Posters: HPM, Repetitive Pulsed Power, Plasmas, Dielectrics, & Analytical Methods
Poster 1: 1
Multipactor Suppression in X-band Waveguide Utilizing Surface Coatings
TTU, United States of America
Multipactor (MP) is a phenomenon where electron multiplication via secondary electron emission (SEE) can occur in waveguides under vacuum conditions. The effects of multipactor can lead to component damage or destruction. This study will explore techniques to suppress MP via modification of the secondary electron yield (SEY) using surface coatings and surface treatments.
This study applies a previously developed X-band high power microwave system and TE10 impedance transformer to test and compare MP formation in a pure copper sample versus samples with surface coatings and treatments. Surface coatings such as Titanium Nitride and Titanium Chromide are of particular interest to this research as they can shift the first crossover point to higher primary electron energies, thus potentially improving the longevity of space-based communication systems and accelerators. The maximum threshold power achievable by such systems may consequently be further increased. Experimental findings are reported and compared against simulations and available literature.
This research was supported by the Air Force Office of Scientific Research under contracts FA9550-18-1-0062 and FA9550-21-1-0367
Poster 1: 2
Development of GaN HEMT based positive and negative, 5 kV, nanosecond pulse generator for the SLS 2.0 fast injection kicker
Paul Scherrer Institute, Switzerland
The SLS 2.0 project aims upgrading the existing 3rd generation Swiss Light Source (SLS) at the Paul Scherrer Institute in to a 4th generation, diffraction limited light source down to soft X-ray wavelengths, to substantially increase its brightness and to ameliorate the photon beam stability in top-up mode.
Conventional (four-kicker) top-up injection in a Storage Ring (SR) perturbs the stored electron beam, causing disturbance or interruption in the photon beam provided to the experimental stations. This creates inconveniences to sensitive experiments and reduces the total available photon flux. To minimize this effect, parallel to the baseline four-kicker injection system, SLS 2.0 plans to adopt a novel electron injection scheme (aperture sharing) that should limit the perturbed portion of the stored beam to only a couple of percents, leaving the rest of the beam to radiate undisturbed.
A fast injection kicker, with deflection duration of several tens of nanoseconds, kicks the injected and a small portion of the stored beam in such way that they both are accommodated in the SR dynamic aperture. After some damping time, the injected and the displaced stored electron bunches join together returning to the nominal beam orbit, replenishing the stored beam charge. To power such fast kicker, short (<40 ns), positive and negative electrical pulses with up to 5 kV amplitude are necessary. We describe the progress in the development of a GaN HEMT based Marx pulse generator, capable of satisfying these requirements.
Poster 1: 3
Improvements of a Branch Module for an Inductive Voltage Adder based on Measurements and Circuit Simulations
1CERN, Switzerland; 2Karlsruhe Institute of Technology, Germany
For future upgrades of some CERN kicker systems, doubling of the driving current by replacing a matched impedance by a short circuit termination is of interest, because it allows a doubling of the kick strength, without an increase in magnet length or generator voltage.
For this application, a branch module for an inductive voltage adder has been designed and built.
Poster 1: 4
A Compact GNLTL Using Permanent Magnet Rings With Improved H-field Uniformity
1INPE; 2UNIFESP; 3UNM
There has been a great interest in using gyromagnetic nonlinear transmission lines (GNLTLs) for compact applications in defense platforms, radars, and space as pulsed RF transmitting sources. The reason is that the GNLTL is all solid-state and does not require vacuum and heating as power electronic tubes. As these devices employ axial magnetic bias, permanent magnets can replace the solenoid to reduce weight and dimension. The ideal case for this is to use neodymium rings along the line. However, the magnet ring configuration produces lower H-field uniformity to the solenoid , producing very low pulse modulation in the RF signal generated with a longer line (50 cm or more). Therefore, the solution appears to be using a small line length of 10 cm as we verified the H-field is improved using a low number of magnets that could lead to a better pulse modulation . Then, in this work, we will present the results obtained with a bench compact shorter line (10 cm) using neodymium ring magnets operating with a Gaussian shape input pulse in the range of 6-12 kV and with a width of about 15 ns.
 J. Bragg, J. Dickens, and A. Neuber, "Magnetic biasing of ferrite filled nonlinear transmission lines," 2010 IEEE International Power Modulator and High Voltage Conference, 2010, pp. 600-603, DOI: 10.1109/IPMHVC.2010.5958430.
 J. O. Rossi et al., "RF Generation Using a Compact Gyromagnetic NLTL with Permanent Magnets *," 2021 IEEE International Conference on Plasma Science (ICOPS), 2021, pp. 1-1, DOI: 10.1109/ICOPS36761.2021.9588544.
-Work supported by SOARD/AFOSR, FAPESP, and CNPq under contracts no. FA9550-18-1-0111, 2018/26086-2 and 306540/2019-3, respectively.
