Conveners
Posters Fundamental Research and Basic Processes and Power Electronics
- Emily Schrock (Sandia National Laboratories)
- John W. Luginsland (Confluent Sciences)
Predicting gas breakdown for micro- and nanoscale dimensions increases in importance as devices continue to shrink. A recent study derived a single universal theory to predict breakdown voltage for any gas and pressure for breakdown characterized by Townsend avalanche or field emission at microscale [1]. At microscale, the gas breakdown model more strongly depends on the electrode conditions,...
High power impulse magnetron sputtering (HiPIMS) is an important example for the technical application of magnetized low temperature plasmas. The spontaneous emergence of self-organized structures (spokes) and the presence of anomalous transport - probably two sides of the same coin - play an important role in HiPIMS and related E$\times$B discharges (e.g., Hall thrusters) [1]. These phenomena...
Although gas breakdown for radiofrequency (RF) and microwaves has been extensively studied, a consistent and accurate model for AC breakdown voltage independent of unknown fitting parameters remains incomplete. While the RF breakdown model derived by Kihara theoretically justifies a fitting parameter based on various molecular constants, the magnitude used to match experimental results differs...
Continued miniaturization of electronic devices requires a comprehensive understanding of electron emission behavior at micro- and nanoscales for applications involving micro- and nanoelectromechanical systems (MEMS and NEMS, respectively) and microplasmas. While Paschen’s law (PL) traditionally governs gas breakdown, field emission (FE) causes experimental deviation from PL at microscale [1]....
A Helicon wave heated hydrogen plasma is created by applying 800 W RF power to a Nagoya-III antenna at 13.56 MHz frequency, which excites m = ±1 azimuthal mode in the plasma. A permanent ring magnet provides the axial field required for the helicon wave excitation. The plasma expands from the source chamber to the expansion chamber in a diverging magnetic field. Diagnosis of the wave field...
State of the art low pressure cold cathode pseudospark switches (PSS) for high pulsed power applications require special kinds of trigger electron source, which possess long life, reliable, durable, uniform electron emission, economical, etc. [1-4]. A high dielectric (dielectric constant ~2000) ferroelectric based trigger source is one of the best suited trigger mechanism for the PSS [2-4]. In...
Discharge formation and breakdown in water have critical implications for water sterilization and biomedical applications [1]. Several studies demonstrate current scaling in liquids following field emission by the Fowler-Nordheim law (FN) and space charge-limited emission (SCLE) by the Mott-Gurney law (MG) with collisions [2]. Recent theoretical work for gases has unified the asymptotic...
A recent theoretical study unified field emission modeled by Fowler-Nordheim (FN) and space charge limited emissions (SCLE) with and without collisions modeled by Mott-Gurney (MG) and Child-Langmuir (CL), respectively [1]. This study showed the existence of a triple point, where the three asymptotic solutions matched, and the ubiquitous nature of CL at high voltages, even at high pressure [1]....
Pulsed power experiments rely on magnetically insulated transmission lines to deliver mega-amps of current to a load to produce and study high energy density matter. Experimental results show that the formation of low-density plasmas in the power feeds gives rise to parasitic currents, which affect load dynamics and prevent scaling of load parameters. To understand the inimical transport...
The dynamics of streamers in PIC-DSMC simulations of 3D pin-to-plane wedge geometries are formally quantified for several azimuthally swept wedges in terms of electron velocity and density as temporal functions of spatial direction and coordinates r,$\phi$,z. Particles are tracked with picosecond temporal resolution out to 1.4 nanoseconds, spatially binned, and averaged over six independent...
In 1963, L.M. Chanin and G.D. Rork[1] measured the first Townsend ionization coefficient for various gasses and a range of pressures experimentally in a vacuum tube. A Townsend discharge is an ionization avalanche that occurs between two electrodes when secondary electron emission caused by ion impact on the cathode is negligible. The first Townsend coefficient, α, is essentially a measure of...
Nanosecond pulsed plasmas (NPPs) can efficiently generate ionized and excited species. While numerous studies have examined local flow field effects [1], characterization of the induced flow field and electrode geometry and the induced flow field remains incomplete. We hypothesize that altering the electrode configuration to modify the electric field will strongly influence plasma species...
The US Air Force is investigating the dynamics of plasmas sustained for long times using focused microwaves laboratory in conditions which approximate free-space. When the plasma density is sufficiently below the cut-off density the plasma develops regular desnity variations with a wavelength equal to one half the wavelength of the drive beam. We hypothesize that these density variations are...
