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Sample records for measured electron density

  1. Electron density measurements for plasma adaptive optics

    NASA Astrophysics Data System (ADS)

    Neiswander, Brian W.

    Over the past 40 years, there has been growing interest in both laser communications and directed energy weapons that operate from moving aircraft. As a laser beam propagates from an aircraft in flight, it passes through boundary layers, turbulence, and shear layers in the near-region of the aircraft. These fluid instabilities cause strong density gradients which adversely affect the transmission of laser energy to a target. Adaptive optics provides corrective measures for this problem but current technology cannot respond quickly enough to be useful for high speed flight conditions. This research investigated the use of plasma as a medium for adaptive optics for aero-optics applications. When a laser beam passes through plasma, its phase is shifted proportionally to the electron density and gas heating within the plasma. As a result, plasma can be utilized as a dynamically controllable optical medium. Experiments were carried out using a cylindrical dielectric barrier discharge plasma chamber which generated a sub-atmospheric pressure, low-temperature plasma. An electrostatic model of this design was developed and revealed an important design constraint relating to the geometry of the chamber. Optical diagnostic techniques were used to characterize the plasma discharge. Single-wavelength interferometric experiments were performed and demonstrated up to 1.5 microns of optical path difference (OPD) in a 633 nm laser beam. Dual-wavelength interferometry was used to obtain time-resolved profiles of the plasma electron density and gas heating inside the plasma chamber. Furthermore, a new multi-wavelength infrared diagnostic technique was developed and proof-of-concept simulations were conducted to demonstrate the system's capabilities.

  2. Estimation of topside electron density profile using on-orbit measured GPS and electron density data.

    NASA Astrophysics Data System (ADS)

    Lee, J.

    2015-12-01

    The topside ionophere have lacks of information about plasma, but it is important for human beings and scientific applicaiton. We establish an estimation method for electron density profile using Langmuir Probe and GPS data of CHAMP satellite and have comparision the method results with other satellites measurements. In order to develop the model, hydrostatic mapping function, vertical scale height, and vertical TEC(Total Electron Contents) are used for calculations. The electron density and GPS data with hydrostatic mapping function give the vertical TEC and after some algebra using exponential model of density profile give the vertical scale height of ionosphere. The scale height have about 10^2~10^3 km order of magnitude so it can be used exponential model again since the altitude of CHAMP. Therefore, apply the scale height to exponoential model we can get the topside electron density profile. The result of the density profile model can be compared with other satellite data as STSAT-1, ROCSAT, DMSP which is measured the electron density in similar Local Time, Latitude, Longitude but above the CHAMP. This comparison shows the method is accecptable and it can be applied to other reseach for topside ionosphere.

  3. Measurement of electron density using reactance cutoff probe

    NASA Astrophysics Data System (ADS)

    You, K. H.; You, S. J.; Kim, D. W.; Na, B. K.; Seo, B. H.; Kim, J. H.; Seong, D. J.; Chang, H. Y.

    2016-05-01

    This paper proposes a new measurement method of electron density using the reactance spectrum of the plasma in the cutoff probe system instead of the transmission spectrum. The highly accurate reactance spectrum of the plasma-cutoff probe system, as expected from previous circuit simulations [Kim et al., Appl. Phys. Lett. 99, 131502 (2011)], was measured using the full two-port error correction and automatic port extension methods of the network analyzer. The electron density can be obtained from the analysis of the measured reactance spectrum, based on circuit modeling. According to the circuit simulation results, the reactance cutoff probe can measure the electron density more precisely than the previous cutoff probe at low densities or at higher pressure. The obtained results for the electron density are presented and discussed for a wide range of experimental conditions, and this method is compared with previous methods (a cutoff probe using the transmission spectrum and a single Langmuir probe).

  4. Measurement of electron density and temperature in plasmas

    NASA Technical Reports Server (NTRS)

    Billman, K. W.; Rowley, P. D.; Presley, L. L.; Stallcop, J.

    1972-01-01

    Application of two laser wavelengths passing through plasma measures electron density and temperature. Function depends on determining absorption of light at two wavelengths. Nature of reaction is explained and schematic diagram of equipment is included.

  5. Measuring ionospheric electron density using the plasma frequency probe

    SciTech Connect

    Jensen, M.D.; Baker, K.D. )

    1992-02-01

    During the past decade, the plasma frequency probe (PFP) has evolved into an accurate, proven method of measuring electron density in the ionosphere above about 90 km. The instrument uses an electrically short antenna mounted on a sounding rocket that is immersed in the plasma and notes the frequency where the antenna impedance is large and nonreactive. This frequency is closely related to the plasma frequency, which is a direct function of free electron concentration. The probe uses phase-locked loop technology to follow a changing electron density. Several sections of the plasma frequency probe circuitry are unique, especially the voltage-controlled oscillator that uses both an electronically tuned capacitor and inductor to give the wide tuning range needed for electron density measurements. The results from two recent sounding rocket flights (Thunderstorm II and CRIT II) under vastly different plasma conditions demonstrate the capabilities of the PFP and show the importance of in situ electron density measurements of understanding plasma processes. 9 refs.

  6. Rocket radio measurement of electron density in the nighttime ionosphere

    NASA Technical Reports Server (NTRS)

    Gilchrist, B. E.; Smith, L. G.

    1979-01-01

    One experimental technique based on the Faraday rotation effect of radio waves is presented for measuring electron density in the nighttime ionosphere at midlatitudes. High frequency linearly-polarized radio signals were transmitted to a linearly-polarized receiving system located in a spinning rocket moving through the ionosphere. Faraday rotation was observed in the reference plane of the rocket as a change in frequency of the detected receiver output. The frequency change was measured and the information was used to obtain electron density data. System performance was evaluated and some sources of error were identified. The data obtained was useful in calibrating a Langmuir probe experiment for electron density values of 100/cu cm and greater. Data from two rocket flights are presented to illustrate the experiment.

  7. Electron density measurements in the ITER fusion plasma

    NASA Astrophysics Data System (ADS)

    Watts, Christopher; Udintsev, Victor; Andrew, Philip; Vayakis, George; Van Zeeland, Michael; Brower, David; Feder, Russell; Mukhin, Eugene; Tolstyakov, Sergey

    2013-08-01

    The operation of ITER requires high-quality estimates of the plasma electron density over multiple regions in the plasma for plasma evaluation, plasma control and machine protection purposes. Although the density regimes of ITER are not very different from those of existing tokamaks (1018-1021 m-3), the severe conditions of the fusion plasma environment present particular challenges to implementing these density diagnostics. In this paper we present an overview of the array of ITER electron density diagnostics designed to measure over the entire ITER domain: plasma core, pedestal, edge, scrape-off layer and divertor. It will focus on the challenges faced in making these measurements, and the technical solutions of the current designs.

  8. Seismo-ionospheric coupling appearing as equatorial electron density enhancements observed via DEMETER electron density measurements

    NASA Astrophysics Data System (ADS)

    Ryu, K.; Lee, E.; Chae, J. S.; Parrot, M.; Pulinets, S.

    2014-10-01

    We report the processes and results of statistical analysis on the ionospheric electron density data measured by the Detection of Electro-Magnetic Emissions Transmitted from Earthquake Regions (DEMETER) satellite over a period of 6 years (2005-2010), in order to investigate the correlation between seismic activity and equatorial plasma density variations. To simplify the analysis, three equatorial regions with frequent earthquakes were selected and then one-dimensional time series analysis between the daily seismic activity indices and the equatorial ionization anomaly (EIA) intensity indices, which represent relative equatorial electron density increase, were performed for each region. The statistically significant values of the lagged cross-correlation function, particularly in the region with minimal effects of longitudinal asymmetry, indicate that some of the very large earthquakes with M > 5.0 in the low-latitude region can accompany observable precursory and concurrent EIA enhancements, even though the seismic activity is not the most significant driver of the equatorial ionospheric evolution. The physical mechanisms of the seismo-ionospheric coupling is consistent with our observation, and the possibility of earthquake prediction using the EIA intensity variation is discussed.

  9. Absolute electron density measurements in the equatorial ionosphere

    NASA Technical Reports Server (NTRS)

    Baker, K. D.; Howlett, L. C.; Rao, N. B.; Ulwick, J. C.; Labelle, J.

    1985-01-01

    Accurate measurement of the electron density profile and its variations is crucial to further progress in understanding the physics of the disturbed equatorial ionosphere. To accomplish this, a plasma frequency probe was included in the payload complement of two rockets flown during the Condor rocket campaign conducted from Peru in March 1983. This paper presents density profiles of the disturbed equatorial ionosphere from a night-time flight in which spread-F conditions were present and from a day-time flight during strong electrojet conditions. Results from both flights are in excellent agreement with simultaneous radar data in that the regions of highly disturbed plasma coincide with the radar signatures. The spread-F rocket penetrated a topside depletion during both the upleg and downleg. The electrojet measurements showed a profile peaking at 1.3 x 10 to the 5th per cu cm at 106 km, with large scale fluctuations having amplitudes of roughly 10 percent seen only in the upward gradient in electron density. This is in agreement with plasma instability theory. It is further shown that simultaneous measurements by fixed-bias Langmuir probes, when normalized at a single point to the altitude profile of electron density, are inadequate to correctly parameterize the observed enhancements and depletions.

  10. Plasma actuator electron density measurement using microwave perturbation method

    SciTech Connect

    Mirhosseini, Farid; Colpitts, Bruce

    2014-07-21

    A cylindrical dielectric barrier discharge plasma under five different pressures is generated in an evacuated glass tube. This plasma volume is located at the center of a rectangular copper waveguide cavity, where the electric field is maximum for the first mode and the magnetic field is very close to zero. The microwave perturbation method is used to measure electron density and plasma frequency for these five pressures. Simulations by a commercial microwave simulator are comparable to the experimental results.

  11. Measurements of electron number density and plasma temperature using LIBS

    NASA Astrophysics Data System (ADS)

    Zhao, Xiao-xia; Luo, Wen-feng; He, Jun-fang; Wang, Hong-ying; Yang, Sen-lin; Li, Yuan-yuan

    2016-10-01

    Plasma produced by the radiation of a 1064 nm Nd:YAG laser focused onto a standard aluminum alloy E311 was studied spectroscopically. The electron density was inferred by measuring the Stark broadened line profile of Cu I 324.75 nm at a distance of 1.5 mm from the target surface with the laser irradiance of 3.27 GW/cm2. The electron temperature was determined using the Boltzmann plot method with eight neutral iron lines. At the same time, the validity of the assumption of local thermodynamic equilibrium was discussed in light of the results obtained.

  12. Cutoff probe using Fourier analysis for electron density measurement

    SciTech Connect

    Na, Byung-Keun; You, Kwang-Ho; Kim, Dae-Woong; Chang, Hong-Young; You, Shin-Jae; Kim, Jung-Hyung

    2012-01-15

    This paper proposes a new method for cutoff probe using a nanosecond impulse generator and an oscilloscope, instead of a network analyzer. The nanosecond impulse generator supplies a radiating signal of broadband frequency spectrum simultaneously without frequency sweeping, while frequency sweeping method is used by a network analyzer in a previous method. The transmission spectrum (S21) was obtained through a Fourier analysis of the transmitted impulse signal detected by the oscilloscope and was used to measure the electron density. The results showed that the transmission frequency spectrum and the electron density obtained with a new method are very close to those obtained with a previous method using a network analyzer. And also, only 15 ns long signal was necessary for spectrum reconstruction. These results were also compared to the Langmuir probe's measurements with satisfactory results. This method is expected to provide not only fast measurement of absolute electron density, but also function in other diagnostic situations where a network analyzer would be used (a hairpin probe and an impedance probe) by replacing the network analyzer with a nanosecond impulse generator and an oscilloscope.

  13. Electron density measurements during the NLC-91 campaign

    NASA Technical Reports Server (NTRS)

    Ulwick, J. C.; Kelley, Michael C.; Alcala, C.

    1994-01-01

    A Super Arcas rocket, MISTI B, containing DC and RF probes, was launched as a part of the PMSE (Polar Mesosphere Summer Echoes) Salvo during the NLC-91 (Noctilucent Cloud) campaign to measure electron density irregularities with high spatial resolution. Measurements of large and small scale structures in the electron density were made on rocket ascent and descent at the altitudes of 86.5 and 88.5 +/- 0.5 km corresponding to the two altitudes of strongest backscatter recorded by the nearby CUPRI (Cornell University Portable Radar Interferometer) radar. Power spectra of the fluctuations shows two different structuring and scattering mechanisms exist at altitudes only 1 km apart. Since the rocket apogee was 89 km, the rocket was in the height range 88.5 +/- 0.5 km for 30 seconds giving an unusual measurement of horizontal structure over a distance of 5.5 km. Using the simultaneous DC and RF probe measurements of electron depletions and sharp gradient in the lower layer, the role of aerosols in creating these depletions and gradients is speculated upon.

  14. Rocket-borne measurements of electron temperature and density with the Electron Retarding Potential Analyzer instrument

    NASA Astrophysics Data System (ADS)

    Cohen, I. J.; Widholm, M.; Lessard, M. R.; Riley, P.; Heavisides, J.; Moen, J. I.; Clausen, L. B. N.; Bekkeng, T. A.

    2016-07-01

    Determining electron temperature in the ionosphere is a fundamentally important measurement for space science. Obtaining measurements of electron temperatures at high altitudes (>700 km) is difficult because of limitations on ground-based radar and classic spacecraft instrumentation. In light of these limitations, the rocket-borne Electron Retarding Potential Analyzer (ERPA) was developed to allow for accurate in situ measurement of ionospheric electron temperature with a simple and low-resource instrument. The compact ERPA, a traditional retarding potential analyzer with multiple baffle collimators, allows for a straightforward calculation of electron temperature. Since its first mission in 2004, it has amassed significant flight heritage and obtained data used in multiple studies investigating a myriad of phenomena related to magnetosphere-ionosphere coupling. In addition to highlighting the scientific contributions of the ERPA instrument, this paper outlines its theory and operation, the methodology used to obtain electron temperature measurements, and a comparative study suggesting that the ERPA can also provide electron density measurements.

  15. Accuracy of cutoff probe for measuring electron density: simulation and experiment

    NASA Astrophysics Data System (ADS)

    Kim, Dae-Woong; You, Shin-Jae; Kim, Si-June; Lee, Jang-Jae; Kim, Jung-Hyung; Oh, Wang-Yuhl

    2016-09-01

    The electron density has been used for characterizing the plasma for basic research as well as industrial application. To measure the exact electron density, various type of microwave probe has been developed and improved. The cutoff probe is a promising technique inferring the electron density from the plasma resonance peak on the transmission spectrum. In this study, we present the accuracy of electron density inferred from cutoff probe. The accuracy was investigated by electromagnetic simulation and experiment. The discrepancy between the electron densities from the cutoff probe and other sophisticated microwave probes were investigated and discussed. We found that the cutoff probe has good accuracy in inferred electron density. corresponding author.

  16. Time-resolved electron density and electron temperature measurements in nanosecond pulse discharges in helium

    NASA Astrophysics Data System (ADS)

    Roettgen, A.; Shkurenkov, I.; Simeni Simeni, M.; Petrishchev, V.; Adamovich, I. V.; Lempert, W. R.

    2016-10-01

     ≈  4.25 eV, attained after the surface ionization wave reaches the grounded electrode. The sensitivity of the present diagnostics is too low to measure electron density in the plasma during surface ionization wave propagation (estimated to be below n e  ≈  1013 cm-3). After peaking during the primary current pulse, the electron density decays due to dissociative recombination. Electron temperature decreases rapidly over ~150 ns after the primary current pulse rise, to T e  ≈  0.5 eV, followed by a much more gradual electron cooling between the primary and the secondary discharge pulses, due to superelastic collisions providing moderate electron heating in the afterglow.

  17. Electron density and electron temperature measurements in nanosecond pulse discharges over liquid water surface

    NASA Astrophysics Data System (ADS)

    Simeni Simeni, M.; Roettgen, A.; Petrishchev, V.; Frederickson, K.; Adamovich, I. V.

    2016-12-01

    Time-resolved electron density, electron temperature, and gas temperature in nanosecond pulse discharges in helium and O2-He mixtures near liquid water surface are measured using Thomson/pure rotational Raman scattering, in two different geometries, (a) ‘diffuse filament’ discharge between a spherical high-voltage electrode and a grounded pin electrode placed in a reservoir filled with distilled water, with the tip exposed, and (b) dielectric barrier discharge between the high-voltage electrode and the liquid water surface. A diffuse plasma filament generated between the electrodes in helium during the primary discharge pulse exhibits noticeable constriction during the secondary discharge pulse several hundred ns later. Adding oxygen to the mixture reduces the plasma filament diameter and enhances constriction during the secondary pulse. In the dielectric barrier discharge, diffuse volumetric plasma occupies nearly the entire space between the high voltage electrode and the liquid surface, and extends radially along the surface. In the filament discharge in helium, adding water to the container results in considerable reduction of plasma lifetime compared to the discharge in dry helium, by about an order of magnitude, indicating rapid electron recombination with water cluster ions. Peak electron density during the pulse is also reduced, by about a factor of two, likely due to dissociative attachment to water vapor during the discharge pulse. These trends become more pronounced as oxygen is added to the mixture, which increases net rate of dissociative attachment. Gas temperature during the primary discharge pulse remains near room temperature, after which it increases up to T ~ 500 K over 5 µs and decays back to near room temperature before the next discharge pulse several tens of ms later. As expected, electron density and electron temperature in diffuse DBD plasmas are considerably lower compared to peak values in the filament discharge. Use of Thomson

  18. Electron density dependence of impedance probe plasma potential measurements

    SciTech Connect

    Walker, D. N.; Blackwell, D. D.; Amatucci, W. E.

    2015-08-15

    In earlier works, we used spheres of various sizes as impedance probes in demonstrating a method of determining plasma potential, φ{sub p}, when the probe radius is much larger than the Debye length, λ{sub D}. The basis of the method in those works [Walker et al., Phys. Plasmas 13, 032108 (2006); ibid. 15, 123506 (2008); ibid. 17, 113503 (2010)] relies on applying a small amplitude signal of fixed frequency to a probe in a plasma and, through network analyzer-based measurements, determining the complex reflection coefficient, Γ, for varying probe bias, V{sub b}. The frequency range of the applied signal is restricted to avoid sheath resonant effects and ion contributions such that ω{sub pi} ≪ ω ≪ ω{sub pe}, where ω{sub pi} is the ion plasma frequency and ω{sub pe} is the electron plasma frequency. For a given frequency and applied bias, both Re(Z{sub ac}) and Im(Z{sub ac}) are available from Γ. When Re(Z{sub ac}) is plotted versus V{sub b}, a minimum predicted by theory occurs at φ{sub p} [Walker et al., Phys. Plasmas 17, 113503 (2010)]. In addition, Im(Z{sub ac}) appears at, or very near, a maximum at φ{sub p}. As n{sub e} decreases and the sheath expands, the minimum becomes harder to discern. The purpose of this work is to demonstrate that when using network analyzer-based measurements, Γ itself and Im(Z{sub ac}) and their derivatives are useful as accompanying indicators to Re(Z{sub ac}) in these difficult cases. We note the difficulties encountered by the most commonly used plasma diagnostic, the Langmuir probe. Spherical probe data is mainly used in this work, although we present limited data for a cylinder and a disk. To demonstrate the effect of lowered density as a function of probe geometry, we compare the cylinder and disk using only the indicator Re(Z{sub ac})

  19. Measurements of Electron Density Profile and Fluctuations on HSX*

    NASA Astrophysics Data System (ADS)

    Deng, C.; Brower, D. L.; Ding, W. X.; Almagri, A. F.; Anderson, D. T.; Anderson, F. S. B.; Gerhardt, S. P.; Probert, P.; Radder, J.; Talmadge, J. N.

    2001-10-01

    The 288 GHz interferometer system on the quasi-helical stellarator HSX views the plasma cross section along 9 adjacent chords with 1.5 cm spacing. At this frequency refraction is manageable but requires correction when performing inversions. The interferometer has sensitivity n_edl = 8 x 10^11 cm-2 and frequency response up to 1 MHz. Improved time response permits measurement of high-frequency density fluctuations as well as fast changes to the equilibrium profile. First results from HSX with 2nd harmonic ECH at 28 GHz, using a 5 chord version of the interferometer, indicate that the density profile is quite peaked for both quasi-helically symmetric (QHS) plasmas and those where the quasisymmetry is broken (mirror mode) for ne = 1 x 10^12 cm-3. However, for densities ne = 3 x 10^11 cm-3, the profile for the QHS plasma (high stored energy) is narrower when compared to the mirror mode (low stored energy). Density profile variation with plasma configuration and resonant heating location using the 9 channel interferometer will be described. For high density HSX plasmas, ne > 3 x 10^12 cm-3, coherent oscillations are observed in the line-integrated density traces which are out of phase across the magnetic axis. These m=1 oscillations are observed at frequencies of 1-2 kHz and result in a periodic displacement of the density profile. *Supported by USDOE under grant DE-FG03-01ER-54615, Task III and DE-FG02-93ER54222.

  20. Electron density and electron temperature measurement in a bi-Maxwellian electron distribution using a derivative method of Langmuir probes

    SciTech Connect

    Choi, Ikjin; Chung, ChinWook; Youn Moon, Se

    2013-08-15

    In plasma diagnostics with a single Langmuir probe, the electron temperature T{sub e} is usually obtained from the slope of the logarithm of the electron current or from the electron energy probability functions of current (I)-voltage (V) curve. Recently, Chen [F. F. Chen, Phys. Plasmas 8, 3029 (2001)] suggested a derivative analysis method to obtain T{sub e} by the ratio between the probe current and the derivative of the probe current at a plasma potential where the ion current becomes zero. Based on this method, electron temperatures and electron densities were measured and compared with those from the electron energy distribution function (EEDF) measurement in Maxwellian and bi-Maxwellian electron distribution conditions. In a bi-Maxwellian electron distribution, we found the electron temperature T{sub e} obtained from the method is always lower than the effective temperatures T{sub eff} derived from EEDFs. The theoretical analysis for this is presented.

  1. Absolute Measurement of Electron Cloud Density in aPositively-Charged Particle Beam

    SciTech Connect

    Kireeff Covo, Michel; Molvik, Arthur W.; Friedman, Alex; Vay,Jean-Luc; Seidl, Peter A.; Logan, Grant; Baca, David; Vujic, Jasmina L.

    2006-04-27

    Clouds of stray electrons are ubiquitous in particle accelerators and frequently limit the performance of storage rings. Earlier measurements of electron energy distribution and flux to the walls provided only a relative electron cloud density. We have measured electron accumulation using ions expelled by the beam. The ion energy distribution maps the depressed beam potential and gives the dynamic cloud density. Clearing electrode current reveals the static background cloud density, allowing the first absolute measurement of the time-dependent electron cloud density during the beam pulse.

  2. Absolute Measurement of Electron Cloud Density in a Positively-Charged Particle Beam

    SciTech Connect

    Covo, M K; Molvik, A W; Friedman, A; Vay, J; Seidl, P A; Logan, B G; Baca, D; Vujic, J L

    2006-05-18

    Clouds of stray electrons are ubiquitous in particle accelerators and frequently limit the performance of storage rings. Earlier measurements of electron energy distribution and flux to the walls provided only a relative electron cloud density. We have measured electron accumulation using ions expelled by the beam. The ion energy distribution maps the depressed beam potential and gives the dynamic cloud density. Clearing electrode current reveals the static background cloud density, allowing the first absolute measurement of the time-dependent electron cloud density during the beam pulse.

  3. Absolute measurement of electron-cloud density in a positively charged particle beam.

    PubMed

    Kireeff Covo, Michel; Molvik, Arthur W; Friedman, Alex; Vay, Jean-Luc; Seidl, Peter A; Logan, Grant; Baca, David; Vujic, Jasmina L

    2006-08-04

    Clouds of stray electrons are ubiquitous in particle accelerators and frequently limit the performance of storage rings. Earlier measurements of electron energy distribution and flux to the walls provided only a relative electron-cloud density. We have measured electron accumulation using ions expelled by the beam. The ion energy distribution maps the depressed beam potential and gives the dynamic cloud density. Clearing electrode current reveals the static background cloud density, allowing the first absolute measurement of the time-dependent electron-cloud density during the beam pulse.

  4. Electron density measurements in a photoinitiated, impulse-enhanced, electrically excited laser gas discharge

    NASA Astrophysics Data System (ADS)

    Seguin, V. A.; Seguin, H. J. J.; Capjack, C. E.; Nikumb, S. K.

    1986-11-01

    Measurements of the electron density within a photo-initiated, impulse-enhanced, electrically excited (PIE) laser gas discharge are presented. Ion current measurements were made using a single Langmuir electrostatic probe positioned within the laser discharge volume. Calculations of the electron density were made utilizing a thick-sheath analysis. The results indicate that the electron density increases by two orders of magnitude as the pulser power level is increased. In addition, the electron density was observed to decrease markedly as the dc discharge current was increased.

  5. Wavefront-sensor-based electron density measurements for laser-plasma accelerators

    SciTech Connect

    Plateau, Guillaume; Matlis, Nicholas; Geddes, Cameron; Gonsalves, Anthony; Shiraishi, Satomi; Lin, Chen; van Mourik, Reinier; Leemans, Wim

    2010-02-20

    Characterization of the electron density in laser produced plasmas is presented using direct wavefront analysis of a probe laser beam. The performance of a laser-driven plasma-wakefield accelerator depends on the plasma wavelength, hence on the electron density. Density measurements using a conventional folded-wave interferometer and using a commercial wavefront sensor are compared for different regimes of the laser-plasma accelerator. It is shown that direct wavefront measurements agree with interferometric measurements and, because of the robustness of the compact commercial device, have greater phase sensitivity, straightforward analysis, improving shot-to-shot plasma-density diagnostics.

  6. Absolute measurements of night-time electron density using ISR gyro lines

    NASA Astrophysics Data System (ADS)

    Bhatt, Asti; Kelley, Michael; Nicolls, Michael; Sulzer, Michael

    2012-07-01

    Gyro line in Incoherent Scatter Spectrum is the underused cousin of the more popular Plasma line. This is because it is very weak during the day and stronger during dawn and dusk hours. When the electron density is such that the electron plasma frequency drops below the electron gyro frequency, the gyro line frequency becomes proportional to the electron density. This is during a time when the plasma line is no longer detected, and we have no other means for getting precise measurements for absolute electron density. In this paper, we will present a linear equation for the gyro line frequency and measurements from the Arecibo radar in Puerto Rico, showing comparison with the plasma line data and derived electron density.

  7. Rocket measurements of ion and electron densities in the D-region during sunrise.

    NASA Technical Reports Server (NTRS)

    Pedersen, A.; Kane, J. A.

    1971-01-01

    Results from two rockets launched near sunrise at White Sands, N. Mex., when positive ion and electron densities were measured in the D-region for solar zenith angles of 91 and 79 deg. The measurements cover the height range 80 to 110 km and complement previous vlf observations and rocket measurements of electron density. It is shown that the majority of negative ions in this height range are detached near to after ground sunrise. On the basis of these measurements it is possible to discuss electron affinity of negative ions and ion production functions during twilight.

  8. Automated determination of electron density from electric field measurements on the Van Allen Probes spacecraft

    NASA Astrophysics Data System (ADS)

    Zhelavskaya, Irina; Kurth, William; Spasojevic, Maria; Shprits, Yuri

    2016-07-01

    We present the Neural-network-based Upper-hybrid Resonance Determination (NURD) algorithm for automatic inference of the electron number density from plasma wave measurements made onboard NASA's Van Allen Probes mission. A feedforward neural network is developed to determine the upper hybrid resonance frequency, f_{uhr}, from electric field measurements, which is then used to calculate the electron number density. In previous missions, the plasma resonance bands were manually identified, and there have been few attempts to do robust, routine automated detections. We describe the design and implementation of the algorithm and perform an initial analysis of the resulting electron number density distribution obtained by applying NURD to 2.5 years of data collected with the EMFISIS instrumentation suite of the Van Allen Probes mission. Densities obtained by NURD are compared to those obtained by another recently developed automated technique and also to an existing empirical plasmasphere and trough density model.

  9. Electron cloud density measurements in accelerator beam-pipe using resonant microwave excitation

    NASA Astrophysics Data System (ADS)

    Sikora, John P.; Carlson, Benjamin T.; Duggins, Danielle O.; Hammond, Kenneth C.; De Santis, Stefano; Tencate, Alister J.

    2014-08-01

    An accelerator beam can generate low energy electrons in the beam-pipe, generally called electron cloud, that can produce instabilities in a positively charged beam. One method of measuring the electron cloud density is by coupling microwaves into and out of the beam-pipe and observing the response of the microwaves to the presence of the electron cloud. In the original technique, microwaves are transmitted through a section of beam-pipe and a change in EC density produces a change in the phase of the transmitted signal. This paper describes a variation on this technique in which the beam-pipe is resonantly excited with microwaves and the electron cloud density calculated from the change that it produces in the resonant frequency of the beam-pipe. The resonant technique has the advantage that measurements can be localized to sections of beam-pipe that are a meter or less in length with a greatly improved signal to noise ratio.

  10. The first in situ electron temperature and density measurements of the Martian nightside ionosphere

    NASA Astrophysics Data System (ADS)

    Fowler, C. M.; Andersson, L.; Ergun, R. E.; Morooka, M.; Delory, G.; Andrews, D. J.; Lillis, Robert J.; McEnulty, T.; Weber, T. D.; Chamandy, T. M.; Eriksson, A. I.; Mitchell, D. L.; Mazelle, C.; Jakosky, B. M.

    2015-11-01

    The first in situ nightside electron density and temperature profiles at Mars are presented as functions of altitude and local time (LT) from the Langmuir Probe and Waves (LPW) instrument on board the Mars Atmosphere and Volatile EvolutioN (MAVEN) mission spacecraft. LPW is able to measure densities as low as ˜100 cm-3, a factor of up to 10 or greater improvement over previous measurements. Above 200 km, near-vertical density profiles of a few hundred cubic centimeters were observed for almost all nightside LT, with the lowest densities and highest temperatures observed postmidnight. Density peaks of a few thousand cubic centimeters were observed below 200 km at all nightside LT. The lowest temperatures were observed below 180 km and approach the neutral atmospheric temperature. One-dimensional modeling demonstrates that precipitating electrons were able to sustain the observed nightside ionospheric densities below 200 km.

  11. Measurements of electron density and energy content in the VX-30 helicon discharge

    NASA Astrophysics Data System (ADS)

    Sciamma, Ella; Chavers, Greg; Chang-Diaz, Franklin

    2005-10-01

    We have observed plasma conditions at several locations in the VASIMR experiment, VX-30, a 20 kW helicon plasma expanding into a nozzle. - A three frequency interferometer (70, 90, 110 GHz) provided electron densities at these locations. - We made absolutely calibrated spectroscopic measurements of He I and He II lines in the UV, visible, and near IR. - A comparison with a collisional radiative model suggested that the actual electron density distribution function was not a Maxwellian, but rather was significantly underpopulated at higher electron energies. - We will present preliminary results comparing our measurements with a spectral model using a non Maxwellian distribution.

  12. Laser Thomson scattering measurements of electron temperature and density in a hall-effect plasma

    NASA Astrophysics Data System (ADS)

    Washeleski, Robert L.

    Hall-effect thrusters (HETs) are compact electric propulsion devices with high specific impulse used for a variety of space propulsion applications. HET technology is well developed but the electron properties in the discharge are not completely understood, mainly due to the difficulty involved in performing accurate measurements in the discharge. Measurements of electron temperature and density have been performed using electrostatic probes, but presence of the probes can significantly disrupt thruster operation, and thus alter the electron temperature and density. While fast-probe studies have expanded understanding of HET discharges, a non-invasive method of measuring the electron temperature and density in the plasma is highly desirable. An alternative to electrostatic probes is a non-perturbing laser diagnostic technique that measures Thomson scattering from the plasma. Thomson scattering is the process by which photons are elastically scattered from the free electrons in a plasma. Since the electrons have thermal energy their motion causes a Doppler shift in the scattered photons that is proportional to their velocity. Like electrostatic probes, laser Thomson scattering (LTS) can be used to determine the temperature and density of free electrons in the plasma. Since Thomson scattering measures the electron velocity distribution function directly no assumptions of the plasma conditions are required, allowing accurate measurements in anisotropic and non-Maxwellian plasmas. LTS requires a complicated measurement apparatus, but has the potential to provide accurate, non-perturbing measurements of electron temperature and density in HET discharges. In order to assess the feasibility of LTS diagnostics on HETs non-invasive measurements of electron temperature and density in the near-field plume of a Hall thruster were performed using a custom built laser Thomson scattering diagnostic. Laser measurements were processed using a maximum likelihood estimation method

  13. Development and application of diagnostic instrumentation for measurement of electron density and conductivity

    SciTech Connect

    Bauman, L.E.

    1990-05-01

    The purpose of this contract was to assemble and demonstrate in the laboratory a Faraday rotation system for measurement of electron density and conductivity, with the intent to produce a system suitable for diagnostic support of the development of pulsed, space-based magnetohydrodynamic (MHD) power systems. Two system configurations were tested: (1) a rotating polarizer and (2) a beam splitting polarizer. Due to the short path length plasma produced in the laboratory flame, the long wavelength 496 {mu}m methyl fluoride laser line was used and only the more sensitive rotating polarizer configuration was used for the demonstration experiments. Electron number densities from 2 {times} 10{sup 19} to 9 {times} 10{sup 19} were measured with good agreement to statistical equilibrium (Saha) calculations using emission absorption-measured flame temperatures and neutral seed atom number seed atom nuclear densities. The electron collision frequencies were measured by transmission measurements. Combining these two measurements gave measured electron conductivities of between 4 and 12 mohs/m. These results compared reasonably well with those found with an electron collision frequency model combined with chemical equilibrium calculations and the emission absorption measurements. Ellipticity measurements of electron collision frequency were not possible due to the short path length of the laboratory plasma. 46 refs., 25 figs., 9 tabs.

  14. Automated Determination of Electron Density from Electric Field Measurements on the Van Allen Probes Spacecraft

    NASA Astrophysics Data System (ADS)

    Zhelavskaya, I. S.; Spasojevic, M.; Shprits, Y.

    2015-12-01

    In this study we present an algorithm for automatic inference of the electron number density from plasma wave measurement made onboard NASA's Van Allen Probes mission. It accomplishes this by using feedforward neural networks to automatically infer the upper hybrid resonance frequency, 𝑓𝑢h𝑟, from plasma wave measurement, which is then used to determine the electron number density. In previous missions, the plasma resonance bands were manually identified, and there have been few attempts to do robust, routine automated detection (Kurth et al. [JGR, 2014]). We describe the design and implementation of the algorithm, as well as the resulting electron number density distribution. Resulting densities are compared with the densities obtained by Kurth et al. [JGR, 2014] and also to the empirical plasmasphere and trough density model of Sheeley et al. [JGR, 2001]. The analysis of the conditions, under which densities obtained by the proposed method differ significantly from the model of Sheeley et al. [JGR, 2001], is presented. Finally, we discuss the dependence of the electron number density on magnetic activity (Kp) and magnetic local time.

  15. Simultaneous measurement of core electron temperature and density fluctuations during electron cyclotron heating on DIII-D

    SciTech Connect

    White, A. E.; Schmitz, L.; Peebles, W. A.; Rhodes, T. L.; Carter, T. A.; McKee, G. R.; Shafer, M. W.; Staebler, G. M.; Burrell, K. H.; DeBoo, J. C.; Prater, R.

    2010-02-15

    New measurements show that long-wavelength (k{sub t}hetarho{sub s}<0.5) electron temperature fluctuations can play an important role in determining electron thermal transport in low-confinement mode (L-mode) tokamak plasmas. In neutral beam-heated L-mode tokamak plasmas, electron thermal transport and the amplitude of long-wavelength electron temperature fluctuations both increase in cases where local electron cyclotron heating (ECH) is used to modify the plasma profiles. In contrast, the amplitude of simultaneously measured long-wavelength density fluctuations does not significantly increase. Linear stability analysis indicates that the ratio of the trapped electron mode (TEM) to ion temperature gradient (ITG) mode growth rates increases in the cases with ECH. The increased importance of the TEM drive relative to the ITG mode drive in the cases with ECH may be associated with the increases in electron thermal transport and electron temperature fluctuations.

  16. Two-Dimensional Electron Density Measurement of Positive Streamer Discharge in Atmospheric-Pressure Air

    NASA Astrophysics Data System (ADS)

    Inada, Yuki; Ono, Ryo; Kumada, Akiko; Hidaka, Kunihiko; Maeyama, Mitsuaki

    2016-09-01

    The electron density of streamer discharges propagating in atmospheric-pressure air is crucially important for systematic understanding of the production mechanisms of reactive species utilized in wide ranging applications such as medical treatment, plasma-assisted ignition and combustion, ozone production and environmental pollutant processing. However, electron density measurement during the propagation of the atmospheric-pressure streamers is extremely difficult by using the conventional localized type measurement systems due to the streamer initiation jitters and the irreproducibility in the discharge paths. In order to overcome the difficulties, single-shot two-dimensional electron density measurement was conducted by using a Shack-Hartmann type laser wavefront sensor. The Shack-Hartmann sensor with a temporal resolution of 2 ns was applied to pulsed positive streamer discharges generated in an air gap between pin-to-plate electrodes. The electron density a few ns after the streamer initiation was 7*1021m-3 and uniformly distributed along the streamer channel. The electron density and its distribution profile were compared with a previous study simulating similar streamers, demonstrating good agreement. This work was supported in part by JKA and its promotion funds from KEIRIN RACE. The authors like to thank Mr. Kazuaki Ogura and Mr. Kaiho Aono of The University of Tokyo for their support during this work.

  17. Measurements of the Electron Cloud Density in the PEP-II Low Energy Ring

    SciTech Connect

    Byrd, J.; De Santis, S.; Sonnad, K.; Caspers, F.; Kroyer, T.; Krasnykh, A.; Pivi, M.; /SLAC

    2012-04-10

    Clouds of low energy electrons in the vacuum beam pipes of accelerators of positively charged particle beams present a serious limitation for operation of these machines at high currents. Because of the size of these accelerators, it is difficult to probe the low energy electron clouds over substantial lengths of the beam pipe. We have developed a novel technique to directly measure the electron cloud density via the phase shift induced in a TE wave that is independently excited and transmitted over a section of the accelerator. We infer the absolute phase shift with relatively high accuracy from the phase modulation of the transmission due to the modulation of the electron cloud density from a gap in the positively charged beam. We have used this technique for the first time to measure the average electron cloud density over a 50 m straight section in the positron ring of the PEP-II collider at the Stanford Linear Accelerator Center. We have also measured the variation of the density by using low field solenoid magnets to control the electrons.

  18. Electron Temperature and Density Measurements by the Unicity of Particle Confinement Time on the TCABR Tokamak

    SciTech Connect

    Machida, M.; Nascimento, I. C.; Severo, J. H. F.; Sanada, E. K.; Galvao, R. M. O.; Daltrini, A. M.

    2006-12-04

    The electron temperature Te and density ne at inner border side of plasma on TCABR tokamak are determined using the unicity of particle confinement time {tau}p. In this method, the signals from hydrogen Balmer series emissions like H alfa, beta and gama are measured with an absolutely intensity calibrated spectrometer during the discharge and the particle confinement time then is evaluated using these three emissions for large range of electron temperature and density, until the unique value of {tau}p is achieved. The results show that during the current plateau, the values of the edge electron density and temperature in high fill density discharge, present much strong variations compared to the low fill pressure because of larger edge turbulence activity.

  19. Real time two-dimensional spatial distribution measurement method of electron temperature and plasma density

    NASA Astrophysics Data System (ADS)

    Kim, Young Cheol; Jang, Sung Ho; Kim, Gun Ho; Chung, Chin Wook

    2009-10-01

    Real time two-dimensional spatial distribution measurement method of electron temperature and plasma density was developed. It is based on a floating probe method [1] because the floating probe has high time resolution. Two-dimensional array of sensors on a 300 mm diameter wafer-shaped printed circuit board (PCB) and a high speed multiplexer circuit were used for real time distribution measurement. The method was tested at various powers and pressures, spatial distributions of the electron temperature and the plasma density could be obtained. And in the measurement results, asymmetric plasma density distributions caused by pumping port effect could be observed. This method can measure spatial distribution of plasma parameters on the wafer in real time without plasma perturbation, therefore it will be expected to improve the uniformity of processing plasmas such as etching and deposition. [4pt] [1] M. H. Lee, S. H. Jang, C. W. Chung, J. Appl. Phys. 101, 033305 (2007).

  20. Measuring the Density of a Molecular Cluster Injector via Visible Emission from an Electron Beam

    SciTech Connect

    Lundberg, D. P.; Kaita, R.; Majeski, R. M.; Stotler, D. P.

    2010-06-28

    A method to measure the density distribution of a dense hydrogen gas jet is pre- sented. A Mach 5.5 nozzle is cooled to 80K to form a flow capable of molecular cluster formation. A 250V, 10mA electron beam collides with the jet and produces Hα emission that is viewed by a fast camera. The high density of the jet, several 1016cm-3, results in substantial electron depletion, which attenuates the Hα emission. The attenuated emission measurement, combined with a simplified electron-molecule collision model, allows us to determine the molecular density profile via a simple iterative calculation.

  1. Partial-reflection studies of D-region winter variability. [electron density measurements

    NASA Technical Reports Server (NTRS)

    Denny, B. W.; Bowhill, S. A.

    1973-01-01

    D-region electron densities were measured from December, 1972, to July, 1973, at Urbana, Illinois (latitude 40.2N) using the partial-reflection technique. During the winter, electron densities at altitudes of 72, 76.5, and 81 km show cyclical changes with a period of about 5 days that are highly correlated between these altitudes, suggesting that the mechanism responsible for the winter anomaly in D-region ionization applies throughout this height region. From January 13 to February 3, a pronounced wave-like variation occurred in the partial-reflection measurements, apparently associated with a major stratospheric warming that developed in that period. During the same time period, a traveling periodic variation is observed in the 10-mb height; it is highly correlated with the partial-reflection measurements. Electron density enhancements occur approximately at the same time as increases in the 10-mb height. Comparison of AL and A3 absorption measurements with electron density measurements below 82 km indicates that the winter anomaly in D-region ionization is divided into two types. Type 1, above about 82 km, extends horizontally for about 200 km while type 2, below about 82 km, extends for a horizontal scale of at least 1000 km.

  2. Radial Electron Temperature and Density Measurements Using Thomson Scattering System in GAMMA 10/PDX

    NASA Astrophysics Data System (ADS)

    Yoshikawa, M.; Ohta, K.; Wang, X.; Chikatsu, M.; Kohagura, J.; Shima, Y.; Sakamoto, M.; Imai, T.; Nakashima, Y.; Yasuhara, R.; Yamada, I.; Funaba, H.; Minami, T.

    2015-11-01

    A Thomson scattering (TS) system in GAMMA 10/PDX has been developed for the measurement of radial profiles of electron temperature and density in a single plasma and laser shot. The TS system has a large solid angle optical collection system and high-sensitivity signal detection system. The TS signals are obtained using four-channel high-speed digital oscilloscopes controlled by a Windows PC. We designed the acquisition program for six oscilloscopes to obtain 10-Hz TS signals in a single plasma shot, following which the time-dependent electron temperatures and densities can be determined. Moreover, in order to obtain larger TS signal intensity in the edge region, we added a second collection mirror. The radial electron temperatures and densities at six radial positions in GAMMA 10/PDX were successfully obtained.

  3. 2D electron density profile measurement in tokamak by laser-accelerated ion-beam probe

    SciTech Connect

    Chen, Y. H.; Yang, X. Y.; Lin, C. E-mail: cjxiao@pku.edu.cn; Wang, X. G.; Xiao, C. J. E-mail: cjxiao@pku.edu.cn; Wang, L.; Xu, M.

    2014-11-15

    A new concept of Heavy Ion Beam Probe (HIBP) diagnostic has been proposed, of which the key is to replace the electrostatic accelerator of traditional HIBP by a laser-driven ion accelerator. Due to the large energy spread of ions, the laser-accelerated HIBP can measure the two-dimensional (2D) electron density profile of tokamak plasma. In a preliminary simulation, a 2D density profile was reconstructed with a spatial resolution of about 2 cm, and with the error below 15% in the core region. Diagnostics of 2D density fluctuation is also discussed.

  4. Measurement of electron density transients in pulsed RF discharges using a frequency boxcar hairpin probe

    NASA Astrophysics Data System (ADS)

    Peterson, David; Coumou, David; Shannon, Steven

    2015-11-01

    Time resolved electron density measurements in pulsed RF discharges are shown using a hairpin resonance probe using low cost electronics, on par with normal Langmuir probe boxcar mode operation. Time resolution of 10 microseconds has been demonstrated. A signal generator produces the applied microwave frequency; the reflected waveform is passed through a directional coupler and filtered to remove the RF component. The signal is heterodyned with a frequency mixer and rectified to produce a DC signal read by an oscilloscope. At certain points during the pulse, the plasma density is such that the applied frequency is the same as the resonance frequency of the probe/plasma system, creating reflected signal dips. The applied microwave frequency is shifted in small increments in a frequency boxcar routine to determine the density as a function of time. A dc sheath correction is applied for the grounded probe, producing low cost, high fidelity, and highly reproducible electron density measurements. The measurements are made in both inductively and capacitively coupled systems, the latter driven by multiple frequencies where a subset of these frequencies are pulsed. Measurements are compared to previous published results, time resolved OES, and in-line measurement of plasma impedance. This work is supported by the NSF DOE partnership on plasma science, the NSF GOALI program, and MKS Instruments.

  5. Real-time electron density measurements from Cotton-Mouton effect in JET machine

    SciTech Connect

    Brombin, M.; Boboc, A.; Zabeo, L.

    2008-10-15

    Real-time density profile measurements are essential for advanced fusion tokamak operation and interferometry is a proven method for this task. Nevertheless, as a consequence of edge localized modes, pellet injections, fast density increases, or disruptions, the interferometer is subject to fringe jumps, which produce loss of the signal preventing reliable use of the measured density in a real-time feedback controller. An alternative method to measure the density is polarimetry based on the Cotton-Mouton effect, which is proportional to the line-integrated electron density. A new analysis approach has been implemented and tested to verify the reliability of the Cotton-Mouton measurements for a wide range of plasma parameters and to compare the density evaluated from polarimetry with that from interferometry. The density measurements based on polarimetry are going to be integrated in the real-time control system of JET since the difference with the interferometry is within one fringe for more than 90% of the cases.

  6. Real-time electron density measurements from Cotton-Mouton effect in JET machine.

    PubMed

    Brombin, M; Boboc, A; Zabeo, L; Murari, A

    2008-10-01

    Real-time density profile measurements are essential for advanced fusion tokamak operation and interferometry is a proven method for this task. Nevertheless, as a consequence of edge localized modes, pellet injections, fast density increases, or disruptions, the interferometer is subject to fringe jumps, which produce loss of the signal preventing reliable use of the measured density in a real-time feedback controller. An alternative method to measure the density is polarimetry based on the Cotton-Mouton effect, which is proportional to the line-integrated electron density. A new analysis approach has been implemented and tested to verify the reliability of the Cotton-Mouton measurements for a wide range of plasma parameters and to compare the density evaluated from polarimetry with that from interferometry. The density measurements based on polarimetry are going to be integrated in the real-time control system of JET since the difference with the interferometry is within one fringe for more than 90% of the cases.

  7. Validation of ISS Floating Potential Measurement Unit Electron Densities and Temperatures

    NASA Technical Reports Server (NTRS)

    Coffey, Victoria N.; Minow, Joseph I.; Parker, Linda N.; Bui, Them; Wright, Kenneth, Jr.; Koontz, Steven L.; Schneider, T.; Vaughn, J.; Craven, P.

    2007-01-01

    Validation of the Floating Potential Measurement Unit (FPMU) electron density and temperature measurements is an important step in the process of evaluating International Space Station spacecraft charging issues .including vehicle arcing and hazards to crew during extravehicular activities. The highest potentials observed on Space Station are due to the combined VxB effects on a large spacecraft and the collection of ionospheric electron and ion currents by the 160 V US solar array modules. Ionospheric electron environments are needed for input to the ISS spacecraft charging models used to predict the severity and frequency of occurrence of ISS charging hazards. Validation of these charging models requires comparing their predictions with measured FPMU values. Of course, the FPMU measurements themselves must also be validated independently for use in manned flight safety work. This presentation compares electron density and temperatures derived from the FPMU Langmuir probes and Plasma Impedance Probe against the independent density and temperature measurements from ultraviolet imagers, ground based incoherent scatter radar, and ionosonde sites.

  8. Measurement of electron temperature and density in an argon microdischarge by laser Thomson scattering

    NASA Astrophysics Data System (ADS)

    Belostotskiy, Sergey G.; Khandelwal, Rahul; Wang, Qiang; Donnelly, Vincent M.; Economou, Demetre J.; Sadeghi, Nader

    2008-06-01

    Laser Thomson scattering in a novel, backscattered configuration was employed to measure the electron temperature (Te) and electron density (ne) in argon dc microdischarges, with an interelectrode gap of 600μm. Measurements were performed at the center of the gap that corresponds to the positive column. For 50mA microdischarge current and over the pressure range of 300-700Torr, the plasma parameters were found to be Te=0.9±0.3eV and ne=(6±3)×1013cm-3, in reasonable agreement with the predictions of a mathematical model.

  9. A study of density measurements in hypersonic helium tunnels using an electron beam fluorescence technique

    NASA Technical Reports Server (NTRS)

    Honaker, W. C.; Hunter, W. W., Jr.; Woods, W. C.

    1979-01-01

    A series of experiments have been conducted at Langley Research Center to determine the feasibility of using electron-beam fluorescence to measure the free-stream static density of gaseous helium flow over a wide range of conditions. These experiments were conducted in the Langley hypersonic helium tunnel facility and its 3-inch prototype. Measurements were made for a range of stagnation pressures and temperatures and produced free-stream number densities of 1.53 x 10 to the 23rd to 1.25 x 10 to the 24th molecules/cu m and static temperatures from 2 K to 80 K. The results showed the collision quenching cross section to be 4.4 x 10 to the -15th sq cm at 1 K and to have a weak temperature dependence of T to the 1/6. With knowledge of these two values, the free-stream number density can be measured quite accurately.

  10. Finite grid radius and thickness effects on retarding potential analyzer measured suprathermal electron density and temperature

    NASA Technical Reports Server (NTRS)

    Knudsen, William C.

    1992-01-01

    The effect of finite grid radius and thickness on the electron current measured by planar retarding potential analyzers (RPAs) is analyzed numerically. Depending on the plasma environment, the current is significantly reduced below that which is calculated using a theoretical equation derived for an idealized RPA having grids with infinite radius and vanishingly small thickness. A correction factor to the idealized theoretical equation is derived for the Pioneer Venus (PV) orbiter RPA (ORPA) for electron gasses consisting of one or more components obeying Maxwell statistics. The error in density and temperature of Maxwellian electron distributions previously derived from ORPA data using the theoretical expression for the idealized ORPA is evaluated by comparing the densities and temperatures derived from a sample of PV ORPA data using the theoretical expression with and without the correction factor.

  11. A Method to Improve Electron Density Measurement of Cone-Beam CT Using Dual Energy Technique

    PubMed Central

    Men, Kuo; Dai, Jian-Rong; Li, Ming-Hui; Chen, Xin-Yuan; Zhang, Ke; Tian, Yuan; Huang, Peng; Xu, Ying-Jie

    2015-01-01

    Purpose. To develop a dual energy imaging method to improve the accuracy of electron density measurement with a cone-beam CT (CBCT) device. Materials and Methods. The imaging system is the XVI CBCT system on Elekta Synergy linac. Projection data were acquired with the high and low energy X-ray, respectively, to set up a basis material decomposition model. Virtual phantom simulation and phantoms experiments were carried out for quantitative evaluation of the method. Phantoms were also scanned twice with the high and low energy X-ray, respectively. The data were decomposed into projections of the two basis material coefficients according to the model set up earlier. The two sets of decomposed projections were used to reconstruct CBCT images of the basis material coefficients. Then, the images of electron densities were calculated with these CBCT images. Results. The difference between the calculated and theoretical values was within 2% and the correlation coefficient of them was about 1.0. The dual energy imaging method obtained more accurate electron density values and reduced the beam hardening artifacts obviously. Conclusion. A novel dual energy CBCT imaging method to calculate the electron densities was developed. It can acquire more accurate values and provide a platform potentially for dose calculation. PMID:26346510

  12. Electron density measurements in very electronegative plasmas using different diagnostic techniques: theory and experiments

    NASA Astrophysics Data System (ADS)

    Rafalskyi, Dmytro; Lafleur, Trevor; Aanesland, Ane

    2016-09-01

    Very electronegative plasmas (known as ``ion-ion'' plasmas) are used in different applications including material processing, space propulsion and thermonuclear fusion. Diagnostics of ion-ion plasmas can be performed using different probe techniques, including Langmuir and hairpin probes, RF, microwave and optical diagnostics. However, in certain applications (for example, in the electronegative thruster PEGASES), the electron density is too low (<1012m-3) to be reliably measured by these standard techniques. This is further complicated by the presence of strong, non-homogeneous, magnetic fields in the plasma ( 200 G) and the relatively small plasma size (few cm). In this work we compare results achieved with a Langmuir probe, and with an independent measurement of the electron density using a matched dipole probe. Measurements are performed in an SF6 plasma with an electronegativity in the range between a few hundred to a few thousand. We show here that though the model itself can correctly describe the plasma-probe interactions, there is a critical value of plasma electronegativity above which the electron density measured with a Langmuir probe can give only an upper limit estimation.

  13. Diagnostics principle of microwave cut-off probe for measuring absolute electron density

    SciTech Connect

    Jun, Hyun-Su

    2014-08-15

    A generalized diagnostics principle of microwave cut-off probe is presented with a full analytical solution. In previous studies on the microwave cut-off measurement of weakly ionized plasmas, the cut-off frequency ω{sub c} of a given electron density is assumed to be equal to the plasma frequency ω{sub p} and is predicted using electromagnetic simulation or electric circuit model analysis. However, for specific plasma conditions such as highly collisional plasma and a very narrow probe tip gap, it has been found that ω{sub c} and ω{sub p} are not equal. To resolve this problem, a generalized diagnostics principle is proposed by analytically solving the microwave cut-off condition Re[ε{sub r,eff}(ω = ω{sub c})] = 0. In addition, characteristics of the microwave cut-off condition are theoretically tested for correct measurement of the absolute electron density.

  14. Simultaneous streak and frame interferometry for electron density measurements of laser produced plasmas

    SciTech Connect

    Quevedo, H. J. McCormick, M.; Wisher, M.; Bengtson, Roger D.; Ditmire, T.

    2016-01-15

    A system of two collinear probe beams with different wavelengths and pulse durations was used to capture simultaneously snapshot interferograms and streaked interferograms of laser produced plasmas. The snapshots measured the two dimensional, path-integrated, electron density on a charge-coupled device while the radial temporal evolution of a one dimensional plasma slice was recorded by a streak camera. This dual-probe combination allowed us to select plasmas that were uniform and axisymmetric along the laser direction suitable for retrieving the continuous evolution of the radial electron density of homogeneous plasmas. Demonstration of this double probe system was done by measuring rapidly evolving plasmas on time scales less than 1 ns produced by the interaction of femtosecond, high intensity, laser pulses with argon gas clusters. Experiments aimed at studying homogeneous plasmas from high intensity laser-gas or laser-cluster interaction could benefit from the use of this probing scheme.

  15. Electron density profile measurements from hydrogen line intensity ratio method in Versatile Experiment Spherical Torus

    NASA Astrophysics Data System (ADS)

    Kim, YooSung; Shi, Yue-Jiang; Yang, Jeong-hun; Kim, SeongCheol; Kim, Young-Gi; Dang, Jeong-Jeung; Yang, Seongmoo; Jo, Jungmin; Oh, Soo-Ghee; Chung, Kyoung-Jae; Hwang, Y. S.

    2016-11-01

    Electron density profiles of versatile experiment spherical torus plasmas are measured by using a hydrogen line intensity ratio method. A fast-frame visible camera with appropriate bandpass filters is used to detect images of Balmer line intensities. The unique optical system makes it possible to take images of Hα and Hβ radiation simultaneously, with only one camera. The frame rate is 1000 fps and the spatial resolution of the system is about 0.5 cm. One-dimensional local emissivity profiles have been obtained from the toroidal line of sight with viewing dumps. An initial result for the electron density profile is presented and is in reasonable agreement with values measured by a triple Langmuir probe.

  16. Development of far infrared attenuation to measure electron densities in cw pin discharge lasers

    NASA Technical Reports Server (NTRS)

    Babcock, R. V.

    1977-01-01

    A two beam attenuation technique was devised to measure electron densities 10 to the 9th power to 10 to the 11th power cm/3 resolved to 1 cm, in a near atmospheric COFFEE laser discharge, using 496 micrometer and 1,220 micrometer radiations from CH3F, optically pumped by a CO2 laser. A far infrared generator was developed which was suitable except for a periodic intensity variation in FIR output deriving from frequency variation of the pump radiation.

  17. Local ionospheric electron density reconstruction from simultaneous ground-based GNSS and ionosonde measurements

    NASA Astrophysics Data System (ADS)

    Stankov, S. M.; Warnant, R.; Stegen, K.

    2009-04-01

    The purpose of the LIEDR (Local Ionospheric Electron Density Reconstruction) system is to acquire and process data from simultaneous ground-based GNSS TEC and digital ionosonde measurements, and subsequently to deduce the vertical electron density distribution in the local ionosphere. LIEDR is primarily designed to operate in real time for service applications, and, if sufficient data from solar and geomagnetic observations are available, to provide short-term forecast as well. For research applications and further development of the system, a post-processing mode of operation is also envisaged. In essence, the reconstruction procedure consists in the following. The high-precision ionosonde measurements are used for directly obtaining the bottom part of the electron density profile. The ionospheric profiler for the lower side (i.e. below the density peak height, hmF2) is based on the Epstein layer functions using the known values of the critical frequencies, foF2 and foE, and the propagation factor, M3000F2. The corresponding bottom-side part of the total electron content is calculated from this profile and is then subtracted from the GPS TEC value in order to obtain the unknown portion of the TEC in the upper side (i.e. above the hmF2). Ionosonde data, together with the simultaneously-measured TEC and empirically obtained O+/H+ ion transition level values, are all required for the determination of the topside electron density scale height. The topside electron density is considered as a sum of the constituent oxygen and hydrogen ion densities with unknown vertical scale heights. The latter are calculated by solving a system of transcendental equations that arise from the incorporation of a suitable ionospheric profiler (Chapman, Epstein, or Exponential) into formulae describing ionospheric conditions (plasma quasi-neutrality, ion transition level). Once the topside scale heights are determined, the construction of the vertical electron density distribution in the

  18. Two color interferometric electron density measurement in an axially blown arc

    NASA Astrophysics Data System (ADS)

    Stoller, Patrick; Carstensen, Jan; Galletti, Bernardo; Doiron, Charles; Sokolov, Alexey; Salzmann, René; Simon, Sandor; Jabs, Philipp

    2016-09-01

    High voltage circuit breakers protect the power grid by interrupting the current in case of a short circuit. To do so an arc is ignited between two contacts as they separate; transonic gas flow is used to cool and ultimately extinguish the arc at a current-zero crossing of the alternating current. A detailed understanding of the arc interruption process is needed to improve circuit breaker design. The conductivity of the partially ionized gas remaining after the current-zero crossing, a key parameter in determining whether the arc will be interrupted or not, is a function of the electron density. The electron density, in turn, is a function of the detailed dynamics of the arc cooling process, which does not necessarily occur under local thermodynamic equilibrium (LTE) conditions. In this work, we measure the spatially resolved line-integrated index of refraction in a near-current-zero arc stabilized in an axial flow of synthetic air with two nanosecond pulsed lasers at wavelengths of 532 nm and 671 nm. Generating a stable, cylindrically symmetric arc enables us to determine the three-dimensional index of refraction distribution using Abel inversion. Due to the wavelength dependence of the component of the index of refraction related to the free electrons, the information at two different wavelengths can be used to determine the electron density. This information allows us to determine how important it is to take into account non-equilibrium effects for accurate modeling of the physics of decaying arcs.

  19. Temperature and density measurement by electron beam fluorescence technique in rocket experiment

    NASA Astrophysics Data System (ADS)

    Kurihara, J.; Oyama, K.-I.

    The Electron Beam Fluorescence (EBF) technique has been widely used in the field of rarefied gas dynamics for over 40 years and applied to measurements for a variety of gases and flow conditions in the laboratory experiment. The EBF technique uses a high-energy electron beam to excite a gas molecule by an inelastic collision with an electron. Spectrum of subsequent fluorescence by the excited molecule consists of many vibrational bands, and each band has a fine rotational structure. If the excitation-emission process is known precisely, the analysis of the vibrational-rotational band provides properties of the initial state of molecules. We applied the EBF technique to an in-situ measurement in the lower thermosphere and the vibrational temperature, the rotational temperature, and the number density of atmospheric molecular nitrogen between 100 - 150 km altitudes were observed by the sounding rocket experiment. Aerodynamic effects on the measurement caused by the rocket flight are corrected quantitatively using Direct Simulation Monte Carlo (DSMC) method. The great advantage of this type of instrument is that temperature and density are observed simultaneously and the consistency between the two measurements can be checked assuming hydrostatic equilibrium.

  20. Computational characterization of cutoff probe system for the measurement of electron density

    SciTech Connect

    Na, Byung-Keun; Kim, Dae-Woong; Kwon, Jun-Hyuk; Chang, Hong-Young; Kim, Jung-Hyung; You, Shin-Jae

    2012-05-15

    The wave cutoff probe, a precise measurement method for measuring the electron density, was recently proposed. To characterize the cutoff probe system, in this paper, the microwave simulations of a cutoff probe system were performed at various configurations of the cutoff probe system. The influence of the cutoff probe spectrum stemming from numerous parametric elements such as the probe tip length, probe tip distance, probe tip plane orientation, chamber volume/geometry, and coaxial cable length is presented and discussed. This article is expected to provide qualitative and quantitative insight into cutoff probe systems and its optimization process.

  1. Electron Density Measurements on LTX Using Microwave and Millimeter-Wave Diagnostics

    NASA Astrophysics Data System (ADS)

    Kubota, S.; Nguyen, X. V.; Peebles, W. A.; Boyle, D. P.; Kaita, R.; Kozub, T.; Majeski, R.; Merino, E.; Schmitt, J. C.

    2015-11-01

    The dynamic evolution of the electron density profile is tracked using microwave and millimeter-wave diagnostics on LTX. The 296 GHz (λ =1 mm) interferometer provides a radial line density measurement at the midplane, while an FMCW (frequency-modulated continuous-wave) reflectometer (13.5 -33 GHz, or O-mode 0 . 2 - 1 . 3 ×1013 cm-3) provides density profile measurements for the low-field side. Data taken during FY2015 will be compared with measurements from Thomson scattering and estimates of the plasma position from LRDFIT. Measurements of density fluctuations due to low-frequency (<100 kHz) MHD instabilities will also be shown. Future plans include the installation of a correlation reflectomter (Ka-band, 27-40 GHz) with dual tuneable sources and a frequency bandwidth of up to 5 MHz. This system will utilize the same antennas as the profile reflectometer to provide radial and/or toroidal/poloidal correlations. Further diagnostic details will be presented at the meeting. Supported by U.S. DoE Grants DE-FG02-99ER54527 and DE-AC02-09CH11466.

  2. Development and Miniaturization of RF based probes for Electron Density Measurements

    NASA Astrophysics Data System (ADS)

    Nakamura, Keiji

    2016-09-01

    To make a diagnostics on plasmas for materials processing plasmas accompanying with deposition of non-conducting films in etching and/or CVD processes, curling probe (CP) with a spiral slot antenna has been recently developed as a compact diagnostic tool which enables the local electron density measurement. The electron density is obtained from a shift of the probe resonance frequency in discharge ON and OFF monitored by a network analyzer (NWA). A conventional CP has a diameter larger than 15 mm typically, because a slot length of the CP is as long as several tens millimeters for its resonance frequency less than several GHz. Further miniaturization of the CP was required to expand applicable range to various plasma sources like a narrow-gap parallel plate discharge. We tried miniaturization of the CP down to less than 3 mm in the probe diameter by fabricating narrow spiral slot antenna, and experimentally and numerically the miniaturized probe was investigated how much influence the slot width has on probe resonance characteristics and electron density measurements. In the case of the conventional CP made of stainless steel, 0.3-mm-wide normal slot antenna, the resonance spectra was clearly observed regardless of antenna materials of copper or stainless steel (SS). However, when the slot width was reduced down to 0.03 mm, the slot resonance was strongly dependent on the antenna materials. Namely the resonance peak was almost vanished for the SS antenna, whereas clearly appeared for the copper antenna. In general, the narrower the slot is, the higher attenuation factor the slot has for electromagnetic wave propagating along the slot. In such an attenuated transmission line of the narrow slot, high electric conductivity of the antenna seems preferable for the slot resonance. Furthermore, the miniaturized CP with the copper antenna was also introduced into low pressure (< 1Pa) Ar plasma. The resonance frequency was confirmed to changes sensitively with electron

  3. Matched dipole probe for precise electron density measurements in magnetized and non-magnetized plasmas

    NASA Astrophysics Data System (ADS)

    Rafalskyi, Dmytro; Aanesland, Ane

    2015-09-01

    We present a plasma diagnostics method based on impedance measurements of a short matched dipole placed in the plasma. This allows measuring the local electron density in the range from 1012-1015 m-3 with a magnetic field of at least 0-50 mT. The magnetic field strength is not directly influencing the data analysis and requires only that the dipole probe is oriented perpendicularly to the magnetic field. As a result, the magnetic field can be non-homogeneous or even non-defined within the probe length without any effect on the final tolerance of the measurements. The method can be applied to plasmas of relatively small dimensions (< 10 cm) and doesn't require any special boundary conditions. The high sensitivity of the impedance measurements is achieved by using a miniature matching system installed close to the probe tip, which also allows to suppress sheath resonance effects. We experimentally show here that the tolerance of the electron density measurements reaches values lower than 1%, both with and without the magnetic field. The method is successfully validated by both analytical modeling and experimental comparison with Langmuir probes. The validation experiments are conducted in a low pressure (1 mTorr) Ar discharge sustained in a 10 cm size plasma chamber with and without a transversal magnetic field of about 20 mT. This work was supported by a Marie Curie International Incoming Fellowships within FP7 (NEPTUNE PIIF-GA-2012-326054).

  4. Microwave techniques for electron density measurements in low pressure RF plasmas

    NASA Astrophysics Data System (ADS)

    Zheltukhin, Viktor; Gafarov, Ildar; Shemakhin, Alexander

    2016-09-01

    Results of the experimental studying of RF plasma jet at low pressure in the range of 10 - 300 Pa is presented. The electron density distribution both in inductive and in capacitive coupled RF discharges was measured at 1.76 MHz and 13.56 MHz consequently. We used three independent microwave diagnostic techniques such as free space (the ``two-frequency'' and ``on the cut-off signal'') and a resonator. It is found that the electron density in the RF plasma jets is by 1-2 orders of magnitude greater than in the decaying plasma jet, and by 1-2 orders of magnitude less than in the RF plasma torch. Thus the RF plasma jet is similar to the additional discharge between the electrodes or the coil and the vacuum chamber walls. As a consequence, the formation of the positive charge sheath near the specimen placed in plasma stream is observed. It is found that the maximum of ionization degree as well as more uniform electron density distribution across the stream is observed in the range of the gas flow rate Gg = 0 . 06 - 0 . 12 g/s and the discharge power Pd = 0 . 5 - 2 . 5 kW. The work was funded by RFBR, according to the research projects No. 16-31-60081 mol_a_dk.