Poster 1: 5
Initial Development of an Inductive Adder for High-Energy Beam Kickers
Eagle Harbor Technologies, Inc., United States of America
The Electron Ion Collider being constructed at Brookhaven National Laboratory (BNL) requires a 150 MeV energy recovery LINAC, whose design includes a new short-pulse stripline kicker. The kicker power system must deliver ±50 kV pulses with pulse widths of less than 38 ns into a 50 Ω load and with low jitter. The kicker power system must be highly reliable and robust to potential faults. Eagle Harbor Technologies (EHT), Inc. is developing a new inductive adder that can meet the needs of the BNL kickers. In this program, EHT designed a single inductive adder stage that was used to demonstrate the pulse characteristics including fast rise and fall times, low jitter, and flat-top stability while operating at the full current (1 kA). EHT will present the development status and output waveforms.
Poster 1: 6
A Bipolar Microsecond Pulser for Electroporation and Cancer Therapies
Eagle Harbor Technologies, Inc., United States of America
Emerging biomedical therapies that use electroporation and other electrode-driving techniques require new medical pulsed-power systems. In electroporation, electric fields are applied to cells to increase the permeability of the cell membrane. Chimeric antigen receptors (CAR) T-cell-based therapeutics is a growing electroporation application that requires complex pulse and burst patterns with high-voltage, bipolar pulses.
To address the growing biomedical market demand, Eagle Harbor Technologies, Inc. (EHT) developed a programmable, bipolar microsecond pulse generator. This pulse generator produces ±3 kV pulses with pulses widths from 500 ns to DC at high pulse repetition frequencies up to 100 kHz and precision burst control. An internal microcontroller combined with a graphical user interface allows the user to remotely control the pulse widths, dwell times, and burst patterns. We will present the pulser capabilities including output waveforms.
Poster 1: 7
X-band Relativistic Backward Wave Oscillator with Dynamic Frequency Tunability
CEA France, France
Relativistic tubes are generally used for High Power ElectroMagnetic (HPEM) applications. Most of these tubes radiate high level electromagnetic fields but operate at a fixed frequency. Nevertheless, in most cases, a variable frequency is required. In a previous study, CEA worked on a very compact HPEM source named CLAIRE. The used tube was an optimized X-band sub-gigawatt relativistic resonant Backward Wave Oscillator (BWO) using low-level magnetic field. Based on it, a frequency tunable BWO have been designed last year. Desired tunable frequency range is obtained by changing the distance between the resonant reflector and the Slow Wave Structure (SWS). The first experiments were operated with a fixed frequency. The goal is to obtain a dynamic tunability, which means that the frequency is tuned during a burst. Besides, a gap exists between resonant reflector and tube to facilitate the fast shifting of the reflector. As the electrical contact is not perfect, the impact of a gap on microwave signal was studied in simulation and experimentation. A specific prototype has been realized with an high mechanical accuracy. Two linear stepper motors allow the the resonant reflector motion into the tube. Two bellows maintain good vacuum state while the resonant reflector is mechanically actuated. In the new experiments, the dynamic tunability is validated during a 6s burst. This paper presents the analyzed results, and the comparison with fixed frequency results.
Poster 1: 8
A High-Power Microwave System for Benchmarking the Microwave Dielectric Strength of Carbon Fluoronitriles
P3E Center, ECE Dept., Texas Tech University, United States of America
Concerns about sulfur hexafluoride's (SF6) high global warming potential (GWP) have motivated the search for alternative insulating gases. Among the many possible alternatives, carbon fluoronitriles have been demonstrated as a promising alternative to SF6. Gases such as C4F7N (3MTM NovecTM 4710) feature a dielectric strength comparable to that of SF6 while simultaneously offering up to 99% reduction in total GWP. However, prior studies have been largely limited to long-timescale DC and 60 Hz AC conditions. This study details the development of a pulsed, highpower microwave system to experimentally characterize the microwave breakdown strength of C4F7N under microsecond pulsed conditions. This system utilizes a 3 MW S-band (2.85 GHz) high power magnetron and a resonant ring structure to deliver an effective microwave power of 20 MW to a stepped impedance transformer, yielding local electric fields exceeding 150 kV/cm (RMS). Microwave system design, calibration, and absolute field measurement data are reported. Design considerations for the gas mixing, gas isolation, and materials compatibility are reviewed, and initial measurements of dielectric strength are reported.
Poster 1: 9
Investigating the Dynamic Behavior of Copper Foils Driven by a Megaampere Class Capacitor Bank
Lawrence Livermore National Laboratory, United States of America
We report on the results of an investigation into the dynamic behavior of copper foils when driven at megaampere current amplitudes from a capacitor bank. For these studies, the cross-sectional area and length of the foils was kept constant, while the thicknesses were varied - from a few tens of microns to greater than one hundred microns. The initial mass of the foils was approximately 3 grams. The typical rise-time to peak current in the circuit was in the range of 10-20 microseconds. A diagnostic suite – which included B-dots, D-dots and Faraday rotation sensors – was used to record foil voltage and current time-histories, which in turn were used to calculate the dynamic impedance of the foil circuit. Optical diagnostics, including high speed imaging, were also used to record the dynamic behavior of foils as they were driven through different phase states by the high current discharge. Experiments were conducted in both axisymmetric (cylindrical) and non-axisymmetric (planar) geometries. The media surrounding the foils was also varied to characterize its influence on the dynamic impedance.
