John Pasour

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

We describe the design, development, and initial testing of a very compact, multiple-beam folded-waveguide traveling wave tube (TWT) operating in Ka -band at $\sim$ 6 kV. A proof-of-principle four-beam, $\sim$ 100 mA/beam device has been fabricated and tested, and a 16-beam version of the device has been designed and is predicted to produce a...

Multiple beam traveling wave tubes (MB-TWTs) are attractive novel devices with enhanced power-bandwidth characteristics1. However, they are more vulnerable to spurious oscillations than single beam TWTs. Therefore, design codes for MB-TWTs should be capable of accurate prediction of MB-TWT operation in steady-state regime as well as prediction of s...

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.

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,...

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...

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...

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...

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...

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...

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...

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...

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...

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...

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...

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...

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....

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...

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...

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...

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...

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...

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...

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...

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...

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...

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-...

This paper presents analysis of the electron beam propagation in transverse radial electrostatic field. It is shown that combination of the inward and outward forces acting on the beam electrons can create favorable conditions for stable transport of equilibrium high current electron beam without need for the confining magnetic field. Physical mech...

There is a significant level of effort by SAIC and BWR, funded by ONR & JTO, to enhance the three dimensional (3D) finite-element (FE) electrostatic time-domain (ESTD) particle-in-cell (PIC) code MICHELLE to provide modeling and simulation of the interaction of electron emission sources in the presence of electromagnetic cavity fields. These enhanc...

Extensive numerical analysis has demonstrated that a terahertz (H-band) sheet beam traveling-wave tube (TWT) amplifier circuit, composed of a staggered double grating array waveguide, has very broad bandwidth (~30%) of the fundamental passband (TE mode) with a 7:1 aspect ratio sheet beam without excitation of n = 1 space harmonic backward-wave mode...

The design and development of a high-perveance sheet electron beam is reported. A beamstick that employs a novel sheet beam gun together with a permanent magnet solenoid has been fabricated and tested up to 4.8 A at 22 kV. At the nominal operating point of 19.5 kV and 3.3 A, this beamstick has transported 98.5% of the emitted electron current throu...

The second device type is a low-voltage multiple-beam ex­ tended-interacti on klystron (MB-EIK). Designs are currently being explored for both Ku-and Ka-bands with operation voltages in the range of 2.5 -4.5 kV using permanent magnet focusing. We will present simulations using the NRLISAIC code TESLA that indicate that an output power of greater th...

A W-band extended interaction klystron (ElK) driven by a 19.5-kV, 3.5-A sheet beam is being developed. Simulations using the 3-D particle-in-cell codes MAGICl and ICEPIC 2 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 tested, transporting...

Extensive numerical analysis has resulted in the conclusion that the THz (H-band) sheet beam traveling wave tube (TWT) amplifier circuit, comprised of a staggered double grating array waveguide, has the very broad bandwidth (~ 30 %) of the fundamental passband (TE-mode) with a 7 : 1 aspect ratio sheet beam without excitation of n = 1 space harmonic...

Key performance characteristics that guide the selection of an amplifier for various applications are gain, power, linearity, and efficiency. In this paper, these pa- rameters are contrasted for two amplifier configurations: a single-beam amplifier with stages placed in series vs. a multi-beam amplifier with cascading stages. Based on MAGIC-3D simu...

A W-band sheet-beam extended interaction klystron (EIK) has been fabricated and tested. The EIK integrates a 3-cavity circuit with our previously demonstrated 20-kV, 3.5-A beamstick. The EIK has produced a saturated peak output power of over 7.5 kW and a small-signal gain of almost 40 dB, in very good agreement with our simulations.

Free Electron Lasers (FELs) make significant demands on the photocathode / drive laser used to generate electron bunches, but no photocathode source simultaneously satisfies needed demands of lifetime, quantum efficiency, and response. High gain mm-wave (and beyond) amplifiers make analogous demands. A diamond current amplifier may enable progress...

To develop compact, high-power, millimeter wave vacuum electronic amplifiers, it is important to minimize the operating voltage while increasing the operating current. Sheet electron beams are attractive for such amplifiers because if the current density can be maintained at round-beam levels, much higher beam current can be propagated in a sheet b...

A beamstick for demonstration of a 25:1 aspect ratio, 750 A/cm² current density sheet beam for DARPA's HiFIVE project will be described.

The stable transport of high-perveance, low-voltage sheet electron beams is a key requirement for the successful development of compact, high-power sheet beam amplifiers. We describe a beam stick to demonstrate the transport of such a beam (19.5 kV, 3.5 A) in a solenoidal magnetic field of about 8.5 kG. The beam stick consists of a novel sheet beam...

