Fast-sweeping Langmuir probes: what happens to the I-V trace when sweeping frequency is higher than the ion plasma frequency?

2021 ◽  
Author(s):  
Chenyao Jin ◽  
Chi-Shung Yip ◽  
Wei Zhang ◽  
Di Jiang ◽  
Guosheng Xu
Keyword(s):  
Langmuir Probe ◽  
High Speed ◽  
Plasma Frequency ◽  
Limiting Factors ◽  
Langmuir Probes ◽  
Weak Current ◽  
Shunt Resistance ◽  
Ion Motion ◽  
Single Probe ◽  
Ion Plasma

Abstract Limited particle transit time is one of several limiting factors which determines the maximum temporal resolution of a Langmuir probe. In this work, we have revisited known fast sweep Langmuir probe techniques in a uniform, quiescent multi-dipole confined hot cathode discharge with two operation scenarios: one in which the probe sweeping frequency fsweep is much lower than the ion plasma frequency fpi, another one where fsweep is much greater than fpi, respectively. This allows the investigation of the effect of limited ion-motion on I-V traces. Serious distortions of I-V traces at high frequencies, previously claimed to be ion-motion limitation effect, was not found in the degree previously claimed unless shunt resistance is sufficiently high, despite achieving a ratio of ~ 3 between the probe sweeping frequency and the ion plasma frequency. On the other hand, evidences of sheath capacitance on the I-V trace have been observed. Distortions of I-V traces qualitatively agrees with predictions of sheath capacitance response to the sweeping voltage. Additionally, techniques in fast sweep Langmuir probe are briefly discussed. The comparison between a High-speed dual Langmuir probe (HDLP) and the single probe setup shows that the capacitive response can be removed via subtracting a leakage current for the single probe setup almost as effective as using an HDLP setup, but the HDLP setup does remain advantageous in its facilitation of better recovery of weak current signal common in low plasma density situations.

A Comparison of Two Collision Detection Libraries in a Haptic Simulation Environment

2004 ◽  
Author(s):  
Adam S. Coutee ◽  
Bert Bras
Keyword(s):  
Virtual Environment ◽  
Collision Detection ◽  
High Speed ◽  
Limiting Factors ◽  
Simulation Environment ◽  
Assembly Sequences ◽  
High Speed Collision ◽  
Dynamic Objects ◽  
Haptic Simulation

Modeling the interaction between dynamic objects in a haptically enabled virtual environment requires high-speed collision detection. We present an independent comparison of two publicly available collision detection libraries, V-Clip and SWIFT++, as they perform in our assembly and disassembly simulation. Three assembly sequences, differing only by the complexity of the objects involved, are tested and compared based on speed of execution. In the process, some potentially limiting factors experienced while using these libraries are exposed.

Development of Particulate Unit Operations and Morphology Property Relations of Particulate Products

2007 ◽  
Author(s):  
Yasumasa Takao ◽  
Tsuyoshi Asai ◽  
Yasuhiro Shimada ◽  
Kiyotaka Shuzenji ◽  
Takeshi Tachibana
Keyword(s):  
Reaction Temperature ◽  
High Speed ◽  
Plasma Heating ◽  
Particle Morphology ◽  
Limiting Factors ◽  
Flame Synthesis ◽  
Aluminum Oxynitride ◽  
Low Oxygen ◽  
Oxide Powders ◽  
Unit Operations

Some particulate unit operations (apparatus engineering) are developed to control the particle morphology. The innovative aspect of this operation is the correspondence between the necessary material properties and their apparatus optimization. Spherical powders of aluminum oxynitride and aluminum nitride are directly prepared by flame synthesis (in spite of the fact that oxygen serves as an indispensable reactant). Non-oxide powders are commonly non-spherical with a size below the submicrometer scale. The major limiting factors in their synthesis are free energy, reaction temperature, and reaction rate. The innovative aspect of this flame synthesis technology assisted by DC arc plasma concerns the reducing gas composition beyond 1500 K. A chemical equilibrium calculation indicates that the plasma heating compensates the lack of reaction temperature under a low oxygen condition. This burner realizes a high-speed reaction with the help of reactive species in the arcs. We also report the multilayer-coated cosmetic powders with regard to material application, and the powder bed shear force evaluation equipment with regard to apparatus optimization.