Poster 1: 10
Increasing the Hydrophobicity of Silicone Rubber for Electrical Insulators by Rapid Treatment with Pulsed Gliding Arc Plasma in Air
1State Key laboratory of Power Grid Environmental Protection (China Electric Power Research Institute), Wuhan 430074, China; 2Beijing International S&T Cooperation Base for Plasma Science and Energy Conversion, Institute of Electrical Engineering, Chinese Academy of Sciences, Beijing 100190, China; 3Key Laboratory of Solar Energy Efficient Utilization and Energy Storage Operation Control in Hubei Province, Hubei University of Technology, Wuhan 430068, China; 4University of Chinese Academy of Sciences, Beijing 100049, China
Hydrophobicity of silicone rubber (SR) is important for the anti-ice and anti-pollution property and flash-over performance of electrical insulators in transmission lines. In this work, gliding arc (GA), as one kind of non-equilibrium plasma, is generated by pulsed high voltage supply with ambient airflow and it is adapted for increasing the hydrophobicity of SR. Kaolin and NaCl solution are used for contaminating suspension and different salt deposit density (SDD, from 0.125 to 1 mg/cm2) is applied. It is found that with SDD of 0.125 mg/cm2 and only 30-second treatment with GA, the water contact angle (WCA) of SR increases from ~ 120° to 150°. Even so, with SDD of 1 mg/cm2, GA treatment of 300 seconds is needed to increase WCA from ~ 10° to 114°. In order to analyze the functional species in GA, optical emission spectroscopy is measured, which illustrates that the O atom has the highest intensity and the energy transfer from excited N2 to O2 contributes to a high O2 dissociation degree. Assisted with Fourier transform infrared analysis of original and treated SR surface, it is demonstrated that high-density O atoms generated by pulsed GA selectively etch the organic matrix of SR and accelerate the accumulation of hydrophobic components in the contaminant. This work proposes a rapid treatment method for increasing SR hydrophobicity, which only consumes electric power and ambient air (without any precursor or rare gas) and has a bright potential for application in the engineering field. [This work is supported by Open Fund of State Key Laboratory of Power Grid Environmental Protection (China Electric Power Research Institute), No. GYW51202101370]
Poster 1: 11
Investigation of sawing Response of PBX 9501 and PBX 9502
1Texas Tech University, United States of America; 2Consolidated Nuclear Security, Pantex Plant
The machining of explosive driven high current devices presents unique challenges in the safety of the operators, integrity of the part, and the timely completion of the operation. Previous works have shown that simple reduction in working speed can be detrimental to the safety of the operation and proper investigation into the machining parameters is needed to avoid dangerous conditions. This work investigates the operating conditions of a band saw in the cutting of polymer-bonded explosives (PBX). Samples of PBX 9501 and PBX 9502 are subject to a range of sawing speeds and feed speeds. Utilizing IR imaging and a force plate the heating of the blade is measured along with the overall forces on the work piece. Further, application of thermocouples in the work piece present more direct access to the conditions of the temperatures in the material of concern. Finite element simulation has been applied to give insight into the internal heat transfer occurring during sawing.
Poster 1: 12
Experiments on a Scaled Rebar Structure to Quantify Lightning Strike Induced Fields on Rebar Reinforced Concrete Structures
1P3E Center, ECE Dept., Texas Tech University, Lubbock TX; 2Mission Engineering Development Group, CNS Pantex, Amarillo, TX; 3Facility Engineering Electromagnetics Group, CNS Pantex, Amarillo, TX
Understanding electric and magnetic fields induced by lighting strike events is crucial to developing efficacious techniques for mitigating the negative effects of lightning strikes. However, experiments investigating the matter are sparse in literature as the prohibitive cost and complexity associated with a full-scale experiment make it impractical to perform. Utilizing electromagnetic scaling relations, scaled experiments allow for the collection of data that may be directly translated to equivalent full-scale quantities. As a second benefit, scaled experiments may also be used to validate computational models that can then be employed for full-scale simulations. Using this scaling principle, a single-layer rebar structure with a 1:4 scale has been constructed consistent with standard construction practices for steel-reinforced concrete structures. Unlike typical rebar structures, this scaled structure features a U-type electrical discontinuity in the roof, which is representative of the full-scale structure of interest to this study. A four-stage Marx generator is used to excite this structure with a peak current of 50 kA. Using a low inductance path, the output of the generator is fed to an attachment point on the structure while maintaining the required scaled rise time of 1.5 µs. Using a Prodyn B-10/20D B-Dot and AD-100R D-Dot probe, the fields produced during the attachment event are investigated. The ground point of the structure is controlled through a single low inductance strap attached to a point on the cage and fed to the building ground. The current passing through the grounding strap is monitored by a Pearson coil (Model #1330), allowing for strike current and waveform shape to be collected. Experimental measurements are compared with the computational model results to verify the computational model.
