Undulator radiation in the THz range

The experimental device for generation of undulator radiation in terahertz wavelength region by use of undulator on ferromagnets is created. The device is based on a beam of a microtrone with the energy 7.5 MeV. The radiation wavelength is 200 micron. Registered spontaneous radiation has a power of 10 microwatt at a current of a beam 2 mA in a pulse. With the optical resonator, in a mode, the amplification of 6 percent is received, that in some times is more than expected value. This effect is explained as a result of partial coherence of radiation.