A portable air-fed cold atmospheric plasma device was invented for postsurgical cancer immunotherapy to inhibit tumor relapse.

Conventional plasma jets for biomedical applications tend to have several drawbacks, such as high voltages, high gas delivery, large plasma probe volume, and the formation of discharge within the organ. Therefore, it is challenging to employ these jets inside a living organism’s body. Thus, we developed a single-electrode tiny plasma jet and evaluated its use for clinical biomedical applications. We investigated the effect of voltage input and flow rate on the jet length and studied the physical parameters of the plasma jet, including discharge voltage, average gas and subject temperature, and optical emissions via spectroscopy (OES). The interactions between the tiny plasma jet and five subjects (de-ionized (DI) water, metal, cardboard, pork belly, and pork muscle) were studied at distances of 10 mm and 15 mm from the jet nozzle. The results showed that the tiny plasma jet caused no damage or burning of tissues, and the ROS/RNS (reactive oxygen/nitrogen species) intensity increased when the distance was lowered from 15 mm to 10 mm. These initial observations establish the tiny plasma jet device as a potentially useful tool in clinical biomedical applications.

Electric propulsion (EP) ground tests need to address multiple facility effects such as carbon sputtering, erosion, and deposition across the inner surfaces of both the thruster and vacuum chamber facilities. As part of a multi-university experimental investigation of the H9 Hall effect thruster as a part of the Joint Advanced Propulsion Institute (JANUS), this paper reports on surface morphology of polycrystalline graphite with different grain sizes and stainless-steel 304 panels tested based on the total fluence of incident ions. Erosion and deposition are evaluated using target and witness plates placed strategically throughout the vacuum facility. Scanning Electron Microscope (SEM) images provide useful qualitative insight into surface morphology while optical profilometry and laser confocal methods provide quantitative results. Quantitative estimates show high uncertainty due to the short test duration, total ion fluence, and surface anomalies; but inform improved approaches to future tests. Preliminary energy-dispersive X-ray spectroscopy (EDS) measurements reveal evidence of deposition on witness plates from non-carbon sources such as stainless-steel and aluminum. These results support companion sputter/deposition modeling efforts and suggest that additional graphite shielding of facility surfaces and use of advanced materials and beam target design may prove beneficial for sputter material mitigation.

Understanding neutral flux behavior within vacuum facilities is important for characterizing the facility effects and design. For applications such as electric propulsion (EP), thruster behavior, performance, and lifetime during ground tests are often obfuscated by facility-borne neutral particles in the thruster plume and those ingested into the thruster. To characterize dominant neutral flow phenomena within EP vacuum facilities, we use 3D flux-based angular coefficient methods to provide rapid and robust analyses. Analytical and computational modeling is used to characterize representative geometries as well as two large, state-of-the-art EP facilities. The results show that the “bulk drift” of neutral particles provides a three-dimensional motion of neutral species within vacuum facilities. Using this perspective, facility operators and designers can quantify particle fluxes and densities throughout the chamber to characterize the facility effects for ground-based thruster testing and other vacuum applications.

Electric propulsion (EP) ground tests need to account for multiple facility effects such as carbon sputtering, erosion, and deposition across the inner surfaces of both the thruster and vacuum chamber facilities. As part of a multi-university experimental investigation of the H9 Hall effect thruster as a part of JANUS (Joint Advanced Propulsion Institute), this paper reports on surface morphology of polycrystalline graphite with different grain sizes and stainless-steel 304 panels tested based on the total time integrated flux of incident ions produced by the thruster. Erosion and deposition observations are discussed with regard to their locations within the facility and expected ion flux from the plume. Scanning Electron Microscope (SEM) images provide useful qualitative surface morphology. Preliminary optical profilometry and laser confocal methods provide quantitative results but with high uncertainty due to the short test duration and surface anomalies; but inform improved approaches to future tests. Preliminary energy-dispersive X-ray spectroscopy (EDS) measurements reveal evidence of stainless-steel and aluminum sputtered material. These results support companion sputter/deposition modeling efforts and suggest that additional graphite shielding of facility surfaces and use of optimized volumetrically complex materials (VCMs) may prove beneficial.

High power electric propulsion space missions require vacuum facility ground tests to predict in-space life and performance. Gridded ion thruster (GIT) mission life prediction must account for facility effects such as facility induced neutral and sputterant flux, which affect thruster performance and grid erosion, which can obfuscate predictions of grid transparency and electron backstreaming. This work demonstrates a simple GIT Predictive Engineer Model (GIT PEM) that captures these coupled effects. The model uses experimental and computational data from NASA’s NSTAR thruster, though any GIT could be used. The GIT PEM is exercised for key aleatoric and epistemic uncertainties, including those related to life threshold, model estimations, relevant physics, thruster operating conditions, and mission scenarios to characterize model sensitivities and uncertainty quantification. Results show that different life mechanisms dominate depending on imposed assumptions, examined factors, and uncertainties. For example, the most common life mechanism for ion thrusters, electron backstreaming, can exhibit high uncertainty for simplified approximations and is strongly influenced by facility-related uncertainties such as charge exchange collisions and sputter deposition.