Poster 1: 13
The characteristic effects of dielectric coatings on electrical exploding film phenomena
University at Buffalo, United States of America
The exploding film phenomenon have a wide a variety of applications in the areas of fast switching, ceramic joining, nano-powder production and exploding bridge wire detonators. Exploding films have many of the same characteristics of exploding wires and foils when they are subjected to high energy densities on the order of magnitude of 107-108.The metallization layer is heated rapidly up to vaporization where the film explodes and the metal layer is ejected from the substrate. The dielectric coating in the exploding wire phenomena has been previously researched and shown to exhibit a significant increase in energy deposition in the wires core before plasma formation. This work investigates if there is any correlation on how the dielectric coating will affect the exploding film event. Current wave forms of initial strike, dwell time, maximum current of restrike and event duration were analyzed.
Poster 1: 14
Energy dissipation and efficiency of exploding film phenomena at varying stack length and thickness
University at Buffalo, United States of America
Metalized polypropylene films (MPPF) can substitute as an alternate for exploding wires in several applications. MPPF can implemented in several different orientation and shaped for more defined functions and applications. Different metallization and substrate thickness have previously been studied at the Energy System Integration laboratory. This work investigates how the plasma formation and electrical characteristic of the phenomena is affected when the MPPF a stacked in multiple parallel configurations.
Poster 1: 15
Benchmarking the suitability of Novec TM 4710 for application in flux compression generators
texas tech, United States of America
Current data indicates that C4F7N (3M, NovecTM 4710) may have many benefits over traditional insulating gases, such as SF6. For example, data has shown that pure NovecTM surpasses SF6 electrical insulating properties. However, the data available is primarily for DC or low frequency (i.e. 60 Hz) conditions and at static pressures. For applications such as flux compression generators (FCGs), the operating conditions are significantly different, and we have yet to see any data which is suggestive of NovecTM performance under dynamic stresses similar to those found in FCGs. Here we report a performance comparison of FCGs utilizing air, SF6, or NovecTM 4710 as the insulating gas. Generators used for this study consist of a single stage, single-pitch helix having an inner diameter of 46 mm (1.8 in), and employing an armature with a diameter of 25 mm (1 in). Direct current seeding is applied to the FCG. In the initial testing, the stator wires are kept bare of insulation to simplify the performance assessment to focus on the different gases. In the experiments, seed current, and load inductance, are explicitly chosen to emphasize the performance differences between NovecTM, air, and SF6 while avoiding statistical variations in other potential flux loss sources that could mask the gas-specific results. The generator dI/dt is monitored using Rogowski coils and provides the primary indications of gas insulation failure, that being sudden deviations or partial collapses in the waveform during FCG operation. The voltage and electric field distributions within the generator during times of observed indications of breakdown are estimated from modeling and simulation. Other comparisons of FCG performance - namely current gain, energy gain, and output voltage - are provided as well. Future research will address the performance of NovecTM 4710 in more practical FCGs that typically have a stator fitted with solid dielectric insulation. Mixtures may be investigated in the future to evaluate what it would take to match SF6 performance. In this context, we note that for low-frequency conditions, a mixture of 20% NovecTM 4710 with CO2 already matches the insulating performance of SF6.
Poster 1: 16
Impact Low Pressures on Internal Partial Discharge under DC Voltage
1Virginia Tech, United States of America; 2University of New Mexico, United States of America
All-electric transportation is targeted as one of the potential pathways to
Poster 1: 17
Study of Partial Discharge Inception Characteristics of Aviation Wire Stressed by PWM Voltages under Various Air Pressures
1The Ohio State University, United States of America; 2Air Force Research Laboratory/RQQE; 3Innovative Scientific Services, Inc.
Partial discharge (PD) is a common and detrimental phenomenon that can cause damage and potential breakdown in insulation systems. According to the Paschen’s curve, from sea level to high altitude, the partial discharge inception voltage (PDIV) of the air will decrease with decreasing pressure. So far, there has not been a widely accepted PD testing method for aviation wires in low pressure environment with pulse width modulated (PWM) voltage excitations. There have been studies of the PD behaviors of aviation wires with conventional triangular impulses, ac voltages, and PWM pulses with relatively low dv/dt before. But existing test methods and study results cannot be directly utilized to test and predict PDIV of aviation wires when high dv/dt PWM excitation is applied with wide bandgap (WBG) power devices, such as Silicon Carbide (SiC) Metal Oxide Semiconductor Field Effect Transistors (MOSFET).
Thus, this paper aims to provide more insights on PD behaviors of aviation wires under high dv/dt PWM excitations and possible ways to improve the existing PD test methods. A test setup including an ultra-high dv/dt PWM generator, a test sample fixture, and associated PD sensors including a photomultiplier tube (PMT) and a high frequency current transducer (HFCT), will be introduced. Experimental results and associated analysis for aviation wire test samples at various pressures under high dv/dt PWM excitations will be presented. The effect of the rise time of the PWM will be discussed in detail. Suggestions on how to improve test methods and test standards will be provided.
