Diagnostic Measured Sensitivity Method Remarks
1 Continuous thrust stand, pulsed thrust stand* Continuous and pulsed thrust 0.5 mN cont.; 5 µN‑s pulsed Inverted pendulum continuous; Pendulum pulsed Range: 1–300 mN, 10−2 s resolution cont.; 5 µN-s –1.0 mN-s
2 Telemicroscopy Grid deflection, thruster erosion 17 µm Telemicroscope/CCD camera All instruments outside vacuum chamber
3 Grid erosion Grid hole enlargement 5 µm Mechanical/optical Grid diameters < 30 cm
4 Faraday probe Fast ion flux 1 nA/cm2 Reject low energy ions Far-field angular distribution
5 Ion energy probe Energy and charge-state distributions < 20 eV Time-of-flight parallel-plate electrostatic deflector Far-field angular distribution
6 Langmuir probe Plasma potential, electron density & temperature, ion flux 107/cm3 Internally heated wire probe Minimize probe surface contaminants
7 Calorimeter* Total heat flux 20 W/sr Instrumented copper disk Far-field angular distribution
8 Beam profiler Ion flux contour maps 1 mm resolution Ion current collected by long wire Near-field ion current map
9 Quartz microbalance Erosion/deposition rate 2 X 10−9 g/cm2‑s Mass accumulation Positioned 360° around thruster
10 Ion-beam surface effects Composition of deposits, deposit/erosion rates Submonolayer Material coupons arrayed in the far-field plume Destructive testing technique
11 Thrust vector tracking* Ion-beam centroid 0.01° resolution, 0.1° accuracy Cruciform wire probe, thruster positioning system < 1 second time response
12 Single photon near-infrared LIF Xe and Xe+ velocity vector 50 m/s Doppler profile of infrared absorption/visible fluorescence Near-field map of axial, radial, azimuthal velocity; 0.5 mm spatial resolution
13 Two photon UV LIF* Xe density; H and H2 density, velocity, temperature (kinetic, rotational, vibrational) 1010–1012 cm−3 UV absorption/ visible fluorescence, Doppler profile Near-field map; 0.5 mm spatial resolution, rotational & vibrational temperature also measurable
14 Single photon visible/UV LIF Velocity, temp, density: Xe, Xe+ NH, Mo, Ti, W, B, Ba, etc. 105 cm−3 in favorable cases Doppler profile of visible or UV absorption/ visible flouresc. Near-field map; 0.5 mm spatial resolution
15 Extreme UV absorption* H2 density, dissociation fraction, rotational and vibrational temperature 8 X 1012 cm−3; 250 K Line-integrated extreme UV laser absorption Configured for centerline traversal only
16 Visible absorption* Absolute Ba, Ba+, Xe+ density 106 cm−3 in favorable cases FM spectroscopy, Doppler profile Near-field map, submillimeter spatial resolution
17 Magnetic field Map of magnetic induction 0.1 Gauss Hall probe Measured on stagnant thruster
18 Optical emission Plume signature, erosion species identification Varies with species Spectrograph/CCD Single point and line imaging
19 Mass/velocity analyzer* Velocity distribution for 6 masses simultaneously 2%/5% Time-of-flight mass spectrometer with position sensitive detection Far-field angular distribution for pulsed thrusters
20 CARS* H2 velocity and translational temperature 200 m/s; 20% Doppler shift/linewidth using single frequency CARS 35 X 350 µm spatial resolution; minimum density of 5 X 1015 cm−3
21 EMC* Electromagnetic emissions Near thermal noise HP 8572A receiver; fiberglass vacuum tank; semi-anechoic room MIL-STD 461/462D 100 MHz to 18 GHz
22 Microwave interferometer Electron density 108–109 cm−3 Microwave absorption and interferometry Near-field nonintrusive measurement, 2–4 cm spatial resolution
23 Infrared imager Thermal flux and temperature maps 300–900 K
±10 K		 Infrared camera 128 X 128 pixel resolution; 2–4 µm spectral band
24 Quadrupole mass spectrometry* Mass-selected velocity distributions of neutral species Down to single ion counting Differentially pumped mass spectrometer with chopper wheel Far-field angular distributions of mass flux, momentum flux, and energy flux
*Aerospace Corporation unique application or approach

A comprehensive list of diagnostic capabilities developed at aerospace for electric thruster test and evaluation.

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