  5. Weak-beam scanning transmission electron microscopy for quantitative dislocation density measurement in steels.

    PubMed

    Yoshida, Kenta; Shimodaira, Masaki; Toyama, Takeshi; Shimizu, Yasuo; Inoue, Koji; Yoshiie, Toshimasa; Milan, Konstantinovic J; Gerard, Robert; Nagai, Yasuyoshi

    2017-01-17

    To evaluate dislocations induced by neutron irradiation, we developed a weak-beam scanning transmission electron microscopy (WB-STEM) system by installing a novel beam selector, an annular detector, a high-speed CCD camera and an imaging filter in the camera chamber of a spherical aberration-corrected transmission electron microscope. The capabilities of the WB-STEM with respect to wide-view imaging, real-time diffraction monitoring and multi-contrast imaging are demonstrated using typical reactor pressure vessel steel that had been used in an European nuclear reactor for 30 years as a surveillance test piece with a fluence of 1.09 × 10(20) neutrons cm(-)(2) The quantitatively measured size distribution (average loop size = 3.6 ± 2.1 nm), number density of the dislocation loops (3.6 × 10(22) m(-3)) and dislocation density (7.8 × 10(13) m m(-)(3)) were carefully compared with the values obtained via conventional weak-beam transmission electron microscopy studies. In addition, cluster analysis using atom probe tomography (APT) further demonstrated the potential of the WB-STEM for correlative electron tomography/APT experiments.

  6. Data-driven sensitivity inference for Thomson scattering electron density measurement systems

    NASA Astrophysics Data System (ADS)

    Fujii, Keisuke; Yamada, Ichihiro; Hasuo, Masahiro

    2017-01-01

    We developed a method to infer the calibration parameters of multichannel measurement systems, such as channel variations of sensitivity and noise amplitude, from experimental data. We regard such uncertainties of the calibration parameters as dependent noise. The statistical properties of the dependent noise and that of the latent functions were modeled and implemented in the Gaussian process kernel. Based on their statistical difference, both parameters were inferred from the data. We applied this method to the electron density measurement system by Thomson scattering for the Large Helical Device plasma, which is equipped with 141 spatial channels. Based on the 210 sets of experimental data, we evaluated the correction factor of the sensitivity and noise amplitude for each channel. The correction factor varies by ≈10%, and the random noise amplitude is ≈2%, i.e., the measurement accuracy increases by a factor of 5 after this sensitivity correction. The certainty improvement in the spatial derivative inference was demonstrated.

  7. Plasma Core Electron Density and Temperature Measurements Using CVI Line Emissions in TCABR Tokamak

    NASA Astrophysics Data System (ADS)

    do Nascimento, F.; Machida, M.; Severo, J. H. F.; Sanada, E.; Ronchi, G.

    2015-08-01

    In this work, we present results of electron temperature ( T e ) and density ( n e ) measurements obtained in Tokamak Chauffage Alfvén Brésilien (TCABR) tokamak using visible spectroscopy from CVI line emissions which occurs mainly near the center of the plasma column. The presented method is based on a well-known relationship between the particle flux ( Γ ion) and the photon flux ( ø ion) emitted by an ion species combined with ionizations per photon atomic data provided by the atomic data and analysis structure (ADAS) database. In the experiment, we measured the photon fluxes of three different CVI spectral line emissions, 4685.2, 5290.5, and 6200.6 Å (one line per shot). Using this method it was possible to find out the temporal evolution of T e and n e in the plasma. The results achieved are in good agreement with T e and n e measurements made using other diagnostic tools.

  8. Measurement of solar wind electron density and temperature in the shocked region of Venus and the density and temperature of photoelectrons within the ionosphere of Venus

    NASA Astrophysics Data System (ADS)

    Knudsen, William C.; Jones, Douglas E.; Peterson, Bryan G.; Knadler, Charles E.

    2016-08-01

    Presented herein are measurements of the solar wind electron number density and temperature near and within the bow shock of Venus. The measurements were made by the Pioneer Venus mission Orbiter Retarding Potential Analyzer operating in its suprathermal electron mode. The measurements are essentially point measurements. The spacecraft travels approximately 0.8 km during the 0.1 s time interval required to record a single I-V curve. The dual measurement of a density and temperature is obtained from one sweep by least squares fitting a mathematical Maxwellian expression to the I-V curve. The distance between successive measurements is approximately 100 km. In many orbits, when the spacecraft is crossing or traveling within the bow shock, the derived densities and temperatures (high density, high temperature (HDHT)) are large, densities of the order of 100 cm-3 and temperatures of the order of several hundred eV. We interpret these HDHT measurements as measurements in regions where the large, directed kinetic energy of the solar wind ions is being degraded into randomized, more thermal-like energy distributions of the electrons and ions through wave-particle interactions. The HDHT values define the electron energy distribution in the limited energy interval 0 to 50 eV. We assume that the underlying electron flux distributions are flat topped like those measured in the Earth's bow shock. We also report densities and temperatures of EUV produced photoelectron energy distributions measured within the ionosphere.

  9. Electron density profile measurements at a self-focusing ion beam with high current density and low energy extracted through concave electrodes

    SciTech Connect

    Fujiwara, Y. Nakamiya, A.; Sakakita, H.; Hirano, Y.; Kiyama, S.; Koguchi, H.

    2014-02-15

    The self-focusing phenomenon has been observed in a high current density and low energy ion beam. In order to study the mechanism of this phenomenon, a special designed double probe to measure the electron density and temperature is installed into the chamber where the high current density ion beam is injected. Electron density profile is successfully measured without the influence of the ion beam components. Estimated electron temperature and density are ∼0.9 eV and ∼8 × 10{sup 8} cm{sup −3} at the center of ion beam cross section, respectively. It was found that a large amount of electrons are spontaneously accumulated in the ion beam line in the case of self-forcing state.

  10. Measurements of mass attenuation coefficient, effective atomic number and electron density of some amino acids

    NASA Astrophysics Data System (ADS)

    Kore, Prashant S.; Pawar, Pravina P.

    2014-05-01

    The mass attenuation coefficients of some amino acids, such as DL-aspartic acid-LR(C4H7NO4), L-glutamine (C4H10N2O3), creatine monohydrate LR(C4H9N3O2H2O), creatinine hydrochloride (C4H7N3O·HCl) L-asparagine monohydrate(C4H9N3O2H2O), L-methionine LR(C5H11NO2S), were measured at 122, 356, 511, 662, 1170, 1275 and 1330 keV photon energies using a well-collimated narrow beam good geometry set-up. The gamma-rays were detected using NaI (Tl) scintillation detection system with a resolution of 0.101785 at 662 keV. The attenuation coefficient data were then used to obtain the effective atomic numbers (Zeff), and effective electron densities (Neff) of amino acids. It was observed that the effective atomic number (Zeff) and effective electron densities (Neff) initially decrease and tend to be almost constant as a function of gamma-ray energy. Zeff and Neff experimental values showed good agreement with the theoretical values with less than 1% error for amino acids.

  11. Magnetic field vector and electron density diagnostics from linear polarization measurements in 14 solar prominences

    NASA Technical Reports Server (NTRS)

    Bommier, V.

    1986-01-01

    The Hanle effect is the modification of the linear polarization parameters of a spectral line due to the effect of the magnetic field. It has been successfully applied to the magnetic field vector diagnostic in solar prominences. The magnetic field vector is determined by comparing the measured polarization to the polarization computed, taking into account all the polarizing and depolarizing processes in line formation and the depolarizing effect of the magnetic field. The method was applied to simultaneous polarization measurements in the Helium D3 line and in the hydrogen beta line in 14 prominences. Four polarization parameters are measured, which lead to the determination of the three coordinates of the magnetic field vector and the electron density, owing to the sensitivity of the hydrogen beta line to the non-negligible effect of depolarizing collisions with electrons and protons of the medium. A mean value of 1.3 x 10 to the 10th power cu. cm. is derived in 14 prominences.

  12. Evaluating the diffusive equilibrium models: Comparison with the IMAGE RPI field-aligned electron density measurements

    NASA Astrophysics Data System (ADS)

    Ozhogin, P.; Song, P.; Tu, J.; Reinisch, B. W.

    2014-06-01

    The diffusive equilibrium models that are widely used by the space physics community to describe the plasma densities in the plasmasphere are evaluated with field-aligned electron density measurements from the radio plasma imager (RPI) instrument onboard the IMAGE satellite. The original mathematical form of the diffusive equilibrium model was based on the hydrostatic equilibrium along the magnetic field line with the centrifugal force and the field-aligned electrostatic force as well as a large number of simplifying approximations. Six free parameters in the mathematical form have been conventionally determined from observations. We evaluate four sets of the parameters that have been reported in the literature. The evaluation is made according to the equatorial radial distance dependence, latitudinal dependence at a given radial distance, and the combined radial and latitudinal dependences. We find that the mathematical form given in the diffusive equilibrium model is intrinsically incompatible with the measurements unless another large number of free parameters are artificially introduced, which essentially changes the nature of a theoretical model to an empirical model.

  13. A global survey of COSMIC ionospheric peak electron density and its height: A comparison with ground-based ionosonde measurements

    NASA Astrophysics Data System (ADS)

    Chu, Yen-Hsyang; Su, Chin-Lung; Ko, Hsiao-Tsung

    2010-08-01

    With a network of ground-based ionosondes distributed around the world, the ionospheric peak electron density and its height measured by FORMOSAT-3/COSMIC satellites in terms of GPS radio occultation technique are extensively examined in this article. It is found that, in spite of the latitude, the mean values of the peak electron density measured by COSMIC satellites are systematically smaller than those observed by ground-based ionosondes. The discrepancy between them is dependent on the latitude, namely, it is small in low and mid-latitudes and large in high-latitude region. Moreover, statistical analysis shows that the slopes of the regression line that is best fitted to the scatter diagram of occultation-retrieved peak electron density (ordinate axis) versus ionosonde-observed peak density (abscissa axis) are universally less than one. This feature is believed to be the result of path average effect of non-uniform distribution of the electron density along the GSP ray during the occultation. A comparison between COSMIC-measured peak height and ionosonde-derived peak height hmF2 indicates that the former is systematically higher than the latter. The difference in the two can be as large as 20% or more in equatorial and low-latitude regions. This result implies that the peak height hmF2 derived from the virtual height through true height analysis based on Titheridge method seems to underestimate the true peak height. The correlation between COSMIC and ionosonde peak electron densities is analyzed and the result reveals that correlation coefficient seems to be dependent on the fluctuation of the occultation-retrieved electron density profile. The correlation will be higher (lower) for the electron density profiles with smaller (larger) fluctuations. This feature suggests that the inhomogeneous distribution of the electron density along the GPS ray path during the occultation plays an important role affecting the correlation between COSMIC and ionosonde

  14. Comparison of measured electron density rise and calculated neutral beam particle deposition in the TFTR tokamak

    SciTech Connect

    Park, H.; Budny, R.; McCune, D.; Taylor, G.; Zarnstorff, M.C. . Plasma Physics Lab.); Barnes, C.W. )

    1991-12-01

    The initial rate of rise of the central electron density during {approximately}100 keV deuterium neutral beam injection is found to agree well with calculations of the beam deposition rate. The best agreement is with beam deposition calculations using older tabulations of the atomic cross-sections; the effects of using new tabulations or including multi-step ionization processes appear to approximately cancel. The neutral-beam deposition profile is a strong function of both the magnitude and the shape of the target plasma density. Peaked heating profiles can be achieved at high target densities only from peaked target density profiles. 15 refs., 4 figs.

  15. Electron density fluctuation measurements using a multichannel microwave interferometer in GAMMA 10

    SciTech Connect

    Yoshikawa, M.; Shima, Y.; Matsumoto, T.; Nakahara, A.; Yanagi, N.; Itakura, A.; Hojo, H.; Kobayashi, T.; Matama, K.; Tatematsu, Y.; Imai, T.; Kohagura, J.; Hirata, M.; Nakashima, Y.; Cho, T.

    2006-10-15

    Measurement of fluctuation in plasma is important for studying the improvement in plasma confinement by the formation of the plasma confinement potential. The density fluctuation is observed by microwaves by methods such as interferometry, reflectometry and Fraunhofer diffraction method. We have constructed a new multichannel microwave interferometer to measure the plasma density and fluctuation radial profiles in a single plasma shot. We successfully measured the time-dependent density and line-integrated density fluctuation radial profiles in a single plasma shot using the multichannel microwave interferometer. Thus, we have developed a useful tool for studying the improvement in plasma confinement by the formation of plasma confinement potential.

  16. Developing an ANN electron density profile model over Cyprus based on ionosonde measurements

    NASA Astrophysics Data System (ADS)

    Haralambous, H.; Papadopoulos, Harris; Mostafa, Md. Golam

    2015-06-01

    The impact of the upper atmosphere on navigation, communication as well as surveillance systems is defined by the state of the ionosphere and in particular by variations in its electron density profile along the signal propagation path. The requirement for the accurate specification of the electron density profile stems from the fact that the electron density at each altitude determines the refractive index for radiowaves that are refracted by or penetrate the ionosphere and therefore affects significantly navigation and communication signals. Consequently satellite systems that are based on trans-ionospheric propagation may be affected by complex variations in the ionospheric structure in space and time leading to degradation of the availability, accuracy and reliability of their services. Therefore the specification of the electron density profile over a geographical region is very important within the context of operation of such systems. Although regional models have been developed for such a purpose by interpolating data coming from different instruments using various techniques, for a limited geographical scope, the single station model approach is the preferable option as it best encapsulates the behaviour of the ionosphere over the station. This paper presents the development of an Artificial Neural Network (ANN) model for the electron density profile of the ionosphere over Cyprus based on manually scaled ionograms collected at the Nicosia ionosonde station during the period 2009-2013.

  17. Visualization of electronic density

    DOE PAGES

    Grosso, Bastien; Cooper, Valentino R.; Pine, Polina; ...

    2015-04-22

    An atom’s volume depends on its electronic density. Although this density can only be evaluated exactly for hydrogen-like atoms, there are many excellent numerical algorithms and packages to calculate it for other materials. 3D visualization of charge density is challenging, especially when several molecular/atomic levels are intertwined in space. We explore several approaches to 3D charge density visualization, including the extension of an anaglyphic stereo visualization application based on the AViz package to larger structures such as nanotubes. We will describe motivations and potential applications of these tools for answering interesting questions about nanotube properties.

  18. Stark broadening measurement of the electron density in an atmospheric pressure argon plasma jet with double-power electrodes

    SciTech Connect

    Qian Muyang; Ren Chunsheng; Wang Dezhen; Zhang Jialiang; Wei Guodong

    2010-03-15

    Characteristics of a double-power electrode dielectric barrier discharge of an argon plasma jet generated at the atmospheric pressure are investigated in this paper. Time-averaged optical emission spectroscopy is used to measure the plasma parameters, of which the excitation electron temperature is determined by the Boltzmann's plot method whereas the gas temperature is estimated using a fiber thermometer. Furthermore, the Stark broadening of the hydrogen Balmer H{sub {beta}} line is applied to measure the electron density, and the simultaneous presence of comparable Doppler, van der Waals, and instrumental broadenings is discussed. Besides, properties of the jet discharge are also studied by electrical diagnosis. It has been found that the electron densities in this argon plasma jet are on the order of 10{sup 14} cm{sup -3}, and the excitation temperature, gas temperature, and electron density increase with the applied voltage. On the other hand, these parameters are inversely proportional to the argon gas flow rate.

  19. Simulation and analysis of TE wave propagation for measurement of electron cloud densities in particle accelerators

    NASA Astrophysics Data System (ADS)

    Sonnad, Kiran G.; Hammond, Kenneth C.; Schwartz, Robert M.; Veitzer, Seth A.

    2014-08-01

    The use of transverse electric (TE) waves has proved to be a powerful, noninvasive method for estimating the densities of electron clouds formed in particle accelerators. Results from the plasma simulation program VSim have served as a useful guide for experimental studies related to this method, which have been performed at various accelerator facilities. This paper provides results of the simulation and modeling work done in conjunction with experimental efforts carried out at the Cornell electron storage ring “Test Accelerator” (CESRTA). This paper begins with a discussion of the phase shift induced by electron clouds in the transmission of RF waves, followed by the effect of reflections along the beam pipe, simulation of the resonant standing wave frequency shifts and finally the effects of external magnetic fields, namely dipoles and wigglers. A derivation of the dispersion relationship of wave propagation for arbitrary geometries in field free regions with a cold, uniform cloud density is also provided.

  20. D-region electron densities obtained by differential absorption and phase measurements with a 3-MHz-Doppler radar

    NASA Astrophysics Data System (ADS)

    Singer, W.; Latteck, R.; Friedrich, M.; Dalin, P.; Kirkwood, S.; Engler, N.; Holdsworth, D.

    2005-08-01

    A Doppler radar at 3.17 MHz has been installed close to the Andøya Rocket Range as part of the ALOMAR observatory at Andenes, Norway (69.3°N, 16.0°E) in summer 2002 to improve the ground based capabilities for measurements of small scale features and electron number densities in the mesosphere. The main feature of the new radar is the transmitting/receiving antenna which is arranged as a Mills Cross of 29 crossed half-wave dipoles with a minimum beam width of about 7°. The modular transceiver system provides high flexibility in beam forming and pointing as well as in switching of the polarisation between ordinary and extraordinary mode on transmission and reception. Doppler winds and electron number densities can be measured between about 55 km and 90 km with a time resolution of 9 minutes. The electron number density profiles derived with differential absorption (DAE) and differential phase (DPE) measurements are in remarkable good agreement. We discuss the diurnal and seasonal variability of electron densities obtained at Andenes in 2004/2005, the response of D-region electron densities to geomagnetic disturbances and solar proton events. The results are compared with rocket measurements from Andenes and with observations from EISCAT VHF radar at Tromsø.

  1. Reconstruction of the ionospheric 3D electron density distribution by assimilation of ionosonde measurements and operational TEC estimations

    NASA Astrophysics Data System (ADS)

    Gerzen, Tatjana; Wilken, Volker; Jakowski, Norbert; Hoque, Mainul M.

    2013-04-01

    New methods to generate maps of the F2 layer peak electron density of the ionosphere (NmF2) and to reconstruct the ionospheric 3D electron density distribution will be presented. For validation, reconstructed NmF2 maps will be compared with peak electron density measurements from independent ionosonde stations. The ionosphere is the ionized part of the upper Earth's atmosphere lying between about 50 km and 1000 km above the Earth's surface. From the applications perspective the electron density, Ne, is certainly one of the most important parameters of the ionosphere because of its strong impact on radio signal propagation. Especially the critical frequency, foF2, which is related to the F2 layer peak electron density, NmF2, according to the equation NmF2-m3 = 1.24 ? 1010(foF2-MHz)2 and builds the lower limit for the maximum usable frequency MUF, is of particular interest with regard to the HF radio communication applications. In a first order approximation the ionospheric delay of transionospheric radio waves of frequency f is proportional to 1-f2 and to the integral of the electron density (total electron content - TEC) along the ray path. Thus, the information about the total electron content along the receiver-to-satellite ray path can be obtained from the dual frequency measurements permanently transmitted by GNSS satellites. As data base for our reconstruction approaches we use the vertical sounding measurements of the ionosonde stations providing foF2 and routinely generated TEC maps in SWACI (http://swaciweb.dlr.de) at DLR Neustrelitz. The basic concept of our approach is the following one: To reconstruct NmF2 maps we assimilate the ionosonde data into the global Neustrelitz F2 layer Peak electron Density Model (NPDM) by means of a successive corrections method. The TEC maps are produced by assimilating actual ground based GPS measurements providing TEC into an operational version of Neustrelitz TEC Model (NTCM). Finally, the derived NmF2 and TEC maps in

  2. Coronal electron density distributions estimated from CMEs, DH type II radio bursts, and polarized brightness measurements

    NASA Astrophysics Data System (ADS)

    Lee, Jae-Ok; Moon, Y.-J.; Lee, Jin-Yi; Lee, Kyoung-Sun; Kim, R.-S.

    2016-04-01

    We determine coronal electron density distributions (CEDDs) by analyzing decahectometric (DH) type II observations under two assumptions. DH type II bursts are generated by either (1) shocks at the leading edges of coronal mass ejections (CMEs) or (2) CME shock-streamer interactions. Among 399 Wind/WAVES type II bursts (from 1997 to 2012) associated with SOHO/LASCO (Large Angle Spectroscopic COronagraph) CMEs, we select 11 limb events whose fundamental and second harmonic emission lanes are well identified. We determine the lowest frequencies of fundamental emission lanes and the heights of leading edges of their associated CMEs. We also determine the heights of CME shock-streamer interaction regions. The CEDDs are estimated by minimizing the root-mean-square error between the heights from the CME leading edges (or CME shock-streamer interaction regions) and DH type II bursts. We also estimate CEDDs of seven events using polarized brightness (pB) measurements. We find the following results. Under the first assumption, the average of estimated CEDDs from 3 to 20 Rs is about 5-fold Saito's model (NSaito(r)). Under the second assumption, the average of estimated CEDDs from 3 to 10 Rs is 1.5-fold NSaito(r). While the CEDDs obtained from pB measurements are significantly smaller than those based on the first assumption and CME flank regions without streamers, they are well consistent with those on the second assumption. Our results show that not only about 1-fold NSaito(r) is a proper CEDD for analyzing DH type II bursts but also CME shock-streamer interactions could be a plausible origin for generating DH type II bursts.

  3. Pseudopotentials from electron density

    NASA Astrophysics Data System (ADS)

    Nagy, Á.; Andrejkovics, I.

    1996-05-01

    A method is introduced that allows the construction of pseudopotentials in the density-functional theory. This method is based on a procedure worked out by one of the authors [J. Phys. B 26, 43 (1993); Philos. Mag. B 69, 779 (1994)] for determining Kohn-Sham potentials, one-electron orbitals, and energies from the electron density. The Hartree-Fock densities of Bunge, Barrientos, and Bunge [At. Data Nucl. Data Tables 53, 114 (1993)] are used to obtain the Kohn-Sham potentials of the Li, Na, and K atoms, and then Phillips-Kleinman-type [Phys. Rev. 116, 287 (1959); 118, 1153 (1960)] pseudopotentials are calculated. The arbitrariness of the pseudo-orbital is removed by minimization of the kinetic energy.

  4. Measurement of a density profile of a hot-electron plasma in RT-1 with three-chord interferometry

    SciTech Connect

    Saitoh, H.; Yano, Y.; Yoshida, Z.; Nishiura, M.; Morikawa, J.; Kawazura, Y.; Nogami, T.; Yamasaki, M.

    2015-02-15

    The electron density profile of a plasma in a magnetospheric dipole field configuration was measured with a multi-chord interferometry including a relativistic correction. In order to improve the accuracy of density reconstruction, a 75 GHz interferometer was installed at a vertical chord of the Ring Trap 1 (RT-1) device in addition to previously installed ones at tangential and another vertical chords. The density profile was calculated by using the data of three-chord interferometry including relativistic effects for a plasma consisting of hot and cold electrons generated by electron cyclotron resonance heating (ECH). The results clearly showed the effects of density peaking and magnetic mirror trapping in a strongly inhomogeneous dipole magnetic field.

  5. Measurement of a density profile of a hot-electron plasma in RT-1 with three-chord interferometry

    NASA Astrophysics Data System (ADS)

    Saitoh, H.; Yano, Y.; Yoshida, Z.; Nishiura, M.; Morikawa, J.; Kawazura, Y.; Nogami, T.; Yamasaki, M.

    2015-02-01

    The electron density profile of a plasma in a magnetospheric dipole field configuration was measured with a multi-chord interferometry including a relativistic correction. In order to improve the accuracy of density reconstruction, a 75 GHz interferometer was installed at a vertical chord of the Ring Trap 1 (RT-1) device in addition to previously installed ones at tangential and another vertical chords. The density profile was calculated by using the data of three-chord interferometry including relativistic effects for a plasma consisting of hot and cold electrons generated by electron cyclotron resonance heating (ECH). The results clearly showed the effects of density peaking and magnetic mirror trapping in a strongly inhomogeneous dipole magnetic field.

  6. Assessment of plasma impedance probe for measuring electron density and collision frequency in a plasma with spatial and temporal gradients

    SciTech Connect

    Hopkins, Mark A. King, Lyon B.

    2014-05-15

    Numerical simulations and experimental measurements were combined to determine the ability of a plasma impedance probe (PIP) to measure plasma density and electron collision frequency in a plasma containing spatial gradients as well as time-varying oscillations in the plasma density. A PIP is sensitive to collision frequency through the width of the parallel resonance in the Re[Z]-vs.-frequency characteristic, while also being sensitive to electron density through the zero-crossing of the Im[Z]-vs.-frequency characteristic at parallel resonance. Simulations of the probe characteristic in a linear plasma gradient indicated that the broadening of Re[Z] due to the spatial gradient obscured the broadening due to electron collision frequency, preventing a quantitative measurement of the absolute collision frequency for gradients considered in this study. Simulation results also showed that the PIP is sensitive to relative changes in electron collision frequency in a spatial density gradient, but a second broadening effect due to time-varying oscillations made collision frequency measurements impossible. The time-varying oscillations had the effect of causing multiple zero-crossings in Im[Z] at parallel resonance. Results of experiments and simulations indicated that the lowest-frequency zero-crossing represented the lowest plasma density in the oscillations and the highest-frequency zero-crossing represented the highest plasma density in the oscillations, thus the PIP probe was found to be an effective tool to measure both the average plasma density as well as the maximum and minimum densities due to temporal oscillations.

  7. Measurement of Field Aligned Electron and Ion Densities and Ducts from the Whistler and Z Mode Radio Sounding from IMAGE

    NASA Astrophysics Data System (ADS)

    Sonwalkar, V. S.; Hazra, S.; Mayank, K.; Reddy, A.; Liu, Y.; Carpenter, D. L.

    2013-12-01

    We present recent results from the application of whistler mode (WM) and Z mode (ZM) radio sounding experiments from the IMAGE satellite to the magnetospheric plasma diagnostics. A recently developed WM radio sounding method [Sonwalkar et al., JGR, 116, A11210, doi:10.1029/2011JA016759, 2011] was applied to 200 cases of WM echoes observed within the plasmasphere to measure field aligned electron density (Ne) and ion densities (NH+, NHe+, NO+) for L~1.6 -4, altitude <5000 km, Kp ~1-7, and F10.7 ~ 72-110 (low solar activity). The measured plasma parameters are in general consistent with the past space borne (e.g. CHAMP, DMSP, Alouette, ISIS, AE) and ground (e.g. ionosonde) measurements, but show significant differences from those predicted by IRI-2012 and GCPM models. We believe our measurements will lead to an improved model of electron and ion densities at <5000 km within the plasmasphere. The WM radio sounding method was applied to a case study of the variation of plasma parameters at L~2 during the development of a major storm, from quiet conditions and subsequent recovery, followed by a moderate and minor storm. Our study showed that relative to the preceding quiet time: (1) There was depletion in electron density, H+, He+ and enhancement in O+ ions leading to increase in O+-H+ transition height; (2) The recovery period of electrons and individual ions was different; (3) A similar trend in the variation of electron density, H+, O+ was observed after the moderate storm and the minor storm but He+ was not affected. Following a ray tracing technique originally developed for whistler mode sounding, we analyzed the fast nonducted and ducted Z mode echoes to obtain field aligned electron density and duct parameters (duct width and enhancement) from the measured dispersion of Z mode echoes. With the help of two case studies, we illustrate that fast Z mode echoes provide measurement of electron density at altitudes <10,000 km and duct width and enhancement within an

  8. An evaluation of International Reference Ionosphere electron density in the polar cap and cusp using EISCAT Svalbard radar measurements

    NASA Astrophysics Data System (ADS)

    Merete Bjoland, Lindis; Belyey, Vasyl; Løvhaug, Unni Pia; La Hoz, Cesar

    2016-09-01

    Incoherent scatter radar measurements are an important source for studies of ionospheric plasma parameters. In this paper the EISCAT Svalbard radar (ESR) long-term database is used to evaluate the International Reference Ionosphere (IRI) model. The ESR started operations in 1996, and the accumulated database up to 2012 thus covers 16 years, giving an overview of the ionosphere in the polar cap and cusp during more than one solar cycle. Data from ESR can be used to obtain information about primary plasma parameters: electron density, electron and ion temperature, and line-of-sight plasma velocity from an altitude of about 50 and up to 1600 km. Monthly averages of electron density and temperature and ion temperature and composition are also provided by the IRI model from an altitude of 50 to 2000 km. We have compared electron density data obtained from the ESR with the predicted electron density from the IRI-2016 model. Our results show that the IRI model in general fits the ESR data well around the F2 peak height. However, the model seems to underestimate the electron density at lower altitudes, particularly during winter months. During solar minimum the model is also less accurate at higher altitudes. The purpose of this study is to validate the IRI model at polar latitudes.

  9. Electron density measurement in gas discharge plasmas by optical and acoustic methods

    NASA Astrophysics Data System (ADS)

    Biagioni, A.; Anania, M. P.; Bellaveglia, M.; Chiadroni, E.; Cianchi, A.; Di Giovenale, D.; Di Pirro, G.; Ferrario, M.; Filippi, F.; Mostacci, A.; Pompili, R.; Shpakov, V.; Vaccarezza, C.; Villa, F.; Zigler, A.

    2016-08-01

    Plasma density represents a very important parameter for both laser wakefield and plasma wakefield acceleration, which use a gas-filled capillary plasma source. Several techniques can be used to measure the plasma density within a capillary discharge, which are mainly based on optical diagnostic methods, as for example the well-known spectroscopic method using the Stark broadening effect. In this work, we introduce a preliminary study on an alternative way to detect the plasma density, based on the shock waves produced by gas discharge in a capillary. Firstly, the measurements of the acoustic spectral content relative to the laser-induced plasmas by a solid target allowed us to understand the main properties of the acoustic waves produced during this kind of plasma generation; afterwards, we have extended such acoustic technique to the capillary plasma source in order to calibrate it by comparison with the stark broadening method.

  10. Measuring atomic oxygen densities and electron properties in an Inductively Coupled Plasma for thin film deposition

    NASA Astrophysics Data System (ADS)

    Meehan, David; Gibson, Andrew; Booth, Jean-Paul; Wagenaars, Erik

    2016-09-01

    Plasma Enhanced Pulsed Laser Deposition (PE-PLD) is an advanced way of depositing thin films of oxide materials by using a laser to ablate a target, and passing the resulting plasma plume through a background Inductively-Coupled Plasma (ICP), instead of a background gas as is done in traditional PLD. The main advantage of PE-PLD is the control of film stoichiometry via the direct control of the reactive oxygen species in the ICP instead of relying on a neutral gas background. The aim is to deposit zinc oxide films from a zinc metal target and an oxygen ICP. In this work, we characterise the range of compositions of the reactive oxygen species achievable in ICPs; in particular the atomic oxygen density. The density of atomic oxygen has been determined within two ICPs of two different geometries over a range of plasma powers and pressures with the use of Energy Resolved Actinometry (ERA). ERA is a robust diagnostic technique with determines both the dissociation degree and average electron energy by comparing the excitation ratios of two oxygen and one argon transition. Alongside this the electron densities have been determined with the use of a hairpin probe. This work received financial support from the EPSRC, and York-Paris CIRC.

  11. Measurement of Electron Density Using the Multipole Resonance Probe, Langmuir Probe and Optical Emission Spectroscopy in Low Pressure Plasmas with Different Electron Energy Distribution Functions

    NASA Astrophysics Data System (ADS)

    Oberberg, Moritz; Bibinov, Nikita; Ries, Stefan; Awakowicz, Peter; Institute of Electrical Engineering; Plasma Technology Team

    2016-09-01

    In recently publication, the young diagnostic tool Multipole Resonance Probe (MRP) for electron density measurements was introduced. It is based on active plasma resonance spectroscopy (APRS). The probe was simulated und evaluated for different devices. The geometrical and electrical symmetry simplifies the APRS model, so that the electron density can be easily calculated from the measured resonance. In this work, low pressure nitrogen mixture plasmas with different electron energy distribution functions (EEDF) are investigated. The results of the MRP measurement are compared with measurements of a Langmuir Probe (LP) and Optical Emission Spectroscopy (OES). Probes and OES measure in different regimes of kinetic electron energy. Both probes measure electrons with low kinetic energy (<10 eV), whereas the OES is influenced by electrons with high kinetic energy which are needed for transitions of molecule bands. By the determination of the absolute intensity of N2(C-B) and N2+(B-X)electron temperature and density can be calculated. In a non-maxwellian plasma, all plasma diagnostics need to be combined.

  12. Validation of NeQuick TEC data ingestion technique against C/NOFS and EISCAT electron density measurements

    NASA Astrophysics Data System (ADS)

    Nigussie, M.; Radicella, S. M.; Damtie, B.; Yizengaw, E.; Nava, B.; Roininen, L.

    2016-07-01

    This paper investigates a technique to estimate near-real-time electron density structure of the ionosphere. Ground-based GPS receiver total electron content (TEC) at low and high latitudes has been used to assist the NeQuick 2 model. First, we compute model input (effective ionization level) when the modeled slant TEC (sTEC) best fits the measured sTEC by single GPS receiver (reference station). Then we run the model at different locations nearby the reference station and produce the spatial distribution of the density profiles of the ionosphere in the East African region. We investigate the performance of the model, before and after data ingestion in estimating the topside ionosphere density profiles. This is carried out by extracting in situ density from the model at the corresponding location of C/NOFS (Communication/Navigation Outage Forecast System) satellite orbit and comparing the modeled ion density with the in situ ion density observed by Planar Langmuir Probe onboard C/NOFS. It is shown that the performance of the model after data ingestion reproduces the topside ionosphere better up to about 824 km away from the reference station than that before adaptation. Similarly, for high-latitude region, NeQuick 2 adapted to sTEC obtained from high-latitude (Tromsø in Norway) GPS receiver and the model used to reproduce parameters measured by European Incoherent Scatter Scientific Association (EISCAT) VHF radar. It is shown that the model after adaptation shows considerable improvement in estimating EISCAT measurements of electron density profile, F2 peak density, and height.

  13. Middle atmosphere measurements of small-scale electron density irregularities and ion properties during the MAC/Epsilon campaign

    NASA Technical Reports Server (NTRS)

    Blood, S. P.; Mitchell, J. D.; Croskey, C. L.

    1989-01-01

    Rocket payloads designed to measure small scale electron density irregularities and ion properties in the middle atmosphere were flown with each of the three main salvos of the MAC/Epsilon campaign conducted at the Andoya Rocket Range, Norway, during October to November 1987. Fixed bias, hemispheric nose tip probes measured small scale electron density irregularities, indicative of neutral air turbulence, during the rocket's ascent; and subsequently, parachute-borne Gerdien condensers measured the region's polar electrical conductivity, ion mobility and density. One rocket was launched during daylight (October 15, 1052:20 UT), and the other two launches occurred at night (October 21, 2134 UT: November 12, 0021:40 UT) under moderately disturbed conditions which enhanced the detection and measurement of turbulence structures. A preliminary analysis of the real time data displays indicates the presence of small scale electron density irregularities in the altitude range of 60 to 90 km. Ongoing data reduction will determine turbulence parameters and also the region's electrical properties below 90 km.

  14. Inductively-coupled plasmas in pure Cl, Oand mixtures: measurements of atoms, ClxOyand electron densities

    NASA Astrophysics Data System (ADS)

    Foucher, Mickaël; Carbone, Emile; Booth, Jean-Paul; Chabert, Pascal; LPP-Plasmas froids Team

    2014-10-01

    Inductively-coupled plasmas in Cl/O (often with HBr) are widely used in the microelectronics industry for the etching of silicon CMOS gates. Many simulations describing these plasmas (global and 2-dimensional fluid models such as HPEM) have been developed but experimental validation is sparse. This paper addresses this gap with a large quantity of experimental data in plasmas of Cl, Oand their mixtures. The plasma is excited by a 4-turn planar coil powered at 13.56 MHz through a dielectric window, and contained in a cylindrical anodized aluminium reactor (55 cm diameter, 10 cm high). Electron densities were measured with a microwave hairpin resonator. In all cases the electron density passes through a maximum with pressure. The ground-state O and Cl atom density was measured by Two-Photon Absorption Laser-Induced Fluorescence (TALIF) combined with specific absolute calibration techniques. Broad-band absorption spectroscopy was used to measure the density of Cland vibrationally excited Omolecules, excited state Cl atoms and a range of oxychlorides products. To our knowledge this is the first time that these oxychloride densities and vibrationally excited molecules have been measured in low-pressure plasmas.

  15. Upgraded millimeter-wave interferometer for measuring the electron density during the beam extraction in the negative ion source.

    PubMed

    Tokuzawa, T; Kisaki, M; Nagaoka, K; Tsumori, K; Ito, Y; Ikeda, K; Nakano, H; Osakabe, M; Takeiri, Y; Kaneko, O

    2016-11-01

    The upgraded millimeter-wave interferometer with the frequency of 70 GHz is installed on a large-scaled negative ion source. Measurable line-averaged electron density is from 2 × 10(15) to 3 × 10(18) m(-3) in front of the plasma grid. Several improvements such as the change to shorter wavelength probing with low noise, the installation of special ordered horn antenna, the signal modulation for a high accuracy digital phase detection, the insertion of insulator, and so on, are carried out for the measurement during the beam extraction by applying high voltage. The line-averaged electron density is successfully measured and it is found that it increases linearly with the arc power and drops suddenly at the beam extraction.

  16. Upgraded millimeter-wave interferometer for measuring the electron density during the beam extraction in the negative ion source

    NASA Astrophysics Data System (ADS)

    Tokuzawa, T.; Kisaki, M.; Nagaoka, K.; Tsumori, K.; Ito, Y.; Ikeda, K.; Nakano, H.; Osakabe, M.; Takeiri, Y.; Kaneko, O.

    2016-11-01

    The upgraded millimeter-wave interferometer with the frequency of 70 GHz is installed on a large-scaled negative ion source. Measurable line-averaged electron density is from 2 × 1015 to 3 × 1018 m-3 in front of the plasma grid. Several improvements such as the change to shorter wavelength probing with low noise, the installation of special ordered horn antenna, the signal modulation for a high accuracy digital phase detection, the insertion of insulator, and so on, are carried out for the measurement during the beam extraction by applying high voltage. The line-averaged electron density is successfully measured and it is found that it increases linearly with the arc power and drops suddenly at the beam extraction.

  17. Simulations of Electron-Cloud Current Density Measurements in Dipoles, Drifts And Wigglers at CesrTA

    SciTech Connect

    Calvey, J.; Crittenden, J. A.; Dugan, G.; Greenwald, S.; Livezey, J. A.; Palmer, M. A.; Rubin, D.; Harkay, K. C.; Jain, P.; Kanazawa, K.; Suetsugu, Y.; Celata, C. M.; Furman, M.; Pivi, M. T. F.; Wang, L.; Kreinick, D.; Penn, G.; Venturini, M.

    2009-05-04

    A core component of the CesrTA research program at Cornell is to fully understand the electron cloud effect through the use of simulation programs that have been developed to predict the growth of the cloud and its interaction with the beam. As a local probe of the electron cloud, several segmented retarding field analyzers (RFAs) have been installed in CesrTA in dipole, drift and wiggler regions. Using these RFAs, the energy spectrum of the time-average electron cloud current density striking the walls has been measured for a variety of bunch train patterns, with different bunch currents, beam energies, emittances, and bunch lengths, and for both positron and electron beams. This paper will compare these measurements with the predictions of simulation programs.

  18. Simulations of Electron-Cloud Current Density Measurements in Dipoles, Drifts, and Wigglers at CesrTA

    SciTech Connect

    Calvey, J.; Crittenden, J. A.; Dugan, G.; Greenwald, S.; Kreinick, D.; Livezey, J. A.; Palmer, M. A.; Rubin, D.; Fukuma, H.; Jain, P.; Kanazawa, K.; Suetsugu, Y.; Celata, C. M.; Furman, M.; Penn, G.; Venturini, M.; Pivi, M.T.F.; Harkay, K.C.; Wang, L.

    2009-05-01

    A core component of the Cesr-TA research program at Cornell is to fully understand the electron cloud effect through the use of simulation programs that have been developed to predict the growth of the cloud and its interaction with the beam. As a local probe of the electron cloud, several segmented retarding field analyzers (RFAs) have been installed in CesrTA in dipole, drift and wiggler regions. Using these RFAs, the energy spectrum of the time-average electron cloud current density striking the walls has been measured for a variety of bunch train patterns, with different bunch currents, beam energies, emittances, and bunch lengths, and for both positron and electron beams. This paper will compare these measurements with the predictions of simulation programs.

  19. Development of a Method for Local Electron Temperature and Density Measurements in the Divertor of the JET Tokamak

    NASA Technical Reports Server (NTRS)

    Jupen, C.; Meigs, A.; Bhatia, A. K.; Brezinsek, S.; OMullane, M.

    2004-01-01

    Plasma volume recombination in the divertor, a process in which charged particles recombine to neutral atoms, contributes to plasma detachment and hence cooling at the divertor target region. Detachment has been observed at JET and other tokamaks and is known to occur at low electron temperatures (T(sub e)<1 eV) and at high electron density (n(sub e)>10(exp 20)/m(exp 3)). The ability to measure such low temperatures is therefore of interest for modelling the divertor. In present work we report development of a new spectroscopic technique for investigation of local electron density (n(sub e)) and temperature (T,) in the outer divertor at JET.

  20. Identification of errors in the electron density measurements of a tangential interferometer/polarimeter system during a tokamak discharge

    SciTech Connect

    Arakawa, H.; Kawano, Y.; Itami, K.

    2012-10-15

    A new method for the comparative verification of electron density measurements obtained with a tangential interferometer and a polarimeter during a discharge is proposed. The possible errors associated with the interferometer and polarimeter are classified by the time required for their identification. Based on the characteristics of the errors, the fringe shift error of the interferometer and the low-frequency noise of the polarimeter were identified and corrected for the JT-60U tangential interferometer/polarimeter system.

  1. Development of a spectroscopic technique for simultaneous magnetic field, electron density, and temperature measurements in Z-pinch plasmas

    NASA Astrophysics Data System (ADS)

    Dutra, Eric; Presura, Radu; Covington, Aaron; Mancini, Roberto; Darling, Timothy; Angermeier, William

    2016-10-01

    Visible spectroscopic techniques are often used in plasma experiments to measure B-field induced Zeeman splitting, electron densities via Stark broadening, and temperatures from Doppler broadening. However, when electron densities and temperatures are sufficiently high, the broadening of the Stark and Doppler components can dominate the emission spectra and obscure the Zeeman component. In this research, we are developing a time-resolved multi-axial technique for measuring the Zeeman, Stark, and Doppler broadened line emission of dense magnetized plasmas for Z-pinch. In parallel, we are developing a line-shape modeling code that incorporates the broadening effects due to Stark, Doppler, and Zeeman effects for dense magnetized plasma. Experiments were conducted at the University of Nevada (Reno) at the Nevada Terawatt Facility (NTF) using the 1 MA Z-pinch (Zebra). The research explored the optical emission of Al III doublet, 4P 2P3/2 to 4S 2S1/2 and 4P 2P1/2 to 4s 2S1/2 transitions and used it to measure Zeeman, Stark, and Doppler broadened emission. The initial parameters for the line shape code are varied to simulate emission spectra. The simulated spectra are compared to experimental results. These results are used to infer temperature, electron density, and B-fields in the magnetized plasma.

  2. Kinetic Temperature and Electron Density Measurement in an Inductively Coupled Plasma Torch using Degenerate Four-Wave Mixing

    NASA Technical Reports Server (NTRS)

    Schafer, Julia; Lyons, Wendy; Tong, WIlliam G.; Danehy, Paul M.

    2008-01-01

    Laser wave mixing is presented as an effective technique for spatially resolved kinetic temperature measurements in an atmospheric-pressure radio-frequency inductively-coupled plasma. Measurements are performed in a 1 kW, 27 MHz RF plasma using a continuous-wave, tunable 811.5-nm diode laser to excite the 4s(sup 3)P2 approaches 4p(sup 3)D3 argon transition. Kinetic temperature measurements are made at five radial steps from the center of the torch and at four different torch heights. The kinetic temperature is determined by measuring simultaneously the line shape of the sub-Doppler backward phase-conjugate degenerate four-wave mixing and the Doppler-broadened forward-scattering degenerate four-wave mixing. The temperature measurements result in a range of 3,500 to 14,000 K+/-150 K. Electron densities measured range from 6.1 (+/-0.3) x 10(exp 15)/cu cm to 10.1 (+/-0.3) x 10(exp 15)/cu cm. The experimental spectra are analyzed using a perturbative treatment of the backward phase-conjugate and forward-geometry wave-mixing theory. Stark width is determined from the collisional broadening measured in the phase-conjugate geometry. Electron density measurements are made based on the Stark width. The kinetic temperature of the plasma was found to be more than halved by adding deionized water through the nebulizer.

  3. Saturn's ionosphere - Inferred electron densities

    NASA Astrophysics Data System (ADS)

    Kaiser, M. L.; Desch, M. D.; Connerney, J. E. P.

    1984-04-01

    During the two Voyager encounters with Saturn, radio bursts were detected which appear to have originated from atmospheric lightning storms. Although these bursts generally extended over frequencies from as low as 100 kHz to the upper detection limit of the instrument, 40 MHz, they often exhibited a sharp but variable low frequency cutoff below which bursts were not detected. We interpret the variable low-frequency extent of these bursts to be due to the reflection of the radio waves as they propagate through an ionosphere which varies with local time. We obtain estimates of electron densities at a variety of latitude and local time locations. These compare well with the dawn and dusk densities measured by the Pioneer 11 Voyager Radio Science investigations, and with model predictions for dayside densities. However, we infer a two-order-of-magnitude diurnal variation of electron density, which had not been anticipated by theoretical models of Saturn's ionosphere, and an equally dramatic extinction of ionospheric electron density by Saturn's rings. Previously announced in STAR as N84-17102

  4. Saturn's ionosphere: Inferred electron densities

    NASA Technical Reports Server (NTRS)

    Kaiser, M. L.; Desch, M. D.; Connerney, J. E. P.

    1983-01-01

    During the two Voyager encounters with Saturn, radio bursts were detected which appear to have originated from atmospheric lightning storms. Although these bursts generally extended over frequencies from as low as 100 kHz to the upper detection limit of the instrument, 40 MHz, they often exhibited a sharp but variable low frequency cutoff below which bursts were not detected. We interpret the variable low-frequency extent of these bursts to be due to the reflection of the radio waves as they propagate through an ionosphere which varies with local time. We obtain estimates of electron densities at a variety of latitude and local time locations. These compare well with the dawn and dusk densitis measured by the Pioneer 11 Voyager Radio Science investigations, and with model predictions for dayside densities. However, we infer a two-order-of-magnitude diurnal variation of electron density, which had not been anticipated by theoretical models of Saturn's ionosphere, and an equally dramatic extinction of ionospheric electron density by Saturn's rings.

  5. Development of a spectroscopic technique for simultaneous magnetic field, electron density, and temperature measurements in ICF-relevant plasmas

    NASA Astrophysics Data System (ADS)

    Dutra, E. C.; Koch, J. A.; Presura, R.; Angermeier, W. A.; Darling, T.; Haque, S.; Mancini, R. C.; Covington, A. M.

    2016-11-01

    Spectroscopic techniques in the visible range are often used in plasma experiments to measure B-field induced Zeeman splitting, electron densities via Stark broadening, and temperatures from Doppler broadening. However, when electron densities and temperatures are sufficiently high, the broadening of the Stark and Doppler components can dominate the emission spectra and obscure the Zeeman component. In this research, we are developing a time-resolved multi-axial technique for measuring the Zeeman, Stark, and Doppler broadened line emission of dense magnetized plasmas for Z-pinch and Dense Plasma Focus (DPF) accelerators. The line emission is used to calculate the electron densities, temperatures, and B-fields. In parallel, we are developing a line-shape modeling code that incorporates the broadening effects due to Stark, Doppler, and Zeeman effects for dense magnetized plasma. This manuscript presents the details of the experimental setup and line shape code, along with the results obtained from an Al iii doublet at the University of Nevada, Reno at Nevada Terawatt Facility. Future tests are planned to further evaluate the technique and modeling on other material wire array, gas puff, and DPF platforms.

  6. Scientific objectives of the Plazma experiment in the Phobos project and principles underlying the measurement of electron density in the Martian ionosphere

    NASA Astrophysics Data System (ADS)

    Breus, T. K.; Krymskii, A. M.; Shtern, D. Ia.; El'Kin, M. L.

    A theoretical evaluation is presented which suggests that vertical profiles of electron density in the Martian ionosphere can be measured effectively via radar sounding from Phobos orbit. It is further suggested that such measurements can be performed with a resolution sufficient to detect a sharp decline of electron density in the ionosphere, corresponding to its upper boundary.

  7. Experimental measurement of spatially resolved electron density in a filament of a pulsed positive streamer discharge in water

    SciTech Connect

    Wen, Xiao Qiong; Niu, Zhi Wen; Ren, Chun-Sheng; Hou, Bo

    2015-06-29

    By combining a high-speed frame camera with a monochromator, the spatially resolved optical emission spectrum of hydrogen α line in a single filament of a pulsed positive streamer discharge in water has been experimentally measured. The spatially resolved electron densities in a single filament of a pulsed positive streamer discharge in water with a conductivity of 200 μS/cm were investigated. During the experiment, the average energy per pulse of discharge was 90.6 ± 13.6 mJ. The results show that the electron density in the streamer filament is 10{sup 17–18}/cm{sup 3}, and present a decreasing tendency along the axial direction of the streamer filament with increasing distance from the tip of the anode.

  8. Multichannel microwave interferometer with an antenna switching system for electron density measurement in a laboratory plasma experiment

    SciTech Connect

    Kawamori, Eiichirou; Lin, Yu-Hsiang; Mase, Atsushi; Nishida, Yasushi; Cheng, C. Z.

    2014-02-15

    This study presents a simple and powerful technique for multichannel measurements of the density profile in laboratory plasmas by microwave interferometry. This technique uses electromechanical microwave switches to temporally switch the connection between multiple receiver antennas and one phase-detection circuit. Using this method, the phase information detected at different positions is rearranged into a time series that can be acquired from a minimum number of data acquisition channels (e.g., two channels in the case of quadrature detection). Our successfully developed multichannel microwave interferometer that uses the antenna switching method was applied to measure the radial electron density profiles in a magnetized plasma experiment. The advantage of the proposed method is its compactness and scalability to multidimensional measurement systems at low cost.

  9. Understanding the dramatic role of anomalous dispersion on the measurement of electron densities in plasmas using interferometers

    SciTech Connect

    Nilsen, J; Johnson, W R; Iglesias, C A; Scofield, J H

    2005-07-20

    For decades the electron density of plasmas has been measured using optical interferometers. With the availability of good X-ray laser sources in the last decade interferometers have been extended into the wavelength range 14-47 nm, which has enabled researchers to probe even higher density plasmas. The data analysis assumes the index of refraction is due only to the free electrons, which makes the index less than one. Recent interferometer experiments in Al plasmas observed plasmas with index of refraction greater than one at 14 nm and brought into question the validity of the usual formula for calculating the index. In this paper we show how the anomalous dispersion from bound electrons can dominate the free electron contribution to the index of refraction in many plasmas and make the index greater than one or enhance the contribution to the index such that one would greatly overestimate the density of the plasma using interferometers. Using a new average-atom code we calculate the index of refraction in many plasmas at different temperatures for photon energies from 0 to 100 eV and compare against calculations done with OPAL. We also present examples of other plasmas that may have index of refraction greater than one at X-ray laser energies. During the next decade X-ray free electron lasers and other X-ray sources will be available to probe a wider variety of plasmas at higher densities and shorter wavelengths so understanding the index of refraction in plasmas will be even more essential.

  10. ISS FPP Ionospheric Electron Density and Temperature Measurements: Results, Comparison with the IRI-90 Model, and Implications for ISS Charging

    NASA Technical Reports Server (NTRS)

    Ferguson, D. C.; Hillard, G. B.; Morton, T. L.; Personen, R.

    2003-01-01

    We give measurement results of electron temperature and electron density from the Floating Potential Probe (FPP) on the International Space Station (ISS), and relate them to the electron current collection of the ISS solar arrays and the degree of charging of ISS when its Plasma Contacting Units (PCUs) are not operating. We show that on days of high solar activity index Kp, high levels of ISS charging are significantly more probable than on days of low solar activity, due to some abnormally low morning electron temperatures. Although the FPP electron temperatures measured are almost always higher than predicted by the International Reference Ionosphere 90 model (IRI-90), it is shown that the CHAMP satellite Langmuir Probe (PLP) also shows low dawn electron temperatures on the same day as those found by FPP. It is further shown that similar high levels of predicted charging, accompanied by vxB charging on the ISS structure, could exceed the -40 V specification on ISS charging, and could be dangerous to ISS astronauts if the PCUs fail to operate.

  11. Design of Q-band FMCW reflectometry for electron density profile measurement on the Joint TEXT tokamak

    NASA Astrophysics Data System (ADS)

    Linghan, Wan; Zhoujun, Yang; Ruobing, Zhou; Xiaoming, Pan; Chi, Zhang; Xianli, Xie; Bowen, Ruan

    2017-02-01

    The Q-band (33-50 GHz) fast sweep frequency modulated continuous wave (FMCW) reflectometry has been recently developed for electron density profile measurement on the Joint TEXT tokamak. It operates in ordinary mode (O-mode) with a 20 μs sweeping period, covering the density range from 1 × 1019 m-3 to 3 × 1019 m-3. On the bench test, a Yttrium Iron Garnet (YIG) filter is used for the dynamic calibration of the voltage controlled oscillator (VCO) to obtain a linear frequency sweep. Besides, the use of a power combiner helps to improve the side-band suppression level of the single side-band modulator (SSBM). The reconstructed density profiles are presented, which demonstrate the capability of the reflectometry.

  12. Multichannel Microwave Interferometer for Simultaneous Measurement of Electron Density and its Fluctuation on HL-2A Tokamak

    NASA Astrophysics Data System (ADS)

    Shi, Peiwan; Shi, Zhongbing; Chen, Wei; Zhong, Wulyu; Yang, Zengchen; Jiang, Min; Zhang, Boyu; Li, Yonggao; Yu, Liming; Liu, Zetian; Ding, Xuantong

    2016-07-01

    A multichannel microwave interferometer system has been developed on the HL-2A tokomak. Its working frequency is well designed to avoid the fringe jump effect. Taking the structure of HL-2A into account, its antennas are installed in the horizontal direction, i.e. one launcher in high field side (HFS) and four receivers in low field side (LFS). The fan-shaped measurement area covers those regions where the magnetohydrodynamics (MHD) instabilities are active. The heterodyne technique contributes to its high temporal resolution (1 μs). It is possible for the multichannel system to realize simultaneous measurements of density and its fluctuation. The quadrature phase detection based on the zero-crossing method is introduced to density measurement. With this system, reliable line-averaged densities and density profiles are obtained. The location of the saturated internal kink mode can be figured out from the mode showing different intensities on four channels, and the result agrees well with that measured by electron cyclotron emission imaging (ECEI). supported by the National Magnetic Confinement Fusion Science Program of China (Nos. 2013GB104002, 2013GB107002, 2014GB107001) and National Natural Science Foundation of China (Nos. 11475058, 11475057, 11261140326, 11405049)

  13. Topside-plasmasphere electron density profiles model by using AIS ionosonde measurements and calibrates GPS TEC data

    NASA Astrophysics Data System (ADS)

    Cesaroni, Claudio; Scotto, Carlo; Ippolito, Alessandro; Ciraolo, Luigi

    2013-04-01

    The Upper Atmosphere Physics group at INGV (Istituto Nazionale di Geofisica e Vulcanologia) developed Autoscala, a computer program for automatic scaling of the critical frequency foF2 and other ionospheric parameters derived from ionograms. Autoscala includes a routine that automatically estimates the electron density profile below F layer peak height hmF2, by adjusting the parameters of a model according to the recorded ionogram [Scotto (2009)]. By integrating this profile we can estimate bottom-side total electron content (bTEC). By means of a calibration technique [Ciraolo et al. (2007)], we are able to obtain calibrated vertical TEC (vTEC) values from GPS measurements over a receiver station. This method permits to estimate biases of the received signal due to transmitter-receiver hardware configuration. These biases must be eliminated from the GPS data in order to calibrate the experimental slant total electron content (sTEC) along the satellite-receiver line-of-sight (LoS). The difference between vTEC and bottom-side TEC (bTEC) permits to evaluate electron content of the topside ionospheric region (tTEC). Starting from tTEC, bottom-side parameters (foF2, hmF2, scale height at hmF2) obtained by ionosonde and O+ - H+ transition level, we can solve a system of equations based on different ionospheric profiler (Chapman, sech-squared and exponential) the solution of which provides ion scale height [Stankov et al. (2003)]. This last factor is sufficient to establish the vertical distribution of electrons in topside and plasmasphere regions. Obtained vertical profiles could be used to develop a new model for real time estimation of TEC and topside electron density distribution. References: Scotto, C. (2009). Electron density profile calculation technique for Autoscala ionogram analysis. Advances in Space Research, 44(6), 756-766. doi:10.1016/j.asr.2009.04.037 Ciraolo, L., et al. "Calibration errors on experimental slant total electron content (TEC) determined with

  14. Improvement of GPS radio occultation retrieval error of E region electron density: COSMIC measurement and IRI model simulation

    NASA Astrophysics Data System (ADS)

    Wu, Kang-Hung; Su, Ching-Lun; Chu, Yen-Hsyang

    2015-03-01

    In this article, we use the International Reference Ionosphere (IRI) model to simulate temporal and spatial distributions of global E region electron densities retrieved by the FORMOSAT-3/COSMIC satellites by means of GPS radio occultation (RO) technique. Despite regional discrepancies in the magnitudes of the E region electron density, the IRI model simulations can, on the whole, describe the COSMIC measurements in quality and quantity. On the basis of global ionosonde network and the IRI model, the retrieval errors of the global COSMIC-measured E region peak electron density (NmE) from July 2006 to July 2011 are examined and simulated. The COSMIC measurement and the IRI model simulation both reveal that the magnitudes of the percentage error (PE) and root mean-square-error (RMSE) of the relative RO retrieval errors of the NmE values are dependent on local time (LT) and geomagnetic latitude, with minimum in the early morning and at high latitudes and maximum in the afternoon and at middle latitudes. In addition, the seasonal variation of PE and RMSE values seems to be latitude dependent. After removing the IRI model-simulated GPS RO retrieval errors from the original COSMIC measurements, the average values of the annual and monthly mean percentage errors of the RO retrieval errors of the COSMIC-measured E region electron density are, respectively, substantially reduced by a factor of about 2.95 and 3.35, and the corresponding root-mean-square errors show averaged decreases of 15.6% and 15.4%, respectively. It is found that, with this process, the largest reduction in the PE and RMSE of the COSMIC-measured NmE occurs at the equatorial anomaly latitudes 10°N-30°N in the afternoon from 14 to 18 LT, with a factor of 25 and 2, respectively. Statistics show that the residual errors that remained in the corrected COSMIC-measured NmE vary in a range of -20% to 38%, which are comparable to or larger than the percentage errors of the IRI-predicted NmE fluctuating in a

  15. Inductively-coupled plasmas in pure O2: measurements of densities of O atoms, electrons and vibrationally excited Omolecules

    NASA Astrophysics Data System (ADS)

    Foucher, Mickaël; Carbone, Emile; Booth, Jean-Paul; Chabert, Pascal; LPP-Plasmas froids Team

    2014-10-01

    Inductively-coupled plasmas containing O2 (pure or mixtures) are widely used in materials processing. Various simulations have been developed but experimental validation is still sparse. We present here a comprehensive data set for O2 plasmas over a wide range of pressure and RF power to address this need. The plasma is excited with a 4-turn planar coil through a dielectric window at 13.56 MHz in an anodized aluminium reactor. The electron density was measured with a microwave resonator hairpin probe. It increases continuously with RF power, but with pressure it passes through a broad maximum around 40 mTorr. Ground-state O atom densities were determined using Two-Photon Absorption Laser-Induced Fluorescence combined with absolute calibration using Xe TALIF. The atom density increases with gas pressure, but with RF power it first increases but progressively saturates tot about 20% of the initial (no plasma) gas density. A novel high-sensitivity ultra-broad-band absorption spectroscopy setup allowed O2 molecules to be detected in high vibrational states (up to v = 18) via the Schumann-Runge bands. Molecular Ovibrational temperatures up to 12,000 K were observed, whereas the rotational temperature did not exceed 500 K. This indicates that electron-impact pumping of vibrational levels is important, whereas V-T transfer is slow. These processes must be included to accurately model the O2 plasma system.

  16. Edge electron density profiles and fluctuations measured by two-dimensional beam emission spectroscopy in the KSTAR

    SciTech Connect

    Nam, Y. U. Wi, H. M.; Zoletnik, S.; Lampert, M.; Kovácsik, Ákos

    2014-11-15

    Beam emission spectroscopy (BES) system in Korea Superconducting Tokamak Advanced Research (KSTAR) has recently been upgraded. The background intensity was reduced from 30% to 2% by suppressing the stray lights. This allows acquisition of the relative electron density profiles on the plasma edge without background subtraction from the beam power modulation signals. The KSTAR BES system has its spatial resolution of 1 cm, the temporal resolution of 2 MHz, and a total 32 channel (8 radial × 4 poloidal) avalanche photo diode array. Most measurements were done on the plasma edge, r/a ∼ 0.9, with 8 cm radial measurement width that covers the pedestal range. High speed density profile measurements reveal temporal behaviors of fast transient events, such as the precursors of edge localized modes and the transitions between confinement modes. Low background level also allows analysis of the edge density fluctuation patterns with reduced background fluctuations. Propagation of the density structures can be investigated by comparing the phase delays between the spatially distributed channels.

  17. Spectral optimization for measuring electron density by the dual-energy computed tomography coupled with balanced filter method.

    PubMed

    Saito, Masatoshi

    2009-08-01

    Dual-energy computed tomography (DECT) has the potential for measuring electron density distribution in a human body to predict the range of particle beams for treatment planning in proton or heavy-ion radiotherapy. However, thus far, a practical dual-energy method that can be used to precisely determine electron density for treatment planning in particle radiotherapy has not been developed. In this article, another DECT technique involving a balanced filter method using a conventional x-ray tube is described. For the spectral optimization of DECT using balanced filters, the author calculates beam-hardening error and air kerma required to achieve a desired noise level in electron density and effective atomic number images of a cylindrical water phantom with 50 cm diameter. The calculation enables the selection of beam parameters such as tube voltage, balanced filter material, and its thickness. The optimized parameters were applied to cases with different phantom diameters ranging from 5 to 50 cm for the calculations. The author predicts that the optimal combination of tube voltages would be 80 and 140 kV with Tb/Hf and Bi/Mo filter pairs for the 50-cm-diameter water phantom. When a single phantom calibration at a diameter of 25 cm was employed to cover all phantom sizes, maximum absolute beam-hardening errors were 0.3% and 0.03% for electron density and effective atomic number, respectively, over a range of diameters of the water phantom. The beam-hardening errors were 1/10 or less as compared to those obtained by conventional DECT, although the dose was twice that of the conventional DECT case. From the viewpoint of beam hardening and the tube-loading efficiency, the present DECT using balanced filters would be significantly more effective in measuring the electron density than the conventional DECT. Nevertheless, further developments of low-exposure imaging technology should be necessary as well as x-ray tubes with higher outputs to apply DECT coupled with the

  18. Compact and high-particle-flux thermal-lithium-beam probe system for measurement of two-dimensional electron density profile

    SciTech Connect

    Shibata, Y. Manabe, T.; Ohno, N.; Takagi, M.; Kajita, S.; Tsuchiya, H.; Morisaki, T.

    2014-09-15

    A compact and high-particle-flux thermal-lithium-beam source for two-dimensional measurement of electron density profiles has been developed. The thermal-lithium-beam oven is heated by a carbon heater. In this system, the maximum particle flux of the thermal lithium beam was ∼4 × 10{sup 19} m{sup −2} s{sup −1} when the temperature of the thermal-lithium-beam oven was 900 K. The electron density profile was evaluated in the small tokamak device HYBTOK-II. The electron density profile was reconstructed using the thermal-lithium-beam probe data and this profile was consistent with the electron density profile measured with a Langmuir electrostatic probe. We confirm that the developed thermal-lithium-beam probe can be used to measure the two-dimensional electron density profile with high time and spatial resolutions.

  19. Comparison of polar cap electron density enhancement due to solar illumination and geomagnetic activity as measured by IMAGE/RPI

    NASA Astrophysics Data System (ADS)

    Nsumei, P.; Reinisch, B.; Song, P.; Tu, J.; Huang, X.

    2007-12-01

    Polar cap electron density (Ne) measurements made between the years 2000 - 2005 by the radio plasma imager (RPI) on board the IMAGE spacecraft are used to study the density enhancements resulting from changes in solar illumination and geomagnetic activity level. This study covers a geocentric distance, R = 1.4 - 5.0 RE and the polar cap is defined by an empirical boundary model that takes into account the dynamic nature of the location and size of the polar cap. The average polar cap electron density profile depends on geomagnetic activity level e.g., measured by the Kp index and solar illumination (solar zenith angle) at the footprints of the geomagnetic field lines. Our analysis of RPI Ne data shows that increase in geomagnetic activity leads to an enhancement in Ne. This enhancement in Ne is found to increase with altitude. At geocentric distance of R = 4.5 RE, an increase in the geomagnetic activity level from Kp < 2 to ~5 results in an Ne increase by a factor of ~5. On the other hand, a strong solar illumination control of Ne at lower altitudes, and not at higher is observed. At geocentric distance of ~ 2 RE, the average Ne is larger on the sunlit side than on the dark side by a factor of 3 - 4 both for quiet and disturbed conditions. At geocentric distance of about 2.5 RE the effects of these two factors on Ne appear to be comparable. Similar to previous polar cap density models, a functional representation of RPI Ne that takes the form of a power law is proposed. While in the previous Ne functional representations the power index is a constant, the power index in our representation of Ne distribution is found to correlate with (and hence is a function of) the Kp index and the solar zenith angle (SZA).

  20. Comparison of topside electron density measured by Radio Occultation (RO) of FORMOSAT-3/COSMIC satellites and Digisondes on a global scale with IRI

    NASA Astrophysics Data System (ADS)

    Das, Tanmay; Haralambous, Haris

    2016-07-01

    This paper represents a comparison of the topside electron density of the F2-layer measured by FORMOSAT-3/COSMIC satellites in terms of GPS radio occultation technique and digisondes as manually scaled ionograms being provided by DIDBase (Digital Ionogram Database) with IRI. This study encompasses data from more than 40 locations for an extended period from January 2007 to December 2015. It utilises a subset of around 1000 very well matched (in terms of bottomside) FORMOSAT-3/COSMIC - Digisonde electron density profile pairs to compare the corresponding topside electron density profiles with IRI. The selection criteria for the electron density profile pairs, apart from coincidence of COSMIC and Digisonde electron density in the bottomside, is a collocation distance of less than 2.5o in terms of latitude and longtitude and 15 min maximum time difference in measuring NmF2 with the two techniques.

