Low work-function thermionic emission and orbital-motion-limited ion collection at bare-tether cathodic contact

Chen, Xin; Sanmartin, J. R.

doi:10.1063/1.4919945

Cited by 12 publications

(12 citation statements)

References 30 publications

(42 reference statements)

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“…6 from Ref. 34, thermionic emission increases the minimum radius R* and enlarges the parameter range for OML validity. Consequently, as I RD increases, the i-non-OML region (OP-7) shrinks.…”

Section: Qualitative Discussionmentioning

confidence: 73%

“…This actually explains why emission broadens the parameter range for OML validity. 34 For the density of repelled plasma electrons, due to…”

Section: Monotonic Potential With / P <0mentioning

confidence: 99%

“…33 Recently, by using boundary-layer techniques and kinetic modelling, a selfconsistent asymptotic solution was found for OML condition at high probe bias (je/ p j ) k B T e ). 34 Without a rigorous and universal kinetic description for cylindrical EPs, a wide variety of methods exist-yet commonly with controversies-to infer plasma potential from experimental data. 7 Contrary to the successful application of the LP I-V curves from Laframboise to interpret plasma parameters, 19 EP techniques have not been used to infer other plasma parameters other than plasma potential.…”

Section: Introductionmentioning

confidence: 99%

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Orbital motion theory and operational regimes for cylindrical emissive probes

Sánchez‐Arriaga

2017

Physics of Plasmas

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A full-kinetic model based on the orbital-motion theory for cylindrical emissive probes (EPs) is presented. The conservation of the distribution function, the energy, and the angular momentum for cylindrical probes immersed in collisionless and stationary plasmas is used to write the Vlasov-Poisson system as a single integro-differential equation. It describes self-consistently the electrostatic potential profile and, consequently, the current-voltage (I-V) probe characteristics. Its numerical solutions are used to identify different EP operational regimes, including orbital-motion-limited (OML)/non-OML current collection and monotonic/non-monotonic potential, in the parametric domain of probe bias and emission level. The most important features of the potential and density profiles are presented and compared with common approximations in the literature. Conventional methods to measure plasma potential with EPs are briefly revisited. A direct application of the model is to estimate plasma parameters by fitting I-V measurements to the theoretical results.

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Section: Qualitative Discussionmentioning

confidence: 73%

“…This actually explains why emission broadens the parameter range for OML validity. 34 For the density of repelled plasma electrons, due to…”

Section: Monotonic Potential With / P <0mentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Orbital motion theory and operational regimes for cylindrical emissive probes

Sánchez‐Arriaga

2017

Physics of Plasmas

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“…Furthermore, another major reason is that the lower work function of PrB 6 single crystal using a high‐density feed rod, which is caused by its higher crystal quality, contributes to improving the emission properties. The work function ( Φ ) of the as‐grown PrB 6 single crystals can be calculated by the Richardson–Dushman formula:

Φ = K T \ln (\frac{A T^{2}}{J_{0}})

, where K is Boltzmann constant ( K = 8.617 × 10 −5 eV K −1 ), T is the cathode temperature, A = 120.4 A cm −2 K −2 is the emission constant, J 0 is the zero field emission current density and can be obtained by the Schottky effect:

\lg J = \lg J_{0} + 0.191 U^{0.5} false(\frac{α^{0.5}}{T} false)

, where α is the experimental constant related to the cathode structure. Due to the linear dependence between lg J and U 0.5 in the region of high applied voltage, the J 0 can be obtained by extrapolating the curves of lg J versus U 0.5 to U 0.5 = 0.…”

Section: Resultsmentioning

confidence: 99%

Density of Feed Rod Dependence of the PrB₆ Single Crystal Grown by the Optical Floating Zone Technique

Wang

Zhao

Yang

et al. 2019

Crystal Research and Technology

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Rare-earth hexaboride single crystals praseodymium hexaboride (PrB 6 ) are successfully grown by the optical floating zone technique using the feed rods with different densities sintered by spark plasma sintering (SPS). Single crystal X-ray diffraction and transmission electron microscopy analysis have found that the as-grown PrB 6 adopts a single crystalline structure which has a primitive cubic structure, and has grown along the <100> direction. Particular attentions are given to the effect of density of feed rod on the crystal quality and thermionic emission performance of PrB 6 single crystals. The result of X-ray rocking curve indicates that the quality of the as-grown single crystals get better with increase in the density of feed rod, and an ultralow full-width at half-maximum of 0.066°, confirming the good crystal integrality, is resulted from the single crystal using the feed rod with relative density of 97.17%. Similarly, the result of thermionic emission shows that the PrB 6 single crystal grown here using a high-density feed rod has a large current density. The density of feed rod plays an important role in PrB 6 single crystal growth by the optical floating zone technique.

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“…Asymptotic analysis of the Vlasov-Poisson system for cylindrical emissive Langmuir probes in the high bias limit and probe radius R = R max to collect ions within the OML regime showed that, for ion, electron and probe temperatures satisfying T i = T e ≡ T = 4 T p = 0.1 eV, the full RD emission to SCL regime takes place at | * |/kT equal to 26.2, 89.7, 143.0, 238.8 for ν = 20, 50, 70, 100, or roughly [6],…”

Section: Negligible Scl Emission Regimementioning

confidence: 99%

Analysis of thermionic bare tether operation regimes in passive mode

2017

Self Cite

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A Thermionic Bare Tether (TBT) is a long conductor coated with a low work function material. Under drag mode, a tether segment extending from anodic end A to a zero-bias point B, with standard Orbital-motionlimited current collection and ohmic effects, is followed by a complex cathodic segment. In general, as bias becomes more negative in moving from B to cathodic end C, one first finds space-charge-limited emission covering up to some intermediate point B*, then full Richardson-Dushman emission reaching from B* to end C. An approximate analytical study, which combines current and voltage profile equations with results from asymptotic studies of the Vlasov-Poisson system for emissive probes. is carried out to determine the parameter domain covering two limit regimes. In one such regime no point B* is reached and thus no full R-D emission develops. In an opposite limit regime, segment BB* is too short to contribute significantly to current balance.

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Low work-function thermionic emission and orbital-motion-limited ion collection at bare-tether cathodic contact

Cited by 12 publications

References 30 publications

Orbital motion theory and operational regimes for cylindrical emissive probes

Orbital motion theory and operational regimes for cylindrical emissive probes

Density of Feed Rod Dependence of the PrB₆ Single Crystal Grown by the Optical Floating Zone Technique

Analysis of thermionic bare tether operation regimes in passive mode

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Low work-function thermionic emission and orbital-motion-limited ion collection at bare-tether cathodic contact

Cited by 12 publications

References 30 publications

Orbital motion theory and operational regimes for cylindrical emissive probes

Orbital motion theory and operational regimes for cylindrical emissive probes

Density of Feed Rod Dependence of the PrB6 Single Crystal Grown by the Optical Floating Zone Technique

Analysis of thermionic bare tether operation regimes in passive mode

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Density of Feed Rod Dependence of the PrB₆ Single Crystal Grown by the Optical Floating Zone Technique