Conveners
Poster - Microwave Generation and Plasma Interactions and Pulsed Power Switches and Components
- Joel Ennis (NWL)
- Jason Sanders (Transient Plasma Systems, Inc.)
- Jose Rossi (National Institute for Space Research)
We present simulation results which demonstrate that a relativistic magnetron can be operated with permanent magnets. Using permanent magnets makes the magnetron a more compact device. In a recent paper (Leopold et al., IEEE-Trans. Plasma Sci., vol. 44, no. 8, pp 1375-85, 2016) we showed that the power balance in an A6 single radial output magnetron with its longitudinal slots covered by anode...
A simple 1D model of the propagation of an ultra-short (≤ 1ns), TM01 mode, 28 GHz, ~1 GW, microwave pulse produced by an SRBWO (Super Radiant Backward Wave Oscillator) in a ~10$^{10}$ cm$^{-3}$ density plasma shows that a wakefield develops as a result of the radial ponderomotive and the Lorentz force. This is a scaled-down equivalent of a laser wakefield experiment with more manageable...
An axial virtual cathode oscillator is experimentally analyzed depending on the transparency of the mesh anode. The axial virtual cathode oscillator is operated using a 140J/170kV Marx generator. A stainless steel cathode and stainless steel mesh anodes with different transparency are used as a high power microwave generating diode. The gap distance of the virtual cathode diode is 4 mm. To...
We presented the design of a 190 GHz dual mode OAM gyrotron with axial output configuration for a prototype experiment of Orbital Angular Momentum (OAM) communication. A mode pair of second harmonic modes ($\rm TE_{8,3}$/$\rm TE_{11,2}$) is excited at 28/35 kV, 5A electron beam input in the presence of a uniform magnetic field of 3.56 T. It incorporates a perturbed cavity with two sinusoidal...
The rippled-field magnetron is a compact millimeter wave source developed by Bekefi [1]. This source is driven by a rotating electron stream. The electron stream moves through an azimuthally periodic wiggler magnetic field oriented transversely to the flow and a uniform axial magnetic field. The advantages of this circular device compared to linear devices is that the beam circulates...
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 useful if not required. In a precedent study, CEA worked on a very compact HPEM source named CLAIRE. The used tube was an optimized X-band sub-gigawatt...
A Ku band tape helix TWT with a center frequency of 13.25 GHz which was chosen for the RF driver present in our lab for a future prototype, was modeled and simulated using CST MWS and CST PS. Connectors for the RF input and output were also modeled in two different types. Firstly, a 50 Ohm coaxial connector was modeled and directly coupled to the helix and secondly an impedance matching...
We present our current progress towards the development of a novel RF source
utilizing a low-loss, dispersion engineered, artificial EM material, based upon
a complementary split ring resonator that supports both forward and
backward wave propagation. The frequency dispersive media was designed
numerically to yield specific constitutive parameters, determined using a
Nicholson Ross Wier based...
In this paper, novel S band metamaterial based rectangular slow-wave structure (RSWS) is proposed for high power backward-wave oscillator (BWO). The circular waveguide is loaded with R-SWS that shows negative permittivity and permeability. Since RSWS shows the negative permittivity and permeability which is the key characteristics of metamaterial, it can work below the cut-off frequency. A...
Magnetrons can be phase-locked using external systems. Previous 2-D PIC simulations of a rising sun magnetron[1] have shown that phase-locking is possible using modulated electron injection to control the spoke formation. An experimental setup using Gated Field Emission Arrays (GFEAs) for the modulated electron injection offers a potential solution to this problem by permitting the injection...
Nonlinear transmission lines (NLTL) have demonstrated the ability to convert a low-frequency video pulse into a narrowband RF packet whose frequency may vary from pulse to pulse. Synchronous wave magnetic NLTLs achieve this via a DC current bias prior to the launch of a video pulse which sets the subsequent shock velocity and thus the RF frequency. This paper explores the idea that a dynamic...
Magnetron with Diffraction Output (MDO) possesses advantages like direct couple to axial output waveguide; hence it has higher output extraction efficiency. Like traditional magnetron, MDO also requires an axial magnetic field to force the explosive field emitted electrons to go into a spiral motion and form resonant fork, and unlike low power traditional magnetron where the B field is formed...
