Baruch Levush

Baruch Levush
United States Naval Research Laboratory | NRL · Electronics Science and Technology Division

PH.D

About

638
Publications
27,969
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8,065
Citations
Citations since 2017
22 Research Items
1932 Citations
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20172018201920202021202220230100200300
20172018201920202021202220230100200300
20172018201920202021202220230100200300
Introduction
Skills and Expertise

Publications

Publications (638)
Article
We present an overview of the progress made by our Naval Research Laboratory (NRL)-based group over the last 25 years in the development of computational tools used in the large-signal modeling and design of linear-beam vacuum electronic (VE) amplifiers, klystrons, and traveling-wave tubes (TWTs). These tools belong to a class of codes that we call...
Article
A theory and general method for calculating self-excitation thresholds for a large class of standing and traveling-wave structures used in amplifiers, klystrons, traveling-wave tubes, and other vacuum electronic devices (VED) is presented. One determines the circuit parameters of RF structures that are changed due to the presence of electron beam a...
Article
We present the experimental demonstration of a traveling-wave tube (TWT) power amplifier operating in the ${W}$ -band (75–110 GHz) frequency range. The device is based on a serpentine waveguide (SWG) amplification circuit, a slow wave circuit type capable of high power and broad instantaneous bandwidth in the upper millimeter-wave range. A 20 kV,...
Article
We present a new approach to the study of the stability of vacuum electronic devices (VEDs) using the Naval Research Laboratory (NRL) large-signal code TESLA-Z. The approach combines a precomputed complex impedance matrix, $\hat {Z}$ , describing the structure with a TESLA-Z computed admittance matrix, $\hat {Y}_{ \boldsymbol {bt}}$ , character...
Article
We present the results of our comprehensive study of the stability of a two-gap input cavity used in an experimental broadband multiple-beam klystron (MBK) with 18 beams and 7 cavities, which was designed for projected >500 kW maximum output power and ~ 13% bandwidth (so-called NRL MBK-3 design). The device was experimentally observed to be prone t...
Article
We present a computationally efficient method for the calculation of impedance matrices of a large class of standing- and traveling-wave structures used in klystrons, traveling-wave tubes, and other vacuum electronic (VE) devices. By treating the gaps as "lumped ports," this method avoids the time and disk spaces consuming steps employed in [1], wh...
Article
We have developed a general approach to modeling a large class of vacuum electronic devices (VEDs) by using impedance matrices to characterize the circuit structure. Our approach can treat VEDs that have an arbitrary number of interaction gaps, severs, and input and/or output ports that may incorporate arbitrarily complex matching and/or tuning ele...
Article
A new computationally efficient 2-D large-signal code TESLA-FW has been developed to model traveling wave tubes (TWTs) using folded (or serpentine) waveguide (FW) slow-wave structures. The code incorporates a recently published shunt-loaded transmission line model of the structure and takes advantage of a new time advance algorithm recently impleme...
Conference Paper
Recent advances in the development of millimeter wave vacuum electronic devices have been made possible by powerful, specialized design tools. We summarize them here and point out areas where improved models and codes will be needed.
Conference Paper
Drive Induced Oscillations (DIO) manifest themselves as spurious oscillations at frequencies close to the edges of pass-band of periodic structure in vacuum electronic devices operating in the large signal regime. DIO in coupled cavity TWTs (CC-TWTs) is most known effect and it has been extensively studied experimentally 1 since it is the major lim...
Conference Paper
We present the demonstration of the first traveling wave tube circuit fabricated using ultraviolet photolithography. The complete amplifier demonstrated over 60 W output power at 214.5 GHz with 15 GHz bandwidth in the small signal regime at 14 dB gain. A high-gain 233 GHz amplifier is now under development and predicted to reach over 100 W output p...
Article
A technological breakthrough is embodied in the successful demonstration of an extended interaction klystron (EIK) amplifier, which has produced over 7.5 kW of peak output power at W-band (94 GHz). An efficiency of ${sim}{17%}$ has been achieved with a depressed collector. The EIK is driven by a 20-kV, 4-A sheet beam in a permanent magnet solenoid,...
Article
A recently published hybrid circuit model for folded-waveguide slow wave structures has been implemented in the 1-D large signal code CHRISTINE. The resulting code is applied to a design for a G-band (220 GHz) folded-waveguide traveling wave tube. Results of small and large signal gain are compared with those from TESLA, a 2-D code using the same c...