Swarm Langmuir Probe measurements : analysis and characterization of the data quality

2020 ◽  
Author(s):  
Filomena Catapano ◽  
Stephan Buchert ◽  
Igino Coco ◽  
Ewa Slominska ◽  
Enkelejda Qamili ◽  
...  
Keyword(s):  
Langmuir Probe ◽  
Langmuir Probes ◽  
Spacecraft Potential ◽  
Earth Environment ◽  
Langmuir Probe Measurements ◽  
The Magnetic Field ◽  
Probe Measurements ◽  
Electric Field Instrument

<p>Swarm is a three-satellite constellation mission launched by ESA in 2013 flying at an altitude of about 510 km for Swarm Bravo, and 460 km for Alpha and Charlie. The three satellites carry identical instruments continuously collecting ground-breaking data on the various components of the magnetic field and on the near-Earth environment and their dynamics. The Electric Field Instrument (EFI)  is composed by the Thermal Ion Imager (TII) and two Langmuir Probes (LPs) which measure the electron density, temperature and spacecraft potential with the cadence of 2Hz. The scope of this work is to provide an updated status of the L1B data derived from LP measurements, describing some of anomalies affecting the data products as well the outcomes of recent investigations aiming at further improving the science quality of the LP-based Swarm data.</p>

A Double Hemispherical Probe for the Advancement of In Situ Plasma Measurements

2020 ◽  
Author(s):  
Joseph Samaniego ◽  
Xu Wang
Keyword(s):  
Langmuir Probe ◽  
High Surface ◽  
Low Density ◽  
Saturation Current ◽  
Langmuir Probes ◽  
Plasma Parameters ◽  
Ambient Plasma ◽  
Surface Emission ◽  
Plasma Measurements

<p>Langmuir probes are conductors of simple geometries (spheres, disks, cylinders, etc.) inserted into a plasma. By sweeping a voltage on the probe and measuring the current collected or emitted, a current-voltage (I-V) relationship can be found and interpreted to derive the density, temperature, and potential of the ambient plasma. Over the past 50 years, Langmuir probes have been flown on spacecraft missions for in-situ measurements of the local plasma environment. However, even after decades of use, there are still challenges in the analysis and interpretation of Langmuir probe measurements due to local plasmas created around the probe as a result of plasma interactions with the probe itself and spacecraft.</p><p>The Double Hemispherical Probe (DHP) is a directional Langmuir probe made of two hemispheres that are electrically isolated from each other and swept with a voltage together to get two separate I-V curves. The DHP uses the I-V curve differences between the two hemispheres to gain information of the asymmetry of the local plasma around the probe to retrieve the true ambient plasma parameters. Specifically, the DHP is intended to improve the plasma measurements in the following scenarios: i) Low-density plasmas; ii) flowing plasmas; iii) high-surface-emission environments; and iv) dust-rich plasmas. The following discusses the current progress of the DHP development.</p><p>Low-density plasmas create large Debye sheaths around the spacecraft that may engulf the Langmuir probe attached to a boom with a finite length. The potential drop in the sheath can change the characteristics of charged particles collected by the probe, causing mischaracterization of the ambient plasma. As expected, the I-V curves of both hemispheres match in the bulk plasma. It was found that as the DHP is moved ‘deeper’ into the sheath of the spacecraft, the currents of the two hemispheres diverge. The saturation current ratio of the hemispheres of the DHP was found to have monotonic relationships with the plasma characteristics measured in the sheath. A technique was created to retrieve the ambient plasma parameters.</p><p>In space ions generally have relative velocities with respect to the spacecraft due to flowing plasmas or fast-moving spacecraft, creating an ion wake behind the probe itself. This self-wake can cause issues in interpreting the I-V curves for both ion and electron species. The ion saturation current of either hemisphere of the DHP is dependent on the ion Mach number (the ratio of the ion flow speed to the thermal speed). Electrons are generally in the thermal state. However, depending on the ratio of the probe size to the Debye length, ambipolar electric fields can be created at the wake boundaries, causing the reduction of the electron density in the downstream side of the probe and its subsequent underestimation measured by traditional single Langmuir probes. It was shown that the DHP can identify this self-wake effect and properly measure the true ambient plasma parameters.    </p><p>Future work will explore the effects of high-surface-emission environments and dust-rich plasmas on DHP measurements and to develop techniques to resolve the true ambient plasma parameters in these environments. </p>