  1. Measurement of electron density in dual-energy x-ray CT with monochromatic x rays and evaluation of its accuracy.

    PubMed

    Tsunoo, Takanori; Torikoshi, Masami; Ohno, Yumiko; Uesugi, Kentaro; Yagi, Naoto

    2008-11-01

    Information on electron density is important for radiotherapy treatment planning in order to optimize the dose distribution in the target volume of a patient. At present, the electron density is derived from a computed tomography (CT) number measured in x-ray CT scanning; however, there are uncertainties due to the beam hardening effect and the method by which the electron density is converted from the CT number. In order to measure the electron density with an accuracy of +/-1%, the authors have developed dual-energy x ray CT using monochromatic x rays. They experimentally proved that the measured linear attenuation coefficients were only a few percent lower than the theoretical ones, which led to an accuracy within 2% for the electron density. There were three factors causing inaccuracy in the linear attenuation coefficient and the electron density: the influence of scattered radiation, the nonlinearity in the detector response function, and a theoretical process to derive the electron density from the linear attenuation coefficients. The linear attenuation coefficients of water were experimentally proved to differ by 1%-2% from the theoretical one even when the scattering effect was negligible. The nonlinearity of the response function played an important role in correcting the difference in the linear attenuation coefficient. Furthermore, the theoretical process used for deriving the electron density from the linear attenuation coefficients introduces about 0.6% deviation from the theoretical value into the resultant electron density. This deviation occurs systematically so that it can be corrected. The authors measured the electron densities for seven samples equivalent to soft tissue in dual-energy x-ray CT, and finally obtained them with an accuracy of around +/-1%.

  2. Measurement of atomic electric fields and charge densities from average momentum transfers using scanning transmission electron microscopy.

    PubMed

    Müller-Caspary, Knut; Krause, Florian F; Grieb, Tim; Löffler, Stefan; Schowalter, Marco; Béché, Armand; Galioit, Vincent; Marquardt, Dennis; Zweck, Josef; Schattschneider, Peter; Verbeeck, Johan; Rosenauer, Andreas

    2016-05-12

    This study sheds light on the prerequisites, possibilities, limitations and interpretation of high-resolution differential phase contrast (DPC) imaging in scanning transmission electron microscopy (STEM). We draw particular attention to the well-established DPC technique based on segmented annular detectors and its relation to recent developments based on pixelated detectors. These employ the expectation value of the momentum transfer as a reliable measure of the angular deflection of the STEM beam induced by an electric field in the specimen. The influence of scattering and propagation of electrons within the specimen is initially discussed separately and then treated in terms of a two-state channeling theory. A detailed simulation study of GaN is presented as a function of specimen thickness and bonding. It is found that bonding effects are rather detectable implicitly, e.g., by characteristics of the momentum flux in areas between the atoms than by directly mapping electric fields and charge densities. For strontium titanate, experimental charge densities are compared with simulations and discussed with respect to experimental artifacts such as scan noise. Finally, we consider practical issues such as figures of merit for spatial and momentum resolution, minimum electron dose, and the mapping of larger-scale, built-in electric fields by virtue of data averaged over a crystal unit cell. We find that the latter is possible for crystals with an inversion center. Concerning the optimal detector design, this study indicates that a sampling of 5mrad per pixel is sufficient in typical applications, corresponding to approximately 10×10 available pixels.

  3. Deferred electronic heterodyne moire deflectometry: A method for transient density fields measurement

    NASA Technical Reports Server (NTRS)

    Stricker, Josef

    1989-01-01

    Effects of spherical aberrations of the mirror used in the moire system on the angular resolution of the system are investigated. It is shown that the spherical aberrations may reduce significantly the performance of the conventional moire deflectometer. However, due to the heterodyne procedure, this is not the case with the heterodyne moire system. A moire system with a constant speed moving grating is demonstrated. It is shown that the system readout is linear and the system does not need calibration. In addition, the repeatability of the measurements is improved in this system as compared to the sinusoidally moving grating setup. The problem of the photographic plates alignment is solved by using a mechanical system in which the plate is held firmly throughout the experiment and accurately replaced after removing for photographic processing. The effect of a circular detector's aperture size on readout was tested. It is shown that the spatial phase variations, observed when scanning along a straight moire fringe, may considerably be reduced. At present we may say that both the on-line and the deferred heterodyne moire techniques may reliably be used. The errors of phase readings are 1 deg and 5 deg for the on-line and deferred methods. The total error due to subtraction of two readings at each position is, therefore, 1.4 deg and 7 deg, respectively. Further research for improving the deferred system is suggested.

  4. Nighttime D-region electron density measurements from ELF-VLF tweek radio atmospherics recorded at low latitudes

    NASA Astrophysics Data System (ADS)

    Maurya, A. K.; Veenadhari, B.; Singh, R.; Kumar, S.; Cohen, M.

    2012-12-01

    Dispersive atmospherics (tweeks) observed during 2010 simultaneously at two low latitude stations, Allahabad (geomagnetic lat., 16.79° N) and Nainital (geomagnetic lat. 20.48° N), have been utilized to estimate the nighttime D-region electron density at the ionospheric reflection height under the local nighttime propagation (21:00 - 02:00 LT or 15:30 - 20:30 UT). The analysis of simultaneously recorded tweeks at both the stations on five international quiet days during one month each from summer (June), winter (January) and equinox (March) seasons shows that the D-region electron density varies 21.5-24.5 cm-3 over the ionospheric reflection height of 85-95 km. The average values of Wait lower ionospheric parameters: ionospheric reference height h‧ and sharpness factor β are almost same during winter (86.1-85.9 km, 0.51-0.52 km-1) and equinox (85.6-85.7 km, 0.54 km-1) seasons. The values of h‧ and β during summer season are about 83.5 km and 0.60 km-1 at both stations. Overall, equivalent electron density profile obtained using tweek method shows lower values of electron density by about 5-60% than those obtained using IRI-2007 model and lower/higher by 2-68% than those obtained using rocket technique. The electron density estimated using all three techniques (tweek, IRI 2007, Rocket) is consistent in the altitude range of 82-98 km. The estimated geographic locations of causative lightnings of tweeks were matched with the locations and times of lightnings detected by the World-Wide Lightning Location Network (WWLLN). The WWLLN detected about 27.5% of causative lightnings of tweeks simultaneously observed at both the stations.

  5. Neurite density from magnetic resonance diffusion measurements at ultrahigh field: comparison with light microscopy and electron microscopy.

    PubMed

    Jespersen, Sune N; Bjarkam, Carsten R; Nyengaard, Jens R; Chakravarty, M Mallar; Hansen, Brian; Vosegaard, Thomas; Østergaard, Leif; Yablonskiy, Dmitriy; Nielsen, Niels Chr; Vestergaard-Poulsen, Peter

    2010-01-01

    Due to its unique sensitivity to tissue microstructure, diffusion-weighted magnetic resonance imaging (MRI) has found many applications in clinical and fundamental science. With few exceptions, a more precise correspondence between physiological or biophysical properties and the obtained diffusion parameters remain uncertain due to lack of specificity. In this work, we address this problem by comparing diffusion parameters of a recently introduced model for water diffusion in brain matter to light microscopy and quantitative electron microscopy. Specifically, we compare diffusion model predictions of neurite density in rats to optical myelin staining intensity and stereological estimation of neurite volume fraction using electron microscopy. We find that the diffusion model describes data better and that its parameters show stronger correlation with optical and electron microscopy, and thus reflect myelinated neurite density better than the more frequently used diffusion tensor imaging (DTI) and cumulant expansion methods. Furthermore, the estimated neurite orientations capture dendritic architecture more faithfully than DTI diffusion ellipsoids.

  6. The measurement of electron number density in helium micro hollow gas discharge using asymmetric He I lines

    NASA Astrophysics Data System (ADS)

    Jovović, J.; Šišović, N. M.

    2015-09-01

    The electron number density N e in helium micro hollow gas discharge (MHGD) is measured by means of optical emission spectroscopy (OES) techniques. The structure of MHGD is a gold-alumina-gold sandwich with 250 μm alumina thickness and 100 μm diameter hole. The electron temperature T e and gas temperature T g in the discharge is determined using the relative intensity of He I lines and {{\\text{N}}2}+≤ft({{\\text{B}}2}Σ\\text{u}+- {{X}2}Σ\\text{g}+\\right) R branch lines in the frame of BP technique, respectively. The simple procedure based on spectral line broadening theory was developed in MATLAB to generate synthetic neutral line asymmetric profiles. The synthetic profiles were compared with an experimental He I 447.1 nm and He I 492.2 nm line to obtain N e from the centre of a micro hollow gas discharge (MHGD) source in helium. The N e results were compared with N e values obtained from the forbidden-to-allowed (F/A) intensity ratio technique. The comparison confirmed higher N e determined using a F/A ratio due to large uncertainty of the method. Applying the fitting formula for a He I 492.2 nm line derived from computer simulation (CS) gives the same N e values as the one determined using the MATLAB procedure in this study. The dependence of N e on gas pressure and electric current is investigated as well.

  7. a High-Density Electron Beam and Quad-Scan Measurements at Pleiades Thomson X-Ray Source

    NASA Astrophysics Data System (ADS)

    Lim, J. K.; Rosenzweig, J. B.; Anderson, S. G.; Tremaine, A. M.

    2007-09-01

    A recent development of the photo-cathode injector technology has greatly enhanced the beam quality necessary for the creation of high density/high brightness electron beam sources. In the Thomson backscattering x-ray experiment, there is an immense need for under 20 micron electron beam spot at the interaction point with a high-intensity laser in order to produce a large x-ray flux. This has been demonstrated successfully at PLEIADES in Lawrence Livermore National Laboratory. For this Thomson backscattering experiment, we employed an asymmetric triplet, high remanence permanent-magnet quads to produce smaller electron beams. Utilizing highly efficient optical transition radiation (OTR) beam spot imaging technique and varying electron focal spot sizes enabled a quadrupole scan at the interaction zone. Comparisons between Twiss parameters obtained upstream to those parameter values deduced from PMQ scan will be presented in this report.

  8. a High-Density Electron Beam and Quad-Scan Measurements at Pleiades Thomson X-Ray Source

    NASA Astrophysics Data System (ADS)

    Lim, J. K.; Rosenzweig, J. B.; Anderson, S. G.; Tremaine, A. M.

    A recent development of the photo-cathode injector technology has greatly enhanced the beam quality necessary for the creation of high density/high brightness electron beam sources. In the Thomson backscattering x-ray experiment, there is an immense need for under 20 micron electron beam spot at the interaction point with a high-intensity laser in order to produce a large x-ray flux. This has been demonstrated successfully at PLEIADES in Lawrence Livermore National Laboratory. For this Thomson backscattering experiment, we employed an asymmetric triplet, high remanence permanent-magnet quads to produce smaller electron beams. Utilizing highly efficient optical transition radiation (OTR) beam spot imaging technique and varying electron focal spot sizes enabled a quadrupole scan at the interaction zone. Comparisons between Twiss parameters obtained upstream to those parameter values deduced from PMQ scan will be presented in this report.

  9. Development of frequency modulated continuous wave reflectometer for electron density profile measurement on the HL-2A tokamak

    SciTech Connect

    Zhong, W. L. Shi, Z. B.; Liu, Z. T.; Chen, W.; Jiang, M.; Li, J.; Cui, Z. Y.; Song, X. M.; Chen, L. Y.; Ding, X. T.; Liu, Yi; Yan, L. W.; Yang, Q. W.; Duan, X. R.; Huang, X. L.; Zou, X. L.

    2014-01-15

    The frequency modulated continuous wave reflectometer was developed for the first time on the HL-2A tokamak. The system utilizes a voltage controlled oscillator and an active multiplier for broadband coverage and detects as heterodyne mode. Three reflectometers have been installed and operated in extraordinary mode polarization on HL-2A to measure density profiles at low field side, covering the Q-band (33–50 GHz), V-band (50–75 GHz), and W-band (75–110 GHz). For density profile reconstruction from the phase shift of the probing wave, a corrected phase unwrapping method is introduced in this article. The effectiveness of the method is demonstrated. The density profile behavior of a fast plasma event is presented and it demonstrates the capability of the reflectometer. These diagnostics will be contributed to the routine density profile measurements and the plasma physics study on HL-2A.

  10. Electron-density profiles and plasma-drift measurements with digital ionosondes. Technical report, July 1987-June 1988

    SciTech Connect

    Reinisch, B.W.; Buchau, J.; Gamache, R.R.; Bibl, K.; Sales, G.S.

    1988-09-01

    Knowledge of the three-dimensional electron-density distribution and the plasma drift in the earth's ionosphere is needed for the radio communication engineer and the geophysicist. The combination of global models, e.g. the International Reference Ionosphere (IRI), modern digital ionosondes, and relatively powerful micro-computers provide the capabilities to overcome the limitations that have heretofore prevented real-time ionospheric specification and improved forecasting techniques. The developing network of digital ionosondes provides an improved ionogram data set. The cumbersome evaluation of electron density profiles (EDP), from the ionograms, has been eased with automatic ionogram scaling and related microcomputer-based algorithms for calculating EDPs. The purpose of this report is to summarize the evolving network of digital ionosondes based on the Digisonde 256 technology and to present techniques that have been developed for calculating electron-density profiles and determining the drift velocities. In addition, examples are presented to illustrate related data summaries that can be developed and tailored to the needs of the communication or radar-system manager and to the needs of the geophysicist involved in basic and applied research in solar-terrestrial physics.

  11. Initial measurements of plasma current and electron density profiles using a polarimeter/interferometer (POINT) for long pulse operation in EAST (invited).

    PubMed

    Liu, H Q; Qian, J P; Jie, Y X; Ding, W X; Brower, D L; Zou, Z Y; Li, W M; Lian, H; Wang, S X; Yang, Y; Zeng, L; Lan, T; Yao, Y; Hu, L Q; Zhang, X D; Wan, B N

    2016-11-01

    A double-pass, radially viewing, far-infrared laser-based POlarimeter-INTerferometer (POINT) system utilizing the three-wave technique has been implemented for diagnosing the plasma current and electron density profiles in the Experimental Advanced Superconducting Tokamak (EAST). POINT has been operated routinely during the most recent experimental campaign and provides continuous 11 chord line-integrated Faraday effect and density measurement throughout the entire plasma discharge for all heating schemes and all plasma conditions (including ITER relevant scenario development). Reliability of both the polarimetric and interferometric measurements is demonstrated in 25 s plasmas with H-mode and 102 s long-pulse discharges. Current density, safety factor (q), and electron density profiles are reconstructed using equilibrium fitting code (EFIT) with POINT constraints for the plasma core.

  12. Initial measurements of plasma current and electron density profiles using a polarimeter/interferometer (POINT) for long pulse operation in EAST (invited)

    NASA Astrophysics Data System (ADS)

    Liu, H. Q.; Qian, J. P.; Jie, Y. X.; Ding, W. X.; Brower, D. L.; Zou, Z. Y.; Li, W. M.; Lian, H.; Wang, S. X.; Yang, Y.; Zeng, L.; Lan, T.; Yao, Y.; Hu, L. Q.; Zhang, X. D.; Wan, B. N.

    2016-11-01

    A double-pass, radially viewing, far-infrared laser-based POlarimeter-INTerferometer (POINT) system utilizing the three-wave technique has been implemented for diagnosing the plasma current and electron density profiles in the Experimental Advanced Superconducting Tokamak (EAST). POINT has been operated routinely during the most recent experimental campaign and provides continuous 11 chord line-integrated Faraday effect and density measurement throughout the entire plasma discharge for all heating schemes and all plasma conditions (including ITER relevant scenario development). Reliability of both the polarimetric and interferometric measurements is demonstrated in 25 s plasmas with H-mode and 102 s long-pulse discharges. Current density, safety factor (q), and electron density profiles are reconstructed using equilibrium fitting code (EFIT) with POINT constraints for the plasma core.

  13. Design of a dispersion interferometer combined with a polarimeter to increase the electron density measurement reliability on ITER

    NASA Astrophysics Data System (ADS)

    Akiyama, T.; Sirinelli, A.; Watts, C.; Shigin, P.; Vayakis, G.; Walsh, M.

    2016-11-01

    A dispersion interferometer is a reliable density measurement system and is being designed as a complementary density diagnostic on ITER. The dispersion interferometer is inherently insensitive to mechanical vibrations, and a combined polarimeter with the same line of sight can correct fringe jump errors. A proof of the principle of the CO2 laser dispersion interferometer combined with the PEM polarimeter was recently conducted, where the phase shift and the polarization angle were successfully measured simultaneously. Standard deviations of the line-average density and the polarization angle measurements over 1 s are 9 × 1016 m-2 and 0.19°, respectively, with a time constant of 100 μs. Drifts of the zero point, which determine the resolution in steady-state operation, correspond to 0.25% and 1% of the phase shift and the Faraday rotation angle expected on ITER.

  14. Design of a dispersion interferometer combined with a polarimeter to increase the electron density measurement reliability on ITER.

    PubMed

    Akiyama, T; Sirinelli, A; Watts, C; Shigin, P; Vayakis, G; Walsh, M

    2016-11-01

    A dispersion interferometer is a reliable density measurement system and is being designed as a complementary density diagnostic on ITER. The dispersion interferometer is inherently insensitive to mechanical vibrations, and a combined polarimeter with the same line of sight can correct fringe jump errors. A proof of the principle of the CO2 laser dispersion interferometer combined with the PEM polarimeter was recently conducted, where the phase shift and the polarization angle were successfully measured simultaneously. Standard deviations of the line-average density and the polarization angle measurements over 1 s are 9 × 10(16) m(-2) and 0.19°, respectively, with a time constant of 100 μs. Drifts of the zero point, which determine the resolution in steady-state operation, correspond to 0.25% and 1% of the phase shift and the Faraday rotation angle expected on ITER.

  15. A new method to measure electron density and effective atomic number using dual-energy CT images

    NASA Astrophysics Data System (ADS)

    Ramos Garcia, Luis Isaac; Pérez Azorin, José Fernando; Almansa, Julio F.

    2016-01-01

    The purpose of this work is to present a new method to extract the electron density ({ρ\\text{e}} ) and the effective atomic number (Z eff) from dual-energy CT images, based on a Karhunen-Loeve expansion (KLE) of the atomic cross section per electron. This method was used to calibrate a Siemens Definition CT using the CIRS phantom. The predicted electron density and effective atomic number using 80 kVp and 140 kVp were compared with a calibration phantom and an independent set of samples. The mean absolute deviations between the theoretical and calculated values for all the samples were 1.7 %  ±  0.1 % for {ρ\\text{e}} and 4.1 %  ±  0.3 % for Z eff. Finally, these results were compared with other stoichiometric method. The application of the KLE to represent the atomic cross section per electron is a promising method for calculating {ρ\\text{e}} and Z eff using dual-energy CT images.

  16. A new method to measure electron density and effective atomic number using dual-energy CT images.

    PubMed

    Garcia, Luis Isaac Ramos; Azorin, José Fernando Pérez; Almansa, Julio F

    2016-01-07

    The purpose of this work is to present a new method to extract the electron density ([Formula: see text]) and the effective atomic number (Z eff) from dual-energy CT images, based on a Karhunen-Loeve expansion (KLE) of the atomic cross section per electron. This method was used to calibrate a Siemens Definition CT using the CIRS phantom. The predicted electron density and effective atomic number using 80 kVp and 140 kVp were compared with a calibration phantom and an independent set of samples. The mean absolute deviations between the theoretical and calculated values for all the samples were 1.7 %  ±  0.1 % for [Formula: see text] and 4.1 %  ±  0.3 % for Z eff. Finally, these results were compared with other stoichiometric method. The application of the KLE to represent the atomic cross section per electron is a promising method for calculating [Formula: see text] and Z eff using dual-energy CT images.

  17. Time-resolved electron temperature and electron density measurements in a nanosecond pulse filament discharge in H2-He and O2-He mixtures

    NASA Astrophysics Data System (ADS)

    Roettgen, A.; Shkurenkov, I.; Simeni Simeni, M.; Adamovich, I. V.; Lempert, W. R.

    2016-10-01

    Time evolution of electron density and electron temperature in a nanosecond pulse, diffuse filament electric discharge in H2-He and O2-He mixtures at a pressure of 100 Torr is studied by Thomson/pure rotational Raman scattering and kinetic modeling. The discharge is sustained between two spherical electrodes separated by a 1 cm gap and powered by high voltage pulses ~150 ns duration. Discharge energy coupled to the plasma filament 2-3 mm in diameter is 4-5 mJ/pulse, with specific energy loading of up to ~0.3 eV/molecule. At all experimental conditions, a rapid initial rise of electron temperature and electron density during the discharge pulse is observed, followed by the decay in the afterglow, over ~100 ns-1 µs. Electron density in the afterglow decays more rapidly as H2 or O2 fraction in the mixture is increased. In He/H2 mixtures, this is likely due to more rapid recombination of electrons in collisions with \\text{H}2+ and \\text{H}3+ ions, compared to recombination with \\text{He}2+ ions. In O2/He mixtures, electron density decay in the afterglow is affected by recombination with \\text{O}2+ and \\text{O}4+ ions, while the effect of three-body attachment is relatively minor. Peak electron number densities and electron temperatures are n e  =  (1.7-3.1) · 1014 cm-3 and T e  =  2.9-5.5 eV, depending on gas mixture composition. Electron temperature in the afterglow decays to approximately T e  ≈  0.3 eV, considerably higher compared to the gas temperature of T  =  300-380 K, inferred from O2 pure rotational Raman scattering spectra, due to superelastic collisions. The experimental results in helium and O2-He mixtures are compared with kinetic modeling predictions, showing good agreement.

  18. Dust storm and electron density in the equatorial D region ionosphere of Mars: Comparison with Earth's ionosphere from rocket measurements in Brazil

    NASA Astrophysics Data System (ADS)

    Haider, S. A.; Batista, I. S.; Abdu, M. A.; Muralikrishna, P.; Shah, Siddhi Y.; Kuroda, T.

    2015-10-01

    We report the first model result for the dust densities and electron densities in the D region ionosphere of Mars for aerosol particles of different sizes during a major dust storm that occurred in Martian Year (MY) 25 at low latitude. These calculations are made at latitude 10°S and solar longitudes (Ls) = 200°, 220°, 250°, and 280° for high, medium, low, and absence of dust storms, respectively. Four corresponding dust layers were found at 50 km, 50 km, 38 km, and 25 km during these events. During high dust storm period, the optical depth and dust density increased by a factor of ~20 from its normal condition. The electron densities estimated for the D region ionosphere of Mars for submicron sized dust particles are largest as compared to that estimated for larger particles. The electron density reduced by ~2 orders of magnitude during high dust storm. The estimated electron density in the clear atmosphere of Mars is compared with measurements of Earth's ionosphere at nearly the same geophysical condition.

  19. Model-independent measurement of the charge density distribution along an Fe atom probe needle using off-axis electron holography without mean inner potential effects

    NASA Astrophysics Data System (ADS)

    Migunov, V.; London, A.; Farle, M.; Dunin-Borkowski, R. E.

    2015-04-01

    The one-dimensional charge density distribution along an electrically biased Fe atom probe needle is measured using a model-independent approach based on off-axis electron holography in the transmission electron microscope. Both the mean inner potential and the magnetic contribution to the phase shift are subtracted by taking differences between electron-optical phase images recorded with different voltages applied to the needle. The measured one-dimensional charge density distribution along the needle is compared with a similar result obtained using model-based fitting of the phase shift surrounding the needle. On the assumption of cylindrical symmetry, it is then used to infer the three-dimensional electric field and electrostatic potential around the needle with ˜10 nm spatial resolution, without needing to consider either the influence of the perturbed reference wave or the extension of the projected potential outside the field of view of the electron hologram. The present study illustrates how a model-independent approach can be used to measure local variations in charge density in a material using electron holography in the presence of additional contributions to the phase, such as those arising from changes in mean inner potential and specimen thickness.

  20. F2 peak electron density at Millstone Hill and Hobart: Comparsion of theory and measurement at solar maximum

    NASA Technical Reports Server (NTRS)

    Richards, P. G.; Torr, D. G.; Reinisch, B. W.; Gamache, R. R.; Wilkinson, P. J.

    1994-01-01

    This paper compares the observed behavior of the (F2) layer of the ionosphere at Millstone Hill and Hobart with calculations from the field line interhemispheric plasma (FLIP) model for solar maximum, solstice conditions in 1990. During the study period the daily F(sub 10.7) index varied by more than a factor of 2 (123 to 280), but the 81-day mean F(sub 10.7) (F(sub 10.7 A)) was almost constant near 190. Calculations were performed with and without the effects of vibrationally excited N2 (N(sup *)(sub 2) which affects the loss rate of atomic oxygen ions. In the case without N(sup *)(sub 2) there is generally good agreement between the model and measurement for the daytime, peak density of the F region (NmF2). Both the model and the measurement show a strong seasonal anomaly with the winter noon densities a factor of 3 to 4 greater than the summer noon densities at Millstone Hill and a factor of 2 greater at Hobart. The seasonal anomaly in the model is caused by changes in the neutral composition as given by the mass spectrometer and incoherent scatter (MSIS) 86 neutral density model. There is generally little or no increase in the observed noon NmF2 as a function of daily F(sub 10.7) except at Millstone Hill in winter. In contrast to the generally good agreement between model and data at noon, the model badly underestimates the density at night at Millstone Hill at all seasons. At Hobart the model reproduces the nighttime density variations well in both winter and summer. The international reference ionosphere (IRI) model generally provides a good representation of the average behavior of noon NmF2 and hmF2 but because the data show a lot of day-to-day variability, there are often large differences. The FLIP model is able to reproduce this variability when hmF2 is specified. The IRI model peak densities are better than the FLIP densities at night, but the IRI model does not represent the Millstone Hill summer data very well at night in 1990.

  1. Nuclear cusps in the HSF electron density

    NASA Astrophysics Data System (ADS)

    Cioslowski, Jerzy; Challacombe, Matt

    1994-07-01

    The Hiller-Sucher-Feinberg (HSF) identity provides an alternative definition for the electron density. The behavior of the HSF electron density in the vicinity of nuclei is analyzed. It is shown that the HSF density possesses nuclear cusps at which its gradient is discontinuous. The discontinuities in the HSF density gradient satisfy a simple equation analogous to Kato's electron-nuclear cusp condition. However, in contrast to Kato's condition, the electron-nuclear cusp condition is satisfied by HSF densities originating from both exact and approximate electronic wavefunctions. Several numerical examples are presented to illustrate this property of the HSF electron density.

  2. Time-resolved electron density measurements in PF-1000 device by means of the Mechelle® 900 optical spectrometer

    NASA Astrophysics Data System (ADS)

    Skladnik-Sadowska, E.; Sadowski, M. J.; Mallnowski, K.; Tsarenko, A. V.; Scholz, M.; Paduch, M.; Tomaszewski, K.

    2004-03-01

    The report presents the main results of the recent spectroscopic investigations of plasma produced within the PF-1000 facility. That experimental device was operated mostly with the pure deuterium filling. The initial pressure was 5 hPa D2 or H2 and the charging voltage of a capacity bank was 28 kV. The electron density was estimated by means of three different techniques: the linear Stark broadening of the Balmer series, the quadratic Stark broadening of copper and carbon spectral lines (including the lines of multi-charged ions), and using the Inglis-Teller correlation for a shift of the boundary serial. At all the stages of the data processing there was applied a convenient and effective software of the GRAMS-32 type (attached to the MECHELLE®900 spectrometer). A critical evaluation of the obtained results, taking into consideration their accuracy and reliability, has been performed.

  3. F{sub 2} peak electron density at Millstone Hill and Hobart: Comparison of theory and measurement at solar maximum

    SciTech Connect

    Richards, P.G.; Torr, D.G.; Reinisch, B.W.

    1994-08-01

    This paper compares the observed behavior of the F{sub 2} layer of the ionosphere at Millstone Hill and Hobart with calculations from the field line interhemispheric plasma (FLIP) model for solar maximum, solstice conditions in 1990. During the study period the daily F{sub 10.7} index varied by more than a factor of 2 (123 to 280), but the 81-day mean F{sub 10.7} (F{sub 10.7A}) was almost constant near 190. Calculations were performed with and without the effects of vibrationally excited N{sub 2} (N{sub 2}*) which affects the loss rate of atomic oxygen ions. In the case without N{sub 2}* there is generally good agreement between the model and measurement for the daytime, peak density of the F region (NmF{sub 2}). Both the model and the measurement show a strong seasonal anomaly with the winter noon densities a factor of 3 to 4 greater than the summer noon densities at Millstone Hill and a factor of 2 greater at Hobart. The seasonal anomaly in the model is caused by changes in the neutral composition as given by the mass spectrometer and incoherent scatter (MSIS) 86 neutral density model. While N{sub 2}* worsens the model-data comparison at Millstone Hill, it does bring the model seasonal density ratio into better agreement with the data and also improves the agreement at Hobart. Although the 1990 daytime ionosphere can be well modeled without N{sub 2}*, it may still be important for high levels of solar and magnetic activity. There is a very close relationship between the height at which peak density occurs hmF{sub 2} variation and the NmF{sub 2} variation with F{sub 10.7} in summer at Millstone Hill. The international reference ionosphere (IRI) model generally provides a good representation of the average behavior of noon NmF{sub 2} and hmF{sub 2} but because the data show a lot of day-to-day variability, there are often large differences. The FLIP model is able to reproduce this variability when hmF{sub 2} is specified. 28 refs., 16 figs.

  4. Departures from local thermodynamic equilibrium in cutting arc plasmas derived from electron and gas density measurements using a two-wavelength quantitative Schlieren technique

    SciTech Connect

    Prevosto, L.; Mancinelli, B.; Artana, G.; Kelly, H.

    2011-03-15

    A two-wavelength quantitative Schlieren technique that allows inferring the electron and gas densities of axisymmetric arc plasmas without imposing any assumption regarding statistical equilibrium models is reported. This technique was applied to the study of local thermodynamic equilibrium (LTE) departures within the core of a 30 A high-energy density cutting arc. In order to derive the electron and heavy particle temperatures from the inferred density profiles, a generalized two-temperature Saha equation together with the plasma equation of state and the quasineutrality condition were employed. Factors such as arc fluctuations that influence the accuracy of the measurements and the validity of the assumptions used to derive the plasma species temperature were considered. Significant deviations from chemical equilibrium as well as kinetic equilibrium were found at elevated electron temperatures and gas densities toward the arc core edge. An electron temperature profile nearly constant through the arc core with a value of about 14000-15000 K, well decoupled from the heavy particle temperature of about 1500 K at the arc core edge, was inferred.

  5. A Comparison of Electron Density Profiles Derived from the Low Resolution Airglow and Aurora Spectrograph (LORAAS) Ultraviolet Measurements: Resolution of the 911 Å Conundrum

    NASA Astrophysics Data System (ADS)

    Dymond, K.; Budzien, S. A.; Coker, C.; Nicholas, A. C.; Stephan, A. W.; Bishop, R. L.; Christensen, A. B.; Hecht, J. H.; Straus, P. R.

    2010-12-01

    Previous measurements of the 911 Å emission made by sounding rockets, at altitude less than 320 km, indicated that the emission was either very weak or non-existent. Newer measurements made by the Remote Atmospheric and Ionospheric Detection System (RAIDS) currently in operation aboard the International Space Station, at an altitude of 340 km, show the same behavior. Yet, satellite-based measurements made at altitudes above 800 km showed the emission to be present and strong enough to be accurately measured and inverted; those inversions were validated against ionosonde measurements and demonstrated the possibility of using the 911 Å emission for daytime ionospheric sensing. So the conundrum is: why do measurements made at lower altitudes (< 350 km) indicate weak or non-existent emission while satellite measurements at higher altitudes (>800 km) show the presence of the emission at the expected level? We present our measurements of the daytime and nighttime electron density derived by analysis of the O I 1356 and O I 911 Å altitude profiles measured by the Low Resolution Airglow and Aurora Spectrograph (LORAAS) instrument launched aboard the Advanced Research and Global Observation Satellite (ARGOS), which operated between mid-May 1999 and April 2002. We compare the retrieved electron density profiles inferred from the limb intensities of the ultraviolet emissions to peak heights and peak densities measured during ionosonde overflights. We show that the 911 Å emission is strongly affected by the height of the ionosphere and show that this is consistent with absorption of the 911 Å by atomic oxygen. Model results are presented showing that the RAIDS and sounding rocket measurements can be explained by this absorption.

  6. Measurements of electron density and temperature profiles in plasma produced by Nike KrF laser for laser plasma instability research

    NASA Astrophysics Data System (ADS)

    Oh, Jaechul; Weaver, J. L.; Karasik, M.; Chan, L. Y.

    2015-08-01

    A grid image refractometer (GIR) has been implemented at the Nike krypton fluoride laser facility of the Naval Research Laboratory. This instrument simultaneously measures propagation angles and transmissions of UV probe rays (λ = 263 nm, Δt = 10 ps) refracted through plasma. We report results of the first Nike-GIR measurement on a CH plasma produced by the Nike laser pulse (˜1 ns FWHM) with the intensity of 1.1 × 1015 W/cm2. The measured angles and transmissions were processed to construct spatial profiles of electron density (ne) and temperature (Te) in the underdense coronal region of the plasma. Using an inversion algorithm developed for the strongly refracted rays, the deployed GIR system probed electron densities up to 4 × 1021 cm-3 with the density scale length of 120 μm along the plasma symmetry axis. The resulting ne and Te profiles are verified to be self-consistent with the measured quantities of the refracted probe light.

  7. Simulation, measurement, and emulation of photovoltaic modules using high frequency and high power density power electronic circuits

    NASA Astrophysics Data System (ADS)

    Erkaya, Yunus

    The number of solar photovoltaic (PV) installations is growing exponentially, and to improve the energy yield and the efficiency of PV systems, it is necessary to have correct methods for simulation, measurement, and emulation. PV systems can be simulated using PV models for different configurations and technologies of PV modules. Additionally, different environmental conditions of solar irradiance, temperature, and partial shading can be incorporated in the model to accurately simulate PV systems for any given condition. The electrical measurement of PV systems both prior to and after making electrical connections is important for attaining high efficiency and reliability. Measuring PV modules using a current-voltage (I-V) curve tracer allows the installer to know whether the PV modules are 100% operational. The installed modules can be properly matched to maximize performance. Once installed, the whole system needs to be characterized similarly to detect mismatches, partial shading, or installation damage before energizing the system. This will prevent any reliability issues from the onset and ensure the system efficiency will remain high. A capacitive load is implemented in making I-V curve measurements with the goal of minimizing the curve tracer volume and cost. Additionally, the increase of measurement resolution and accuracy is possible via the use of accurate voltage and current measurement methods and accurate PV models to translate the curves to standard testing conditions. A move from mechanical relays to solid-state MOSFETs improved system reliability while significantly reducing device volume and costs. Finally, emulating PV modules is necessary for testing electrical components of a PV system. PV emulation simplifies and standardizes the tests allowing for different irradiance, temperature and partial shading levels to be easily tested. Proper emulation of PV modules requires an accurate and mathematically simple PV model that incorporates all known

  8. Electron Density and Two-Channel Neutron Emission Measurements in Steady-State Spherical Inertial-Electrostatically Confined Plasmas, with Review of the 1-D Kinetic Model

    NASA Technical Reports Server (NTRS)

    Dobson, Chris C.; Hrbud, Ivana

    2004-01-01

    Electron density measurements have been made in steady-state plasmas in a spherical inertial electrostatic confinement (IEC) discharge using microwave interferometry. Plasma cores interior to two cathodes, having diameters of 15 and 23 cm, respectively, were probed over a transverse range of 10 cm with a spatial resolution of about 1.4 cm for buffer gas pressures from 0.2 to 6 Pa in argon and deuterium. The transverse profiles are generally flat, in some cases with eccentric symmetric minima, and give mean densities of from approx. = 0.4 to 7x 10(exp 10)/cu cm, the density generally increasing with the neutral gas pressure. Numerical solutions of the 1-D Poisson equation for EC plasmas are reviewed and energy distribution functions are identified which give flat transverse profiles. These functions are used with the plasma approximation to obtain solutions which also give densities consistent with the measurements, and a double potential well solution is obtained which has minima qualitatively similar to those observed. Explicit consideration is given to the compatibility of the solutions interior and exterior to the cathode, and to grid transparency. Deuterium fusion neutron emission rates were also measured and found to be isotropic, to within the measurement error, over two simultaneous directions. Anisotropy was observed in residual emissions during operation with non-fusing hydrogen-1. The deuterium rates are consistent with predictions from the model.

  9. Electron Density and Two-Channel Neutron Emission Measurements in Steady-State Spherical Inertial-Electrostatically Confined Plasmas, with Review of the One-Dimensional Kinetic Model

    NASA Technical Reports Server (NTRS)

    Dobson, Chris C.; Hrbud, Ivana

    2004-01-01

    Electron density measurements have been made in steady-state plasmas in a spherical inertial electrostatic confinement (IEC) discharge using microwave interferometry. Plasma cores interior to two cathodes, having diameters of 15 and 23 cm, respectively, were probed over a transverse range of 10 cm with a spatial resolution of about 1.4 cm for buffer gas pressures from 0.2 to 6 Pa in argon and deuterium. The transverse profiles are generally flat, in some cases with eccentric symmetric minima, and give mean densities of from approx. = 0.4 to 7 x 10(exp 10)/cu cm, the density generally increasing with the neutral gas pressure. Numerical solutions of the one-dimensional Poisson equation for IEC plasmas are reviewed and energy distribution functions are identified which give flat transverse profiles. These functions are used with the plasma approximation to obtain solutions which also give densities consistent with the measurements, and a double potential well solution is obtained which has minima qualitatively similar to those observed. Explicit consideration is given to the compatibility of the solutions interior and exterior to the cathode, and to grid transparency. Deuterium fusion neutron emission rates were also measured and found to be isotropic, to within the measurement error, over two simultaneous directions. Anisotropy was observed in residual emissions during operation with nonfusing hydrogen- 1. The deuterium rates are consistent with predictions from the model.

  10. Electron (charge) density studies of cellulose models

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Introductory material first describes electron density approaches and demonstrates visualization of electron lone pairs and bonding as concentrations of electron density. Then it focuses on the application of Bader’s Quantum Theory of Atoms-in-Molecules (AIM) to cellulose models. The purpose of the ...

  11. Pulsed HF radiowave absorption measurements at 2.1 MHZ. over Delhi under quiet and solar flare conditions and related electron density height profiles

    NASA Astrophysics Data System (ADS)

    Balachandra Swamy, A. C.

    EXTENDED ABSTRACT Pulsed HF radiowave absorption measurements at 2.1 MHZ. over Delhi under quiet and solar flare conditions and related electron density height profiles A.C.Balachandra swmay & Late C.S.G.K. Setty Absorption of radio waves in the ionosphere is of great practical importance for radio communication and navigation systems. The first attempt to measure the absolute magnitude of the radiowave absorption were made by appletion and Ratcliffe (1930) using the frequency change method for medium frequency waves reflected from the E-region. They concluded from their experiment that the main part of the attenuation occurred below the reflection level and named the absorption region, D-region of the ionosphere. One of the basic properties of the ionosphere is the absorption of high Frequency Radiowaves. HF radiowave absorption results mainly from collisions between electrons (which are set into forced oscillations by the electric field of the wave) and neutral air particles, the RF energy abstracted from the wave being converted into thermal energy. The radiowave absorption in the ionosphere depends on electron density and collision frequency. The most important absorbing regions are the D-region and the lower E-region (50-100 Km.) The regular diurnal variation of the electron density in this height range is caused mainly by the changes in the depth of penetration of solar XUV radiations with solar zenith angle under quiet solar conditions. In 1937 Dellinger J.H.identified fade outs in high frequency radio circuits as due to abnormal ionospheric absorption associated with solar flares. The onset of the fade out was usually rapid and the duration was typically tens of minutes like that of the visible flare, because of the sudden onset, the immediate effects of solar flares are known collectively as sudden Ionospheric Disturbances (STD). The phenomenon discovered by Dellinger is usually called a short Wave Fadeout(SWF). Since the SWF is due to abnormal absorption

  12. The Reliability of Density Measurements.

    ERIC Educational Resources Information Center

    Crothers, Charles

    1978-01-01

    Data from a land-use study of small- and medium-sized towns in New Zealand are used to ascertain the relationship between official and effective density measures. It was found that the reliability of official measures of density is very low overall, although reliability increases with community size. (Author/RLV)

  13. Development of a spectroscopic technique for simultaneous magnetic field, electron density, and temperature measurements in ICF-relevant plasmas (Conference Presentation)

    NASA Astrophysics Data System (ADS)

    Dutra, Eric C.; Covington, Aaron M.; Darling, Timothy; Mancini, Roberto C.; Haque, Showera; Angermeier, William A.

    2016-09-01

    Visible spectroscopic techniques are often used in plasma experiments to measure B-field induced Zeeman splitting, electron densities via Stark broadening and temperatures from Doppler broadening. However, when electron densities and temperatures are sufficiently high, the broadening of the Stark and Doppler components can dominate the emission spectra and obscure the Zeeman component. In this research, we are developing a time-resolved multi-axial technique for measuring the Zeeman, Stark, and Doppler broadened line emission of dense magnetized plasmas for Z-pinch and Dense Plasma Focus (DPF) accelerators. The line emission is used to calculate the electron densities, temperatures, and B-fields. In parallel, we are developing a line-shape modeling code that incorporates the broadening effects due to Stark, Doppler, and Zeeman effects for dense magnetized plasma. Experiments conducted at the University of Nevada (Reno) at the Nevada Terawatt Facility (NTF) using the 1 MA Z-pinch (Zebra). The research explored the response of Al III doublet, 4p 2P3/2 to 4s 2S1/2 and 4p 2P1/2 to 4s 2S1/2 transitions. Optical light emitted from the pinch is fiber coupled to high-resolution spectrometers. The dual spectrometers are coupled to two high-speed visible streak cameras to capture time-resolved emission spectra from the experiment. The data reflects emission spectra from 100 ns before the current peak to 100 ns after the current peak, where the current peak is approximately the time at which the pinch occurs. The Al III doublet is used to measure Zeeman, Stark, and Doppler broadened emission. The line emission is then used to calculate the temperature, electron density, and B-fields. The measured quantities are used as initial parameters for the line shape code to simulate emission spectra and compare to experimental results. Future tests are planned to evaluate technique and modeling on other material wire array, gas puff, and DPF platforms. This work was done by National

  14. Electron measurement in PHENIX

    SciTech Connect

    Akiba, Y.

    1995-07-15

    Electron Measurement in PHENIX detector at RHIC is discussed. The yield and S/N ratio at vector meson peaks ({phi}, {omega}, {rho}{sup o}, and J/{psi}) are evaluated. The electrons from open charm decay, and its consequence to the di-electron measurements is discussed.

  15. Teaching Chemistry with Electron Density Models.

    ERIC Educational Resources Information Center

    Shusterman, Gwendolyn P.; Shusterman, Alan J.

    1997-01-01

    Describes a method for teaching electronic structure and its relevance to chemical phenomena that relies on computer-generated three-dimensional models of electron density distributions. Discusses the quantum mechanical background needed and presents ways of using models of electronic ground states to teach electronic structure, bonding concepts,…

  16. Measuring the magnetic-field-dependent chemical potential of a low-density three-dimensional electron gas in n -GaAs and extracting its magnetic susceptibility

    NASA Astrophysics Data System (ADS)

    Roy Choudhury, Aditya N.; Venkataraman, V.

    2016-01-01

    We report the magnetic-field-dependent shift of the electron chemical potential in bulk, n -type GaAs at room temperature. A transient voltage of ˜100 μ V was measured across a Au-Al2O3 -GaAs metal-oxide-semiconductor capacitor in a pulsed magnetic field of ˜6 T . Several spurious voltages larger than the signal that had plagued earlier researchers performing similar experiments were carefully eliminated. The itinerant magnetic susceptibility of GaAs is extracted from the experimentally measured data for four different doping densities, including one as low as 5 ×1015cm-3 . Though the susceptibility in GaAs is dominated by Landau-Peierls diamagnetism, the experimental technique demonstrated can be a powerful tool for extracting the total free carrier magnetization of any electron system. The method is also virtually independent of the carrier concentration and is expected to work better in the nondegenerate limit. Such experiments had been successfully performed in two-dimensional electron gases at cryogenic temperatures. However, an unambiguous report on having observed this effect in any three-dimensional electron gas has been lacking. We highlight the 50 year old literature of various trials and discuss the key details of our experiment that were essential for its success. The technique can be used to unambiguously yield only the itinerant part of the magnetic susceptibility of complex materials such as magnetic semiconductors and hexaborides, and thus shed light on the origin of ferromagnetism in such systems.

  17. Ionospheric E-region electron density and neutral atmosphere variations

    NASA Technical Reports Server (NTRS)

    Stick, T. L.

    1976-01-01

    Electron density deviations from a basic variation with the solar zenith angle were investigated. A model study was conducted in which the effects of changes in neutral and relative densities of atomic and molecular oxygen on calculated electron densities were compared with incoherent scatter measurements in the height range 100-117 km at Arecibo, Puerto Rico. The feasibility of determining tides in the neutral atmosphere from electron density profiles was studied. It was determined that variations in phase between the density and temperature variation and the comparable magnitudes of their components make it appear improbable that the useful information on tidal modes can be obtained in this way.

  18. Instrumentation for bone density measurement

    NASA Technical Reports Server (NTRS)

    Meharg, L. S.

    1968-01-01

    Measurement system evaluates the integrated bone density over a specific cross section of bone. A digital computer converts stored bone scan data to equivalent aluminum calibration wedge thickness, and bone density is then integrated along the scan by using the trapezoidal approximation integration formula.

  19. Electron density studies of methyl cellobioside

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Experimental X-ray diffraction crystallography determines the variations in electron density that result from the periodic array of atoms in a crystal. Normally, the positions and type of atom are determined from the electron density based on an approximation that the atoms are spherical. However, t...

  20. Bulk Density Measurements of Meteorites

    NASA Astrophysics Data System (ADS)

    Wilkison, S. L.; Robinson, M. S.

    1999-03-01

    We present density measurements of meteorites detailing the precision and errors associated with the modified Archimedian method of Consolmagno and Britt. We find that the method is accurate to better than 1%.

  1. Measurements of line-averaged electron density of pulsed plasmas using a He-Ne laser interferometer in a magnetized coaxial plasma gun device

    NASA Astrophysics Data System (ADS)

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

    2012-10-01

    In next step of fusion devices such as ITER, lifetime of plasma-facing materials (PFMs) is strongly affected by transient heat and particle loads during type I edge localized modes (ELMs) and disruption. To clarify damage characteristics of the PFMs, transient heat and particle loads have been simulated by using a plasma gun device. We have performed simulation experiments by using a magnetized coaxial plasma gun (MCPG) device at University of Hyogo. The line-averaged electron density measured by a He-Ne interferometer is 2x10^21 m-3 in a drift tube. The plasma velocity measured by a time of flight technique and ion Doppler spectrometer was 70 km/s, corresponding to the ion energy of 100 eV for helium. Thus, the ion flux density is 1.4x10^26 m-2s-1. On the other hand, the MCPG is connected to a target chamber for material irradiation experiments. It is important to measure plasma parameters in front of target materials in the target chamber. In particular, a vapor cloud layer in front of the target material produced by the pulsed plasma irradiation has to be characterized in order to understand surface damage of PFMs under ELM-like plasma bombardment. In the conference, preliminary results of application of the He-Ne laser interferometer for the above experiment will be shown.

  2. Morphology of high-latitude plasma density perturbations as deduced from the total electron content measurements onboard the Swarm constellation

    NASA Astrophysics Data System (ADS)

    Park, Jaeheung; Lühr, Hermann; Kervalishvili, Guram; Rauberg, Jan; Stolle, Claudia; Kwak, Young-Sil; Lee, Woo Kyoung

    2017-01-01

    In this study, we investigate the climatology of high-latitude total electron content (TEC) variations as observed by the dual-frequency Global Navigation Satellite Systems (GNSS) receivers onboard the Swarm satellite constellation. The distribution of TEC perturbations as a function of geographic/magnetic coordinates and seasons reasonably agrees with that of the Challenging Minisatellite Payload observations published earlier. Categorizing the high-latitude TEC perturbations according to line-of-sight directions between Swarm and GNSS satellites, we can deduce their morphology with respect to the geomagnetic field lines. In the Northern Hemisphere, the perturbation shapes are mostly aligned with the L shell surface, and this anisotropy is strongest in the nightside auroral (substorm) and subauroral regions and weakest in the central polar cap. The results are consistent with the well-known two-cell plasma convection pattern of the high-latitude ionosphere, which is approximately aligned with L shells at auroral regions and crossing different L shells for a significant part of the polar cap. In the Southern Hemisphere, the perturbation structures exhibit noticeable misalignment to the local L shells. Here the direction toward the Sun has an additional influence on the plasma structure, which we attribute to photoionization effects. The larger offset between geographic and geomagnetic poles in the south than in the north is responsible for the hemispheric difference.

  3. Electron densities of three B12 vitamins.

    PubMed

    Mebs, Stefan; Henn, Julian; Dittrich, Birger; Paulmann, Carsten; Luger, Peter

    2009-07-23

    The electron densities of the three natural B(12)-vitamins, two of them being essential cofactors for animal life, were determined in a procedure combining high-order X-ray data collection at low to very low temperatures with high-level density functional calculations. In a series of extensive experimental attempts, a high-order data set of adenosylcobalamin (AdoCbl) could be collected to a resolution of sin theta/lambda = 1.00 A(-1) at 25 K. This modification contains only minor disorder at the solvent bulk. For methylcobalamin (MeCbl), only a severely disordered modification was found (sin theta/lambda = 1.00 A(-1), 100 K, measured with synchrotron radiation). The already published data set of cyanocobalamin (CNCbl) (sin theta/lambda = 1.25 A(-1), 100 K) was reintegrated to guarantee similar treatment of the three compounds and cut to sin theta/lambda = 1.11 A(-1) to obtain a higher degree of completeness and redundancy. On the basis of these accurate experimental geometries of AdoCbl, MeCbl, and CNCbl, state-of-the-art density functional calculations, single-point calculations, and geometry optimizations were performed on model compounds at the BP86/TZVP level of theory to evaluate the electronic differences of the three compounds. AdoCbl and MeCbl are known to undergo different reaction paths in the body. Thus, the focus was directed toward the characterization of the dative Co-C(ax) and Co-N(ax) bonds, which were quantifed by topological parameters, including energy densities; the source function including local source; and the electron localizability indicator (ELI-D), respectively. The source function reveals the existence of delocalized interactions between the corrin macrocycle and the axial ligands. The ELI-D indicates unsaturated Co-C(ax) bonding basins for the two biochemically active cofactors, but not for CNCbl, where a population of 2.2e is found. This may be related to significant pi-backbonding, which is supported by the delocalization index, delta

  4. Measuring liquid density using Archimedes' principle

    NASA Astrophysics Data System (ADS)

    Hughes, Stephen W.

    2006-09-01

    A simple technique is described for measuring absolute and relative liquid density based on Archimedes' principle. The technique involves placing a container of the liquid under test on an electronic balance and suspending a probe (e.g. a glass marble) attached to a length of line beneath the surface of the liquid. If the volume of the probe is known, the density of liquid is given by the difference between the balance reading before and after immersion of the probe divided by the volume of the probe. A test showed that the density of water at room temperature could be measured to an accuracy and precision of 0.01 ± 0.1%. The probe technique was also used to measure the relative density of milk, Coca-Cola, fruit juice, olive oil and vinegar.

  5. Density Measurements of Be Shells

    SciTech Connect

    Cook, R C

    2005-02-15

    The purpose of this memo is to lay out the uncertainties associated with the measurement of density of Be ablators by the weigh and volume method. I am counting on the readers to point out any faulty assumptions about the techniques or uncertainties associated with them. Based on the analysis presented below we should expect that 30 {micro}m thick shells will have an uncertainty in the measured density of about 2% of the value, coming more or less equally from the mass and volume measurement. The uncertainty is roughly inversely proportional to the coating thickness, thus a 60 {micro}m walled shell would result in a 1% uncertainty in the density.

  6. EISCAT (European Incoherent Scatter Radar) Electron Density Studies.

    DTIC Science & Technology

    1987-09-08

    lists the corresponding measurements of electron content made by HILAT and calculated from SPI03 measurements for each of the 7 coincident runs. The...TEC measured by HILAT and TEC calculated from EISCAT measurements, the HILAT values being always larger than those from EISCAT. The measurements...HILAT results could be due to several factors. The EISCAT value was calculated by integrating electron density over the range gates 184 km to 746.5

  7. Polar cap electron densities from DE 1 plasma wave observations

    NASA Technical Reports Server (NTRS)

    Persoon, A. M.; Gurnett, D. A.; Shawhan, S. D.

    1983-01-01

    Electric-field-spectum measurements from the plasma-wave instrument on the Dynamics Explorer 1 spacecraft are used to study the local electron density at high altitudes in the northern polar-cap region. The electron density is determined from the upper cutoff of whistler-mode radiation at the electron plasma frequency. Median density values over the polar cap at L greater than 10 are found to vary from 35.2 + or - 8.5 cu cm at 2.1 earth radii to 0.99 + or - 0.51 cu cm at 4.66 earth radii. The steady-state radial-outflow model is examined for consistency with the observed density profile. A power-law fit to the radial variation of the electron density yields an exponent of - 3.85 + or - 0.32, which for the radial-outflow model implies a flow velocity increasing nearly linearly with incresing radial distance. Comparison of the observed electron densities with theoretical polar-wind densities yields consistent results up to 2.8 earth radii. A comparison of the observed electron densities with low-altitude density profiles from the Alouette II and ISIS 1 spacecraft illustrates transitions in the slope of the profile at 1.16 earth radii and between 1.55 and 2.0 earth radii. The changes in the density profile suggest that changes occur in the basic radial-transport processes at these altitudes.

  8. LIF Measurements on an Atomic Helium Beam in the Edge of a Fusion Plasma--possible derivation of the electron density

    SciTech Connect

    Krychowiak, M.; Koenig, R.; Klinger, T.; Mertens, Ph.; Schweer, B.; Brezinsek, S.; Schmitz, O.; Samm, U.; Brix, M.

    2008-03-19

    Local values of the electron density and temperature in the edge of a fusion plasma can be derived with high space and time resolution by the use of line radiation of atomic helium beams. The accuracy of this method is mainly limited by the uncertainties in the collisional-radiative model which is needed in order to obtain both plasma parameters from the measured relative intensities of atomic helium lines. Combination of a helium beam with a pulsed high-power laser provides a possibility of n{sub e} measurement which does not require a detailed knowledge of the collisional-radiative model. The method relies on resonant laser pumping of some levels and analyzing their fluorescence after the end of the laser pulse. Such measurements were already performed in low temperature plasmas with some content of atomic helium [1,2,3]. In this paper, we discuss the applicability of this method in the fusion edge plasma in the density range of {approx}10{sup 12}-10{sup 13} cm{sup -3} when exciting helium atoms with a laser at the wavelength of {lambda} = 388.9 nm tuned to the triplet transition 2{sup 3}S-vector3{sup 3}P deg. and observing the fluorescence light at the laser wavelength and at {lambda} = 587.6 nm(3{sup 3}D-vector2{sup 3}P deg.). A first test measurement at the TEXTOR tokamak in Juelich performed by use of an excimer-pumped dye laser in connection with a thermal helium beam is shown and discussed.

  9. Electron cyclotron emission as a density fluctuation diagnostic

    SciTech Connect

    Lynn, A.G.; Phillips, P.E.; Hubbard, A.

    2004-10-01

    A new technique for measuring density fluctuations using a high-resolution heterodyne electron cyclotron emission (ECE) radiometer has been developed. Although ECE radiometry is typically used for electron temperature measurements, the unique viewing geometry of this system's quasioptical antenna has been found to make the detected emission extremely sensitive to refractive effects under certain conditions. This sensitivity gives the diagnostic the ability to measure very low levels of density fluctuations in the core of Alcator C-Mod tokamak. The refractive effects have been modeled using ray-tracing methods, allowing estimates of the density fluctuation magnitude and spatial localization.

  10. Ionospheric density enhancement during relativistic electron precipitation

    NASA Technical Reports Server (NTRS)

    Foster, J. C.; Doupnik, J. R.; Stiles, G. S.

    1980-01-01

    The temporal evolution of the ionospheric density enhancement produced by a widespread relativistic electron precipitation (REP) has been observed with the Chatanika Radar. The REP was associated with a substorm particle energization event, and both the ionospheric absorption and density perturbation exhibited an approximately 90 min periodicity associated with the particles' longitudinal drift. A 80-keV characteristic energy for the precipitating electrons is deduced from ground-based and satellite data. At the maximum of the event, electrons deposited approximately 50 ergs/sq cm per sec in the ionosphere, producing a peak density of 500,000/cu cm at 89 km altitude. At that time the radar observed densities greater than 100,000/cu cm between 70 km and 110 km altitude and riometer absorption at 30 MHz was approximately 12 db.

  11. Picosecond imaging of low-density plasmas by electron deflectometry.

    PubMed

    Centurion, M; Reckenthaeler, P; Krausz, F; Fill, E E

    2009-02-15

    We have imaged optical-field ionized plasmas with electron densities as low as 10(13) cm(-3) on a picosecond timescale using ultrashort electron pulses. Electric fields generated by the separation of charges are imprinted on a 20 keV probe electron pulse and reveal a cloud of electrons expanding away from a positively charged plasma core. Our method allows for a direct measurement of the electron energy required to escape the plasma and the total charge. Simulations reproduce the main features of the experiment and allow determination of the energy of the electrons.

  12. Electrons In The Low Density Solar Wind

    NASA Technical Reports Server (NTRS)

    Ogilvie, Keith W.; Desch, Michael; Fitzenreiter, Richard; Vondrak, Richard R. (Technical Monitor)

    2000-01-01

    The recent occurrence of an interval (May 9th to May 12th, 1999) of abnormally low density solar wind has drawn attention to such events. The SWE instrument on the Wind spacecraft observed nine similar events between launch (November 1994) and August 1999: one in 1997, three in 1998, and five in January-August 1999. No such events were observed in 1996, the year of solar minimum. This already suggests a strong dependence upon solar activity. In this paper we discuss observations of the electron strahl, a strong anisotropy in the solar wind electrons above 60 eV directed along the magnetic field and observed continuously during the periods of low density in 1998 and 1999. When the solar wind density was less than 2/cc, the angular width of the strahl was below 3.5 degrees and the temperature deduced from the slope of the electron strahl phase density (as a function of energy in the energy range 200 to 800 eV) was 100 to 150 eV, equivalent to a typical coronal electron temperature. Three examples of this phenomenon, observed on Feb. 20- 22, April 26-27 and May 9-12, 1999, are discussed to show their similarity to one another. These electron observations are interpreted to show that the strahl occurs as a result of the conservation of the first adiabatic invariant, combined with the lack of coulomb collisions as suggested by Fairfield and Scudder, 1985.

  13. Time-resolved ion flux, electron temperature and plasma density measurements in a pulsed Ar plasma using a capacitively coupled planar probe

    NASA Astrophysics Data System (ADS)

    Darnon, Maxime; Cunge, Gilles; Braithwaite, Nicholas St. J.

    2014-04-01

    The resurgence of industrial interest in pulsed radiofrequency plasmas for etching applications highlights the fact that these plasmas are much less well characterized than their continuous wave counterparts. A capacitively coupled planar probe is used to determine the time variations of the ion flux, electron temperature (of the high-energy tail of the electron energy distribution function) and plasma density. For a pulsing frequency of 1 kHz or higher, the plasma never reaches a steady state during the on-time and is not fully extinguished during the off-time. The drop of plasma density during the off-time leads to an overshoot in the electron temperature at the beginning of each pulse, particularly at low frequencies, in good agreement with modeling results from the literature.

  14. Stabilization of electron-scale turbulence by electron density gradient in national spherical torus experiment

    SciTech Connect

    Ruiz Ruiz, J.; White, A. E.; Ren, Y.; Guttenfelder, W.; Kaye, S. M.; Leblanc, B. P.; Mazzucato, E.; Lee, K. C.; Domier, C. W.; Smith, D. R.; Yuh, H.

    2015-12-15

    Theory and experiments have shown that electron temperature gradient (ETG) turbulence on the electron gyro-scale, k{sub ⊥}ρ{sub e} ≲ 1, can be responsible for anomalous electron thermal transport in NSTX. Electron scale (high-k) turbulence is diagnosed in NSTX with a high-k microwave scattering system [D. R. Smith et al., Rev. Sci. Instrum. 79, 123501 (2008)]. Here we report on stabilization effects of the electron density gradient on electron-scale density fluctuations in a set of neutral beam injection heated H-mode plasmas. We found that the absence of high-k density fluctuations from measurements is correlated with large equilibrium density gradient, which is shown to be consistent with linear stabilization of ETG modes due to the density gradient using the analytical ETG linear threshold in F. Jenko et al. [Phys. Plasmas 8, 4096 (2001)] and linear gyrokinetic simulations with GS2 [M. Kotschenreuther et al., Comput. Phys. Commun. 88, 128 (1995)]. We also found that the observed power of electron-scale turbulence (when it exists) is anti-correlated with the equilibrium density gradient, suggesting density gradient as a nonlinear stabilizing mechanism. Higher density gradients give rise to lower values of the plasma frame frequency, calculated based on the Doppler shift of the measured density fluctuations. Linear gyrokinetic simulations show that higher values of the electron density gradient reduce the value of the real frequency, in agreement with experimental observation. Nonlinear electron-scale gyrokinetic simulations show that high electron density gradient reduces electron heat flux and stiffness, and increases the ETG nonlinear threshold, consistent with experimental observations.

  15. Teaching Chemistry with Electron Density Models

    NASA Astrophysics Data System (ADS)

    Shusterman, Gwendolyn P.; Shusterman, Alan J.

    1997-07-01

    Linus Pauling once said that a topic must satisfy two criteria before it can be taught to students. First, students must be able to assimilate the topic within a reasonable amount of time. Second, the topic must be relevant to the educational needs and interests of the students. Unfortunately, the standard general chemistry textbook presentation of "electronic structure theory", set as it is in the language of molecular orbitals, has a difficult time satisfying either criterion. Many of the quantum mechanical aspects of molecular orbitals are too difficult for most beginning students to appreciate, much less master, and the few applications that are presented in the typical textbook are too limited in scope to excite much student interest. This article describes a powerful new method for teaching students about electronic structure and its relevance to chemical phenomena. This method, which we have developed and used for several years in general chemistry (G.P.S.) and organic chemistry (A.J.S.) courses, relies on computer-generated three-dimensional models of electron density distributions, and largely satisfies Pauling's two criteria. Students find electron density models easy to understand and use, and because these models are easily applied to a broad range of topics, they successfully convey to students the importance of electronic structure. In addition, when students finally learn about orbital concepts they are better prepared because they already have a well-developed three-dimensional picture of electronic structure to fall back on. We note in this regard that the types of models we use have found widespread, rigorous application in chemical research (1, 2), so students who understand and use electron density models do not need to "unlearn" anything before progressing to more advanced theories.

  16. Electron correlation by polarization of interacting densities

    NASA Astrophysics Data System (ADS)

    Whitten, Jerry L.

    2017-02-01

    Coulomb interactions that occur in electronic structure calculations are correlated by allowing basis function components of the interacting densities to polarize dynamically, thereby reducing the magnitude of the interaction. Exchange integrals of molecular orbitals are not correlated. The modified Coulomb interactions are used in single-determinant or configuration interaction calculations. The objective is to account for dynamical correlation effects without explicitly introducing higher spherical harmonic functions into the molecular orbital basis. Molecular orbital densities are decomposed into a distribution of spherical components that conserve the charge and each of the interacting components is considered as a two-electron wavefunction embedded in the system acted on by an average field Hamiltonian plus r12-1. A method of avoiding redundancy is described. Applications to atoms, negative ions, and molecules representing different types of bonding and spin states are discussed.

  17. Electron Density Profiles of the Topside Ionosphere

    NASA Technical Reports Server (NTRS)

    Huang, Xue-Qin; Reinsch, Bodo W.; Bilitza, Dieter; Benson, Robert F.

    2002-01-01

    The existing uncertainties about the electron density profiles in the topside ionosphere, i.e., in the height region from h,F2 to - 2000 km, require the search for new data sources. The ISIS and Alouette topside sounder satellites from the sixties to the eighties recorded millions of ionograms but most were not analyzed in terms of electron density profiles. In recent years an effort started to digitize the analog recordings to prepare the ionograms for computerized analysis. As of November 2001 about 350000 ionograms have been digitized from the original 7-track analog tapes. These data are available in binary and CDF format from the anonymous ftp site of the National Space Science Data Center. A search site and browse capabilities on CDAWeb assist the scientific usage of these data. All information and access links can be found at http://nssdc.gsfc.nasa.gov/space/isis/isis- status.htm1. This paper describes the ISIS data restoration effort and shows how the digital ionograms are automatically processed into electron density profiles from satellite orbit altitude (1400 km for ISIS-2) down to the F peak. Because of the large volume of data an automated processing algorithm is imperative. The TOPside Ionogram Scaler with True height algorithm TOPIST software developed for this task is successfully scaling - 70% of the ionograms. An <> is available to manually scale the more difficult ionograms. The automated processing of the digitized ISIS ionograms is now underway, producing a much-needed database of topside electron density profiles for ionospheric modeling covering more than one solar cycle.

  18. Electroweak charge density distributions with parity-violating electron scattering

    NASA Astrophysics Data System (ADS)

    Liu, Jian; Ren, Zhongzhou; Xu, Chang; Xu, Renli

    2013-11-01

    Parity-violating electron scattering (PVS) is an accurate and model-independent way to investigate the weak-charge density distributions of nuclei. In this paper, we study parity-violating electron scattering with the Helm model where the effects of spin-orbit currents on nuclear weak skins are taken into account. The conditions of two PVS measurements to constrain the surface thickness σW of Helm weak-charge densities are investigated. According to the plane wave Born approximation, Apv is expressed in terms of parameters of the corresponding Helm charge and weak-charge densities. After fitting the results of Apv calculated from the phase-shift analysis method where the Coulomb distortion effects are incorporated, an empirical formula in terms of Helm model parameters for calculating Apv is obtained. If two PVS measurements with different scattering angles are carried out, the modeled weak-charge density distributions with two parameters could be extracted from this empirical formula.

  19. Electron densities and the excitation of CN in molecular clouds

    NASA Technical Reports Server (NTRS)

    Black, John H.; Van Dishoeck, Ewine F.

    1991-01-01

    In molecular clouds of modest density and relatively high fractional ionization, the rotational excitation of CN is controlled by a competition among electron impact, neutral impact and the interaction with the cosmic background radiation. The degree of excitation can be measured through optical absorption lines and millimeter-wave emission lines. The available, accurate data on CN in diffuse and translucent molecular clouds are assembled and used to determine electron densities. The derived values, n(e) = roughly 0.02 - 0.5/cu cm, imply modest neutral densities, which generally agree well with determinations by other techniques. The absorption- and emission-line measurements of CN both exclude densities higher than n(H2) = roughly 10 exp 3.5/cu cm on scales varying from 0.001 to 60 arcsec in these clouds.

  20. Analysis of the IMAGE RPI electron density data and CHAMP plasmasphere electron density reconstructions with focus on plasmasphere modelling

    NASA Astrophysics Data System (ADS)

    Gerzen, T.; Feltens, J.; Jakowski, N.; Galkin, I.; Reinisch, B.; Zandbergen, R.

