Frequency-tunable, terahertz gyrotron for the direct measurement of the transition of positronium

Hyperfine transition of the ground-state positronium occurs at an energy level of about 203 GHz. Precise measurement of the transition frequency may be beneficial to the understanding of quantum electrodynamics in a bound state. This study reports the development of the frequency-tunable terahertz radiation sources. Two mechanisms of gyrotron backward wave oscillators will be proposed: TE02 reflective gyrotron backward-wave oscillator and 2nd harmonic TE21 gyro-BWO based on axis-encircling electron beam.