geometry and calculate certain important but unmeasured local ion and upstream properties. Pressure balance across the tail gives ion temperatures and betas of ∼1.2 x 10 5 K and ∼40 in the center of the current sheet to ∼1 x 10 6 K and ∼3 in the outer lobes. Axial stress balance shows that the velocity shear upstream near the nucleus is >6 (∼1 at ICE), and that a region of strongly enhanced mass loading (ion source rate ∼24 times that upstream from lobes) exists upstream from the current sheet. The integrated downtail mass flux is ∼2.6 x 10 26 H 2 O+/sec, which is only ∼1% of the independently determined total cometary efflux. 79 refs., 37 figs

Plasma potentials and performance of the advanced electron cyclotron resonance ion source

International Nuclear Information System (INIS)

Xie, Z.Q.; Lyneis, C.M.

1994-01-01

The mean plasma potential was measured on the LBL advanced electron cyclotron resonance (AECR) ion source for a variety of conditions. The mean potentials for plasmas of oxygen, argon, and argon mixed with oxygen in the AECR were determined. These plasma potentials are positive with respect to the plasma chamber wall and are on the order of tens of volts. Electrons injected into the plasma by an electron gun or from an aluminum oxide wall coating with a very high secondary electron emission reduce the plasma potential as does gas mixing. A lower plasma potential in the AECR source coincides with enhanced production of high charged state ions indicating longer ion confinement times. The effect of the extra electrons from external injection or wall coatings is to lower the average plasma potential and to increase the n e τ i of the ECR plasma. With sufficient extra electrons, the need for gas mixing can be eliminated or reduced to a lower level, so the source can operate at lower neutral pressures. A reduction of the neutral pressure decreases charge exchange between ions and neutrals and enhances the production of high charge state ions. An aluminum oxide coating results in the lowest plasma potential among the three methods discussed and the best source performance

Investigation of Dusts Effect and Negative Ion in DC Plasmas by Electric Probes

Science.gov (United States)

Oh, Hye Taek; Kang, Inje; Bae, Min-Keun; Park, Insun; Lee, Seunghwa; Jeong, Seojin; Chung, Kyu-Sun

2017-10-01

Dust is typically negatively charged by electron attachment whose thermal velocities are fast compared to that of the heavier ions. The negatively charged particles can play a role of negative ions which affect the quasi-neutrality of background plasma. To investigate effect of metal dusts and negative ion on plasma and materials, metal dusts are injected into background Ar plasma which is generated by tungsten filament using dust dispenser on Cubical Plasma Device (CPD). The CPD has following conditions: size =24x24x24cm3, plasma source =DC filament plasma (ne 1x10x1010, Te 2eV), background gas =Ar, dusts =tungsten powder (diameter 1.89micron). The dust dispenser is developed to quantitate of metal dust by ultrasonic transducer. Electronegative plasmas are generated by adding O2 + Ar plasma to compare negative ion and dust effect. A few grams of micron-sized dusts are placed in the dust dispenser which is located at the upper side of the Cubical Plasma Device. The falling particles by dust dispenser are mainly charged up by the collection of the background plasma. The change in parameters due to negative ion production are characterized by measuring the floating and plasma potential, electron temperature and negative ion density using electric probes.

Excitation of electrostatic ion cyclotron wave in electron beam plasma system

International Nuclear Information System (INIS)

Fukumura, Takashi; Takamoto, Teruo

1984-01-01

The electrostatic ion cyclotron waves excited in an electron beam plasma system was investigated. The excitation condition of the waves was calculated by using Harris type dispersion relation under some assumption, and its comparison with the experimental result was made. Beam plasma discharge is a kind of RF discharge, and it is caused by the waves generated by the interaction of electron beam with plasma. It was shown that electrostatic ion cyclotron waves seemed to be the most probable as excited waves. But the excitation mechanism of these waves has not been concretely investigated. In this study, the excitation condition of electrostatic ion cyclotron waves was calculated as described above. The experimental apparatus and the results of potential, electric field and ion saturation current in beam plasma, electron drift motion in azimuthal direction and the waves excited in beam plasma are reported. The frequency of oscillation observed in beam plasma corresponds to the harmonics or subharmonics of ion cyclotron frequency. The calculation of Harris type dispersion relation, the numerical calculation and the comparison of the experimental result with the calculated result are described. (Kako, I.)