    2016-09-01

    The electron density of the topside ionosphere and the plasmasphere contributes essentially to the overall Total Electron Content (TEC) budget affecting Global Navigation Satellite Systems (GNSS) signals. The plasmasphere can cause half or even more of the GNSS range error budget due to ionospheric propagation errors. This paper presents a comparative study of different plasmasphere and topside ionosphere data aiming at establishing an appropriate database for plasmasphere modelling. We analyze electron density profiles along the geomagnetic field lines derived from the Imager for Magnetopause-to-Aurora Global Exploration (IMAGE) satellite/Radio Plasma Imager (RPI) records of remote plasma sounding with radio waves. We compare these RPI profiles with 2D reconstructions of the topside ionosphere and plasmasphere electron density derived from GNSS based TEC measurements onboard the Challenging Minisatellite Payload (CHAMP) satellite. Most of the coincidences between IMAGE profiles and CHAMP reconstructions are detected in the region with L-shell between 2 and 5. In general the CHAMP reconstructed electron densities are below the IMAGE profile densities, with median of the CHAMP minus IMAGE residuals around -588 cm-3. Additionally, a comparison is made with electron densities derived from passive radio wave RPI measurements onboard the IMAGE satellite. Over the available 2001-2005 period of IMAGE measurements, the considered combined data from the active and passive RPI operations cover the region within a latitude range of ±60°N, all longitudes, and an L-shell ranging from 1.2 to 15. In the coincidence regions (mainly 2 ⩽ L ⩽ 4), we check the agreement between available active and passive RPI data. The comparison shows that the measurements are well correlated, with a median residual of ∼52 cm-3. The RMS and STD values of the relative residuals are around 22% and 21% respectively. In summary, the results encourage the application of IMAGE RPI data for

  1. Measurements of Laser Plasma Instability (LPI) and Electron Density/Temperature Profiles in Plasmas Produced by the Nike KrF Laser

    NASA Astrophysics Data System (ADS)

    Oh, Jaechul; Weaver, J. L.; Serlin, V.; Obenschain, S. P.

    2016-10-01

    We will present results of simultaneous measurements of LPI-driven light scattering and density/temperature profiles in CH plasmas produced by the Nike krypton fluoride laser (λ = 248 nm). The primary diagnostics for the LPI measurement are time-resolved spectrometers with absolute intensity calibration in spectral ranges relevant to the optical detection of stimulated Raman scattering or two plasmon decay. The spectrometers are capable of monitoring signal intensity relative to thermal background radiation from plasma providing a useful way to analyze LPI initiation. For further understanding of LPI processes, the recently implemented grid image refractometer (Nike-GIR)a is used to measure the coronal plasma profiles. In this experiment, Nike-GIR is equipped with a 5th harmonic probe laser (λ = 213 nm) in attempt to probe into a high density region over the previous peak density with λ = 263 nm probe light ( 4 ×1021 cm-3). The LPI behaviors will be discussed with the measured data sets. Work supported by DoE/NNSA.

  2. Electron Density Measurements in the National Spherical Torus Experiment Detached Divertor Region Using Stark Broadening of Deuterium Infrared Paschen Emission Lines

    SciTech Connect

    Soukhanovskii, V A; Johnson, D W; Kaita, R; Roquemore, A L

    2007-04-27

    Spatially resolved measurements of deuterium Balmer and Paschen line emission have been performed in the divertor region of the National Spherical Torus Experiment using a commercial 0.5 m Czerny-Turner spectrometer. While the Balmer emission lines, Balmer and Paschen continua in the ultraviolet and visible regions have been extensively used for tokamak divertor plasma temperature and density measurements, the diagnostic potential of infrared Paschen lines has been largely overlooked. We analyze Stark broadening of the lines corresponding to 2-n and 3-m transitions with principle quantum numbers n = 7-12 and m = 10-12 using recent Model Microfield Method calculations (C. Stehle and R. Hutcheon, Astron. Astrophys. Supl. Ser. 140, 93 (1999)). Densities in the range (5-50) x 10{sup 19} m{sup -3} are obtained in the recombining inner divertor plasma in 2-6 MW NBI H-mode discharges. The measured Paschen line profiles show good sensitivity to Stark effects, and low sensitivity to instrumental and Doppler broadening. The lines are situated in the near-infrared wavelength domain, where optical signal extraction schemes for harsh nuclear environments are practically realizable, and where a recombining divertor plasma is optically thin. These properties make them an attractive recombining divertor density diagnostic for a burning plasma experiment.

  3. High Density Mastering Using Electron Beam

    NASA Astrophysics Data System (ADS)

    Kojima, Yoshiaki; Kitahara, Hiroaki; Kasono, Osamu; Katsumura, Masahiro; Wada, Yasumitsu

    1998-04-01

    A mastering system for the next-generation digital versatile disk (DVD) is required to have a higher resolution compared with the conventional mastering systems. We have developed an electron beam mastering machine which features a thermal field emitter and a vacuum sealed air spindle motor. Beam displacement caused by magnetic fluctuation with spindle rotation was about 60 nm(p-p) in both the radial and tangential directions. Considering the servo gain of a read-out system, it has little influence on the read-out signal in terms of tracking errors and jitters. The disk performance was evaluated by recording either the 8/16 modulation signal or a groove on the disk. The electron beam recording showed better jitter values from the disk playback than those from a laser beam recorder. The deviation of track pitch was 44 nm(p-p). We also confirmed the high density recording with a capacity reaching 30 GB.

  4. Single electron densities: a new tool to analyze molecular wavefunctions.

    PubMed

    Lüchow, Arne; Petz, René

    2011-09-01

    A new partitioning scheme for the electron density of a many-electron wavefunction into single electron densities is proposed. These densities are based on the most probable arrangement of the electrons in an atom or molecule. Therefore, they contain information about the electron-electron interaction and, most notably, the Fermi hole due to the antisymmetry of the many-electron wavefunction. The single electron densities overlap and can be combined to electron pair distributions close to the qualitative electron pairs that represent, for instance, the basis of the valence shell electron pair repulsion model. Single electron analyses are presented for the water, ethane, and ethene molecules. The effect of electron correlation on the single electron and pair densities is investigated for the water molecule.

  5. Electron temperature and density relationships in coronal mass ejections

    NASA Technical Reports Server (NTRS)

    Hammond, C. M.; Phillips, J. L.; Balogh, A.

    1995-01-01

    We examine 10 coronal mass ejections from the in-ecliptic portion of the Ulysses mission. Five of these CMEs are magnetic clouds. In each case we observe an inverse relationship between electron temperature and density. For protons this relationship is less clear. Earlier work has shown a similar inverse relationship for electrons inside magnetic clouds and interpreted it to mean that the polytropic index governing the expansion of electrons is less than unity. This requires electrons to be heated as the CME expands. We offer an alternative view that the inverse relationship between electron temperature and density is caused by more rapid cooling of the denser plasma through collisions. More rapid cooling of denser plasma has been shown for 1 AU measurements in the solar wind. As evidence for this hypothesis we show that the denser plasma inside the CMEs tends to be more isotropic indicating a different history of collisions for the dense plasma. Thus, although the electron temperature inside CMEs consistently shows an inverse correlation with the density, this is not an indication of the polytropic index of the plasma but instead supports the idea of collisional modification of the electrons during their transit from the sun.

  6. Electron momentum spectroscopy study of amantadine: binding energy spectra and valence orbital electron density distributions

    NASA Astrophysics Data System (ADS)

    Litvinyuk, I. V.; Zheng, Y.; Brion, C. E.

    2000-11-01

    The electron binding energy spectrum and valence orbital electron momentum density distributions of amantadine (1-aminoadamantane), an important anti-viral and anti-Parkinsonian drug, have been measured by electron momentum spectroscopy. Theoretical momentum distributions, calculated at the 6-311++G** and AUG-CC-PVTZ levels within the target Hartree-Fock and also the target Kohn-Sham density functional theory approximations, show good agreement with the experimental results. The results for amantadine are also compared with those for the parent molecule, adamantane, reported earlier (Chem. Phys. 253 (2000) 41). Based on the comparison tentative assignments of the valence region ionization bands of amantadine have been made.

  7. Density-dependent electron transport and precise modeling of GaN high electron mobility transistors

    SciTech Connect

    Bajaj, Sanyam Shoron, Omor F.; Park, Pil Sung; Krishnamoorthy, Sriram; Akyol, Fatih; Hung, Ting-Hsiang; Reza, Shahed; Chumbes, Eduardo M.; Khurgin, Jacob; Rajan, Siddharth

    2015-10-12

    We report on the direct measurement of two-dimensional sheet charge density dependence of electron transport in AlGaN/GaN high electron mobility transistors (HEMTs). Pulsed IV measurements established increasing electron velocities with decreasing sheet charge densities, resulting in saturation velocity of 1.9 × 10{sup 7 }cm/s at a low sheet charge density of 7.8 × 10{sup 11 }cm{sup −2}. An optical phonon emission-based electron velocity model for GaN is also presented. It accommodates stimulated longitudinal optical (LO) phonon emission which clamps the electron velocity with strong electron-phonon interaction and long LO phonon lifetime in GaN. A comparison with the measured density-dependent saturation velocity shows that it captures the dependence rather well. Finally, the experimental result is applied in TCAD-based device simulator to predict DC and small signal characteristics of a reported GaN HEMT. Good agreement between the simulated and reported experimental results validated the measurement presented in this report and established accurate modeling of GaN HEMTs.

  8. Implementation of a multichannel soft x-ray diagnostic for electron temperature measurements in TJ-II high-density plasmas

    SciTech Connect

    Baiao, D.; Varandas, C.; Molinero, A.; Chercoles, J.

    2012-10-15

    Based on the multi-foil technique, a multichannel soft x-ray diagnostic for electron temperature measurements has been recently implemented in the TJ-II stellarator. The diagnostic system is composed by four photodiodes arrays with beryllium filters of different thickness. An in-vacuum amplifier board is coupled to each array, aiming at preventing induced noise currents. The Thomson scattering and the vacuum ultraviolet survey diagnostics are used for assessing plasma profiles and composition, being the analysis carried out with the radiation code IONEQ. The electron temperature is determined through the different signal-pair ratios with temporal and spatial resolution. The design and preliminary results from the diagnostic are presented.

  9. Superthermal electron distribution measurements from polarized electron cyclotron emission

    SciTech Connect

    Luce, T.C.; Efthimion, P.C.; Fisch, N.J.

    1988-06-01

    Measurements of the superthermal electron distribution can be made by observing the polarized electron cyclotron emission. The emission is viewed along a constant magnetic field surface. This simplifies the resonance condition and gives a direct correlation between emission frequency and kinetic energy of the emitting electron. A transformation technique is formulated which determines the anisotropy of the distribution and number density of superthermals at each energy measured. The steady-state distribution during lower hybrid current drive and examples of the superthermal dynamics as the runaway conditions is varied are presented for discharges in the PLT tokamak. 15 refs., 8 figs.

  10. Total electron content and F-region electron density distribution near the magnetic equator in India

    NASA Technical Reports Server (NTRS)

    Rastogi, R. G.; Sethia, G.; Chandra, H.; Deshpande, M. R.; Davies, K.; Murthy, B. S.

    1979-01-01

    Total electron content derived from the group delay measurements of ATS-6 radio beacons received at Ootacamund (India) are compared with the electron-density vs height distributions derived from the ionosonde data of the nearby station Kodaikanal. The daily variation of equivalent vertical total electron content does not show the midday bite out which is so prominently present in the corresponding daily variation of the maximum F-region electron density. The topside electron content continues to increase from sunrise to a maximum value around 1500 LT, while the bottomside electron content reaches a maximum value around 0500 LT. Daily variations of these as well as other parameters, e.g. the vertical slab thickness, the bottomside semi-thickness, the height of the F2 peak have been also studied for a geomagnetically quiet and a disturbed day.

  11. Exploring the temporally resolved electron density evolution in extreme ultra-violet induced plasmas

    NASA Astrophysics Data System (ADS)

    van der Horst, R. M.; Beckers, J.; Nijdam, S.; Kroesen, G. M. W.

    2014-07-01

    We measured the electron density in an extreme ultra-violet (EUV) induced plasma. This is achieved in a low-pressure argon plasma by using a method called microwave cavity resonance spectroscopy. The measured electron density just after the EUV pulse is 2.6 × 1016 m-3. This is in good agreement with a theoretical prediction from photo-ionization, which yields a density of 4.5 × 1016 m-3. After the EUV pulse the density slightly increases due to electron impact ionization. The plasma (i.e. electron density) decays in tens of microseconds.

  12. Modeling Ionosphere Environments: Creating an ISS Electron Density Tool

    NASA Technical Reports Server (NTRS)

    Gurgew, Danielle N.; Minow, Joseph I.

    2011-01-01

    The International Space Station (ISS) maintains an altitude typically between 300 km and 400 km in low Earth orbit (LEO) which itself is situated in the Earth's ionosphere. The ionosphere is a region of partially ionized gas (plasma) formed by the photoionization of neutral atoms and molecules in the upper atmosphere of Earth. It is important to understand what electron density the spacecraft is/will be operating in because the ionized gas along the ISS orbit interacts with the electrical power system resulting in charging of the vehicle. One instrument that is already operational onboard the ISS with a goal of monitoring electron density, electron temperature, and ISS floating potential is the Floating Potential Measurement Unit (FPMU). Although this tool is a valuable addition to the ISS, there are limitations concerning the data collection periods. The FPMU uses the Ku band communication frequency to transmit data from orbit. Use of this band for FPMU data runs is often terminated due to necessary observation of higher priority Extravehicular Activities (EVAs) and other operations on ISS. Thus, large gaps are present in FPMU data. The purpose of this study is to solve the issue of missing environmental data by implementing a secondary electron density data source, derived from the COSMIC satellite constellation, to create a model of ISS orbital environments. Extrapolating data specific to ISS orbital altitudes, we model the ionospheric electron density along the ISS orbit track to supply a set of data when the FPMU is unavailable. This computer model also provides an additional new source of electron density data that is used to confirm FPMU is operating correctly and supplements the original environmental data taken by FPMU.

  13. Wireless sensor node for surface seawater density measurements.

    PubMed

    Baronti, Federico; Fantechi, Gabriele; Roncella, Roberto; Saletti, Roberto

    2012-01-01

    An electronic meter to measure surface seawater density is presented. It is based on the measurement of the difference in displacements of a surface level probe and a weighted float, which according to Archimedes' law depends on the density of the water. The displacements are simultaneously measured using a high-accuracy magnetostrictive sensor, to which a custom electronic board provides a wireless connection and power supply so that it can become part of a wireless sensor network. The electronics are designed so that different kinds of wireless networks can be used, by simply changing the wireless module and the relevant firmware of the microcontroller. Lastly, laboratory and at-sea tests are presented and discussed in order to highlight the functionality and the performance of a prototype of the wireless density meter node in a Bluetooth radio network. The experimental results show a good agreement of the values of the calculated density compared to reference hydrometer readings.

  14. Electron Density Determination, Bonding and Properties of Tetragonal Ferromagnetic Intermetallics

    SciTech Connect

    Wiezorek, Jorg

    2016-09-01

    The project developed quantitative convergent-beam electron diffraction (QCBED) methods by energy-filtered transmission electron microscopy (EFTEM) and used them in combination with density functional theory (DFT) calculations to study the electron density distribution in metallic and intermetallic phases with different cubic and non-cubic crystal structures that comprise elements with d-electron shells. The experimental methods developed here focus on the bonding charge distribution as one of the quantum mechanical characteristics central for understanding of intrinsic properties and validation of DFT calculations. Multiple structure and temperature factors have been measured simultaneously from nano-scale volumes of high-quality crystal with sufficient accuracy and precision for comparison with electron density distribution calculations by DFT. The often anisotropic temperature factors for the different atoms and atom sites in chemically ordered phases can differ significantly from those known for relevant pure element crystals due to bonding effects. Thus they have been measured from the same crystal volumes from which the structure factors have been determined. The ferromagnetic ordered intermetallic phases FePd and FePt are selected as model systems for 3d-4d and 3d-5d electron interactions, while the intermetallic phases NiAl and TiAl are used to probe 3d-3p electron interactions. Additionally, pure transition metal elements with d-electrons have been studied. FCC metals exhibit well defined delocalized bonding charge in tetrahedral sites, while less directional, more distributed bonding charge attains in BCC metals. Agreement between DFT calculated and QCBED results degrades as d-electron levels fill in the elements, and for intermetallics as d-d interactions become prominent over p-d interactions. Utilizing the LDA+U approach enabled inclusion of onsite Coulomb-repulsion effects in DFT calculations, which can afford improved agreements with QCBED results

  15. Time and space resolved measurement of the electron temperature, mass density and ionization state in the ablation plasma between two exploding Al wiresa)

    NASA Astrophysics Data System (ADS)

    Knapp, P. F.; Pikuz, S. A.; Shelkovenko, T. A.; Hammer, D. A.; Hansen, S. B.

    2012-05-01

    We have determined the properties of plasma around and between two exploding wires using high-resolution x-ray absorption spectroscopy. Plasma densities and temperatures ranging from ≳0.1g/cm3 and a few eV to less than 0.01 g/cm3 and 30 eV have been measured in experiments at Cornell University with two 40 μm aluminum (Al) wires spaced 1 mm apart driven by ˜150 kA peak current pulses with 100 ns rise time. The wire plasma was backlit by the 1.4-1.6 keV continuum radiation produced by a Mo wire X-pinch. The spectrometer employed two spherically bent quartz crystals to record the absorption and backlighter spectra simultaneously. The transition between the dense Al wire core and the coronal plasma is seen as a transition from cold K-edge absorption to Mg-, Na-, and finally Ne-like absorption at the boundary. In the plasma that accumulates between the wires, ionization states up to C-Like Al are observed. The spectrometer geometry and ˜2μm X-pinch source size provide 0.3 eV spectral resolution and 20 μm spatial resolution enabling us to see 1s → 2p satellite transitions as separate lines as well as O-, F-, and Ne-like 1s → 3p transitions that have not been seen before. A step wedge was used to calibrate the transmission, enabling density to be measured within a factor of two and temperature to be measured within ±25%. A genetic algorithm was developed to fit synthetic spectra calculated using the collisional-radiative code SCRAM to the experimental spectra. In order to obtain agreement it was necessary to assume multiple plasma regions with variable thicknesses, thereby allowing the inferred plasma conditions to vary along the absorption path.

  16. A novel electron density reconstruction method for asymmetrical toroidal plasmas

    SciTech Connect

    Shi, N.; Ohshima, S.; Minami, T.; Nagasaki, K.; Yamamoto, S.; Mizuuchi, T.; Okada, H.; Kado, S.; Kobayashi, S.; Konoshima, S.; Sano, F.; Tanaka, K.; Ohtani, Y.; Zang, L.; Kenmochi, N.

    2014-05-15

    A novel reconstruction method is developed for acquiring the electron density profile from multi-channel interferometric measurements of strongly asymmetrical toroidal plasmas. It is based on a regularization technique, and a generalized cross-validation function is used to optimize the regularization parameter with the aid of singular value decomposition. The feasibility of method could be testified by simulated measurements based on a magnetic configuration of the flexible helical-axis heliotron device, Heliotron J, which has an asymmetrical poloidal cross section. And the successful reconstruction makes possible to construct a multi-channel Far-infrared laser interferometry on this device. The advantages of this method are demonstrated by comparison with a conventional method. The factors which may affect the accuracy of the results are investigated, and an error analysis is carried out. Based on the obtained results, the proposed method is highly promising for accurately reconstructing the electron density in the asymmetrical toroidal plasma.

  17. Imaginary time density-density correlations for two-dimensional electron gases at high density

    SciTech Connect

    Motta, M.; Galli, D. E.; Moroni, S.; Vitali, E.

    2015-10-28

    We evaluate imaginary time density-density correlation functions for two-dimensional homogeneous electron gases of up to 42 particles in the continuum using the phaseless auxiliary field quantum Monte Carlo method. We use periodic boundary conditions and up to 300 plane waves as basis set elements. We show that such methodology, once equipped with suitable numerical stabilization techniques necessary to deal with exponentials, products, and inversions of large matrices, gives access to the calculation of imaginary time correlation functions for medium-sized systems. We discuss the numerical stabilization techniques and the computational complexity of the methodology and we present the limitations related to the size of the systems on a quantitative basis. We perform the inverse Laplace transform of the obtained density-density correlation functions, assessing the ability of the phaseless auxiliary field quantum Monte Carlo method to evaluate dynamical properties of medium-sized homogeneous fermion systems.

  18. Communication: Investigation of the electron momentum density distribution of nanodiamonds by electron energy-loss spectroscopy

    SciTech Connect

    Feng, Zhenbao; Yang, Bing; Lin, Yangming; Su, Dangsheng

    2015-12-07

    The electron momentum distribution of detonation nanodiamonds (DND) was investigated by recording electron energy-loss spectra at large momentum transfer in the transmission electron microscope (TEM), which is known as electron Compton scattering from solid (ECOSS). Compton profile of diamond film obtained by ECOSS was found in good agreement with prior photon experimental measurement and theoretical calculation that for bulk diamond. Compared to the diamond film, the valence Compton profile of DND was found to be narrower, which indicates a more delocalization of the ground-state charge density for the latter. Combining with other TEM characterizations such as high-resolution transmission electron spectroscopy, diffraction, and energy dispersive X-ray spectroscopy measurements, ECOSS was shown to be a great potential technique to study ground-state electronic properties of nanomaterials.

  19. Time and space resolved measurement of the electron temperature, mass density and ionization state in the ablation plasma between two exploding Al wires

    SciTech Connect

    Knapp, P. F.; Pikuz, S. A.; Shelkovenko, T. A.; Hammer, D. A.; Hansen, S. B.

    2012-05-15

    We have determined the properties of plasma around and between two exploding wires using high-resolution x-ray absorption spectroscopy. Plasma densities and temperatures ranging from Greater-Than-Or-Equivalent-To 0.1g/cm{sup 3} and a few eV to less than 0.01 g/cm{sup 3} and 30 eV have been measured in experiments at Cornell University with two 40 {mu}m aluminum (Al) wires spaced 1 mm apart driven by {approx}150 kA peak current pulses with 100 ns rise time. The wire plasma was backlit by the 1.4-1.6 keV continuum radiation produced by a Mo wire X-pinch. The spectrometer employed two spherically bent quartz crystals to record the absorption and backlighter spectra simultaneously. The transition between the dense Al wire core and the coronal plasma is seen as a transition from cold K-edge absorption to Mg-, Na-, and finally Ne-like absorption at the boundary. In the plasma that accumulates between the wires, ionization states up to C-Like Al are observed. The spectrometer geometry and {approx}2{mu}m X-pinch source size provide 0.3 eV spectral resolution and 20 {mu}m spatial resolution enabling us to see 1s{yields} 2p satellite transitions as separate lines as well as O-, F-, and Ne-like 1s{yields} 3p transitions that have not been seen before. A step wedge was used to calibrate the transmission, enabling density to be measured within a factor of two and temperature to be measured within {+-}25%. A genetic algorithm was developed to fit synthetic spectra calculated using the collisional-radiative code SCRAM to the experimental spectra. In order to obtain agreement it was necessary to assume multiple plasma regions with variable thicknesses, thereby allowing the inferred plasma conditions to vary along the absorption path.

  20. Measuring electron beam polarization

    NASA Astrophysics Data System (ADS)

    Napolitano, J.

    1992-12-01

    A two-hour discussion session was held on electron beam polarimetry including representatives from Halls A, B, and C. Presentations included a description of an existing Mo/ller polarimeter at the MIT-Bates laboratory, plans for Mo/ller polarimeters in Halls A and B, and a Compton (i.e., ``laser backscatter'') polarimeter planned for Hall A. This paper is a summary of those discussions.

  1. Electron density power spectrum in the local interstellar medium

    NASA Technical Reports Server (NTRS)

    Armstrong, J. W.; Rickett, B. J.; Spangler, S. R.

    1995-01-01

    Interstellar scintillation (ISS), fluctuations in the amplitude and phase of radio waves caused by scattering in the interstellar medium, is important as a diagnostic of interstellar plasma turbulence. ISS is also of interest because it is noise for other radio astronomical observations. The unifying concern is the power spectrum of the interstellar electron density. Here we use ISS observations through the nearby (less than or approximately =1 kpc) (ISM) to estimate the spectrum. From measurements of angular broadening of pulsars and extragalactic sources, decorrelation bandwidth of pulsars, refractive steering of features in pulsar dynamic spectra, dispersion measured fluctuations of pulsars, and refractive scintillation index measurements, we construct a composite structure function that is approximately power law over 2 x 10(exp 6) m less than scale less than 10(exp 13) m. The data are consistent with the structure function having a logarithmic slope versus baseline less than 2; thus there is a meaningful connection between scales in the radiowave fluctuation field and the scales in the electron density field causing the scattering. The data give an upper limit to the inner scale, l(sub o) less than or approximately 10(exp 8) m and are consistent with much smaller values. We construct a composite electron density spectrum that is approximately power law over at least the approximately = 5 decade wavenumber range 10(exp -13)/m less than wavenumber less than 10(exp -8)/m and that may extend to higher wavenumbers. The average spectral index of electron density over this wavenumber range is approximately = 3.7, very close to the value expected for a Kolmogorov process. The outer scale size, L(sub o), must be greater than or approximately = 10(exp 13) m (determined from dispersion measure fluctuations). When the ISS data are combined with measurements of differential Faraday rotation angle, and gradients in the average electron density, constraints can be put on the

  2. An Overview of Ionospheric Electron Density Variations over Istanbul

    NASA Astrophysics Data System (ADS)

    Kaymaz, Zerefsan; Türk Katircioglu, Filiz; Ceren Moral, Aysegul; Emine Ceren Kalafatoglu Eyiguler, R. A..; Zabotin, Nikolai

    2016-07-01

    This study will present the temporal variations in electron density measured in Istanbul (42, 29) using Dynasonde observations. Dynasonde is a type of ionosonde that can measure the dynamics of the ionosphere. Istanbul Dynasonde was established in October 2012 and collecting data since then. The NeXtYZ software have been used to convert ionospheric signals into ionospheric data. In this study, among 72 outputs of ionospheric parameters, electron density, and critical frequency for F2 layer, and TEC have been studied to reveal the ionospheric variations over Istanbul. Statistics for seasonal, monthly and daily variations were obtained by scanning thorough about two years of ionograms. Four types of temporal variability were determined depending on the season and the time of the day. Gravity waves were detected very clearly in the ionograms at this mid-latitude station. In addition, magnetic substorm signatures on the electron density are clearly noticeable and are seen both positive and negative phases. In this talk we will give an overview of the results based on the first two years of the Dynasonde operation in Istanbul.

  3. Deriving large electron temperatures and small electron densities with the Cassini Langmuir probe at Saturn

    NASA Astrophysics Data System (ADS)

    Garnier, Philippe; Wahlund, Jan-Erik; Holmberg, Mika; Lewis, Geraint; Schippers, Patricia; Rochel Grimald, Sandrine; Gurnett, Donald; Coates, Andrew; Dandouras, Iannis; Waite, Hunter

    2014-05-01

    The Langmuir Probes (LPs) are commonly used to investigate the cold plasma characteristics in planetary ionospheres/magnetospheres. The LPs performances are limited to low temperatures (i.e. below 5-10 eV at Saturn) and large densities (above several particles/cm3). A strong sensitivity of the Cassini LP measurements to energetic electrons (hundreds eV) may however be observed at Saturn in the L Shell range L=6-10 RS. These electrons impact the surface of the probe and generate a detectable current of secondary electrons. We investigate the influence of such electrons on the current-voltage (I-V) characteristics (for negative potentials), and manage to reproduce the observations with a reasonable precision through empirical and theoretical methods. Conversely, the modelling allows us to derive useful information about the energetic electrons from the LP observations : some information about their pitch angle anisotropy (if combined with the data from a single CAPS ELS anode), as well as an estimate of the electron temperature (in the range 100-300 eV) and of the electron density (above 0.1 particles/cm3). This enlarges the LP measurements capabilities when the influence of the energetic electrons is large (essentially near L=6-10 RS at Saturn). We finally show that a significant influence of the energetic electrons (larger than the contribution of thermal ions) is also expected in various plasma environments of the Solar System, such as at Jupiter (i.e near Ganymede, Europa, Callisto and Io), or even at Earth (in the plasmasheet, the magnetosheath or in plasma cavities). Large electron temperatures and small electron densities could potentially be derived in these environments, which may be of interest for Langmuir Probes in the Earth magnetosphere or onboard the future JUICE mission at Jupiter.

  4. Electron temperature and density probe for small aeronomy satellites.

    PubMed

    Oyama, K-I; Hsu, Y W; Jiang, G S; Chen, W H; Cheng, C Z; Fang, H K; Liu, W T

    2015-08-01

    A compact and low power consumption instrument for measuring the electron density and temperature in the ionosphere has been developed by modifying the previously developed Electron Temperature Probe (ETP). A circuit block which controls frequency of the sinusoidal signal is added to the ETP so that the instrument can measure both T(e) in low frequency mode and N(e) in high frequency mode from the floating potential shift of the electrode. The floating potential shift shows a minimum at the upper hybrid resonance frequency (f(UHR)). The instrument which is named "TeNeP" can be used for tiny satellites which do not have enough conductive surface area for conventional DC Langmuir probe measurements. The instrument also eliminates the serious problems associated with the contamination of satellite surface as well as the sensor electrode.

  5. Electron temperature and density probe for small aeronomy satellites

    SciTech Connect

    Oyama, K.-I.; Hsu, Y. W.; Jiang, G. S.; Chen, W. H.; Liu, W. T.; Cheng, C. Z.; Fang, H. K.

    2015-08-15

    A compact and low power consumption instrument for measuring the electron density and temperature in the ionosphere has been developed by modifying the previously developed Electron Temperature Probe (ETP). A circuit block which controls frequency of the sinusoidal signal is added to the ETP so that the instrument can measure both T{sub e} in low frequency mode and N{sub e} in high frequency mode from the floating potential shift of the electrode. The floating potential shift shows a minimum at the upper hybrid resonance frequency (f{sub UHR}). The instrument which is named “TeNeP” can be used for tiny satellites which do not have enough conductive surface area for conventional DC Langmuir probe measurements. The instrument also eliminates the serious problems associated with the contamination of satellite surface as well as the sensor electrode.

  6. Electron temperature and density probe for small aeronomy satellites

    NASA Astrophysics Data System (ADS)

    Oyama, K.-I.; Hsu, Y. W.; Jiang, G. S.; Chen, W. H.; Cheng, C. Z.; Fang, H. K.; Liu, W. T.

    2015-08-01

    A compact and low power consumption instrument for measuring the electron density and temperature in the ionosphere has been developed by modifying the previously developed Electron Temperature Probe (ETP). A circuit block which controls frequency of the sinusoidal signal is added to the ETP so that the instrument can measure both Te in low frequency mode and Ne in high frequency mode from the floating potential shift of the electrode. The floating potential shift shows a minimum at the upper hybrid resonance frequency (fUHR). The instrument which is named "TeNeP" can be used for tiny satellites which do not have enough conductive surface area for conventional DC Langmuir probe measurements. The instrument also eliminates the serious problems associated with the contamination of satellite surface as well as the sensor electrode.

  7. Driving Plasmaspheric Electron Density Simulations During Geomagnetic Storms

    NASA Astrophysics Data System (ADS)

    De Pascuale, S.; Kletzing, C.; Jordanova, V.; Goldstein, J.; Wygant, J. R.; Thaller, S. A.

    2015-12-01

    We test global convection electric field models driving plasmaspheric electron density simulations (RAM-CPL) during geomagnetic storms with in situ measurements provided by the Van Allen Probes (RBSP). RAM-CPL is the cold plasma component of the ring-current atmosphere interactions suite (RAM-SCB) and describes the evolution of plasma density in the magnetic equatorial plane near Earth. Geomagnetic events observed by the RBSP satellites in different magnetic local time (MLT) sectors enable a comparison of local asymmetries in the input electric field and output densities of these simulations. Using a fluid MHD approach, RAM-CPL reproduces core plasmaspheric densities (L<4) to less than 1 order of magnitude difference. Approximately 80% of plasmapause crossings, defined by a low-density threshold, are reproduced to within a mean radial difference of 0.6 L. RAM-CPL, in conjunction with a best-fit driver, can be used in other studies as an asset to predict density conditions in locations distant from RBSP orbits of interest.

  8. Interferometer for the measurement of plasma density

    DOEpatents

    Jacobson, Abram R.

    1980-01-01

    An interferometer which combines the advantages of a coupled cavity interferometer requiring alignment of only one light beam, and a quadrature interferometer which has the ability to track multi-fringe phase excursions unambiguously. The device utilizes a Bragg cell for generating a signal which is electronically analyzed to unambiguously determine phase modulation which is proportional to the path integral of the plasma density.

  9. Measuring track densities in lunar grains using image analysis

    NASA Technical Reports Server (NTRS)

    Blanford, G. E.; Mckay, D. S.; Bernhard, R. P.; Schulz, C. K.

    1994-01-01

    We have used digitized scanning electron micrographs and computer image analysis programs to measure track densities in lunar soil grains. Tracks were formed by highly ionizing solar energetic particles and cosmic rays. Back-scattered electron images produced suitable high contrast images for analysis. We used computer counting and measurement of area to obtain track densities. We found an excellent correlation with manual measurements for track densities below 1x10(exp 8) cm(exp -2). For track densities between 1x10(exp 8) to 1x10(exp 9) cm(exp -2) we found that a regression formula using the percentage area covered by tracks gave good agreement with manual measurements. Measurement of tract densities in lunar samples has been a very rewarding technique for measuring exposure ages and soil maturation processes. We have shown that we can reliably measure track densities in lunar grains using image analysis techniques. Automating track counting may allow application of this technique to important problems in regolith dynamics including the ratio of radiation exposure to reworking in various surface and core samples and in regolith breccias.

  10. Absolute density measurements in the middle atmosphere

    NASA Astrophysics Data System (ADS)

    Rapp, M.; Gumbel, J.; Lübken, F.-J.

    2001-05-01

    In the last ten years a total of 25 sounding rockets employing ionization gauges have been launched at high latitudes ( ~ 70° N) to measure total atmospheric density and its small scale fluctuations in an altitude range between 70 and 110 km. While the determination of small scale fluctuations is unambiguous, the total density analysis has been complicated in the past by aerodynamical disturbances leading to densities inside the sensor which are enhanced compared to atmospheric values. Here, we present the results of both Monte Carlo simulations and wind tunnel measurements to quantify this aerodynamical effect. The comparison of the resulting ‘ram-factor’ profiles with empirically determined density ratios of ionization gauge measurements and falling sphere measurements provides excellent agreement. This demonstrates both the need, but also the possibility, to correct aerodynamical influences on measurements from sounding rockets. We have determined a total of 20 density profiles of the mesosphere-lower-thermosphere (MLT) region. Grouping these profiles according to season, a listing of mean density profiles is included in the paper. A comparison with density profiles taken from the reference atmospheres CIRA86 and MSIS90 results in differences of up to 40%. This reflects that current reference atmospheres are a significant potential error source for the determination of mixing ratios of, for example, trace gas constituents in the MLT region.

  11. Spacetime Average Density (SAD) cosmological measures

    SciTech Connect

    Page, Don N.

    2014-11-01

    The measure problem of cosmology is how to obtain normalized probabilities of observations from the quantum state of the universe. This is particularly a problem when eternal inflation leads to a universe of unbounded size so that there are apparently infinitely many realizations or occurrences of observations of each of many different kinds or types, making the ratios ambiguous. There is also the danger of domination by Boltzmann Brains. Here two new Spacetime Average Density (SAD) measures are proposed, Maximal Average Density (MAD) and Biased Average Density (BAD), for getting a finite number of observation occurrences by using properties of the Spacetime Average Density (SAD) of observation occurrences to restrict to finite regions of spacetimes that have a preferred beginning or bounce hypersurface. These measures avoid Boltzmann brain domination and appear to give results consistent with other observations that are problematic for other widely used measures, such as the observation of a positive cosmological constant.

  12. Probing Electron Dynamics with the Laplacian of the Momentum Density

    SciTech Connect

    Sukumar, N.; MacDougall, Preston J.; Levit, M. Creon

    2012-09-24

    This chapter in the above-titled monograph presents topological analysis of the Laplacian of the electron momentum density in organic molecules. It relates topological features in this distribution to chemical and physical properties, particularly aromaticity and electron transport.

  13. BOOK REVIEW: Practical Density Measurement and Hydrometry

    NASA Astrophysics Data System (ADS)

    Gupta, S. V.

    2003-01-01

    Density determinations are very important not only for science and production but also in everyday life, since very often a product is sold by mass but the content of the package is measured by volume (or vice versa) so that the density is needed to convert the values. In production processes the density serves as a measure of mixing ratios and other properties. In science, the determination of Avogadro's constant using silicon single crystals and the potential replacement of the kilogram prototype boost density determination to an extremely low relative uncertainty of 10-7 or less. The book by S V Gupta explains in detail the foundations of any density measurement, namely the volume determination of solid artefacts in terms of the SI base unit of length and the density of water and mercury. Both the history and the actual state of science are reported. For practical density measurements, these chapters contain very useful formulae and tables. Water is treated in detail since it is most widely used as a standard not only for density determination but also to gravimetrically calibrate the capacity of volumetric glassware. Two thirds of the book are devoted to the practical density measurement of solids and liquids, mainly using classical instruments like pycnometers and hydrometers. Methods using free flotation of samples in a liquid without suspension are especially useful for small samples. Also, density determinations of powders and granular or porous samples are explained. Unfortunately, modern density meters of the oscillation type are dealt with in only a few pages. The book is clearly written and easy to understand. It contains a lot of evaluations of formulae that for practical measurements are represented in detailed tables. Methods and measurement procedures are described in detail, including also the calculation of uncertainty. Listings of the advantages and disadvantages of the different methods are very helpful. S V Gupta has written a book that will be

  14. Momentum-space properties from coordinate-space electron density

    SciTech Connect

    Harbola, Manoj K.; Zope, Rajendra R.; Kshirsagar, Anjali; Pathak, Rajeev K.

    2005-05-22

    Electron density and electron momentum density, while independently tractable experimentally, bear no direct connection without going through the many-electron wave function. However, invoking a variant of the constrained-search formulation of density-functional theory, we develop a general scheme (valid for arbitrary external potentials) yielding decent momentum-space properties, starting exclusively from the coordinate-space electron density. A numerical illustration of the scheme is provided for the closed-shell atomic systems He, Be, and Ne in their ground state and for 1s{sup 1} 2s{sup 1} singlet electronic excited state for helium by calculating the Compton profiles and the expectation values derived from given coordinate-space electron densities.

  15. Electronic and nuclear flux densities in the H2 molecule

    NASA Astrophysics Data System (ADS)

    Hermann, G.; Paulus, B.; Pérez-Torres, J. F.; Pohl, V.

    2014-05-01

    We present a theoretical study of the electronic and nuclear flux densities of a vibrating H2 molecule after an electronic excitation by a short femtosecond laser pulse. The final state, a coherent superposition of the electronic ground state X1Σg+ and the electronic excited state B1Σu+, evolves freely and permits the partition of the electronic flux density into two competing fluxes: the adiabatic and the transition flux density. The nature of the two fluxes allows us to identify two alternating dynamics of the electronic motion, occurring on the attosecond and the femtosecond time scales. In contradistinction to the adiabatic electronic flux density, the transition electronic flux density shows a dependence on the carrier-envelope phase of the laser field, encoding information of the interaction of the electrons with the electric field. Furthermore, the nuclear flux density displays multiple reversals, a quantum effect recently discovered by Manz et al. [J. Manz, J. F. Pérez-Torres, and Y. Yang, Phys. Rev. Lett. 111, 153004 (2013), 10.1103/PhysRevLett.111.153004], calling for investigation of the electronic flux density.

  16. Validation of DSMC results for chemically nonequilibrium air flows against measurements of the electron number density in RAM-C II flight experiment

    SciTech Connect

    Shevyrin, Alexander A.; Vashchenkov, Pavel V.; Bondar, Yevgeniy A.; Ivanov, Mikhail S.

    2014-12-09

    An ionized flow around the RAM C-II vehicle in the range of altitudes from 73 to 81 km is studied by the Direct Simulation Monte Carlo (DSMC) method with three models of chemical reactions. It is demonstrated that vibration favoring in reactions of dissociation of neutral molecules affects significantly the predicted values of plasma density in the shock layer, and good agreement between the results of experiments and DSMC computations can be achieved in terms of the plasma density as a function of the flight altitude.

  17. MAVEN observations of dayside peak electron densities in the ionosphere of Mars

    NASA Astrophysics Data System (ADS)

    Vogt, Marissa F.; Withers, Paul; Fallows, Kathryn; Andersson, Laila; Girazian, Zachary; Mahaffy, Paul R.; Benna, Mehdi; Elrod, Meredith K.; Connerney, John E. P.; Espley, Jared R.; Eparvier, Frank G.; Jakosky, Bruce M.

    2017-01-01

    The peak electron density in the dayside Martian ionosphere is a valuable diagnostic of the state of the ionosphere. Its dependence on factors like the solar zenith angle, ionizing solar irradiance, neutral scale height, and electron temperature has been well studied. The Mars Atmosphere and Volatile EvolutioN spacecraft's September 2015 "deep dip" orbits, in which the orbital periapsis was lowered to 125 km, provided the first opportunity since Viking to sample in situ a complete dayside electron density profile including the main peak. Here we present peak electron density measurements from 37 deep dip orbits and describe conditions at the altitude of the main peak, including the electron temperature and composition of the ionosphere and neutral atmosphere. We find that the dependence of the peak electron density and the altitude of the main peak on solar zenith angle are well described by analytical photochemical theory. Additionally, we find that the electron temperatures at the main peak display a dependence on solar zenith angle that is consistent with the observed variability in the peak electron density. Several peak density measurements were made in regions of large crustal magnetic field, but there is no clear evidence that the crustal magnetic field strength influences the peak electron density, peak altitude, or electron temperature. Finally, we find that the fractional abundance of O2+ and CO2+ at the peak altitude is variable but that the two species together consistently represent 95% of the total ion density.

  18. Ligand identification using electron-density mapcorrelations

    SciTech Connect

    Terwilliger, Thomas C.; Adams, Paul D.; Moriarty, Nigel W.; Cohn,Judith D.

    2006-12-01

    A procedure for the identification of ligands bound incrystal structuresof macromolecules is described. Two characteristics ofthe density corresponding to a ligand are used in the identificationprocedure. One is the correlation of the ligand density with each of aset of test ligands after optimization of the fit of that ligand to thedensity. The other is the correlation of a fingerprint of the densitywith the fingerprint of model density for each possible ligand. Thefingerprints consist of an ordered list of correlations of each the testligands with the density. The two characteristics are scored using aZ-score approach in which the correlations are normalized to the mean andstandard deviation of correlations found for a variety of mismatchedligand-density pairs, so that the Z scores are related to the probabilityof observing a particular value of the correlation by chance. Theprocedure was tested with a set of 200 of the most commonly found ligandsin the Protein Data Bank, collectively representing 57 percent of allligands in the Protein Data Bank. Using a combination of these twocharacteristics of ligand density, ranked lists of ligand identificationswere made for representative (F-o-F-c) exp(i phi(c)) difference densityfrom entries in the Protein Data Bank. In 48 percent of the 200 cases,the correct ligand was at the top of the ranked list of ligands. Thisapproach may be useful in identification of unknown ligands in newmacromolecular structures as well as in the identification of whichligands in a mixture have bound to a macromolecule.

  19. A new method for determining the plasma electron density using optical frequency comb interferometer

    SciTech Connect

    Arakawa, Hiroyuki Tojo, Hiroshi; Sasao, Hajime; Kawano, Yasunori; Itami, Kiyoshi

    2014-04-15

    A new method of plasma electron density measurement using interferometric phases (fractional fringes) of an optical frequency comb interferometer is proposed. Using the characteristics of the optical frequency comb laser, high density measurement can be achieved without fringe counting errors. Simulations show that the short wavelength and wide wavelength range of the laser source and low noise in interferometric phases measurements are effective to reduce ambiguity of measured density.

  20. Contactless Mobility, Carrier Density, and Sheet Resistance Measurements on Si, GaN, and AlGaN/GaN High Electron Mobility Transistor (HEMT) Wafers

    DTIC Science & Technology

    2015-02-01

    structures grown on SiC substrates; and an unintentionally doped (UID) GaN on sapphire template. 15. SUBJECT TERMS Hall effect, high electron mobility...2. Experiment 2 3. Results 4 3.1 Standard n-type Si Sample 4 3.2 AlGaN/GaN HEMTs on SiC Sample Series 5 3.3 Si and UID GaN on Sapphire Pieces 12...AlGaN/GaN high electron mobility transistors (HEMTs) grown on SiC substrates, an unintentionally doped (UID) GaN epi layer on a sapphire substrate

  1. A study of electron density profiles in relation to ionization sources and ground-based radio wave absorption measurements, part 2

    NASA Technical Reports Server (NTRS)

    Gnanalingam, S.; Kane, J. A.

    1975-01-01

    The D-region ion production functions are used to calculate the relationship between radio wave absorption and the flux level of X-rays in the 1-8A wavelength band. In order to bring this calculation into agreement with the empirically established relationship, it was found necessary to reduce by, a factor of about 5, the Meira nitric oxide densities below 90 km.

  2. Gutzwiller density functional theory for correlated electron systems

    SciTech Connect

    Ho, K. M.; Schmalian, J.; Wang, C. Z.

    2008-02-04

    We develop a density functional theory (DFT) and formalism for correlated electron systems by taking as reference an interacting electron system that has a ground state wave function which exactly obeys the Gutzwiller approximation for all one-particle operators. The solution of the many-electron problem is mapped onto the self-consistent solution of a set of single-particle Schroedinger equations, analogously to standard DFT-local density approximation calculations.

  3. Electron and ion densities in interstellar clouds

    NASA Technical Reports Server (NTRS)

    Glassgold, A. E.; Langer, W. D.

    1974-01-01

    A quantitative theory of ionization in diffuse clouds is developed which includes H(+) charge exchange with O. Dissociative charge exchange of He(+) with H2 plays an important role in the densities of H(+) and He(+). The abundance of HD is also discussed.

  4. The Influence of Energetic Electrons on the Cassini Langmuir Probe at Saturn : Deriving Large Electron Temperatures and Small Electron Densities

    NASA Astrophysics Data System (ADS)

    Garnier, P.; Wahlund, J.; Holmberg, M.; Lewis, G.; Schippers, P.; Thomsen, M. F.; Rochel Grimald, S.; Gurnett, D. A.; Coates, A. J.; Dandouras, I. S.; Waite, J. H.

    2013-12-01

    The Langmuir probes (LPs) are commonly used to investigate the cold plasma characteristics in planetary ionospheres/magnetospheres. The LPs performances are limited to low temperatures (i.e. below 5-10 eV at Saturn) and large densities (above several particles/cm3). A strong sensitivity of the Cassini LP measurements to energetic electrons (hundreds eV) may however be observed at Saturn in the L Shell range L=6-10 RS. These electrons impact the surface of the probe and generate a detectable current of secondary electrons. We investigated the influence of such electrons on the current-voltage (I-V) characteristics (for negative potentials), showing that both the DC level and slope of the I-V curve are modified. The influence of energetic electrons may be interpreted in terms of the critical and anticritical temperatures concept that is important for spacecraft charging studies. Estimations of the maximum secondary yield value for the LP surface are obtained without using laboratory measurements. Empirical and theoretical methods were developed to reproduce the influence of the energetic electrons with a reasonable precision. Conversely, this modelling allows us to derive useful information about the energetic electrons from the LP observations : some information about their pitch angle anisotropy (if combined with the data from a single CAPS ELS anode), as well as an estimate of the electron temperature (in the range 100-300 eV) and of the electron density (above 0.1 particles/cm3). This enlarges the LP measurements capabilities when the influence of the energetic electrons is large (essentially near L=6-10 RS at Saturn). The understanding of this influence may be used for other missions using Langmuir probes, such as the future missions JUICE at Jupiter, BepiColombo at Mercury, or even the probes in the Earth magnetosphere.

  5. Measuring Air Density in the Introductory Lab

    ERIC Educational Resources Information Center

    Calza, G.; Gratton, L. M.; Lopez-Arias, T.; Oss, S.

    2010-01-01

    The measurement of the mass, or the density, of air can easily be done with very simple materials and offers many interesting phenomena for discussion--buoyancy and its effects being the most obvious but not the only one. Many interesting considerations can be done regarding the behavior of gases, the effect of the external conditions in the…

  6. A study of electron density profiles in relation to ionization sources and ground-based radio wave absorption measurements, part 1

    NASA Technical Reports Server (NTRS)

    Gnanalingam, S.; Kane, J. A.

    1973-01-01

    An extensive set of ground-based measurements of the diurnal variation of medium frequency radio wave adsorption and virtual height is analyzed in terms of current understanding of the D- and lower E-region ion production and loss process. When this is done a gross discrepancy arises, the source of which is not known.

  7. Measurement of density and temperature in a hypersonic turbulent boundary layer using the electron beam fluorescence technique. Ph.D. Thesis. Final Report, 1 Oct. 1969 - 1 Sep. 1972

    NASA Technical Reports Server (NTRS)

    Mcronald, A. D.

    1975-01-01

    Mean density and temperature fluctuations were measured across the turbulent, cooled-wall boundary layer in a continuous hypersonic (Mach 9.4) wind tunnel in air, using the nitrogen fluorescence excited by a 50 kV electron beam. Data were taken at three values of the tunnel stagnation pressure, the corresponding free stream densities being equivalent to 1.2, 4.0, and 7.4 torr at room temperature, and the boundary layer thicknesses about 4.0, 4.5, and 6.0 inches. The mean temperature and density profiles were similar to those previously determined in the same facility by conventional probes (static and pitot pressure, total temperature). A static pressure variation of about 50% across the boundary layer was found, the shape of the variation changing somewhat for the three stagnation pressure levels. The quadrupole model for rotational temperature spectra gave closer agreement with the free stream isentropic level (approximately 44 K) than the dipole model.

  8. Neutral Atmosphere Properties Determining D-region Electron Densities

    NASA Technical Reports Server (NTRS)

    Taubenheim, J.

    1984-01-01

    The increasing discoveries of various manifestations of meteorological control of the D region ionization and the growth of techniques for its measurement provide a challenge to meteorologists to test their insight into middle atmosphere processes with the physical interpretation of D layer phenomena. Models for ion production due to photoionization of minor atmospheric nitric oxide by quasi-monochromatic solar Lyman-alpha radiation are presented. A ground based measuring technique using low frequency radio reflection heights is briefly described and an approach to the interpretation of data acquired by this method is discussed. It is shown that D region electron density variations can provide an efficient diagnostic tool for the detection of perturbations of the circulation state of the middle atmosphere.

  9. Medical Electronics and Physiological Measurement.

    ERIC Educational Resources Information Center

    Cochrane, T.

    1989-01-01

    Described are developments in medical electronics and physiological measurement. Discussed are electrocardiology, audiology, and urology as mature applications; applied potential tomography, magnetic stimulation of nerves, and laser Doppler flowmetry as new techniques; and optical sensors, ambulatory monitoring, and biosensors as future…

  10. Cassini INMS measurements of Enceladus plume density

    NASA Astrophysics Data System (ADS)

    Perry, M. E.; Teolis, B. D.; Hurley, D. M.; Magee, B. A.; Waite, J. H.; Brockwell, T. G.; Perryman, R. S.; McNutt, R. L.

    2015-09-01

    During six encounters between 2008 and 2013, the Cassini Ion and Neutral Mass Spectrometer (INMS) made in situ measurements deep within the Enceladus plumes. Throughout each encounter, those measurements contained density variations that reflected the nature of the source, particularly of the high-velocity jets. Since the dominant constituent of the vapor, H2O, interacted with the walls of the INMS inlet, we track changes in the external vapor density by using more-volatile species that responded promptly to those changes. However, the most-abundant volatiles, at 28 u and 44 u, behaved differently from each other in the plume. At least a portion of their differences may be attributed to mass-dependent thermal velocity that affects Mach number in the high-velocity jets. Variations between volatiles place an emphasis on modeling as a means to construct overall plume density from the volatile densities and to investigate the velocity, gas temperature, and location of the jets. Ice grains, entering the INMS aperture add complexity and uncertainty to the physical interpretation of the data because the grains modified the INMS measurements. A comparison of data from the last three encounters, E14, E17, and E18, are consistent with the VIMS observation of variability in jet production and a slower, more diffuse gas flux from the four sulci or tiger stripes. We provide and describe the INMS data, its processing, and its uncertainty.

  11. A statistical study of magnetospheric electron density using the Cluster spacecraft

    NASA Astrophysics Data System (ADS)

    Sandhu, J. K.; Yeoman, T. K.; Fear, R. C.; Dandouras, I.

    2016-11-01

    Observations from the WHISPER (Waves of High frequency and Sounder for Probing of Electron density by Relaxation) instrument on board Cluster, for the interval spanning 2001-2012, are utilized to determine an empirical model describing the total electron density along closed geomagnetic field lines. The model, representing field lines in the region of 4.5≤L < 9.5, includes dependences on L and magnetic local time. Data verification tests ensured that the WHISPER data set provided unbiased measurements for low-density regions, including comparisons with Plasma Electron and Current Experiment and Electric Field and Waves observations. The model was determined by modeling variations in the electron density along the field lines, which is observed to follow a power law distribution along the geomagnetic field at high latitudes, with power law index values ranging from approximately 0.0 to 1.2. However, a localized peak in electron density close to the magnetic equator is observed, which is described using a Gaussian peak function, with the electron density peak ranging as high as 10 cm-3 above the background power law dependence. The resulting model illustrates some key features of the electron density spatial distribution. The role of the number density distribution, represented by the empirical electron density model, in determining the total plasma mass density is also explored. By combining the empirical electron density model with an empirical average ion mass model, the total plasma mass density distribution is inferred, which includes contributions of both the number density and ion composition of the plasma in the region.

  12. High Current Density Scandate Cathodes for Future Vacuum Electronics Applications

    DTIC Science & Technology

    2008-05-30

    braze alloy . The structure was fired in a furnace at 16500 C for 15 minutes. The resultant structure was sectioned to determine if the scandium flowed...Density Cathodes for Future Vacuum Electronics Applications FA9550-07-C-0063 7. PERFORMING ORGANIZATION NAME(S) AND ADDRESS(ES) 8. PERFORMING ORGANIZATION...Current Density Scandate Cathodes for Future Vacuum Electronics Applications USAF/AFRL Contract Number FA9550-07-C-0063 Final Report Calabazas Creek

  13. New link between conceptual density functional theory and electron delocalization.

    PubMed

    Matito, Eduard; Putz, Mihai V

    2011-11-17

    In this paper we give a new definition of the softness kernel based on the exchange-correlation density. This new kernel is shown to correspond to the change of electron fluctuation upon external perturbation, thus helping to bridge the gap between conceptual density functional theory and some tools describing electron localization in molecules. With the aid of a few computational calculations on diatomics we illustrate the performance of this new computational tool.

  14. Waves in relativistic electron beam in low-density plasma

    NASA Astrophysics Data System (ADS)

    Sheinman, I.; Sheinman (Chernenco, J.

    2016-11-01

    Waves in electron beam in low-density plasma are analyzed. The analysis is based on complete electrodynamics consideration. Dependencies of dispersion laws from system parameters are investigated. It is shown that when relativistic electron beam is passed through low-density plasma surface waves of two types may exist. The first type is a high frequency wave on a boundary between the beam and neutralization area and the second type wave is on the boundary between neutralization area and stationary plasma.

  15. Two-color terahertz interferometer based on the frequency-splitted orthogonal polarization modes of the water vapor laser and designed for measuring the electron density profile in the L-2M stellarator

    SciTech Connect

    Letunov, A. A.; Logvinenko, V. P.; Zav'yalov, V. V.

    2008-03-15

    An upgraded diagnostics for measuring the electron density profile in the L-2M stellarator is proposed. The existing diagnostics employs an interferometer based on an HCN laser with a mechanical frequency shifter and unmagnetized InSb detectors cooled with liquid helium. It is proposed to replace the HCN laser with a water vapor laser operating simultaneously at two wavelengths (220 and 118 {mu}m). Being equipped with an anisotropic exit mirror, the water vapor laser allows the generation of orthogonally polarized, frequency-splitted modes at each of these wavelengths with a frequency difference of several tens of kilohertzs. Such a scheme makes it possible to get rid of the mechanical frequency shifter. Moreover, simultaneous measurements at two wavelengths allow one to reliably separate the phase increments introduced by the plasma electron component and by variations in the lengths of the interferometer arms. To take full advantage of this scheme, specially developed cryogenic receivers consisting of Ge and InSb photodetectors placed one after another will be used. To increase the response of the system near {lambda} = 220 {mu}m, the InSb detector is placed in a Almost-Equal-To 0.55-T magnetic field.

  16. Influence of the electronic plasma density on the wave particle interaction

    NASA Astrophysics Data System (ADS)

    Sicard-Piet, Angelica; Boscher, Daniel

    2013-04-01

    The wave particle interaction, which is well known to be a major phenomenon in the electron radiation belts dynamics, is based on two main parameters: the characteristics of the wave (type of wave, intensity,…) and the characteristics of the ambient plasma. In this work we studied the second parameter. On one side, the electronic plasma density can be derived from in-situ measurements. On the other side, several empirical models exist: GCPM, IZMIRAN or Carpenter models. Here, we compared electronic plasma densities derived from in-situ measurements each other and with existing models. Then, we investigated on the electronic plasma density distribution to distinguish the inside to the outside plasmasphere. Finally, the effect of the electronic plasma density on the diffusion coefficients due to wave particle interaction has been studied via a numerical code, called WAPI, based on quasi linear theory.

  17. Radiance Measurement for Low Density Mars Entry

    NASA Technical Reports Server (NTRS)

    Cruden, Brett A.

    2012-01-01

    We report measurements of radiance behind a shock wave in Martian simulant (96% CO2, 4% N2) atmosphere at conditions relevant for aerodynamic decelerators. Shock waves are generated in the NASA Ames Electric Arc Shock Tube (EAST) facility at velocities from 6-8 km/s and freestream densities from 1.2-5.9 x 10(exp -4) kilograms per cubic meter (0.05-0.25 Torr, corresponding to 35-50 km altitude). Absolute radiance is measured as a function of wavelength and position in the shock. Radiance measurements extend from the vacuum ultraviolet to near infrared (120-1650 nm). As at higher density/velocity, radiation is dominate by CO 4th positive radiation in the vacuum ultraviolet, though CN contribution is also significant. At most low density conditions, the shock does not relax to equilibrium over several centimeters. A small number of measurements in the mid-infrared were performed to quantify radiation from the fundamental vibrational transition in CO, and this is found to be a minor contributor to the overall radiance at these speeds. Efforts to extend test time and reliability in the 60 cm (24) shock tube will be discussed in the full paper.

  18. Long-term observations of D-region electron densities at high and middle northern latitudes

    NASA Astrophysics Data System (ADS)

    Singer, Werner; Keuer, Dieter; Friedrich, Martin; Strelnikova, Irina; Latteck, Ralph

    D-region electron densities are estimated using Doppler radars at frequencies around 3 MHz in Andenes, Norway (69.3°N, 16.0°E) since summer 2003 and in Juliusruh, Germany (54.6°N, 13.4°E) since summer 2006. Both experiments utilize partial reflections of ordinary and extraordinary component waves from scatterers in the altitude range 50-90 km to estimate electron number densities from differential absorption (DAE) and differential phase (DPE) measurements. Height profiles of electron density are obtained between about 55 km and 90 km with sampling times of 2-3 minutes and height resolution of 1.5 km at Andenes and 3 km at Juliusruh. The electron density profiles independently derived from DAE and DPE measurements agree remarkably well. The radar results are compared with co-located simultaneously measured electron densities by rocket-borne radio wave propagation experiments (differential absorption, Faraday rotation, and impedance probe) in Andenes with good agreement between insitu and ground-based measurements. The diurnal and seasonal variability of electron densities as observed at high and mid-latitudes under quiet ionospheric conditions is presented and compared to the corresponding electron density profiles of the International Reference Ionosphere. The response of D-region ionization to regular solar activity variation as well as to solar activity storms and geomagnetic disturbances has been studied at polar latitudes. Characteristic electron density variations are found during downwelling events of nitric oxide due to strong vertical coupling during stratospheric warming events. In addition, we discuss the inter-relation between D-region electron densities from radar observations, riometer absorption, and the empirical model IMAZ at different levels of solar activity and during particle precipitation events.

  19. Extracting electron transfer coupling elements from constrained density functional theory

    NASA Astrophysics Data System (ADS)

    Wu, Qin; Van Voorhis, Troy

    2006-10-01

    Constrained density functional theory (DFT) is a useful tool for studying electron transfer (ET) reactions. It can straightforwardly construct the charge-localized diabatic states and give a direct measure of the inner-sphere reorganization energy. In this work, a method is presented for calculating the electronic coupling matrix element (Hab) based on constrained DFT. This method completely avoids the use of ground-state DFT energies because they are known to irrationally predict fractional electron transfer in many cases. Instead it makes use of the constrained DFT energies and the Kohn-Sham wave functions for the diabatic states in a careful way. Test calculations on the Zn2+ and the benzene-Cl atom systems show that the new prescription yields reasonable agreement with the standard generalized Mulliken-Hush method. We then proceed to produce the diabatic and adiabatic potential energy curves along the reaction pathway for intervalence ET in the tetrathiafulvalene-diquinone (Q-TTF-Q) anion. While the unconstrained DFT curve has no reaction barrier and gives Hab≈17kcal /mol, which qualitatively disagrees with experimental results, the Hab calculated from constrained DFT is about 3kcal /mol and the generated ground state has a barrier height of 1.70kcal/mol, successfully predicting (Q-TTF-Q)- to be a class II mixed-valence compound.

  20. Electronics reliability and measurement technology

    NASA Technical Reports Server (NTRS)

    Heyman, Joseph S. (Editor)

    1987-01-01

    A summary is presented of the Electronics Reliability and Measurement Technology Workshop. The meeting examined the U.S. electronics industry with particular focus on reliability and state-of-the-art technology. A general consensus of the approximately 75 attendees was that "the U.S. electronics industries are facing a crisis that may threaten their existence". The workshop had specific objectives to discuss mechanisms to improve areas such as reliability, yield, and performance while reducing failure rates, delivery times, and cost. The findings of the workshop addressed various aspects of the industry from wafers to parts to assemblies. Key problem areas that were singled out for attention are identified, and action items necessary to accomplish their resolution are recommended.

  1. Two-dimensional time resolved measurements of toroidal velocity correlated with density blobs in magnetized plasmas

    SciTech Connect

    Labit, B.; Furno, I.; Fasoli, A.; Podesta, M.

    2008-08-15

    A new method for toroidal velocity measurements with Mach probes is presented. This technique is based on the conditional sampling technique, the triggering events being density blobs. A reconstruction of the time resolved two-dimensional profile of electron density, electron temperature, plasma potential, and toroidal velocity is possible with a single point measurement on a shot-to-shot basis.

  2. Density and Temperature Measurements in a Solar Active Region

    NASA Astrophysics Data System (ADS)

    Warren, Harry P.; Winebarger, Amy R.

    2003-10-01

    We present electron density and temperature measurements from an active region observed above the limb with the Solar Ultraviolet Measurements of Emitted Radiation spectrometer on the Solar and Heliospheric Observatory. Density-sensitive line ratios from Si VIII and S X indicate densities greater than 108 cm-3 as high as 200" (or 145 Mm) above the limb. At these heights, static, uniformly heated loop models predict densities close to 107 cm-3. Differential emission measure analysis shows that the observed plasma is nearly isothermal with a mean temperature of about 1.5 MK and a dispersion of about 0.2 MK. Both the differential emission measure and the Si XI/Si VIII line ratios indicate only small variations in the temperature at the heights observed. These measurements confirm recent observations from the Transition Region and Coronal Explorer of ``overdense'' plasma at temperatures near 1 MK in solar active regions. Time-dependent hydrodynamic simulations suggest that impulsive heating models can account for the large densities, but they have a difficult time reproducing the narrow range of observed temperatures. The observations of overdense, nearly isothermal plasma in the solar corona provide a significant challenge to theories of coronal heating.

  3. Measurement of Electron Clouds in Large Accelerators by Microwave Dispersion

    SciTech Connect

    De Santis, S.; Byrd, J.M.; Caspers, F.; Krasnykh, A.; Kroyer, T.; Pivi, M.T.F.; Sonnad, K.G.; /LBL, Berkeley

    2008-03-19

    Clouds of low energy electrons in the vacuum beam pipes of accelerators of positively charged particle beams present a serious limitation for operation at high currents. Furthermore, it is difficult to probe their density over substantial lengths of the beam pipe. We have developed a novel technique to directly measure the electron cloud density via the phase shift induced in a TE wave transmitted over a section of the accelerator and used it to measure the average electron cloud density over a 50 m section in the positron ring of the PEP-II collider at the Stanford Linear Accelerator Center.

  4. Measurement of electron clouds in large accelerators by microwave dispersion.

    PubMed

    De Santis, S; Byrd, J M; Caspers, F; Krasnykh, A; Kroyer, T; Pivi, M T F; Sonnad, K G

    2008-03-07

    Clouds of low energy electrons in the vacuum beam pipes of accelerators of positively charged particle beams present a serious limitation for operation at high currents. Furthermore, it is difficult to probe their density over substantial lengths of the beam pipe. We have developed a novel technique to directly measure the electron cloud density via the phase shift induced in a TE wave transmitted over a section of the accelerator and used it to measure the average electron cloud density over a 50 m section in the positron ring of the PEP-II collider at the Stanford Linear Accelerator Center.

  5. Warm O(+) polar wind and the DE-1 polar cap electron density profile

    NASA Technical Reports Server (NTRS)

    Ho, C. W.; Horwitz, J. L.

    1993-01-01

    Theoretical steady state semikinetic polar wind density profiles, based on DE1/RIMS polar wind data (up to 3700 km), were obtained which agree very well with the power law electron density profile measured by the DE1/PWI for high altitudes. The polar wind is found to be O(+) dominated for the full altitude range considered (up to 8 R(E)). Multiple solutions are obtained for various combinations of base altitude ion temperatures and electron temperatures, such that the densities fit the Persoon et al. (1983) profile. For example, good fits to measured density profile are found for low base ion temperatures (5000 K) and high electron temperatures (9000 K), and also for unheated H(+) and O(+)(3000 K) with electron temperatures of 11,000 K. Below 2.8 R(E) the theoretical polar wind density deviates somewhat from the r exp -3.85 power law. It is concluded that this theoretical polar wind density profile, with a sum of base electron and ion temperatures of 14,000 K, yields a close match with the measured DE-1 electron density profile.

  6. Electric Field and Density Measurements with STEREO-SWaves.

    NASA Astrophysics Data System (ADS)

    Kellogg, P. J.; Goetz, K.; Monson, S. J.; Bale, S. D.; Maksimovic, M.

