Concentration Of Heavy Ions Research Articles

Computing magnetospheric mass density from field line resonances in a realistic magnetic field geometry

Ultra‐low‐frequency (ULF) field line resonances can be used to infer the mass density along magnetospheric magnetic field lines. By specifying how mass density is distributed along the magnetic field (usually a power law as a function of distance from the Earth) and a dipole magnetic field geometry, the MHD standing wave equation can be analytically solved and mass density inferred from observed field line eigenfrequencies. However, the geometry of the Earth's magnetic field can deviate significantly from a dipole, even at relatively low L shells and on the dayside magnetosphere. This study investigates the importance of including a realistic magnetic field geometry when computing plasma mass density from observed field line eigenfrequencies. A generalized version of the toroidal mode MHD standing wave equation is solved using the Tsyganenko (2002a, 2002b) empirical magnetic field model (T01). The results are compared to those found using a dipole. We find that assuming a dipole magnetic field geometry results in an overestimation of mass density. The overestimation is larger for more disturbed levels of geomagnetic activity. Our results have important implications for the inference of heavy ions in the magnetosphere. Namely, an increase in heavy ion concentration as a result of enhanced geomagnetic activity will be exaggerated unless the proper magnetic field geometry is taken into account when calculating mass density from field line eigenfrequencies.

Electronic Defect and Contamination Monitoring in Si Wafers Using Spectrally Integrated Photocarrier Radiometry

The ability of spectrally integrated room-temperature photocarrier radiometry to image electronic defects and contamination in silicon wafers is presented. Amplitude and phase imaging contrast is a result of signal sensitivity to local variations in the recombination lifetime of photoexcited carriers. Experimental frequency scans are fitted to carrier density-wave theory to simultaneously obtain the recombination lifetime, diffusivity, and surface recombination velocities (front and back). Lifetime measurements are combined with lateral surface scans to produce quantitative lifetime imaging. Contaminated boron-doped silicon wafers with iron concentration on a baseline of have been successfully imaged and exhibit a much higher spatial resolution than surface photovoltage images. Recombination lifetime measurements before and after photodissociation of FeB pairs have been utilized for quantitative determination of iron concentration; however, lifetime accuracy limitations due to photodissociation by the excitation laser under medium-to-high optical injection levels required for photocarrier radiometric measurements compromise the accuracy of heavy ion (Fe) concentration measurements.

A plasmaspheric mass density model and constraints on its heavy ion concentration

The first empirical model of the equatorial mass density of the plasmasphere is constructed using ground‐based ULF wave diagnostics. Plasmaspheric mass density between L = 1.7 and L = 3.2 has been determined using over 5200 hours of data from pairs of stations in the MEASURE array of ground magnetometers. The least squares fit to the data as a function of L shows that mass density falls logarithmically with L. Average ion mass as a function of L is also estimated by combining the mass density model with plasmaspheric electron density profiles determined from the IMAGE Radio Plasma Imager (RPI). Additionally, we use the RPI electron density database to examine how the average ion mass changes under different levels of geomagnetic activity. We find that average ion mass is greatest under the most disturbed conditions. This result indicates that heavy ion concentrations (percent by number) are enhanced during large geomagnetic disturbances. We also find that the average ion mass increases with increasing L (below L = 3.2), indicating the presence of a heavy ion torus during disturbed times. Heavy ions must play an important role in storm‐time plasmaspheric dynamics. The average ion mass is also used to constrain the concentrations of He+ and O+. Estimates of the He+ concentration determined this way may be useful for interpreting IMAGE Extreme Ultraviolet Imager (EUV) images.

Heavy-metal ion sensors using chitosan-capped gold nanoparticles

We report a novel strategy for using gold nanoparticles capped with chitosan for sensing ions of heavy metals. Acidic anions (glutamate ions in our case) are expected to cap the nanoparticle surfaces similar to conventional methods of stabilization of gold nanoparticles by citrate ions. The polycationic nature of chitosan enables attachment of the polymer to the negatively charged gold nanoparticle surfaces through electrostatic interactions. Use of chitosan serves dual purpose of providing sufficient steric hindrance ensuring stability of the colloid and also to functionalize the nanoparticles for use as sensors. The well-documented chelating properties of chitosan and the sensitivity of the optical properties of gold nanoparticles to agglomeration have been employed to detect low concentrations of heavy metals ions (Zn2+ and Cu2+) in water. A comparison of the optical absorption spectra of the colloidal suspension before and after exposure to metal ions is a good indicator of the concentration of the heavy metal ions.

