L.J. Dressman

Efficient Ka-band second-harmonic slotted peniotron

A harmonic peniotron has been designed for high efficiency and relative immunity to mode competition from gyrotron interactions. The device employs a 70-kV, 3.5-A, axis-encircling electron beam. To ensure stability from competing gyrotron interactions, the peniotron will operates in the lowest-order mode of a slotted four-vane circuit, the /spl pi//2-mode. The cavity is strongly diffraction coupled for a high circuit efficiency. The 33-GHz, slotted second-harmonic peniotron is predicted to yield 125 kW with an electron efficiency of 58% and a device efficiency of 52%. The device is being constructed at the University of California at Davis and is driven by a recently developed Northrop Grumman (Rolling Meadows, IL) cusp electron gun.

34 GHz Second-Harmonic Peniotron Experiment

Summary form only given. The peniotron has previously demonstrated very high (up to 75%) conversion efficiencies (T. Ishihara et al., 1999). However, high output powers with high device efficiency at mm-wave frequencies have not been reported. The UC Davis peniotron is designed to demonstrate high device efficiency at 100 kW power levels. The device operates in the second cyclotron harmonic at 34 GHz as a first step toward higher harmonics and frequencies. Design parameters for the device have been previously reported (D.B. McDermott et al., 2000) and large-signal codes predict output power and device efficiency of 125 kW and 47% respectively. The device utilizes a second-harmonic interaction with the fundamental mode in a four-vane slotted (magnetron-like) cavity. The interaction B-field is 6.5 kG which is achieved with conventional coils. Previously, the magnet was tested and its performance verified (L.J., Dressman et al., 2006). An adjustable pole piece allows the interaction B-field to be tapered. Key to the device is the axis-encircling electron beam produced by a Northrop Grumman cusp electron gun (D.A. Gallagher, 2000). The original design called for a 70 kV, 3.5 A beam. Output power is extracted from four ports which directly couple to each of the cavity slots. Initial testing has produced output power at 34 GHz with peak power levels in the range of a few kilowatts while operating at a reduced beam voltage of approximately 40 kV. Future efforts will concentrate on operation at full power and optimization of the magnetic fields.

Design and test of a 34 GHz harmonic peniotron

A 34 GHz peniotron, designed for high device efficiency and power output has been constructed at UC Davis. The device is designed for second-harmonic interaction with the axis-encircling beam produced by a Northrop Grumman cusp gun and is predicted to produce 125 kW peak output power. Magnetics have been recently redesigned, built and tested. Recent efforts have concentrated on final assembly of the device and improvement of the modulator.

Highly efficient 34 GHz peniotron

While high conversion efficiency has been demonstrated in peniotrons, practical application of the device requires that power be efficiently extracted from the cavity. The UCD peniotron is designed to achieve high overall device efficiency and power output (130 kW peak) by employing an over-coupled cavity driven by a Northrop Grumman Cusp gun. Stability is insured through the use of a fundamental-mode interaction with the second cyclotron harmonic of the axis-encircling electron beam.

Highly efficient Ka-band second-harmonic slotted peniotron

A harmonic peniotron has been designed for high efficiency and relative immunity to mode competition from gyrotron interactions. The device employs a 70 kV, 3.5 A, axis-encircling electron beam. To ensure stability from competing gyrotron interactions, the peniotron will operate in the lowest order mode of a slotted four-vane circuit, the /spl pi//2 mode. The 33 GHz, slotted second-harmonic peniotron is predicted to yield 125 kW with an electron efficiency of 58% and a device efficiency of 52%. The device is being constructed at UCD and will be driven by a recently developed Northrop Grumman Cusp electron gun.

Analysis of a 34 GHz peniotron oscillator

Preliminary results from the UC Davis peniotron experiment have been previously reported. The device operated, as designed, in the second cyclotron harmonic at the expected frequency of 34 GHz in the fundamental cavity mode. However, the device produced maximum output power at lower than expected voltage. Furthermore, a competing mode was present at the lower end of the magnetic tuning range which interfered with the peniotron mode and likely resulted in decreased power output. This mode was determined to be the fourth-harmonic gyrotron mode and was unexpected at the design beam current of 3.5 A used in the experiment. In fact, measurements of this gyrotron mode indicated a start current comparable to that of the design peniotron mode. The initial estimate of maximum output power was approximately 30 kW peak. However, the output coupling scheme of the device is being examined and re-calibrated to provide final values. The Q of the 4-vane interaction cavity at the competing mode frequency is also being analyzed and measured in an effort to explain the mode competition. The device was also observed to operate in a linear polarized peniotron mode for some regimes of beam voltage and beam alpha. This is also being investigated in terms of the interaction cavity parameters and gun performance. Results of the analysis will be presented along with final efficiency and power values.

Design and Test of a 34 GHz Peniotron

A peniotron, designed for optimized device efficiency and power output at 34 GHz, has been constructed at UC Davis. The device exploits the interaction of the second harmonic of an axis‐encircling electron beam with the fundamental mode of a four‐vane (magnetron like) slotted circuit. Output power and device efficiency have been predicted as 125 kW (peak) and 47% respectively.

Cusp gun driven peniotron

The UCD peniotron has been designed for optimum device efficiency and output power in second-harmonic operation at a 34 GHz fundamental-mode resonance. Key to the design is interaction with the axis-encircling electron beam. The UCD device incorporates over-coupling of the cavity to achieve the desired increased device efficiency. The predicted efficiency and power have been calculated from our large signal code.

Efficient 34 GHz second-harmonic peniotron with cusp gun drive

A 34 GHz peniotron, operating in the fundamental-mode of a slotted circuit, is under construction at UC Davis. The device is designed for second-harmonic interaction with the axis-encircling beam produced by a Northrop Grumman cusp gun. Recent efforts have concentrated on improving the magnetic field design and beam quality. Consequently, the cryogenic magnet of the initial design has been replaced with conventional coils and pole pieces. Measurement of the new magnet indicates that design goals for the magnetic field have been achieved and simulation of the beam predicts greatly improved quality.

Simulation and modeling of a 34 GHz cusp gun driven peniotron

A comprehensive review of the simulation and modeling work done to insure optimal realization of the design, including recent progress on the magnetic field design using the subsequent effect on beam quality were presented in this paper. However, the beam quality was critically dependent on the magnetic field in gun region, which has been the most difficult aspect of the design.