Nano- and microscale surface features can have drastic impact on field enhancement and work function, altering field emission from the material. This can significantly change gas breakdown voltage for microscale gaps at atmospheric pressure [1], where field emission drives breakdown rather than Paschen’s law. This presentation reports the nanofabrication of surface feature protrusions [2] and...
Graphene has gained a lot of attention due to its exception properties of high electron mobility (104-5 cm2/Vs), electric current carrying capacity (~108 A/cm2), optically transparent (> 95 %) and considered as an excellent candidate for next-generation optical, electrical and spintronic devices. Graphene properties can be modified by altering the graphene/substrate interfaces by changing the...
The field of study of the explosion of metallic conductors has great scientific interest for researchers [1] because of its adjustable input power, low-temperature plasma generation, and production of nanoparticles for materials science applications. X- and Z-pinch configurations of wires are studied across a broad range of pulsed power drivers. The diagnostics for such experiments typically...
Dielectric Elastomers have the potential of exhibiting large strains when the material is in the presence of an electric field. The dielectric in this case is a soft acrylic (VHB 4910) film that is sandwiched between two compliant electrodes that are subjected to a high voltage potential. When high voltage is applied, attracting charges lead to a contractive force known as electrostatic...
Nano/micromotors that can convert local chemical fuels or external physical inputs into autonomous motion and perform a variety of advanced functions ranging from active drug delivery to environmental remediation and nanofabrication [1]. Synthetic micro/nanomotors can be self-propelled or externally powered in the liquid phase by different types of energy source such as catalytic,...
VPIC is being ported and optimized on several modern architectures. These include KNL processors available on Trinity, Cori and Stampede2, Skylake processors available on Mare Nostrum and Stampede2, IBM Power 9 processors and Volta GPUs available on Summit and Sierra and ARM ThunderX2 processors, available on Astra at Sandia and ARM clusters at Los Alamos National Laboratory. VPIC is in...
Speed-limited particle-in-cell (SLPIC) modeling is a new simulation technique [Werner et al., PoP 25, 123512 (2018)], potentially much faster than conventional PIC, for modeling plasmas characterized by low-velocity kinetic processes. Numerical constraints (e.g. timestep limitations associated with particle cell-crossing times or stability limits) often place challenging restrictions on...
High-power microwave source design has evolved from analytic scaling laws to advanced computational methods that can virtually prototype devices before metal is cut in the laboratory. However, with this success has come the requirement that the DOD have the capability to quickly design novel HPM sources for applications with different power and frequency requirements. This need for rapid...
In current and future pulsed-power devices, it has become increasingly important to have predictive capability for determining the amount of energy coupled through the magnetically-insulated transmission line (MITL) to the load. Because of the high magnetization and low densities of electrode plasmas in the MITL gap, extended-MHD effects may play a critical role in power-flow physics. In...
DIODE DESIGN FOR INCREASED RADIATION DOSE IN HERMES III FAR-FIELD
Troy C. Powell, Andrew Biller, Keith L. Cartwright, Timothy J. Renk, and Timothy D. Pointon
Sandia National Labs, 1515 Eubank SE
Albuquerque, NM 87123 USA
Increasing radiated dose in the HERMES III far-field region is both a matter of mitigating current loss in the MITL and electron incident angle on the Bremsstrahlung...
The paper is devoted to the calculation of equilibrium compositions, thermodynamic properties (mass density, enthalpy and specific heat at constant pressure) and transport coefficients (electrical conductivity, viscosity and thermal conductivity) of C4F7N/CO2 thermal plasma. Assuming local thermodynamic equilibrium, the species composition is determined using the principle of minimization of...
We present a new code for solving the Wigner-Poisson system. Drawing from techniques for solving Vlasov-Poisson, we employ Strang splitting to divide Wigner-Poisson into an advection equation and an integral equation describing velocity space. A forward, Semi-Lagrangian scheme based on the Convected Scheme handles the advection piece while a Fourier transform handles the velocity integral...
Capacitively coupled plasmas (CCPs) are widely utilized in etching and deposition processes in semiconductor manufacturing. Nowadays, the nonuniformity of plasma density and temperature distributions is a critical issue near the wafer edge which results in non-uniform etching or deposition profiles. Computer simulation is a good tool to understand the background physics of the nonuniformity...