Diurnal variation in the concentration of air ions of different mobility classes in a rural area

Analyzed data consist of 8900 hourly average mobility distributions measured in the mobility range of 0.00041–3.2 cm2 V−1 s−1 (diameter range 0.36–79 nm) at Tahkuse Observatory, Estonia, in 1993–1994. The average diurnal variation in the concentration of cluster ions is typical for continental stations: the maximum in the early morning hours and the minimum in the afternoon. This is explained by variations in radon concentration. The diurnal variation for big cluster ions (0.5–1.3 cm2 V−1 s−1) differs from that for small cluster ions (1.3–3.14 cm2 V−1 s−1). The size distribution of intermediate and light large ions in the range of 1.6–22 nm is strongly affected by nucleation bursts of nanometer particles. On the burst days, the maximum concentration of intermediate ions (1.6–7.4 nm) is about the noontime and that of light large ions (7.4–22 nm) about 2 hours later. The concentration of heavy large ions (charged Aitken particles of diameters of 22–79 nm) is enhanced in the afternoon and this is explained by the bursts of nanometer particles and the subsequent growth of particles by condensation and coagulation. If the burst days are excluded, then in the warm season the concentration of Aitken particles increases during night. In the cold season, the diurnal variation is different and all the classes of aerosol ions (2.1–79 nm) show similar variation with the minimum at 0600 LT and the maximum in the afternoon; exceptions are the rare nucleation burst days.

Conditions for the Observation of Two Ion-Acoustic Waves viaThomson Scattering

Observation of two ion-acoustic waves via Thomson scattering canprovide precise measurements of plasma parameters. The conditionsfor the observation of two ion-acoustic modes in a two-ion plasmaare discussed. The ratio of electron temperature Te to iontemperature Ti is the critical parameter for the presence oftwo ion-acoustic modes, which should be in the range of4/ZL≲{Te/Ti}≲2AH/ZHAL, where ZL,H arethe charge states of light and heavy ions, and AL,H are theatomic numbers of light and heavy ions, respectively. As thetemperature ratio varies in this range, the concentration ofheavy ions must increase with the ratio Te/Ti so that thetwo ion-acoustic modes can have the same fluctuation levels.

Study of Trace and Heavy Metals in Rural and Urban Aerosols of Uludağ and Bursa (Turkey)

The concentrations of heavy, trace elements and major ions measuredin the Uludag and Bursa aerosols were investigated to assess size distributions, spatial and temporal variability, sources and source regions affecting the composition of aerosols in Uludag and Bursa. A total of 81 samples were collected in two sites, one in Bursa city and another in the Uludag Mountain during two sampling campaigns. Daily samples were collected using a high volume sampler on Whatman 41 cellulose filters in Uludag, while three days interval samples were collected in Bursa using an automatic dichotomous sampler on PTFE Teflon filters. Samples were analysed for 15 trace and heavy metals (Al, Fe, Ba, Na, Mg, K, Mn, Ca, Cu), (V, Pb, Cd, Cr, Ni, Zn), and 4 major ions (SO42-, NO3-, Cl-), (NH4+) using ICP-AES, GFAAS, HPLC and UV/VIS Spectrophotometer,respectively. In general, concentrations of the metals measured inUludag aerosols were lower than those in Bursa. The concentrations of crustal elements were higher in summer than winter, while anthropogenic elements had higher concentrations in winter than summer. Most of the mass of crustal elements was concentrated in the coarse mode while the mass of the heavy metals was concentrated in the fine mode. Factor analysis revealed four factors with sources including crustal, industrial and combustion. Back trajectory calculations were used to determine long range contributions. These calculations showed that contributions were mostly from European countries, former Soviet Union countries, Black Sea and North Africa.

Effect of heavy ions on ponderomotive forces due to ion cyclotron waves

We study ponderomotive effects induced by the electromagnetic ion cyclotron (EMIC) waves in the Pel frequency band (0.2 to 5.0 Hz) in a two‐ion (H+ and one heavy ion, e.g., He+) plasma. Near the dayside boundary of the magnetosphere, the ponderomotive forces lead to a noticeable accumulation of cold plasma along the field line in two regions of minimum magnetic field intensity located symmetrically around the equator. In the inner magnetosphere, one maximum of cold plasma at the equator is found. At frequencies less than the heavy ion gyrofrequency, the accumulation of cold plasma increases with increasing heavy ion concentration. At frequencies above the heavy ion gyrofrequency, the ponderomotive forces due to EMIC waves are enhanced because of a resonance at the stop band frequencies. We investigate the stop band structure of EMIC waves in a nondipolar magnetosphere and discuss the properties of wave propagation along the field line for different heavy ion plasma concentrations.

