Mark Frederick Kirshner

A 100 Watt W-Band MPM TWT

L-3 EDD has developed a W-Band TWT with 100 W RF power over 4 GHz of bandwidth around 94 GHz suitable for MPM integration. The TWT employs an aperture grid modulated electron gun with mod-anode current control, a serpentine waveguide interaction circuit, and a single-stage depressed collector. Two TWTs have been built and tested to over 100 W pulsed output power. The first unit has been operated at high duty, producing 65 W CW output power and 75 W average pulsed power with reduced beam current. The TWT is designed for ease of manufacture, and is suitable for MPM integration, relying on conduction cooling and capable of operation to an altitude of 50k feet.

Ab initio investigation of the surface properties of dispenser B-type and scandate thermionic emission cathodes

Scandate cathodes (BaxScyOz on W) are important thermionic electron emission materials whose emission mechanism remains unclear. Ab initio modeling is used to investigate the surface properties of both scandate and traditional B-type (Ba–O on W) cathodes. We demonstrate that the Ba–O dipole surface structure believed to be present in active B-type cathodes is not thermodynamically stable, suggesting that a nonequilibrium steady state dominates the active cathode’s surface structure. We identify a stable, low work function BaxScyOz surface structure, which may be responsible for some scandate cathode properties and demonstrate that multicomponent surface coatings can lower cathode work functions.Scandate cathodes (BaxScyOz on W) are important thermionic electron emission materials whose emission mechanism remains unclear. Ab initio modeling is used to investigate the surface properties of both scandate and traditional B-type (Ba–O on W) cathodes. We demonstrate that the Ba–O dipole surface structure believed to be present in active B-type cathodes is not thermodynamically stable, suggesting that a nonequilibrium steady state dominates the active cathode’s surface structure. We identify a stable, low work function BaxScyOz surface structure, which may be responsible for some scandate cathode properties and demonstrate that multicomponent surface coatings can lower cathode work functions.

Input Circuit for a Wideband IOT

Emission gated microwave amplifiers, such as the inductive output tube (IOT), use density modulation to establish an AC current on the electron beam directly at the cathode surface. These amplifiers are compact and highly efficient, even in the linear regime. L-3 Electron Devices Division is developing a wide instantaneous bandwidth IOT (WBIOT) which will provide output power levels suitable for UHF radar applications with a 1 dB bandwidth in excess of ten percent. In this paper we describe the input circuit of the WBIOT.

High power X-band klystron

L-3 Communications Electron Devices Division (EDD) is developing a 9.3 GHz, 5 MW peak, 20 kW average power klystron suitable for use in linear accelerator and radar applications. Generating RF power of this magnitude within the confines of a relatively small sized X-band RF circuit is a significant challenge. A discussion of the design methodology and simulation tools used to accomplish this task will be presented, as will hot test data from the first prototype.

Development of a wideband inductive output tube

Inductive output tubes (IOTs) employ emission gating to modulate the electron beam directly at the cathode surface. The high efficiency of these compact devices has motivated their use in UHF television broadcast and particle accelerators. The instantaneous bandwidth of broadcast IOTs is two percent (6 MHz). Many radar and communications applications - in which the linearity and efficiency of the IOT are highly desirable - require a significantly larger bandwidth. L-3 Electron Devices Division (EDD) is therefore developing a wideband IOT (WBIOT) which will provide output power levels suitable for UHF radar with a 1 dB bandwidth greater than ten percent.

A 100 Watt W-Band MPM

L-3 EDD has developed a pulsed mode WBand microwave power module (MPM) providing 100W RF power over 92 to 96 GHz. The MPM includes a serpentine waveguide PPM-focused TWT and a modular electronic power conditioner (EPC). A breadboard power supply was previously built and successfully tested with a W-Band TWT. The final power conditioner design is completing development for packaging with a TWT as an MPM.

The wideband inductive output tube

L-3 Electron Devices Division (EDD) is developing a wideband IOT (WBIOT) with a 1 dB bandwidth greater than ten percent. High efficiency, good linearity, and compact size are provided by emission gated modulation of the electron beam directly at the cathode surface. Through use of a high impedance input circuit and an extended interaction output circuit, the instantaneous bandwidth of existing IOTs is increased by a factor of five, making the WBIOT suitable for use in a broad range of radar and communications applications.

IOT Development at Electron Devices

The inductive output tube, or IOT, has long been established as the amplifier of choice for UHF television broadcast. IOTs are also employed in an increasing number of accelerator applications. For example, L-3 has recently provided several IOTs, optimized for accelerator use, to the Thomas Jefferson National Accelerator Facility. Many of these accelerator projects have power and frequency requirements beyond the conventional IOT parameter regime. In particular, there have been a number of accelerator designs proposed utilizing the superconducting 1.3 GHz cavity developed at DESY

An 805 MHz high-power klystron

Describes a 805 MHz, 2.75 MW peak power klystron in support of the Spallation Neutron Source currently under construction in Oak Ridge, Tennessee. The klystron was tested at a pulse length of 1.67 msec and a repetition rate of 60 Hz (10% duty) producing an average power of 275 kW. The electron beam was produced by an anode controlled electron gun operating with a nominal cathode voltage of 107 kV and a current of 43 A. The amplifier section consisted of a total of 6 cavities, including one cavity operating at the second harmonic. Each of the cavities, with the exception of the output cavity, incorporated tuners, allowing their resonant frequencies to be optimized.

High efficiency E-band MPM for communications applications

L-3 Electron Devices Division (EDD) has developed a compact CW E-band microwave power module (MPM) to cover the 81 to 86 GHz band for communications applications. The power amplifier in the MPM is a periodic permanent magnet focused serpentine waveguide TWT, capable of over 200 W and 50% efficiency. In combination with a predistortion linearizer from LTI, the MPM will provide over 50 W linear power, making it suitable for high data rate communications.