Evaluation of ion collection area in Faraday probes

Brown, Daniel L.; Gallimore, Alec D.

doi:10.1063/1.3449541

Cited by 33 publications

(29 citation statements)

References 12 publications

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“…26 Ion current densities in the exhaust plume are obtained using measurement sweeps of a Faraday probe (FP). 27 The current collecting surface of the probe is mounted flush within a guard-ring, which is used to minimize the error due to sheath effects on the collection area. Current is collected through a shunt resistor for probe and guard-ring bias voltages of −30 V.…”

Section: Iib Plasma Diagnosticsmentioning

confidence: 99%

Influence of the Applied Magnetic Field Strength on Flow Collimation in Magnetic Nozzles

Little¹,

Choueiri²

2014

50th AIAA/ASME/SAE/ASEE Joint Propulsion Conference

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The influence of the magnetic field strength on the collimation of the plasma flow in an electron-driven magnetic nozzle is investigated experimentally. A collimated plasma flow is required for efficient plasma propulsion to minimize plume divergence losses. Faraday probe measurements are used to estimate the ion streamlines in the diverging field of the magnetic nozzle. It is found that decreasing the strength of the applied magnetic field invokes a transition from a collimated plume to an under-collimated plume, where an under-collimated plume is defined such that the plume divergence is greater than the magnetic field divergence. Langmuir and emissive probe measurements reveal that the transition to an under-collimated plume is accompanied by anomalous deceleration of the ion beam along the nozzle centerline, broadening of the transverse density profile, and the disappearance of an ion-confining potential well at the plasma periphery. This transition offers a guideline for reducing the plume divergence of an electron-driven magnetic nozzle.

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Section: Iib Plasma Diagnosticsmentioning

confidence: 99%

Influence of the Applied Magnetic Field Strength on Flow Collimation in Magnetic Nozzles

Little¹,

Choueiri²

2014

50th AIAA/ASME/SAE/ASEE Joint Propulsion Conference

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“…The integrate current density from the Faraday probe allows determination of the plume divergence angle following the procedures outlined by Brown and Gallimore. 19,20 The plume divergence angle for the conditions shown here is given in Table I.…”

Section: Discussionmentioning

confidence: 99%

“…The beam current and plume divergence angle are determined from Faraday probe measurements according to the technique developed by Brown and Gallimore. 19,20 The uncertainty in the plume angle and beam current are 65%. The ion energy systematic error is 65.3 V.…”

Section: Discussionmentioning

confidence: 99%

Potential contour shaping and sheath behavior with wall electrodes and near-wall magnetic fields in Hall thrusters

Dao

Walker

2012

Physics of Plasmas

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Graphite electrodes are embedded within the discharge channel of a Hall effect thruster to focus ions for improved performance. Cusp-shaped magnetic fields are added around the electrodes to shield the electrodes from high electron current. Internal plasma potential measurements inside the discharge channel show that the presence of floating graphite does not significantly affect the potential contours at 150 V anode potential. Creation of closed contour pockets are observed with the electrodes biased 10 and 30 V above the anode potential. The electrodes also cause a compression of the acceleration region in the thruster. The cause of the changes in the potential contours is attributed to a shifting of discharge electrode from the anode to the electrodes and an expansion of the near-wall plasma sheath. The presence of the cusp magnetic fields is shown to affect the current collected by the electrodes, a behavior associated with modification of the plasma sheath properties due to magnetization of electrons. V C 2012 American Institute of Physics. [http://dx.

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“…This Faraday probe is described in detail by Liang and Gallimore, 21 and is modeled after the nested Faraday probe design described by Brown and Gallimore. 24 The Faraday probe was mounted to a rotation stage such that it could move in an arc about the HHT exit plane. To take data, the guard ring and both collectors are biased at -30 V with respect to facility ground into ion saturation.…”

Section: Faraday Probementioning

confidence: 99%

Performance of a Helicon Hall Thruster Operating with Xenon, Argon, and Nitrogen

Shabshelowitz

Gallimore²,

Peterson

2012

48th AIAA/ASME/SAE/ASEE Joint Propulsion Conference &Amp;amp; Exhibit

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The Helicon Hall Thruster (HHT) is a two-stage thruster that was developed to investigate whether a radiofrequency ionization stage can improve the overall efficiency of a Hall thruster operating at high thrust and low specific impulse. This experiment measured the single-stage and two-stage performance of the HHT for 10-25 mg/s anode mass flow rates of xenon at 100-200 V discharge voltages, and also for 6 mg/s of argon at 300 V, and 2.6 mg/s of nitrogen at 200 V. Argon and nitrogen performance are characterized by low beam divergence efficiency and low propellant utilization efficiency. During two-stage operation, the thrust of the HHT increased slightly with rf power, but the propulsive efficiency and thrust-to-power both decreased with increasing rf power. Probe diagnostics suggest that gains were realized by a slight increase in propellant efficiency, but that the rate of increase was not sufficient to overcome the increase in power. NomenclatureA c,eff = Faraday probe effective collection area [m 2 ] e = elementary charge [C] E 1 = voltage exchange parameter [-] E 2 = mass exchange parameter [-] = Faraday constant [C/mol] I axial = axial component of ion beam current [A] I beam = ion beam current [A] I c = current collected by probe [A] I d = discharge current [A] I sp,a = anode specific impulse [s] I sp,a + = theoretical anode specific impulse of a singly-charged plasma [s] = molar mass [kg/mol] m i = ion mass [kg] = total thruster mass flow rate [kg/s] = anode mass flow rate [kg/s] = cathode mass flow rate [kg/s] P d = discharge power [W] P elec = total electrical power [W] P dc = dc discharge power [W] P mag = magnet power [W] P rf = rf power [W] P thrust = jet power of thruster exhaust [W] 2 r = Faraday probe distance from thruster [m] T = measured thrust [N] T + = theoretical thrust of a thruster with singly-charged plasma [N] = average axial velocity of exhaust particle [m/s] V d = discharge voltage [V] V mp = most probable energy of exhaust ions [V] V p = plasma potential [V] = anode efficiency [-] = anode efficiency of a thruster with singly-charged plasma [-] = cathode efficiency [-] = discharge efficiency [-] = magnet power efficiency [-] = current utilization efficiency [-] = rf power efficiency [-] = total efficiency [-] = voltage utilization efficiency [-] θ = angular position of Faraday probe [radians] λ = effective exhaust divergence angle [degrees] = propellant utilization efficiency [-] = beam divergence efficiency [-]

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Evaluation of ion collection area in Faraday probes

Cited by 33 publications

References 12 publications

Influence of the Applied Magnetic Field Strength on Flow Collimation in Magnetic Nozzles

Influence of the Applied Magnetic Field Strength on Flow Collimation in Magnetic Nozzles

Potential contour shaping and sheath behavior with wall electrodes and near-wall magnetic fields in Hall thrusters

Performance of a Helicon Hall Thruster Operating with Xenon, Argon, and Nitrogen

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