A sheet-beam Extended Interaction Klystron (EIK) is an attractive MMW amplifier because of its enhanced power capability, compactness, and relatively high gain per unit length. However, an intrinsic problem with a sheet beam amplifier is its susceptibility to multimoding, which results because the width of the device is typically larger than a wave...

A new concept for a compact high-gain multiple-beam TWT amplifier is introduced. To illustrate the concept, we present the design of a three-beam 220-GHz serpentine TWT amplifier. MAGIC-3D particle-in-cell code simulation results predict that the device should be capable of a peak power of 73 W and saturated gain of 42 dB over an instantaneous band...

The inductive output tube (IOT) is the preferred technology for a number of applications requiring tens to hundreds of kilowatts of RF power at UHF and L-band frequencies and has been proposed for applications requiring as much as a megawatt CW. Although conceptually simple, modeling and simulation of the physics of the electron beam formation regi...

A permanent magnet structure has been successfully designed and fabricated for the HiFIVE program. The design produces a peak field of 0.75 T within a gap length of 2.5 cm.

This paper describes the latest advances in code development targeted to model the beam wave interaction of inductive output tubes. At the core of this effort is the modeling and simulation of the input cavity, which requires the utilization of finite-element (FE) electromagnetic (EM), magnetostatic and electrostatic time-domain (ESTD) PIC codes. K...

Vacuum electronics (VE) amplifiers and oscillators are used for military and commercial applications that require high power at high frequency and also used in scientific research areas such as high-energy particle accelerators and plasma heating for controlled thermonuclear fusion. The types of amplifiers like space-based traveling-wave tube ampli...

The vacuum electronics branch of the US Naval Research Laboratory (NRL) is actively engaged in research and development of key technologies for high-power MMW to upper-MMW amplifiers. This work includes the development and application of physics-based modeling and simulation tools, the design and development of high-perveance sheet electron beams a...

In this paper, the transport of intense sheet electron beams in a uniform solenoidal magnetic field in high-power vacuum electronic devices is theoretically examined with the 3-D beam optics code MICHELLE. It is shown that a solenoidal magnetic field can be an effective transport mechanism for sheet electron beams, provided the beam tunnel is match...

Summary form only given: To evaluate the feasibility of operating a 94-GHz, 30-100 kW gyrotron with a permanent magnet, we have explored various 4th harmonic configurations, including two- and three-cavity multipliers and single-cavity oscillators. Such devices require a magnetic field of ~9.5 kG, a level that is achievable with readily available p...

Low-voltage, high-perveance sheet beams are attractive for compact, high-power millimeter wave (MMW) amplifiers, because significantly higher beam current and RF power can be accommodated in the larger cross sectional area (as compared to conventional pencil beam devices). Furthermore, solenoidal focusing offers important advantages over the more p...

The extended interaction klystron (EIK) is a compact amplifier that is well-suited to millimeter-wave and submillimeter-wave operation, having achieved state-of-the-art performance of 9 W CW at 218 GHz with a tightly focused 12-kV round beam. By utilizing an EIK circuit in a sheet-beam topology, our goal is to produce more than an order of magnitud...

The preliminary design of a four-cavity G-band sheet-beam Extended-Interaction Klystron (EIK) Circuit is presented. The circuit design has been performed with the self-consistent particle-in-cell (PIC) code MAGIC-3D. All cavities operate in the 2-pi mode. The circuit is powered by a 520 mA, 16.5 kV sheet-electron beam. Output power of 453 W is achi...

The stable transport of high-perveance, low-voltage sheet electron beams is a key requirement for the successful development of compact, high-power sheet beam amplifiers. Here, we examine the transport of such beams in a solenoidal magnetic field and compare and contrast this transport with that produced by a periodic permanent magnet array. It is...

The accelerator community is making the transition to inductive output tube (IOT) technology for a number of high-power UHF and L-band applications as a result of their inherent benefits. Scientists, funded by the Office of Naval Research and Naval Research Laboratory, are investigating the physics of the beam-wave interaction of the IOT. The time-...

The Inductive Output Tube (IOT) is today the device-of-choice for terrestrial UHF broadcast applications due to the IOT's high efficiency with linearity and compact size. The accelerator community is also making the transition to IOT technology for a number of high-power UHF and L-band applications as a result of these benefits. Although the IOT ap...

In this paper an overview of theoretical studies of frequency-quadrupling gyrotrons (FQGs) will be given. This concept allows one to overcome the use of superconducting solenoids in gyrotrons operating at short wavelengths as well as to master the range of THz frequencies with available superconducting magnets.