Article
Full-text available
We present the first vacuum electronic traveling wave amplifier to incorporate an interaction circuit fabricated by ultraviolet (UV) photolithography and electroforming, demonstrating over 60 W of output power at 214.5 GHz from a 12.1 kV, 118 mA electron beam. The tube also achieved an instantaneous bandwidth of ${sim}{rm 15}~{rm GHz}$ in $G$ -band...
Article
The general electromagnetic properties and design methodology for serpentine/folded-waveguide (FW) amplifiers are presented. In addition, hybrid-waveguide circuit topologies, which permit greater design flexibility than the basic serpentine/ FW topologies, are also introduced, and their dispersion characteristics are discussed. Experimental validat...
Conference Paper
An extended-interaction oscillator (EIO), driven by a 20-kV, 4-A sheet electron beam having a cross section of 0.3 × 4 mm, is described. This new EIO is an outgrowth of our recently demonstrated sheet-beam-driven, 94-GHz extended interaction klystron (EIK) amplifier, which has produced a peak power of over 7.5 kW. 1, 2 The size and weight of these...
Conference Paper
The design of a traveling-wave tube (TWT) amplifier chain capable of 2.5kW of peak RF output power and > 1.5 kW of power over the frequency band of 92 – 100 GHz will be presented. This amplifier configuration is comprised of a driver TWT and two serpentine TWT power boosters, which are cascaded in series. The driver TWT is driven by a 122 mA, 20 kV...
Conference Paper
The development of a broadband multi-kW Ka-band PPM focused TWT driver-booster combination is reported. The driver is an existing broadband coupled-cavity TWT 1 , employing a 2 stage depressed collector. The power booster is a newly designed sever-less folded waveguide TWT designed to provide 3–4 dB of additional gain 2 . The booster also uses a 2...
Article
A sheet-beam coupled-cavity traveling wave tube has produced over 10 kW of peak power at a center frequency of 34 GHz, with a 3-dB bandwidth of almost 5 GHz. The power of this amplifier is an order of magnitude higher than state-of-the-art conventional amplifiers of comparable frequency, bandwidth, and operating voltage $({<}{rm 20}~{rm kV})$ . Thi...
Conference Paper
The design of a high-gain single-stage TWT amplifier is presented. This amplifier will be driven by a 124 mA 20 kV electron gun currently under development. Output power is expected to be more than 80 W across the 231.5-235 GHz band at 113 mW of input power. Predicted saturated output power is more than 140 W, which can yield 23% overall efficiency...
Conference Paper
We describe our progress on the development of a Ka-band TWT driver-booster combination to produce >1kW over a 5 GHz band centered at 35 GHz. The driver is an existing > 500 Watt broadband coupled-cavity TWT1, employing a 2 stage depressed collector. The power booster is a newly designed sever-less folded waveguide TWT designed to provide 3-4 dB of...
Conference Paper
We report on the extension and further generalization of two different large-signal models suitable for the 2D modeling of TWTs based on different types of slow-wave structures. The initial implementation of the 2D large-signal codes TESLA-CC and TESLA-FW has been generalized in such way to create a single algorithm with modular extensions that can...
Conference Paper
We describe a new formulation for the electromagnetic fields in an arbitrary slow wave structure that can be used in the 2D large-signal modeling of beam-wave interaction. The main idea is to represent fields in the portions of the structure not occupied by the beam as a superposition of whole structure modes. This approach generalizes that based o...
Conference Paper
NRL's unique sheet-beam electron gun, which produces a 3.5-4-A, 0.3 × 4 mm electron beam at ~20 kV, has been successfully used to power multi-kW amplifiers at both Ka and W bands. The 94-GHz narrow-band EIK uses a 3-cavity circuit to produce a peak output power of over 7.5 kW, with saturated gain of ~35 dB. The Ka-band amplifier uses a double stagg...
Conference Paper
Results of comprehensive modeling of drive induced oscillation (DIO) excitation in CC-TWTs are presented. For modeling of DIO onset the CC-TWT design code TESLA-CC has been extended to be capable of multi-frequency simulation. The results of TESLA-CC modeling of DIO onset are in reasonable agreement with the measurements. Different techniques for D...
Article
A new approach implemented in the MICHELLE-eBEAM code [Ovtchinnikov etal, J. Vac. Sci. Technol. B 28, C6J8 (2010)] is designed to take advantage of the graphics processing unit hardware acceleration using novel algorithms to capture inter-particle interactions accurately and efficiently. This approach is used in the simulation of counter streaming...
