High efficiency operation of a 140 GHz pulsed gyrotron

Abstract

The operating characteristics of a 140 GHz, pulsed gyrotron are reported. Total efficiencies of 36% and ouput powers of 175 kW have been obtained in single mode operation.Measurements of power and efficiency have been made for a variety of modes between 120 and 160 GHz, and these results are in good agreement with predictions based on nonlinear theory. The best results have been obtained with isolated, asymmetric modes, such as the TE 4 , 2 , 1 (127.3 GHz), TE 2 , 3 , 1 (136.7 GHz),and the TE 3 , 3 , 1 (155.6 GHz). Although mode competition was found to prevent the TEO, 3 , 1 mode (139.5 GHz) from reaching the optimum operating conditions, an output power of 138 kW and total efficiency of 29% were achieved with this mode. A variety of new, highly accurate diagnostic techniques that have been developed to measure the power, frequency, and mode content of the output radiation will be reviewed. In addition, the operating characteristics of both laminar and nonlaminar magnetron injection guns will be compared. The high powers and efficiencies obtained in this experiment are promising for the extension of gyrotron output powers to the megawatt range.2

Frequency pulling and bandwidth measurements of a 140 GHz pulsed gyrotron

“…Such investigations of the emission frequency have recently been conducted, including frequency detuning measurements in a low power gyrotron (Brand et al 1983) and a comparison between self-consistent nonlinear theory and experimental results for a low Q, 35 GHz gyrotron operating in the TEO,II mode (Fliflet et al 1982). The present study differs from previous work in that good agreement has been achieved between the theoretical and experimental efficiency in our device (Kreischer et al 1984b). Under these conditions, the degree of agreement between theory and experiment for frequency tuning provides an important additional test of the theoretical formalism.…”

“…A detailed description of the design and initial operation of the experiment can be found in an earlier paper (Temkin et al 1982a). An extensive effort was subsequently made (Kreischer et al 1984b) to understand and improve the operating characteristics of the device. This eventually led to total efficiencies as high as 36% and peak output powers of 175 kW in single mode operation.…”

Photonic-Band-Gap Resonator Gyrotron

“…The present experiment is modeled on a previous device that we have studied, a 140 GHz conventional cavity gyrotron oscillator operating in the TE 031 mode [13]. The reduced mode competition observed in the present experiments and described below represents a clear and dramatic improvement over earlier results with a conventional cavity.…”

“…The surface absorbing layer of the calorimeter is increased to optimize absorption at 140 GHz. The details of the modification to the calorimeter are discussed in [13]. The frequency was measured by a heterodyne receiver system with a harmonic mixer and filters.…”

A gyrotron-powered standing-wave electromagnetic wiggler experiment

“…Power measurements were made using a thermopile calorimeter [20]. Far field patterns were obtain by scanning with a microwave diode.…”