The design and development of compact, slow-wave MMW amplifiers driven by low-voltage sheet beams will be discussed. A high-perveance sheet-beam gun has been designed to produce a 3.5-A, 19.5-kV beam having a cross section of 0.32 mm times 4 mm, suitable for driving a W-band amplifier at ~10 kW. A relatively simple sheet-beam circuit, an extended i...

This paper investigates solenoidal transport and show that it is not only feasible but preferred for certain types of devices. In particular, interest in low-voltage (

A design methodology for sheet-beam formation and solenoidal magnetic field transport is described, and a point design for a W-band amplifier gun and beam transport is presented. The gun topology flexibly permits adjustment of beam width to accommodate various interaction circuits while maintaining beam height. This topology has been employed in th...

Circuit designs for 91 GHz and 220-GHz sheet-beam extended-interaction klystrons (EIKs) are presented. The W-band circuit employs a relatively simple two-cavity configuration to demonstrate beam transport and high peak power RF generation, which will serve as the basis for future scaling to higher gain and frequencies. Uniform (solenoidal) magnetic...

Power modulators for compact, repetitive systems are continually faced with new requirements as the corresponding system objectives increase. Changes in pulse rate frequency or number of pulses significantly impact the design of the power conditioning system. In order to meet future power supply requirements, we have developed several high voltage...

We report the development of two-dimensional, time-domain simulation tools for modeling klystrons and inductive output tubes (IOTs). The present development is based upon the techniques developed for the GATOR (Freund et al., 2002) simulation code for coupled-cavity traveling wave tubes. This technique relies on the integration of equivalent circui...

We develop a methodology for the design of multiple-cavity klystron interaction circuits. We demonstrate our approach with the detailed design of a collector and a four-cavity circuit for a multiple-beam klystron (MBK) operating in the fundamental mode at a center frequency of 3.27 GHz (S-band). These elements are designed to be used with a 32-A 45...

This paper describes the detailed design of an eight-beam electron gun for use in S-band multiple-beam amplifiers operating in the fundamental mode. The gun operating voltage is 45 kV with a total beam current of 32 A, evenly divided among the beamlets. Each individual beam has a perveance of 0.42 mpervs making a total beam perveance of 3.35 mpervs...

This paper describes our efforts to develop a test environment that accurately approximates elements of several battery-driven compact Marx generator (CMG) systems currently in use, but which avoids the high-voltage and electromagnetic interference (EMI) issues of operating the actual CMG's. A triggering circuit, lumped capacitance, and load resist...

The design of an eight‐beam, four‐cavity multiple‐beam klystron (MBK) to be operated in S‐band is presented. The design methodologies for the gun, magnetic circuit, and RF interaction circuit are described, along with a brief description of the principal computational design tools. The large‐signal code, TESLA, was used to design the interaction ci...

A prototype, low‐repetition‐rate triaxial klystron amplifier (TKA) has been fabricated and tested. This device is powered by an annular electron beam (∼400 kV, 3.5 kA). The TKA operates at 9.3 GHz at power levels >100 MW and with a pulse duration of 750 nsec.

Efficiency enhancement in free-electron lasers (FELs) using rf beam acceleration in the wiggler is described. Since the beam tube is a waveguide, there are low and high frequency resonances. Injection of low frequency power can act as an inverse-FEL accelerator concurrently with high frequency power extraction. Simulation of a FEL using this techni...

Annular beam klystron amplifiers are being developed at L‐band and at X‐band. These devices are designed to operate at power levels of hundreds of MW to ∼1 GW, with pulse durations up to 800 nsec. The L‐band amplifier uses an 11‐cm‐diameter, 3‐mm‐thick annular beam (450 kV, 4.5 kA) inside an open beam tube with large‐gap cavities. The X‐band ampli...

A very attractive class of amplifiers that has the potential to provide high RF power at low beam voltage uses multiple electron beams rather than the single beam of conventional devices. These multiple beam amplifiers (MBAs) typically have individual beam channels with a common RF interaction region. A multiple beam klystron (MBK) illustrates the...

Summary form only given. Annular beam klystrons are well suited to high power operation. Significantly higher beam current can be transported than in conventional pencil beam klystrons (at the same beam voltage). Furthermore, we have designed cavity configurations that provide strong beam modulation and efficient energy extraction from the bunched...

We describe a high-power, annular beam klystron, the Triaxial Klystron, that promises high efficiency at GW power levels and frequencies up to X band. Higher frequency operation should be possible at reduced power levels. The device consists of a thin annular electron beam propagating in an annular drift region, with cavity structures located insid...

