Plasma & Space Propulsion Lab

The UCLA Plasma & Space Propulsion Lab is investigating the plasma processes in advanced space propulsion systems through a combined experimental, computational, and analytical approach.

Henry Huh McKenna Davis Richard Wirz

Recent advancements in electrospray thrusters have unveiled their extraordinary potential for a variety of aerospace applications. In particular, colloidal electrospray thrusters provide unprecedented thrust resolution and control over spacecraft position and orientation. Electrospray thrusters first flew in space in 2015 on the Space Technology 7 (ST7) mission, demonstrating nearly 2,500 hours of continuous operation. Their lifetime was limited by a myriad of factors including propellant deposition on grids inside the thruster and propellant decomposition.

Peter Wright Anirudh Thuppul Adam Collins

The Plasma and Space Propulsion Laboratory at UCLA is investigating advanced electrospray emitter concepts for high performance, long lifetime, and highly throttlable thrusters. In particular, the hybrid emitter geometry, which consists of a capillary emitter with a protruding coaxial needle, allows for variable performance depending on the state of the meniscus. This design takes advantage of the natural increase in specific charge of emission as current decreases to produce high specific impulse operation at low flow rate and high thrust-to-power operation at high flow rate.

Angelica Ottaviano Richard Wirz

The study of plasma-material interactions (PMI) is fundamental to improving the performance and lifetime of many electric propulsion (EP) devices. PMI processes such as ion-induced sputtering, sputter erosion, plasma contamination, and secondary electron emission (SEE) have a direct impact on important thruster parameters. Solving these PMI issues is necessary to develop and operate high-power thruster concepts, such as magnetoplasmadynamic (MPD) thrusters and advanced fusion propulsion concepts.

Zhitong Chen Richard Wirz

Strategies to improve efficacy and reduce side effects of immune checkpoint blockade (ICB) therapy are clinically relevant. Here, we described a transdermal cold atmospheric plasma (CAP)-mediated ICB therapy. Local delivery of CAP through hollow-structured microneedles as microchannels promote the release of tumor- associated antigens by CAP. The subsequent T cell-mediated immune response can be augmented by the immune checkpoint inhibitors delivered via microneedles, resulting in enhanced local and systemic anticancer immunity.

Stephen Samples Richard Wirz

At PSPL we are developing the Miniature Xenon Ion (MiXI) thruster to operate both as primary propulsion for CubeSat and SmallSat missions, and as secondary propulsion for larger missions. MiXI, first developed in 2001 by Wirz, is a 3 cm diameter, 30 - 100 W high efficiency miniature gridded ion thruster. We are incorporating new discharge designs, such as the Axial Ring Cusp Hybrid (ARCH) discharge, into MiXI, and characterizing both MiXI(3-Ring) and MiXI(ARCH) with miniature hollow cathodes.

Historical IIEE model applied to electrospray thruster propellant.
Jared Magnusson Nolan Uchizono Richard Wirz

Ion-induced electron emission (IIEE) has received relatively little research attention in electrospray thruster operating regimes. In addition, kinetic emission theory has largely revolved around monatomic ion projectiles, while polyatomic cluster data at low velocities are lacking. Moreover, potential emission may not be neglected due to such low velocities. Efforts to characterize secondary electron yield would reduce uncertainty of thruster plume measurements and inform the lifetime models for programs such as LISA Pathfinder.

Collection optic inside high bay chamber at JPL, pointing at collection area on MaSMi
Mary Konopliv Richard Wirz Lee Johnson

Optical Emission Spectroscopy is a non-intrusive optical method for analyzing plasma properties including electron temperature emitted by a plasma source, such as the plasma column in UCLA's Pi facility or a Hall thruster at JPL. This optical method measures plasma parameters with a collection optic inside of the vacuum chamber but does not interfere with the measured plume as a semi-invasive probe would. With OES, the spectrum of photons emitted by a plasma source due to interactions between electrons and xenon (or another gas) atoms and ions is measured.

Adam Collins Richard Wirz UCLA Electrospray Team

The Laser Interferometry Space Antenna (LISA) mission is a European-led gravitational wave observatory consisting of three independent spacecraft flying in a synchronized formation. Each spacecraft must operate "drag-free" against any disturbances or accelerations that would impact the signal-to-noise ratio of the gravitational wave signal. Busek Co. developed the Colloid Micro-Newton Thruster (CMNT) for the LISA Pathfinder ST7 mission to demonstrate colloid electrospray propulsion as a viable technology for disturbance reduction.

Nolan Uchizono Richard Wirz

Metamaterials are man-made devices engineered with sub-wavelength features, producing extraordinary behavior, such as negative refractive index or nonlinear dispersion. Integrating a plasma discharge enhances the function of these metamaterial structures, enabling modification and control over their response. Our research focuses on the excitation of electron density oscillations at the plasma/dielectric interface using metamaterials as coupling devices. This effort is part of a larger Multidisciplinary University Research Initiative (MURI) between Stanford, UCLA, UW, UT-Austin, and PSU.