MULTI-MEDIA CONCENTRATIONS OF HEAVY METALS AND MAJOR IONS FROM URBAN AND RURAL SITES IN NEW BRUNSWICK, CANADA

Concentrations of heavy metals and major ions were measured in precipitation, snowpack, garden soils and vegetables from urban and rural sites in New Brunswick in Atlantic Canada. Atmospheric loading of mercury, lead, cadmium, arsenic, strontium, and vanadium need further assessment. Vanadium concentrations in precipitation, snowpack, soils and vegetables showed an urban influence. Vanadium concentrations in the snowpack ranged between SO4 > NH4 > H > Mg > Cl > Na > K. Hydrogen ion equivalents were highest in the snowpack and precipitation from urban samples. Mean hydrogen ion concentrations ranged from 11 to 22 μeq L-1 in the snowpack compared with 18 to 41 μeq L-1 in event precipitation.

Electromagnetic ion cyclotron wave amplification and source regions in the magnetosphere

The amplification of electromagnetic ion cyclotron (EMIC) waves in the magnetosphere is studied by integrating local convective growth rates along the wave path. The integrated wave amplification is used to investigate the radial extent of wave source regions. Typical heavy ion concentrations (He+ ∼10‐20%, O+ ∼1‐10%) are considered in the calculation. In contrast to previous studies, the results presented indicate that the radial structure of the integrated wave amplification is controlled by the ion composition in the magnetosphere, as well as by the cold (or thermal) plasma density profile. It is found that the source region of the lowest‐frequency wave branch (i.e., the O+ wave branch here) is confined to the plasmapause and inside the plasmasphere, whereas the other wave branches (i.e., the He+ and H+ wave branches here) can be amplified over most of the magnetosphere. It is suggested that the structured Pc 1‐2 waves observed mainly on the ground are due to the lowest‐frequency wave branch, and the unstructured Pc 1‐2 waves observed both on the ground and in space result from the other wave branches.

An experimental study of electrostatic ion cyclotron waves in a two‐ion component plasma

Two‐ion component electrostatic ion cyclotron (EIC) waves are studied in a single‐ended Q‐machine containing variable concentrations of Cs+ and K+ ions. Measurements of the excitation and propagation characteristics of the waves are presented and compared with available theories. The waves are internally excited by drawing an electron current along the magnetic field to an 11‐mm exciter disk. Both Cs+ and K+ EIC waves can be simultaneously excited over a large range of relative ion concentrations. The EIC wave features are found to depend on the relative ion concentrations. As the light ion (K+) concentration is increased, the frequency of the heavy ion (Cs+) mode shifts toward its cyclotron frequency. Likewise, the frequency of the light ion mode approaches the light ion cyclotron frequency as the heavy ion concentration is increased. The critical drift velocity for the excitation of the heavy ion (Cs+) mode is more strongly dependent on the relative ion concentrations than that of the light ion (K+) mode. These results are of interest in the context of EIC wave excitation in the ionosphere.

Light ion concentrations in Jupiter's inner magnetosphere

In this paper, Voyager 1 plasma wave instrument observations of lightning‐generated whistlers are combined with Voyager 1 plasma instrument heavy ion (8 ≤ A/Z ≤ 64) charge concentrations to investigate the concentration of light ions (A/Z < 8) along the whistler propagation path. Two models for light ion concentration over dipole L shells for L between 5.2 and 6.2 are obtained, one giving a constant concentration along the field line and the other corresponding to an exponential density distribution. Near the equator the light ion concentration ranges from only about 1 to 10% of the heavy ion concentration, while outside of the torus, at distances of from 1 to 1.5 RJ above the equator, the light ions are the dominant species.

On characteristic frequencies of a five-component model of magnetospheric plasma

The author gives more general relations derived for characteristic frequencies of a more complex plasma model. One may assume that expressions derived herein, represent a more appropriate approximation of reality, especially in regions of ionospheric and magnetospheric plasma with a higher concentration of heavy ions.

Modifications in the maximum convective growth rate of the electromagnetic proton cyclotron instability due to the presence of thermal ions

The effect of thermal ions on the convective properties of the electromagnetic proton cyclotron instability is investigated. It is shown that when Ap < 1, where Ap is the proton anisotropy, cold ions, with relative specific charge mj/Zj mp ≥ 1, stabilize the convective growth of the instability. When Ap >1, the effect of thermal ions is to enhance the convective growth of the instabifity in the range where the real part of the frequency, ωr, is smaller than the ion gyrofrequency, Ωj. The maximum enhancement, corresponding to an optimum concentration of heavy ions, is shown to be a constant independent of the species. However, for each species, even for Ap > 1 (except for protons), there is always a range of values of Ap such that the species will stabilize the system. Heavier ions are shown to be more effective in enhancing the convective growth of the instability, in the sense that, the heavier they are, smaller relative concentrations are required to reach the constant value mentioned above. For sufficiently heavy species, the required concentration to optimize the convective growth, is independent of the species.