A large diameter thin annular intense relativistic electron beam was modulated at a frequency of 10 GHz. The electron beam propagated inside a narrow annular drift tube in which gaps feeding radial cavities were inserted. An external source injected microwave power of 180 kW into a single input cavity followed by a simple idler structure. A stable...

We describe a microwave source that utilizes a plasma to bunch the electron beam. The electron beam interacts with the plasma via the wakefield produced by the head of the beam. The resulting plasma oscillations bunch the beam at a frequency proportional to the plasma frequency. Thus the device can be tuned by varying the plasma density. The theory...

A nonperturbing probe that utilizes a focused ion beam has been developed to measure the position and profile of a tightly bunched charged particle beam (CPB). The ions are injected across the path of the CPB and are deflected by the electromagnetic field of the CPB. Deflected ions are detected by a gated microchannel plate detector and video camer...

This project investigated a novel microwave source that utilizes a plasma to bunch the electron beam. The electron beam interacts with the plasma via the wakefield produced by the head of the electron beam as it passes through the plasma. The resulting plasma oscillations bunch the beam at a frequency proportional to the plasma frequency. Thus, the...

A new mechanism for self‐modulation of an annular intense relativistic electron beam is being described. The frequency of modulation can be tuned 10% by magnetically compressing the diameter of the electron beam. © 1996 American Institute of Physics.

We describe a non-perturbing diagnostic to measure the position and profile of tightly bunched ({mu}m-sized) beams. The probe consists of a finely-focused low-energy ({approx_lt}30 keV) ion beam that is injected across the path of the beam to be measured. The deflections of the ions are measured with a gated microchannel plate (MCP) detector and re...

THOR is a 3-MeV, 2-kA, 1-µsec, Marx-based pulse generator. We are developing a 94-GHz PEL that is driven by the THOR electron beam. The PEL uses a 2.5-m-long, 10-cm-period helical wiggler. The PEL is initially being configured as an oscillator, with simple annular mirrors defining the cavity. The high power and long pulse duration of the THOR beam...

Infrared sensors are being incorporated in more systems and are often placed close to radar systems. The IR sensor is thus subjected to various microwave levels from the sidelobes or reflections of the radar pulses. In this paper we address the effect of microwaves on the performance of mercury-cadmium-telluride longwave photodiodes. We examine the...

A nonperturbing diagnostic tool which is capable of precisely measuring the position and charge distribution of charged‐particle beams, including those from rf accelerators, is described. The diagnostic uses as a probe a low‐energy (1–20 keV), μA‐level electron beam, which is injected across the path of the primary beam to be diagnosed. The probe e...

The authors describe the fundamental principles of the CIK and summarize the results of an experimental study of a proof-of-principle (POP) version of the device. the CIK is a microwave amplifier which utilizes circular orbit effects to strongly bunch electrons. The CIK has several important features which make it an attractive source, including hi...

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A series of experiments is underway to utilize the virtual-cathode-driven oscillator as a source of high-power microwaves on Aurora. The most recent experiment launched 270 J per pulse to resistive terminations through eight radial waveguides, with the frequency in a band around 750 MHz. The highest power, ~10 GW in a short burst, was obtained with...

The AAI High Power Microwave Source Development Program (HPM) has been actively investigating the design of HPM test systems using relativistic magnetrons with a repetition rate capability. The design and test of a gigawatt-level, S - to C -band, 10-Hz, mobile relativistic magnetron HPM system have been carried out. Mode competition, output-couplin...

A microwave calorimeter is disclosed for substantially measuring the total microwave energy in an applied microwave pulse. The microwave calorimeter includes: a housing having a highly reflective interior surface, a microwave device disposed in the housing for substantially absorbing microwave energy transmitted into the housing and for producing a...

The CIK is a microwave source which relies on the negative mass instability for electron bunching, as opposed to the linear-drift ballistic bunching of conventional klystrons. A proof-of-principle (POP) CIK is being tested to verify the predictions of analyses, which indicate that the CIK is feasible in the 2-10-GHz region at megawatt to gigawatt p...

The incorporation of several efficiency-enhancing features, the successful integration of high-gain amplifiers and oscillators, and the design of more compact and more practical devices, have recently been witnessed in the development of long-wavelength, high current MeV accelerator-driven FELs. Attention is presently given to the design difference...

The Aurora electron-beam generator driving a reflex diode has produced the largest single microwave pulse measured in the laboratory to date (early 1988). In this experiment up to 374 J per pulse is extracted from the device into two radial waveguides. The maximum peak power is 22 GW obtained in a single narrow spike; the peak average power is 9 GW...