Conference Paper
To meet the need to transmit increasingly massive volumes of data, both the defense and commercial sectors are turning to higher operational frequencies to take advantage of larger signal bandwidths while concurrently requiring increased amplifier power to achieve the necessary signal-to-noise ratios over large transmission distances. In response t...
Article
We describe an equivalent circuit model for traveling wave structures based on folded or serpentine waveguides (F/SWs), including a beam tunnel. The model consists of a combination of transmission line segments and lumped electrical elements. Values of the five parameters that characterize the model are found by minimizing the differences between t...
Conference Paper
The 2.5D large-signal code TESLA-FW was recently developed with the goal to model TWT amplifiers based on the serpentine or folded-waveguide slow-wave structures. Predictions of the large-signal code, applied to the modeling of the single stage amplifiers, were found in a good agreement with the results of the 3D PIC code MAGIC, while its run-time...
Conference Paper
Simulations of modern, high current electron beam lithography devices may require modeling of optical components and multiple electron sources that are positioned in an oblique fashion with respect to the main device axis and include counter streaming regions, where two beams are co-located in space while propagating in opposite directions. Modelin...
Conference Paper
Results are reported from a comprehensive study of the dispersive properties of serpentine and folded waveguide circuits. The dependence of various features of the dispersion on geometrical parameters is illustrated. Comparisons with predictions of a model circuit consisting of a periodically loaded transmission line are presented.
Conference Paper
Full-text available
This paper presents theory and analysis of single-tip field emission and electron beam propagation in the electrostatic focusing fields. It is shown that two gate apertures with a focusing anode allow transport of narrow electron beams over long distances without need for a confining magnetic field. Physical mechanisms of the beam formation, transp...
Conference Paper
form only given. A compact, 94-GHz extended interaction klystron (EIK) amplifier has been developed and tested. A peak power of over 6.6 kW has been measured at the output flange of the device (in air), corresponding to over 8 kW at the output cavity aperture (in vacuum). The observed output is in excellent agreement with 3-D PIC simulations. The E...
Conference Paper
Serpentine or, its cousin, the folded waveguide (FW) traveling-wave tubes (TWTs) are a class of vacuum electronic devices capable of wideband, high-power performance. This was first demonstrated in [1] with several Q-band 2-stage TWTs that produced 135 W of average power and saturated gains of ~30 dB over an impressive 25% instantaneous bandwidth....
Conference Paper
We present a technique for time-domain measurement and predistortion of complex wideband waveforms in a Ka-band helix TWT power amplifier. The measurement technique relies on a hybrid calibration procedure that uses both single tone and wideband multitone calibration for characterizing the amplifier response to simultaneous excitation across its op...
Conference Paper
The U.S. Naval Research Laboratory has been developing a novel UV-LIGA process to create amplifier circuits from 100 GHz through the THz. A 670 GHz EIK ladder test piece has been successfully fabricated with a 0.004 inch diameter beam tunnel, and demonstrates sub-micron fabrication accuracies. The technique is being extended to showcase capabilitie...
Conference Paper
A two stage 'driver-booster' TWT configuration designed to produce 1.8 kW in Ka-band will be described. The folded waveguide circuit used in the power booster is designed to meet bandwidth requirements while simultaneously eliminating the usual stop-band at 2π, in order to avoid drive-induced oscillation.
Conference Paper
We present the hot test results of a 220 GHz, serpentine waveguide vacuum electron amplifier showcasing a novel embedded monofilament microfabrication technique based on UV-LIGA. The instantaneous operating bandwidth exceeds 15 GHz and the small signal gain of the circuit is over 14 dB. By varying the voltage slightly, an operating bandwidth of alm...
Conference Paper
We are developing a wideband 95-GHz, 200-W TWT powered by a 20-kV, 122-mA electron beam. The serpentine waveguide circuit is fabricated by UV-LIGA using an embedded monofilament, which produces an all-copper structure with beam tunnel. Simulations predict 37 dB small-signal gain and 245 W maximum output power.
Conference Paper
The design of a W-band serpentine TWT with >200 W of power over a 4 GHz bandwidth (>100 W over 7 GHz) is presented. The amplifier is driven by a 122mA, 20 kV electron beam generated by a slightly modified version of the demonstrated 670 GHz beamstick at a reduced magnetic field. The design was performed by both the established MAGIC-3D and the rece...
Conference Paper
Progress on the demonstration of a high power broadband three-beam Ka-band cascaded traveling-wave tube (TWT) prototype is presented. The amplifier will be driven by an electron gun (0.6 A × 3, 20 kV) adapted from our 18-beam multiple-beam klystron gun design. Both serpentine and folded-waveguide versions of the cascaded-TWT have been evaluated. Th...
