As a part of the plan to deploy a wideband high-power module (HPM) to very high-throughput satellite (VHTS) network systems, Communications and Power Industries LLC (CPI) has been developing a ${V}$ -band high-power traveling-wave tube (TWT) amplifier. The power amplifier is designed with a staggered-vane TWT (SVTWT) circuit and a circular beam, operating at beam voltage ( ${E}_{k}{)} =18$ –20 kV and beam current ( ${I}_{k}{)} =400$ –500 mA with the perveance of $0.168 \mu \text{P}$ . Within the development program, three prototypes have been built and tested so far—the first two prototypes only include simple features in their circuit configuration, excluding servers and complex tuning elements. The signal amplification process in the novel beam–wave scheme was demonstrated with the first prototype, showing 35 dBm of output power ( ${P}_{\text {out}}{)}$ with 10–15 dB of small-signal gain and 4 GHz of 1-dB bandwidth (47.2–51.2 GHz). ${P}_{\text {out}} =57$ dBm (500 W) and 24 dB of small-signal gain (SSG) were demonstrated over 4.2 GHz (47.2–51.4 GHz) of 1-dB bandwidth with the second prototype. During the RF test, the tube operated at the continuous wave (CW) mode (100% of duty cycle) with extra external cooling fans. The third prototype is designed with more complex features, including servers, mode anode, and multistage depressed collector (MDC). Its test results showed ${P}_{\text {out}} =54$ dBm (250 W) and 24 dB of SSG over 5.2 GHz (47.2–52.4 GHz) of 1-dB bandwidth, running at CW mode with extra external cooling fans.

As a part of plan to deploy a wideband high-power module (HPM) to very high-throughput satellite (VHTS) network systems, CPI has been developing a V-band high-power TWT amplifier. The first two prototypes designed for 500 W and 250 W levels of saturated output power were fully tested, showing 24 dB gain and more than 5 GHz bandwidth with 50 - 100 % of duty factor. Currently, a 3 rd prototype is being developed with the plan to release its version compatible with market-demands. This paper will summarize their fabrication processes and test results.

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.

Having a proven beam system focused by a periodic permanent magnet structure, rf circuits to achieve 700Watts CW of power amplification at Ka-Band have been designed. These circuit designs have been further explored and correlated to TESLA-CC (US Naval Research Laboratory's newly developed code) simulation results and to measured data.

A family of 700-W Ka-band Coupled-Cavity Traveling-Wave Tubes (CCTWTs) has been successfully developed, built, and tested at Communications and Power Industries (CPI). These CCTWTs are capable of up to 700-W Continuous Wave (CW) output power with 2.0 GHz of instantaneous bandwidth. They were built with the intended use for the commercial satellite and military communication market. We discuss the design and successful demonstration of the family of CCTWTs, including the VTA-6428S2B prototype which achieved over 700-W (783-W maximum output power) with an overall efficiency reaching as high as 52%.

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 power, bandwidth, and stability. We discuss the design and successful demonstration of the series of CCTWT's, including the VTA-6430N1 prototype which achieved over 700-W (879-W maximum power) over a 5-GHz range in Ka-band.

A four-stage depressed collector is designed with MICHELLE using the optimization tool in ANALYST. The effect of slow or “true” secondary electrons (SSE), back-scattered primary electrons (BSE) and different geometries are studied in the modeling of multi-stage depressed collectors. Details of the design and optimization philosophy along with user settings in MICHELLE and ANALYST will be discussed. Results of a collector that was designed, built and tested at CPI, will be presented.

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 through a 0.4 × 5 mm beam tunnel over a distance of 20 mm in a uniform 8.5-kG field. The beamstick collector has been depressed to -9 kV with very little effect on the beam transport. The performance very well agrees with simulations. This beamstick will be the basis for a high-power (~10-kW) W-band extended-interaction-klystron amplifier that is currently under development.

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 gun having single-plane convergence of a factor of ~30, a permanent magnet solenoid, a 1.8-cm-long × 5 mm wide × 0.4 mm high beam tunnel, and an isolated collector. The engineering design was based closely upon MICHELLE and MAGIC-3D simulations of a W-band extended interaction klystron.

The Sheet Beam Klystron (SBK) is characterized by a large drift tube, which allows the use of high beam current at a low voltage, resulting in low beam current density, high efficiency and the possibility of PPM focusing. CPI has designed, manufactured and is currently testing an X-Band SBK capable of 5 MW peak, 20 kW average output power This paper discusses the general design, manufacturing and performance to date of CPI's X-Band SBK.

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 appears to be quite simple, the actual operation of the device is quite complex and difficult to analyze quantitatively. Consequently, we are investigating the physics of the beam-wave interaction of the IOT with the goal of achieving significantly higher power operation. The time-domain electrostatic PIC code MICHELLE, in conjunction with the Analyst® suite of electromagnetic codes, were used to model the cathode-grid-anode structure that comprise the input cavity. Our investigation has led to the discovery of a mechanism responsible for intra-bunch charge formation. Time-domain PIC results of this effect will be shown. We will also present simulation results of the large-signal beam wave interaction in the output cavity using the code TESLA. Examples of single beam and multiple-beam (MB) IOT designs will also be shown.

After successfully designed and manufactured 40 kW CW/85 kW peak 1.3 GHz inductive output tube (IOT) amplifiers, we have been working on pushing the power of IOT to a new level, 120 kW CW. The challenges are so significant that simple modifications to the lower power version IOT would not be adequate. A complete new design is necessary for increased power level and reliable performance. In this paper, we will describe the tasks conducted for the IOT amplifier design.