Poster 1: 18
Optimal Energy and storage abilities of super capacitors
University at Buffalo, United States of America
In terms of energy storage, conventional batteries are the most widely used technology in today’s devices and automobiles. However, they lack some qualities that capacitors can provide and are also not as environmentally friendly. Even so, Li-Ion batteries have a much higher energy density of 120-170 Wh/kg compared to capacitors at 5-10 Wh/kg which is a firm requirement for modern electronics. Super capacitors offer traits that normal capacitors cannot in terms of their energy capacity and capacitance. This type of capacitor operates by combining the technology of normal capacitors and batteries. Super capacitors use electrolyte concentrations separated by an insulator similar to a battery. Unlike batteries though, super capacitors utilize the physical movement of ions instead of chemical reactions. For this reason, super capacitors have long life times of over 100,000 cycles which makes them usable for decades without replacement. Additionally, because super capacitors take much less longer to charge and discharge they can deliver larger amounts of instantaneous power. In order to achieve the optimal energy storage device these technologies can be integrated to balance power density with energy density. Using a design composed of a Li-Ion battery in tandem with a super capacitor will be simulated in MULTISIM then built into a circuit to demonstrate the balance of energy and power in an electric motor. The energy and power will be measured using the voltage, current, and time readings provided by the circuit. The results will be compared to each of the technologies individually to emphasize the benefits of the design.
Poster 1: 19
The investigation of dielectric elastomers as non magnetic polymer motor
University at Buffalo, United States of America
Dielectric elastomers (DE) are a subgroup of Electroactive polymers (EAPs) that have the potential of exhibiting large strains in the presence of an electric field. This process produces a compressive and tensile force that causes the film membrane to reduce in its thickness and expand in area which creates linear actuation in response to the application of an electrical stimulus. The actuation of the elastomers is governed by maxwell stress and electrostriction, and this paper will investigate the efficiency and effectiveness of applying and configuring a DE a non-magnetic motor.
Poster 1: 20
Syntherization and characterization of ceramic capacitor based on BZT for use in nonlinear transmission lines
1Federal University of Sao Paulo, Brazil; 2National Institute for Space Research; 3University of New Mexico
Nonlinear transmission lines -NLTLs have been investigated as a high-power RF source to apply in radars, battlefield communication disruption, satellites, biomedical instrumentation, and other communication systems [1-2]. Another way to produce the RF signals on NLTL is using nonlinear components such as ceramic capacitors. In this work, we synthesized and characterized a barium zirconium titanate ceramic for use in nonlinear dielectrics. Its application is in NLTLs due to their high permittivity > 5000 in the phase temperature transition with low tangent loss < 0.07. The electrical characterization investigated in this work is in temperature, frequency, and DC voltage sweep, which give the nonlinearity factor of ceramic, a key parameter to produce RF in NLTL, and the dielectric strength to know the breakdown voltage in the pulsed power systems.
1. L. P. S. Neto, H. M. Moraes, J. O. Rossi, J. J. Barroso and E. G. L. Rangel, "Increasing the Voltage Modulation Depth of the RF Produced by NLTL," in IEEE Trans. on Plas. Science, vol.48, no.10, 2020, pp. 3367-3372.
2. L. P. S. Neto, J. O. Rossi, J. J. Barroso and E. Schamiloglu, “High-Power RF Generation From Nonlinear Transmission Lines With Barium Titanate Ceramic Capacitors,” in IEEE Trans. on Plas. Science, vol.44, no.12, 2016, pp. 3424-3431.
Work supported by FAPESP funding under contract number 2020/04395-3 and AFOSR FA9550-18-1-0111.
Poster 1: 21
Research on Enabling Process Optimization Methods of Metallized Film Capacitor Elements based on Self-healing Frequency Change Characteristics
1State Key Laboratory of Electrical Insulation and Power Equipment, Xi'an Jiaotong University, Xi'an, China; 2State Grid Jibei Electric Power Co., Ltd. Luanzhou City Power Supply Company
The enabling process is one of the most important manufacturing processes of metallized film capacitors, which has a great effect on the reliability. The electrical weaknesses and defects can be effectively removed by the self-healing during the enabling process. At present, the parameters used in enabling process of metallized film capacitors are empirically determined, and the influence of the parameters on the reliability has not been characterized. In this paper, electro-thermal stress test platform with DC plus harmonic AC voltage will be built. The platform is composed of programmable temperature and humidity test chamber, multi-frequency compound source and self-healing current pulse counter, etc. By changing the operating temperature and the frequency components of the operating voltage, the repetition frequency of self-healing current pulses in continuous periods of time will be recorded under various temperature and voltage frequency. A set of self-healing frequency changing curves will be obtained. Compared with the trend of the infant mortality of the bathtub curve, the most efficient and reliable enabling parameters for metallized film capacitors in different application scenarios will be summarized. This research is of great significance for standardizing and optimizing the enabling process of metallized film capacitors.
