Oscillation characteristics of a continuously frequency tunable 400 GHz gyrotron

Irradiation of intense electromagnetic (EM) wave in sub-millimeter wave region is effective in enhancing the sensitivity solid state nuclear magnetic resonance (NMR) spectroscopy (Dynamic nuclear polarization (DNP) method). It is important to irradiate EM wave with a optimal frequency at stimulated absorption or emission peak. Continuous tunability of frequency is required to obtain the maximum enhancement. The irradiation power needs several Watts for DNP. We have already developed a frequency tunable gyrotron which is of demountable type. The frequency tunable range was 1.6 GHz and the output pwer was 10-30 W. DNP-NMR experiment is going on with this gyrotron. Then, a new sealed-off gyrotron has been developed to improve output power, the stability and CW operation