Synthesis and properties of an electron-ion plasma

1961 ◽  
Vol 264 (1318) ◽  
pp. 355-366
Keyword(s):  
Plasma Frequency ◽  
Electron Velocity ◽  
Signal Frequency ◽  
Electric Signal ◽  
Lithium Aluminium ◽  
Ion Plasma ◽  
Free Region ◽  
Field Free Region ◽  
Field Lines ◽  
Singly Charged

It is shown that a low-density neutral plasma in a steady state, consisting of electrons and ions only, can be obtained by injecting opposing beams of charges into a field-free region. With the aid of electrostatic probes the electric neutrality of such a synthetic plasma can be controlled. Experiments were carried out with a plasma consisting of singly charged lithium ions of energy up to 300 eV drawn from a lithium-aluminium silicate emitter and electrons of energy 12 to 24 eV drawn from a dispenser cathode. The residual gas pressure was kept so low that collision with atoms did not contribute to the effects measured. A continuous electric signal of frequency 2 to 30 Mc/s was transmitted through the plasma. Whereas in a gaseous plasma a resonance peak at the plasma frequency was found by varying either the signal frequency or the discharge current (and thus the plasma frequency), a resonance absorption was recorded in an electron-ion plasma. This suggests that for frequencies lower than that corresponding to an individual electron crossing the region of influence of the signal the phase of the electron oscillation always tends to reduce the local field. As the electron velocity was raised the magnitude of absorption was shown to grow. The transmission in the electron-ion plasma was also studied with a magnetic field parallel to the direction of the beams which caused the electrons to circulate about the field lines. By varying the field strength the absorption was found to reach a maximum when the electron cyclotron frequency equals the plasma frequency. The width of the absorption curves for the electron-ion plasma was greater than that with an electron beam only. The interaction between ions and electrons has been demonstrated by measuring the electric noise produced by the plasma. For electron energies between 10 and 70 eV the increase in noise corresponds to a change of the electron temperature by 400 to 500 °K or to an average scattering angle of 1 to 3°.

scholarly journals Determination of the averaged charge-to-mass ratio of the heavy charged constituents of a magnetoplasma using whistler wave measurements

2010 ◽  
Vol 28 (12) ◽  
pp. 2237-2247 ◽  
Author(s):  
C. Krafft ◽  
B. V. Lundin
Keyword(s):  
Plasma Frequency ◽  
Magnetized Plasma ◽  
Charged Dust ◽  
Mass Ratio ◽  
Cutoff Frequencies ◽  
Wave Measurements ◽  
Ion Plasma ◽  
Light Ions ◽  
Spectrometer Data

Abstract. In a cold magnetized plasma with two light ions of comparable gyrofrequencies and any species of heavy ions and/or charged dust particulates, a technique is developed to recover the relative charge density of the heavy plasma population and to estimate its effective averaged charge-to-mass ratio. Such results can be obtained without using mass spectrometer data but only the measurements of the ion plasma frequency, the electron gyro- and plasma frequencies as well as the two highest ion cutoff frequencies.

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