Cluster view of the plasma sheet boundary layer and bursty bulk flow connection

Directory of Open Access Journals (Sweden)

O. W. Lennartsson

2009-04-01

Full Text Available The high-latitude boundaries of the plasma sheet (PSBL are dynamic latitude zones of recurring and transient (minutes to tens of minutes earthward and magnetic field-aligned bursts of plasma, each being more or less confined in longitude as well, whose ionic component is dominated by protons with flux, energies and density that are consistent with a central plasma sheet (CPS source at varying distance (varying rates of energy time dispersion, sometimes as close as the ~19 RE Cluster apogees, or closer still. The arguably most plausible source consists of so called "bursty bulk flows" (BBFs, i.e. proton bulk flow events with large, positive and bursty GSE vx. Known mainly from CPS observations made at GSE x>−30 RE, the BBF type events probably take place much further downtail as well. What makes the BBFs an especially plausible source are (1 their earthward bulk flow, which helps explain the lack of distinctive latitudinal PSBL energy dispersion, and (2 their association with a transient strong increase of the local tail Bz component ("local dipolarization". The enhanced Bz provides intermittent access to higher latitudes for the CPS plasma, resulting in local density reductions in the tail midplane, as illustrated here by proton data from the Cluster CIS CODIF instruments. Another sign of kinship between the PSBL bursts and the BBFs is their similar spatial fine structure. The PSBL bursts have prominent filaments aligned along the magnetic field with transverse flux gradients that are often characterized by local ~10 keV proton gyroradii scale size (or even smaller, as evidenced by Cluster measurements. The same kind of fine structure is also found during Cluster near-apogee traversals of the tail midplane, as illustrated here and implied by recently published statistics on BBFs obtained with Cluster multipoint observations at varying satellite separations. Altogether, the Cluster observations described here mesh rather well with theories

Study on the effects of ion motion on laser-induced plasma wakes

International Nuclear Information System (INIS)

Zhou Suyun; Yu Wei; Yuan Xiao; Xu Han; Cao, L. H.; Cai, H. B.; Zhou, C. T.

2012-01-01

A 2D analytical model is presented for the generation of plasma wakes (or bubbles) with an ultra-intense laser pulse by taking into account the response of plasma ions. It is shown that the effect of ion motion becomes significant at the laser intensity exceeding 10 21 W/cm 2 and plasma background density below 10 19 cm −3 . In this regime, ion motion tends to suppress the electrostatic field induced by charge separation and makes the electron acceleration less effective. As a result, the assumption of immobile ions overestimates the efficiency of laser wake-field acceleration of electrons. Based on the analytical model, the dynamics of plasma ions in laser-induced wake field is investigated. It is found that only one bubble appears as the plasmas background density exceeds the resonant density and the deposited laser energy is concentrated into the bubble, resulting in the generation of an ion bunch with extremely high energy density.

Ion-cyclotron modes in weakly relatavistic plasmas

International Nuclear Information System (INIS)

Venugopal, C.; Kurian, P.J.; Renuka, G.

1994-01-01

We derive a dispersion relation for the perpendicular propagation of ion-cyclotron waves around the ion gyrofrequency Ω + in a weakly relativistic, anisotropic Maxwellian plasma. Using an ordering parameter ε, we separated out two dispersion relations, one of which is independent of the relativistic terms, while the other depends sensitively on them. The solutions of the former dispersion relation yield two modes: a low-frequency (LF) mode with a frequency ω + and a high-frequency (HF) mode with ω > Ω + . The plasma is stable to the propagation of these modes. The latter dispersion relation yields a new LF mode in addition to the modes supported by the non-relativistic dispersion relation. The two LF modes can coalesce to make the plasma unstable. These results are also verified numerically using a standard root solver. (author)

Ion Acceleration in Plasmas with Alfven Waves

International Nuclear Information System (INIS)

Kolesnychenko, O.Ya.; Lutsenko, V.V.; White, R.B.