    2007-12-01

    The STEREO experiment SWaves has a low frequency part which is designed to make measurements of low frequency electric fields and rapid measurements of density fluctuations, using the three 6 meter stacer monopole antennas. The short antennas of STEREO respond both to density fluctuations and to electric fields. Therefore, it is desired to obtain four quantities, density and 3 components of electric field, from three measurements, the potentials on the three orthogonal antennas relative to the spacecraft, which requires some additional information. One possibility is to add a fourth equation implied by the large plasma conductivity, so large that electric field parallel to the magnetic field is zero, a condition which has often been used in electric field measurements. Under selected conditions, this seems to work. There are also conditions, for example ion acoustic waves, where the responses to density fluctuations and to electric fields are available from dispersion relations, and this provides another possible solution. A situation where it is not likely that the parallel electric field is zero is the case of solitary, intense bursts of Langmuir waves. For this case, it is expected that there is an electron density depression due to the ponderomotive pressure, and a resulting low frequency electric field from the non-neutrality which would be expected to have components parallel to the magnetic field. Examples will be discussed.

  7. Seasonal and solar activity variability of D-region electron density at 69°N

    NASA Astrophysics Data System (ADS)

    Singer, Werner; Latteck, Ralph; Friedrich, Martin; Wakabayashi, Makato; Rapp, Markus

    2011-06-01

    A narrow beam Doppler radar operating at 3.17 MHz and installed close to the Andøya Rocket Range in Andenes, Norway, (69.3°N, 16.0°E) has been providing electron densities in the lower ionosphere since summer 2003. The experiment utilizes partial reflection of ordinary and extraordinary component waves from scatterers in the altitude range 50-95 km to estimate electron densities from differential absorption and differential phase measurements. These ground-based observations are in good agreement with concurrent rocket-borne radio wave propagation measurements at Andenes. Results of the diurnal and seasonal variability of electron densities and the response of D-region electron densities to solar activity storms are presented.

  8. Interactive Database of Pulsar Flux Density Measurements

    NASA Astrophysics Data System (ADS)

    Koralewska, O.; Krzeszowski, K.; Kijak, J.; Lewandowski, W.

    2012-12-01

    The number of astronomical observations is steadily growing, giving rise to the need of cataloguing the obtained results. There are a lot of databases, created to store different types of data and serve a variety of purposes, e. g. databases providing basic data for astronomical objects (SIMBAD Astronomical Database), databases devoted to one type of astronomical object (ATNF Pulsar Database) or to a set of values of the specific parameter (Lorimer 1995 - database of flux density measurements for 280 pulsars on the frequencies up to 1606 MHz), etc. We found that creating an online database of pulsar flux measurements, provided with facilities for plotting diagrams and histograms, calculating mean values for a chosen set of data, filtering parameter values and adding new measurements by the registered users, could be useful in further studies on pulsar spectra.

  9. Density-shear instability in electron magneto-hydrodynamics

    SciTech Connect

    Wood, T. S. Hollerbach, R.; Lyutikov, M.

    2014-05-15

    We discuss a novel instability in inertia-less electron magneto-hydrodynamics (EMHD), which arises from a combination of electron velocity shear and electron density gradients. The unstable modes have a lengthscale longer than the transverse density scale, and a growth-rate of the order of the inverse Hall timescale. We suggest that this density-shear instability may be of importance in magnetic reconnection regions on scales smaller than the ion skin depth, and in neutron star crusts. We demonstrate that the so-called Hall drift instability, previously argued to be relevant in neutron star crusts, is a resistive tearing instability rather than an instability of the Hall term itself. We argue that the density-shear instability is of greater significance in neutron stars than the tearing instability, because it generally has a faster growth-rate and is less sensitive to geometry and boundary conditions. We prove that, for uniform electron density, EMHD is “at least as stable” as regular, incompressible MHD, in the sense that any field configuration that is stable in MHD is also stable in EMHD. We present a connection between the density-shear instability in EMHD and the magneto-buoyancy instability in anelastic MHD.

  10. Electron density profiles from ionograms - Underlying ionization corrections and their comparison with rocket results

    NASA Technical Reports Server (NTRS)

    Wright, J. W.; Paul, A. K.; Mechtly, E. A.

    1975-01-01

    Electron density profiles from nine daytime rocket flights at Wallops Island, Va., conducted at high and low levels of solar activity are compared with profiles calculated by inversion of ionograms obtained at the same times and location. Sources of error and uncertainty in the ionogram inversion are discussed, as are means for their amelioration. In most cases, agreement between the two kinds of measurement within a few percent in electron density and within a few percent of a scale height can be achieved.

  11. Effective mass in bilayer graphene at low carrier densities: The role of potential disorder and electron-electron interaction

    NASA Astrophysics Data System (ADS)

    Li, J.; Tan, L. Z.; Zou, K.; Stabile, A. A.; Seiwell, D. J.; Watanabe, K.; Taniguchi, T.; Louie, Steven G.; Zhu, J.

    2016-10-01

    In a two-dimensional electron gas, the electron-electron interaction generally becomes stronger at lower carrier densities and renormalizes the Fermi-liquid parameters, such as the effective mass of carriers. We combine experiment and theory to study the effective masses of electrons and holes me* and mh* in bilayer graphene in the low carrier density regime on the order of 1 ×1011c m-2 . Measurements use temperature-dependent low-field Shubnikov-de Haas oscillations observed in high-mobility hexagonal boron nitride supported samples. We find that while me* follows a tight-binding description in the whole density range, mh* starts to drop rapidly below the tight-binding description at a carrier density of n =6 ×1011c m-2 and exhibits a strong suppression of 30% when n reaches 2 ×1011c m-2 . Contributions from the electron-electron interaction alone, evaluated using several different approximations, cannot explain the experimental trend. Instead, the effect of the potential fluctuation and the resulting electron-hole puddles play a crucial role. Calculations including both the electron-electron interaction and disorder effects explain the experimental data qualitatively and quantitatively. This Rapid Communication reveals an unusual disorder effect unique to two-dimensional semimetallic systems.

  12. Measuring Entanglement Spectrum via Density Matrix Exponentiation

    NASA Astrophysics Data System (ADS)

    Zhu, Guanyu; Seif, Alireza; Pichler, Hannes; Zoller, Peter; Hafezi, Mohammad

    Entanglement spectrum (ES), the eigenvalues of the reduced density matrix of a subsystem, serves as a powerful theoretical tool to study many-body systems. For example, the gap and degeneracies of the entanglement spectrum have been used to identify various topological phases. However, the usefulness of such a concept in real experiments has been debated, since it is believed that obtaining the ES requires full state tomography, at a cost which exponentially grows with the systems size. Inspired by a recent density matrix exponentiation technique, we propose a scheme to measure ES by evolving the system with a Hamiltonian that is the subsystem's own reduced density matrix. Such a time evolution can be induced by an ancilla photon that is coupled to multiple qubits at the same time. The phase associated with the time evolution can be detected and converted into ES through either a digital or an analogue scheme. The digital scheme involves a modified quantum phase estimation algorithm based on random time evolution, while the analogue scheme is in the spirit of Ramsey interferometry. Both schemes are not limited by the size of the system, and are especially sensitive to the gap and degeneracies. We also discuss the implementation in cavity/circuit-QED and ion trap systems.

  13. Electron density and parallel electric field distribution of the auroral density cavity

    NASA Astrophysics Data System (ADS)

    Alm, L.; Marklund, G. T.; Karlsson, T.

    2015-11-01

    We present an event study in which Cluster satellites C1 and C3 encounters the flux tube of a stable auroral arc in the premidnight sector. C1 observes the midcavity, while C3 enters the flux tube of the auroral arc at an altitude which is below the acceleration region, before crossing into the top half of the acceleration region. This allows us to study the boundary between the ionosphere and the density cavity, as well as large portion of the upper density cavity. The position of the two satellites, in relation to the acceleration region, is described using a pseudo altitude derived from the distribution of the parallel potential drop above and below the satellites. The electron density exhibits an anticorrelation with the pseudo altitude, indicating that the lowest electron densities are found near the top of the density cavity. Over the entire pseudo altitude range, the electron density distribution is similar to a planar sheath, formed out of a plasma sheet dominated electron distribution, in response to the parallel electric field of the acceleration region. This indicates that the parallel electric fields on the ionosphere-cavity boundary, as well as the midcavity parallel electric fields, are part of one unified structure rather than two discrete entities. The results highlight the strong connection between the auroral density cavity and auroral acceleration as well as the necessity of studying them in a unified fashion.

  14. Imaging polychromator for density measurements of polystyrene pellet cloud on the Large Helical Device.

    PubMed

    Sharov, I A; Sergeev, V Yu; Miroshnikov, I V; Tamura, N; Kuteev, B V; Sudo, S

    2015-04-01

    Experimental data on spatial distributions of a pellet cloud electron density are necessary for the development of many applications of pellet injection, namely, plasma fuelling, discharge control, and plasma diagnostics. An improved approach of electron density measurements inside the cloud of a polystyrene pellet ablating in hot plasma of the large helical device is described. Density values of (1-30) × 10(16) cm(-3) depending on the background plasma parameters and distance from the solid pellet were measured.

  15. Density Measurement of Ethanol Blended Fuels

    NASA Astrophysics Data System (ADS)

    Man, John

    Density measurements for petro-ethanol blended fuels of various mixture ratios were conducted at temperatures from 5°C to 40°C using an oscillatory densitometer at the National Measurement Institute, Australia (NMIA). The petrol and ethanol fuels used for the preparation of samples of ethanol blends were supplied directly from a local petroleum refinery. Results were within the lower end of 0.06% repeatability and 0.3% reproducibility of the ASTM D4052-2011 method. The volume correction factors (VCF) for petrol and ethanol obtained from the measurement results agreed to within 0.1% and 0.01% of the values calculated as per American Petroleum Institute Standard 2540 Chapter 11.1 and 11.3.3 respectively. Based on a simple volume-mixture model, an equation was derived to calculate the VCF for petrol-ethanol blends. The measured and calculated values of VCF were in agreement within 0.1%. This paper presents the measurement method, results and the development of an equation for calculation of VCF for petro-ethanol blends. Note from Publisher: This article contains the abstract only.

  16. Isotope Generated Electron Density in Silicon Carbide Direct Energy Converters

    DTIC Science & Technology

    2006-10-01

    output of a diode into a resistively loaded circuit. This paper describes the use of a nuclear scattering code ( MCNPX ) to calculate the increased...used in the MCNPX calculations . The range constant supplied in section 3.2 (9) must be multiplied by the density of the material used. The density... MCNPX code. Instead, we are only modeling the SiC material and attempting to calculate how many free-electrons are being generated within as a

  17. Mobility of electrons in supercritical krypton: Role of density fluctuations

    SciTech Connect

    Nishikawa, Masaru; Holroyd, Richard A.; Preses, Jack M.

    2007-07-07

    Excess electrons were generated in supercritical krypton by means of pulsed x-ray irradiation, and the electron transport phenomena were studied. Electron signals immediately after a 30 ps pulse showed a distinctive feature characteristic of the presence of the Ramsauer-Townsend minimum in the momentum transfer cross section. The dependence of the drift velocity v{sub D} on field strength was found to be concave upward in the low field region and then to go through a maximum with increasing field strength, which is also typical of the presence of a minimum in the scattering cross section at an intermediate field strength. A minimum in the electron mobility was observed at about one-half the critical density. The acoustical phonon scattering model, which successfully explained the mobility change in this density region in supercritical xenon, was again found to account for the mobility in supercritical krypton.

  18. Ionospheric topside models compared with experimental electron density profiles

    NASA Astrophysics Data System (ADS)

    Coisson, P.; Radicella, S. M.

    2003-04-01

    In the last couple of years an increasing number of topside electron density profiles has been made available through the Internet to the scientific community. This kind of data is particularly important for ionospheric modeling purposes, since the experimental information on the electron density above the ionosphere maximum of ionization is very scarce. The present work analyses the behavior of the NeQuick and IRI models, adopted by the ITU-R recommendation P.531-5, with respect to the topside electron density profiles available in the databases of ISIS2, IK19 and Cosmos-1809 satellites. Experimental total electron content (TEC) from the F2 peak up to satellite height and electron densities at fixed heights above that peak have been compared with values computed with the models. A wide range of different conditions (solar activity, local time, geographical and geomagnetic position has been considered). The analysis done allows to point out the behavior of the models and the improvement needed to allow a better reproduction of the experimental results.

  19. Statistical quality indicators for electron-density maps

    SciTech Connect

    Tickle, Ian J.

    2012-04-01

    A likelihood-based metric for scoring the local agreement of a structure model with the observed electron density is described. The commonly used validation metrics for the local agreement of a structure model with the observed electron density, namely the real-space R (RSR) and the real-space correlation coefficient (RSCC), are reviewed. It is argued that the primary goal of all validation techniques is to verify the accuracy of the model, since precision is an inherent property of the crystal and the data. It is demonstrated that the principal weakness of both of the above metrics is their inability to distinguish the accuracy of the model from its precision. Furthermore, neither of these metrics in their usual implementation indicate the statistical significance of the result. The statistical properties of electron-density maps are reviewed and an improved alternative likelihood-based metric is suggested. This leads naturally to a χ{sup 2} significance test of the difference density using the real-space difference density Z score (RSZD). This is a metric purely of the local model accuracy, as required for effective model validation and structure optimization by practising crystallographers prior to submission of a structure model to the PDB. A new real-space observed density Z score (RSZO) is also proposed; this is a metric purely of the model precision, as a substitute for other precision metrics such as the B factor.

  20. Electron beam control using shock-induced density downramp injection

    NASA Astrophysics Data System (ADS)

    Swanson, K.; Tsai, H.-E.; Barber, S.; Lehe, R.; Mao, H.-S.; Steinke, S.; van Tilborg, J.; Geddes, C. G. R.; Leemans, W. P.

    2017-03-01

    In these experiments, we improve the quality of electrons injected along a shock-induced density downramp. We demonstrate that beam ellipticity and steering are influenced by the shock front tilt, and we present simple models to explain these effects. By adjusting the shock front angle, we minimize the beam's off-axis steering and ellipticity, producing high-quality electron beams over a tunable energy range.

  1. A simple and straightforward expression for curling probe electron density diagnosis in reactive plasmas

    NASA Astrophysics Data System (ADS)

    Arshadi, Ali; Brinkmann, Ralf Peter; Hotta, Masaya; Nakamura, Keiji

    2017-04-01

    Active plasma resonance spectroscopy (APRS) refers to the family of plasma diagnostic methods which utilize the ability of plasmas to resonate at frequencies close to the plasma frequency. APRS operates by exciting the plasma with a weak RF signal by means of a small electric probe. The response of the plasma is recorded by a network analyzer (NA). A mathematical model is applied to derive characteristics like the electron density and the electron temperature. The curling probe is a promising realization of APRS. The curling probe is well-qualified for the local measurement of the electron density in reactive plasmas. This spiral probe resonates in plasma at a larger density dependent frequency than the plasma frequency. This manuscript represents a simple and straightforward expression relating this resonance frequency to the electron density of the plasma. A good agreement is observed between the proposed expression and the results obtained from previous studies and numerical simulations.

  2. Comparisons of ionospheric electron density distributions reconstructed by GPS computerized tomography, backscatter ionograms, and vertical ionograms

    NASA Astrophysics Data System (ADS)

    Zhou, Chen; Lei, Yong; Li, Bofeng; An, Jiachun; Zhu, Peng; Jiang, Chunhua; Zhao, Zhengyu; Zhang, Yuannong; Ni, Binbin; Wang, Zemin; Zhou, Xuhua

    2015-12-01

    Global Positioning System (GPS) computerized ionosphere tomography (CIT) and ionospheric sky wave ground backscatter radar are both capable of measuring the large-scale, two-dimensional (2-D) distributions of ionospheric electron density (IED). Here we report the spatial and temporal electron density results obtained by GPS CIT and backscatter ionogram (BSI) inversion for three individual experiments. Both the GPS CIT and BSI inversion techniques demonstrate the capability and the consistency of reconstructing large-scale IED distributions. To validate the results, electron density profiles obtained from GPS CIT and BSI inversion are quantitatively compared to the vertical ionosonde data, which clearly manifests that both methods output accurate information of ionopsheric electron density and thereby provide reliable approaches to ionospheric soundings. Our study can improve current understanding of the capability and insufficiency of these two methods on the large-scale IED reconstruction.

  3. Electron density diagnostics in the 10-100 A interval for a solar flare

    NASA Technical Reports Server (NTRS)

    Brown, W. A.; Bruner, M. E.; Acton, L. W.; Mason, H. E.

    1986-01-01

    Electron density measurements from spectral-line diagnostics are reported for a solar flare on July 13, 1982, 1627 UT. The spectrogram, covering the 10-95 A interval, contained usable lines of helium-like ions C V, N VI, O VII, and Ne IX which are formed over the temperature interval 0.7-3.5 x 10 to the 6th K. In addition, spectral-line ratios of Si IX, Fe XIV, and Ca XV were compared with new theoretical estimates of their electron density sensitivity to obtain additional electron density diagnostics. An electron density of 3 x 10 to the 10th/cu cm was obtained. The comparison of these results from helium-like and other ions gives confidence in the utility of these tools for solar coronal analysis and will lead to a fuller understanding of the phenomena observed in this flare.

  4. The COSMOS-[O II] survey: evolution of electron density with star formation rate

    NASA Astrophysics Data System (ADS)

    Kaasinen, Melanie; Bian, Fuyan; Groves, Brent; Kewley, Lisa J.; Gupta, Anshu

    2017-03-01

    Star-forming galaxies at z > 1 exhibit significantly different properties to local galaxies of equivalent stellar mass. Not only are high-redshift star-forming galaxies characterized by higher star formation rates and gas fractions than their local counterparts, they also appear to host star-forming regions with significantly different physical conditions, including greater electron densities. To understand what physical mechanisms are responsible for the observed evolution of the star-forming conditions, we have assembled the largest sample of star-forming galaxies at z ∼ 1.5 with emission-line measurements of the {[O II]}λ λ 3726,3729 doublet. By comparing our z ∼ 1.5 sample to local galaxy samples with equivalent distributions of stellar mass, star formation rate and specific star formation rate we investigate the proposed evolution in electron density and its dependence on global properties. We measure an average electron density of 114_{-27}^{+28} cm^{-3} for our z ∼ 1.5 sample, a factor of 5 greater than the typical electron density of local star-forming galaxies. However, we find no offset between the typical electron densities of local and high-redshift galaxies with equivalent star formation rates. Our work indicates that the average electron density of a sample is highly sensitive to the star formation rates, implying that the previously observed evolution is mainly the result of selection effects.

  5. Accurate Measurement of Bone Density with QCT

    NASA Technical Reports Server (NTRS)

    Cleek, Tammy M.; Beaupre, Gary S.; Matsubara, Miki; Whalen, Robert T.; Dalton, Bonnie P. (Technical Monitor)

    2002-01-01

    The objective of this study was to determine the accuracy of bone density measurement with a new OCT technology. A phantom was fabricated using two materials, a water-equivalent compound and hydroxyapatite (HA), combined in precise proportions (QRM GrnbH, Germany). The phantom was designed to have the approximate physical size and range in bone density as a human calcaneus, with regions of 0, 50, 100, 200, 400, and 800 mg/cc HA. The phantom was scanned at 80, 120 and 140 KVp with a GE CT/i HiSpeed Advantage scanner. A ring of highly attenuating material (polyvinyl chloride or teflon) was slipped over the phantom to alter the image by introducing non-axi-symmetric beam hardening. Images were corrected with a new OCT technology using an estimate of the effective X-ray beam spectrum to eliminate beam hardening artifacts. The algorithm computes the volume fraction of HA and water-equivalent matrix in each voxel. We found excellent agreement between expected and computed HA volume fractions. Results were insensitive to beam hardening ring material, HA concentration, and scan voltage settings. Data from all 3 voltages with a best fit linear regression are displays.

  6. More systematic errors in the measurement of power spectral density

    NASA Astrophysics Data System (ADS)

    Mack, Chris A.

    2015-07-01

    Power spectral density (PSD) analysis is an important part of understanding line-edge and linewidth roughness in lithography. But uncertainty in the measured PSD, both random and systematic, complicates interpretation. It is essential to understand and quantify the sources of the measured PSD's uncertainty and to develop mitigation strategies. Both analytical derivations and simulations of rough features are used to evaluate data window functions for reducing spectral leakage and to understand the impact of data detrending on biases in PSD, autocovariance function (ACF), and height-to-height covariance function measurement. A generalized Welch window was found to be best among the windows tested. Linear detrending for line-edge roughness measurement results in underestimation of the low-frequency PSD and errors in the ACF and height-to-height covariance function. Measuring multiple edges per scanning electron microscope image reduces this detrending bias.

  7. Spectral density measurements of gyro noise

    NASA Technical Reports Server (NTRS)

    Truncale, A.; Koenigsberg, W.; Harris, R.

    1972-01-01

    Power spectral density (PSD) was used to analyze the outputs of several gyros in the frequency range from 0.01 to 200 Hz. Data were accumulated on eight inertial quality instruments. The results are described in terms of input angle noise (arcsec 2/Hz) and are presented on log-log plots of PSD. These data show that the standard deviation of measurement noise was 0.01 arcsec or less for some gyros in the passband from 1 Hz down 10 0.01 Hz and probably down to 0.001 Hz for at least one gyro. For the passband between 1 and 100 Hz, uncertainties in the 0.01 and 0.05 arcsec region were observed.

  8. Tethered two-point measurements of solitary auroral density cavities

    NASA Astrophysics Data System (ADS)

    Knudsen, D. J.; Wallis, D. D.; James, H. G.

    The OEDIPUS-C sounding rocket observed localized plasma density depletions in the topside auroral ionosphere using two Langmuir probes situated on separate subpayloads several hundred meters apart. One probe was biased in electron saturation (+5 V) and the second in ion saturation (-5 V). Both of these measurements are consistent with density depletions of tens of percent. The depletions have cross-field dimensions of tens of meters and occur in regions of VLF hiss, suggesting they are likely signatures of lower hybrid solitary structures. Time delays between event detections on the two subpayloads are consistent with spatially localized structures traversed in succession. The two-point measurements show directly that the cavities extend at least 800 m along the geomagnetic field line, and the apparent electric potential within them is depressed by roughly 0.5 V.

  9. Extreme atmospheric electron densities created by extensive air showers

    NASA Astrophysics Data System (ADS)

    Rutjes, Casper; Camporeale, Enrico; Ebert, Ute; Buitink, Stijn; Scholten, Olaf; Trinh, Gia

    2016-04-01

    A sufficient density of free electrons and strong electric fields are the basic requirements to start any electrical discharge. In the context of thunderstorm discharges it has become clear that in addition droplets and or ice particles are required to enhance the electric field to values above breakdown. In our recent study [1] we have shown that these three ingredients have to interplay to allow for lightning inception, triggered by an extensive air shower event. The extensive air showers are a very stochastic natural phenomenon, creating highly coherent bursts of extreme electron density in our atmosphere. Predicting these electron density bursts accurately one has to take the uncertainty of the input variables into account. To this end we use uncertainty quantification methods, like in [2], to post-process our detailed Monte Carlo extensive air shower simulations, done with the CORSIKA [3] software package, which provides an efficient and elegant way to determine the distribution of the atmospheric electron density enhancements. We will present the latest results. [1] Dubinova, A., Rutjes, C., Ebert, E., Buitink, S., Scholten, O., and Trinh, G. T. N. "Prediction of Lightning Inception by Large Ice Particles and Extensive Air Showers." PRL 115 015002 (2015) [2] G.J.A. Loeven, J.A.S. Witteveen, H. Bijl, Probabilistic collocation: an efficient nonintrusive approach for arbitrarily distributed parametric uncertainties, 45th AIAA Aerospace Sciences Meeting, Reno, Nevada, 2007, AIAA-2007-317 [3] Heck, Dieter, et al. CORSIKA: A Monte Carlo code to simulate extensive air showers. No. FZKA-6019. 1998.

  10. Pseudoconvexity of the atomic electron density: A numerical study

    NASA Astrophysics Data System (ADS)

    Esquivel, Rodolfo O.; Sagar, Robin P.; Smith, Vedene H., Jr.; Chen, Jiqiang; Stott, M. J.

    1993-06-01

    The curvature, ρ''(r), of the atomic electron density ρ(r) is studied using results from a bare-Coulomb-field (BCF) model, Hartree-Fock (HF), and configuration-interaction (CI) calculations. A region of nonconvexity in ρ(r), previously reported by Angulo, Dehesa, and Gálvez [Phys. Rev. A 42, 641 (1990)] for light atoms in a Hartree-Fock framework, is investigated for all atoms up to Z=92 and is found not to be an artifact of the basis set or the HF model. Numerical results for the BCF model show that the total electron density of an arbitrary number of closed shells is convex. However, for the same model with electrons filling orbitals according to Stoner's restriction we find that nonconvexity of the density is a periodic property appearing around closed-shell ground-state hydrogenic configurations. Cusp conditions, reported earlier by Esquivel et al. [Phys. Rev. A 47, 936 (1993)] for the second derivative of the BCF density are verified for model atoms with s and p subshells. Using wave functions of near-HF accuracy we have found a region of nonconvexity in ρ(r) for atoms with Z=3-6, 16-32, and 45-92. Highly correlated densities of CI and Hylleraas-type quality for atoms of Li and Be isoelectronic sequences show that the nonconvex region of ρ(r) is largely unaffected by the inclusion of electron correlation. These results, coupled with those from the BCF model, lead us to suggest that it is the bare Coulomb field of the nucleus that is mainly responsible for the appearance of nonconvex regions in atoms. Furthermore, the degree of nonconvexity is shown to decrease as Z increases along the isoelectronic series. The contributions of different spin densities to the nonconvex electron densities is also studied. Finally, the behavior of the curvature of the electron density far from the nucleus is investigated. The ratio ρ''(r)/ρ(r) is found to approach an asymptotic value from above or below, according to the magnitude of the ionization potential.

  11. Relations among several nuclear and electronic density functional reactivity indexes

    NASA Astrophysics Data System (ADS)

    Torrent-Sucarrat, Miquel; Luis, Josep M.; Duran, Miquel; Toro-Labbé, Alejandro; Solà, Miquel

    2003-11-01

    An expansion of the energy functional in terms of the total number of electrons and the normal coordinates within the canonical ensemble is presented. A comparison of this expansion with the expansion of the energy in terms of the total number of electrons and the external potential leads to new relations among common density functional reactivity descriptors. The formulas obtained provide explicit links between important quantities related to the chemical reactivity of a system. In particular, the relation between the nuclear and the electronic Fukui functions is recovered. The connection between the derivatives of the electronic energy and the nuclear repulsion energy with respect to the external potential offers a proof for the "Quantum Chemical le Chatelier Principle." Finally, the nuclear linear response function is defined and the relation of this function with the electronic linear response function is given.

  12. Bayesian electron density inference from JET lithium beam emission spectra using Gaussian processes

    NASA Astrophysics Data System (ADS)

    Kwak, Sehyun; Svensson, J.; Brix, M.; Ghim, Y.-C.; Contributors, JET

    2017-03-01

    A Bayesian model to infer edge electron density profiles is developed for the JET lithium beam emission spectroscopy (Li-BES) system, measuring Li I (2p-2s) line radiation using 26 channels with  ∼1 cm spatial resolution and 10∼ 20 ms temporal resolution. The density profile is modelled using a Gaussian process prior, and the uncertainty of the density profile is calculated by a Markov Chain Monte Carlo (MCMC) scheme. From the spectra measured by the transmission grating spectrometer, the Li I line intensities are extracted, and modelled as a function of the plasma density by a multi-state model which describes the relevant processes between neutral lithium beam atoms and plasma particles. The spectral model fully takes into account interference filter and instrument effects, that are separately estimated, again using Gaussian processes. The line intensities are inferred based on a spectral model consistent with the measured spectra within their uncertainties, which includes photon statistics and electronic noise. Our newly developed method to infer JET edge electron density profiles has the following advantages in comparison to the conventional method: (i) providing full posterior distributions of edge density profiles, including their associated uncertainties, (ii) the available radial range for density profiles is increased to the full observation range (∼26 cm), (iii) an assumption of monotonic electron density profile is not necessary, (iv) the absolute calibration factor of the diagnostic system is automatically estimated overcoming the limitation of the conventional technique and allowing us to infer the electron density profiles for all pulses without preprocessing the data or an additional boundary condition, and (v) since the full spectrum is modelled, the procedure of modulating the beam to measure the background signal is only necessary for the case of overlapping of the Li I line with impurity lines.

  13. FUSION++: A New Data Assimilative Model for Electron Density Forecasting

    NASA Astrophysics Data System (ADS)

    Bust, G. S.; Comberiate, J.; Paxton, L. J.; Kelly, M.; Datta-Barua, S.

    2014-12-01

    There is a continuing need within the operational space weather community, both civilian and military, for accurate, robust data assimilative specifications and forecasts of the global electron density field, as well as derived RF application product specifications and forecasts obtained from the electron density field. The spatial scales of interest range from a hundred to a few thousand kilometers horizontally (synoptic large scale structuring) and meters to kilometers (small scale structuring that cause scintillations). RF space weather applications affected by electron density variability on these scales include navigation, communication and geo-location of RF frequencies ranging from 100's of Hz to GHz. For many of these applications, the necessary forecast time periods range from nowcasts to 1-3 hours. For more "mission planning" applications, necessary forecast times can range from hours to days. In this paper we present a new ionosphere-thermosphere (IT) specification and forecast model being developed at JHU/APL based upon the well-known data assimilation algorithms Ionospheric Data Assimilation Four Dimensional (IDA4D) and Estimating Model Parameters from Ionospheric Reverse Engineering (EMPIRE). This new forecast model, "Forward Update Simple IONosphere model Plus IDA4D Plus EMPIRE (FUSION++), ingests data from observations related to electron density, winds, electric fields and neutral composition and provides improved specification and forecast of electron density. In addition, the new model provides improved specification of winds, electric fields and composition. We will present a short overview and derivation of the methodology behind FUSION++, some preliminary results using real observational sources, example derived RF application products such as HF bi-static propagation, and initial comparisons with independent data sources for validation.

  14. Sorting carbon nanotubes by electronic structure using density differentiation.

    PubMed

    Arnold, Michael S; Green, Alexander A; Hulvat, James F; Stupp, Samuel I; Hersam, Mark C

    2006-10-01

    The heterogeneity of as-synthesized single-walled carbon nanotubes (SWNTs) precludes their widespread application in electronics, optics and sensing. We report on the sorting of carbon nanotubes by diameter, bandgap and electronic type using structure-discriminating surfactants to engineer subtle differences in their buoyant densities. Using the scalable technique of density-gradient ultracentrifugation, we have isolated narrow distributions of SWNTs in which >97% are within a 0.02-nm-diameter range. Furthermore, using competing mixtures of surfactants, we have produced bulk quantities of SWNTs of predominantly a single electronic type. These materials were used to fabricate thin-film electrical devices of networked SWNTs characterized by either metallic or semiconducting behaviour.

  15. Fast electronic resistance switching involving hidden charge density wave states

    NASA Astrophysics Data System (ADS)

    Vaskivskyi, I.; Mihailovic, I. A.; Brazovskii, S.; Gospodaric, J.; Mertelj, T.; Svetin, D.; Sutar, P.; Mihailovic, D.

    2016-05-01

    The functionality of computer memory elements is currently based on multi-stability, driven either by locally manipulating the density of electrons in transistors or by switching magnetic or ferroelectric order. Another possibility is switching between metallic and insulating phases by the motion of ions, but their speed is limited by slow nucleation and inhomogeneous percolative growth. Here we demonstrate fast resistance switching in a charge density wave system caused by pulsed current injection. As a charge pulse travels through the material, it converts a commensurately ordered polaronic Mott insulating state in 1T-TaS2 to a metastable electronic state with textured domain walls, accompanied with a conversion of polarons to band states, and concurrent rapid switching from an insulator to a metal. The large resistance change, high switching speed (30 ps) and ultralow energy per bit opens the way to new concepts in non-volatile memory devices manipulating all-electronic states.

  16. Fast electronic resistance switching involving hidden charge density wave states

    PubMed Central

    Vaskivskyi, I.; Mihailovic, I. A.; Brazovskii, S.; Gospodaric, J.; Mertelj, T.; Svetin, D.; Sutar, P.; Mihailovic, D.

    2016-01-01

    The functionality of computer memory elements is currently based on multi-stability, driven either by locally manipulating the density of electrons in transistors or by switching magnetic or ferroelectric order. Another possibility is switching between metallic and insulating phases by the motion of ions, but their speed is limited by slow nucleation and inhomogeneous percolative growth. Here we demonstrate fast resistance switching in a charge density wave system caused by pulsed current injection. As a charge pulse travels through the material, it converts a commensurately ordered polaronic Mott insulating state in 1T–TaS2 to a metastable electronic state with textured domain walls, accompanied with a conversion of polarons to band states, and concurrent rapid switching from an insulator to a metal. The large resistance change, high switching speed (30 ps) and ultralow energy per bit opens the way to new concepts in non-volatile memory devices manipulating all-electronic states. PMID:27181483

  17. Collimated fast electron beam generation in critical density plasma

    SciTech Connect

    Iwawaki, T. Habara, H.; Morita, K.; Tanaka, K. A.; Baton, S.; Fuchs, J.; Chen, S.; Nakatsutsumi, M.; Rousseaux, C.; Filippi, F.; Nazarov, W.

    2014-11-15

    Significantly collimated fast electron beam with a divergence angle 10° (FWHM) is observed when an ultra-intense laser pulse (I = 10{sup 14 }W/cm{sup 2}, 300 fs) irradiates a uniform critical density plasma. The uniform plasma is created through the ionization of an ultra-low density (5 mg/c.c.) plastic foam by X-ray burst from the interaction of intense laser (I = 10{sup 14 }W/cm{sup 2}, 600 ps) with a thin Cu foil. 2D Particle-In-Cell (PIC) simulation well reproduces the collimated electron beam with a strong magnetic field in the region of the laser pulse propagation. To understand the physical mechanism of the collimation, we calculate energetic electron motion in the magnetic field obtained from the 2D PIC simulation. As the results, the strong magnetic field (300 MG) collimates electrons with energy over a few MeV. This collimation mechanism may attract attention in many applications such as electron acceleration, electron microscope and fast ignition of laser fusion.

  18. Estimation of dislocation density from precession electron diffraction data using the Nye tensor.

    PubMed

    Leff, A C; Weinberger, C R; Taheri, M L

    2015-06-01

    The Nye tensor offers a means to estimate the geometrically necessary dislocation density of a crystalline sample based on measurements of the orientation changes within individual crystal grains. In this paper, the Nye tensor theory is applied to precession electron diffraction automated crystallographic orientation mapping (PED-ACOM) data acquired using a transmission electron microscope (TEM). The resulting dislocation density values are mapped in order to visualize the dislocation structures present in a quantitative manner. These density maps are compared with other related methods of approximating local strain dependencies in dislocation-based microstructural transitions from orientation data. The effect of acquisition parameters on density measurements is examined. By decreasing the step size and spot size during data acquisition, an increasing fraction of the dislocation content becomes accessible. Finally, the method described herein is applied to the measurement of dislocation emission during in situ annealing of Cu in TEM in order to demonstrate the utility of the technique for characterizing microstructural dynamics.

  19. Predictions of electron temperatures in the Mars ionosphere and their effects on electron densities

    NASA Astrophysics Data System (ADS)

    Withers, Paul; Fallows, Kathryn; Matta, Majd

    2014-04-01

    Observations of peak electron densities in the Mars ionosphere are well fit by a simplistic theory that assumes the electron temperature, Te, at the peak remains constant as solar zenith angle, χ, changes. However, Te ought to vary with both altitude and χ. Here we use an existing numerical model of ionospheric energetics, which includes both vertical and diurnal variations in temperatures, to predict that Te at the ionospheric peak is relatively independent of χ. This model accurately predicts the observed dependence of peak electron density on χ, whereas predictions using Viking-based electron temperatures that are held constant with time do not. A simplified analytic model is developed to interpret these results further. It predicts that the difference between electron and neutral temperatures is proportional to the ratio of electron heating rate to electron production rate and proportional to the square root of solar irradiance.

  20. A technique for routinely updating the ITU-R database using radio occultation electron density profiles

    NASA Astrophysics Data System (ADS)

    Brunini, Claudio; Azpilicueta, Francisco; Nava, Bruno

    2013-09-01

    Well credited and widely used ionospheric models, such as the International Reference Ionosphere or NeQuick, describe the variation of the electron density with height by means of a piecewise profile tied to the F2-peak parameters: the electron density,, and the height, . Accurate values of these parameters are crucial for retrieving reliable electron density estimations from those models. When direct measurements of these parameters are not available, the models compute the parameters using the so-called ITU-R database, which was established in the early 1960s. This paper presents a technique aimed at routinely updating the ITU-R database using radio occultation electron density profiles derived from GPS measurements gathered from low Earth orbit satellites. Before being used, these radio occultation profiles are validated by fitting to them an electron density model. A re-weighted Least Squares algorithm is used for down-weighting unreliable measurements (occasionally, entire profiles) and to retrieve and values—together with their error estimates—from the profiles. These values are used to monthly update the database, which consists of two sets of ITU-R-like coefficients that could easily be implemented in the IRI or NeQuick models. The technique was tested with radio occultation electron density profiles that are delivered to the community by the COSMIC/FORMOSAT-3 mission team. Tests were performed for solstices and equinoxes seasons in high and low-solar activity conditions. The global mean error of the resulting maps—estimated by the Least Squares technique—is between and elec/m for the F2-peak electron density (which is equivalent to 7 % of the value of the estimated parameter) and from 2.0 to 5.6 km for the height (2 %).

  1. Diurnal and seasonal Variability of D-Region Electron Densities at 69°N

    NASA Astrophysics Data System (ADS)

    Singer, Werner; Rapp, Markus; Latteck, Ralph; Friedrich, Martin

    Electron densities of the lower ionosphere are estimated with the Saura MF Doppler radar since summer 2004. The radar is located near country-regioncountry-regionAndenes, countryregionNorway (69.3° N, 16.0° E) and operates at 3.17 MHz with a peak power of 116 kW. The narrow beam transmitting/receiving antenna consists of 29 crossed half-wave dipoles arranged as a Mills Cross resulting in a beam width of about 7° . Antenna and transceiver system provide high flexibility in beam forming as well as the capability forming beams with left and right circular polarization at alternate pulses. The experiment utilizes partial reflections of ordinary and extraordinary component waves from scatterers in the altitude range 50-90 km to estimate electron number densities from differential absorption (DAE) and differential phase (DPE) measurements. Height profiles are obtained between about 55 km and 90 km with a time resolution of 9 minutes and a height resolution of 1 km. The electron density profiles independently derived from DAE and DPE measurements are in remarkable good agreement. Electron number densities are given if the results of the DAE and DPE experiments are in agreement within a factor of two. We discuss the diurnal and seasonal variability of electron densities obtained at Andenes and the response of D-region electron densities to solar activity storms and geomagnetic disturbances. The radar results are compared with previous rocket-borne radio wave propagation measurements at Andenes as well as with recent co-located simultaneous insitu observations using radio wave propagation experiments (differential absorption and Faraday rotation) which showed good agreement between the two techniques. In addition, monthly mean electron densities obtained with the MF radar are compared the recent dedicated auroral-zone, empirical model IMAZ.

  2. Validation of Ionosonde Electron Density Reconstruction Algorithms with IONOLAB-RAY in Central Europe

    NASA Astrophysics Data System (ADS)

    Gok, Gokhan; Mosna, Zbysek; Arikan, Feza; Arikan, Orhan; Erdem, Esra

    2016-07-01

    Ionospheric observation is essentially accomplished by specialized radar systems called ionosondes. The time delay between the transmitted and received signals versus frequency is measured by the ionosondes and the received signals are processed to generate ionogram plots, which show the time delay or reflection height of signals with respect to transmitted frequency. The critical frequencies of ionospheric layers and virtual heights, that provide useful information about ionospheric structurecan be extracted from ionograms . Ionograms also indicate the amount of variability or disturbances in the ionosphere. With special inversion algorithms and tomographical methods, electron density profiles can also be estimated from the ionograms. Although structural pictures of ionosphere in the vertical direction can be observed from ionosonde measurements, some errors may arise due to inaccuracies that arise from signal propagation, modeling, data processing and tomographic reconstruction algorithms. Recently IONOLAB group (www.ionolab.org) developed a new algorithm for effective and accurate extraction of ionospheric parameters and reconstruction of electron density profile from ionograms. The electron density reconstruction algorithm applies advanced optimization techniques to calculate parameters of any existing analytical function which defines electron density with respect to height using ionogram measurement data. The process of reconstructing electron density with respect to height is known as the ionogram scaling or true height analysis. IONOLAB-RAY algorithm is a tool to investigate the propagation path and parameters of HF wave in the ionosphere. The algorithm models the wave propagation using ray representation under geometrical optics approximation. In the algorithm , the structural ionospheric characteristics arerepresented as realistically as possible including anisotropicity, inhomogenity and time dependence in 3-D voxel structure. The algorithm is also used

  3. An x-ray backlit Talbot-Lau deflectometer for high-energy-density electron density diagnostics

    SciTech Connect

    Valdivia, M. P.; Stutman, D.; Stoeckl, C.; Theobald, W.; Mileham, C.; Begishev, I. A.; Bromage, J.; Regan, S. P.

    2016-02-10

    X-ray phase-contrast techniques can measure electron density gradients in high-energy-density plasmas through refraction induced phase shifts. An 8 keV Talbot-Lau interferometer consisting of free standing ultrathin gratings was deployed at an ultra-short, high-intensity laser system using K-shell emission from a 1-30 J, 8 ps laser pulse focused on thin Cu foil targets. Grating survival was demonstrated for 30 J, 8 ps laser pulses. The first x-ray deflectometry images obtained under laser backlighting showed up to 25% image contrast and thus enabled detection of electron areal density gradients with a maximum value of 8.1 ± 0.5 × 1023 cm₋3 in a low-Z millimeter sized sample. An electron density profile was obtained from refraction measurements with an error of <8%. We found the 50 ± 15 μm spatial resolution achieved across the full field of view was limited by the x-ray source-size, similar to conventional radiography.

  4. An x-ray backlit Talbot-Lau deflectometer for high-energy-density electron density diagnostics

    DOE PAGES

    Valdivia, M. P.; Stutman, D.; Stoeckl, C.; ...

    2016-02-10

    X-ray phase-contrast techniques can measure electron density gradients in high-energy-density plasmas through refraction induced phase shifts. An 8 keV Talbot-Lau interferometer consisting of free standing ultrathin gratings was deployed at an ultra-short, high-intensity laser system using K-shell emission from a 1-30 J, 8 ps laser pulse focused on thin Cu foil targets. Grating survival was demonstrated for 30 J, 8 ps laser pulses. The first x-ray deflectometry images obtained under laser backlighting showed up to 25% image contrast and thus enabled detection of electron areal density gradients with a maximum value of 8.1 ± 0.5 × 1023 cm₋3 in amore » low-Z millimeter sized sample. An electron density profile was obtained from refraction measurements with an error of <8%. We found the 50 ± 15 μm spatial resolution achieved across the full field of view was limited by the x-ray source-size, similar to conventional radiography.« less

  5. Nearly degenerate electron distributions and superluminal radiation densities

    NASA Astrophysics Data System (ADS)

    Tomaschitz, Roman

    2010-02-01

    Polylogarithmic fugacity expansions of the partition function, the caloric and thermal equations of state, and the specific heat of fermionic power-law distributions are derived in the nearly degenerate low-temperature/high-density quantum regime. The spectral functions of an ultra-relativistic electron plasma are obtained by averaging the tachyonic radiation densities of inertial electrons with Fermi power-laws, whose entropy is shown to be extensive and stable. The averaged radiation densities are put to test by performing tachyonic cascade fits to the γ-ray spectrum of the TeV blazar Markarian 421 in a low and high emission state. Estimates of the thermal electron plasma in this active galactic nucleus are extracted from the spectral fits, such as temperature, number count, and internal energy. The tachyonic cascades reproduce the quiescent as well as a burst spectrum of the blazar obtained with imaging atmospheric Cherenkov detectors. Double-logarithmic plots of the differential tachyon flux exhibit intrinsic spectral curvature, caused by the Boltzmann factor of the electron gas.

  6. Statistical quality indicators for electron-density maps.

    PubMed

    Tickle, Ian J

    2012-04-01

    The commonly used validation metrics for the local agreement of a structure model with the observed electron density, namely the real-space R (RSR) and the real-space correlation coefficient (RSCC), are reviewed. It is argued that the primary goal of all validation techniques is to verify the accuracy of the model, since precision is an inherent property of the crystal and the data. It is demonstrated that the principal weakness of both of the above metrics is their inability to distinguish the accuracy of the model from its precision. Furthermore, neither of these metrics in their usual implementation indicate the statistical significance of the result. The statistical properties of electron-density maps are reviewed and an improved alternative likelihood-based metric is suggested. This leads naturally to a χ(2) significance test of the difference density using the real-space difference density Z score (RSZD). This is a metric purely of the local model accuracy, as required for effective model validation and structure optimization by practising crystallographers prior to submission of a structure model to the PDB. A new real-space observed density Z score (RSZO) is also proposed; this is a metric purely of the model precision, as a substitute for other precision metrics such as the B factor.

  7. The Electron Density in Explosive Transition Region Events Observed by IRIS

    NASA Astrophysics Data System (ADS)

    Doschek, G. A.; Warren, H. P.; Young, P. R.

    2016-11-01

    We discuss the intensity ratio of the O iv line at 1401.16 Å to the Si iv line at 1402.77 Å in Interface Region Imaging Spectrograph (IRIS) spectra. This intensity ratio is important if it can be used to measure high electron densities that cannot be measured using line intensity ratios of two different O iv lines from the multiplet within the IRIS wavelength range. Our discussion is in terms of considerably earlier observations made from the Skylab manned space station and other spectrometers on orbiting spacecraft. The earlier data on the O iv and Si iv ratio and other intersystem line ratios not available to IRIS are complementary to IRIS data. In this paper, we adopt a simple interpretation based on electron density. We adopt a set of assumptions and calculate the electron density as a function of velocity in the Si iv line profiles of two explosive events. At zero velocity the densities are about 2-3 × 1011 cm-3, and near 200 km s-1 outflow speed the densities are about 1012 cm-3. The densities increase with outflow speed up to about 150 km s-1 after which they level off. Because of the difference in the temperature of formation of the two lines and other possible effects such as non-ionization equilibrium, these density measurements do not have the precision that would be available if there were some additional lines near the formation temperature of O iv.

  8. Excess electrons in ice: a density functional theory study.

    PubMed

    Bhattacharya, Somesh Kr; Inam, Fakharul; Scandolo, Sandro

    2014-02-21

    We present a density functional theory study of the localization of excess electrons in the bulk and on the surface of crystalline and amorphous water ice. We analyze the initial stages of electron solvation in crystalline and amorphous ice. In the case of crystalline ice we find that excess electrons favor surface states over bulk states, even when the latter are localized at defect sites. In contrast, in amorphous ice excess electrons find it equally favorable to localize in bulk and in surface states which we attribute to the preexisting precursor states in the disordered structure. In all cases excess electrons are found to occupy the vacuum regions of the molecular network. The electron localization in the bulk of amorphous ice is assisted by its distorted hydrogen bonding network as opposed to the crystalline phase. Although qualitative, our results provide a simple interpretation of the large differences observed in the dynamics and localization of excess electrons in crystalline and amorphous ice films on metals.

  9. Electron inelastic mean free path theory and density functional theory resolving discrepancies for low-energy electrons in copper.

    PubMed

    Chantler, C T; Bourke, J D

    2014-02-06

    We develop the many-pole dielectric theory of UV plasmon interactions and electron energy losses, and couple our advances with recent developments of Kohn-Sham density functional theory to address observed discrepancies between high-precision measurements and tabulated data for electron inelastic mean free paths (IMFPs). Recent publications have demonstrated that a five standard error difference exists between longstanding theoretical calculations and measurements of electron IMFPs for elemental solids at energies below 120 eV, a critical region for analysis of electron energy loss spectroscopy (EELS), X-ray absorption spectroscopy (XAS), and related technologies. Our implementation of improved optical loss spectra and a physical treatment of second-order excitation lifetimes resolves this problem in copper for the first time for energies in excess of 80 eV and substantially improves agreement for lower energy electrons.

  10. Excitations and benchmark ensemble density functional theory for two electrons

    SciTech Connect

    Pribram-Jones, Aurora; Burke, Kieron; Yang, Zeng-hui; Ullrich, Carsten A.; Trail, John R.; Needs, Richard J.

    2014-05-14

    A new method for extracting ensemble Kohn-Sham potentials from accurate excited state densities is applied to a variety of two-electron systems, exploring the behavior of exact ensemble density functional theory. The issue of separating the Hartree energy and the choice of degenerate eigenstates is explored. A new approximation, spin eigenstate Hartree-exchange, is derived. Exact conditions that are proven include the signs of the correlation energy components and the asymptotic behavior of the potential for small weights of the excited states. Many energy components are given as a function of the weights for two electrons in a one-dimensional flat box, in a box with a large barrier to create charge transfer excitations, in a three-dimensional harmonic well (Hooke's atom), and for the He atom singlet-triplet ensemble, singlet-triplet-singlet ensemble, and triplet bi-ensemble.

  11. Temporal evolution of electron density and temperature in capillary discharge plasmas

    NASA Astrophysics Data System (ADS)

    Oh, Seong Y.; Uhm, Han S.; Kang, Hoonsoo; Lee, In W.; Suk, Hyyong

    2010-05-01

    Time-resolved spectroscopic measurements of a capillary discharge plasma of helium gas were carried out to obtain detailed information about dynamics of the discharge plasma column, where the fast plasma dynamics is determined by the electron density and temperature. Our measurements show that the electron density of the capillary plasma column increases sharply after gas breakdown and reaches its peak of the order of 1018 cm-3 within less than 100 ns, and then it decreases as time goes by. The result indicates that a peak electron density of 2.3×1018 cm-3 occurs about 65 ns after formation of the discharge current, which is ideal for laser wakefield acceleration experiments reported by Karsch et al. [New J. Phys. 9, 415 (2007)].

  12. New Data on the Topside Electron Density Distribution

    NASA Technical Reports Server (NTRS)

    Huang, Xue-Qin; Reinisch, Bodo; Bilitza, Dieter; Benson, Robert F.

    2001-01-01

    The existing uncertainties about the electron density profiles in the topside ionosphere, i.e., in the height region from hmF2 to approx. 2000 km, require the search for new data sources. The ISIS and Alouette topside sounder satellites from the sixties to the eighties recorded millions of ionograms and most were not analyzed in terms of electron density profiles. In recent years an effort started to digitize the analog recordings to prepare the ionograms for computerized analysis. As of November 2001 about 350,000 ionograms have been digitized from the original 7-track analog tapes. These data are available in binary and CDF format from the anonymous ftp site of the National Space Science Data Center. A search site and browse capabilities on CDAWeb assist the scientific usage of these data. All information and access links can be found at http://nssdc.gsfc.nasa.gov/space/isis/isis-status.html. This paper describes the ISIS data restoration effort and shows how the digital ionograms are automatically processed into electron density profiles from satellite orbit altitude (1400 km for ISIS-2) down to the F peak. Because of the large volume of data an automated processing algorithm is imperative. The automatic topside ionogram scaler with true height algorithm TOPIST software developed for this task is successfully scaling approx.70 % of the ionograms. An 'editing process' is available to manually scale the more difficult ionograms. The automated processing of the digitized ISIS ionograms is now underway, producing a much-needed database of topside electron density profiles for ionospheric modeling covering more than one solar cycle. The ISIS data restoration efforts are supported through NASA's Applied Systems and Information Research Program.

  13. Surprising resistivity decrease in manganites with constant electronic density

    NASA Astrophysics Data System (ADS)

    Cortés-Gil, R.; Ruiz-González, M. L.; Alonso, J. M.; Martínez, J. L.; Hernando, A.; Vallet-Regí, M.; González-Calbet, J. M.

    2013-12-01

    A decrease of eight orders of magnitude in the resistance of (La0.5Ca0.5)zMnO3 has been detected when the electronic density is kept constant while the calcium content is modified by introducing cationic vacancies. This effect is related to the disappearance of the charge ordering state and the emergence of an antiferromagnetic-ferromagnetic transition. Moreover, high values of the colossal magnetoresistance above room temperature are attained. Dedicated to Professor J M Rojo.

  14. Halogen bonding: a study based on the electronic charge density.

    PubMed

    Amezaga, Nancy J Martinez; Pamies, Silvana C; Peruchena, Nélida M; Sosa, Gladis L

    2010-01-14

    Density functional theory (DFT) and atoms in molecules theory (AIM) were used to study the characteristic of the noncovalent interactions in complexes formed between Lewis bases (NH(3), H(2)O, and H(2)S) and Lewis acids (ClF, BrF, IF, BrCl, ICl, and IBr). In order to compare halogen and hydrogen bonds interactions, this study included hydrogen complexes formed by some Lewis bases and HF, HCl, and HBr Lewis acids. Ab initio, wave functions were generated at B3LYP/6-311++G(d,p) level with optimized structures at the same level. Criteria based on a topological analysis of the electron density were used in order to characterize the nature of halogen interactions in Lewis complexes. The main purpose of the present work is to provide an answer to the following questions: (a) why can electronegative atoms such as halogens act as bridges between two other electronegative atoms? Can a study based on the electron charge density answer this question? Considering this, we had performed a profound study of halogen complexes in the framework of the AIM theory. A good correlation between the density at the intermolecular bond critical point and the energy interaction was found. We had also explored the concentration and depletion of the charge density, displayed by the Laplacian topology, in the interaction zone and in the X-Y halogen donor bond. From the atomic properties, it was generally observed that the two halogen atoms gain electron population in response to its own intrinsic nature. Because of this fact, both atoms are energetically stabilized.

  15. determination of current density distribution in an electron beam

    NASA Astrophysics Data System (ADS)

    Kandel, Yudhishthir Prasad

    Electron beams are useful in many applications because they can be focused down to a spot far exceeding the physical limit of focusing visible light or x-rays. Additionally, electron beams are useful in transferring concentrated amounts of energy to a very small well defined region of a target for a fixed duration. This has led to the development of both scanning electron microscopes (SEMs) and electron beam lithography. The goal of this work was to develop a general method that accurately and easily yields the best estimate of the electron current density distribution of a focused electron beam, known as point spread function (PSF). The method developed is fast, easy to use and accurate. Two specific areas of research have been addressed for PSF determination. The first is concerned with the monotonic response of EUV photoresist as a function of electron beam dose. An external metrology is used for mapping the change in thickness that is smaller than the beam spot size. The method developed in this study simultaneously gives the photo-resist thickness change as a function of electron dose and electron beam PSF. A second thrust of this research has been to develop set of PSF characterization approaches that apply to the SEM. Here a knowledge of the PSF offers many benefits including the ability to monitor and optimize SEM performance such as astigmatism control. Perhaps, even more importantly, a knowledge of the PSF combined with a series of well-defined experimental steps has led to the development of new methods for improving the resolution of SEM images through computational means rather than very costly and complex equipment modification.

  16. Kinetic and electron-electron energies for convex sums of ground state densities with degeneracies and fractional electron number

    SciTech Connect

    Levy, Mel E-mail: mlevy@tulane.edu; Anderson, James S. M.; Zadeh, Farnaz Heidar; Ayers, Paul W. E-mail: mlevy@tulane.edu

    2014-05-14

    Properties of exact density functionals provide useful constraints for the development of new approximate functionals. This paper focuses on convex sums of ground-level densities. It is observed that the electronic kinetic energy of a convex sum of degenerate ground-level densities is equal to the convex sum of the kinetic energies of the individual degenerate densities. (The same type of relationship holds also for the electron-electron repulsion energy.) This extends a known property of the Levy-Valone Ensemble Constrained-Search and the Lieb Legendre-Transform refomulations of the Hohenberg-Kohn functional to the individual components of the functional. Moreover, we observe that the kinetic and electron-repulsion results also apply to densities with fractional electron number (even if there are no degeneracies), and we close with an analogous point-wise property involving the external potential. Examples where different degenerate states have different kinetic energy and electron-nuclear attraction energy are given; consequently, individual components of the ground state electronic energy can change abruptly when the molecular geometry changes. These discontinuities are predicted to be ubiquitous at conical intersections, complicating the development of universally applicable density-functional approximations.

  17. A real-space stochastic density matrix approach for density functional electronic structure.

    PubMed

    Beck, Thomas L

    2015-12-21

    The recent development of real-space grid methods has led to more efficient, accurate, and adaptable approaches for large-scale electrostatics and density functional electronic structure modeling. With the incorporation of multiscale techniques, linear-scaling real-space solvers are possible for density functional problems if localized orbitals are used to represent the Kohn-Sham energy functional. These methods still suffer from high computational and storage overheads, however, due to extensive matrix operations related to the underlying wave function grid representation. In this paper, an alternative stochastic method is outlined that aims to solve directly for the one-electron density matrix in real space. In order to illustrate aspects of the method, model calculations are performed for simple one-dimensional problems that display some features of the more general problem, such as spatial nodes in the density matrix. This orbital-free approach may prove helpful considering a future involving increasingly parallel computing architectures. Its primary advantage is the near-locality of the random walks, allowing for simultaneous updates of the density matrix in different regions of space partitioned across the processors. In addition, it allows for testing and enforcement of the particle number and idempotency constraints through stabilization of a Feynman-Kac functional integral as opposed to the extensive matrix operations in traditional approaches.

  18. Electron intracule densities with correct electron coalescence cusps from Hiller-Sucher-Feinberg-type identities

    NASA Astrophysics Data System (ADS)

    Cioslowski, Jerzy; Stefanov, Boris B.; Tan, Agnes; Umrigar, C. J.

    1995-10-01

    Identities for the electron intracule density I(R) in atoms and molecules are derived within the Hiller-Sucher-Feinberg (HSF) formalism. It is proven that, when applied to arbitrary (exact or approximate) electronic wave functions, these identities produce intracule densities that satisfy a modified condition for the electron coalescence cusp. A corollary of this proof provides a new, simplified derivation of the cusp condition for the exact I(R). An expression for the Hartree-Fock approximation to the HSF electron intracule density that contains only two- and three-electron terms is obtained and its properties are analyzed. A simple scaling of the three-electron contributions in this expression assures integrability of the approximate I(R) and improves its overall accuracy. Numerical tests carried out for the H-, He, Li+, Be2+, Li, and Be systems demonstrate that the application of the scaled HSF-type identity to Hartree-Fock wave functions affords dramatic improvements in the short-range behavior of the electron intracule density.

  19. Unfolding ambient electron plasma density from wave spectra induced by electron beam

    NASA Astrophysics Data System (ADS)

    Kiraga, A.; Klos, Z.; Oraevsky, V.; Dokukin, V.; Pulinets, S.

    Numerous rocket and few satellite projects were devoted to study of astrophysical plasma with the aid of active electron beam experiments. The quality and volume of wave data from such experiments did not fulfill original expectat ions due to complexity of involved processes, technical malfunctions and limited diagnostics. Due to fortunate, temporal malfunction of plasma accelerator, there were several cases when pulsed electron beam had been injected from the APEX satellite into otherwise unmodified ionospheric plasma. Instantaneous current intensity didn't exceeded 0.15A and an unstabilized acceleration voltage was of the order of 10keV. Injection pitch angle slowly changed according to moderate three-axis satellite stabilization. Injections took place in the altitude range 400-1100km in the European region and in the north, polar region. A receiver with bandwidth of 15kHz was connected to a cylindrical dipole antenna having half lengths of 7.5m. The receiver operated in survey mode providing one spectrum every 2s or 8s. The single spectrum was measured in 1s with an equally spaced mesh of 200 frequencies starting from 100kHz with a step of 50kHz. Electron beam induced spectra show up large variety of narrow band structures. In many cases, from reproducibility or slow evolution of the spectra, it may be inferred that distinct interactions prevail for some ranges of ambient electron gyro (fc) and plasma (fn) frequencies, injection pitch angles and beam intensity. Interaction plausibility arguments are useful in preliminary assignment of spectral structures. We show that discrete emission can be identified at least on ambient plasma frequency or ambient upper hybrid frequency. One class of arguments supporting such identification is provided by interrelation between spectral signatures of local plasma density in passive mode and beam induced spectra. Another class of arguments is provided by interrelations between spectral structures induced by electron beam

  20. Electronic density of states in sequence dependent DNA molecules

    NASA Astrophysics Data System (ADS)

    de Oliveira, B. P. W.; Albuquerque, E. L.; Vasconcelos, M. S.

    2006-09-01

    We report in this work a numerical study of the electronic density of states (DOS) in π-stacked arrays of DNA single-strand segments made up from the nucleotides guanine G, adenine A, cytosine C and thymine T, forming a Rudin-Shapiro (RS) as well as a Fibonacci (FB) polyGC quasiperiodic sequences. Both structures are constructed starting from a G nucleotide as seed and following their respective inflation rules. Our theoretical method uses Dyson's equation together with a transfer-matrix treatment, within an electronic tight-binding Hamiltonian model, suitable to describe the DNA segments modelled by the quasiperiodic chains. We compared the DOS spectra found for the quasiperiodic structure to those using a sequence of natural DNA, as part of the human chromosome Ch22, with a remarkable concordance, as far as the RS structure is concerned. The electronic spectrum shows several peaks, corresponding to localized states, as well as a striking self-similar aspect.

  1. Feedback control of plasma electron density and ion energy in an inductively coupled plasma etcher

    SciTech Connect

    Lin Chaung; Leou, K.-C.; Huang, H.-M.; Hsieh, C.-H.

    2009-01-15

    Here the authors report the development of a fuzzy logic based feedback control of the plasma electron density and ion energy for high density plasma etch process. The plasma electron density was measured using their recently developed transmission line microstrip microwave interferometer mounted on the chamber wall, and the rf voltage was measured by a commercial impedance meter connected to the wafer stage. The actuators were two 13.56 MHz rf power generators which provided the inductively coupled plasma power and bias power, respectively. The control system adopted the fuzzy logic control algorithm to reduce frequent actuator action resulting from measurement noise. The experimental results show that the first wafer effect can be eliminated using closed-loop control for both poly-Si and HfO{sub 2} etching. In particular, for the HfO2 etch, the controlled variables in this work were much more effective than the previous one where ion current was controlled, instead of the electron density. However, the pressure disturbance effect cannot be reduced using plasma electron density feedback.

  2. A density-temperature description of the outer electron radiation belt during geomagnetic storms

    SciTech Connect

    Borovsky, Joseph E; Cayton, Thomas E; Denton, Michael H

    2009-01-01

    Electron flux measurements from 7 satellites in geosynchronous orbit from 1990-2007 are fit with relativistic bi-Maxwellians, yielding a number density n and temperature T description of the outer electron radiation belt. For 54.5 spacecraft years of measurements the median value ofn is 3.7x10-4 cm-3 and the median value ofT is 142 keY. General statistical properties of n, T, and the 1.1-1.5 MeV flux J are investigated, including local-time and solar-cycle dependencies. Using superposed-epoch analysis triggered on storm onset, the evolution of the outer electron radiation belt through high-speed-steam-driven storms is investigated. The number density decay during the calm before the storm is seen, relativistic-electron dropouts and recoveries from dropout are investigated, and the heating of the outer electron radiation belt during storms is examined. Using four different triggers (SSCs, southward-IMF CME sheaths, southward-IMF magnetic clouds, and minimum Dst), CME-driven storms are analyzed with superposed-epoch techniques. For CME-driven storms an absence of a density decay prior to storm onset is found, the compression of the outer electron radiation belt at time of SSC is analyzed, the number-density increase and temperature decrease during storm main phase is seen, and the increase in density and temperature during storm recovery phase is observed. Differences are found between the density-temperature and the flux descriptions, with more information for analysis being available in the density-temperature description.

  3. Equation satisfied by the energy-density functional for electron-electron mutual Coulomb repulsion

    SciTech Connect

    Joubert, Daniel P.

    2011-10-15

    It is shown that the electron-electron mutual Coulomb repulsion energy-density functional V{sub ee}{sup {gamma}}[{rho}] satisfies the equationV{sub ee}{sup {gamma}}[{rho}{sub N}{sup 1}]-V{sub ee}{sup {gamma}}[{rho}{sub N-1}{sup {gamma}}]={integral}d{sup 3}r({delta}V{sub ee}{sup {gamma}}[{rho}{sub N}{sup 1}]/{delta}{rho}{sub N}{sup 1}(r))[{rho}{sub N}{sup 1}(r)-{rho}{sub N-1}{sup {gamma}}(r)], where {rho}{sub N}{sup 1}(r) and {rho}{sub N-1}{sup {gamma}}(r) are N-electron and (N-1)-electron densities determined from the same adiabatic scaled external potential of the N-electron system at coupling strength {gamma}.

  4. Exploring the electron density in plasma induced by EUV radiation: II. Numerical studies in argon and hydrogen

    NASA Astrophysics Data System (ADS)

    Astakhov, D. I.; Goedheer, W. J.; Lee, C. J.; Ivanov, V. V.; Krivtsun, V. M.; Koshelev, K. N.; Lopaev, D. V.; van der Horst, R. M.; Beckers, J.; Osorio, E. A.; Bijkerk, F.

    2016-07-01

    We used numerical modeling to study the evolution of EUV-induced plasmas in argon and hydrogen. The results of simulations were compared to the electron densities measured by microwave cavity resonance spectroscopy. It was found that the measured electron densities can be used to derive the integral amount of plasma in the cavity. However, in some regimes, the impact of the setup geometry, EUV spectrum, and EUV induced secondary emission should be taken into account. The influence of these parameters on the generated plasma and the measured electron density is discussed.

  5. Electronic correlations in vanadium revealed by electron-positron annihilation measurements

    NASA Astrophysics Data System (ADS)

    Weber, Josef Andreas; Benea, Diana; Appelt, Wilhelm H.; Ceeh, Hubert; Kreuzpaintner, Wolfgang; Leitner, Michael; Vollhardt, Dieter; Hugenschmidt, Christoph; Chioncel, Liviu

    2017-02-01

    The electronic structure of vanadium measured by angular correlation of electron-positron annihilation radiation (ACAR) is compared with the predictions of the combined density functional and dynamical mean-field theory (DMFT). Reconstructing the momentum density from five two-dimensional projections we were able to determine the full Fermi surface and found excellent agreement with the DMFT calculations. In particular, we show that the local, dynamic self-energy corrections contribute to the anisotropy of the momentum density and need to be included to explain the experimental results.

  6. Damping of Electron Density Structures and Implications for Interstellar Scintillation

    NASA Astrophysics Data System (ADS)

    Smith, K. W.; Terry, P. W.

    2011-04-01

    The forms of electron density structures in kinetic Alfvén wave (KAW) turbulence are studied in connection with scintillation. The focus is on small scales L ~ 108-1010 cm where the KAW regime is active in the interstellar medium, principally within turbulent H II regions. Scales at 10 times the ion gyroradius and smaller are inferred to dominate scintillation in the theory of Boldyrev et al. From numerical solutions of a decaying KAW turbulence model, structure morphology reveals two types of localized structures, filaments and sheets, and shows that they arise in different regimes of resistive and diffusive damping. Minimal resistive damping yields localized current filaments that form out of Gaussian-distributed initial conditions. When resistive damping is large relative to diffusive damping, sheet-like structures form. In the filamentary regime, each filament is associated with a non-localized magnetic and density structure, circularly symmetric in cross section. Density and magnetic fields have Gaussian statistics (as inferred from Gaussian-valued kurtosis) while density gradients are strongly non-Gaussian, more so than current. This enhancement of non-Gaussian statistics in a derivative field is expected since gradient operations enhance small-scale fluctuations. The enhancement of density gradient kurtosis over current kurtosis is not obvious, yet it suggests that modest density fluctuations may yield large scintillation events during pulsar signal propagation. In the sheet regime the same statistical observations hold, despite the absence of localized filamentary structures. Probability density functions are constructed from statistical ensembles in both regimes, showing clear formation of long, highly non-Gaussian tails.

