Experimental Study of Microwave Pulse Compression Using a Five-Fold Helically Corrugated Waveguide

2017 IEEE 21st International Conference on Pulsed Power (PPC)

et al. 2017

Backward Wave Oscillators (BWO's) utilizing moderately relativistic (~550kV), high-current (~10 kA) electron beams are capable of producing hundreds of MWs of pulsed radiation in the centimeter wavelength range. Such relativistic BWOs (RBWOs) allow for broadband, smooth, frequency-tuning via adjustment of the accelerating potential; making them an attractive source for use in frequency-swept pulse compression.This paper presents results of a 2.86m long 5-fold helically corrugated, dispersive pulse compressor where a maximum power compression ratio of 25 was achieved by compressing an input microwave pulse of 80 ns duration swept from 9.65 GHz to 9.05 GHz into a 1.6ns Gaussianenvelope pulse. For an average input power of 5.8 kW generated by a conventional traveling wave tube amplifier, a peak pulse output power of 145 kW was measured corresponding to an energy efficiency of 66%.An X-band relativistic BWO, designed to drive a 0.97m long 5-fold compressor, was built and tested using the accelerating potential generated by a SINUS-6 highcurrent accelerator. The experimental RBWO operated close to the predicted power of 700MW with its oscillation frequency varied from 10 to 9.6GHz via the falling edge of the voltage pulse. It was demonstrated that the ~15ns duration frequency-swept part of the RBWO pulse was effectively compressed resulting in a 4.5-fold peak power increase with a maximum power of 3.2 GW generated. The potential for a 5-fold helical waveguide to compress longer duration pulses generated by a RBWO is discussed.

Section: A Experimental Results 5-fold Compressor (286m Long)mentioning

confidence: 97%

Periodic GW level microwave pulses in X-band from a combination of a relativistic backward wave oscillator and a helical waveguide compressor

MacInnes

Bratman

2017 IEEE 21st International Conference on Pulsed Power (PPC)

et al. 2017

“…It has interesting features as it can couple two operating modes in the circular waveguide to generate new eigenmodes. It has attracted considerable interest and found its applications in gyrotron backward wave oscillators (gyro-BWOs) [15,16], gyrotron traveling wave amplifiers (gyro-TWAs) [17][18][19], mode converters [20,21], microwave pulse compressors [22,23], and as a microwave undulator [11]. The inner surface of an HCW can be expressed in cylindrical coordinates as ( , ) = 0 + 1 ( + 2 / ) (5) where R 0 is the mean radius of the circular waveguide, R 1 is the corrugation depth, m B is the fold number, and d is the axial period of the corrugation.…”

Section: Hcw As Microwave Undulatormentioning

confidence: 99%

Microwave Undulator Using a Helically Corrugated Waveguide

IEEE Trans. Electron Devices

Clarke

et al. 2018

Self Cite

Microwave undulators (MU) can be an alternative to the permanent magnet undulators in a free electron laser (FEL). MUs normally employ a cavity-type structure that supports the standing wave to boost the electromagnetic field strength. In this paper, a waveguide-type MU based on a helically corrugated waveguide (HCW) that supports a traveling wave is studied. The use of the HCW allows partial conversion of a traveling wave mode into a backward traveling wave mode, hence increasing the effective interaction length. When operating with a TE11 mode at 30.3 GHz, the MU was predicted to realize a field strength of ~0.3 T and an undulator period of 4.95 mm when driven by 1 GW of microwave power.Index Terms-microwave undulator, free electron laser, helically corrugated waveguide, traveling wave mode.

“…When the interaction region has a helical corrugation on the inner surface there exists an "ideal" eigenwave giving many benefits that can be exploited in novel gyro-devices and in pulse compression [4]. For the gyro-devices the eigenwave has an almost constant value of group velocity over a wide frequency band in the region of small axial wave numbers [5].…”

Section: Introductionmentioning

confidence: 99%

High pulse repetition frequency operation of a W-band Gyro-TWA based on a cusp electron beam source

Donaldson

2016 41st International Conference on Infrared, Millimeter, and Terahertz Waves (IRMMW-THz)

et al. 2016

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