2005-01-01

Effects of elliptically polarized Alfven waves on thermal ions are investigated. Both regular oscillations and stochastic motion of the particles are observed. It is found that during regular oscillations the energy of the thermal ions can reach magnitudes well exceeding the plasma temperature, the effect being largest in low-beta plasmas (beta is the ratio of the plasma pressure to the magnetic field pressure). Conditions of a low stochasticity threshold are obtained. It is shown that stochasticity can arise even for waves propagating along the magnetic field provided that the frequency spectrum is non-monochromatic. The analysis carried out is based on equations derived by using a Lagrangian formalism. A code solving these equations is developed. Steady-state perturbations and perturbations with the amplitude slowly varying in time are considered

Large-amplitude ion-acoustic double layers in a plasma with warm ions

International Nuclear Information System (INIS)

Roychoudury, R.K.; Bhattacharyya, S.; Varshni, Y.P.

1990-01-01

The conditions for the existence of an ion-acoustic double layer in a plasma with warm ions and two distinct groups of hot electrons have been studied using the Sagdeev potential method. A comparison is made with the published results of Bharuthram and Shukla for cold ions and a two temperature electron population. Numerical studies have been made to find out the effect of a finite ion temperature on the Mach number of the double layers

The hot plasma environment at jupiter: ulysses results.

Science.gov (United States)

Lanzerotti, L J; Armstrong, T P; Gold, R E; Anderson, K A; Krimigis, S M; Lin, R P; Pick, M; Roelof, E C; Sarris, E T; Simnett, G M; Maclennan, C G; Choo, H T; Tappin, S J

1992-09-11

Measurements of the hot plasma environment during the Ulysses flyby of Jupiter have revealed several new discoveries related to this large rotating astrophysical system. The Jovian magnetosphere was found by Ulysses to be very extended, with the day-side magnetopause located at approximately 105 Jupiter radii. The heavy ion (sulfur, oxygen, and sodium) population in the day-side magnetosphere increased sharply at approximately 86 Jupiter radii. This is somewhat more extended than the "inner" magnetosphere boundary region identified by the Voyager hot plasma measurements. In the day-side magnetosphere, the ion fluxes have the anisotropy direction expected for corotation with the planet, with the magnitude of the anisotropy increasing when the spacecraft becomes more immersed in the hot plasma sheet. The relative abundances of sulfur, oxygen, and sodium to helium decreased somewhat with decreasing radial distance from the planet on the day-side, which suggests that the abundances of the Jupiter-derived species are dependent on latitude. In the dusk-side, high-latitude region, intense fluxes of counter-streaming ions and electrons were discovered from the edge of the plasma sheet to the dusk-side magnetopause. These beams of electrons and ions were found to be very tightly aligned with the magnetic field and to be superimposed on a time- and space-variable isotropic hot plasma background. The currents carried by the measured hot plasma particles are typically approximately 1.6 x 10(-4) microamperes per square meter or approximately 8 x 10(5) amperes per squared Jupiter radius throughout the high-latitude magnetosphere volume. It is likely that the intense particle beams discovered at high Jovian latitudes produce auroras in the polar caps of the planet.

Hyperpolarizabilities of one and two electron ions under strongly coupled plasma

International Nuclear Information System (INIS)

Sen, Subhrangsu; Mandal, Puspajit; Kumar Mukherjee, Prasanta; Fricke, Burkhard

2013-01-01

Systematic investigations on the hyperpolarizabilities of hydrogen and helium like ions up to nuclear charge Z = 7 under strongly coupled plasma environment have been performed. Variation perturbation theory has been adopted to evaluate such properties for the one and two electron systems. For the two electron systems coupled Hartree-Fock theory, which takes care of partial electron correlation effects, has been utilised. Ion sphere model of the strongly coupled plasma, valid for ionic systems only, has been adopted for estimating the effect of plasma environment on the hyperpolarizability. The calculated free ion hyperpolarizability for all the systems is in good agreement with the existing data. Under confinement hyperpolarizabilities of one and two electron ions show interesting trend with respect to plasma coupling strength.

Ion cyclotron instability saturation and turbulent plasma heating in the presence of ions moving across the magnetic field

International Nuclear Information System (INIS)

Mikhajlenko, V.S.; Stepanov, K.N.