Conference Paper
Comparisons between predictions of the NRL large signal codes CHRISTINE and TESLA-FW and measurements of small signal gain of NRL's G-Band serpentine waveguide TWT are presented. Results of a sensitivity study of the effects on gain of the circuit dispersion allow us to identify the most critical physical circuit dimensions for TWT design and to qu...
Conference Paper
Using a simple model we derive a universal condition for oscillation in a traveling wave tube for frequencies near a band edge, when the adjacent band gap is small. The condition is expressed graphically as a value for the maximum allowable (stable) small signal gain as a function of the size of the band gap. As an example of the application of the...
Conference Paper
We present an overview of the theoretical and experimental research activities at the U.S. Naval Research Laboratory in the area of millimeter-wave and sub-millimeter-wave vacuum electronics. Amplifier and related circuit development ranging in frequency from 30 GHz to 1.35 THz at power levels from multi-kilowatts to watts will be described along w...
Chapter
Vacuum electronic devices produce coherent electromagnetic radiation through the interaction of a beam of electrons with an electromagnetic structure. They are used in a wide variety of defense, scientific, and commercial applications ranging from radar, terrestrial and space-based communications, high energy physics, fusion, industrial processing,...
Conference Paper
We present large-signal, 3D simulations of vacuum electronic slow-wave amplifier operation using the GPU-accelerated FDTD-PIC simulation code, 'Neptune'. Neptune implements a self-consistent, charge-conserving, electromagnetic, particle-in-cell algorithm optimized for parallel execution in both multi-core CPU and GPU processors. Significant perform...
Conference Paper
Travelling Wave Tubes (TWTs) with slow-wave structures, based on a serpentine or folded waveguides, are promising devices for operation at sub-Terahertz and Terahertz frequency ranges. Development of such types of TWTs requires accurate and efficient computational tools suitable for their design, analysis and optimization. Recently we have develope...
Conference Paper
form only given. New models have been developed and implemented in the MICHELLE Finite-Element Electrostatic Particle-in-Cell code1 in support of modeling RF photocathodes and IOTs (inductive output tubes). In the case of photocatodes, low emittance, high current density sources are required to achieve the small beam size needed for high frequency...
Conference Paper
form only given. Reported on is the progress of the counter streaming, fully self-consistent model development in the MICHELLE Ebeam [1,2,3] code. This GPU-based software module performs high accuracy simulations of electron and ion beams including the effects of stochastic space charge.
Conference Paper
Spurious oscillations near edges of pass-bands due to periodicity (π and 2π) as well as edges due to manufacturing tolerance (3π/2) might develop in coupled cavity TWTs (CC-TWTs) and limit their performance. Modeling of spurious oscillations is challenging computational task since the beam-wave interaction occurs at several frequencies simultaneous...
Conference Paper
We have implemented a simple hybrid circuit model for folded waveguide slow wave structures [1] in the CHRISTINE-CC large signal simulation code [2]. The unit cell of the circuit model consists of an inductive shunt element that represents the interaction gap region, combined with a section of transmission line that represents the folded waveguide....
Conference Paper
The design of a Ka-band three-beam cascaded serpentine travelling-wave tube (TWT) amplifier is presented. Simulations predict that a peak power of 3.5 kW with saturated gain of 16 dB and an instantaneous bandwidth of 30% can be achieved in a circuit length of ≤ 4.5 cm driven by three 20 kV beams with 0.5-A each. A plan for a proof-of-principle expe...
Conference Paper
form only given. A W-band extended interaction klystron (EIK) driven by a 19.5-kV, 3.5-A sheet beam is being developed. Simulations using the 3-D particle-in-cell codes MAGIC and ICEPIC predict saturated output power levels of 8-10 kW with a saturated gain >;30 dB and small signal gain >;40 dB. A beamstick has been successfully fabricated and teste...
Article
A new computationally efficient 2-D model of the beam-wave interaction in coupled-cavity traveling-wave tubes (CC-TWTs) has been developed. The model provides self-consistent time-dependent solutions of Maxwell's equations together with a fully relativistic solution of the electron equations of motion. The model is based on different treatments of...
Article
We formulate and solve a set of equations that model the effects of reflections from an arbitrary number of circuit discontinuities in a traveling-wave tube (TWT) operating under small-signal conditions. Applying this model to a case in which the discontinuities represent a series of small random pitch variations due to fabrication errors in a heli...