We seek a nonequillibrium, heterogenous, large-scale model for strongly coupled plasmas. We generate a generalized hydrodynamic model for strongly coupled plasmas using density functional theory closures of BBGKY hierarchies via hypernetted chain theory. We formulate these equations in the form of a balance law, thereby providing a ''memory'' effect, facilitating correlation. This isothermal...
Many interesting and important problems in plasma science involve the differential motion of regions of plasma, threaded by the same magnetic field lines. In all reference frames, there is a difference in the motional electric field between regions, a difference in potential parallel to the magnetic field, and currents that couple the different regions, thus transferring momentum by J x B...
This experimental investigation of colliding plasma flows which are frozen-in opposing magnetic fields was conducted to better understand and describe microscopic instabilities and macroscopic-flow patterns. The Plasma Physics and Sensors Laboratory (PPSL), located at Wright-Patterson AFB, developed an experimental setup where a pulsed power system is used to create colliding flows through an...
The Colorado Solar Wind Experiment (CSWE) simulates solar wind plasma with ion energy up to 1 keV. We present two sets of experimental results related to the interaction of the solar wind with airless bodies: 1) solar wind interactions with lunar magnetic anomalies (LMAs); and 2) wake formation with various Debye lengths relative to the object size. In the first experiment, a permanent magnet...
The main difficulties in verification of numerous mathematical models of an electrical discharge in water is a lack of experimental studies observing a spark channel expansion and its comparison with an experimental result. As a rule, the authors compare an acoustical signature produced by an underwater discharge and also how a bubble cavitation matches the simulation. The presented...
Using particle-in-cell Monte Carlo collision simulations we have demonstrated an electron heating mode transition from drift-ambipolar (DA) mode to $\alpha$-mode in the capacitively coupled oxygen discharge as the operating pressure [1,2], electrode separation, and driving frequency [3] are increased. Here we explore further the transition as pressure and electrode separation are varied. When...
Carbon dioxide CO$_2$, as thermodynamically stable end product of fossil fuel based combustion, is an interesting source for carbon monoxide CO, if a sustainable energy source is used. CO is a major precursor in chemical synthesis, e.g. Fischer-Tropsch based CO hydrogenation to synthetic hydrocarbons and future fuels.
In this study, pulsed power technology has been applied for generating a...
A simulation code is under development for the solution of the time-dependent Boltzmann equation, self-consistently coupled with time-evolving nitrogen plasma chemistry of an electron beam driven discharge. The application is to a N2 filled chamber of pressure 0.1 to 10 Torr driven by the NRL 90 kV Febetron generator with a e-beam current pulse of 100 ns, peak current of 4 kA, and beam current...
Carbon monoxide is a gas generated by incomplete combustion and carbon compounds, and generally recognized as a toxic gas. Also, it is known as greenhouse gas. The emission amount of carbon dioxide is increasing year by year, which is recognized as a severe environmental problem. On the other hand, it is considered to be an industrially useful material used for the synthesis of methanol....
Low temperature atmospheric pressure non-equilibrium plasma was generated in liquid hydrocarbon with gas bubbles to characterize the reformed gases formed by hydrocarbon processing. A 10g sample of hexadecane was used as liquid hydrocarbon while 90% CH4, 10% H2 gas bubbles of 50 sccm was flown throw it. A RC circuit was used to generate nano-second pulsed plasma with 20pF capacitor and 1.5M...
Control of low-temperature plasmas for materials processing is critical to the quality of the product. Therefore, it is required to further refine and customize reactive fluxes. In this regard, a global model was used to study the electron kinetic effects in Cl$_2$ and CF$_4$ plasmas. The model was benchmarked against another global model by using the same set of gas phase and wall surface...
Plasma chemistry induced in air by an electron beam is being studied at the Naval Research Laboratory. An electron beam is produced in vacuum using a Febetron pulsed-power generator modified to produce a peak voltage of 80 kV, a peak current of 4 kA, and a pulse width of 100 ns. The beam then passes through a thin anode followed by a thin pressure barrier into a cavity filled with low-pressure...
Understanding air plasma chemistry requires accounting for the myriad of gas phase reactions initiated and mediated by electrons and excited species in the presence of an applied field. In the case of a time-varying electric field, this task of tracking reactions is even more complex. Models developed to track these physical processes require physics verification, model benchmarking and...