  7. Performance of a local electron density trigger to select extensive air showers at sea level

    NASA Technical Reports Server (NTRS)

    Abbas, T.; Madani, J.; Ashton, F.

    1985-01-01

    Time coincident voltage pulses in the two closely space (1.6m) plastic scintillators were recorded. Most of the recorded events are expeted to be due to electrons in cosmic ray showers whose core fall at some distance from the detectors. This result is confirmed from a measurement of the frequency distribution of the recorded density ratios of the two scintillators.

  8. Measurements of recombination of electrons with HCO(plus) ions

    NASA Technical Reports Server (NTRS)

    Leu, M. T.; Biondi, M. A.; Johnsen, R.

    1973-01-01

    Recombination coefficients of electrons with HCO(+) ions were determined with a microwave afterglow/mass spectrometer apparatus. Afterglow measurements of electron density decays in neon-hydrogen-carbon monoxide mixtures are correlated with the decay of mass-identified ion currents to the wall of the microwave cavity. At the appropriate partial pressures of hydrogen and carbon monoxide in the mixture, the ion HCO(+) dominates the ion composition and its wall current approximately tracks the electron density decay curve. From recombination controlled electron density decay curves, the values alpha (HCO(+)) = (3.3 + or - 0.5) and (2.0 + or - 0.3) 0.0000001 cu cm/sec are obtained at 205 and 300 K, respectively. The implications of these results for models of polyatomic molecule formation in dense interstellar clouds are briefly discussed.

  9. Density Measurement of Compact Toroid with Mach-Zehnder Interferometer

    NASA Astrophysics Data System (ADS)

    Laufman-Wollitzer, Lauren; Endrizzi, Doug; Brookhart, Matt; Flanagan, Ken; Forest, Cary

    2016-10-01

    Utilizing a magnetized coaxial plasma gun (MCPG) built by Tri Alpha Energy, a dense compact toroid (CT) is created and injected at high speed into the Wisconsin Plasma Astrophysics Laboratory (WiPAL) vessel. A modified Mach-Zehnder interferometer from the Line-Tied Reconnection Experiment (LTRX) provides an absolute measurement of electron density. The interferometer is located such that the beam intersects the plasma across the diameter of the MCPG drift region before the CT enters the vessel. This placement ensures that the measurement is taken before the CT expand. Results presented will be used to further analyze characteristics of the CT. Funding provided by DoE, NSF, and WISE Summer Research.

  10. Role of Density Gradient Driven Trapped Electron Modes in the H-Mode Inner Core with Electron Heating

    NASA Astrophysics Data System (ADS)

    Ernst, D.

    2015-11-01

    We present new experiments and nonlinear gyrokinetic simulations showing that density gradient driven TEM (DGTEM) turbulence dominates the inner core of H-Mode plasmas during strong electron heating. Thus α-heating may degrade inner core confinement in H-Mode plasmas with moderate density peaking. These DIII-D low torque quiescent H-mode experiments were designed to study DGTEM turbulence. Gyrokinetic simulations using GYRO (and GENE) closely match not only particle, energy, and momentum fluxes, but also density fluctuation spectra, with and without ECH. Adding 3.4 MW ECH doubles Te /Ti from 0.5 to 1.0, which halves the linear TEM critical density gradient, locally flattening the density profile. Density fluctuations from Doppler backscattering (DBS) intensify near ρ = 0.3 during ECH, displaying a band of coherent fluctuations with adjacent toroidal mode numbers. GYRO closely reproduces the DBS spectrum and its change in shape and intensity with ECH, identifying these as coherent TEMs. Prior to ECH, parallel flow shear lowers the effective nonlinear DGTEM critical density gradient 50%, but is negligible during ECH, when transport displays extreme stiffness in the density gradient. GS2 predictions show the DGTEM can be suppressed, to avoid degradation with electron heating, by broadening the current density profile to attain q0 >qmin > 1 . A related experiment in the same regime varied the electron temperature gradient in the outer half-radius (ρ ~ 0 . 65) using ECH, revealing spatially coherent 2D mode structures in the Te fluctuations measured by ECE imaging. Fourier analysis with modulated ECH finds a threshold in Te profile stiffness. Supported by the US DOE under DE-FC02-08ER54966 and DE-FC02-04ER54698.

  11. Interpretation of the shape factor at Ootacamund, India. [ionospheric electron density profile

    NASA Technical Reports Server (NTRS)

    Donnelly, R. F.; Anderson, D. N.; Davies, K.; Rama Rao, P. V. S.

    1978-01-01

    The paper deals with equatorial ATS-6 measurements of the shape factor, F, interpreted in terms of the shape of the electron density profile along the ray path. The observed rapid increase in F at sunrise is attributed to EUV production of ionization in the E and F regions. The evening decrease is seen to result from an upward drift of the F region at sunset and the evening decay of the E and bottomside F regions. The nighttime peak, or plateau, is caused by gradual decrease of the electron density profile.

  12. A model of F2 peak electron densities in the main trough region of the ionosphere

    NASA Technical Reports Server (NTRS)

    Halcrow, B. W.; Nisbet, J. S.

    1977-01-01

    An empirical model of the peak electron densities in the region of the northerly main trough in the ionospheric F region is presented. The model was derived from measurements made by the satellites Alouette I and II and is in the form of a multiplicative modification factor to the CCIR peak electron density model. The model is a computer program which, when provided with the location, universal time, day number, sunspot number, and Kp index, provides the modification factor, the CCIR model prediction of Nm F2, and the new prediction including the effect of the trough. The model is expected to be of considerable use for propagation calculations in the affected region.

  13. Calculation of optical and electronic properties of modeled titanium dioxide films of different densities.

    PubMed

    Turowski, Marcus; Amotchkina, Tatiana; Ehlers, Henrik; Jupé, Marco; Ristau, Detlev

    2014-02-01

    The electronic and optical properties of TiO2 atomic structures representing simulated thin films have been investigated using density functional theory. Suitable model parameters and system sizes have been identified in advance by validation of the results with experimental data. Dependencies of the electronic band gap and the refractive index have been calculated as a function of film density. The results of the performed calculations have been compared to characterized optical properties of titania single layers deposited using different coating techniques. The modeled dependencies are consistent with experimental observations, and absolute magnitudes of simulated values are in agreement with measured optical data.

  14. Statistical studies of electron density around lunar wake boundary derived from WFC observation onboard KAGUYA

    NASA Astrophysics Data System (ADS)

    Kasahara, Y.; Kanatani, K.; Goto, Y.; Hashimoto, K.; Omura, Y.; Kumamoto, A.; Ono, T.; Nishino, M. N.; Saito, Y.; Tsunakawa, H.

    2011-12-01

    The waveform capture (WFC) [1,2] onboard KAGUYA measured two components of electric wave signals detected by the two orthogonal 30 m tip-to-tip antennas from 100Hz to 1MHz during the mission period of KAGUYA from November, 2007 to June 2009. By taking advantage of a moon orbiter, the WFC was expected to measure plasma waves related to solar wind-moon interaction, mini-magnetospheres caused by magnetic anomaly on the lunar surface, and radio emissions to be observed from the moon. Because the moon is basically non-magnetized, the solar wind particles directly hit the lunar surface and a plasma cavity called the "lunar wake" is created behind the moon. We investigated electron density profile around the terminator of the moon from the local plasma frequency obtained by WFC. Because our measurement is a direct method measuring the local plasma frequency, we expect absolute density can be derived. KAGUYA experienced encounters with the lunar wake every 2 hours at an altitude of ~100km in the nominal mission, we first analyzed electron density statistically when KAGUYA was located in the solar wind comparing with the data from WIND. Using these observation data, we constructed an electron density model around the lunar wake boundary region. We also report several interesting feature in the profile such as asymmetric structure depending on the direction of interplanetary magnetic field (IMF). KAGUYA was descended to the 50 km altitude and was descended again down to 10-30km in lower altitude (perilune). Electron density in the lower altitude region is also studied using the data obtained in the extended mission. We found electron density slightly increases in the lower altitude region. [1] Y. Kasahara et al., Earth, Planets and Space, 60, 341-351, 2008. [2] T. Ono et al., Space Science Review, doi:10.1007/s11214-010-9673-8, 2010.

  15. Electron densities and alkali atoms in exoplanet atmospheres

    SciTech Connect

    Lavvas, P.; Koskinen, T.; Yelle, R. V.

    2014-11-20

    We describe a detailed study on the properties of alkali atoms in extrasolar giant planets, and specifically focus on their role in generating the atmospheric free electron densities, as well as their impact on the transit depth observations. We focus our study on the case of HD 209458b, and we show that photoionization produces a large electron density in the middle atmosphere that is about two orders of magnitude larger than the density anticipated from thermal ionization. Our purely photochemical calculations, though, result in a much larger transit depth for K than observed for this planet. This result does not change even if the roles of molecular chemistry and excited state chemistry are considered for the alkali atoms. In contrast, the model results for the case of exoplanet XO-2b are in good agreement with the available observations. Given these results we discuss other possible scenarios, such as changes in the elemental abundances, changes in the temperature profiles, and the possible presence of clouds, which could potentially explain the observed HD 209458b alkali properties. We find that most of these scenarios cannot explain the observations, with the exception of a heterogeneous source (i.e., clouds or aerosols) under specific conditions, but we also note the discrepancies among the available observations.

  16. FINDMOL: automated identification of macromolecules in electron-density maps.

    PubMed

    McKee, E W; Kanbi, L D; Childs, K L; Grosse-Kunstleve, R W; Adams, P D; Sacchettini, J C; Ioerger, T R

    2005-11-01

    Automating the determination of novel macromolecular structures via X-ray crystallographic methods involves building a model into an electron-density map. Unfortunately, the conventional crystallographic asymmetric unit volumes are usually not well matched to the biological molecular units. In most cases, the facets of the asymmetric unit cut the molecules into a number of disconnected fragments, rendering interpretation by the crystallographer significantly more difficult. The FINDMOL algorithm is designed to quickly parse the arrangement of trace points (pseudo-atoms) derived from a skeletonized electron-density map without requiring higher level prior information such as sequence information or number of molecules in the asymmetric unit. The algorithm was tested with a variety of density-modified maps computed with medium- to low-resolution data. Typically, the resulting volume resembles the biological unit. In the remaining cases the number of disconnected fragments is very small. In all examples, secondary-structural elements such as alpha-helices or beta-sheets are easily identifiable in the defragmented arrangement. FINDMOL can greatly assist a crystallographer during manual model building or in cases where automatic model building can only build partial models owing to limitations of the data such as low resolution and/or poor phases.

  17. Analysis of line integrated electron density using plasma position data on Korea Superconducting Tokamak Advanced Researcha)

    NASA Astrophysics Data System (ADS)

    Nam, Y. U.; Chung, J.

    2010-10-01

    A 280 GHz single-channel horizontal millimeter-wave interferometer system has been installed for plasma electron density measurements on the Korea Superconducting Tokamak Advanced Research (KSTAR) device. This system has a triangular beam path that does not pass through the plasma axis due to geometrical constraints in the superconducting tokamak. The term line density on KSTAR has a different meaning from the line density of other tokamaks. To estimate the peak density and the mean density from the measured line density, information on the position of the plasma is needed. The information has been calculated from tangentially viewed visible images using the toroidal symmetry of the plasma. Interface definition language routines have been developed for this purpose. The calculated plasma position data correspond well to calculation results from magnetic analysis. With the position data and an estimated plasma profile, the peak density and the mean density have been obtained from the line density. From these results, changes of plasma density themselves can be separated from effects of the plasma movements, so they can give valuable information on the plasma status.

  18. 46 CFR 164.009-17 - Density measurement.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... 46 Shipping 6 2011-10-01 2011-10-01 false Density measurement. 164.009-17 Section 164.009-17... measurement. (a) The measurements described in this section are made to determine the density of a sample. (b... the specimen. The average of at least four measurements of each dimension is determined. (c) If...

  19. 46 CFR 164.009-17 - Density measurement.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... 46 Shipping 6 2010-10-01 2010-10-01 false Density measurement. 164.009-17 Section 164.009-17... measurement. (a) The measurements described in this section are made to determine the density of a sample. (b... the specimen. The average of at least four measurements of each dimension is determined. (c) If...

  20. 46 CFR 164.009-17 - Density measurement.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ... 46 Shipping 6 2014-10-01 2014-10-01 false Density measurement. 164.009-17 Section 164.009-17... measurement. (a) The measurements described in this section are made to determine the density of a sample. (b... the specimen. The average of at least four measurements of each dimension is determined. (c) If...

  1. 46 CFR 164.009-17 - Density measurement.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ... 46 Shipping 6 2013-10-01 2013-10-01 false Density measurement. 164.009-17 Section 164.009-17... measurement. (a) The measurements described in this section are made to determine the density of a sample. (b... the specimen. The average of at least four measurements of each dimension is determined. (c) If...

  2. 46 CFR 164.009-17 - Density measurement.

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ... 46 Shipping 6 2012-10-01 2012-10-01 false Density measurement. 164.009-17 Section 164.009-17... measurement. (a) The measurements described in this section are made to determine the density of a sample. (b... the specimen. The average of at least four measurements of each dimension is determined. (c) If...

  3. The electron localization as the information content of the conditional pair density

    NASA Astrophysics Data System (ADS)

    Urbina, Andres S.; Torres, F. Javier; Rincon, Luis

    2016-06-01

    In the present work, the information gained by an electron for "knowing" about the position of another electron with the same spin is calculated using the Kullback-Leibler divergence (DKL) between the same-spin conditional pair probability density and the marginal probability. DKL is proposed as an electron localization measurement, based on the observation that regions of the space with high information gain can be associated with strong correlated localized electrons. Taking into consideration the scaling of DKL with the number of σ-spin electrons of a system (Nσ), the quantity χ = (Nσ - 1) DKLfcut is introduced as a general descriptor that allows the quantification of the electron localization in the space. fcut is defined such that it goes smoothly to zero for negligible densities. χ is computed for a selection of atomic and molecular systems in order to test its capability to determine the region in space where electrons are localized. As a general conclusion, χ is able to explain the electron structure of molecules on the basis of chemical grounds with a high degree of success and to produce a clear differentiation of the localization of electrons that can be traced to the fluctuation in the average number of electrons in these regions.

  4. [Research on electron density in DC needle-plate corona discharge at atmospheric pressure].

    PubMed

    Liu, Zhi-Qiang; Guo, Wei; Liu, Tao-Tao; Wu, Wen-Shuo; Liu, Shu-Min

    2013-11-01

    Using needle-plate discharge device, corona discharge experiment was done in the atmosphere. Through photo of spot size of light-emitting area, the relationship between the voltage and thickness of corona layer was discussed. When the distance between tip and plate is fixed, the thickness of corona layer increases with the increase in voltage; when the voltage is fixed, the thickness of corona layer decreases with the increase in the distance between tip and plate. As spectral intensity of N2 (C3pi(u)) (337.1 nm)reflects high energy electron density, it was measured with emission spectrometry. The results show that high energy electron density is the biggest near the needle tip and the relationship between high energy electron density and voltage is basically linear increasing. Fixing voltage, high energy electron density decreases with the increase in the distance between tip and plate. When the voltage and the distance between tip and plate are fixed, the high energy electron density increases with the decrease in the curvature radius of needle tip. These results are of great importance for the study of plasma parameters of corona discharge.

  5. The behavior of electron density and temperature during ionospheric heating near the fifth electron gyrofrequency

    NASA Astrophysics Data System (ADS)

    Wu, Jun; Wu, Jian; Rietveld, M. T.; Haggstrom, I.; Zhao, Haisheng; Xu, Zhengwen

    2017-01-01

    The experimental phenomena involving the changes in electron temperature and electron density as a function of pump frequency during an ionospheric heating campaign at European Incoherent Scatter near Tromsø, Norway, are reported. When the pump frequency is slightly above the fifth electron gyrofrequency, the UHF radar observation shows some apparent enhancements over a wide altitude range in radar echo, ion line, and electron density respectively, which are apparently altitude independent and consistent temporally with the upshifting and spread of plasma line around the reflection altitude. However, they do not, in fact, correspond to true increase in electron density. Based on some existing theories, some discussions are presented to try to explain the above enhancements and the upshifting and spread of plasma line. Even so, the mechanism remains to be determined. In addition, the observation also shows some enhancements in electron temperature as a function of pump frequency around the reflection altitude of the pump, which are dependent on the behavior of dispersion of the upper hybrid wave near the fifth electron gyrofrequency.

  6. Density fitting for three-electron integrals in explicitly correlated electronic structure theory

    SciTech Connect

    Womack, James C.; Manby, Frederick R.

    2014-01-28

    The principal challenge in using explicitly correlated wavefunctions for molecules is the evaluation of nonfactorizable integrals over the coordinates of three or more electrons. Immense progress was made in tackling this problem through the introduction of a single-particle resolution of the identity. Decompositions of sufficient accuracy can be achieved, but only with large auxiliary basis sets. Density fitting is an alternative integral approximation scheme, which has proven to be very reliable for two-electron integrals. Here, we extend density fitting to the treatment of all three-electron integrals that appear at the MP2-F12/3*A level of theory. We demonstrate that the convergence of energies with respect to auxiliary basis size is much more rapid with density fitting than with the traditional resolution-of-the-identity approach.

  7. Electron density in the intermediate heights for low latitude stations: observations and models

    NASA Astrophysics Data System (ADS)

    Mosert, M.; Radicella, S. M.; Adeniyi, J. O.; Ezquer, R. G.; Jadur, C.

    The electron density (NF1) and height (hF1) of the F1 inflection point measured at three low latitude ionosonde stations were compared with the parameters of the N170 point (electron density at 170 km) and with those predicted by the IRI model. The validity of the empirical equation proposed by Radicella and Mosert to predict the height hF1 was checked. Daytime electron density profiles from Ibadan, Ouagadougou and Tucumán covering different seasonal and solar activity conditions were used in the study. The results indicate that the two points are close together most of the time and that the Radicella-Mosert formula descrbies the data better than the current IRI model.

  8. Measurement of the lunar neutron density profile

    NASA Technical Reports Server (NTRS)

    Woolum, D. S.; Burnett, D. S.; Furst, M.; Weiss, J. R.

    1975-01-01

    Relatively small discrepancies between Apollo 17 lunar neutron probe experiment (LNPE) data and theoretical calculations by Lingenfelter, Canfield, and Hampel in the effect of Cd absorption on the neutron density, and in the relative Sm-149 to Gd-157 capture rates reported previously, imply that the true lunar Gd-157 capture rate is about one-half of that derived theoretically.

  9. Baseline Bone Mineral Density Measurements Key to Future Testing Intervals

    MedlinePlus

    ... on Research 2012 May 2012 (historical) Baseline Bone Mineral Density Measurements Key to Future Testing Intervals How often a woman should have bone mineral density (BMD) tests to track bone mass is ...

  10. Automated Processing of ISIS Topside Ionograms into Electron Density Profiles

    NASA Technical Reports Server (NTRS)

    Reinisch, bodo W.; Huang, Xueqin; Bilitza, Dieter; Hills, H. Kent

    2004-01-01

    Modeling of the topside ionosphere has for the most part relied on just a few years of data from topside sounder satellites. The widely used Bent et al. (1972) model, for example, is based on only 50,000 Alouette 1 profiles. The International Reference Ionosphere (IRI) (Bilitza, 1990, 2001) uses an analytical description of the graphs and tables provided by Bent et al. (1972). The Alouette 1, 2 and ISIS 1, 2 topside sounder satellites of the sixties and seventies were ahead of their times in terms of the sheer volume of data obtained and in terms of the computer and software requirements for data analysis. As a result, only a small percentage of the collected topside ionograms was converted into electron density profiles. Recently, a NASA-funded data restoration project has undertaken and is continuing the process of digitizing the Alouette/ISIS ionograms from the analog 7-track tapes. Our project involves the automated processing of these digital ionograms into electron density profiles. The project accomplished a set of important goals that will have a major impact on understanding and modeling of the topside ionosphere: (1) The TOPside Ionogram Scaling and True height inversion (TOPIST) software was developed for the automated scaling and inversion of topside ionograms. (2) The TOPIST software was applied to the over 300,000 ISIS-2 topside ionograms that had been digitized in the fkamework of a separate AISRP project (PI: R.F. Benson). (3) The new TOPIST-produced database of global electron density profiles for the topside ionosphere were made publicly available through NASA s National Space Science Data Center (NSSDC) ftp archive at . (4) Earlier Alouette 1,2 and ISIS 1, 2 data sets of electron density profiles from manual scaling of selected sets of ionograms were converted fiom a highly-compressed binary format into a user-friendly ASCII format and made publicly available through nssdcftp.gsfc.nasa.gov. The new database for the topside

  11. Electron density profiles from ionograms - Comparisons with rocket profiles.

    NASA Technical Reports Server (NTRS)

    Wright, J. W.; Paul, A. K.

    1973-01-01

    From a series of ten rocket flights at Wallops Island conducted by the University of Illinois, detailed electron density profiles are available in the altitude range 60-120 km. Concurrent ionograms from a nearby conventional ionosonde of good sensitivity and precision, have been reduced to N(h) profiles by the NOAA methods. Special attention is given to the needs for accurate ionosonde calibration, proper ionogram interpretation, and corrections for underlying ionization, 'valley' ionization, and effects of lateral-gradients. Proper corrections in the present cases yield profiles by ionogram inversion which agree to within a few percent in density, and a few hundred meters or less in height, with the rocket results.

  12. Simulations of the electron cloud buildup and its influence on the microwave transmission measurement

    NASA Astrophysics Data System (ADS)

    Haas, Oliver Sebastian; Boine-Frankenheim, Oliver; Petrov, Fedor

    2013-11-01

    An electron cloud density in an accelerator can be measured using the Microwave Transmission (MWT) method. The aim of our study is to evaluate the influence of a realistic, nonuniform electron cloud on the MWT. We conduct electron cloud buildup simulations for beam pipe geometries and bunch parameters resembling roughly the conditions in the CERN SPS. For different microwave waveguide modes the phase shift induced by a known electron cloud density is obtained from three different approaches: 3D Particle-In-Cell (PIC) simulation of the electron response, a 2D eigenvalue solver for waveguide modes assuming a dielectric response function for cold electrons, a perturbative method assuming a sufficiently smooth density profile. While several electron cloud parameters, such as temperature, result in minor errors in the determined density, the transversely inhomogeneous density can introduce a large error in the measured electron density. We show that the perturbative approach is sufficient to describe the phase shift under realistic electron cloud conditions. Depending on the geometry of the beam pipe, the external magnetic field configuration and the used waveguide mode, the electron cloud density can be concentrated at the beam pipe or near the beam pipe center, leading to a severe over- or underestimation of the electron density. Electron cloud distributions are very inhomogeneous, especially in dipoles. These inhomogeneities affect the microwave transmission measurement results. Electron density might be over- or underestimated, depending on setup. This can be quantified with several models, e.g. a perturbative approach.

  13. Procedure for Uranium-Molybdenum Density Measurements and Porosity Determination

    SciTech Connect

    Prabhakaran, Ramprashad; Devaraj, Arun; Joshi, Vineet V.; Lavender, Curt A.

    2016-08-13

    The purpose of this document is to provide guidelines for preparing uranium-molybdenum (U-Mo) specimens, performing density measurements, and computing sample porosity. Typical specimens (solids) will be sheared to small rectangular foils, disks, or pieces of metal. A mass balance, solid density determination kit, and a liquid of known density will be used to determine the density of U-Mo specimens using the Archimedes principle. A standard test weight of known density would be used to verify proper operation of the system. By measuring the density of a U-Mo sample, it is possible to determine its porosity.

  14. The effective density of randomly moving electrons and related characteristics of materials with degenerate electron gas

    SciTech Connect

    Palenskis, V.

    2014-04-15

    Interpretation of the conductivity of metals, of superconductors in the normal state and of semiconductors with highly degenerate electron gas remains a significant issue if consideration is based on the classical statistics. This study is addressed to the characterization of the effective density of randomly moving electrons and to the evaluation of carrier diffusion coefficient, mobility, and other parameters by generalization of the widely published experimental results. The generalized expressions have been derived for various kinetic parameters attributed to the non-degenerate and degenerate electron gas, by analyzing a random motion of the single type carriers in homogeneous materials. The values of the most important kinetic parameters for different metals are also systematized and discussed. It has been proved that Einstein's relation between the diffusion coefficient and the drift mobility of electrons is held for any level of degeneracy if the effective density of randomly moving carriers is properly taken into account.

  15. Electron star birth: a continuous phase transition at nonzero density.

    PubMed

    Hartnoll, Sean A; Petrov, Pavel

    2011-03-25

    We show that charged black holes in anti-de Sitter spacetime can undergo a third-order phase transition at a critical temperature in the presence of charged fermions. In the low temperature phase, a fraction of the charge is carried by a fermion fluid located a finite distance from the black hole. In the zero temperature limit, the black hole is no longer present and all charge is sourced by the fermions. The solutions exhibit the low temperature entropy density scaling s~T(2/z) anticipated from the emergent IR criticality of recently discussed electron stars.

  16. Charge density waves in strongly correlated electron systems

    NASA Astrophysics Data System (ADS)

    Chen, Chih-Wei; Choe, Jesse; Morosan, E.

    2016-08-01

    Strong electron correlations are at the heart of many physical phenomena of current interest to the condensed matter community. Here we present a survey of the mechanisms underlying such correlations in charge density wave (CDW) systems, including the current theoretical understanding and experimental evidence for CDW transitions. The focus is on emergent phenomena that result as CDWs interact with other charge or spin states, such as magnetism and superconductivity. In addition to reviewing the CDW mechanisms in 1D, 2D, and 3D systems, we pay particular attention to the prevalence of this state in two particular classes of compounds, the high temperature superconductors (cuprates) and the layered transition metal dichalcogenides. The possibilities for quantum criticality resulting from the competition between magnetic fluctuations and electronic instabilities (CDW, unconventional superconductivity) are also discussed.

  17. Discriminating the trapped electron modes contribution in density fluctuation spectra

    NASA Astrophysics Data System (ADS)

    Arnichand, H.; Sabot, R.; Hacquin, S.; Krämer-Flecken, A.; Bourdelle, C.; Citrin, J.; Garbet, X.; Giacalone, J. C.; Guirlet, R.; Hillesheim, J. C.; Meneses, L.

    2015-09-01

    Quasi-coherent (QC) modes have been reported for more than 10 years in reflectometry fluctuations spectra in the core region of fusion plasmas. They have characteristics in-between coherent and broadband fluctuations as they oscillate at a marked frequency but have a wide spectrum. This work presents further evidences of the link recently established between QC modes and the trapped electron modes (TEM) instabilities (Arnichand et al 2014 Nucl. Fusion 54 123017). In electron cyclotron resonance heated discharges of Tore Supra, an enhancement of QC modes amplitude is observed in a region where TEM cause impurity transport and turbulence. In JET Ohmic plasmas, QC modes disappear during density ramp-up and current ramp-down. This is reminiscent of Tore Supra and TEXTOR observations during transitions from the linear Ohmic confinement (LOC) to the saturated Ohmic confinement (SOC) regimes. Evidencing TEM activity then becomes experimentally possible via analysis of fluctuation spectra.

  18. MEASUREMENTS OF RAPID DENSITY FLUCTUATIONS IN THE SOLAR WIND

    SciTech Connect

    Malaspina, D. M.; Ergun, R. E.; Kellogg, P. J.; Bale, S. D.

    2010-03-01

    The power spectrum of density fluctuations in the solar wind is inferred by tracking small timescale changes in the electron plasma frequency during periods of strong Langmuir wave activity. STEREO electric field waveform data are used to produce time profiles of plasma density from which the density power spectrum is derived. The power spectra obtained by this method extend the observed frequency range by an order of magnitude while remaining consistent with previous results near a few Hertz. Density power spectral indices are found to be organized by the angle between the local magnetic field and the solar wind direction, indicating significant anisotropy in solar wind high-frequency density turbulence.

  19. A new interferometry-based electron density fluctuation diagnostic on Alcator C-Mod.

    PubMed

    Kasten, C P; Irby, J H; Murray, R; White, A E; Pace, D C

    2012-10-01

    The two-color interferometry diagnostic on the Alcator C-Mod tokamak has been upgraded to measure fluctuations in the electron density and density gradient for turbulence and transport studies. Diagnostic features and capabilities are described. In differential mode, fast phase demodulation electronics detect the relative phase change between ten adjacent, radially-separated (ΔR = 1.2 cm, adjustable), vertical-viewing chords, which allows for measurement of the line-integrated electron density gradient. The system can be configured to detect the absolute phase shift of each chord by comparison to a local oscillator, measuring the line-integrated density. Each chord is sensitive to density fluctuations with k(R) < 20.3 cm(-1) and is digitized at up to 10 MS/s, resolving aspects of ion temperature gradient-driven modes and other long-wavelength turbulence. Data from C-Mod discharges is presented, including observations of the quasi-coherent mode in enhanced D-alpha H-mode plasmas and the weakly coherent mode in I-mode.

  20. A new interferometry-based electron density fluctuation diagnostic on Alcator C-Moda)

    NASA Astrophysics Data System (ADS)

    Kasten, C. P.; Irby, J. H.; Murray, R.; White, A. E.; Pace, D. C.

    2012-10-01

    The two-color interferometry diagnostic on the Alcator C-Mod tokamak has been upgraded to measure fluctuations in the electron density and density gradient for turbulence and transport studies. Diagnostic features and capabilities are described. In differential mode, fast phase demodulation electronics detect the relative phase change between ten adjacent, radially-separated (ΔR = 1.2 cm, adjustable), vertical-viewing chords, which allows for measurement of the line-integrated electron density gradient. The system can be configured to detect the absolute phase shift of each chord by comparison to a local oscillator, measuring the line-integrated density. Each chord is sensitive to density fluctuations with kR < 20.3 cm-1 and is digitized at up to 10 MS/s, resolving aspects of ion temperature gradient-driven modes and other long-wavelength turbulence. Data from C-Mod discharges is presented, including observations of the quasi-coherent mode in enhanced D-alpha H-mode plasmas and the weakly coherent mode in I-mode.

  1. Monte Carlo modeling of electron density in hypersonic rarefied gas flows

    SciTech Connect

    Fan, Jin; Zhang, Yuhuai; Jiang, Jianzheng

    2014-12-09

    The electron density distribution around a vehicle employed in the RAM-C II flight test is calculated with the DSMC method. To resolve the mole fraction of electrons which is several orders lower than those of the primary species in the free stream, an algorithm named as trace species separation (TSS) is utilized. The TSS algorithm solves the primary and trace species separately, which is similar to the DSMC overlay techniques; however it generates new simulated molecules of trace species, such as ions and electrons in each cell, basing on the ionization and recombination rates directly, which differs from the DSMC overlay techniques based on probabilistic models. The electron density distributions computed by TSS agree well with the flight data measured in the RAM-C II test along a decent trajectory at three altitudes 81km, 76km, and 71km.

  2. Exploring the electron density in plasmas induced by extreme ultraviolet radiation in argon

    NASA Astrophysics Data System (ADS)

    van der Horst, R. M.; Beckers, J.; Osorio, E. A.; Banine, V. Y.

    2015-07-01

    The new generation of lithography tools use high energy EUV radiation which ionizes the present background gas due to photoionization. To predict and understand the long term impact on the highly delicate mirrors, it is essential to characterize these kinds of EUV-induced plasmas. We measured the electron density evolution in argon gas during and just after irradiation by a short pulse of EUV light at 13.5 nm by applying microwave cavity resonance spectroscopy. Dependencies on EUV pulse energy and gas pressure have been explored over a range relevant for industrial applications. Our experimental results show that the maximum reached electron density depends linearly on pulse energy. A quadratic dependence caused by photoionization and subsequent electron impact ionization by free electrons is found from experiments where the gas pressure is varied. This is demonstrated by our theoretical estimates presented in this manuscript as well.

  3. Effective electron displacements: A tool for time-dependent density functional theory computational spectroscopy

    SciTech Connect

    Guido, Ciro A. Cortona, Pietro; Adamo, Carlo

    2014-03-14

    We extend our previous definition of the metric Δr for electronic excitations in the framework of the time-dependent density functional theory [C. A. Guido, P. Cortona, B. Mennucci, and C. Adamo, J. Chem. Theory Comput. 9, 3118 (2013)], by including a measure of the difference of electronic position variances in passing from occupied to virtual orbitals. This new definition, called Γ, permits applications in those situations where the Δr-index is not helpful: transitions in centrosymmetric systems and Rydberg excitations. The Γ-metric is then extended by using the Natural Transition Orbitals, thus providing an intuitive picture of how locally the electron density changes during the electronic transitions. Furthermore, the Γ values give insight about the functional performances in reproducing different type of transitions, and allow one to define a “confidence radius” for GGA and hybrid functionals.

  4. Estimates of the Electron Density Profile on LTX Using FMCW Reflectometry and mm-Wave Interferometry

    NASA Astrophysics Data System (ADS)

    Peebles, W. A.; Kubota, S.; Nguyen, X. V.; Holoman, T.; Kaita, R.; Kozub, T.; Labrie, D.; Schmitt, J. C.; Majeski, R.

    2014-10-01

    An FMCW (frequency-modulated continuous-wave) reflectometer has been installed on the Lithium Tokamak Experiment (LTX) for electron density profile and fluctuation measurements. This diagnostic consists of two channels using bistatic antennas with a combined frequency coverage of 13.5 -33 GHz, which corresponds to electron density measurements in the range of 0 . 2 - 1 . 3 ×1013 cm-3 (in O-mode). Initial measurements will utilize O-mode polarization, which will require modeling of the plasma edge. Reflections from the center stack (delayometry above the peak cutoff frequency), as well as line density measurements from a 296 GHz interferometer (single-chord, radial midplane), will provide constraints for the profile reconstruction/estimate. Typical chord-averaged line densities on LTX range from 2 -6 ×1012 cm-3, which correspond to peak densities of 0 . 6 - 1 . 8 ×1013 cm-3 assuming a parabolic shape. If available, EFIT/LRDFIT results will provide additional constraints, as well as the possibility of utilizing data from measurements with X-mode or dual-mode (simultaneous O- and X-mode) polarization. Supported by U.S. DoE Grants DE-FG02-99ER54527 and DE-AC02-09CH11466.

  5. Imaging polychromator for density measurements of polystyrene pellet cloud on the Large Helical Device

    SciTech Connect

    Sharov, I. A. Sergeev, V. Yu.; Miroshnikov, I. V.; Tamura, N.; Sudo, S.; Kuteev, B. V.

    2015-04-15

    Experimental data on spatial distributions of a pellet cloud electron density are necessary for the development of many applications of pellet injection, namely, plasma fuelling, discharge control, and plasma diagnostics. An improved approach of electron density measurements inside the cloud of a polystyrene pellet ablating in hot plasma of the large helical device is described. Density values of (1-30) × 10{sup 16} cm{sup −3} depending on the background plasma parameters and distance from the solid pellet were measured.

  6. Spatially resolved density and ionization measurements of shocked foams using x-ray fluorescence

    DOE PAGES

    MacDonald, M. J.; Keiter, P. A.; Montgomery, D. S.; ...

    2016-09-22

    We present experiments at the Trident laser facility demonstrating the use of x-ray fluorescence (XRF) to simultaneously measure density, ionization state populations, and electron temperature in shocked foams. An imaging x-ray spectrometer was used to obtain spatially-resolved measurements of Ti K-more » $$\\alpha$$ emission. Density profiles were measured from K-$$\\alpha$$ intensity. Ti ionization state distributions and electron temperatures were inferred by fitting K-$$\\alpha$$ spectra to spectra from CRETIN simulations. This study shows that XRF provides a powerful tool to complement other diagnostics to make equation of state measurements of shocked materials containing a suitable tracer element.« less

  7. Spatially resolved density and ionization measurements of shocked foams using x-ray fluorescence

    SciTech Connect

    MacDonald, M. J.; Keiter, P. A.; Montgomery, D. S.; Scott, H. A.; Biener, M. M.; Fein, J. R.; Fournier, K. B.; Gamboa, E. J.; Kemp, G. E.; Klein, S. R.; Kuranz, C. C.; LeFevre, H. J.; Manuel, M. J. -E.; Wan, W. C.; Drake, R. P.

    2016-09-22

    We present experiments at the Trident laser facility demonstrating the use of x-ray fluorescence (XRF) to simultaneously measure density, ionization state populations, and electron temperature in shocked foams. An imaging x-ray spectrometer was used to obtain spatially-resolved measurements of Ti K-$\\alpha$ emission. Density profiles were measured from K-$\\alpha$ intensity. Ti ionization state distributions and electron temperatures were inferred by fitting K-$\\alpha$ spectra to spectra from CRETIN simulations. This study shows that XRF provides a powerful tool to complement other diagnostics to make equation of state measurements of shocked materials containing a suitable tracer element.

  8. Ionospheric plasma density irregularities measured by stimulated electromagnetic emission

    NASA Astrophysics Data System (ADS)

    Norin, L.; Grach, S. M.; Leyser, T. B.; Thidé, B.; Sergeev, E. N.; Berlin, M.

    2008-09-01

    It is well known that ionospheric plasma turbulence can be conveniently generated by controlled injection of powerful high-frequency radio beams from the ground. Irradiation of the ionosphere with such radio waves leads to the formation of plasma density structures, striations, and the generation of secondary electromagnetic radiation, a phenomenon known as stimulated electromagnetic emission (SEE). In this paper we present experimental results of the dependence of SEE on decreasing excitation levels of the striations. In the experiments the frequency of the injected radio beam was varied near the fifth harmonic of the local ionospheric electron gyro frequency. We use the SEE measurements to obtain transverse length scales of the striations involved in the generation of the SEE. Our results show that different spectral features of the SEE display different temporal dynamics, suggesting that they are related to striations with different transverse length scales (1 ≲ l⊥ ≲ 25 m).

  9. Electron response in van der Waals density functionals

    NASA Astrophysics Data System (ADS)

    Hyldgaard, Per

    2013-03-01

    There is significant interest in density functional theory (DFT) of dispersive or van der Waals (vdW) interactions and in DFT studies of sparse systems where vdW forces contribute to the cohesion and behavior. The Rutgers-Chalmers van der Waals density functional (vdW-DF) method [PRL 92, 246401 (2004); PRB 76, 125112 (2007)] is a nonempirical approach to calculate vdW bonding and for DFT characterizations of sparse matter. The vdW-DF framework is defined by a single exchange-correlation density functional that rests on a plasmon-type description for both semilocal components and for a parameter-free evaluation of nonlocal correlation. My talk summarizes a set of vdW-DF studies that seeks to map and analyze details in the vdW-DF electron-response nature. The purpose is in part to extract consequences that can facilitate an experiment-theory comparison that goes beyond binding geometries and energies. The aim is also to seek implications that can help develop the vdW-DF framework. I present an analysis of the relative importance of morphology, screening (image-plane formation), and collective effects in the vdW-DF description of molecular systems. In addition, I compare vdW-DF results with Cu(111) experiments that tests the electron-response behavior in terms of adsorption-induced band shifts, the form of the overall light-molecule physisorption potential, and the corrugation in the kinetic-energy repulsion of molecules at surfaces. Overall, the vdW-DF studies suggest the importance of benchmarking vdW methods across different length scales and by exploring the variation that arise when related structures have a different balance between exchange repulsion and vdW attraction.

  10. Thomson Scattering Measurements of Temperature and Density in a Low-Density, Laser-Driven Magnetized Plasma

    NASA Astrophysics Data System (ADS)

    Schaeffer, D. B.; Montgomery, D. S.; Bondarenko, A. S.; Morton, L. A.; Johnson, R. P.; Shimada, T.; Constantin, C. G.; Everson, E. T.; Letzring, S. A.; Gaillard, S. A.; Flippo, K. A.; Glenzer, S. H.; Niemann, C.

    2012-02-01

    We present electron temperature and density measurements from Thomson scattering on recent collisionless shock experiments on the Trident laser at Los Alamos National Laboratory. A graphite target placed inside a static magnetic field (lesssim1 kG) created by a 50 cm-diameter Helmholtz coil was ablated by a 1053 nm beam, which created a low-density, magnetized plasma. A separate 527 nm beam was used for Thomson scattering to characterize the plasma 3 cm radially from the target and 0.5-8.5 μs after ablation. The electron temperature was found to be relatively constant over 8 μs at 11-13 eV and, combined with Rayleigh scattering, the electron density was found to be 2 × 1014-4 × 1014 cm-3 over the same timescale. Several carbon emission lines were also observed in the Thomson spectrum and were utilized to independently measure the electron temperature and density and to characterize the plasma charge state.

  11. Exploring the electron density in plasma induced by EUV radiation: I. Experimental study in hydrogen

    NASA Astrophysics Data System (ADS)

    van der Horst, R. M.; Beckers, J.; Osorio, E. A.; Astakhov, D. I.; Goedheer, W. J.; Lee, C. J.; Ivanov, V. V.; Krivtsum, V. M.; Koshelev, K. N.; Lopaev, D. V.; Bijkerk, F.; Banine, V. Y.

    2016-04-01

    Plasmas induced by EUV radiation are unique since they are created without the need of any discharge. Moreover, it is essential to characterize these plasmas to understand and predict their long term impact on highly delicate optics in EUV lithography tools. In this paper we study plasmas induced by 13.5 nm EUV radiation in hydrogen gas. The electron density is measured temporally resolved using a non-invasive technique known as microwave cavity resonance spectroscopy. The influence of the EUV pulse energy and gas pressure on the temporal evolution of the electron density has been explored over a parameter range relevant for industry. Our experimental results show that the maximum electron density is in the order of 1014 m-3 and depends linearly on the EUV pulse energy. Furthermore, the maximum electron density depends quadratically on the pressure; the linear term is caused by photoionization and the quadratic term by subsequent electron impact ionization. The decay of the plasma is governed by ambipolar diffusion and, hence, becomes slower at elevated pressures. Similarities and differences of the same processes in argon are highlighted in this paper.

  12. Electrode material dependence of two-dimensional electron and vapour density distribution over vacuum arc discharge

    NASA Astrophysics Data System (ADS)

    Inada, Y.; Matsuoka, S.; Kumada, A.; Ikeda, H.; Hidaka, K.

    2017-03-01

    Electrode material dependence of intense-mode vacuum arc behaviour was systematically investigated by using the Shack-Hartmann method capable of simultaneously visualising two-dimensional electron and metal vapour density distributions from single-shot recordings. The electrode materials studied included Cu, CuCr (Cu75Cr25 wt. %), WC, and AgWC (Ag40WC60 wt. %). A comparison between the Cu and CuCr electrodes showed that the metal vapour densities for the CuCr decreased in an even shorter time scale than for the Cu. In the case of the WC electrodes, the widths of the electron density distributions became narrower as the arc current decreased although the electron densities hardly decreased in the decaying process of the arc current. The density measurements conducted at the late stage of the vacuum arcs demonstrated that the metal vapour densities around the anode were maintained at the highest value for the AgWC among the electrode materials in this study.

  13. Electron temperatures and densities in the venus ionosphere: pioneer venus orbiter electron temperature probe results.

    PubMed

    Brace, L H; Theis, R F; Krehbiel, J P; Nagy, A F; Donahue, T M; McElroy, M B; Pedersen, A

    1979-02-23

    Altitude profiles of electron temperature and density in the ionosphere of Venus have been obtained by the Pioneer Venus orbiter electron temperatutre probe. Elevated temperatutres observed at times of low solar wind flux exhibit height profiles that are consistent with a model in which less than 5 percent of the solar wind energy is deposited at the ionopause and is conducted downward through an unmagnetized ionosphere to the region below 200 kilomneters where electron cooling to the neutral atmosphere proceeds rapidly. When solar wind fluxes are higher, the electron temperatures and densities are highly structured and the ionopause moves to lower altitudes. The ionopause height in the late afternoon sector observed thus far varies so widely from day to (day that any height variation with solar zenith angle is not apparent in the observations. In the neighborhood of the ionopause, measuremnents of plasma temperatures and densities and magnetic field strength indicate that an induced magnetic barrier plays an important role in the pressure transfer between the solar wind and the ionosphere. The bow, shock is marked by a distinct increase in electron current collected by the instrument, a featutre that provides a convenient identification of the bow shock location.

  14. Bayesian modeling of JET Li-BES for edge electron density profiles using Gaussian processes

    NASA Astrophysics Data System (ADS)

    Kwak, Sehyun; Svensson, Jakob; Brix, Mathias; Ghim, Young-Chul; JET Contributors Collaboration

    2015-11-01

    A Bayesian model for the JET lithium beam emission spectroscopy (Li-BES) system has been developed to infer edge electron density profiles. The 26 spatial channels measure emission profiles with ~15 ms temporal resolution and ~1 cm spatial resolution. The lithium I (2p-2s) line radiation in an emission spectrum is calculated using a multi-state model, which expresses collisions between the neutral lithium beam atoms and the plasma particles as a set of differential equations. The emission spectrum is described in the model including photon and electronic noise, spectral line shapes, interference filter curves, and relative calibrations. This spectral modeling gets rid of the need of separate background measurements for calculating the intensity of the line radiation. Gaussian processes are applied to model both emission spectrum and edge electron density profile, and the electron temperature to calculate all the rate coefficients is obtained from the JET high resolution Thomson scattering (HRTS) system. The posterior distributions of the edge electron density profile are explored via the numerical technique and the Markov chain Monte Carlo (MCMC) samplings. See the Appendix of F. Romanelli et al., Proceedings of the 25th IAEA Fusion Energy Conference 2014, Saint Petersburg, Russia.

  15. Optical pressure/density measuring means

    DOEpatents

    Veligdan, J.T.

    1995-05-09

    An apparatus and method are disclosed for rapidly and accurately determining the pressure of a fluid medium in either a static or dynamic state. The pressure is determined by making a measurement of the velocity of a light beam that is directed through the fluid medium along a pathway that enables an integrated pressure measurement to be made along the pathway, rather than making such a measurement only at a single point in the medium. A HeNe laser is configured to emit a beam of two frequencies separated by about 2 MHz. One of these beam frequencies is directed through the fluid medium and is reflected back through the medium to a non-linear diode detector. The other beam frequency is passed directly to a diode detector without traversing said medium. The diode detector is operated to determine the frequency shift or beat frequency between the two beam frequencies. Any variation in the frequency of said reflected beam that is caused by a change in its velocity as it is passed through the fluid medium causes a change in the beat frequency. This beat frequency change is then converted to an output signal value corresponding to the pressure of the medium. The measurement instrument apparatus is remotely positioned relative to the medium being measured, thus the apparatus is immune from electro-magnetic interference and can operate in conditions of high radiation, corrosion and extraordinarily high temperature. 4 figs.

  16. Optical pressure/density measuring means

    DOEpatents

    Veligdan, James T.

    1995-05-09

    An apparatus and method for rapidly and accurately determining the pressure of a fluid medium in either a static or dynamic state. The pressure is determined by making a measurement of the velocity of a light beam that is directed through the fluid medium along a pathway that enables an integrated pressure measurement to be made along the pathway, rather than making such a measurement only at a single point in the medium. A HeNe laser is configured to emit a beam of two frequencies separated by about 2 MHz. One of these beam frequencies is directed through the fluid medium and is reflected back through the medium to a non-linear diode detector. The other beam frequency is passed directly to a diode detector without traversing said medium. The diode detector is operated to determine the frequency shift or beat frequency between the two beam frequencies. Any variation in the frequency of said reflected beam that is caused by a change in its velocity as it is passed through the fluid medium causes a change in the beat frequency. This beat frequency change is then converted to an output signal value corresponding to the pressure of the medium. The measurement instrument apparatus is remotely positioned relative to the medium being measured, thus the apparatus is immune from electro-magnetic interference and can operate in conditions of high radiation, corrosion and extraordinarily high temperature.

  17. Development of High Power Electron Beam Measuring and Analyzing System for Microwave Vacuum Electron Devices

    NASA Astrophysics Data System (ADS)

    Ruan, C. J.; Wu, X. L.; Li, Q. S.; Li, C. S.

    The measurement and analysis of high power electron beam during its formation and transmission are the basic scientific problems and key techniques for the development of high performance microwave vacuum electron devices, which are widely used in the fields of military weapon, microwave system and scientific instruments. In this paper, the dynamic parameters measurement and analysis system being built in Institute of Electronics, Chinese Academy of Sciences (IECAS) recently are introduced. The instrument are designed to determine the cross-section, the current density, and the energy resolution of the high power electron beam during its formation and transmission process, which are available both for the electron gun and the electron optics system respectively. Then the three dimension trajectory images of the electron beam can be rebuilt and display with computer controlled data acquisition and processing system easily. Thus, much more complicated structures are considered and solved completely to achieve its detection and analysis, such as big chamber with 10-6 Pa high vacuum system, the controlled detector movement system in axis direction with distance of 600 mm inside the vacuum chamber, the electron beam energy analysis system with high resolution of 0.5%, and the electron beam cross-section and density detector using the YAG: Ce crystal and CCD imaging system et al. At present, the key parts of the instrument have been finished, the cross-section experiment of the electron beam have been performed successfully. Hereafter, the instrument will be used to measure and analyze the electron beam with the electron gun and electron optics system for the single beam and multiple beam klystron, gyrotron, sheet beam device, and traveling wave tube etc. thoroughly.

  18. Measurements of uranium mass confined in high density plasmas

    NASA Technical Reports Server (NTRS)

    Stoeffler, R. C.

    1976-01-01

    An X-ray absorption method for measuring the amount of uranium confined in high density, rf-heated uranium plasmas is described. A comparison of measured absorption of 8 keV X-rays with absorption calculated using Beer Law indicated that the method could be used to measure uranium densities from 3 times 10 to the 16th power atoms/cu cm to 5 times 10 to the 18th power atoms/cu cm. Tests were conducted to measure the density of uranium in an rf-heated argon plasma with UF6 infection and with the power to maintain the discharge supplied by a 1.2 MW rf induction heater facility. The uranium density was measured as the flow rate through the test chamber was varied. A maximum uranium density of 3.85 times 10 to the 17th power atoms/cu cm was measured.

  19. Effect of fast drifting electrons on electron temperature measurement with a triple Langmuir probe

    SciTech Connect

    Biswas, Subir Chowdhury, Satyajit; Pal, Rabindranath

    2015-08-14

    Triple Langmuir Probe (TLP) is a widely used diagnostics for instantaneous measurement of electron temperature and density in low temperature laboratory plasmas as well as in edge region of fusion plasma devices. Presence of a moderately energetic flowing electron component, constituting only a small fraction of the bulk electrons, is also a generally observed scenario in plasma devices, where plasmas are produced by electron impact ionization of neutrals. A theoretical analysis of its effect on interpretation of the TLP data for bulk electron temperature measurement is presented here assuming electron velocity distribution is not deviating substantially from a Maxwellian. The study predicts conventional expression from standard TLP theory to give overestimated value of bulk electron temperature. Correction factor is significant and largely depends on population density, temperature, and energy of the fast component. Experimental verification of theoretical results is obtained in the magnetized plasma linear experimental device of Saha Institute of Nuclear Physics where plasma is produced by an electron cyclotron resonance method and known to have a fast flowing electron component.

  20. Empirical models of the electron temperature and density in the nightside venus ionosphere.

    PubMed

    Brace, L H; Theis, R F; Niemann, H B; Mayr, H G; Hoegy, W R; Nagy, A F

    1979-07-06

    Empirical models of the electron temperature and electron density of the late afternoon and nightside Venus ionosphere have been derived from Pioneer Venus measurements acquired between 10 December 1978 and 23 March 1979. The models describe the average ionosphere conditions near 18 degrees N latitude between 150 and 700 kilometers altitude for solar zenith angles of 80 degrees to 180 degrees . The average index of solar flux was 200. A major feature of the density model is the factor of 10 decrease beyond 90 degrees followed by a very gradual decrease between 120 degrees and 180 degrees . The density at 150 degrees is about five times greater than observed by Venera 9 and 10 at solar minimum (solar flux approximately 80), a difference that is probably related to the effects of increased solar activity on the processes that maintain the nightside ionosphere. The nightside electron density profile from the model (above 150 kilometers) can be reproduced theoretically either by transport of 0(+) ions from the dayside or by precipitation of low-energy electrons. The ion transport process would require a horizontal flow velocity of about 300 meters per second, a value that is consistent with other Pioneer Venus observations. Although currently available energetic electron data do not yet permit the role of precipitation to be evaluated quantitatively, this process is clearly involved to some extent in the formation of the nightside ionosphere. Perhaps the most surprising feature of the temperature model is that the electron temperature remains high throughout the nightside ionosphere. These high nocturnal temperatures and the existence of a well-defined nightside ionopause suggest that energetic processes occur across the top of the entire nightside ionosphere, maintaining elevated temperatures. A heat flux of 2 x 10(10) electron volts per square centimeter per second, introduced at the ionopause, is consistent with the average electron temperature profile on the

  1. Multiple Point Dynamic Gas Density Measurements Using Molecular Rayleigh Scattering

    NASA Technical Reports Server (NTRS)

    Seasholtz, Richard; Panda, Jayanta

    1999-01-01

    A nonintrusive technique for measuring dynamic gas density properties is described. Molecular Rayleigh scattering is used to measure the time-history of gas density simultaneously at eight spatial locations at a 50 kHz sampling rate. The data are analyzed using the Welch method of modified periodograms to reduce measurement uncertainty. Cross-correlations, power spectral density functions, cross-spectral density functions, and coherence functions may be obtained from the data. The technique is demonstrated using low speed co-flowing jets with a heated inner jet.

  2. The Peierls instability and charge density wave in one-dimensional electronic conductors

    NASA Astrophysics Data System (ADS)

    Pouget, Jean-Paul

    2016-03-01

    We review salient structural and electronic features associated with the concomitant Peierls-charge density wave (CDW) instabilities observed in most one-dimensional (1D) inorganic and organic electronic conductors. First of all, the genesis of these concepts is placed in an historical perspective. We then present basic experimental facts supporting the general description of these 1D electron-phonon coupled systems developed in the 1970s. In this framework we shall consider in particular the role of 1D fluctuations on both lattice and electronic degrees of freedom, and of the inter-chain Coulomb coupling between CDWs in stabilizing in 3D the Peierls transition at finite temperature. We also clarify, in relation with experimental findings, the various conditions of adiabaticity of the electron-phonon coupling. Finally we illustrate by recent structural measurements the pioneering work of Jacques Friedel on CDW elasticity and plasticity and CDW pinning to defects through the appearance of Friedel oscillations.

  3. Direct Measurement of the Density Matrix of a Quantum System

    NASA Astrophysics Data System (ADS)

    Thekkadath, G. S.; Giner, L.; Chalich, Y.; Horton, M. J.; Banker, J.; Lundeen, J. S.

    2016-09-01

    One drawback of conventional quantum state tomography is that it does not readily provide access to single density matrix elements since it requires a global reconstruction. Here, we experimentally demonstrate a scheme that can be used to directly measure individual density matrix elements of general quantum states. The scheme relies on measuring a sequence of three observables, each complementary to the last. The first two measurements are made weak to minimize the disturbance they cause to the state, while the final measurement is strong. We perform this joint measurement on polarized photons in pure and mixed states to directly measure their density matrix. The weak measurements are achieved using two walk-off crystals, each inducing a polarization-dependent spatial shift that couples the spatial and polarization degrees of freedom of the photons. This direct measurement method provides an operational meaning to the density matrix and promises to be especially useful for large dimensional states.

  4. Method for measuring the density of lightweight materials

    DOEpatents

    Snow, Samuel G.; Giacomelli, Edward J.

    1980-01-01

    This invention relates to a nondestructive method for measuring the density of articles composed of elements having a low atomic number such as plastic and carbon composites. The measurement is accomplished by striking the article with a collimated beam of X radiation, simultaneously monitoring the radiation scattered and the radiation transmitted by the article, then relating the ratio of the radiation scattered to the radiation transmitted with the density of the article. The above method is insensitive to all variables except density.

  5. Relative electron density distribution in a low nd helium dc discharge

    NASA Astrophysics Data System (ADS)

    Ganguly, Biswa N.; Scofield, James D.

    2016-09-01

    The axial and radial variations of the relative electron density distributions have been measured in an obstructed helium dc discharge by a laser collision induced fluorescence (LCIF) from 4 3D to 2 3P state at 447 nm. For this 1.75 Torr, 6.5 mm gap, 1.6 mA helium obstructed gas discharge, the on-axis LCIF intensity is mostly determined by the neutral atom collision. On the basis of this information, we have plotted the LCIF data to obtain a normalized electron density variation in the inter-electrode volume by plotting the ratio, I/-Io n -a x i s Io n -a x i s , where I is the radial variation of the LCIF intensity and Ion-axis is the on-axis LCIF intensity. The normalized LCIF data show an annular current density distribution in this obstructed discharge with the current peaking near the radial boundary of the electrodes.

  6. High Temporal and Spatial Resolution Electron Density Diagnostic for the Edge Plasma based on Stark Broadening

    NASA Astrophysics Data System (ADS)

    Zafar, Abdullah; Martin, Elijah; Shannon, Steve; Isler, Ralph; Caughman, John

    2016-10-01

    Passive spectroscopic measurements of Stark broadening have been reliably used to determine electron density for decades. However, a low-density limit ( 1014 cm-3) exists due to Doppler and instrument broadening of the spectral line profile. A synthetic electron density diagnostic capable of high temporal (ms) and spatial (mm) resolution is currently under development at Oak Ridge National Laboratory. The diagnostic is based on measuring the Stark broadened, Doppler-free, spectral line profile of a Balmar series transition by using an active laser based technique. The diagnostic approach outlined here greatly reduces both of these broadening contributions using Doppler-free saturation spectroscopy (DFSS), allowing access to lower density regimes. The measured profile is then fit to a fully quantum mechanical model including the appropriate electric and magnetic field operators. The modeling and experimental results for this active spectroscopic technique are presented for a magnetized (<=5 T), low-density (1011-1013 cm-3) plasma. Details of applying DFSS to the plasma edge are also discussed.

  7. Nearest Neighbor Classification Using a Density Sensitive Distance Measurement

    DTIC Science & Technology

    2009-09-01

    both the proposed density sensitive distance measurement and Euclidean distance are compared on the Wisconsin Diagnostic Breast Cancer dataset and...proposed density sensitive distance measurement and Euclidean distance are compared on the Wisconsin Diagnostic Breast Cancer dataset and the MNIST...35 1. The Wisconsin Diagnostic Breast Cancer (WDBC) Dataset..........35 2. The

  8. Density gradient free electron collisionally excited x-ray laser

    DOEpatents

    Campbell, E.M.; Rosen, M.D.

    1984-11-29

    An operational x-ray laser is provided that amplifies 3p-3s transition x-ray radiation along an approximately linear path. The x-ray laser is driven by a high power optical laser. The driving line focused optical laser beam illuminates a free-standing thin foil that may be associated with a substrate for improved structural integrity. This illumination produces a generally cylindrically shaped plasma having an essentially uniform electron density and temperature, that exists over a long period of time, and provides the x-ray laser gain medium. The x-ray laser may be driven by more than one optical laser beam. The x-ray laser has been successfully demonstrated to function in a series of experimental tests.

  9. Density gradient free electron collisionally excited X-ray laser

    DOEpatents

    Campbell, Edward M.; Rosen, Mordecai D.

    1989-01-01

    An operational X-ray laser (30) is provided that amplifies 3p-3s transition X-ray radiation along an approximately linear path. The X-ray laser (30) is driven by a high power optical laser. The driving line focused optical laser beam (32) illuminates a free-standing thin foil (34) that may be associated with a substrate (36) for improved structural integrity. This illumination produces a generally cylindrically shaped plasma having an essentially uniform electron density and temperature, that exists over a long period of time, and provides the X-ray laser gain medium. The X-ray laser (30) may be driven by more than one optical laser beam (32, 44). The X-ray laser (30) has been successfully demonstrated to function in a series of experimental tests.

  10. Controlling Electron-Phonon Interactions in Graphene at Ultrahigh Carrier Densities

    NASA Astrophysics Data System (ADS)

    Efetov, Dmitri K.; Kim, Philip

    2010-12-01

    We report on the temperature dependent electron transport in graphene at different carrier densities n. Employing an electrolytic gate, we demonstrate that n can be adjusted up to 4×1014cm-2 for both electrons and holes. The measured sample resistivity ρ increases linearly with temperature T in the high temperature limit, indicating that a quasiclassical phonon distribution is responsible for the electron scattering. As T decreases, the resistivity decreases more rapidly following ρ(T)˜T4. This low temperature behavior can be described by a Bloch-Grüneisen model taking into account the quantum distribution of the two-dimensional acoustic phonons in graphene. We map out the density dependence of the characteristic temperature ΘBG defining the crossover between the two distinct regimes, and show that, for all n, ρ(T) scales as a universal function of the normalized temperature T/ΘBG.

  11. Plasmaspheric Electron Densities and Plasmashere-Ionosphere Coupling Fluxes

    NASA Astrophysics Data System (ADS)

    Lichtenberger, Janos; Cherneva, Nina; Shevtsov, Boris; Sannikov, Dmitry; Ferencz, Csaba; Koronczay, David

    The Automatic Whistler Detector and Analyzer Network (AWDANet) is able to detect and analyze whistlers in quasi-realtime and can provide equatorial electron density data. The plasmaspheric electron densities and ionosphere-plasmasphere coupling fluxes are key parameters for plasmasphere models in Space Weather related investigations, particularly in modeling charged particle accelerations and losses in Radiation Belts. The global AWDANet [1] detects millions of whistlers in a year. The system has been recently completed with automatic analyzer capability in PLASMON (http://plasmon.elte.hu) project. It is based on a recently developed whistler inversion model [2], that opened the way for an automated process of whistler analysis, not only for single whistler events but for complex analysis of multiple-path propagation whistler groups [3]. In this paper we present the results of quasi-real-time runs processing whistlers from quiet and disturb periods from Karymshina station (Kamchatka, Russia). Refilling rates, that are not yet known in details are also presented for the various periods. 1.Lichtenberger, J., C. Ferencz, L. Bodnár, D. Hamar, and P. Steinbach (2008), Automatic whistler detector and analyzer system: Automatic whistler detector, J. Geophys. Res., 113, A12201, doi:10.1029/2008JA013467. 2. Lichtenberger, J. (2009), A new whistler inversion method, J. Geophys. Res., 114, A07222, doi:10.1029/2008JA013799. 3. Lichtenberger, J., C. Ferencz, D. Hamar, P. Steinbach, C. J. Rodger, M. A. Clilverd, and A. B. Collier (2010), Automatic Whistler Detector and Analyzer system: Implementation of the analyzer algorithm, J. Geophys. Res., 115, A12214, doi:10.1029/2010JA015931.

  12. The behavior of the electron density and temperatue at Millstone Hill during the equinox transition study September 1984

    NASA Technical Reports Server (NTRS)

    Richards, P. G.; Torr, D. G.; Buonsanto, M. J.; Miller, K. L.

    1989-01-01

    The ionospheric electron density and temperature variations is simulated during the equinox transition study in September 1984 and the results are compared with measurements made at Millstone Hill. The agreement between the modeled and measured electron density and temperature for the quiet day (18 September) is very good but there are large differences on the day of the storm (19 September). On the storm day, the measured electron density decreases by a factor of 1.7 over the previous day, while the model density actually increases slightly. The model failure is attributed to an inadequate increase in the ratio of atomic oxygen to molecular neutral densities in the MSIS neutral atmosphere model, for this particular storm. A factor of 3 to 5 increase in the molecular to atomic oxygen density ratio at 300 km is needed to explain the observed decrease in electron density. The effect of vibrationally excited N sub 2 on the electron density were studied and found to be small.

  13. Electron correlation in solids via density embedding theory

    SciTech Connect

    Bulik, Ireneusz W.; Chen, Weibing; Scuseria, Gustavo E.

    2014-08-07

    Density matrix embedding theory [G. Knizia and G. K.-L. Chan, Phys. Rev. Lett. 109, 186404 (2012)] and density embedding theory [I. W. Bulik, G. E. Scuseria, and J. Dukelsky, Phys. Rev. B 89, 035140 (2014)] have recently been introduced for model lattice Hamiltonians and molecular systems. In the present work, the formalism is extended to the ab initio description of infinite systems. An appropriate definition of the impurity Hamiltonian for such systems is presented and demonstrated in cases of 1, 2, and 3 dimensions, using coupled cluster theory as the impurity solver. Additionally, we discuss the challenges related to disentanglement of fragment and bath states. The current approach yields results comparable to coupled cluster calculations of infinite systems even when using a single unit cell as the fragment. The theory is formulated in the basis of Wannier functions but it does not require separate localization of unoccupied bands. The embedding scheme presented here is a promising way of employing highly accurate electronic structure methods for extended systems at a fraction of their original computational cost.

  14. Relative electron density determination using a physics based parameterization of photon interactions in medical DECT

    NASA Astrophysics Data System (ADS)

    van Abbema, Joanne K.; van Goethem, Marc-Jan; Greuter, Marcel J. W.; van der Schaaf, Arjen; Brandenburg, Sytze; van der Graaf, Emiel R.

    2015-05-01

    Radiotherapy and particle therapy treatment planning require accurate knowledge of the electron density and elemental composition of the tissues in the beam path to predict the local dose deposition. We describe a method for the analysis of dual energy computed tomography (DECT) images that provides the electron densities and effective atomic numbers of tissues. The CT measurement process is modelled by system weighting functions, which apply an energy dependent weighting to the parameterization of the total cross section for photon interactions with matter. This detailed parameterization is based on the theoretical analysis of Jackson and Hawkes and deviates, at most, 0.3% from the tabulated NIST values for the elements H to Zn. To account for beam hardening in the object as present in the CT image we implemented an iterative process employing a local weighting function, derived from the method proposed by Heismann and Balda. With this method effective atomic numbers between 1 and 30 can be determined. The method has been experimentally validated on a commercially available tissue characterization phantom with 16 inserts made of tissue substitutes and aluminium that has been scanned on a dual source CT system with tube potentials of 100 kV and 140 kV using a clinical scan protocol. Relative electron densities of all tissue substitutes have been determined with accuracy better than 1%. The presented DECT analysis method thus provides high accuracy electron densities and effective atomic numbers for radiotherapy and especially particle therapy treatment planning.

  15. Relative electron density determination using a physics based parameterization of photon interactions in medical DECT.

    PubMed

    van Abbema, Joanne K; van Goethem, Marc-Jan; Greuter, Marcel J W; van der Schaaf, Arjen; Brandenburg, Sytze; van der Graaf, Emiel R

    2015-05-07

    Radiotherapy and particle therapy treatment planning require accurate knowledge of the electron density and elemental composition of the tissues in the beam path to predict the local dose deposition. We describe a method for the analysis of dual energy computed tomography (DECT) images that provides the electron densities and effective atomic numbers of tissues. The CT measurement process is modelled by system weighting functions, which apply an energy dependent weighting to the parameterization of the total cross section for photon interactions with matter. This detailed parameterization is based on the theoretical analysis of Jackson and Hawkes and deviates, at most, 0.3% from the tabulated NIST values for the elements H to Zn. To account for beam hardening in the object as present in the CT image we implemented an iterative process employing a local weighting function, derived from the method proposed by Heismann and Balda. With this method effective atomic numbers between 1 and 30 can be determined. The method has been experimentally validated on a commercially available tissue characterization phantom with 16 inserts made of tissue substitutes and aluminium that has been scanned on a dual source CT system with tube potentials of 100 kV and 140 kV using a clinical scan protocol. Relative electron densities of all tissue substitutes have been determined with accuracy better than 1%. The presented DECT analysis method thus provides high accuracy electron densities and effective atomic numbers for radiotherapy and especially particle therapy treatment planning.