Gary Li Chris Dodson Dan Goebel Richard Wirz

We investigate the time-dependent sputtering behavior of materials with micro-architectured surfaces for extending the lifetime of devices with similar plasma environments (electric propulsion/fusion). A hollow cathode generated argon or xenon plasma is directed to a biased target via solenoid magnets to provide energetic ion bombardment. Tested materials include refractory metals (molybdenum, rhenium), carbon-based compounds, and dielectric (Al2O3, Macor).

Anirudh Thuppul Gary Li Peter Wright Richard Wirz

In collaboration with AFRL, we investigate extraction mechanisms in ionic liquid electrospray thrusters for optimizing for the design of multi-emitter arrays. Initial studies will include electrostatic simulation of the emitter-extractor domain to determine particle paths for varying geometries. As this project is ongoing, future efforts may include collaborative experimental investigation of thruster prototypes, electrospray plume characterization, and electrohydrodynamic modeling and simulation.

Angelica Ottaviano Anirudh Thuppul Chris Dodson

The objective of this work is to provide in situ imaging of micron-scale surface structures using a long distance microscope (LDM) to study plasma-material interactions, in particular ion-induced erosion of plasma-facing materials. A CMOS camera and microscope system is used to capture live images of material erosion resulting from exposure to a magnetically confined plasma. Focus stacking images to create composite images and height maps at various time steps yields videos displaying the time-dependent erosion.

Samuel Jun Araki Ben Dankongkakul Richard Wirz

Magnetic cusp confinement of plasma at conducting surfaces involves interactions between a highly divergent magnetic field, ions, electrons, neutral particles, and the pre-sheath and sheath conditions that develop along the surface boundary. Large plasma devices have benefitted greatly by using permanent magnet cusps for bulk plasma confinement for both terrestrial and space applications; however, the magnetic cusp confinement mechanisms and the associated plasma dynamics very near the conducting surface are poorly understood.

Chris Dodson Taylor Matlock Dan Goebel Richard Wirz

Degradation of plasma-facing materials is a significant problem in electric propulsion, pulsed power technologies, and fusion energy experiments. To reduce material degradation, new micro-engineered materials are being developed that reduce sputtering and thermal stress through an increased surface volume and area exposed to the heat flux, along with the use of micron-sized dendrites, nodules, or fibers that can deform independently.

Lauren Chu Steve Synder (JPL) Dan Goebel Richard Wirz

High power solar electric propulsion capabilities have the potential for significantly decreasing the mass and cost of many future NASA exploration missions. Reducing the spacecraft’s mass and complexity of power processing by utilizing Direct Drive power technology will save mission cost, as suggested by studies of high power systems.

Marlene Patino Taylor Matlock Richard Wirz

The interaction of charge-exchange collisions ions created in the plume of ion and Hall-effect thrusters interacting with background electric fields contribute to unwanted spacecraft surface sputtering and grid erosion, thereby limiting the thruster and spacecraft operation and lifetime. Improving our understanding of heavy species collisions (e.g. momentum-exchange and charge exchange collisions between ions and neutrals) in intermediately-ionized plasma is necessary for furthering the development and use of electric propulsion devices for deep space missions.

Hollow cathode aim at single cusp with Helmholtz background B-field
Ben Dankongkakul Samuel Jun Araki Richard Wirz

The development of permanent magnet microdischarge on the scale of 1 cm requires an improved understanding of magnetic cusp confinement physics very near the anode. Larger magnetically confined discharges benefit from relatively low surface-to-volume ratios, which can provide favorable electron confinement and high ionization efficiency.

MaSMi-60 Hall thruster operating at 250 V and 350 W, JPL High Bay Facility
Ryan Conversano Dan Goebel Richard Hofer Ioannis Mikellides Ira Katz Richard Wirz

This research aims to demonstrate the applicability of magnetic shielding to low power Hall thrusters as a means to significantly improve operational lifetime. The key life-limiting factors of conventional Hall thrusters, including ion-bombardment sputter erosion of the discharge channel and high-energy electron power deposition to the channel walls, are well understood on all thruster scales.

Microdischarge magnetic field mapping using COMSOL
Cesar Huerta Stephen Samples Richard Wirz

A microplasma source for photonic crystal applications is currently being developed at UCLA. Wirz' hybrid model, DC-Ion, is being used to simulate and diagnose this microdischarge. For validation, a well-characterized ring-cusp discharge is first modeled with the code.

Chris Dodson Benjamin Jorns Richard Wirz

This project investigates the existence of high energy ions generated in high current hollow cathode plumes using Laser Induced Fluorescence (LIF) and plasma probes. Ion acoustic turbulence is generated from a high electron to ion relative drift velocity, and wave-particle interactions lead to heating of plasma in the plume. Energetic ions can cause erosion of cathode surfaces used for long duration missions using Hall thrusters. We test a 100 A-class hollow cathode at JPL and perform LIF measurements to study the formation of energetic ions and the evolution of the IVDF in the plume.