The chemical process that occurs in plasma-liquid interaction is a key issue in plasma biomedical applications and clinical treatment processes. The researchers have discussed the effects of different plasma sources and liquid components on the generation of aqueous RONS [1-3] while almost no one cares about the different liquid-dissolved gases have what different influence on the...
China Spallation Neutron Source (CSNS) is the first neutron source facility in developing countries. it includes a powerful linear proton accelerator, a rapid circling synchrotron, a target station and three neutron instruments. As one of the largest science and technology infrastructure projects in China, CSNS is expected to have positive effects in promoting the sciences, high-tech...
Abstract - The purpose of this paper is to show the work being performed to develop a compact rapid capacitor charger suitable to charge Marx banks to voltages ranging between 5 kV to 10 kV. The capacitor charger is being constructed with mobility in mind; for this reason it is powered using a series of high current LiPo batteries. A detailed description of the different system components is...
A passively balanced, bipolar high voltage power supply was created to drive a compact pulsed power system. The supply was designed to average 100 kW when charging a capacitive load to ±50 kV with a total volume of less than 15 L. The supply is sourced from a low-ESR ultra-capacitor bank charged to 285 V and operates with runtime durations less than a few seconds. The converter employs a...
In the field of high voltage discharge device and pulse gas laser, electrode profiles, in the determination of the polar electric field, have a direct impact on the quality of the product. From the demand of practical engineering, for the high-current two-electrode self-breakdown repetitive spark switch, in this paper, we selected the ball electrode, flat bulb electrode, Chang and Bruce, four...
In compact pulsed power applications, high voltage is often sourced by a DC to DC resonant converter that draws power from a manageable, lower voltage source. As the converter’s switching frequency is increased, the size of the magnetics decreases increasing overall power density. Despite its many advantages, increasing the frequency can increase the switching losses within the rectifying...
In the work presented here, a well-controlled study has been performed to characterize the performance of a high-voltage, pulsed-power capacitor when it is recharged to 100 kV in 100 μs. A CLC testbed has been assembled to supply the high rate pulsed recharge current to the capacitor being studied. Experiments are being performed in a controlled temperature environment ranging from 20 deg C to...
Amorphous metal magnetic cores are essential in developing multi-pulse solid state systems due to their high magnetic saturation value. In order to operate in multi-pulse mode, the magnetic core must provide enough volt-seconds before reaching saturation. They must prove to be reliable and maintain little to no load loss during the high rate pulses. This paper presents the efforts to...
To enable the use of additively manufactured polymer materials as structural and insulating components within high voltage pulsed power systems, better understanding of material compatibility with common pulser material environments is required. The present work examines the effect of long-duration contact of printed polymeric components with three high voltage insulating oils: Diala, Luminol,...
The SPIDER experiment features four radiofrequency (RF) circuits to heat the plasma generated in its inductively coupled ion source. Each circuit includes a tetrode-based Colpitts push-pull oscillator (200kW rated power) operating at 1 MHz frequency, a coaxial transmission line to feed the load composed of a couple of RF antennas and a resonant matching network. The SPIDER operation has shown...
Millimeter wave summation is the only way to achieve high power generation due to the limited power handling capability of a single high power microwave source. In this work, a 12-way power combiner was experimentally studied. The amplitude and phase of each input are adjustable using 12 attenuators and 12 phase shifters. The output of the power combiner was received by an open-ended waveguide...
Eagle Harbor Technologies (EHT), Inc. is developing a Ćuk converter for local helicity injection and magnet driving and control for the Pegasus Toroidal Experiment at the University of Wisconsin – Madison. A Ćuk converter has low output ripple; high efficiency; voltage gain greater than one, allowing for deeper energy storage utilization; continuous power flow that lowers output EMI, reducing...
Low temperature plasma microdischarges in contact with aqueous solutions which include organic dyes are studied. Plasma treatment of samples over a duration of time encompassing one hour are observed. The Ultraviolet–visible (UV-Vis) spectrum of select samples is analyzed to assess and measure the change in organic dye content. Results are presented which indicate the efficacy of small scale...
Plume morphologies and their formation mechanism of an atmospheric pressure argon plasma jet excited by a biased voltage
Xuechen Li , Xiaotong Lin, Kaiyue Wu, Rui Liu, and Pengying Jia
College of Physics Science & Technology, Hebei University, Baoding，071002
Several morphologies of plasma plume are observed through using an argon plasma jet, including solid cone, hollow cone, regularly swells,...