  16. Control of neural stem cell adhesion and density by an electronic polymer surface switch.

    PubMed

    Saltó, Carmen; Saindon, Emilien; Bolin, Maria; Kanciurzewska, Anna; Fahlman, Mats; Jager, Edwin W H; Tengvall, Pentti; Arenas, Ernest; Berggren, Magnus

    2008-12-16

    Adhesion is an essential parameter for stem cells. It regulates the overall cell density along the carrying surface, which further dictates the differentiation scheme of stem cells toward a more matured and specified population as well as tissue. Electronic control of the seeding density of neural stem cells (c17.2) is here reported. Thin electrode films of poly(3,4-ethylenedioxythiophene) (PEDOT):Tosylate were manufactured along the floor of cell growth dishes. As the oxidation state of the conjugated polymer electrodes was controlled, the seeding density could be varied by a factor of 2. Along the oxidized PEDOT:Tosylate-electrodes, a relatively lower density of, and less tightly bonded, human serum albumin (HSA) was observed as compared to reduced electrodes. We found that this favors adhesion of the specific stem cells studied. Surface analysis experiments, such as photoelectron spectroscopy, and water contact angle measurements, were carried out to investigate the mechanisms responsible for the electronic control of the seeding density of the c17.2 neural stem cells. Further, our findings may provide an opening for electronic control of stem cell differentiation.

  17. Comparison of measured and modelled negative hydrogen ion densities at the ECR-discharge HOMER

    NASA Astrophysics Data System (ADS)

    Rauner, D.; Kurutz, U.; Fantz, U.

    2015-04-01

    As the negative hydrogen ion density nH- is a key parameter for the investigation of negative ion sources, its diagnostic quantification is essential in source development and operation as well as for fundamental research. By utilizing the photodetachment process of negative ions, generally two different diagnostic methods can be applied: via laser photodetachment, the density of negative ions is measured locally, but only relatively to the electron density. To obtain absolute densities, the electron density has to be measured additionally, which induces further uncertainties. Via cavity ring-down spectroscopy (CRDS), the absolute density of H- is measured directly, however LOS-averaged over the plasma length. At the ECR-discharge HOMER, where H- is produced in the plasma volume, laser photodetachment is applied as the standard method to measure nH-. The additional application of CRDS provides the possibility to directly obtain absolute values of nH-, thereby successfully bench-marking the laser photodetachment system as both diagnostics are in good agreement. In the investigated pressure range from 0.3 to 3 Pa, the measured negative hydrogen ion density shows a maximum at 1 to 1.5 Pa and an approximately linear response to increasing input microwave powers from 200 up to 500 W. Additionally, the volume production of negative ions is 0-dimensionally modelled by balancing H- production and destruction processes. The modelled densities are adapted to the absolute measurements of nH- via CRDS, allowing to identify collisions of H- with hydrogen atoms (associative and non-associative detachment) to be the dominant loss process of H- in the plasma volume at HOMER. Furthermore, the characteristic peak of nH- observed at 1 to 1.5 Pa is identified to be caused by a comparable behaviour of the electron density with varying pressure, as ne determines the volume production rate via dissociative electron attachment to vibrationally excited hydrogen molecules.

  18. Attenuated retroreflectors for electronic distance measurement

    NASA Astrophysics Data System (ADS)

    Parker, David H.; Goldman, Michael A.; Radcliff, Bill; Shelton, John W.

    Methods are described for attenuating solid glass and hollow retroreflectors, without introducing optical path length modifications, for electronic distance measurement. Construction of a prototype novel-design hollow retroreflector is described.

  19. Measuring the Plasma Density of a Ferroelectric Plasma Source in an Expanding Plasma

    SciTech Connect

    A. Dunaevsky; N.J. Fisch

    2003-10-02

    The initial density and electron temperature at the surface of a ferroelectric plasma source were deduced from floating probe measurements in an expanding plasma. The method exploits negative charging of the floating probe capacitance by fast flows before the expanding plasma reaches the probe. The temporal profiles of the plasma density can be obtained from the voltage traces of the discharge of the charged probe capacitance by the ion current from the expanding plasma. The temporal profiles of the plasma density, at two different distances from the surface of the ferroelectric plasma source, could be further fitted by using the density profiles for the expanding plasma. This gives the initial values of the plasma density and electron temperature at the surface. The method could be useful for any pulsed discharge, which is accompanied by considerable electromagnetic noise, if the initial plasma parameters might be deduced from measurements in expanding plasma.

  20. Electronic Structure and Effectively Unpaired Electron Density Topology in closo-Boranes: Nonclassical Three-Center Two-Electron Bonding.

    PubMed

    Lobayan, Rosana M; Bochicchio, Roberto C; Torre, Alicia; Lain, Luis

    2011-04-12

    This article provides a detailed study of the structure and bonding in closo-borane cluster compounds X2B3H3 (X = BH(-), P, SiH, CH, N), with particular emphasis on the description of the electron distribution using the topology of the quantum many-body effectively unpaired density. The close relationship observed between the critical points of this quantity and the localization of the electron cloud allows us to characterize the nonclassical bonding patterns of these systems. The obtained results confirm the suitability of the local rule to detect three-center two-electron bonds, which was conjectured in our previous study on boron hydrides.

  1. First test of BNL electron beam ion source with high current density electron beam

    SciTech Connect

    Pikin, Alexander Alessi, James G. Beebe, Edward N.; Shornikov, Andrey; Mertzig, Robert; Wenander, Fredrik; Scrivens, Richard

    2015-01-09

    A new electron gun with electrostatic compression has been installed at the Electron Beam Ion Source (EBIS) Test Stand at BNL. This is a collaborative effort by BNL and CERN teams with a common goal to study an EBIS with electron beam current up to 10 A, current density up to 10,000 A/cm{sup 2} and energy more than 50 keV. Intensive and pure beams of heavy highly charged ions with mass-to-charge ratio < 4.5 are requested by many heavy ion research facilities including NASA Space Radiation Laboratory (NSRL) at BNL and HIE-ISOLDE at CERN. With a multiampere electron gun, the EBIS should be capable of delivering highly charged ions for both RHIC facility applications at BNL and for ISOLDE experiments at CERN. Details of the electron gun simulations and design, and the Test EBIS electrostatic and magnetostatic structures with the new electron gun are presented. The experimental results of the electron beam transmission are given.

  2. First test of BNL electron beam ion source with high current density electron beam

    NASA Astrophysics Data System (ADS)

    Pikin, Alexander; Alessi, James G.; Beebe, Edward N.; Shornikov, Andrey; Mertzig, Robert; Wenander, Fredrik; Scrivens, Richard

    2015-01-01

    A new electron gun with electrostatic compression has been installed at the Electron Beam Ion Source (EBIS) Test Stand at BNL. This is a collaborative effort by BNL and CERN teams with a common goal to study an EBIS with electron beam current up to 10 A, current density up to 10,000 A/cm2 and energy more than 50 keV. Intensive and pure beams of heavy highly charged ions with mass-to-charge ratio < 4.5 are requested by many heavy ion research facilities including NASA Space Radiation Laboratory (NSRL) at BNL and HIE-ISOLDE at CERN. With a multiampere electron gun, the EBIS should be capable of delivering highly charged ions for both RHIC facility applications at BNL and for ISOLDE experiments at CERN. Details of the electron gun simulations and design, and the Test EBIS electrostatic and magnetostatic structures with the new electron gun are presented. The experimental results of the electron beam transmission are given.

  3. Measurements of parallel electron velocity distributions using whistler wave absorption

    SciTech Connect

    Thuecks, D. J.; Skiff, F.; Kletzing, C. A.

    2012-08-15

    We describe a diagnostic to measure the parallel electron velocity distribution in a magnetized plasma that is overdense ({omega}{sub pe} > {omega}{sub ce}). This technique utilizes resonant absorption of whistler waves by electrons with velocities parallel to a background magnetic field. The whistler waves were launched and received by a pair of dipole antennas immersed in a cylindrical discharge plasma at two positions along an axial background magnetic field. The whistler wave frequency was swept from somewhat below and up to the electron cyclotron frequency {omega}{sub ce}. As the frequency was swept, the wave was resonantly absorbed by the part of the electron phase space density which was Doppler shifted into resonance according to the relation {omega}-k{sub ||v||} = {omega}{sub ce}. The measured absorption is directly related to the reduced parallel electron distribution function integrated along the wave trajectory. The background theory and initial results from this diagnostic are presented here. Though this diagnostic is best suited to detect tail populations of the parallel electron distribution function, these first results show that this diagnostic is also rather successful in measuring the bulk plasma density and temperature both during the plasma discharge and into the afterglow.

  4. The quasirelativistic contact interaction and effective electron and spin densities at the nucleus: A model based on weighting the electron density with the finite Gaussian nucleus model

    NASA Astrophysics Data System (ADS)

    Malček, Michal; Bučinský, Lukáš; Biskupič, Stanislav; Jayatilaka, Dylan

    2013-08-01

    The Infinite Order Two Component quasirelativistic Hartree-Fock contact and effective electron/spin densities of Cu, Ag, Au atoms and the chemical shifts of HgF2, Cu+, Ag+ and Au+ are presented. The effective densities for the Gaussian nucleus model based on the weighted product of electron/spin density with the Gaussian distribution of the nucleus are reported for the first time. The effective (average) electron density obtained via the derivative of the energy of the system with respect to the size of the nucleus is shown for comparison. The finite-field difference method to obtain the derivative of the energy is also considered.

  5. Vanishing quasiparticle density in a hybrid Al/Cu/Al single-electron transistor

    NASA Astrophysics Data System (ADS)

    Saira, O.-P.; Kemppinen, A.; Maisi, V. F.; Pekola, J. P.

    2012-01-01

    The achievable fidelity of many nanoelectronic devices based on superconducting aluminum is limited by either the density of residual nonequilibrium quasiparticles nqp or the density of quasiparticle states in the gap, characterized by Dynes parameter γ. We infer upper bounds nqp<0.033μm-3 and γ<1.6×10-7 from transport measurements performed on Al/Cu/Al single-electron transistors, improving previous results by an order of magnitude. Owing to efficient microwave shielding and quasiparticle relaxation, a typical number of quasiparticles in the superconducting leads is zero.

  6. Density matrix calculations of gaseous and adsorbate dynamics in electronically excited molecular systems

    NASA Astrophysics Data System (ADS)

    Micha, David A.

    This contribution deals with two approaches for localized phenomena in excited many-atom systems. The first approach develops a quantum quasi-classical treatment for the density operator, including all atoms. It is based on a partial Wigner representation and is illustrated with applications to photodissociation of NaI, and to light emission of excited Li interacting with a He cluster. This second application describes the direct dynamics with a time-dependent electronic density matrix, expanded in a basis set of atomic functions. It shows that such an approach can deal with electronically excited many-atom systems involving tens of quantum states and hundreds of classical variables. The second approach makes use of the reduced density operator description for a system in a medium. This allows for dissipative dynamics, which can be instantaneous or delayed. An application is presented for femtosecond photodesorption using a Markovian dissipation and construction of the density operator from density amplitudes, for CO/Cu(001). A second application of a reduced density operator has been made to vibrational relaxation of adsorbates, solving integrodifferential equations to compare delayed, instantaneous, and Markovian dissipation. It is concluded that delayed dissipation is needed at short times and that a Markovian treatment is suitable for the interpretation of cross-sectional measurements that involve long-term dynamics.

  7. Rocket observations of electron-density irregularities in the equatorial ionosphere below 200 km

    NASA Technical Reports Server (NTRS)

    Klaus, D. E.; Smith, L. G.

    1978-01-01

    Nike Apache rockets carring instrumentation to measure electron density and its fine structure in the equatorial ionosphere were launched from Chilca, Peru in May and June 1975. The fine structure experiment and the data reduction system are described. Results obtained from this system are presented and compared with those obtained by VHF radar and from other rocket studies. A description of the equatorial ionosphere and its features is also presented.

  8. Contemporary X-ray electron-density studies using synchrotron radiation

    PubMed Central

    Jørgensen, Mads R. V.; Hathwar, Venkatesha R.; Bindzus, Niels; Wahlberg, Nanna; Chen, Yu-Sheng; Overgaard, Jacob; Iversen, Bo B.

    2014-01-01

    Synchrotron radiation has many compelling advantages over conventional radiation sources in the measurement of accurate Bragg diffraction data. The variable photon energy and much higher flux may help to minimize critical systematic effects such as absorption, extinction and anomalous scattering. Based on a survey of selected published results from the last decade, the benefits of using synchrotron radiation in the determination of X-ray electron densities are discussed, and possible future directions of this field are examined. PMID:25295169

  9. Non-invasive fluid density and viscosity measurement

    DOEpatents

    Sinha, Dipen N [Los Alamos, NM

    2012-05-01

    The noninvasively measurement of the density and viscosity of static or flowing fluids in a section of pipe such that the pipe performs as the sensing apparatus, is described. Measurement of a suitable structural vibration resonance frequency of the pipe and the width of this resonance permits the density and viscosity to be determined, respectively. The viscosity may also be measured by monitoring the decay in time of a vibration resonance in the pipe.

  10. Measuring electron temperature in the extended corona

    NASA Technical Reports Server (NTRS)

    Hassler, Donald M.; Gardner, L. D.; Kohl, John L.

    1992-01-01

    A technique for measuring electron temperature in the extended corona from the line profile of the electron scattered component of coronal H I Ly alpha produced by Thomson scattering of chromospheric Ly alpha emission is discussed. Because of the high thermal velocity of electrons at coronal temperatures (approximately 6800 km/s at T(sub e) = 1,500,000 K) the effect of nonthermal velocities and solar wind flows on the electron velocity distribution are negligible. However, the low electron mass which is responsible for the high thermal velocity also results in a very wide profile (approximately equal to 50 A). This wide profile, together with an intensity that is three orders of magnitude weaker than the resonantly scattered component of Ly alpha makes the direct measurement of T(sub e) a challenging observational problem. An evaluation of this technique based on simulated measurements is presented and the subsequent instrumental requirements necessary to make a meaningful determination of the electron temperature are discussed. Estimates of uncertainties in the measured electron temperature are related to critical instrument parameters such as grating stray light suppression.

  11. Rocket experiments for spectral estimation of electron density fine structure in the auroral and equatorial ionosphere and preliminary results

    NASA Technical Reports Server (NTRS)

    Tomei, B. A.; Smith, L. G.

    1986-01-01

    Sounding rockets equipped to monitor electron density and its fine structure were launched into the auroral and equatorial ionosphere in 1980 and 1983, respectively. The measurement electronics are based on the Langmuir probe and are described in detail. An approach to the spectral analysis of the density irregularities is addressed and a software algorithm implementing the approach is given. Preliminary results of the analysis are presented.

  12. Measured acoustic properties of variable and low density bulk absorbers

    NASA Technical Reports Server (NTRS)

    Dahl, M. D.; Rice, E. J.

    1985-01-01

    Experimental data were taken to determine the acoustic absorbing properties of uniform low density and layered variable density samples using a bulk absober with a perforated plate facing to hold the material in place. In the layered variable density case, the bulk absorber was packed such that the lowest density layer began at the surface of the sample and progressed to higher density layers deeper inside. The samples were placed in a rectangular duct and measurements were taken using the two microphone method. The data were used to calculate specific acoustic impedances and normal incidence absorption coefficients. Results showed that for uniform density samples the absorption coefficient at low frequencies decreased with increasing density and resonances occurred in the absorption coefficient curve at lower densities. These results were confirmed by a model for uniform density bulk absorbers. Results from layered variable density samples showed that low frequency absorption was the highest when the lowest density possible was packed in the first layer near the exposed surface. The layers of increasing density within the sample had the effect of damping the resonances.

  13. Paramagnetic ionic liquids for measurements of density using magnetic levitation.

    PubMed

    Bwambok, David K; Thuo, Martin M; Atkinson, Manza B J; Mirica, Katherine A; Shapiro, Nathan D; Whitesides, George M

    2013-09-03

    Paramagnetic ionic liquids (PILs) provide new capabilities to measurements of density using magnetic levitation (MagLev). In a typical measurement, a diamagnetic object of unknown density is placed in a container containing a PIL. The container is placed between two magnets (typically NdFeB, oriented with like poles facing). The density of the diamagnetic object can be determined by measuring its position in the magnetic field along the vertical axis (levitation height, h), either as an absolute value or relative to internal standards of known density. For density measurements by MagLev, PILs have three advantages over solutions of paramagnetic salts in aqueous or organic solutions: (i) negligible vapor pressures; (ii) low melting points; (iii) high thermal stabilities. In addition, the densities, magnetic susceptibilities, glass transition temperatures, thermal decomposition temperatures, viscosities, and hydrophobicities of PILs can be tuned over broad ranges by choosing the cation-anion pair. The low melting points and high thermal stabilities of PILs provide large liquidus windows for density measurements. This paper demonstrates applications and advantages of PILs in density-based analyses using MagLev.

  14. Evidence of water molecules--a statistical evaluation of water molecules based on electron density.

    PubMed

    Nittinger, Eva; Schneider, Nadine; Lange, Gudrun; Rarey, Matthias

    2015-04-27

    Water molecules play important roles in many biological processes, especially when mediating protein-ligand interactions. Dehydration and the hydrophobic effect are of central importance for estimating binding affinities. Due to the specific geometric characteristics of hydrogen bond functions of water molecules, meaning two acceptor and two donor functions in a tetrahedral arrangement, they have to be modeled accurately. Despite many attempts in the past years, accurate prediction of water molecules-structurally as well as energetically-remains a grand challenge. One reason is certainly the lack of experimental data, since energetic contributions of water molecules can only be measured indirectly. However, on the structural side, the electron density clearly shows the positions of stable water molecules. This information has the potential to improve models on water structure and energy in proteins and protein interfaces. On the basis of a high-resolution subset of the Protein Data Bank, we have conducted an extensive statistical analysis of 2.3 million water molecules, discriminating those water molecules that are well resolved and those without much evidence of electron density. In order to perform this classification, we introduce a new measurement of electron density around an individual atom enabling the automatic quantification of experimental support. On the basis of this measurement, we present an analysis of water molecules with a detailed profile of geometric and structural features. This data, which is freely available, can be applied to not only modeling and validation of new water models in structural biology but also in molecular design.

  15. Electron and Negative Ion Densities in C(2)F(6) and CHF(3) Containing Inductively Coupled Discharges

    SciTech Connect

    HEBNER,GREGORY A.; MILLER,PAUL A.

    1999-12-07

    Electron and negative ion densities have been measured in inductively coupled discharges containing C{sub 2}F{sub 6} and CHF{sub 3}. Line integrated electron density was determined using a microwave interferometer, negative ion densities were inferred using laser photodetachment spectroscopy, and electron temperature was determined using a Langmuir probe. For the range of induction powers, pressures and bias power investigated, the electron density peaked at 9 x 10{sup 12} cm{sup -2} (line-integrated) or approximately 9 x 10{sup 11} cm{sup -3}. The negative ion density peaked at approximately 1.3 x 10{sup 11} cm{sup -3}. A maximum in the negative ion density as a function of induction coil power was observed. The maximum is attributed to a power dependent change in the density of one or more of the potential negative ion precursor species since the electron temperature did not depend strongly on power. The variation of photodetachment with laser wavelength indicated that the dominant negative ion was F{sup -}. Measurement of the decay of the negative ion density in the afterglow of a pulse modulated discharge was used to determine the ion-ion recombination rate for CF{sub 4}, C{sub 2}F{sub 6} and CHF{sub 3} discharges.

  16. Matched dipole probe for magnetized low electron density laboratory plasma diagnostics

    SciTech Connect

    Rafalskyi, Dmytro; Aanesland, Ane

    2015-07-15

    In this paper, a diagnostic method for magnetized and unmagnetized laboratory plasma is proposed, based on impedance measurements of a short matched dipole. The range of the measured electron densities is limited to low density plasmas (10{sup 12}–10{sup 15 }m{sup −3}), where other diagnostic methods have strong limitations on the magnetic field strength and topology, plasma dimensions, and boundary conditions. The method is designed for use in both large- and small-dimension plasma (<10 cm) without or with strong non-homogeneous magnetic field, which can be undefined within the probe size. The design of a matched dipole probe allows to suppress the sheath resonance effects and to reach high sensitivity at relatively small probe dimensions. Validation experiments are conducted in both magnetized (B ∼ 170 G) and unmagnetized (B = 0) low density (7 × 10{sup 12 }m{sup −3}–7 × 10{sup 13 }m{sup −3}) low pressure (1 mTorr) 10 cm scale plasmas. The experimentally measured data show very good agreement with an analytical theory both for a non-magnetized and a magnetized case. The electron density measured by the matched dipole and Langmuir probes in the range of 7 × 10{sup 12 }m{sup −3}–7 × 10{sup 13 }m{sup −3} show less than 30% difference. An experimentally measured tolerance/uncertainty of the dipole probe method is estimated to ±1% for plasma densities above 2 × 10{sup 13 }m{sup −3}. A spatial resolution is estimated from the experiments to be about 3d, where d is the dipole diameter. The diagnostic method is also validated by comparing the measured plasma impedance curves with results of analytical modelling.

  17. Pauling bond strength, bond length and electron density distribution

    SciTech Connect

    Gibbs, Gerald V.; Ross, Nancy L.; Cox, David F.; Rosso, Kevin M.; Iversen, Bo B.; Spackman, M. A.

    2014-01-18

    A power law regression equation, = 1.46(<ρ(rc)>/r)-0.19, connecting the average experimental bond lengths, , with the average accumulation of the electron density at the bond critical point, <ρ(rc)>, between bonded metal M and oxygen atoms, determined at ambient conditions for oxide crystals, where r is the row number of the M atom, is similar to the regression equation R(M-O) = 1.39(ρ(rc)/r)-0.21 determined for three perovskite crystals for pressures as high as 80 GPa. The two equations are also comparable with those, = 1.43(/r)-0.21, determined for a large number of oxide crystals at ambient conditions and = 1.39(/r)-0.22, determined for geometry optimized hydroxyacid molecules, that connect the bond lengths to the average Pauling electrostatic bond strength, , for the M-O bonded interactions. On the basis of the correspondence between the two sets of equations connecting ρ(rc) and the Pauling bond strength s with bond length, it appears that Pauling’s simple definition of bond strength closely mimics the accumulation of the electron density between bonded pairs of atoms. The similarity of the expressions for the crystals and molecules is compelling evidence that the M-O bonded interactions for the crystals and molecules 2 containing the same bonded interactions are comparable. Similar expressions, connecting bond lengths and bond strength, have also been found to hold for fluoride, nitride and sulfide molecules and crystals. The Brown-Shannon bond valence, σ, power law expression σ = [R1/(R(M-O)]N that has found wide use in crystal chemistry, is shown to be connected to a more universal expression determined for oxides and the perovskites, <ρ(rc)> = r[(1.41)/]4.76, demonstrating that the bond valence for a bonded interaction is likewise closely connected to the accumulation of the electron density between the bonded atoms. Unlike the Brown-Shannon expression, it is universal in that it holds for the M

  18. Magnesium: Comparison of density functional theory calculations with electron and x-ray diffraction experiments

    NASA Astrophysics Data System (ADS)

    Friis, J.; Madsen, G. K. H.; Larsen, F. K.; Jiang, B.; Marthinsen, K.; Holmestad, R.

    2003-12-01

    Accurate experimental structure factors for Mg have been measured and compared with density functional theory (DFT) to test some commonly used functionals and self-interaction correction (SIC) schemes. Low order structure factors, free of extinction and on absolute scale, were measured accurately by quantitative convergent beam electron diffraction. In addition, a complete set of structure factors up to sin θ/λ=1.6 Å-1 was measured by x-ray diffraction at 10 K. The DFT calculations were performed using the full potential linearized augmented plane wave method. It was found that the agreement with experiment increases when going from the local density approximation (LDA) to the generalized gradient approximation (GGA) of Perdew, Burke, and Ernzerhofer and further to the GGA of Engel and Vosko. Applying the SIC of Perdew and Zunger to the core states for LDA does not improve the agreement with theory, while applying the SIC of Lundin and Eriksson results in a significantly improved agreement. This implies that the main source of error in the LDA functional comes from the description of the core densities. Using the functional which agrees best with experiment, a non-nuclear maximum is established in the calculated electron density of beryllium but not of magnesium.

  19. Electron density and collision frequency of microwave resonant cavity produced discharges. [Progress report

    SciTech Connect

    McColl, W.; Brooks, C.; Brake, M.L.

    1992-12-31

    This progress report consists of an article, the abstract of which follows, and apparently the references and vita from a proposal. A review of perturbation diagnostics applied to microwave resonant cavity discharges is presented. The classical microwave perturbation technique examines the shift in the resonant frequency and cavity quality factor of the resonant cavity caused by low electron density discharges. However, modifications presented here allow the analysis to be applied to discharges with electron densities beyond the limit predicted by perturbation theory. An {open_quote}exact{close_quote} perturbation analysis is presented which models the discharge as a separate dielectric, thereby removing the restrictions on electron density imposed by the classical technique. The {open_quote}exact{close_quote} method also uses measurements of the shifts in the resonant conditions of the cavity. Thirdly, an electromagnetic analysis is presented which uses a characteristic equation, based upon Maxwell`s laws, and predicts the discharge conductivity based upon measurements of a complex axial wave number. By allowing the axial wave number of the electromagnetic fields to be complex, the fields are experimentally and theoretically shown to be spatially attenuated. The diagnostics are applied to continuous-wave microwave (2.45 GHz) discharges produced in an Asmussen resonant cavity. Double Langmuir probes, placed directly in the discharge at the point where the radial electric field is zero, act as a comparison with the analytic diagnostics. Microwave powers ranging from 30 to 100 watts produce helium and nitrogen discharges with pressures ranging from 0.5 to 6 torr. Analysis of the data predicts electron temperatures from 5 to 20 eV, electron densities from 10{sup 11} to 3 {times} 10{sup 12} cm{sup {minus}3}, and collision frequencies from 10{sup 9} to 10{sup 11} sec{sup {minus}1}.

  20. Electron cyclotron emission measurements on the Texas Experimental Tokamak

    SciTech Connect

    Austin, M.E. Jr.

    1992-01-01

    A ten-channel grating polychromator was designed, constructed, and installed on the Texas Experimental Tokamak to monitor the second harmonic electron cyclotron emission. Electron temperature profiles were derived from measurements of the optically thick radiation for a variety of plasma confinement experiments. The radial and temporal evolution of T[sub e] has been characterized for electron cyclotron heated discharges with 150 kW of 60 GHz power. Comparisons were made of the heating efficiency of two type of ECH launchers. A focussed launcher was shown to have slightly better heating efficiency than an unfocussed launcher; however, the focussed antenna did not yield significantly higher electron temperatures as expected. A study of the time evolution of the electron temperature indicated that increased sawtooth activity limited the effectiveness of the focussed launcher. A focussing hog-horn antenna was fabricated and installed on the inboard side of the tokamak to measure emission directed towards the high-field side during ECH. Comparison of the radiation temperature profiles from low-field side and high-field side antennas indicates the creation of a nonthermal electron distribution by the heating. The results of the experiment compare favorably with theoretical predictions from a quasi-linear Fokker-Planck code of a 6 keV nonthermal population with a density about 1 percent of the thermal density.

  1. Alkali-metal electron spin density shift induced by a helium nanodroplet

    NASA Astrophysics Data System (ADS)

    Koch, Markus; Callegari, Carlo; Ernst, Wolfgang E.

    2010-04-01

    Helium (He) nanodroplets provide a cold and virtually unperturbing environment for the study of weakly bound molecules and van der Waals aggregates. High resolution microwave spectroscopy and the detection of electron spin transitions in doped He droplets have recently become possible. Measurements of hyperfine-resolved electron spin resonance in potassium (39K) and rubidium (85Rb) atoms on the surface of He droplets show small line shifts relative to the bare atoms. These shifts were recorded for all 2I + 1 components (I is the nuclear spin) of a transition at high accuracy for He droplets ranging in size from 1000 to 15,000 He atoms. Evaluation of the spectra yields the influence of the He environment on the electron spin density at the alkali-metal nucleus. A semi-empirical model is presented that shows good qualitative agreement with the measured droplet size dependent increase of Fermi contact interaction at the nuclei of dopant K and Rb.

  2. Investigation of Electron Density Profile in the ionospheric D and E region by Kagoshima rocket experiment

    NASA Astrophysics Data System (ADS)

    Ashihara, Y.; Ishisaka, K.; Miyake, T.; Okada, T.; Nagano, I.; Abe, T.; Ono, T.

    2007-12-01

    The radio wave propagation characteristic in the lower ionosphere is important because of its effect on commercial radio communication, navigation, and broadcast services. The electron density is of primary interest in this region because the high ion-neutral collision frequencies result in radio wave absorption. In order to investigate the ionization structure in the ionospheric D and E region by using the propagation characteristics of MF-band and LF-band radio waves, S-310-37 and S-520-23 sounding rocket experiments have been carried out at Uchinoura Space Center (USC). S-310-37 sounding rocket was launched at 11:20 LT on January 16, 2007. The apex of rocket trajectory was about 138 km. Then S-520-23 sounding rocket was launched at 19:20 LT on September 2, 2007. The apex was about 279 km. As a common measurement, these sounding rockets measure the fields intensities and the waveform of radio waves from NHK Kumamoto broadcasting station (873kHz, 500kW) and JJY signals from Haganeyama LF radio station (60kHz, 50kW). The approximate electron density profile can be determined from the comparison between these experimental results and propagation characteristics calculated by the full wave method. We will get the most probable electron density profile in the ionosphere. In presentation, we will show the propagation characteristic of LF/MF radio waves measured by two sounding rocket experiments. Then we will discuss the analysis method and the estimated electron density profile in the ionosphere.

  3. Electron Densities in Solar Flare Loops, Chromospheric Evaporation Upflows, and Acceleration Sites

    NASA Technical Reports Server (NTRS)

    Aschwanden, Markus J.; Benz, Arnold O.

    1996-01-01

    We compare electron densities measured at three different locations in solar flares: (1) in Soft X-Ray (SXR) loops, determined from SXR emission measures and loop diameters from Yohkoh Soft X-Ray Telescope maps (n(sub e, sup SXR) = (0.2-2.5) x 10(exp 11)/ cu cm); (2) in chromospheric evaporation upflows, inferred from plasma frequency cutoffs of decimetric radio bursts detected with the 0.1-3 GHz spectrometer Phoenix of ETH Zuerich (n(sub e, sup upflow) = (0.3-11) x 10(exp 10)/cu cm; and (3) in acceleration sites, inferred from the plasma frequency at the separatrix between upward-accelerated (type III bursts) and downward-accelerated (reverse-drift bursts) electron beams [n(sub e, sup acc) = (0.6-10) x 10(exp 9)/cu cm]. The comparison of these density measurements, obtained from 44 flare episodes (during 14 different flares), demonstrates the compatibility of flare plasma density diagnostics with SXR and radio methods. The density in the upflowing plasma is found to be somewhat lower than in the filled loops, having ratios in a range n(sub e, sup upflow)/n(sub e, sup SXR) = 0.02-1.3, and a factor of 3.6 higher behind the upflow front. The acceleration sites are found to have a much lower density than the SXR-bright flare loops, i.e., n(sub e, sup acc)/n(sub e, sup SXR) = 0.005- 0.13, and thus must be physically displaced from the SXR-bright flare loops. The scaling law between electron time-of-flight distances l' and loop half-lengths s, l'/s = 1.4 +/- 0.3, recently established by Aschwanden et al. suggests that the centroid of the acceleration region is located above the SXR-bright flare loop, as envisioned in cusp geometries (e.g., in magnetic reconnection models).

  4. Evidence for density-gradient-driven trapped-electron modes in improved confinement RFP plasmas

    NASA Astrophysics Data System (ADS)

    Duff, James; Chapman, Brett; Sarff, John; Terry, Paul; Williams, Zach; Ding, Weixing; Brower, David; Parke, Eli

    2015-11-01

    Density fluctuations in the large-density-gradient region of improved-confinement MST RFP plasmas exhibit features characteristic of the trapped-electron-mode (TEM), strong evidence that drift wave turbulence emerges in RFP plasmas when magnetic transport is reduced. In standard RFP plasmas, core transport is governed by magnetic stochasticity stemming from current-driven tearing modes. Using inductive control, these tearing modes are reduced, improving confinement. The improved confinement is associated with substantial increases in the density and temperature gradients, and we present evidence for the onset of drift wave instability. Density fluctuations are measured with a multi-chord, laser-based interferometer. These fluctuations have wavenumbers kϕ *ρs <0.14, frequencies characteristic of drift waves (>50 kHz), and are clearly distinct from residual global tearing modes. Their amplitudes increase with the local density gradient, and require a critical density gradient. Gyrokinetic analysis provides supporting evidence of microinstability in these plasmas, in which the density-gradient-driven TEM is most unstable. The experimental threshold gradient is close to the predicted critical gradient for linear stability. Work supported by DOE.

  5. Paper area density measurement from forward transmitted scattered light

    DOEpatents

    Koo, Jackson C.

    2001-01-01

    A method whereby the average paper fiber area density (weight per unit area) can be directly calculated from the intensity of transmitted, scattered light at two different wavelengths, one being a non-absorpted wavelength. Also, the method makes it possible to derive the water percentage per fiber area density from a two-wavelength measurement. In the optical measuring technique optical transmitted intensity, for example, at 2.1 microns cellulose absorption line is measured and compared with another scattered, optical transmitted intensity reference in the nearby spectrum region, such as 1.68 microns, where there is no absorption. From the ratio of these two intensities, one can calculate the scattering absorption coefficient at 2.1 microns. This absorption coefficient at this wavelength is, then, experimentally correlated to the paper fiber area density. The water percentage per fiber area density can be derived from this two-wavelength measurement approach.

  6. Mars Atmosphere Argon Density Measurement on MER Mission

    NASA Astrophysics Data System (ADS)

    Economou, T. E.

    2008-11-01

    Using the Alpha Particle X-ray Spectrometer (APXS) on board Spirit and Opportunity rovers on MER mission, we were able to measure the argon density variation in the martian atmosphere as a function of seasonal changes.

  7. Ozone density measurements in the troposphere and stratosphere of Natal

    NASA Technical Reports Server (NTRS)

    Kirchhoff, V. W. J. H.; Motta, A. G.

    1983-01-01

    Ozone densitities were measured in the troposphere and stratosphere of Natal using ECC sondes launches on balloons. The data analyzed so far show tropospheric densities and total ozone contents larger than expected.

  8. Rapid density-measurement system with vibrating-tube densimeter

    NASA Astrophysics Data System (ADS)

    Kayukawa, Yohei; Hasumoto, Masaya; Watanabe, Koichi

    2003-09-01

    Concerning an increasing demand for environmentally friendly refrigerants including hydrocarbons, thermodynamic properties of such new refrigerants, especially densities, are essential information for refrigeration engineering. A rapid density-measurement system with vibrating-tube densimeter was developed in the present study with an aim to supply large numbers of high-quality PVT property data in a short period. The present system needs only a few minutes to obtain a single datum, and requires less than 20 cm3 sample fluid. PVT properties in the entire fluid-phase, vapor-pressures, saturated-liquid densities for pure fluid are available. Liquid densities, bubble-point pressures and saturated-liquid densities for mixture can be obtained. The measurement range is from 240 to 380 K for temperature and up to 7 MPa for pressure. By employing a new calibration function, density can be precisely obtained even at lower densities. The densimeter is calibrated with pure water and iso-octane which is one of the density-standard fluids, and then measurement uncertainty was evaluated to be 0.1 kg m-3 or 0.024% whichever greater in density, 0.26 kPa or 0.022% whichever greater in pressure and 3 mK for temperature, respectively. The performance of the present measurement system was examined by measuring thermodynamic properties for refrigerant R134a. The experimental results were compared with available equation of state and confirmed to agree with it within ±0.05% for liquid densities while ±0.5% in pressure for the gas phase.

  9. A basis set convergence study of conventional and HSF electron densities in the Li 2 molecule

    NASA Astrophysics Data System (ADS)

    Challacombe, Matt; Cioslowski, Jerzy

    1994-07-01

    Calculations of nonnuclear, Hartree-Fock HSF and CHSF electron densities are reported for the first time. The positions of critical points in the conventional, HSF, and CHSF electron densities of the Li 2 molecule (including the nonnuclear maximum) and corresponding values of the electron density are computed for a sequence of systematically improved basis sets. The basis set convergence of these topological properties, as well as that of the densities at nuclei, are examined. Quantities derived from HSF and CHSF electron densities are found to converge more rapidly than their conventional counterparts.

  10. Calculated ionization rates, ion densities, and airglow emission rates due to precipitating electrons in the nightside ionosphere of Mars

    NASA Technical Reports Server (NTRS)

    Haider, S. A.; Kim, J.; Nagy, A. F.; Keller, C. N.; Verigin, M. I.; Gringauz, K. I.; Shutte, N. M.; Szego, K.; Kiraly, P.

    1992-01-01

    The calculations presented in this paper clearly establish that the electron fluxes measured by the HARP instrument, carried on board Phobos 2, could cause significant electron impact ionization and excitation in the nightside atmosphere of Mars, if these electrons actually do precipitate. The calculated peak electron densities were found to be about a factor of 2 larger than the mean observed nightside densities, indicating that if a significant fraction of the measured electrons actually precipitate, they could be the dominant mechanism responsible for maintaining the nightside ionosphere. The calculated zenith column emission rates of the O I 5577-A and 6300-A and CO Cameron band emissions, due to electron impact and dissociative recombination mechanisms, were found to be significant.

  11. Density-Gradient-Driven trapped-electron-modes in improved-confinement RFP plasmas

    NASA Astrophysics Data System (ADS)

    Duff, James

    2016-10-01

    Short wavelength density fluctuations in improved-confinement MST plasmas exhibit multiple features characteristic of the trapped-electron-mode (TEM), strong evidence that drift wave turbulence emerges in RFP plasmas when transport associated with MHD tearing is reduced. Core transport in the RFP is normally governed by magnetic stochasticity stemming from long wavelength tearing modes that arise from current profile peaking. Using inductive control, the tearing modes are reduced and global confinement is increased to values expected for a comparable tokamak plasma. The improved confinement is associated with a large increase in the pressure gradient that can destabilize drift waves. The measured density fluctuations have frequencies >50 kHz, wavenumbers k_phi*rho_s<0.14, and propagate in the electron drift direction. Their spectral emergence coincides with a sharp decrease in fluctuations associated with global tearing modes. Their amplitude increases with the local density gradient, and they exhibit a density-gradient threshold at R/L_n 15, higher than in tokamak plasmas by R/a. the GENE code, modified for RFP equilibria, predicts the onset of microinstability for these strong-gradient plasma conditions. The density-gradient-driven TEM is the dominant instability in the region where the measured density fluctuations are largest, and the experimental threshold-gradient is close to the predicted critical gradient for linear stability. While nonlinear analysis shows a large Dimits shift associated with predicted strong zonal flows, the inclusion of residual magnetic fluctuations causes a collapse of the zonal flows and an increase in the predicted transport to a level close to the experimentally measured heat flux. Similar circumstances could occur in the edge region of tokamak plasmas when resonant magnetic perturbations are applied for the control of ELMs. Work supported by US DOE.

  12. Device and method for electron beam heating of a high density plasma

    DOEpatents

    Thode, L.E.

    A device and method for relativistic electron beam heating of a high density plasma in a small localized region are described. A relativistic electron beam generator produces a high voltage electron beam which propagates along a vacuum drift tube and is modulated to initiate electron bunching within the beam. The beam is then directed through a low density gas chamber which provides isolation between the vacuum modulator and the relativistic electron beam target. The relativistic beam is then applied to a high density target plasma which typically comprises DT, DD, hydrogen boron or similar thermonuclear gas at a density of 10/sup 17/ to 10/sup 20/.

  13. Transmission Electron Microscope Measures Lattice Parameters

    NASA Technical Reports Server (NTRS)

    Pike, William T.

    1996-01-01

    Convergent-beam microdiffraction (CBM) in thermionic-emission transmission electron microscope (TEM) is technique for measuring lattice parameters of nanometer-sized specimens of crystalline materials. Lattice parameters determined by use of CBM accurate to within few parts in thousand. Technique developed especially for use in quantifying lattice parameters, and thus strains, in epitaxial mismatched-crystal-lattice multilayer structures in multiple-quantum-well and other advanced semiconductor electronic devices. Ability to determine strains in indivdual layers contributes to understanding of novel electronic behaviors of devices.

  14. Mars Global Surveyor Radio Science Electron Density Profiles: Interannual Variability and Implications for the Neutral Atmosphere

    NASA Technical Reports Server (NTRS)

    Bougher, S. W.; Engel, S.; Hinson, D. P.; Murphy, J. R.

    2003-01-01

    The Mars Global Surveyor (MGS) Radio Science (RS) experiment employs an ultrastable oscillator aboard the spacecraft. The signal from the oscillator to Earth is refracted by the Martian ionosphere, allowing retrieval of electron density profiles versus radius and geopotential. The present analysis is carried out on five sets of occultation measurements: (1) four obtained near northern summer solstice (Ls = 74-116, near aphelion) at high northern latitudes (64.7-77.6N), and (2) one set of profiles approaching equinox conditions (Ls = 135- 146) at high southern latitudes (64.7-69.1S). Electron density profiles (95 to 200 km) are examined over a narrow range of solar zenith angles (76.5-86.9 degrees) for local true solar times of (1) 3-4 hours and (2) 12.1 hours. Variations spanning 1-Martian year are specifically examined in the Northern hemisphere.

  15. High Precision Density Measurements of Single Particles: The Density of Metastable Phases

    SciTech Connect

    Zelenyuk, Alla; Cai, Yong; Chieffo, Logan; Imre, Dan G.

    2005-10-01

    We describe a system designed to measure the size, composition and density of individual particles in real-time. It uses a DMA to select a monodisperse particle population and the single particle mass spectrometer to measure individual particle mass spectrometer to measure individual particle aerodynamic diameter and composition. Mobility and aerodynamic diameters are used to extract particle density. The addition of individual particle density to the mass spectrum is intended to improve the data classification process. In the present paper we demonstrate that the system has the requisite accuracy and resolution to make this approach practicable. We also present a high precision variant that uses an internal calibrant to remove any of the systematic errors and significantly improves the measurement quality. The high precision scheme is most suitable for laboratory studies making it possible to follow slight changes in particle density. An application of the system to measure the density of hygroscopic particles of atmospheric importance in metastable phases near zero relative humidity is presented. The density data are consistent with conclusions reached in a number of other studies that some particle systems of atmospheric significance once deliquesced persist as droplets down to near zero relative humidity.

  16. Ultrasonic Technique for Density Measurement of Liquids in Extreme Conditions

    PubMed Central

    Kazys, Rymantas; Sliteris, Reimondas; Rekuviene, Regina; Zukauskas, Egidijus; Mazeika, Liudas

    2015-01-01

    An ultrasonic technique, invariant to temperature changes, for a density measurement of different liquids under in situ extreme conditions is presented. The influence of geometry and material parameters of the measurement system (transducer, waveguide, matching layer) on measurement accuracy and reliability is analyzed theoretically along with experimental results. The proposed method is based on measurement of the amplitude of the ultrasonic wave, reflected from the interface of the solid/liquid medium under investigation. In order to enhance sensitivity, the use of a quarter wavelength acoustic matching layer is proposed. Therefore, the sensitivity of the measurement system increases significantly. Density measurements quite often must be performed in extreme conditions at high temperature (up to 220 °C) and high pressure. In this case, metal waveguides between piezoelectric transducer and the measured liquid are used in order to protect the conventional transducer from the influence of high temperature and to avoid depolarization. The presented ultrasonic density measurement technique is suitable for density measurement in different materials, including liquids and polymer melts in extreme conditions. A new calibration algorithm was proposed. The metrological evaluation of the measurement method was performed. The expanded measurement uncertainty Uρ = 7.4 × 10−3 g/cm3 (1%). PMID:26262619

  17. High-Density Electron-Beam Recording of Circumferentially Aligned Dots by Using Substrates with Low Atomic Numbers

    NASA Astrophysics Data System (ADS)

    Okada, Takeru; Aida, Makoto; Fujimori, Jiro; Katsumura, Masahiro; Iida, Tetsuya

    2012-01-01

    Reducing proximity effects is a key factor for achieving a higher resolution in electron-beam lithography and realizing the mastering of patterned media. The effect of substrate materials on backscattering electrons was investigated by simulation and experiment, and resolution enhancement was demonstrated. In Monte Carlo simulations with 100 keV incident electrons, the intensity of backscattering electrons decreased with decreasing atomic number of substrates. On the other hand, both the density of substrates and the existence of 10 nm thin films had negligible effects on the intensity of backscattering electrons. The measured exposure distributions from line-scanned electron beams supported the results of simulations. The intensity of backscattering electrons was reduced by using a carbon substrate, and circumferentially aligned high-density patterns of 878 Gbit/in.2 were resolved.

  18. Increasing positive ion number densities below the peak of ion-electron pair production in Titan's ionosphere

    SciTech Connect

    Vigren, E.; Galand, M.; Shebanits, O.; Wahlund, J.-E.; Geppert, W. D.; Lavvas, P.; Vuitton, V.

    2014-05-01

    We combine derived ion-electron pair formation rates with Cassini Radio Plasma Wave Science Langmuir Probe measurements of electron and positive ion number densities in Titan's sunlit ionosphere. We show that positive ion number densities in Titan's sunlit ionosphere can increase toward significantly lower altitudes than the peak of ion-electron pair formation despite that the effective ion-electron recombination coefficient increases. This is explained by the increased mixing ratios of negative ions, which are formed by electron attachment to neutrals. While such a process acts as a sink for free electrons, the positive ions become longer-lived as the rate coefficients for ion-anion neutralization reactions are smaller than those for ion-electron dissociative recombination reactions.

  19. DE/ISIS conjunction comparisons of high-latitude electron density features

    NASA Technical Reports Server (NTRS)

    Hoegy, Walter R.; Benson, Robert F.

    1988-01-01

    This paper presents a comparison between the ISIS-1 and -2 topside sounder measurements of electron number density, N(e), with the in situ ion and N(e) measurements by the Langmuir probe aboard the Dynamics Explorer 2 (DE 2) during four high-latitude ISIS/DE magnetic field-aligned conjunctions. The ISIS-derived N(e) values, even at the greatest distance from the sounder, were found to agree with the Langmuir probe measurements to within about 30 percent over a density range of more than two decades on three of the four comparisons; the fourth comparison which included data with strong N(e) irregularities, showed a difference of 60 percent.

  20. Nonlocal electron kinetics and densities of excited atoms in S and P striations

    PubMed

    Golubovskii; Kozakov; Maiorov; Behnke; Behnke

    2000-08-01

    A numerical solution of the Boltzmann kinetic equation involving elastic and inelastic collisions as well as spatial gradients along the electric field is obtained for the experimentally measured fields in S and P striations. The peculiarities of formation of the distribution function are analyzed. They are connected with the displacements of one distinctive peak in the electron distribution function (EDF) for S striations or two peaks for P striations in accordance with the resonance trajectories. A descriptive model is constructed for the processes of excitation of neon 2p(5)3s and 2p(5)3p atomic states and ionization in striations. The presence of phase shifts between ionization rate and electron density is shown, which can cause ionization wave propagation. Measurements and calculations of the excited state densities are carried out for different striation phases. Comparison of theory and spectroscopic measurements shows a good description of fast electrons by the distribution function in striations. Comparison of theory and probe measurements of the distribution function shows that the main features of the EDF in an energy range below the excitation threshold are experimentally observed.

  1. Enhancement of Mammographic Density Measures in Breast Cancer Risk Prediction

    PubMed Central

    Cheddad, Abbas; Czene, Kamila; Shepherd, John A.; Li, Jingmei; Hall, Per; Humphreys, Keith

    2016-01-01

    Background Mammographic density is a strong risk factor for breast cancer. Methods We present a novel approach to enhance area density measures that takes advantage of the relative density of the pectoral muscle that appears in lateral mammographic views. We hypothesized that the grey scale of film mammograms is normalized to volume breast density but not pectoral density and thus pectoral density becomes an independent marker of volumetric density. Results From analysis of data from a Swedish case–control study (1,286 breast cancer cases and 1,391 control subjects, ages 50–75 years), we found that the mean intensity of the pectoral muscle (MIP) was highly associated with breast cancer risk [per SD: OR = 0.82; 95% confidence interval (CI), 0.75–0.88; P = 6 × 10−7] after adjusting for a validated computer-assisted measure of percent density (PD), Cumulus. The area under curve (AUC) changed from 0.600 to 0.618 due to using PD with the pectoral muscle as reference instead of a standard area-based PD measure. We showed that MIP is associated with a genetic variant known to be associated with mammographic density and breast cancer risk, rs10995190, in a subset of women with genetic data. We further replicated the association between MIP and rs10995190 in an additional cohort of 2,655 breast cancer cases (combined P = 0.0002). Conclusions MIP is a marker of volumetric density that can be used to complement area PD in mammographic density studies and breast cancer risk assessment. Impact Inclusion of MIP in risk models should be considered for studies using area PD from analog films. PMID:24722754

  2. Development of a Lithium Beam Probe and Measurement of Density Pedestal in JT-60U

    NASA Astrophysics Data System (ADS)

    Kojima, Atsushi; Kamiya, Kensaku; Fujita, Takaaki; Kubo, Hirotaka; Iguchi, Harukazu; Oyama, Naoyuki; Suzuki, Takahiro; Kamada, Yutaka; JT-60 Team

    A lithium beam probe (LiBP) has been developed for the measurement of electron density profiles with highly spatial and temporal resolutions in JT-60U. Using an electron beam heating ion source with a capability of 10 mA extraction, a 5.5 mA beam has been injected to the plasmas. It corresponds to the equivalent neutral beam current of 2 mA. A spectrum width of the beam emission has been small enough to separate Zeeman splitting. By use of the LiBP, time evolutions of pedestal density profiles during type I and grassy edge localized modes (ELMs) have been obtained for the first time. After a type I ELM crash, the drop of the line-integrated density measured by an interferometer delays by 2 ms later than that of the pedestal density. Comparing the line-integrated density to the line integration of the edge density profile measured by the LiBP, it is found that the recovery from the type I ELM crash is correlated with the reduction of core plasma density. As for grassy ELMs, grassy ELMs have smaller density crashes than that of type I ELMs, which is mainly derived from the narrower ELM affected area.

  3. Dayside electron density structures organised by the Martian crustal magnetic fields

    NASA Astrophysics Data System (ADS)

    Dieval, C.; Wild, J. A.; Morgan, D. D.; Andrews, D. J.; Gurnett, D. A.

    2015-12-01

    The Advanced Radar for Subsurface and Ionospheric Sounding (MARSIS) onboard Mars Express is able to detect remotely the Martian topside electron densities down to the main ionospheric peak. In the ionospheric mode it transmits a sequence of pulses in the frequency range 0.1 to 5.5 MHz and measures the delay of reception of the reflected signals returned by the ionospheric plasma layers below the spacecraft. Previous studies using MARSIS have investigated localized electron density structures in the dayside Martian ionosphere, located in areas of typically near-vertical or oblique orientation of the Martian crustal magnetic fields. These crustal fields are remnants of the now extinct global Martian dipole magnetic field, with the strongest fields in the Southern hemisphere reaching up to |B| > 200 nT at altitudes of 400 km. These density structures are often detected as apparent upwellings above the surrounding ideally horizontally stratified ionosphere. Previous studies searched the density structures at a fixed sounding frequency of 1.9 MHz (equivalent to a plasma density of 4.47·104 cm-3), which is a typical frequency at which they are detected. In addition, these studies did not account for the signal dispersion due to the propagation through the ionosphere, which causes larger time delays for receiving the radar echoes, and therefore an underestimation of the altitude of these structures. In the present work we propose to use a statistical dataset of such density structures detected on the dayside of Mars by MARSIS in areas of oblique crustal fields, to determine the interval of densities for which the structures are found to make apparent upwellings. Then we use the corresponding electron density profiles corrected for signal dispersion, to determine the real altitudes of the density structures, their vertical extent and their plasma scale heights compared to the surrounding ionosphere. These new informations give critical hints for uncovering their origins

  4. Comparison of density fluctuation measurements between O-mode and X-mode reflectometry on Tore Supra

    SciTech Connect

    Gerbaud, T.; Clairet, F.; Sabot, R.; Sirinelli, A.; Heuraux, S.; Leclert, G.; Vermare, L.

    2006-10-15

    Reflectometry is a versatile diagnostic which allows both electronic density profile and density fluctuation measurements. Fast sweep heterodyne technique is particularly suitable for precise measurement of the phase of the reflected signal, which records the story of the wave propagation through the plasma up to the cutoff layer, including the density fluctuations. The present article exhibits a comparison of the density fluctuation radial profile measurements between fast sweep frequency technique, both using O-mode and X-mode polarizations, and fixed frequency technique. The correct agreement between all measurements of the relative values of the density fluctuation profiles reinforces the validity of the approximations used.

  5. Model simulations of ion and electron density profiles in ionospheric E and F regions

    NASA Astrophysics Data System (ADS)

    Lin, Y. C.; Chu, Y. H.

    2017-02-01

    We develop a time-dependent theoretical numerical model to simulate the density profiles of the ions (i.e., O+(2P), O+(2D), N2+, O+(4S), N+, O2+, and NO+) and free electrons in E and F regions. In this model, the ion photoionization production rates, the photoelectron ionization production effect, and the chemical reactions between the ionized species and the neutral compositions are considered, and the plasma transport processes are not included. The simulation results show that the mean electron density ratios of the model simulations to the AE-C satellite measurements for the Solar Dynamics Observatory-Extreme Ultraviolet Variability Experiment (SDO-EVE), EUV flux model for Aeronomic Calculations, and Hinteregger-Fukui-Gilson solar irradiance models are, respectively, 0.97, 0.79, and 0.71 in a height range 140-400 km and 0.79, 0.75, and 0.64 in a height range 90-150 km. A comparison shows that the electron densities simulated by the model developed in this study are much more consistent with the in situ measurements made by the AE-C satellite than those predicted by the International Reference Ionosphere model and simulated by the Thermosphere Ionosphere Electrodynamics General Circulation Model. The model simulations with SDO-EVE solar irradiance input indicate that the photoelectron impact production process contributes about 20%-30% of the total atomic ion densities throughout the height range 130-400 km around noon. However, the photoelectron production effect on the molecular ion densities is very minor (less than about 7%) above 275 km. Below 250 km, its effect increases with the decrease of height for O2+ and N2+, from about 4% and 10% at 250 km to 13% and 27% at 150 km, respectively.

  6. [Measuring the density of wood and bamboo using computed tomography].

    PubMed

    Peng, Guan-Yun; Jiang, Ze-Hui; Liu, Xing-E; Yu, Yan; Yang, Shu-Min; Deng, Biao; Xiao, Ti-Qiao; Wang, Xiao-Huan

    2012-07-01

    CT is widespread non-destructive detection technique for wood materials, and the density measurement is a key role during this application. In the present report, the use of CT for air-dry density measurement of wood and bamboo is described. The authors found that there were marked linear correlations between air-dry density (0.303-1.061 g x cm(-3)) of 24 kinds of woods and their respective CT value, as well as 25 kinds of lignin materials (including 24 kinds of woods and 1 kind of bamboo) and the CT value, both with correlation coefficient of 0.99, which belonged to the CT technological breakthrough for wood quantitative detection These research results show that CT is an appropriate way to measure density for wood and bamboo, and would provide technical support for CT used in the field of wood science research and wood processing.

  7. Quasi-optical design for systems to diagnose the electron temperature and density fluctuations on EAST.

    PubMed

    Cao, Qifo; Liu, Yong; Zhao, Hailin; Zhou, Tianfu; Ti, Ang; Hu, Liqun

    2016-11-01

    A system to simultaneously diagnose the electron temperature and density fluctuations is proposed for Experimental Advanced Superconducting Tokamak device. This system includes a common quasi-optical antenna, a correlation electron cyclotron emission (CECE) system that is used to measure the electron temperature fluctuations and a Doppler backscattering (DBS) system that is used to measure the electron density fluctuations. The frequency range of the proposed CECE system is 108-120 GHz, and this corresponds to a radial coverage of normalized radius ((R - R0)/a, R0 = 1850 mm, a = 450 mm) from 0.2 to 0.67 for the plasma operation with a toroidal magnetic field of 2.26 T. This paper focuses on the design of the quasi-optical antenna and aims at optimizing the poloidal resolution for different frequency bands. An optimum result gives the beam radius for the CECE system of 13-15 mm and this corresponds to a wave number range of kθ < 2.4 cm(-1). The beam radius is 20-30 mm for V band (50-75 GHz) and 15-20 mm for W band (75-110 GHz).

  8. Quasi-optical design for systems to diagnose the electron temperature and density fluctuations on EAST

    NASA Astrophysics Data System (ADS)

    Cao, Qifo; Liu, Yong; Zhao, Hailin; Zhou, Tianfu; Ti, Ang; Hu, Liqun

    2016-11-01

    A system to simultaneously diagnose the electron temperature and density fluctuations is proposed for Experimental Advanced Superconducting Tokamak device. This system includes a common quasi-optical antenna, a correlation electron cyclotron emission (CECE) system that is used to measure the electron temperature fluctuations and a Doppler backscattering (DBS) system that is used to measure the electron density fluctuations. The frequency range of the proposed CECE system is 108-120 GHz, and this corresponds to a radial coverage of normalized radius ((R - R0)/a, R0 = 1850 mm, a = 450 mm) from 0.2 to 0.67 for the plasma operation with a toroidal magnetic field of 2.26 T. This paper focuses on the design of the quasi-optical antenna and aims at optimizing the poloidal resolution for different frequency bands. An optimum result gives the beam radius for the CECE system of 13-15 mm and this corresponds to a wave number range of kθ < 2.4 cm-1. The beam radius is 20-30 mm for V band (50-75 GHz) and 15-20 mm for W band (75-110 GHz).

  9. A high density two-dimensional electron gas in an oxide heterostructure on Si (001)

    SciTech Connect

    Jin, E. N.; Kornblum, L.; Kumah, D. P.; Zou, K.; Walker, F. J.; Broadbridge, C. C.; Ngai, J. H.; Ahn, C. H.

    2014-11-01

    We present the growth and characterization of layered heterostructures comprised of LaTiO{sub 3} and SrTiO{sub 3} epitaxially grown on Si (001). Magnetotransport measurements show that the sheet carrier densities of the heterostructures scale with the number of LaTiO{sub 3}/SrTiO{sub 3} interfaces, consistent with the presence of an interfacial 2-dimensional electron gas (2DEG) at each interface. Sheet carrier densities of 8.9 × 10{sup 14} cm{sup −2} per interface are observed. Integration of such high density oxide 2DEGs on silicon provides a bridge between the exceptional properties and functionalities of oxide 2DEGs and microelectronic technologies.

  10. Spacecraft radio scattering observations of the power spectrum of electron density fluctuations in the solar wind

    NASA Technical Reports Server (NTRS)

    Woo, R.; Armstrong, J. W.

    1979-01-01

    Solar wind electron density power spectra in the solar equatorial region are inferred from observations of phase scintillations and spectral broadening made with the Viking, Helios, and Pioneer spacecraft. The heliocentric distance range covered is 2-215 solar radii and for some observations close to the sun the spectra extend to fluctuation frequencies as high as 100 Hz. For heliocentric distances of about 20 solar radii the equivalent spacecraft-measured one-dimensional density spectrum is well modeled by a single power law in the frequency range 0.0001-0.05 Hz. The flattening of the density spectrum within 20 solar radii is presumably associated with energy deposition in the near-sun region and acceleration of the solar wind.

  11. Systematic comparison between line integrated densities measured with interferometry and polarimetry at JET

    SciTech Connect

    Brombin, M.; Zilli, E.; Giudicotti, L.; Boboc, A.; Collaboration: JET-EFDA Contributors

    2009-06-15

    A systematic comparison between the line integrated electron density derived from interferometry and polarimetry at JET has been carried out. For the first time the reliability of the measurements of the Cotton-Mouton effect has been analyzed for a wide range of main plasma parameters and the possibility to evaluate the electron density directly from polarimetric data has been studied. The purpose of this work is to recover the interferometric data with the density derived from the measured Cotton-Mouton effect, when the fringe jump phenomena occur. The results show that the difference between the line integrated electron density from interferometry and polarimetry is with one fringe (1.143x10{sup 19} m{sup -2}) for more than 90% of the cases. It is possible to consider polarimetry as a satisfactory alternative method to interferometry to measure the electron density and it could be used to recover interferometric signal when a fringe jumps occurs, preventing difficulties for the real-time control of many experiments at the JET machine.

  12. Possible cause of enhancement of electron temperature in high electron density region in the dayside ionosphere

    NASA Astrophysics Data System (ADS)

    Kakinami, Yoshihiro; Watanabe, Shigeto

    2016-07-01

    When neutral atmosphere is ionized by solar EUV, energetic electrons named photoelectrons are emitted. The photoelectrons are primary heat source of electrons in the ionosphere in the daytime. The heating rate of electron by photoelectron is proportion to 0.97 power of electron density (Ne) while the heated electron is cooled through the Column collision with ions, the rate of which rate is square of Ne. Therefore, electron temperature (Te) decreases and approach ion temperature (Ti) with increase of Ne. Ions are also cooled through the collision with neutral spices. Finally, these temperatures (Te, Ti and Tn) show very similar values in high Ne region. However, Te enhancement with increase of Ne is found in the satellite observation at 600 km in the daytime ionosphere [Kakinami et al., 2011]. Similar Ti variation is also found around the magnetic dip equator [Kakinami et al., 2014]. One possible cause of the enhancement of Te is enhacement of Tn with increase Ne because both Ne and Tn increase with increase of solar irradiance flux, F10.7 [Lei et al., 2007]. However, since such the enhancements of Te are seen in any F10.7, it is hard to explain the phenomenon. In this paper, we present correlation between Te (Ti) and Ne obtained by the Incoherent Scatter radar at Jicamarca. The similar correlation, namely positive correlation of Te (Ti) with Ne in high Ne region are found above 300 km. Using the observations and Tn and neutral density calculated with MSIS, the Column collision cooling with ions, and inelastic collision cooling with neutral spices for electron are shown. The heat conduction along the magnetic field line is also estimated by using IRI model. Using these information, we discuss possible cause of the enhancement of Te in the high Ne region. References Kakinami et al. (2011), J. Geophys. Res., doi:10.1029/2011JA016905. Kakinami et al. (2014), J. Geophys. Res., 119, doi:10.1002/2014JA020302. Lei et al.(2007), J. Geophys. Res., doi:10.1029/2006JA012041.

  13. Comparing two iteration algorithms of Broyden electron density mixing through an atomic electronic structure computation

    NASA Astrophysics Data System (ADS)

    Man-Hong, Zhang

    2016-05-01

    By performing the electronic structure computation of a Si atom, we compare two iteration algorithms of Broyden electron density mixing in the literature. One was proposed by Johnson and implemented in the well-known VASP code. The other was given by Eyert. We solve the Kohn-Sham equation by using a conventional outward/inward integration of the differential equation and then connect two parts of solutions at the classical turning points, which is different from the method of the matrix eigenvalue solution as used in the VASP code. Compared to Johnson’s algorithm, the one proposed by Eyert needs fewer total iteration numbers. Project supported by the National Natural Science Foundation of China (Grant No. 61176080).

  14. Direct electronic measurement of Peltier cooling and heating in graphene.

    PubMed

    Vera-Marun, I J; van den Berg, J J; Dejene, F K; van Wees, B J

    2016-05-10

    Thermoelectric effects allow the generation of electrical power from waste heat and the electrical control of cooling and heating. Remarkably, these effects are also highly sensitive to the asymmetry in the density of states around the Fermi energy and can therefore be exploited as probes of distortions in the electronic structure at the nanoscale. Here we consider two-dimensional graphene as an excellent nanoscale carbon material for exploring the interaction between electronic and thermal transport phenomena, by presenting a direct and quantitative measurement of the Peltier component to electronic cooling and heating in graphene. Thanks to an architecture including nanoscale thermometers, we detected Peltier component modulation of up to 15 mK for currents of 20 μA at room temperature and observed a full reversal between Peltier cooling and heating for electron and hole regimes. This fundamental thermodynamic property is a complementary tool for the study of nanoscale thermoelectric transport in two-dimensional materials.

  15. Direct electronic measurement of Peltier cooling and heating in graphene

    NASA Astrophysics Data System (ADS)

    Vera-Marun, I. J.; van den Berg, J. J.; Dejene, F. K.; van Wees, B. J.

    2016-05-01

    Thermoelectric effects allow the generation of electrical power from waste heat and the electrical control of cooling and heating. Remarkably, these effects are also highly sensitive to the asymmetry in the density of states around the Fermi energy and can therefore be exploited as probes of distortions in the electronic structure at the nanoscale. Here we consider two-dimensional graphene as an excellent nanoscale carbon material for exploring the interaction between electronic and thermal transport phenomena, by presenting a direct and quantitative measurement of the Peltier component to electronic cooling and heating in graphene. Thanks to an architecture including nanoscale thermometers, we detected Peltier component modulation of up to 15 mK for currents of 20 μA at room temperature and observed a full reversal between Peltier cooling and heating for electron and hole regimes. This fundamental thermodynamic property is a complementary tool for the study of nanoscale thermoelectric transport in two-dimensional materials.

  16. Direct electronic measurement of Peltier cooling and heating in graphene

    PubMed Central

    Vera-Marun, I. J.; van den Berg, J. J.; Dejene, F. K.; van Wees, B. J.

    2016-01-01

    Thermoelectric effects allow the generation of electrical power from waste heat and the electrical control of cooling and heating. Remarkably, these effects are also highly sensitive to the asymmetry in the density of states around the Fermi energy and can therefore be exploited as probes of distortions in the electronic structure at the nanoscale. Here we consider two-dimensional graphene as an excellent nanoscale carbon material for exploring the interaction between electronic and thermal transport phenomena, by presenting a direct and quantitative measurement of the Peltier component to electronic cooling and heating in graphene. Thanks to an architecture including nanoscale thermometers, we detected Peltier component modulation of up to 15 mK for currents of 20 μA at room temperature and observed a full reversal between Peltier cooling and heating for electron and hole regimes. This fundamental thermodynamic property is a complementary tool for the study of nanoscale thermoelectric transport in two-dimensional materials. PMID:27161186

  17. Existence of a virtual cathode close to a strongly electron emissive wall in low density plasmas

    SciTech Connect

    Tierno, S. P. Donoso, J. M.; Domenech-Garret, J. L.; Conde, L.