1981-01-01

Ion cyclotron instability saturation is considered in terms of the turbulence theory when there is a beam of heavy ions with large thermal longitudinal velocity spread. The instability excitation is due to a cyclotron interaction with ions of the beam under the anomalous Doppler effect. The instability is shown to be saturated due to an induced plasma ion scattering of ion cyclotron waves when the beam ion charge number Zsub(b) is approximately 1. Decay processes, wave scattering by virtual wave polarization clouds and resonance broadening due to random walk of plasma ions in turbulent instability fields appear to be unimportant. For Zsub(b)>>1 the induced wave scattering by the beam ions is the main process determining the nonlinear stage of the instability. Estimates are given for the oscillation energy density in the instability saturation state and for the turbulent heating rate of plasma and beam ions [ru

Pressure changes in the plasma sheet during substorm injections

International Nuclear Information System (INIS)

Kistler, L.M.; Moebuis, E.; Baumjohann, W.; Paschmann, G.; Hamilton, D.C.

1992-01-01

The authors have determined the particle pressure and total pressure as a function of radial distance in the plasma sheet for periods before and after the onset of substorm-associated ion enhancements over the radial range 7-19 R E . They have chosen events occurring during times of increasing magnetospheric activity, as determined by an increasing AE index, in which a sudden increase, or injection, of energetic particle flux is observed. During these events the particle energy of maximum contribution to the pressure increases from about 12 to about 27 keV. In addition, the particle pressure increases, and the magnetic pressure decreases, with the total pressure only changing slightly. For radial distances of less than 10 R E the total pressure tends to increase with the injection, while outside 10 R E it tends to decrease or remain the same. Because the fraction of the pressure due to particles has increased and higher energies are contributing to the pressure, a radial gradient is evident in the postinjection, but not preinjection, flux measurements. These observations show that the simulations appearance of energetic particles and changes in the magnetic field results naturally from pressure balance and does not necessarily indicate that the local changing field is accelerating the particles. The changes in the total pressure outside 10 R E are consistent with previous measurements of pressure changes at substorm onset and can be understood in terms of the unloading of energy in the magnetotail and the resulting change in the magnetic field configuration

Dynamic plasma screening effects on semiclassical inelastic electron endash ion collisions in dense plasmas

International Nuclear Information System (INIS)

Jung, Y.

1997-01-01

In dense plasmas, dynamic plasma screening effects are investigated on 1s→2p dipole transition probabilities for electron-impact excitation of hydrogenic ions. The electron endash ion interaction potential is considered by introduction of the plasma dielectric function. A semiclassical straight-line trajectory method is applied to the path of the projectile electron in order to visualize the semiclassical transition probability as a function of the impact parameter, projectile energy, and plasma parameters. The transition probability including the dynamic plasma screening effect is always greater than that including the static plasma screening effect. When the projectile velocity is smaller than the electron thermal velocity, the dynamic polarization screening effect becomes the static plasma screening effect. When the projectile velocity is greater than the electron thermal velocity, then the interaction potential is almost unshielded. The difference between the dynamic and static plasma screening effects is more significant for low-energy projectiles. It is also found that the static plasma screening formula obtained by the Debye endash Hueckel model overestimates the plasma screening effects on the atomic excitation processes in dense plasmas. copyright 1997 American Institute of Physics

Prediction of plasma properties in mercury ion thrusters

Science.gov (United States)

Longhurst, G. R.

1978-01-01

A simplified theoretical model was developed which obtains to first order the plasma properties in the discharge chamber of a mercury ion thruster from basic thruster design and controllable operating parameters. The basic operation and design of ion thrusters is discussed, and the important processes which influence the plasma properties are described in terms of the design and control parameters. The conservation for mass, charge and energy were applied to the ion production region, which was defined as the region of the discharge chamber having as its outer boundary the surface of revolution of the innermost field line to intersect the anode. Mass conservation and the equations describing the various processes involved with mass addition and removal from the ion production region are satisfied by a Maxwellian electron density spatial distribution in that region.

Ion acceleration in multi-species cathodic plasma jet

International Nuclear Information System (INIS)

Krasov, V. I.; Paperny, V. L.

2016-01-01

A general expression for ion-ion coupling in a multi-species plasma jet was obtained. The expression is valid for any value of the inter-species velocity. This expression has enabled us to review a hydrodynamic problem of expanding the cathodic plasma microjet with two ion species within the respective charge states Z 1  = +1 and Z 2  = +2 into a vacuum. We were able to illustrate that in scenario when the initial (i.e., acquired during a process of emission from cathode's surface) difference for ion's species velocity exceeds a threshold value, the difference remains noticeable (roughly about 10% of the average jet's velocity) at a distance of a few centimeters from the emission center. At this point, it can be measured experimentally.