Poster 1: 22
Influence of Charge Traps on Flashover Characteristics of Epoxy Resin in Liquefied Natural Gas under DC Voltage
1Beijing International S&T Cooperation Base for Plasma Science and Energy Conversion, Institute of Electrical Engineering, Chinese Academy of Sciences, Beijing, China; 2University of Chinese Academy of Sciences, Beijing, China
Liquefied natural gas (LNG) has been widely used as a cooling medium, but its dielectric properties are poorly understood. The use of LNG as the insulating and cooling medium of superconducting energy pipeline is a milestone technology to realize the efficient transmission of power and fuel . The research on insulation characteristics of LNG is related to safe and reliable operation and technological upgrading of superconducting energy pipeline. As one of the main evaluation indexes of insulation system, flashover characteristics of LNG need to be studied in detail from two aspects of experiment and mechanism [2, 3]. In this paper, the solid-liquid interface composed of Glass epoxy laminate sheet (G10) and LNG was taken as the starting point. Firstly, the flashover voltage and current at the solid-liquid interface were measured, and the data were analyzed by using two-parameter Weibull model. Secondly, the surface morphology evolution of G10 before and after flashover was observed. Finally, the flashover mechanism is explained based on the charge trap theory, and the trap energy level and density distribution before and after flashover were measured by isothermal surface potential decay method. This research enriches cryogenic temperature insulation properties of polymer and provides theoretical and experimental support for the development of electrical equipment represented by superconducting energy pipeline.
Poster 1: 23
Density Functional Theory Calculations of Modified Work Functions for Composite Materials
1Purdue University, School of Nuclear Engineering, United States of America; 2Purdue University, School of Aeronautics and Astronautics, United States of America
Electron emission plays a vital role in numerous applications, including thermionic energy converters, electric propulsion, high-power microwave systems, and ultramicroscopy . Characterizing the electron emission and gas breakdown behavior for these devices is critical for ensuring device reliability and optimum operation. One parameter that may be tuned to adjust electron emission is the work function of the emitting material . Decreasing the work function can enhance emission for high current applications, while increasing the work function can prevent unwanted or damaging electron emission that may lead to gas breakdown in microscale devices. The work function can be modified by surface features on the electrode  and by the type of material and surface treatment used . In this work, we assess how using various composites and adjusting surface structure can alter the local work function by using density functional theory (DFT). DFT finds the equilibrium position of atoms within a supercell structure, relaxing the positions to minimize forces. The work function is calculated as the difference between the Fermi and vacuum level energies . We use the Spanish Initiative for Electronic Simulations with Thousands of Atoms (SIESTA) code, an open source code that uses a linear combination of atomic orbitals (LCAO) basis set and pseudopotentials to solve DFT problems , to examine the ability to tune work function by adjusting the composites or surface structure. The implications of this work function tunability will be assessed in the context of electron emission and microscale gas breakdown theory to elucidate potential material development for either enhancing or mitigating electron emission. We will summarize the methods and preliminary results, conjecture on potential implications on emission and breakdown performance, and discuss other applications of DFT to composite materials relevant to the power modulator community.
 P. Zhang, Y. S. Ang, A. L. Garner, Á. Valfells, J. W. Luginsland, and L. K. Ang, “Space-charge limited current in nanodiodes: Ballistic, collisional and dynamical effects,” J. Appl. Phys., vol. 129, 2021, Art. no. 100902.
 J. R. Malayter and A. L. Garner, “Theoretical assessment of surface waviness on work function,” AIP Adv., vol. 10, 2020, Art. no. 095110.
 J. M. Soler, E. Artacho, J. D. Gale, A. García, J. Junquera, P. Ordejón, and D. Sánchez-Portal, “The SIESTA method for ab initio order-N materials simulation,” J. Phys.-Condens. Mat., vol. 14, pp. 2745-2766, 2002.
This research was funded by a Purdue Doctoral Fellowship.
Poster 1: 24
Protection Assessment of Lightning Strikes on Concrete-Steel Structures simulated at full-scale
1P3E Center, ECE Dept., Texas Tech University, Lubbock, TX; 2Mission Engineering Development Group, CNS Pantex, Amarillo, TX; 3Facility Engineering Electromagnetics Group, CNS Pantex, Amarillo, TX
The ability for a structure to provide adequate shielding from the fields induced by lightning attachment is of critical importance. Steel-reinforced concrete structures offer some protection. However, these structures may contain electrical discontinuities in the rebar reinforcement that potentially reduce the structure's shielding capacity.