Article
Full-text available
This paper presents analysis of the effects of nonperiodic perturbations in periodic RF structures. Small departures from periodicity change the phase shift experienced by a wave as it traverses an imperfect cell. Cell imperfections may be introduced intentionally or due to fabrication errors or material properties variations. The cumulative effect...
Article
We present a parallelization framework prototype for efficient physics-based computer simulation of hyperspectral time-dependent waveforms (i.e., wideband with a large number of frequency components) in nonlinear power amplifiers with memory. It relies on an adaptive algorithm for signal splitting and splicing in the time domain and uses a well-est...
Conference Paper
Experimental testing of electron beam formation, transport, and depressed collection is performed in a beamstick for a 670 GHz extended interaction klystron with a 25 kV, 100 mA nominal operating point. Beam transmissions of 77-86% are achieved through a 125 micron diameter by 1.7 cm long beam tunnel.
Conference Paper
Data from experimental testing of a beamstick designed and built for a 670 GHz extended interaction klystron are compared against 2D and 3D beam optics simulations using the MICHELLE code. A methodology is presented to establish the “as-built” geometry from these comparisons. Excellent agreement with experimental beam current and transmission data...
Conference Paper
A series of Ka-band Coupled-Cavity Traveling-Wave Tubes (CCTWTs) has been successfully developed, built, and tested at Communications and Power Industries (CPI) in collaboration with the Naval Research Laboratory (NRL) and SAIC. These devices represent a significant advance in the state-of-the-art of millimeter-wave CCTWTs, exploring the limits of...
Conference Paper
Coupled cavity TWT performance has been modeled using 1D (CHIRISTINE-CC) and 2D (TESLA-CC) approaches. The codes' predictions have been compared in detail for regimes for which application of both codes is valid. It was found that the level of code agreement depends primarily on beam current (beam perveance). The codes predict almost identical gain...
Conference Paper
A simple model for the dispersive properties of a folded waveguide slow wave structure is presented. The model, with a small number of fitting parameters, reproduces well the dispersion relation and Kino impedance of a structure as calculated using a computational electromagnetics code. The model allows for the inclusion of asymmetric beam tunnel f...
Conference Paper
The beam envelope equation [1] provides a simple model of the steady state dependence of the radius of an electron beam on axial location. Since the forces acting on a beam in any linear beam VE device depend on the beam radius, it is useful to have a model of the axial variation of the beam size in a beam-circuit interaction code. We describe an i...
Conference Paper
Simulation of counter streaming charged particle beams, where two beams are co-located in space while propagating in opposite directions, has many applications ranging from the lower current electron beam lithography regime to the higher current Free Electron Laser (FEL) regime. Modeling such counter streaming beams presents different computational...
Conference Paper
TESLA is a 2.5D large-signal code, which is suitable for the modeling of single-beam and multiple-beam amplifiers based on linear propagating beams. Initially developed for the modeling of conventional, single-beam klystrons mainly, later on the code was extended and successfully validated to allow modeling of multiple-beam klystrons (MBKs), extend...
Conference Paper
We present results of an electromagnetic cold-test of an all-copper, microfabricated 220 GHz serpentine waveguide amplifier circuit. Transmission/reflection measurements are used to determine the ohmic loss, pass band, and cutoff frequency. We observe the effects of fabrication accuracy, including circuit depth and beam tunnel alignment, on the mea...
Conference Paper
The 2.5D large-signal code TESLA-CC is a modification of the well-established klystron code TESLA to make it suitable for the 2D modeling of Coupled-Cavity Traveling-Wave Tubes (CCTWTs) by adopting the Curnow-circuit model for representation of the fields of an external coupled-cavity structure. We report the results of TESLA-CC modeling for an exp...
Conference Paper
A 50 watt, wideband serpentine amplifier is under development to demonstrate a novel beam tunnel fabrication technique capable of forming arbitrarily long beam tunnels of very small diameter using a single Ultraviolet Lithography (UV-LIGA) exposure step.
Conference Paper
A helix TWT having unprecedented power across the full K/Ka band (18-40 GHz) has been developed. This TWT has a minimum CW output power greater than 130 W over the full band and greater than 200 W for most of the band (19 to 38 GHz). This K/Ka band helix TWT development has leveraged the underlying technology from L-3 ETI's high-power millimeter-wa...
Conference Paper
The Multiple-Beam (MB) Inductive Output Tube (IOT) has been proposed for UHF applications requiring from 500 kW to 1 MW of average power. Our team of Scientists and Engineers are developing and validating a suite of computation tools for the design of these advanced devices. The cornerstone of this effort is the development of a circuit-based beam-...