    2016-01-15

    The interaction between an electron emissive wall, electrically biased in a plasma, is revisited through a simple fluid model. We search for realistic conditions of the existence of a non-monotonic plasma potential profile with a virtual cathode as it is observed in several experiments. We mainly focus our attention on thermionic emission related to the operation of emissive probes for plasma diagnostics, although most conclusions also apply to other electron emission processes. An extended Bohm criterion is derived involving the ratio between the two different electron densities at the potential minimum and at the background plasma. The model allows a phase-diagram analysis, which confirms the existence of the non-monotonic potential profiles with a virtual cathode. This analysis shows that the formation of the potential well critically depends on the emitted electron current and on the velocity at the sheath edge of cold ions flowing from the bulk plasma. As a consequence, a threshold value of the governing parameter is required, in accordance to the physical nature of the electron emission process. The latter is a threshold wall temperature in the case of thermionic electrons. Experimental evidence supports our numerical calculations of this threshold temperature. Besides this, the potential well becomes deeper with increasing electron emission, retaining a fraction of the released current which limits the extent of the bulk plasma perturbation. This noninvasive property would explain the reliable measurements of plasma potential by using the floating potential method of emissive probes operating in the so-called strong emission regime.

  18. Plasma Wave and Electron Density Structure Observed in the Cusp with a Dual-Rocket Experiment

    NASA Astrophysics Data System (ADS)

    Colpitts, C. A.; Labelle, J. W.; Kletzing, C.; Bounds, S.; Cairns, I.

    2008-12-01

    The Twin Rockets to Investigate Cusp Electrodynamics (TRICE) were launched on December 10, 2007, from Andoya Research Range in Andenes, Norway, into the active cusp. Both payloads traveled north over Svalbard, with one payload reaching an apogee of ~1100 km, and the other reaching ~600 km. The payloads were separated by 100-400 km during the main portion of the flight. Both payloads included waveform receivers with 5 MHz bandwidth. These recorded several distinct types of auroral waves including whistler mode waves below ~1000 kHz and Langmuir-upper hybrid waves at 300-3000 kHz for several hundred km. Both payloads concurrently encountered a distinct period of Langmuir turbulence. Clearly defined wave cutoffs provide measurements of electron density and reveal significant density structure with density enhancements having amplitudes up to 100 percent and scale sizes from meters to tens of kilometers. Analysis of the inferred density profiles using windowed Fourier Transforms or Lomb-Scargle periodograms generates dynamic spectra of the density, which provide estimates of the spectral composition of the density irregularities for time intervals sufficiently short that the stationarity of the spectra can be investigated. The large-scale structures through which the two payloads propagated were measured by both the EISCAT and SuperDARN radars as well as by all-sky cameras operated at Longyearbyen and Ny-Alesund on Svalbard. Using this data when available, comparison of the density irregularity waveforms and spectra from the two flights is studied in relation to spatial and altitude variations of the turbulence. This examination of wave and density structures and the large scale formations with which they are associated will add to the understanding of the large scale electrodynamics of the cusp region.

  19. Evaluation of four mammographic density measures on HRT data

    NASA Astrophysics Data System (ADS)

    Raundahl, Jakob; Loog, Marco; Pettersen, Paola; Nielsen, Mads

    2007-03-01

    Numerous studies have investigated the relation between mammographic density and breast cancer risk. These studies indicate that women with dense breasts have a four to six fold risk increase. There is currently no gold standard for automatic assessment of mammographic density. In previous work two different automated methods for measuring the effect of HRT w.r.t. changes in breast density have been presented. One is a percentage density based on an adaptive global threshold, and the other is an intensity invariant measure, which provides structural information orthogonal to intensity-based methods. In this article we investigate the ability to detect density changes induced by HRT for these measures and compare to a radiologist's BI-RADS rating and interactive threshold percentage density. In the experiments, two sets of mammograms of 80 patients from a double blind, placebo controlled HRT experiment are used. The p-values for the statistical significance of the separation of density means, for the HRT group and the placebo group at end of study, are 0.2, 0.1, 0.02 and 0.02 for the automatic threshold, BI-RADS, the stripyness and the interactive threshold respectively.

  20. EDITORIAL: Precision Density Measurements of Solids and Liquids

    NASA Astrophysics Data System (ADS)

    Bettin, Horst

    2006-10-01

    This special feature is dedicated to methods and applications of density measurements of the highest precision. It contains papers from the 210th PTB Seminar 'Precision Density Measurements of Solids and Liquids', which was held at the Physikalisch-Technische Bundesanstalt, Germany, on 24 26 October 2005 and was sponsored by the Helmholtz Funds e.V., Germany. More than 55 density experts from 20 countries attended the seminar. The participants came from national metrological institutes, calibration laboratories, verification offices, universities and manufactures of density meters. Thus, many interesting discussions were stimulated between various groups, in particular between those in research and those working on applications. The main topics of the seminar were the realization of the density unit and its dissemination by comparison methods. The research activities for the determination of the Avogadro constant stimulated the development of new methods as well as the improvement of more conventional methods in order to reach density uncertainties below 0.1 ppm. Technical and physical limitations of the methods were discussed as well as applications and future trends. This special feature contains nine papers based on presentations given at the seminar. Two additional papers on liquid density reference standards and compressibility measurements of liquids complete the feature. I would like to take this opportunity to thank all the authors who contributed to this special feature, which I hope provides an excellent compendium of the topics discussed at the seminar.

  1. 600-GHz Electronically Tunable Vector Measurement System

    NASA Technical Reports Server (NTRS)

    Dengler, Robert; Maiwald, Frank; Siegel, Peter

    2007-01-01

    A compact, high-dynamic-range, electronically tunable vector measurement system that operates in the frequency range from approximately 560 to approximately 635 GHz has been developed as a prototype of vector measurement systems that would be suitable for use in nearly-real-time active submillimeter-wave imaging. As used here, 'vector measurement system" signifies an instrumentation system that applies a radio-frequency (RF) excitation to an object of interest and measures the resulting amplitude and phase response, relative to either the applied excitatory signal or another reference signal related in a known way to applied excitatory signal.

  2. A neural network based error correction method for radio occultation electron density retrieval

    NASA Astrophysics Data System (ADS)

    Pham, Viet-Cuong; Juang, Jyh-Ching

    2015-12-01

    Abel inversion techniques have been widely employed to retrieve electron density profiles (EDPs) from radio occultation (RO) measurements, which are available by observing Global Navigation Satellite System (GNSS) satellites from low-earth-orbit (LEO) satellites. It is well known that the ordinary Abel inversion might introduce errors in the retrieval of EDPs when the spherical symmetry assumption is violated. The error, however, is case-dependent; therefore it is desirable to associate an error index or correction coefficient with respect to each retrieved EDP. Several error indices have been proposed but they only deal with electron density at the F2 peak and suffer from some drawbacks. In this paper we propose an artificial neural network (ANN) based error correction method for EDPs obtained by the ordinary Abel inversion. The ANN is first trained to learn the relationship between vertical total electron content (TEC) measurements and retrieval errors at the F2 peak, 220 km and 110 km altitudes; correction coefficients are then estimated to correct the retrieved EDPs at these three altitudes. Experiments using the NeQuick2 model and real FORMOSAT-3/COSMIC RO geometry show that the proposed method outperforms existing ones. Real incoherent scatter radar (ISR) measurements at the Jicamarca Radio Observatory and the global TEC map provided by the International GNSS Service (IGS) are also used to valid the proposed method.

  3. Measuring the Fluence of Clinical Electron Beams

    NASA Astrophysics Data System (ADS)

    Zaini, Mehran

    1995-01-01

    The incident electron fluence on the patient is greatly affected by the various collimator components on the path of the beam. It is therefore important to measure and characterize these fluence perturbations, which alter the dose distributions. In addition, the incident fluence information is needed as input for the treatment planning algorithms, which are presently inferred from the dose measurements. The magnitude of electron fluence for patient treatments is very low and it is difficult to assess directly. Therefore, a specially designed fluence-meter is required. Of all the detection methods, an ion-implanted semiconductor detector with an ultra-thin depletion layer is the most suitable. We have shown that the energy deposited in an ultra-thin detector, with no window, is directly proportional to the incident fluence of clinical electron beams, including the small contribution of delta-rays. The main reasons for this concept are that (L/rho ) of silicon is essentially constant over the spectrum of any clinical beam and these beams are almost mono-energetic. Our detector is calibrated against a flat Faraday cup and can provide a measure of true electron fluence, with almost no energy and directional dependence. Calibrations are done in a vacuum chamber, where the chamber and the measuring electronics are connected to the accelerator ground. In the calibration setup, a pipe collimation system is used to create a mono-directional beam, so that Phi = Phi_{planar }. Geometrical calculations and films are used for making quantitative analysis of the beam impinging on the detector and the cup. The precision of the calibrations is below 1%. Since the calibration factors of the detector are the same on two different linacs, once a detector is calibrated, it can measure electron fluence on any clinical machine. Fluence output and profiles, and dphi /dtheta of a variety of cones and blocks are measured. The measured surface fluence values conform to the expected shape of

  4. Talbot-Lau X-ray Deflectometer electron density diagnostic for laser and pulsed power high energy density plasma experiments

    DOE PAGES

    Valdivia, M. P.; Stutman, D.; Stoeckl, C.; ...

    2016-04-21

    Talbot-Lau X-ray Deflectometry has been developed as an electron density diagnostic for High Energy Density plasmas. The technique can deliver x-ray refraction, attenuation, elemental composition, and scatter information from a single Moiré image. An 8 keV Talbot-Lau interferometer was deployed using laser and x-pinch backlighters. Grating survival and electron density mapping was demonstrated for 25-29 J, 8-30 ps laser pulses using copper foil targets. Moire pattern formation and grating survival was also observed using a copper x-pinch driven at 400 kA, ~1 kA/ns. Lastly, these results demonstrate the potential of TXD as an electron density diagnostic for HED plasmas.

  5. Measurements of Parity Violation in Electron Scattering

    NASA Astrophysics Data System (ADS)

    Paschke, Kent

    2016-09-01

    The measurement of the violation of parity symmetry in electron scattering has proven to be a powerful technique for exploring nuclear matter and for the search for new fundamental forces. A successful history with the experimental technique has set the stage for a series of high precision measurements to be made over the next decade. Scattering from heavy, spinless targets will measure the neutron skin of heavy nuclei, providing a valuable calibration for the equation-of-state in neutron-rich nuclear systems. Searches for new neutral-current interactions will be performed in ultra-high precision measurements of scattering from protons and electrons at very low momentum transfer Q2 . In the DIS regime, scattering from deuterium will extend this search for new physics while also providing a unique window on nucleon partonic structure. The physics implications of recent results and development of the next generation of experiments will be reviewed.

  6. Structural and electronic properties of small silver-sulfur clusters: A density functional study

    NASA Astrophysics Data System (ADS)

    Li, Yan-Fang; Li, Yang; Li, Ying; Tan, Jia-Jin; Li, Hui-Li

    2016-10-01

    Density functional theory calculations have been performed to systematically investigate the structural and electronic properties of neutral and anionic AgnSm (2≤n+m≤6) clusters. The results show that the ground-state structures of neutral clusters are different from those of anionic clusters. Theoretical electron detachment energies (both vertical and adiabatic) are compared with the experimental measurements to verify the ground states of silver-sulfur clusters obtained in the present study. For both neutral and anionic systems, the highest occupied-lowest unoccupied molecular orbital energy gaps exhibit an odd-even oscillation as a function of the cluster size. In addition, the natural population analysis reveals that the charges transfer from Ag atoms to S atoms in AgnSm clusters, and the extra electron of AgnSm- clusters is mainly localized on the 3p subshells of S atoms.

  7. Comet P/Giacobini-Zinner electron and H2O column densities from ICE and ground-based observations

    NASA Technical Reports Server (NTRS)

    Meyer-Vernet, N.; Strauss, Michael A.; Steinberg, J. L.; Spinrad, Hyron; Mccarthy, Patrick J.

    1986-01-01

    An H2O(+) emission profile extracted from an optical CCD spectrogram obtained during the ICE/Giacobini-Zinner encounter is compared to the electron density profile deduced from in-situ measurements by the ratio experiment aboard ICE. It is concluded that the electrons and the H2O(+) ions are distributed similarly 9600 km tailward from the cometary nucleus; that the ratio of number densities of H2O(+) ions to electrons is 1/4 at this point; and that the width of the plasma sheet is 16,000 km.

  8. User's Guide: An Enhanced Modified Faraday Cup for the Profiling of the Power Density Distribution in Electron Beams

    SciTech Connect

    Elmer, J W; Teruya, A T; Palmer, T A

    2002-06-01

    This handbook describes the assembly and operation of an enhanced Modified Faraday Cup (MFC) diagnostic device for measuring the power density distribution of high power electron beams used for welding. The most recent version of this diagnostic device, [1] Version 2.0, contains modifications to the hardware components of previous MFC designs.[2] These modifications allow for more complete capture of the electrons and better electrical grounding, thus improving the quality of the acquired data and enabling a more accurate computed tomographic (CT) reconstruction [3,4] of the power density distribution of the electron beam to be performed. [ 5-9

  9. Finding the Density of Objects without Measuring Mass and Volume

    ERIC Educational Resources Information Center

    Mumba, Frackson; Tsige, Mesfin

    2007-01-01

    A simple method based on the moment of forces and Archimedes' principle is described for finding density without measuring the mass and volume of an object. The method involves balancing two unknown objects of masses M[subscript 1] and M[subscript 2] on each side of a pivot on a metre rule and measuring their corresponding moment arms. The object…

  10. Electrostatic density measurements in green-state PM parts

    NASA Astrophysics Data System (ADS)

    Leuenberger, Georg H. W.

    The goal of this research is to show the feasibility of detecting density variations in greenstate powder metallurgy (P/M) compacts from surface voltage measurements. By monitoring a steady electric current flow through the sample and recording the voltages over the surface, valuable information is gathered leading to the prediction of the structural health of the compacts. Unlike prior research that concentrated on the detection of surface-breaking and subsurface defects, the results presented in this thesis target the density prediction throughout the volume of the sample. The detection of density variations is achieved by establishing a correlation between the conductivity and their respective density. The data obtained from the surface measurements is used as part of an inversion algorithm, calculating the conductivity distribution, and subsequently the density within the compact. In a first step, the relationship between conductivity and density of green-state P/M compacts was investigated. Tests were conducted for a number of parts of various powder mixtures. In all cases a clear correlation between conductivity and density could be established, indicating that measurements of electric conductivity could indeed be exploited in an effort to render valid information about the density of the sample under test. We found a linear correlation for nonlubricated parts and a non-linear behavior for lubricated samples. Specifically, it was found that the conductivity increases with increasing density only up to a maximum value obtained at approximately 6.9g/cm 3. Interestingly, any additional density increase leads to a reduction of the conductivity. This behavior was confirmed to be inherent in all powder mixtures with lubricants. The thesis research is able to provide a physical model and a mathematical formulation describing this counter-intuitive phenomenon. A finite element solver in conjunction with an inversion algorithm was then implemented to study arbitrarily

  11. WSN-Based Space Charge Density Measurement System.

    PubMed

    Deng, Dawei; Yuan, Haiwen; Lv, Jianxun; Ju, Yong

    2017-01-01

    It is generally acknowledged that high voltage direct current (HVDC) transmission line endures the drawback of large area, because of which the utilization of cable for space charge density monitoring system is of inconvenience. Compared with the traditional communication network, wireless sensor network (WSN) shows advantages in small volume, high flexibility and strong self-organization, thereby presenting great potential in solving the problem. Additionally, WSN is more suitable for the construction of distributed space charge density monitoring system as it has longer distance and higher mobility. A distributed wireless system is designed for collecting and monitoring the space charge density under HVDC transmission lines, which has been widely applied in both Chinese state grid HVDC test base and power transmission projects. Experimental results of the measuring system demonstrated its adaptability in the complex electromagnetic environment under the transmission lines and the ability in realizing accurate, flexible, and stable demands for the measurement of space charge density.

  12. Density measurement in air with saturable absorbing seed gas

    NASA Technical Reports Server (NTRS)

    Baganoff, D.

    1982-01-01

    Approaches which have the potential to make density measurements in a compressible flow, where one or more laser beams are used as probes, were investigated. Saturation in sulfur hexafluoride iodine and a crossed beam technique where one beam acts as a saturating beam and the other is at low intensity and acts as a probe beam are considered. It is shown that a balance between an increase in fluorescence intensity with increasing pressure from line broadening and the normal decrease in intensity with increasing pressure from quenching can be used to develop a linear relation between fluorescence intensity and number density and lead to a new density measurement scheme. The method is used to obtain a density image of the cross section of an iodine seeded underexpanded supersonic jet of nitrogen, by illuminating the cross section by a sheet of laser light.

  13. WSN-Based Space Charge Density Measurement System

    PubMed Central

    Deng, Dawei; Yuan, Haiwen; Lv, Jianxun; Ju, Yong

    2017-01-01

    It is generally acknowledged that high voltage direct current (HVDC) transmission line endures the drawback of large area, because of which the utilization of cable for space charge density monitoring system is of inconvenience. Compared with the traditional communication network, wireless sensor network (WSN) shows advantages in small volume, high flexibility and strong self-organization, thereby presenting great potential in solving the problem. Additionally, WSN is more suitable for the construction of distributed space charge density monitoring system as it has longer distance and higher mobility. A distributed wireless system is designed for collecting and monitoring the space charge density under HVDC transmission lines, which has been widely applied in both Chinese state grid HVDC test base and power transmission projects. Experimental results of the measuring system demonstrated its adaptability in the complex electromagnetic environment under the transmission lines and the ability in realizing accurate, flexible, and stable demands for the measurement of space charge density. PMID:28052105

  14. Electron momentum density, band structure, and structural properties of SrS

    SciTech Connect

    Sharma, G.; Munjal, N.; Vyas, V.; Kumar, R.; Sharma, B. K.; Joshi, K. B.

    2013-10-15

    The electron momentum density, the electronic band structure, and the structural properties of SrS are presented in this paper. The isotropic Compton profile, anisotropies in the directional Compton profiles, the electronic band structure and density of states are calculated using the ab initio periodic linear combination of atomic orbitals method with the CRYSTAL06 code. Structural parameters of SrS-lattice constants and bulk moduli in the B1 and B2 phases-are computed together with the transition pressure. The computed parameters are well in agreement with earlier investigations. To compare the calculated isotropic Compton profile, measurement on polycrystalline SrS is performed using 5Ci-{sup 241}Am Compton spectrometer. Additionally, charge transfer is studied by means of the Compton profiles computed from the ionic model. The nature of bonding in the isovalent SrS and SrO compounds is compared on the basis of equal-valenceelectron-density profiles and the bonding in SrS is found to be more covalent than in SrO.

  15. Direct Measurements of Pore Fluid Density by Vibrating Tube Densimetry

    SciTech Connect

    Gruszkiewicz, Miroslaw {Mirek} S; Rother, Gernot; Wesolowski, David J; Cole, David R; Wallacher, Dirk

    2012-01-01

    The densities of pore-confined fluids were measured for the first time by means of a vibrating tube method. Isotherms of total adsorption capacity were measured directly making the method complementary to the conventional gravimetric or volumetric/piezometric adsorption techniques, which yield the excess adsorption (the Gibbsian surface excess). A custom-made high-pressure, high-temperature vibrating tube densimeter (VTD) was used to measure the densities of subcritical and supercritical propane (between 35 C and 97 C) and supercritical carbon dioxide (between 32 C and 50 C) saturating hydrophobic silica aerogel (0.2 g/cm3, 90% porosity) synthesized inside Hastelloy U-tubes. Additionally, excess adsorption isotherms for supercritical CO2 and the same porous solid were measured gravimetrically using a precise magnetically-coupled microbalance. Pore fluid densities and total adsorption isotherms increased monotonically with increasing density of the bulk fluid, in contrast to excess adsorption isotherms, which reached a maximum at a subcritical density of the bulk fluid, and then decreased towards zero or negative values at supercritical densities. Compression of the confined fluid significantly beyond the density of the bulk liquid at the same temperature was observed at subcritical temperatures. The features of the isotherms of confined fluid density are interpreted to elucidate the observed behavior of excess adsorption. The maxima of excess adsorption were found to occur below the critical density of the bulk fluid at the conditions corresponding to the beginning of the plateau of total adsorption, marking the end of the transition of pore fluid to a denser, liquid-like pore phase. The results for propane and carbon dioxide showed similarity in the sense of the principle of corresponding states. No measurable effect of pore confinement on the liquid-vapor critical point was found. Quantitative agreement was obtained between excess adsorption isotherms determined

  16. X-ray diagnostic for current density profiling relativistic electron beams in vacuum and gas

    SciTech Connect

    Slaughter, D.; Koppel, L.; Smith, J.

    1986-02-15

    An x-ray imaging technique has been studied for the purpose of observing the current density profile in a high-current relativistic electron beam (50 MeV, 10 kA). Calculations and measurements of energy spectra and intensities are in good agreement. Results indicate sufficient photon yield for pinhole imaging when the beam deposits a small part of its energy in high-Z gas or a thin high-Z foil. Characteristic L and K x-ray emission is not found not be a reliable technique due to strong L and K shell fluorescence in the presence of intense bremsstrahlung radiation. It is also found that at pressures on the order of one atmosphere, the density of energy deposition in a gas cell is too small to generate sufficient photon yield for time-resolved measurements.

  17. Density fluctuation spectrum of solar wind turbulence between ion and electron scales.

    PubMed

    Chen, C H K; Salem, C S; Bonnell, J W; Mozer, F S; Bale, S D

    2012-07-20

    We present a measurement of the spectral index of density fluctuations between ion and electron scales in solar wind turbulence using the EFI instrument on the ARTEMIS spacecraft. The mean spectral index at 1 AU was found to be -2.75±0.06, steeper than predictions for pure whistler or kinetic Alfvén wave turbulence but consistent with previous magnetic field measurements. The steep spectra are also consistent with expectations of increased intermittency or damping of some of the turbulent energy over this range of scales. Neither the spectral index nor the flattening of the density spectra before ion scales were found to depend on the proximity to the pressure anisotropy instability thresholds, suggesting that they are features inherent to the turbulent cascade.

  18. A quantitative measure of phase correlations in density fields

    NASA Technical Reports Server (NTRS)

    Scherrer, Robert J.; Melott, Adrian L.; Shandarin, Sergei F.

    1991-01-01

    A quantitative measure of the phase correlations in a density field is presented based on the location of the maxima of the Fourier components of that field. It is found that this measue can easily detect non-Gaussian behavior either in artificially constructed density fields or those that become non-Gaussian from gravitational clustering of Gaussian initial conditions. It is found that different initial power spectra produce somewhat distinguishable signals, and the signals are robust against sparse sampling.

  19. Measurement of the lunar neutron density profile. [Apollo 17 flight

    NASA Technical Reports Server (NTRS)

    Woolum, D. S.; Burnett, D. S.; Furst, M.; Weiss, J. R.

    1974-01-01

    An in situ measurement of the lunar neutron density from 20 to 400 g/sq cm depth between the lunar surface was made by the Apollo 17 Lunar Neutron Probe Experiment using particle tracks produced by the B10(n, alpha)Li7 reaction. Both the absolute magnitude and depth profile of the neutron density are in good agreement with past theoretical calculations. The effect of cadmium absorption on the neutron density and in the relative Sm149 to Gd157 capture rates obtained experimentally implies that the true lunar Gd157 capture rate is about one half of that calculated theoretically.

  20. Measuring soil particle density using the ultrasonic method

    NASA Astrophysics Data System (ADS)

    Vennik, Kersti; Tõnutare, Tõnu; Krebstein, Kadri; Keller, Thomas

    2015-04-01

    Particle density is a fundamental soil physical parameter that represents the density of the solid soil particles (mineral and organic) and is expressed as the ratio of the mass to the volume of the solid. Particle density serves as input value in many models, such as soil compression and bearing capacity models. Particle density is often estimated rather than measured. In Estonia particle density is typically estimated based on soil organic matter content by Kitse's (1978) and Reppo's (1968) formulas for mineral and peat soils. The standard method for measuring particle density is the pycnometer method in which entrapped air is removed by vacuum or by boiling the soil-water mixture. The ultrasonic technology is widely used in chromatography for degassing of solutions and is easy to use. This ultrasonic energy can also be used for sweeping out the gaseous phase from the soil-water mixture, however the appropriate treatment time is not yet specified. The purpose of this study was to test the usability of ultrasonic energy in particle density determination as well to test different treatment time steps with ultrasonic path. We sampled 15 typical Estonian mineral soils with different texture and organic content. Also 3 peat soils were analysed. Particle density was determined by the pycnometer method and with ultrasonic bath. Soil organic carbon (SOC) content was determined by the Tjurin method and the soil organic matter content (SOM) was calculated as SOM=1.724SOC. The particle density values determined with the pycnometer method were compared to values measured with the ultrasonic bath with different time steps, as well as to calculated values according to Kitse (1978) and Reppo (1968). The applicability of formulas by Kitse and Reppo were tested by comparing the estimated particle densities with measured particle densities. Based on the results of this study it can be concluded that ultrasonic method is applicable for particle density determination and the most

  1. Variation of carrier concentration and interface trap density in 8MeV electron irradiated c-Si solar cells

    SciTech Connect

    Bhat, Sathyanarayana Rao, Asha; Krishnan, Sheeja; Sanjeev, Ganesh; Suresh, E. P.

    2014-04-24

    The capacitance and conductance measurements were carried out for c-Si solar cells, irradiated with 8 MeV electrons with doses ranging from 5kGy – 100kGy in order to investigate the anomalous degradation of the cells in the radiation harsh environments. Capacitance – Voltage measurements indicate that there is a slight reduction in the carrier concentration upon electron irradiation due to the creation of radiation induced defects. The conductance measurement results reveal that the interface state densities and the trap time constant increases with electron dose due to displacement damages in c-Si solar cells.

  2. Comparison of DMSP SSIES Density and Temperature Measurements With Ground-Based Incoherent Scatter Radar Data

    NASA Astrophysics Data System (ADS)

    Keyser, H. L.; Green, B. S.; della-Rose, D. J.; Sojka, J. J.; Erickson, P. J.; Hairston, M. R.; Rich, F. J.

    2003-12-01

    We have compared electron density and temperature data, measured aboard the Defense Meteorological Satellite Program (DMSP) spacecraft, against POLITE campaign data collected by the Millstone Hill incoherent scatter radar. The POLITE data span the period between February 1996 (near solar minimum) and July 2000 (near solar maximum). Following the work of Sultan and Rich [2000], we averaged the DMSP data within a five-degree circle of Millstone Hill, and averaged the corresponding radar data within +/-30 minutes of the satellite overflight time. Our study revealed that the average electron density difference between DMSP and Millstone data exceeds 20 percent, which is statistically significant compared to the published DMSP topside ionospheric plasma monitor (SSIES) instrument accuracy. Further, DMSP density values are typically lower than the corresponding radar measurements; this negative bias is largest near solar minimum. Conversely, DMSP electron temperature values are an average 23 percent higher than the radar-derived temperature. This difference is statistically significant compared to both the DMSP and radar errors. As with the electron density, the bias lessens toward solar maximum. This temperature bias appears to decrease as the DMSP zenith angle increases, and this suggests the possibility of increased photoelectron contamination of the Langmuir probe for smaller zenith angles. Apart from this, however, the root cause(s) for these density and temperature differences remain under study.

  3. Measurement of dielectric-film thickness at low density plasma

    NASA Astrophysics Data System (ADS)

    Jeon, Sang-Bum; Kim, Dong-Hwan; Kim, Jin-Yong; Paek, Se-Yeol; Chung, Chin-Wook

    2016-09-01

    The measurement system of dielectric-film thickness was improved to measure thin-film at low density plasma. There are three improvements than previous method, which is electrical measurement of dielectric-film thickness using R-C sheath model. First, the frequency of input voltage was decreased to reduce the ratio of the dielectric-film impedance to sheath impedance. Second, three different frequencies were used to overcome the inaccuracy of measured phase; only amplitudes of measured current were used to obtain a film thickness. Third, the notch filter was used for sensing current instead of the resistor to improve the signal to noise ratio. Using this method, dielectric-film thickness was well measured at low density plasma (thickness: 300, sheath impedance: 100 200 k Ω) .

  4. High-Sensitivity Measurement of Density by Magnetic Levitation.

    PubMed

    Nemiroski, Alex; Kumar, A A; Soh, Siowling; Harburg, Daniel V; Yu, Hai-Dong; Whitesides, George M

    2016-03-01

    This paper presents methods that use Magnetic Levitation (MagLev) to measure very small differences in density of solid diamagnetic objects suspended in a paramagnetic medium. Previous work in this field has shown that, while it is a convenient method, standard MagLev (i.e., where the direction of magnetization and gravitational force are parallel) cannot resolve differences in density <10(-4) g/cm(3) for macroscopic objects (>mm) because (i) objects close in density prevent each other from reaching an equilibrium height due to hard contact and excluded volume, and (ii) using weaker magnets or reducing the magnetic susceptibility of the medium destabilizes the magnetic trap. The present work investigates the use of weak magnetic gradients parallel to the faces of the magnets as a means of increasing the sensitivity of MagLev without destabilization. Configuring the MagLev device in a rotated state (i.e., where the direction of magnetization and gravitational force are perpendicular) relative to the standard configuration enables simple measurements along the axes with the highest sensitivity to changes in density. Manipulating the distance of separation between the magnets or the lengths of the magnets (along the axis of measurement) enables the sensitivity to be tuned. These modifications enable an improvement in the resolution up to 100-fold over the standard configuration, and measurements with resolution down to 10(-6) g/cm(3). Three examples of characterizing the small differences in density among samples of materials having ostensibly indistinguishable densities-Nylon spheres, PMMA spheres, and drug spheres-demonstrate the applicability of rotated Maglev to measuring the density of small (0.1-1 mm) objects with high sensitivity. This capability will be useful in materials science, separations, and quality control of manufactured objects.

  5. Faraday-effect polarimeter-interferometer system for current density measurement on EAST

    NASA Astrophysics Data System (ADS)

    Liu, H. Q.; Jie, Y. X.; Ding, W. X.; Brower, D. L.; Zou, Z. Y.; Li, W. M.; Wang, Z. X.; Qian, J. P.; Yang, Y.; Zeng, L.; Lan, T.; Wei, X. C.; Li, G. S.; Hu, L. Q.; Wan, B. N.

    2014-11-01

    A multichannel far-infrared laser-based POlarimeter-INTerferometer (POINT) system utilizing the three-wave technique is under development for current density and electron density profile measurements in the EAST tokamak. Novel molybdenum retro-reflectors are mounted in the inside wall for the double-pass optical arrangement. A Digital Phase Detector with 250 kHz bandwidth, which will provide real-time Faraday rotation angle and density phase shift output, have been developed for use on the POINT system. Initial calibration indicates the electron line-integrated density resolution is less than 5 × 1016 m-2 (˜2°), and the Faraday rotation angle rms phase noise is <0.1°.

  6. Faraday-effect polarimeter-interferometer system for current density measurement on EAST.

    PubMed

    Liu, H Q; Jie, Y X; Ding, W X; Brower, D L; Zou, Z Y; Li, W M; Wang, Z X; Qian, J P; Yang, Y; Zeng, L; Lan, T; Wei, X C; Li, G S; Hu, L Q; Wan, B N

    2014-11-01

    A multichannel far-infrared laser-based POlarimeter-INTerferometer (POINT) system utilizing the three-wave technique is under development for current density and electron density profile measurements in the EAST tokamak. Novel molybdenum retro-reflectors are mounted in the inside wall for the double-pass optical arrangement. A Digital Phase Detector with 250 kHz bandwidth, which will provide real-time Faraday rotation angle and density phase shift output, have been developed for use on the POINT system. Initial calibration indicates the electron line-integrated density resolution is less than 5 × 10(16) m(-2) (∼2°), and the Faraday rotation angle rms phase noise is <0.1°.

  7. Faraday-effect polarimeter-interferometer system for current density measurement on EAST

    SciTech Connect

    Liu, H. Q.; Jie, Y. X. Zou, Z. Y.; Li, W. M.; Wang, Z. X.; Qian, J. P.; Yang, Y.; Zeng, L.; Wei, X. C.; Hu, L. Q.; Wan, B. N.; Ding, W. X.; Brower, D. L.; Lan, T.; Li, G. S.

    2014-11-15

    A multichannel far-infrared laser-based POlarimeter-INTerferometer (POINT) system utilizing the three-wave technique is under development for current density and electron density profile measurements in the EAST tokamak. Novel molybdenum retro-reflectors are mounted in the inside wall for the double-pass optical arrangement. A Digital Phase Detector with 250 kHz bandwidth, which will provide real-time Faraday rotation angle and density phase shift output, have been developed for use on the POINT system. Initial calibration indicates the electron line-integrated density resolution is less than 5 × 10{sup 16} m{sup −2} (∼2°), and the Faraday rotation angle rms phase noise is <0.1°.

  8. Boundary location of Mars nightside ionospheric plasma in term of the electron density

    NASA Astrophysics Data System (ADS)

    Morooka, Michiko W.; Andersson, Laila; Ergun, Bob; Fowler, Christopher; Woodson, Adam; Weber, Tristan; Delory, Greg; Andrews, David; Edberg, Niklas; Eriksson, Anders; Michell, David; Connerney, Jack; Gruesbeck, Jacob; Halekas, Jasper

    2015-11-01

    Photo-ionized Mars atmosphere is forming an ionosphere and shielding the solar wind with creating barriers of bow shock. Inside the bow shock ionospheric plasma interact with solar wind plasma and result different boundaries. A question is how far the ionospheric plasma can stand off the solar wind.On the dayside, in-situ data set from Mars magnetosphere missions often observed the sharp gradient of the thermal plasma flux and ion composition change as well as the drop off of the magnetic fluctuation simultaneously as a outer boundary of the ionospheric plasma and an obstacle to the solar wind. Several models have constructed the shape of the boundary based on the statistical observations [e.g., Trotignon et al., 2006; Edberg et al., 2008].On the nightside, plasma instrument onboard Phobos 2 observed the particles and magnetic field characteristics similar to the dayside. However, the number of data is still too few to understand the general location of boundaries. We will present the characteristics of the nightside magnetospheric boundary region in term of the electron density. MAVEN Langmuir probe measurement (LPW) can estimate the electron density using the spacecraft environment. As MAVEN pass from the bow shock and sheath region into the magnetosphere the electron density often show a sharp gradient (the density jumps two orders of magnitudes in a few seconds). Comparing this to the data from particle instrument, the sharp electron density gradient was often associated with the transition of the characteristic energy of ions.Several hundreds of boundaries crossing by MAVEN allow us to investigate the statistical view of the boundary. We searched for a large electron density gradient as an indicator of the plasma boundary to identify the location of the ionospheric/solar wind plasma boundary. The results show that the many of the nightside boundaries locates close to the tail region of Mars forming elliptical shape of boundary. We will provide the empirical

  9. Principles for microwave moisture and density measurement in grain and seed.

    PubMed

    Nelson, Stuart O; Trabelsi, Samir

    2004-01-01

    The importance of cereal grain moisture content in determining time of harvest and in preserving grain quality is described. Techniques for moisture measurement, including electronic moisture meters, are also discussed briefly, and the need for better moisture sensing techniques for modern agricultural on-line moisture monitoring is described. Principles of microwave free-space measurements involving attenuation and phase-shift determination are explained, and density-independent functions of the grain permittivity are presented that permit reliable moisture sensing applicable to moving grain in which bulk density variation occurs. Three different approaches are discussed for determining moisture content and bulk density of grain from microwave measurement of the dielectric properties. A new moisture calibration function, based on complex-plane plots of dielectric constant and loss factor, each divided by bulk density, is described, which promises a universal calibration for different types of grain and seed. This important advantage should encourage commercial development for practical use.

  10. Temperature measurement systems in wearable electronics

    NASA Astrophysics Data System (ADS)

    Walczak, S.; Gołebiowski, J.

    2014-08-01

    The aim of this paper is to present the concept of temperature measurement system, adapted to wearable electronics applications. Temperature is one of the most commonly monitored factor in smart textiles, especially in sportswear, medical and rescue products. Depending on the application, measured temperature could be used as an initial value of alert, heating, lifesaving or analysis system. The concept of the temperature measurement multi-point system, which consists of flexible screen-printed resistive sensors, placed on the T-shirt connected with the central unit and the power supply is elaborated in the paper.

  11. Atomic and electronic structure of polar oxide interfaces: Electron microscopy and density functional theory study

    NASA Astrophysics Data System (ADS)

    Lazarov, Vlado

    Polar oxide interfaces are formed when two polar oxide surfaces join. The apparent presence of an electric dipole moment in the repeat unit parallel to the surface/interface closely relate the polar oxide interfaces instability to that of the of polar oxide surfaces. In this thesis, we combined Electron Microscopy and Density Functional Theory to study how the interface polarity affects the atomic and electronic structure of polar oxide interfaces, by using Fe3O4(111)/MgO(111) as a model system. The formation of Fe nanoinclusions found at the interface and within the polar Fe3 O4(111) film is proposed to be new stabilization mechanism for the magnetite film. High-resolution electron microscopy imaging of the interface together with first principle calculations suggest an atomically abrupt substrate-film interface determined with Fe monolayer in octahedral position (FeB). This interface stacking (O/Mg/O/3FeB/O) provides lowest total interface (system) energy and the most effectively screening of the MgO(111) substrate surface polarity. The results of our study suggest that surface polarity could be used as an additional growth parameter in creating novel material structures, such as metals in oxide matrices.

  12. Stationary Conditions of the Electron Density Along the Reaction Path: Connection with Conceptual DFT and Information Theory.

    PubMed

    Gonzalez, Carlos A; Squitieri, Emilio; Franco, Hector J; Rincon, Luis C

    2017-01-26

    The Kohn-Sham density functional theory (DFT) formalism has been used to investigate the influence of the stationary behavior of the electron density (ρ(r⃗;s)) along a minimum energy path on the corresponding stationary conditions observed in the total potential energy of the reactive system, information theory measures (Shannon information entropy and Onicescu information energy), and chemical reactivity indexes (the chemical hardness). The theoretical treatment presented in this work, combined with DFT calculations on 3 different test reactions: Ḣ' + H2, Ḣ' + CH4 and H(-) + CH4, suggest that for any reactive system, properties that can be cast as a functional of the electron density, must exhibit stationary points along the IRC path modulated by the corresponding stationary behavior of the electron density.

  13. TRACTOGRAPHY DENSITY AND NETWORK MEASURES IN ALZHEIMER'S DISEASE.

    PubMed

    Prasad, Gautam; Nir, Talia M; Toga, Arthur W; Thompson, Paul M

    2013-04-01

    Brain connectivity declines in Alzheimer's disease (AD), both functionally and structurally. Connectivity maps and networks derived from diffusion-based tractography offer new ways to track disease progression and to understand how AD affects the brain. Here we set out to identify (1) which fiber network measures show greatest differences between AD patients and controls, and (2) how these effects depend on the density of fibers extracted by the tractography algorithm. We computed brain networks from diffusion-weighted images (DWI) of the brain, in 110 subjects (28 normal elderly, 56 with early and 11 with late mild cognitive impairment, and 15 with AD). We derived connectivity matrices and network topology measures, for each subject, from whole-brain tractography and cortical parcellations. We used an ODF lookup table to speed up fiber extraction, and to exploit the full information in the orientation distribution function (ODF). This made it feasible to compute high density connectivity maps. We used accelerated tractography to compute a large number of fibers to understand what effect fiber density has on network measures and in distinguishing different disease groups in our data. We focused on global efficiency, transitivity, path length, mean degree, density, modularity, small world, and assortativity measures computed from weighted and binary undirected connectivity matrices. Of all these measures, the mean nodal degree best distinguished diagnostic groups. High-density fiber matrices were most helpful for picking up the more subtle clinical differences, e.g. between mild cognitively impaired (MCI) and normals, or for distinguishing subtypes of MCI (early versus late). Care is needed in clinical analyses of brain connectivity, as the density of extracted fibers may affect how well a network measure can pick up differences between patients and controls.

  14. Precision measurements of linear scattering density using muon tomography

    NASA Astrophysics Data System (ADS)

    Åström, E.; Bonomi, G.; Calliari, I.; Calvini, P.; Checchia, P.; Donzella, A.; Faraci, E.; Forsberg, F.; Gonella, F.; Hu, X.; Klinger, J.; Sundqvist Ökvist, L.; Pagano, D.; Rigoni, A.; Ramous, E.; Urbani, M.; Vanini, S.; Zenoni, A.; Zumerle, G.

    2016-07-01

    We demonstrate that muon tomography can be used to precisely measure the properties of various materials. The materials which have been considered have been extracted from an experimental blast furnace, including carbon (coke) and iron oxides, for which measurements of the linear scattering density relative to the mass density have been performed with an absolute precision of 10%. We report the procedures that are used in order to obtain such precision, and a discussion is presented to address the expected performance of the technique when applied to heavier materials. The results we obtain do not depend on the specific type of material considered and therefore they can be extended to any application.

  15. Lunar Surface Material - Spacecraft Measurements of Density and Strength

    NASA Technical Reports Server (NTRS)

    Jaffe, L. D.

    1969-01-01

    The relation of the density of the lunar surface layer to depth is probably best determined from spacecraft measurements of the bearing capacity as a function of depth. A comparison of these values with laboratory measurements of the bearing capacity of low-cohesion particulate materials as a function of the percentage of solid indicates that the bulk density at the lunar surface is about 1.1 grams per cubic centimeter and that it increases nearly linearly to about 1.6 grams per cubic centimeter at a depth of 5 centimeters.

  16. Density measurements of compressed-liquid dimethyl ether + pentane mixtures

    PubMed Central

    Outcalt, Stephanie L.; Lemmon, Eric W.

    2016-01-01

    Compressed-liquid densities of three compositions of the binary mixture dimethyl ether (CAS No. 115-10-6) + pentane (CAS No. 109-66-0) have been measured with a vibrating U-tube densimeter. Measurements were made at temperatures from 270 K to 390 K with pressures from 1.0 MPa to 50 MPa. The overall combined uncertainty (k=2) of the density data is 0.81 kg·m−3. Data presented here have been used to improve a previously formulated Helmholtz energy based mixture model. The newly derived parameters are given. PMID:27840450

  17. Guiding and collimating the fast electrons by using a low-density-core target with buried high density layers

    NASA Astrophysics Data System (ADS)

    Lv, Chong; Wan, Feng; Hou, Ya-Juan; Jia, Mo-Ran; Sang, Hai-Bo; Xie, Bai-Song; Liu, Shi-Bing

    2017-02-01

    A low-density-core target with buried high density layers is proposed to improve the transport of fast electrons and involved problems are investigated by using two-dimensional particle-in-cell simulations. It is demonstrated that this target can collimate the fast electrons efficiently and lead to a better beam quality. The enhancement is attributed to the weakening of the two stream instability and the better collimation by the self-generated multilayer megagauss magnetic field as well as the baroclinic magnetic field. Comparing this to that without buried high density layers, the energy flux of fast electrons is increased by a factor of about 1.8 and has a narrower transverse distribution in space. Besides, the dependence of the efficiency on the target parameters is examined, and the optimal target parameters are also obtained. Such a target can be useful to many applications, such as fast ignition in inertial fusion.

  18. A microwave interferometer for small and tenuous plasma density measurements.

    PubMed

    Tudisco, O; Lucca Fabris, A; Falcetta, C; Accatino, L; De Angelis, R; Manente, M; Ferri, F; Florean, M; Neri, C; Mazzotta, C; Pavarin, D; Pollastrone, F; Rocchi, G; Selmo, A; Tasinato, L; Trezzolani, F; Tuccillo, A A

    2013-03-01

    The non-intrusive density measurement of the thin plasma produced by a mini-helicon space thruster (HPH.com project) is a challenge, due to the broad density range (between 10(16) m(-3) and 10(19) m(-3)) and the small size of the plasma source (2 cm of diameter). A microwave interferometer has been developed for this purpose. Due to the small size of plasma, the probing beam wavelength must be small (λ = 4 mm), thus a very high sensitivity interferometer is required in order to observe the lower density values. A low noise digital phase detector with a phase noise of 0.02° has been used, corresponding to a density of 0.5 × 10(16) m(-3).

  19. A microwave interferometer for small and tenuous plasma density measurements

    SciTech Connect

    Tudisco, O.; Falcetta, C.; De Angelis, R.; Florean, M.; Neri, C.; Mazzotta, C.; Pollastrone, F.; Rocchi, G.; Tuccillo, A. A.; Lucca Fabris, A.; Manente, M.; Ferri, F.; Tasinato, L.; Trezzolani, F.; Accatino, L.; Selmo, A.

    2013-03-15

    The non-intrusive density measurement of the thin plasma produced by a mini-helicon space thruster (HPH.com project) is a challenge, due to the broad density range (between 10{sup 16} m{sup -3} and 10{sup 19} m{sup -3}) and the small size of the plasma source (2 cm of diameter). A microwave interferometer has been developed for this purpose. Due to the small size of plasma, the probing beam wavelength must be small ({lambda}= 4 mm), thus a very high sensitivity interferometer is required in order to observe the lower density values. A low noise digital phase detector with a phase noise of 0.02 Degree-Sign has been used, corresponding to a density of 0.5 Multiplication-Sign 10{sup 16} m{sup -3}.

  20. Ionospheric electron density retrieval from FORMOSAT-3/COSMIC occultation data for a period of more than half a Solar Cycle

    NASA Astrophysics Data System (ADS)

    Limberger, Marco; Hernandez-Pajarez, Manuel; García Rigo, Alberto; Schmidt, Michael; Hugentobler, Urs

    2014-05-01

    The disposability of information about the atmospheric electron density distribution plays an important role in a variety of application areas such as space weather monitoring and prediction, in ionosphere modeling and in general for numerous aspects in radio science. In this context, the ionospheric region constitutes a key component in the system of Sun-Earth interactions due to its high concentration of charged particles, especially electrons. One prevailing method for the exploration of the Earth's ionosphere is the application of GPS radio occultation measurements onboard Low Earth Orbiter (LEO) satellites to derive electron density values below the LEO orbit where an advanced retrieval method shall be described in this work. Besides, we present a comprehensive analysis and validation of the electron density information retrieved by GPS satellite occultation measurements taken from the FORMOSAT-3/COSMIC constellation. A signal, transmitted by a GPS satellite and tracked on a LEO in occultation geometry, becomes delayed on its way through the atmospheric medium which allows for the determination of the refractivity indices based on the solution of an inverse problem with observations at different elevation angles. A classical Abel inversion algorithm may be applied to solve this inverse problem but goes along with mainly two drawbacks related to (1) the consideration of a spherical symmetry assumption for the electron density implying that electron density and accordingly the refractivity indices only depend on height and (2) the negligence of electron density data above the LEO orbit. Instead, a modified Abel inversion based on an algorithm developed previously at UPC will be considered in this work. It includes the supposition that electron density measurements can be described by the vertical total electron content, e.g. determined from terrestrial GNSS networks, in combination with an additional shape function (separability hypothesis) for the description

  1. Density fluctuation measurement using motional Stark effect optics in JT-60U

    SciTech Connect

    Suzuki, T.; Fujita, T.; Oyama, N.; Isayama, A.; Matsunaga, G.; Oikawa, T.; Asakura, N.; Takechi, M.

    2006-10-15

    The multichannel motional Stark effect (MSE) diagnostic system in JT-60U has been upgraded to measure density fluctuation profile. A 16-channel fast-sampling digitizer has been added in order to measure photomultiplier-tube signals at measurement frequency of 0.5-1 MHz. The new system works as a MSE and beam emission spectroscopy diagnostic. Spatially resolved electron density fluctuation profile measurement in various operation regimes is presented. In the core plasma, density fluctuation induced by rotation of tearing mode islands was observed. Temporal evolution of the fluctuation frequency agrees with that measured by Mirnov coils (poloidal and toroidal mode numbers: 2 and 1, respectively). The phases of the fluctuations on either side of the q=2 surface are inverted, which is consistent with electron cyclotron emission. These measurements show that the density fluctuation is caused by a rotating magnetic island structure induced by the tearing mode. In the scrape-off layer of a H-mode plasma with edge-localized-mode (ELM), i. e., ELMy H-mode outward propagation of strong intermittent emission corresponding to ELM crash was also observed. The propagation velocity is 0.69-2.2 km/s along the MSE measurement points, the time lag and distance between adjacent channels being 67{+-}35 {mu}s and 70 mm, respectively.

  2. Control of ion density distribution by magnetic traps for plasma electrons

    SciTech Connect

    Baranov, Oleg; Romanov, Maxim; Fang Jinghua; Cvelbar, Uros; Ostrikov, Kostya

    2012-10-01

    The effect of a magnetic field of two magnetic coils on the ion current density distribution in the setup for low-temperature plasma deposition is investigated. The substrate of 400 mm diameter is placed at a distance of 325 mm from the plasma duct exit, with the two magnetic coils mounted symmetrically under the substrate at a distance of 140 mm relative to the substrate centre. A planar probe is used to measure the ion current density distribution along the plasma flux cross-sections at distances of 150, 230, and 325 mm from the plasma duct exit. It is shown that the magnetic field strongly affects the ion current density distribution. Transparent plastic films are used to investigate qualitatively the ion density distribution profiles and the effect of the magnetic field. A theoretical model is developed to describe the interaction of the ion fluxes with the negative space charge regions associated with the magnetic trapping of the plasma electrons. Theoretical results are compared with the experimental measurements, and a reasonable agreement is demonstrated.

  3. Fast tokamak plasma flux and electron density reconstruction technique

    SciTech Connect

    Chiang, K.L.; Hallock, G.A.; Wootton, A.J.; Wang, L.

    1997-01-01

    Density profiles in TEXT-U are obtained using a vertical viewing far-infrared (FIR) interferometer. To obtain the local (inverted) density, we have developed a simple analytic model of the plasma equilibrium configuration which is faster than EFIT (a flux surface reconstruction program) and can be easily computed between discharges. This analytic solution of the Grad{endash}Shafranov equation is valid as long as the pressure p is a function of poloidal flux {psi}, i.e., p=p({psi}). The procedure incorporates both magnetic and FIR density data to solve the Grad{endash}Shafranov equation, and provides a density profile which is self-consistent with the reconstructed equilibrium flux surfaces. Examples are presented. {copyright} {ital 1997 American Institute of Physics.}

  4. Density matrix renormalization group with efficient dynamical electron correlation through range separation

    SciTech Connect

    Hedegård, Erik Donovan Knecht, Stefan; Reiher, Markus; Kielberg, Jesper Skau; Jensen, Hans Jørgen Aagaard

    2015-06-14

    We present a new hybrid multiconfigurational method based on the concept of range-separation that combines the density matrix renormalization group approach with density functional theory. This new method is designed for the simultaneous description of dynamical and static electron-correlation effects in multiconfigurational electronic structure problems.

  5. Comparison of bone density measurement techniques: DXA and Archimedes' principle.

    PubMed

    Keenan, M J; Hegsted, M; Jones, K L; Delany, J P; Kime, J C; Melancon, L E; Tulley, R T; Hong, K D

    1997-11-01

    The standard method for determination of density (g/cm3) of bones from small animals has been the application of Archimedes' principle. A recent development has been software for the determination of "density" (g/cm2) of small animal bones with dual-energy X-ray absorptiometry (DXA). We compared Archimedes' principle and DXA (Hologic QDR-2000) in the measurement of the densities of whole and hollowed femurs of 5- to 6-month-old retired female breeder rats. In an attempt to ensure detectable treatment differences, rats were used from a low-vitamin D Holtzman and a supplemental-vitamin D Sprague-Dawley colony. Whole femur densities were higher for supplemental-vitamin D colony rats than for low vitamin D rats using both techniques (Archimedes' principle, p < 0.002; DXA, p < 0.005), and the densities from the two techniques were highly correlated (r = 0.82, p < 0.0001). Actual density values were higher for Archimedes' principle than for DXA. Other variables such as femur ash weight and calcium content were also highly correlated to densities with both techniques. Hollowed femur density values were higher than whole femur values with Archimedes' principle but lower with DXA. Colony effects for hollowed femur densities were diminished with Archimedes' principle (p < 0.03) and eliminated with DXA (p < 0.53). Investigation of whole bones is more biologically relevant, and both techniques were effective in detecting differences between whole femurs from low-vitamin D and supplemental-vitamin D colony rats.

  6. Improved measurement of ice layer density in seasonal snowpacks

    NASA Astrophysics Data System (ADS)

    Watts, T.; Rutter, N.; Toose, P.; Derksen, C.; Sandells, M.; Woodward, J.

    2015-11-01

    Ice layers in snowpacks introduce uncertainty in satellite derived estimates of snow water equivalent, have ecological impacts on plants and animals, and change the thermal and vapour transport properties of the snowpack. The microstructure and specifically the density of ice layers is poorly quantified. Here we present a new field method, for measuring the density of ice layers caused by melt or rain-on-snow events. The method was used on 87 ice layer samples in the Canadian Arctic and mid-latitudes; the mean measured ice layer density was 909 ± 18 kg m-3 with a standard deviation of 23 kg m-3, significantly higher than values typically used in the literature.

  7. Electron beam fluorescence measurements in the Boeing hypersonic shock tunnel

    NASA Technical Reports Server (NTRS)

    Price, Linwood L.; Williams, W. Dan; Powell, H. M.

    1992-01-01

    The Calspan electron beam fluorescence (EBF) measurement system is described along with the results of measurements made in hypersonic flow. Numerous self-emitting metallic species were identified, many of which may be associated with an aging/erosion process within the B30HST. Because there were only 16 tunnel runs, it was only possible to obtain spectral measurements over a limited range of wavelengths and time sampling periods. Many spectral features of the flow remain uninvestigated. Because flow self-emission is important to all optical diagnostic techniques, it is recommended that additional spectral studies by performed. The three electron beam-excited species that were identified are nitrogen, helium, and nitric oxide. The high metallic radiation background interfered with attempts to obtain the time-wise variation of N2 density and He radiation with the optical fiber/PMT channels. In the case of the N2 density measurements the result of interference was increased uncertainty. Unfortunately, the interference caused the time-wise He measurements to fail completely. It is recommended that the electron beam be modulated to provide discrimination against the background radiation in future N2 density measurements. Careful data reduction produced useful measurements of N2 vibrational temperature, even though the high background from metallic species significantly increased measurement uncertainty. Perhaps the recommended additional spectral studies would reveal N2(+) First Negative System band-pair regions having less background. Detection of the He arrival was easily accomplished with the spectrometer/array detector system. Because of this, it is recommended that this means of detecting He arrival be used in the future. With proper calibrations of the system an He number density could be obtained. Although the flow conditions were out of limits for the run in which the NO spectrum was recorded, the usefulness of the NO spectrum for determination of free

  8. Electron density and temperature in the solar corona from multifrequency radio imaging

    NASA Astrophysics Data System (ADS)

    Mercier, C.; Chambe, G.

    2015-11-01

    Context. The 2D images obtained through rotational aperture synthesis with the Nançay Radioheliograph are suitable for quantitative exploitation. First results are presented. Aims: We study the variations of the quiet corona in brightness and size during an 8-year period and derive electron density and temperature in the corona. Methods: Images at 6 frequencies between 150 and 450 MHz for 183 quiet days between 2004 and 2011 were used. Measurements of the brightness temperature Tb beyond the limb allowed coronal density models to be derived in both EW and NS radial directions, with a weak dependence on the electron temperature. The total ranges in the heliocentric distance r are 1.15-1.60 R⊙ (EW) and 1.0-1.4 R⊙ (NS). The agreement between results from different frequencies, in the ranges of r where there is overlapping shows the robustness of the method. The electron temperature, in turn, can be derived from the comparison of the observed mean spectra on the disk with those predicted through transfer calculations from the density models derived from limb observations. Results: The widths of the brightness profiles that were averaged yearly have minima at cycle minimum (2008-2009). These minima are more pronounced for EW profiles than for NS ones. The derived yearly-averaged density models along equatorial and polar diameters are consistent with isothermal and hydrostatic models. They are characterized by their density value n0 extrapolated down to the base of the corona and their scale-height temperature TH. Changes in n0 and TH with solar cycle are given for equatorial and polar regions. The kinetic temperature Te of electrons in the corona (~0.62 MK) is found to be significantly less than TH (~1.5 MK). This implies an ion temperature Ti ~ 2.2 MK. Conclusions: The yearly-averaged variations of these models are less than the dispersion between models derived from other techniques, such as white light and EUV observations, partly because these two techniques

  9. Structural transitions in electron beam deposited Co-carbonyl suspended nanowires at high electrical current densities.

    PubMed

    Gazzadi, Gian Carlo; Frabboni, Stefano

    2015-01-01

    Suspended nanowires (SNWs) have been deposited from Co-carbonyl precursor (Co2(CO)8) by focused electron beam induced deposition (FEBID). The SNWs dimensions are about 30-50 nm in diameter and 600-850 nm in length. The as-deposited material has a nanogranular structure of mixed face-centered cubic (FCC) and hexagonal close-packed (HCP) Co phases, and a composition of 80 atom % Co, 15 atom % O and 5 atom % C, as revealed by transmission electron microscopy (TEM) analysis and by energy-dispersive X-ray (EDX) spectroscopy, respectively. Current (I)-voltage (V) measurements with current densities up to 10(7) A/cm(2) determine different structural transitions in the SNWs, depending on the I-V history. A single measurement with a sudden current burst leads to a polycrystalline FCC Co structure extended over the whole wire. Repeated measurements at increasing currents produce wires with a split structure: one half is polycrystalline FCC Co and the other half is graphitized C. The breakdown current density is found at 2.1 × 10(7) A/cm(2). The role played by resistive heating and electromigration in these transitions is discussed.

  10. Materials for high-density electronic packaging and interconnection

    NASA Technical Reports Server (NTRS)

    1990-01-01

    Electronic packaging and interconnections are the elements that today limit the ultimate performance of advanced electronic systems. Materials in use today and those becoming available are critically examined to ascertain what actions are needed for U.S. industry to compete favorably in the world market for advanced electronics. Materials and processes are discussed in terms of the final properties achievable and systems design compatibility. Weak points in the domestic industrial capability, including technical, industrial philosophy, and political, are identified. Recommendations are presented for actions that could help U.S. industry regain its former leadership position in advanced semiconductor systems production.

  11. Electronic Structure Methods Based on Density Functional Theory

    DTIC Science & Technology

    2010-01-01

    L. Nordström, L. Tongming, and B. Johansson, “Relativistic Effects on the Thermal Expansion of the Actinide Elements ”, Phys. Rev. B 42, 1990, p 4544...In-house 5b. GRANT NUMBER 5c. PROGRAM ELEMENT NUMBER 62102F 6. AUTHOR(S) Christopher F. Woodward (AFRL/RXLMD) 5d. PROJECT NUMBER 4347 5e...in valence electrons change the structure of the core electrons. For example in the actinides , where the f-electrons are coupled to the core states

  12. Preliminary analysis of coronal electron content measurements from spacecraft Helios A around first solar occultation

    NASA Technical Reports Server (NTRS)

    Edenhofer, P.; Esposito, P. B.; Martin, W. L.; Zygielbaum, A. I.; Hansen, R. T.; Hansen, S. F.; Lueneburg, E.

    1977-01-01

    Steady-state and dynamical features of the electron density distribution in the solar corona emerge from a preliminary analysis of Helios A electron content measurements. There are strong indications that correlations can be established with earth-bound K-coronagraph measurements.

  13. Density fluctuation measurements on the ATF (Advanced Toroidal Facility) using a two-frequency reflectometer

    SciTech Connect

    Anabitarte, E. . Inst. de Energias Renovables); Hanson, G.R.; Harris, J.H.; Wilgen, J.B.; Bell, J.D.; Dunlap, J.L.; Hidalgo, C.; Thomas, C.E.; Uckan, T. )

    1990-01-01

    A microwave reflectometer system has been installed and operated on the Advanced Toroidal Facility (ATF) to measure density fluctuations. This system consists of two individual reflectometers that use the same antenna system and operate in the 30- to 40-GHz band. This arrangement allows operation at two frequencies along the same radial chord so that radial coherence measurements are possible. During the initial operating period of the reflectometer, a correlation was observed between a change in the edge density fluctuation spectrum and a transition to improved confinement. Recently, local measurements of the density fluctuation spectra in electron-cyclotron-heated (ECH) plasmas has been shown to agree with Langmuir probe measurements at the edge. Furthermore, structure in the spectra has been observed in some ECH plasmas. 4 refs., 3 figs.

  14. Tuning the electron energy by controlling the density perturbation position in laser plasma accelerators

    SciTech Connect

    Brijesh, P.; Thaury, C.; Phuoc, K. T.; Corde, S.; Lambert, G.; Malka, V.; Mangles, S. P. D.; Bloom, M.; Kneip, S.

    2012-06-15

    A density perturbation in an underdense plasma was used to improve the quality of electron bunches produced in the laser-plasma wakefield acceleration scheme. Quasi-monoenergetic electrons were generated by controlled injection in the longitudinal density gradients of the density perturbation. By tuning the position of the density perturbation along the laser propagation axis, a fine control of the electron energy from a mean value of 60 MeV to 120 MeV has been demonstrated with a relative energy-spread of 15 {+-} 3.6%, divergence of 4 {+-} 0.8 mrad, and charge of 6 {+-} 1.8 pC.

  15. Current Density Measurements of an Annular-Geometry Ion Engine

    NASA Technical Reports Server (NTRS)

    Shastry, Rohit; Patterson, Michael J.; Herman, Daniel A.; Foster, John E.

    2012-01-01

    The concept of the annular-geometry ion engine, or AGI-Engine, has been shown to have many potential benefits when scaling electric propulsion technologies to higher power. However, the necessary asymmetric location of the discharge cathode away from thruster centerline could potentially lead to non-uniformities in the discharge not present in conventional geometry ion thrusters. In an effort to characterize the degree of this potential non-uniformity, a number of current density measurements were taken on a breadboard AGI-Engine. Fourteen button probes were used to measure the ion current density of the discharge along a perforated electrode that replaced the ion optics during conditions of simulated beam extraction. Three Faraday probes spaced apart in the vertical direction were also used in a separate test to interrogate the plume of the AGI-Engine during true beam extraction. It was determined that both the discharge and the plume of the AGI-Engine are highly uniform, with variations under most conditions limited to +/-10% of the average current density in the discharge and +/-5% of the average current density in the plume. Beam flatness parameter measured 30 mm from the ion optics ranged from 0.85 - 0.95, and overall uniformity was shown to generally increase with increasing discharge and beam currents. These measurements indicate that the plasma is highly uniform despite the asymmetric location of the discharge cathode.

  16. Current Density Measurements of an Annular-Geometry Ion Engine

    NASA Technical Reports Server (NTRS)

    Shastry, Rohit; Patterson, Michael J.; Herman, Daniel A.; Foster, John E.

    2012-01-01

    The concept of the annular-geometry ion engine, or AGI-Engine, has been shown to have many potential benefits when scaling electric propulsion technologies to higher power. However, the necessary asymmetric location of the discharge cathode away from thruster centerline could potentially lead to non-uniformities in the discharge not present in conventional geometry ion thrusters. In an effort to characterize the degree of this potential nonuniformity, a number of current density measurements were taken on a breadboard AGI-Engine. Fourteen button probes were used to measure the ion current density of the discharge along a perforated electrode that replaced the ion optics during conditions of simulated beam extraction. Three Faraday probes spaced apart in the vertical direction were also used in a separate test to interrogate the plume of the AGI-Engine during true beam extraction. It was determined that both the discharge and the plume of the AGI-Engine are highly uniform, with variations under most conditions limited to 10% of the average current density in the discharge and 5% of the average current density in the plume. Beam flatness parameter measured 30 mm from the ion optics ranged from 0.85 0.95, and overall uniformity was shown to generally increase with increasing discharge and beam currents. These measurements indicate that the plasma is highly uniform despite the asymmetric location of the discharge cathode.

  17. Comparison of measured and modelled negative hydrogen ion densities at the ECR-discharge HOMER

    SciTech Connect

    Rauner, D.; Kurutz, U.; Fantz, U.

    2015-04-08

    As the negative hydrogen ion density n{sub H{sup −}} is a key parameter for the investigation of negative ion sources, its diagnostic quantification is essential in source development and operation as well as for fundamental research. By utilizing the photodetachment process of negative ions, generally two different diagnostic methods can be applied: via laser photodetachment, the density of negative ions is measured locally, but only relatively to the electron density. To obtain absolute densities, the electron density has to be measured additionally, which induces further uncertainties. Via cavity ring-down spectroscopy (CRDS), the absolute density of H{sup −} is measured directly, however LOS-averaged over the plasma length. At the ECR-discharge HOMER, where H{sup −} is produced in the plasma volume, laser photodetachment is applied as the standard method to measure n{sub H{sup −}}. The additional application of CRDS provides the possibility to directly obtain absolute values of n{sub H{sup −}}, thereby successfully bench-marking the laser photodetachment system as both diagnostics are in good agreement. In the investigated pressure range from 0.3 to 3 Pa, the measured negative hydrogen ion density shows a maximum at 1 to 1.5 Pa and an approximately linear response to increasing input microwave powers from 200 up to 500 W. Additionally, the volume production of negative ions is 0-dimensionally modelled by balancing H{sup −} production and destruction processes. The modelled densities are adapted to the absolute measurements of n{sub H{sup −}} via CRDS, allowing to identify collisions of H{sup −} with hydrogen atoms (associative and non-associative detachment) to be the dominant loss process of H{sup −} in the plasma volume at HOMER. Furthermore, the characteristic peak of n{sub H{sup −}} observed at 1 to 1.5 Pa is identified to be caused by a comparable behaviour of the electron density with varying pressure, as n{sub e} determines

  18. Nonlinear Upshift of Trapped Electron Mode Critical Density Gradient: Simulation and Experiment

    NASA Astrophysics Data System (ADS)

    Ernst, D. R.

    2012-10-01

    A new nonlinear critical density gradient for pure trapped electron mode (TEM) turbulence increases strongly with collisionality, saturating at several times the linear threshold. The nonlinear TEM threshold appears to limit the density gradient in new experiments subjecting Alcator C-Mod internal transport barriers to modulated radio-frequency heating. Gyrokinetic simulations show the nonlinear upshift of the TEM critical density gradient is associated with long-lived zonal flow dominated states [1]. This introduces a strong temperature dependence that allows external RF heating to control TEM turbulent transport. During pulsed on-axis heating of ITB discharges, core electron temperature modulations of 50% were produced. Bursts of line-integrated density fluctuations, observed on phase contrast imaging, closely follow modulations of core electron temperature inside the ITB foot. Multiple edge fluctuation measurements show the edge response to modulated heating is out of phase with the core response. A new limit cycle stability diagram shows the density gradient appears to be clamped during on-axis heating by the nonlinear TEM critical density gradient, rather than by the much lower linear threshold. Fluctuation wavelength spectra will be quantitatively compared with nonlinear TRINITY/GS2 gyrokinetic transport simulations, using an improved synthetic diagnostic. In related work, we are implementing the first gyrokinetic exact linearized Fokker Planck collision operator [2]. Initial results show short wavelength TEMs are fully stabilized by finite-gyroradius collisional effects for realistic collisionalities. The nonlinear TEM threshold and its collisionality dependence may impact predictions of density peaking based on quasilinear theory, which excludes zonal flows.[4pt] In collaboration with M. Churchill, A. Dominguez, C. L. Fiore, Y. Podpaly, M. L. Reinke, J. Rice, J. L. Terry, N. Tsujii, M. A. Barnes, I. Bespamyatnov, R. Granetz, M. Greenwald, A. Hubbard, J. W

  19. Device and method for electron beam heating of a high density plasma

    DOEpatents

    Thode, Lester E.

    1981-01-01

    A device and method for relativistic electron beam heating of a high density plasma in a small localized region. A relativistic electron beam generator produces a high voltage electron beam which propagates along a vacuum drift tube and is modulated to initiate e