The induced electric and magnetic fields inside a full-scale model of a steel-reinforced concrete structure with a soil overburden are simulated in electromagnetic software to determine the effective shielding provided by the structure against a lightning protection level (LPL) category one strike. The strike attachment point and strike type (positive/negative) are varied with the fields internal to the structure, evaluated to understand the spatial relation of the strike attachment point on field magnitude. Following NFPA 780, regulation defining lightning protection systems (LPS) for buildings, a model incorporating an overhead catenary wire is analyzed to determine the field mitigation provided by the LPS. The moisture content of the structure’s concrete frame and surrounding soil, as well as soil composition, are investigated to determine their influence on the structure’s internal field levels during attachment. Additionally, the strike rise time is varied to determine the shielding capability of the structure as a function of the strike’s frequency. The simulation models are analyzed to determine a parameter space that promotes an electromagnetically resilient structure against a worst-case attachment scenario.
Poster 1: 25
Multipactor saturation variances due to changes in the SEY curve*
Texas Tech University, United States of America
Multipactor susceptibility regions, when probed through simulations based on a Vlasov-Poisson scheme using finite difference time domain methods (FDTD), show their sensitivity to small changes in the secondary electron yield (SEY) curve. Variations in the 1st SEY crossover points and shape approximations of the SEY curve can result in distinct shifts of the multipactor susceptibility regions. These changes in multipactor susceptibility regions proliferate into changes in multipactor saturation.
*This Research was supported by the Air Force Office of Scientific Research under Contract No. FA9550-18-1-0062 and FA9550-21-1-0367
Poster 1: 26
Variation of the Hull Cutoff Magnetic Field with External Resistance and Collisions
1Purdue University, West Lafayette, IN 47906 USA; 2Sandia National Laboratories, Albuquerque, NM
Crossed-field diodes (CFDs), in which a magnetic field is applied orthogonal to the electric field induced by the applied voltage across the anode-cathode gap, are used in multiple high power applications. One of the critical quantities used to characterize a CFD is the Hull cutoff magnetic field (HCMF), which represents the maximum applied magnetic field for which an electron emitted from the cathode still reaches the anode . CFDs with magnetic fields above the Hull cutoff are referred to as magnetically insulated. This Hull cutoff is a critical threshold for characterizing CFD operation since many parameters, such as the maximum stable emission current , differ depending on whether or not the CFD is magnetically insulated. However, the traditional Hull cutoff assumes a vacuum planar diode, which may not represent actual operating conditions.
This presentation investigates the implications of adding an external resistor to represent dissipation in the circuit or collisions to represent imperfect vacuum on magnetic insulation. For magnetic fields just below the HCMF, adding an external resistor can cause emitted electrons to return to the cathode. We refer to this condition as “semi-magnetically insulated,” since this onset of magnetic insulation is not steady-state. We derive equations for this modified Hull cutoff by accounting for the differences between the applied voltage and potential drop across a CFD in the presence of the resistor. We then use the 1D/3v (one-dimensional in space and three-dimensional in velocity) particle-in-cell software XPDP1 to validate these results. We further assess the modification of the Hull cutoff by incorporating collisions in a CFD. Previous theory and simulations have demonstrated that including ions in the gap could cause a loss of magnetic insulation . By incorporating electron mobility into the electron force law for a CFD, we examine changes in the Hull cutoff as a function of mobility. These results will be compared to XPDP1 simulations, demonstrating changes in magnetic insulation for various pressures. The implications on practical CFDs operating near the Hull cutoff, as studied recently theoretically and experimentally for magnetically insulated line oscillators (MILOs) , will be discussed.
 P. J. Christenson, Ph.D. dissertation, Department of Nuclear Engineering and Radiological Sciences, University of Michigan, 1996.
 B. S. Stutzman and J. W. Luginsland, “Loss of magnetic insulation in a crossed-field diode: Ion and collisional effects,” IEEE Trans. Plasma Sci., vol. 38, pp. 2010-2015, 2010.
 D. A. Packard, Y. Y. Lau, E. N. Guerin, C. J. Swenson, S. V. Lagnellotti, A. Jassem, N. M. Jordan, J. W. Luginsland, R. D. McBride, and R. M. Gilgenbach, “Theory, simulation, and experiments on a magnetically insulated line oscillator (MILO) at 10 kA, 240 kV near Hull cutoff condition,” Phys. Plasmas, vol. 28, 2021, Art. no. 123102.
Poster 1: 27
The Pulsed Magnetic Field Diffusion into Moving Metal Body with Pre-Created Gradient of Electrical Conductivity (Numerical Analysis in 2D Model of FlexPDE-6 software)
1V.I. Vernadsky National Taurida University of Ukraine in Kyiv, Ukraine; 2National Aviation University of Ukraine, Kyiv, Ukraine
The problem of the pulsed magnetic field diffusion into non-uniform media has been studied in the numerous papers and monographs, which can be called to-day as classical, mainly from the point of view when the media became heterogeneous in result of Joule’s heating in the process of intensive interaction with electromagnetic field, or when the medium initially was formatted as the mixture of heterogeneous elements or grains. Beside of such approach, today is of interest to consider the situation of pre-created non-uniform distribution of electrical conductivity coefficient (in more general case  – coefficient of magnetic diffusion) as the smooth function along one or two coordinate axes. Similar situation can be created in the process of metal sample manufacturing with a purpose to supply him the special properties. A theoretical background for such approach was prescribed by first author in the paper of 2020 year . There was shown in 2D model how the presence of electrical conductivity gradient had a specific influence on the induced current distribution which can be treated in result as appearance of correction for distribution of pulsed field applied along the normal to the plane of symmetry of model. For the numerical analysis of this process has been chosen a software FlexPDE-6.37 due to principal ability to introduce the gradient of electrical conductivity into system of the field equations as pre-defined smooth function of coordinates, for example, exponential one. The performed numerical experiments provided a demonstration of additional way to control the speed of pulsed field diffusion in the non-uniform sample. Taking into account the velocity of sample movement had allowed to view the process diffusion both for the motion of sample out of applied magnetic field source (a mode of the field decompression) and for the moving to (a mode of the field compression). The results of simulation has been illustrated by the graphics, which represent distribution of electromagnetic quantities along the plane of model at different form pre-defined coefficient of electrical conductivity. The program for the FlexPDE-6.37 which has been used by authors can be included in the appendix of the full description of this work.