Multiple‐beam amplifiers (MBAs) represent a device technology with the potential to produce high‐power, efficient amplifiers with relatively wide bandwidths that are compact, low‐weight, low‐noise, and operate at reduced voltages relative to comparable single‐beam devices. To better understand the device physics and technical issues involved in the design, fabrication, and operation of these devices, the U.S. Naval Research Laboratory (NRL) has an on‐going program to develop high peak power (> 600 kW) multiple‐beam klystrons (MBKs) operating in S‐band (∼3.3 GHz).

We present initial experimental results from the successful operation of a 600-kW peak, fundamental-mode multiple-beam klystron (MBK). The eight-beam device operates at a cathode voltage of similar to 45 kV and a total beam current of similar to 32 A with an axial guiding magnetic field of 1.8-2.2 kG. In the absence of radio-frequency (RF) drive, the measured beam transmission is in excess of 99%; at a driven frequency of 3.25 GHz, the measured beam transmission at saturation is >= 97%, where the four-cavity circuit generates a peak power of similar to 600 kW with an electronic efficiency of 40%. The measured beam transport and RF performance are in excellent agreement with predictions made by the three-dimensional gun/collector code, MICHELLE, and the large-signal klystron code, TESLA. The accuracy of the design codes enabled the achievement of a working device in a single hardware design pass.

A 10 MW, 1.3 GHz multiple beam klystron (MBK) has been developed for the DESY X-FEL and International Linear Collider projects. The device uses six electron beams set off-axis on a large bolt circle which interact with a combination of higher-order-mode and conventional klystron cavities to efficiently produce high power RF. Extensive two and three dimensional simulations were used to design the device. Recent test results have validated the basic design concepts and procedure. Ten megawatts of peak and 150 kW of average power have been stably generated with 59% efficiency and 48 dB of gain.

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 circuit and is shown to be in excellent agreement with the three-dimensional particle-in-cell code, MAGIC 3D. Computational simulations indicate that the optimized design has very low beam interception, producing a peak RF power of 865 kW with a corresponding gain of 34.5 dB and an electronic efficiency of similar to60% at mid-band (3.27 GHz).

A high-efficiency, Multiple-Beam Klystron (MBK), designated the VKL-8301, is being manufactured for the DESY Tera Electron volt Superconducting Linear Accelerator (TESLA) in Hamburg, Germany. There are a number of excellent reasons for using an MBK for this application. The primary reasons are reduced size and lower operating voltage with respect to the conventional, single beam counterparts. Once this decision has been made, the class of MBK must now be selected. MBKs can be divided into two categories: Fundamental Mode (FM) and Higher-order Mode (HM) devices, distinguished by the interaction mode of the cavity resonators. Each class has inherent advantages and disadvantages dependent upon end-user requirements. For the 10 MW, 1.3 GHz TESLA application the HM-MBK is the clear choice. The primary factor influencing this choice was operational life, since the accelerator will require approximately 600 MBKs. The advantage of the HM approach is low cathode loading. Our cathode loading design goal of 2 A/cm/sup 2/ or less has been achieved. For this application the HM-MBK cathode loading is a factor of four lower than competing FM-MBK designs and a factor of three lower than the SLAC 5045 design. The VKL-8301 will use six off-axis electron beams interacting with a combination of TM/sub 010/ and hybrid TM/sub 020/ cavities. These six beams are equally spaced on a diameter of approximately 25 centimeters. Because of the large beam-to-beam separation, individual high-area convergence guns can be utilized versus the single multi-emission-site gun used in FM-MBK's. This solution requires a sophisticated focusing system that is relatively difficult to realize, compounded by our use of confined-flow focusing. Newly developed, state-of-the-art three- dimensional electromagnetics codes have been used to design the novel electron-beam-focusing system and microwave cavity geometry. Modeling and simulation results will be presented, hardware will be shown, and a description of the FM- versus HM-MBK selection process will be discussed.

: Multiple-beam klystrons (MBKs) are a class of vacuum electronic amplifiers, in which the kinetic energy of axially streaming electron beams is converted to electromagnetic energy through the interaction of the beams with a series of resonant microwave cavities. With their potential to efficiently produce coherent, broadband, high-power microwave radiation in a compact package, MBKs are a promising device technology to provide the low-noise transmitter performance required by shipboard radar systems to operate in high-clutter environments (e.g., littoral zones) and to keep pace with evolving antiship cruise missile (ASCM) and tactical ballistic missile (TBM) threats. Nondefense applications of this technology include civilian radar, communications, and accelerators for high-energy physics. As the name implies, MBKs make use of multiple electron beamlets, each of which propagates in a separate, parallel beam tunnel, but interact with electric fields in common regions such as cavity gaps. In this manner, the perveance of the individual beamlets can be low, facilitating stable-beam propagation and efficient beam-wave interaction without the adverse space-charge effects that could debunch the beam, while the total beam current can be high, facilitating high-power and broad-bandwidth operation. In addition, MBKs possess a number of advantages over conventional single-beam klystrons of comparable power, including reduced operating voltages (typically 50% to 80%) which leads to shorter circuit lengths (typically 30% to 60%) and significantly lower weight. Furthermore, MBKs possess the low phase noise performance that is desirable for radar and communication applications.