Phase Measurements of a 140-GHz Confocal Gyro-Amplifier

Area of Science:

• Physics
• Electrical Engineering
• Plasma Physics

Background:

• Gyro-amplifiers are crucial for high-frequency, high-power applications.
• Understanding phase stability is essential for coherent operation in these devices.
• Previous phase measurements in gyro-amplifiers above W-band are scarce.

Purpose of the Study:

• To experimentally measure the phase stability of a 140GHz pulsed gyro-amplifier.
• To investigate the phase dependence on cathode voltage.
• To compare experimental results with simulations and identify dominant factors influencing phase stability.

Main Methods:

• Experimental measurement of phase stability and phase-voltage dependence in a 1kW, 140GHz pulsed gyro-amplifier.
• Operation at optimized conditions (47 kV, 1 A, ~30W output power) for precise measurements.
• Comparison of experimental data with simulation results.

Main Results:

• The gyro-amplifier demonstrated excellent phase stability, both pulse-to-pulse and intra-pulse, under constant operating conditions.
• A phase variation of 130±30°/kV was measured, showing excellent agreement with simulations.
• The non-adiabatic nature of the electron gun was identified as the primary cause for voltage-dependent phase shifts.

Conclusions:

• The 140GHz gyro-amplifier exhibits robust phase stability.
• Non-adiabatic electron guns significantly impact phase stability due to their steep pitch factor dependence on voltage.
• Adiabatic electron guns are predicted to offer superior phase stability, crucial for future high-frequency gyro-amplifier development.