(1) Volodymyr T. Chemerys, Associate Professor (per 1/2 day) of the V. I. Vernadsky National Taurida University in Kyiv, Department of Automatic Control of Technological Processes. Build. 31, John McCane Street, Kyiv, Ukraine, 01042. E-mail: email@example.com.
(2) Iren O. Borodiy, Assistant of Professor, Department of Physics at National Aviation University of Ukraine.
Build 1, Cosmonaut Komarov Ave., Kyiv, Ukraine, 03680. E-mail: firstname.lastname@example.org.
 Isaak D. Mayergoyz, Nonlinear Diffusion of Electromagnetic Fields (with Applications to Eddy Currents and Superconductivity), New York: Academic Press, 1998.
 Volodymyr T. Chemerys, “Specifics of Pulsed Magnetic Field Penetration…”, IEEE Trans. on Plasma Science, vol. 48, no. 7, July 2020, pp. 2608 – 2617.
Poster 1: 28
The physical model of explosive ion emission
Kore-Science, LLC, United States of America
Explosive Ion Emission has been discovered by Dr. Sergey Korenev in 1985 
Poster 1: 29
Wavelet Based Feature Extraction From High Voltage Impulse Signal
1Istanbul Technical University, Turkey; 2University of California, Riverside, California USA
WAVELET-BASED PARAMETER ESTIMATION OF
HIGH VOLTAGE IMPULSE SIGNALS
In transmission and distribution systems, electrical equipment is commonly exposed to impulse voltage and currents produced by lightning strikes and switching operations. Transformers, insulators, cables, overhead lines, and other electrical equipment suffer malfunctions and insulation problems leading to short circuits and interruptions in electrical networks.
The parameters of peak value, front time, time to half value, and time to chopping are substantial variables in producing a standard impulse waveform. Nevertheless, disturbances like oscillations and/or overshoots may occur in the impulse signals, preventing accurate and precise testing of high voltage equipment. The frequency range of disturbances varies depending on the source such as the equipment itself, test and measurement systems, and ambient conditions. Eventually, the k-factor filtering approach was suggested in the IEC 60060-1 standard. In this method, the disturbance of oscillations and overshoots are removed from the impulse signal by residual filtering using the k-factor approach.
This study is focused on wavelet-based analysis for the evaluation of impulse signals providing curve fitting and the filtering of disturbances resulted from oscillations and/or overshoots. A wavelet transform has the significant features of presenting time and frequency information at the same time while enabling signal de-noising naturally. Fourier based transforms suffer fixed resolution of window function while wavelet-based approaches provide better time and frequency resolutions. A wavelet-based transform provides sub-band decomposition while presenting curve fitting and de-noising in each level of resolution.
In this context, wavelet based multiresolution analysis was introduced as a suggestion for k-factor filtering. Real time impulse signals are produced and measured using an impulse generator and an oscilloscope. Then, the sampled waveforms were analyzed through k-factor filtering and wavelet based multi-resolution analysis. The mean curves and impulse parameters for each sampled signal are calculated using both methods. Afterwards, the differences in the calculated parameters are analyzed in terms of relative errors. An evaluation of the proposed method in comparison to the IEC approach is provided.
In this study, a comparison of the filtering approaches of k-factor and wavelet-based decomposition is provided. The procedures for each approach are introduced. The steps for optimal wavelet function selection and assessment of sub-band levels are discussed. And the results, obtained by the application of multi-resolution wavelet analysis and the IEC 60060-1 approach are evaluated. The analysis is conducted on several impulse signals produced by the experimental setup. The decomposition level and the wavelet function are determined through the procedures given at last.
In the conclusion, the findings and the contributions of this research are presented. As an alternative solution, the opportunities of multi-resolution wavelet analysis over k-factor filtering are discussed. Based on a numerical analysis, it is found that wavelet-based multi-resolution analysis provides very close results to the k-factor approach. In addition, it is shown that the proposed wavelet-based approach provides a compact solution for curve fitting and filtering while enabling further evaluation of frequency content for each sub-band of high-voltage impulse signals.