There has been tremendous progress in the modeling and simulation of high-power microwave devices, especially in the lower frequencies, such as L-band (1-2GHz) and S-band (2-4GHz). Here we look at significantly higher frequency, 14GHz, while still studying a tube with GW-class power levels [Tao Jiang et. al. Phys. Plasmas 2015]. The choice of this Ku-band allows both high frequency and high...
Two dimensional (2D) periodic surface lattices PSLs have been used successfully in both fast-wave sources [1] and in slow-wave sources [2-4]. Numerical simulation codes have been used to design an electron beam driven W-band millimeter-wave source, in which a cylindrical two dimensional (2D) periodic surface lattice (PSL) forms an over-sized mode-selective cavity. The 2D PSL consists of...
A growing interest has been rising around the use of Gyromagnetic Nonlinear Transmission Lines (GNLTLs) for Radiofrequency (RF) generation since recent results that were published has demonstrated great prospects for this end. The interest on this type of transmission line comes from the high RF conversion efficiency around 20.0% according to some works already elaborated, what shows a great...
We are exploring the amplification of W-band electromagnetic radiation using a dielectric-loaded traveling wave tube (TWT) by employing several particle–in–cell (PIC) codes. We are seeking to replicate recent results obtained by a Naval Research Laboratory’s (NRL’s) dielectric–loaded TWT design [1] consisting of a solid circular electron beam (26 kV, 100 mA and 0.185 mm beam radius) surrounded...
Nonlinear Transmission Lines (NLTLs) has been used for RF generation with great success. Possible applications of NLTLs as an RF generator include aerospace radars, telecommunications, battlefield communication disruption, etc. The RF pulses generated by the NLTLs can be radiated using antennas connected to the output of the lines. Also, there has been a paucity in the literature considering...
An E-band relativistic backward wave oscillator (RBWO) is proposed to generate megawatts of power. An overmoded rectangular slow wave structure (SWS) is chosen and combined with a relativistic hollow electron beam to increase the interaction impedance and avoid RF breakdown. To overcome the frequency limits of conventional fundamental mode version, a higher order mode is selected as the...
We present results of 3D ICEPIC simulations of a relativistic X-band (9.9 GHz) twistron based on a design reported in the literature. Here we report on progress made in our hot test simulations of this device. Full 3D ICEPIC simulations were made using the supercomputers of the DoD Supercomputing Resource Centers (DSRCs). Our hot test simulations used a 373 kV, 6.5 kA annular beam with 13.75...
Surface inhomogeneities can have a large impact on field emission, because it is strongly dependent on the local value of the surface electric field and work function of the metal. Within a given area the bulk of the emitted current may stem from a protrusion where the field is enhanced, or from a site where the work function is lower than in the surroundings. In systems that are large these...
The next generation high frequency tubes will face significant challenge in focusing the beam into small aperture for beam-wave interaction. The efficiency of such tubes will depend largely on available beam energy that will interact with electromagnetic wave as the beam is transported. Unlike low frequency tubes, emittance is emerging as a major concern since beam loss at the wall or at the...
Fusion energy promises nearly unlimited, clean energy. One approach to fusion energy production is by means of inertial confinement fusion experiments where a fuel boundary exists (e.g., fuel-liner or fuel-ablator). Unfortunately, in the presence of a wide variety of energy loss mechanisms, obtaining a net gain in energy remains a challenge. The mixing of cooler materials into hot regions can...
Generation of high density and energetic electron beams of short duration are important in growing areas such as the generation of extreme ultraviolet/X-ray radiation, microwaves, THz radiation and for biomedical and radiography applications [1-2]. A pseudospark discharge (PSD) has the ability to produce the combined highest current density (>108A/m2) and brightness (~1012Am−2rad−2) electron...
Numerical heating due to the mesh size being larger than the Debye length is well understood for collisionless PIC simulations [1]. However, the importance of grid heating in collisional, partially ionized plasmas such as streamer discharges is less understood. In these plasma regimes the artificial heating of the plasma can, at least theoretically, be mitigated by collisional energy transfer...
