HPEPL employs a wide-range of plasma probe diagnostics and facility measurement techniques. HPEPL also employs a rigorous probe calibration and check-out procedure to accurately define the uncertainty of each measurement.
Terahertz time-domain spectroscopy (THz-TDS) is a method by which material or plasma properties are determined through measurement of attenuation and refraction of broadband pulsed THz radiation in media.
Quartz crystal microbalances (QCMs) are devices used to measure the rate of mass deposition per unit area by correlating changes in the measured frequency of an exposed quartz crystal resonator to a corresponding change in crystal mass.
A null-type stand differs from other inverted pendulum thrust stands in that it actively holds the thrust stand in a nearly stationary position at all thrust levels. This eliminates changes in the elevation angle of the thrust vector and reduces error in the thrust measurement.
This thrust stand makes accurate measurements of thrust for devices operating in a pulsed mode. Many high-power thruster concepts such as magnetoplasmadynamic thrusters and pulsed inductive thrusters operate in short pulses.
This Langmuir probe employs both a floating electrode immediately adjacent to the probe tip and multiple RF chokes to facilitate measurements of electron number density and electron temperature in RF plasmas. Example RF plasmas include capacitively-coupled, inductively-coupled, and helicon discharges.
Faraday probes provide a measurement of ion current density. The measurement is often performed in angular sweeps across the thruster plume to quantify the divergence angle of the thruster plume. The probe pictured is modeled on the JPL nude Faraday probe design.
A Retarding Potential Analyzer directly measures ion energy distribution by quantifying their ability to migrate across a biased grid. Three other grids provide shielding from the plasma and repulsion/suppression of electrons.
HPEPL has developed a novel method for propellant flow characterization employing a premixed flame stabilized on the exit plane of the propellant distributor. This technique yields immediate visual feedback on the flow through the propellant distributor by making spatial nonuniformities in mass flow rate visible. A quantitative measure of the uniformity can be obtained by examination of the flame luminosity and its variability in circumferential and radial directions.