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Diagnostics

The Electric Propulsion Laboratory at JPL maintains a multitude of diagnostics to assess thruster performance and plasma properties, including thrust stands, plasma probes, and optical diagnostics. These diagnostic capabilities are described in more detail below. Contact the Electric Propulsion Group supervisor for further details.

Diagnostics in the Micropropulsion Lab

  • Nano-Newton Thrust Stand (nNTS) The Nano-Newton Thrust Stand (nNTS) is capable of < 0.5 uN resolution thrust measurements for thruster assemblies that weigh up to 500 g.

  • Contamination Diagnostics Temperature controlled Quartz Crystal Microbalance (TQCM) with ~ng/cm^2/hr resolution

  • Beam Target Porous beam target to prevent facility effects (back sputtering, charge effects, etc)

  • Faraday Probes

  • Retarding Potential Analyzer (RPA)

  • Time of Flight (TOF) probe

  • High voltage, low current electrometers up to 10 kV, pA resolution

  • Scanning electron microscope with energy dispersive x-ray spectroscopy (SEM/EDS)

  • Class 100 clean room

Diagnostics in the Owens Chamber

  • Thrust Stand
    • High-resolution inverted pendulum thrust stand available for measurements between 1 mN and 1 N
    • Hofer, R. R. and Anderson, J. R., "Finite Pressure Effects in Magnetically Shielded Hall Thrusters," AIAA Paper 2014-3709, July 2014.

  • Laser Induced Fluorescence (LIF) ion velocimetry
    • To determine time-averaged and time-resolved ion velocity distributions in the thruster plume
    • Chaplin, V.H., Jorns, B.A., Lopez Ortega, A., Mikellides, I.G., Conversano, R.W., Lobbia, R.B., and Hofer, R.R. “Laser-induced fluorescence measurements of acceleration zone scaling in the 12.5 kW HERMeS Hall thruster,” Journal of Applied Physics 124, 183302 (2018); https://doi.org/10.1063/1.5040388
    • Chaplin, V.H., Lobbia, R.B., Lopez Ortega, A., Mikellides, I.G., Hofer, R.R., Polk, J.E., and Friss, A.J. “Time-resolved ion velocity measurements in a high-power Hall thruster using laser-induced fluorescence with transfer function averaging,” Applied Physics Letters 116, 234107 (2020)

  • Near-field, high-speed ion current density, emissive, and Langmuir probes
    • These probes describe plasma properties (ion current density, plasma potential, and electron temperature) near the thruster exit plane
    • Hofer, R. R., Goebel, D. M., Mikellides, I. G., and Katz, I., "Magnetic Shielding of a Laboratory Hall Thruster Part II: Experiments," Journal of Applied Physics 115, 043303 (2014).
    • Jorns, B., Hofer, R. R., and Mikellides, I. G., "Power Dependence of the Electron Mobility Profile in a Hall Thruster," AIAA Paper 2014-3620, July 2014.

  • Far field probes (ExB, RPA, Faraday, Langmuir)
    • These probes describe plasma properties (ion charge-to-mass ratio, ion energy, ion current density, and electron temperature) far from the thruster exit plane
    • Hofer, R. R., Goebel, D. M., Mikellides, I. G., and Katz, I., "Design of a Laboratory Hall Thruster with Magnetically Shielded Channel Walls, Phase II: Experiments," AIAA-2012-3788, July 2012.

  • Flush-mounted wall probes
    • These probes measure plasma properties (ion current density, plasma potential, and electron temperature) at the facility wall to help in determining facility effects
    • Hofer, R. R., Goebel, D. M., Mikellides, I. G., and Katz, I., "Design of a Laboratory Hall Thruster with Magnetically Shielded Channel Walls, Phase II: Experiments," AIAA-2012-3788, July 2012.