The design and the development of High-Power Microwave (HPM) sources today relies heavily on Particle-In-Cell (PIC) codes, which allow the source concepts to be virtually prototyped and optimized prior to being built experimentally. The current state of source development consists of developing the geometry of the structure, extracting the dispersion relation from the eigenmodes, evaluating...
Maxwell’s equations based vector potential formulation of electromagnetism is widely used in classical and quantum physics. However, in PIC simulations, the community has primarily focused on Maxwell’s equations in first-order form, exploiting the explicit Yee method for the fields with the Boris push for the particles. However, a challenge with this approach is geometry. The community has...
L3 Applied Technologies is developing series pulsed forming water transmission lines for Los Alamos National Laboratory. The Series Pulse-Line Integrated Test Stand (SPLITS) consists of a set of four, 5.5 ohm coaxial water pulse forming lines in series. Each water line is capable of producing a -300 kV pulse when driving a matched resistive load.
As part of this effort, the University of New...
Gas recirculation effects have been modeled following a nanosecond-pulse high-voltage discharge across a pin-to-pin air gap, where subsequent pulses in a burst have been found to couple very efficiently if the repetitive pulses occur above a critical frequency. Previous data from the same pulse discharge system indicated that the inter-electrode gas temperature increased rapidly following...
Multipactor is a nonlinear phenomenon driven by an rf electric field in which secondary electron emission from metallic or dielectric surfaces, leads to an exponential growth of charge. It is harmful to satellite communications and microwave systems [1]. Here, we apply Monte Carlo (MC) simulation [2] to study the multipactor susceptibility in a gap between two parallel metallic electrodes....
Verus Research designed and modeled a novel plasma switch assembly to optimize the mechanical and electrical characteristics required to create an efficient and reliable family of switches for megawatt sources. There is a need in the high-power community for a fast rise-time High Power Radio Frequency (HPRF) pulse shaping tool to augment slow risetime HPRF sources, such as magnetrons, to...
High Power Microwave (HPM) is a proven effective mean to suppress electronic system or disable Unmanned Aerial Vehicle (UAV) because the power level can be as high as GW, however, due to basic limitation from antenna theory, the power per unit area quickly decline when the distance to target increases, therefore difficult to extend the effective range to more than a few km. Elaborately...
The propagation of moderately high energy (10-100 keV) electron beams through gas-filled tubes has been being long studied for various potential applications, such as microwave generation, EUV/X-ray radiation and surface modification [1-3]. However, it appears that not much attention has been paid to understand the mechanism as to how the e-beam cross-sectional shape affects the breakdown of a...
An experimental setup to study plasma generated at the focus of a continuous-wave (CW) microwave beam was designed and constructed at the Air Force Research Laboratory at Kirtland AFB, NM. Experimental studies of free space plasma are of interest because they can help validate and improve theoretical models, such as the Improved Concurrent Electromagnetic Particle-In-Cell (ICEPIC) code. Free...
Despite decades of research, understanding and prediction of multipactor in complex geometries remains predominantly empirical. This results in large safety margins in RF design, driving up production and deployment costs to prevent costly operating disruptions or complete device failure.
As part of a Multi-University Research Initiative (MURI) led by Michigan State University, the University...
Multipactor discharge is a major concern in a multitude of electromagnetic devices, often requiring suppression to properly operate devices and avoid damage. The factors affecting multipactor discharges are mainly from the dielectric window properties and the field distribution. Modifying the window geometry including periodic grooves on the window surface in rectangular or triangular shape,...
As a non-linear medium, plasma can exhibit diverse dynamics when excited by multiple EM waves. Electromagnetic waves are vital to the introduction of energy in laser plasma interactions and the heating of magnetically confined fusion reactors. In laser plasma applications Raman coupling via a Langmuir oscillation or Brillouin scattering mediated by ion-acoustic waves are of interest. Signals...
Introduction
Fast and repetitive switching in high-power circuits is a challenging task where the ultimate solutions still have to be found. Areas of application are power switches in high-voltage networks and heavy duty switches for pulsed power applications.
Supercritical switch media
We propose a new approach: the use of supercritical fluids as switching medium. Supercritical fluids have...