Concentration and mass distribution of charged species in sooting flames

Total concentration and mass distribution of charged species larger than about 300 amu were measured along the centerline of a premixed sooting acetylene/oxygen flat flame at 20 mmHg. Charge concentration was determined by measuring the electric current delivered to a Faraday cage in the detection chamber of a staged molecular beam flame sampling instrument having a quenching time of about 1 μs. Charge/mass ratio distributions were measured by the incremental electrical filtration of charged species from the beam. Mass and diameter distributions were than calculated by assuming unicharged species of density 2 g/cm 3 . The observed species, which include heavy hydrocarbon ions and charged soot particles, are of positive polarity. Their total concentration at fuel equivalence ratios in the range 2.1–3.0 and cold gas velocities of 31 and 38 cm/s ranges from 10 8 to 10 12 cm −3 , exhibits a distinct peak near the onset of soot formation, increases strongly with increasing fuel equivalence ratio, and decreases with increasing cold gas velocity. The mass distribution of charged species peaks sharply at a mass which increases with increasing height above the burner or time. At a fuel equivalence ratio of 2.25 and a cold gas velocity of 31 cm/s, the peak mass and its equivalent diameter increase from 1390 amu and 13just prior to the onset of visible soot formation to 7700 amu and 23about 2 ms later. The concentration of heavy hydrocarbon ions and that of heavy hydrocarbon molecules estimated previously decrease rapidly with the onset of soot formation in a manner that correlates with the initially fast surface gorwth of soot particles. Thus the heavy hydrocarbons appear to include both soot nuclei and surface growth intermediates. The concentrations of heavy hydrocarbon ions are much larger than the peak concentrations of soot particles. Therefore ionic nucleation of soot particles is feasible for these conditions, and a tentative mechanism is described.

Studies of positive-ion composition in the equatorialD-region ionosphere

Evaluation of two daytime D-region positive-ion composition measurements performed at Thumba, India, for solar zenith angles of 53.2 and 27.8 deg. Comparison of upleg ram with downleg wake data shows a large increase in the concentration of heavy ions 48(+), NO(+) . H2O; 55(+), H3O(+) . (H2O)2; and M(+) greater than 65(+) for the downleg reduced shock condition. Peak concentrations of 48(+) and 55(+) occur at unit optical depth for Lyman alpha radiation. The ion 37(+), H3O(+) . H2O, is dominant for chi = 27.8 deg, but not for chi = 53.2 deg, consistent above 80 km with an origin from the X-ray production of O2(+). Laboratory measurements have shown that the ion, NO(+), can be transferred to heavy hydrates 48(+), 55(+), and M(+) greater than 65(+) by a reaction chain starting with NO(+) + X + M = NO(+) . X + M, where X can be O2, N2, CO2 or a combination of all three, depending on the rate of reaction. This chain, together with a similar reaction scheme starting with O2(+) and ending in 19(+), 37(+), and heavier clusters, is used to provide a consistent explanation for the hydrated ions observed in the D region.

Characterization of MOSFETs formed by gate masked ion implantation technique

Ion implanted MOSFETs formed with the gate as source-drain mask were described at the 1966 I EDM. These devices exhibited low Miller capacitance and freedom from critical mask alignment. Hewever, the devices were unstable because ions were implanted into unpassivated silicon. In addition, the characteristics were fixed because heavy ion concentrations were required for contact formation. MOSFETs formed by a combination of diffusion and ion implantation have recently been investigated. They retain the major attributes of the previously described device, but have greater stability and flexibility of characteristics. An offset-gate diffused device is first formed by standard techniques. The drain p-region is then extended to the edge of the gate by Boron implantation through the oxide-passivated area connecting the gate and diffused drain. The metallic gate acts as a mask to prevent ion doping of the modulated channel region. Device stability is achieved by implanting the ions through a passivated oxide layer. With diffused contact areas, the implanted doping concentration can be varied to allow formation of devices which simulate the Insulated Gate Tetrode. A light implantation produces high drain to source breakdown and low frequency response while heavy implantation produces low breakdown and high frequency response. The device fabrication procedure will be described. Noise, frequency response, and drain to sourer breakdown voltage will be evaluated at various implantation doping levels. Results will be compared with conventional devices.

The gyro-frequency in the ArcticE-layer

Calculation of the gyro-frequency in the E-layer at arctic stations from measurements of critical radio-frequency differences gives a lower magnetic field than that obtained by extrapolation of the terrestrial field measured at ground-level, and, at one station, a large semi-diurnal variation with maxima at 06h and 18h local time. Ray-path deflections which can explain similar effects previously reported for the F-layer cannot be responsible in the E-layer because of the opposite sense of this deviation and because of the small layer-thickness. Moreover, no semi-diurnal variation was found in the F-layer. It is shown that these new E-layer phenomena may be due to a variable concentration of heavy ions rising to over 4,000 times the density of free electrons.