Gyrodevice oscillators and amplifiers (or gyro-oscillators and gyro-amplifiers) are being utilized in a variety of applications where high power levels are required at millimeter-wave frequencies. Gyro-oscillators, developed primarily for magnetic fusion research applications, have achieved power levels near 1 MW for pulse durations in excess of 1 s at frequencies above 100 GHz. Continued work on these devices should enable them to achieve continuous-wave operation at multimegawatt power levels at frequencies in the 100-GHz to 200-GHz range, thereby meeting the requirements of planned magnetic fusion experiments. The development of gyro-oscillators for fusion experiments has led to the utilization of the devices in several industrial applications, such as ceramic sintering and metal joining. Activities in this area involve adapting the oscillators to the industrial environment where reliability, efficiency, and ease of operation are paramount. Gyro-amplifiers are being developed for applications requiring phase coherence and instantaneous bandwidth, such as in linear accelerators and millimeter-wave radar. Impressive results from X-band to W-band already suggest the promise of these devices. Potential new applications and novel gyrodevice design approaches continue to attract the attention of researchers around the world.

Characteristics and applications of fast-wave gyrodevices

A novel, linearly polarized TEn,1mode coupler has been designed and demonstrated experimentally. 997percnt; of the fundamental TE1,0 mode in a rectangular waveguide is converted to the TE3,1mode in a cylindrical waveguide in this coupler. The field pattern of the linearly polarized TE3,1 mode has been verified using a RF probe for an X-band coupler. The coupling and return losses in the X-band and Ka-band couplers measured are in good agreement with theoretical predictions. For the Ka-band coupler, — 25 dB of return loss and 7% 3dB bandwidth has been measured.

Linearly polarized TEn,l coupler

Publisher Summary
The peniotron is similar to a gyrotron in several ways. Some of these ways have are mentioned in the chapter. However, peniotrons are different from gyrotrons in the mechanism for which the energy conversion takes place. In the peniotron, the electron beam can be a large envelope of orbiting electrons as in the gyrotron. Such a device is called a gyropeniotron and it is capable of power levels comparable to those of gyrotrons and has applications similar to those of gyrotrons. However, in many cases the electron beam is simply a hollow, axis-encircling (rotating) beam that is one beamlet of the gyrotron beam. The major peniotron types are illustrated in the chapter. The chapter explains the traditional peniotron, its principle of operation, performance, and design. The chapter also offers a discussion on nontraditional peniotrons that are proposed, theoretically analyzed, and developed. In any of these devices, the principle of peniotron amplification resides with the alternating acceleration–deceleration of the electrons during any cyclotron period and with increasing electric field strength with increasing radius of the orbiting electrons.

Chapter 5 – The Peniotron

Advances in electron gun and circuit technology have made it possible to design compact high power (multi-kW wave, tens-kW peak) gyro-amplifiers operating at millimeter wave frequencies employing conventional magnet technology. The devices being developed have the potential to increase the power available to the millimeter wave system designer by over an order of magnitude in a configuration compatible with system deployment. To demonstrate the viability of the technical approach, a focused two-phase, five-year ARPA/Tri-Service program has been established under the Vacuum Electronics Initiative to develop a high performance millimeter wave amplifier operating at 95 GHz. The program progress to date is reviewed, followed by a discussion of the millimeter wave gyro-peniotron amplifier experiment underway at the Naval Research Laboratory (NRL). >

High power harmonic gyro-amplifiers for millimeter-wave radar

Summary form only given. Litton has been investigating a 4th harmonic, 4-cavity amplifier based on an axis-encircling electron beam from a new type of electron gun, the advanced center post gun. The current amplifier design utilizes a coaxial magnetron type output cavity. In this cavity, vanes extend nearly down to the electron beam's outside diameter. The RF power is coupled through slots at the end of the gaps between the vanes into a coaxial cavity whose inner conductor is the outer conductor of the magnetron cavity. The majority of the RF stored energy in the system is in the coaxial cavity, so that the resonant frequency of the system may be adjusted by varying the resonance of the larger coaxial cavity. The output power is coupled into a waveguide through a hole in the outside diameter of the coaxial cavity. As a first RF test, an oscillator based on this type of cavity is being designed. A small signal code has been developed to study the oscillation threshold sensitivity to cavity dimensions and electron beam parameters.

Design and construction of a 95 GHz, 4th harmonic oscillator experiment

A 95 GHz, fourth harmonic gyro oscillator is being investigated at Litton. The design centers around a new type of electron gun, the advanced centerpost (ACP) gun. This gun produces an axis-encircling beam which interacts with the RF fields in an 8-vaned magnetron cavity. Four of the vanes have slots in their outside diameters that couple into a coaxial cavity. Radiation is extracted from the coaxial cavity by a fundamental W-band waveguide. >

Design and construction of a 95 GHz, 4/sup th/ harmonic oscillator experiment

The ARPA High Power Millimeter Wave Amplifier Program harmonic gyroklystron experiment required a hollow axis encircling electron beam. Scheitrum's (ACP) advanced centerpost gun was used in the beamstick experiment. 88% beam transmission was realized through a 64 mil drift tube for a 25 kV, 1.4 amp beam in a 8.5 kGauss solenoid. >

Beamstick for a 95 GHz gyroklystron

Summary form only given. This paper describes a new advanced centerpost (ACP) gun for the Litton 95 GHz harmonic gyroklystron which provides roughly four times higher beam current than that available from the original gun. The magnetic focussing structure has been carefully matched to the beam in order to provide a very high quality, low velocity spread, axis-encircling beam. The level of magnetic field in the rf interaction region is consistent with fourth harmonic operation of the device (approximately 8500 gauss) which allows a conventional solenoid to be used. At an operating voltage of 30 kilovolts and a beam current of 6.4 amps, peak power in the beam from the new gun is 192 kilowatts. At this voltage and current, the perveance of the gun is 1.23 micropervs. Procedures, computer codes, and methodology used to design the gun and magnetic focussing system will be discussed in detail. Two key codes used in the design process were DEMEOS and POISSON. DEMEOS is a finite-element based variable triangular mesh electron beam dynamics code and POISSON is a variable mesh magnetic field code. Results from POISSON can be imported into DEMEOS. The first step was to develop a low spherical aberration gun in an x-y half plane (using DEMEOS) having the correct current density and as long a beam throw (cathode to beam waist) as possible. Next, code VAXSCALE was modified to reflect, rotate and shift DEMEOS data for solution in the actual problem space (the z-r plane). Both nonthermal and thermal beam models were used in the simulations.

Design of a high perveance ACP gun for the Litton 95 GHz harmonic gyroklystron

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Design and construction of a 95 GHz, 4th harmonic oscillator experiment

Design and construction of a 95 GHz, 4/sup th/ harmonic oscillator experiment

Beamstick for a 95 GHz gyroklystron

Design of a high perveance ACP gun for the Litton 95 GHz harmonic gyroklystron