Large Hadron Collider (LHC) - the world biggest and highest energy proton accelerator/collider is built on Switzerland/France border at ~100 m underground. Its circumference is 27 km and it will accelerate up to 4e14 protons per beam to a peak energy of 7 TeV. Under these conditions energy of each beam will be 360 MJ. Safe dumping of the beam with such energy is crucial for the safety of the...
Reliable operation of the Large Hadron Collider Beam Dumping System (LBDS) is vital for the machine safety. The role of the LBDS is to extract two counter rotating beams and to dispose of them safely on their respective 8 m long graphite dump blocks. The LBDS consists of 50 pulse generators located in the LHC galleries: each generator is connected to a kicker magnet by, 30 m long, coaxial...
High power plasma switches, such as, hot and cold cathode thyratrons have always been the key components of pulsed power systems including pulse modulators, linear accelerators, synchrotron sources, crowbar circuits, cargo scanning systems, sterilization, etc. These switches are classified by their unique pulse characteristics and performances. The unique features of hot cathode thyratron are...
Pseudospark discharge are widely used in high power switches, intense electron beam generation and extreme ultra violet light source. Current quenching is one of the most important problems that seriously hamper the applications of the pseudospark discharge, which is characterized by the appearance of sudden current interruption and inductive voltage spikes at the same time. In this paper,...
This work describes laboratory measurements of recently-fabricated, state-of-the-art Silicon Carbide (SiC) Insulated-Gate Bipolar Transistors (IGBTs) developed for medium-voltage converters and pulsed-power applications. These next-generation, monolithic devices, have an active area of 0.3 cm2, a drift region of 160 µm, and are rated for 20-kV and 20 A. The IGBTs were co-packaged with SiC...
The surface defect states of GaAs substrate may cause surface flashover which results in the immature breakdown of the GaAs based photoconductive semiconductor switch (PCSS) devices. It is also expected that the shorter carrier life time and the high surface recombination velocity at the GaAs surface have impact on the performance of GaAs based PCSS devices.
In this study, the surface...
Silicon carbide (SiC) based photoconductive semiconductor switches (PCSSs) are interesting because of their potential for higher voltage operation originating from the excellent material properties of SiC. However, the experimentally demonstrated performances of the SiC based PCSSs are still far inferior to those of the GaAs counterpart. To harness their potential inherited from the excellent...
Gas-discharge closing switches usually have more poor repetition performance than semiconducting switches. This is due to the recovery of gaseous insulation takes a lot of time, and can restrict the use of the gas switch in repetitive applications. The corona-stabilized switch is a potential plasma closing switch that has excellent PRF (pulse repetition frequency) capability. The electric...
Gas-discharge closing switches have poor repetition performance, which is due to the gaseous insulation will decrease for a short time after the last breakdown , and therefore the gas switch will usually close at a much lower voltage than the initial breakdown voltage. The corona-stabilized switch is based on corona stabilization phenomenon that a space charge develops around the highly...
High explosive pulsed power experiments conducted by Lawrence Livermore National Laboratory employ several different triggered closing switches. Since experiments are single-shot events, failure in any one of these switches can be catastrophic to the experiment outcome. Thus, repeatability and reliability are key metrics in the assessment of closing switch performance. Presented in this paper...
HERMES III is a 20-MeV linear induction accelerator that was constructed at Sandia National Laboratories in the late 1980’s and continues operation to this day. The accelerator utilizes 10 Marx banks for its initial energy storage and pulse formation. These Marx banks discharge their energy into 20 intermediate storage capacitors which, in turn, feed 80 pulse forming lines that further...
Mixed-Mode modeling, is a combination of SPICE circuit and finite element device physics, is used to evaluate SiC drift step recovery diode structures for optimal operation as opening switches for the generation of narrow high voltage pulses in a single loop resonant LC circuit. This comparison is made as a practical means to define device design elements and process steps prior to the...
Pulsed gas discharge is an important means of generating low temperature plasma. Short pulses with fast frontier show superior performance in terms of increasing the active particle content, ionization coefficient and electron conversion rate due to its higher voltage rise rate. The common nanosecond pulse generator is based on capacitive energy storage. Compared with the nanosecond pulse...
Cable is the main component of the network of power system. It is usually laid in the underground corridor and its function is to transmit and distribute electrical energy. As with further development of urban construction, cable usage is inevitablty getting higher and higher in hub substation with 110kV or higher voltage levels. Meanwhile, high voltage single-core XLPE insulated power cables...