  • Xenon-calibrated ionization gauges mounted at thruster exit plane

  • Thrust vector probe

Other Diagnostics

  • Environmental Testing
    • Thermal vacuum testing is accomplished with a large thermal shroud for testing over temperatures of -140 to >450 degrees C.
    • Vibration and shock testing is also available in the Environmental Test Lab at JPL.
    • Snyder, J. S., Anderson, J. R., Van Noord, J. L., and Soulas, G. C., "Environmental Testing of Nasa’s Evolutionary Xenon Thruster Prototype Model 1 Reworked Ion Engine," Journal of Propulsion and Power 25, 1, 94-104 (2009).
    • Lobbia, R.B., Conversano, R.W., Reilly, S., Hofer, R.R., and Sorensen, R. “Environmental Testing of the HERMeS TDU-2 Hall Thruster,” AIAA Propulsion and Power Forum, Cincinnati, OH, Jul 9-11 2018. DOI: 10.2514/6.2018-4646
  • Surface profilometry (CMM and Nanovea) – to assess erosion and deposition on thruster or other component surfaces
    • Coordinate measuring machine (30 um resolution)
    • Hofer, R. R., Jorns, B. A., Polk, J. E., Mikellides, I. G., and Snyder, J. S., "Wear Test of a Magnetically Shielded Hall Thruster at 3000 Seconds Specific Impulse," Presented at the 33rd International Electric Propulsion Conference, IEPC-2013-033, Washington, DC, Oct 6-10, 2013.
    • Nanovea ST-400 non-contact surface profiler (1 um resolution, 20 mm depth-of-field, 3-axis motion control)
    • Sekerak, M., Hofer, R. R., Polk, J. E., Jorns, B. A., and Mikellides, I. G., "Wear Testing of a Magnetically Shielded Hall Thruster at 2000 S Specific Impulse," Presented at the 34th International Electric Propulsion Conference, IEPC-2015-155, Kobe, Japan, July 4-10, 2015.
  • FLIR Infrared Camera
    • To determine thermal distribution during operation
    • Hofer, R. R., Jorns, B. A., Polk, J. E., Mikellides, I. G., and Snyder, J. S., "Wear Test of a Magnetically Shielded Hall Thruster at 3000 Seconds Specific Impulse," Presented at the 33rd International Electric Propulsion Conference, IEPC-2013-033, Washington, DC, Oct 6-10, 2013.
  • FASTCAM S1
    • High speed (650 kfps) visual camera used to evaluate dynamic behavior across the thruster face
    • Jorns, B. A. and Hofer, R. R., "Plasma Oscillations in a 6-kW Magnetically Shielded Hall Thruster," Physics of Plasmas 21, 5, 053512 (2014).
  • 3-axis Gaussmeter
    • Lakeshore 460 with automated data acquisition and motion control
  • Fast Scanning Pyrometer System for cathode life assessment
    • Noncontact temperature measurement technique for hollow cathode inserts using ratio pyrometry used to determine axial temperature profile
    • Polk, J. E., Marrese-Reading, C. M., Thornber, B., Dang, L., Johnson, L. K., and Katz, I., "Scanning Optical Pyrometer for Measuring Temperatures in Hollow Cathodes," Review of Scientific Instruments 78, 093101 (2007).
  • Optical emission spectroscopy
    • Chaplin, V.H., Johnson, L.K., Lobbia, R.B., Konopliv, M.F., Simka, T., and Wirz, R.E. “Insights from Collisional-Radiative Models of Neutral and Singly Ionized Xenon in Hall Thrusters,” Journal of Propulsion and Power 38(5) (2022). DOI: https://doi.org/10.2514/1.B38676
  • Gamma radiation diagnostics
    • High sensitivity erosion measurements using radioactive tracers
    • Polk, J. E., Lobbia, R., Barriault, A. and Guerrero Vela, P. P., “Use of an accelerated testing method to characterize inner front pole cover erosion in a high-power Hall thruster,” Journal of Applied Physics, 130(18) 183302 (2021), doi: 10.1063/5.0067452.
  • Research-grade Hiden mass spectrometer/energy analyzer
    • Polk, J. E., Lobbia, R., Barriault, A. and Guerrero Vela, P. P., “Use of an accelerated testing method to characterize inner front pole cover erosion in a high-power Hall thruster,” Journal of Applied Physics, 130(18) 183302 (2021), doi: 10.1063/5.0067452.
  • High speed scanning Langmuir probes for hollow cathode internal plasma measurements.
    • Polk, J.E. and Lobbia, R.B., “The Effect of Time-Varying Currents on Hollow Operation,” IEPC-2022-146, 37th International Electric Propulsion Conference, 2022, and Goebel, D.M., et al., “Hollow cathode theory and experiment. I. Plasma characterization using fast mini fast miniature scanning probes,” Journal of Applied Physics 98, 113302 (2005); doi: 10.1063/1.2135417
  • LabView control to automate and control experiments and collect data
  • Current probes to measure discharge voltage/current oscillations in the Hall thruster
  • Thermocouples
    • The EP labs at JPL have a variety of thermocouples suited to different operating regimes (type K, type C, type R, etc).
  • Quartz Crystal Microbalance (QCM)
    • To measure carbon backsputter rate
  • Residual Gas Analyzer (RGA)

CL#24-0850