Gyrotrons FU CW V and FU CW VIII for measurement of hyperfine structure of positronium

For direct measurement on hyperfine structure of positronium, high power sub-THz radiation sources, Gyrotrons FU CW V and FU CW VIII have been developed. FU CW V is a frequency fixed gyrotron operating at 203.3 GHz for the proof-of-principle experiment and FU CW VIII a frequency continuously tunable gyrotron to measure directly the energy difference between orth- and para states of positronium.