Typical pulsed power applications cover the field as e.g. collision and fusion experiments or the generation of high temperatures, as well as the generation of X-rays in medical applications [1]. In these applications, pulsed power modulators are used for generating highly accurate high voltage pulses with very fast rise and fall times and pulse widths from microseconds to milliseconds. In...
The University of New Mexico has designed and built a 10-stage high energy Marx generator with a pulse length of 1.5 Microseconds. This Marx generator has the capability to drive low impedance HPM loads such as the Magnetically Insulated Line Oscillators as well as HEDP loads like a DPF. A transmission line coupling the Marx to the load is the typical energy transfer mechanism for such a...
A 1 MV transformer, based on Tesla technique, was designed and most of its components were already manufactured. The paper will present the calculations performed for obtaining an optimum design for the major components of the arrangement, such as the windings and the 1 MV switch connecting the load.
High voltage insulation methods that can easily be assembled and disassembled are of use on compact pulsed power systems. High voltage isolation systems are a key element for reliable pulsed power operation. Verus Research’s Dense Plasma Focus (DPF) system, under development as a radiation test source for the U.S. Army, requires an electrical-mechanical interface that can withhold a minimum of...
The high voltage repetitive frequency nanosecond pulse (RFNP) generator is an important equipment in many industrial and scientific applications, including the plasma-assisted combustion and plasma-surface interaction. The gas-insulated gap, one of the typical insulation infrastructures, is required to withstand RFNP. It is usually accepted that the insulation capacity of the gas gap under...
One of the main limiting factors in the design of high-power vacuum systems is a surface flashover occurring over the insulator surface between two conducting regions separated by a high-voltage gap. To decrease the probability of this phenomenon, traditional approaches include an increase in the area of insulators, screening tricks of triple junctions and limitation techniques of the...
With the increasing usage of sulfur hexafluoride, the disadvantages of its high GWP are becoming increasingly prominent. Therefore, looking for alternatives to SF6 gas to promote gas-insulated technology to an environmentally friendly direction has important engineering and practical value. The mixture green gas C4F7N/CO2 which is most potential to subscribe SF6 arouses the concern of the...
SF6/N2 gas mixtures has the huge potential. However, due to the inevitable insulation defects in high voltage apparatus, partial discharge is caused, and then the mixture is decomposed, which ultimately endangers the safe operation of the equipment. The study on the decomposition of SF6/N2 mixtures in corona discharge is of guiding significance to the timely detection of early failure of...
SF6, an insulated gas with high dielectric strength, is widely used in the power system. However, SF6 is one of the six limited greenhouse gases specified with a GWP of 23500. Therefore, it is necessary to assess a candidate as alternatives to SF6 in electrical equipment.
In this paper, a new insulating media C5F10O with a GWP value of only 1 and a dielectric strength twice that of SF6 is...
In recent years, C5F10O has become one of the most promising alternatives to SF6.Not only because it fundamentally solves the issue of greenhouse effect of SF6 with the GWP of 1, but also, thanks to its high content of fluoride, the insulating strength of C5 is twice as good as SF6.However, the liquefaction temperature of C5 is 27℃ under normal pressure, so the most crucial challenge for it...
As naphthenic mineral oils are classified as a Class 1 water hazard, both the power and pulsed power industries are actively investigating suitable replacement liquid insulation. Natural and synthetic ester liquids present a possible alternative to these naphthenic mineral oils, primarily due to their comparable dielectric properties. Furthermore, ester liquids offer a number of additional...
In large machines, such as accelerators and high power microwave systems, it is common to implement pulsed power technology. Pulsed power attempts to deliver large amounts of power in a short amount of time. This is done by generating high voltage and delivering that energy to the desired load quickly through switches. To ensure that the energy is delivered to the desired load it is necessary...
A reactor being developed and instrumented for plasma decomposition of carbon dioxide contains a pin-to-plane microdischarge, with a stainless steel pin and aluminum electrode. The degradation of the aluminum electrode over testing time is an unwanted effect of this particular system. A predictive model of degradation of the current electrode is being developed to relate the system parameters...
