Theoretical and Experimental Investigations of Terahertz-Range Gyrotrons with Frequency and Spectrum Control

Bulletin of the Polish Academy of Sciences: Technical Sciences

“…The reported theory and experiment discrepancy is smaller than 3 × 10 −5 , which proves the credibility of the approach presented in [91]. The total frequency tuning range was 4 MHz with frequency stability of 1 Hz, which can be compared to a stability of 0.5 MHz for the free running gyrotron [62]. Frequency stabilization by delayed reflection of the output radiation is experimentally simple as it is done outside the gyrotron tube [62].…”

“…This implies that the cavity is relatively long, and that the middle part of the resonator is sometimes slightly up-tapered. A series of gyrotrons, which possess continuous tuning capability, have been demonstrated by several groups: MIT group gyrotrons, which use this technique described in [40,42,44,49,50]; Fukui group gyrotrons -described in [41,[51][52][53]; CRPP-EPFL in Switzerland -described in [54][55][56][57]; KIT in Germany -described in [58,59]; and Nizhny Novgorod Technical University/GYCOM in Russia -described in [60][61][62].…”

“…A shorter cavity requires a higher electron beam current in order to provide starting conditions for high order modes. By reducing the cavity length and the order of the operating transverse mode, a fairly wide frequency band of the gyrotron generation can be achieved [62]. In the paper, changes in output power and frequency caused by magnetic field variation is presented for the 0.2 THz gyrotron.…”

“…Control voltage was applied between the cavity (body) and collector (ground potential). The high capacitance of the gyrotron body (ground), means that this method has a significantly lower PID bandwidth (fast variations of voltage are very difficult to achieve) [84] when compared to the anode voltage tuning method [62]. On the other hand, it does not require the high voltage cathode power supply to be modified.…”

Russian Gyrotrons: Achievements and Trends

“…Analytical estimates show that the frequency tuning via excitation of axial modes can be achieved in a gyrotron with a short cavity driven by an electron beam with high current. Simulations [44] and preliminary experiments [45] demonstrated a possibility of wide-band (about 10%) fine frequency tuning. An output power of 0.5 to 1 kW can be obtained at a frequency of about 0.2 THz within a 10 GHz band, which are the parameters needed for testing of quantum electrodynamics predictions in positronium spectroscopy measurements.…”