PROGRESS OF CW AND SHORT-PULSE CALORIMETRIC LOADS FOR HIGH POWER MILLIMETER-WAVE BEAMS

A family of compact matched loads for high power millimeter wavelength beams absorption, good for atmospheric and vacuum operation, suited for CW (1MW) or short pulses (2MW, 0.ls) precise measurement has been designed to test high power gyrotrons. The common origin for members of this family is a toad developed for the ECRH FTU plant (140 GHz, 0.5 s, 0.5 MW) and successfully exploited. A CW version of the load has been built and used as absorber and bolometer for the high-power test of a remote steering launcher mock-up at 140 GHz. The high-power tests have been performed with powers up to 700 kW and pulse lengths of up to 10 seconds without limitation due to the load. An investigation of the gas emission properties of the load coating material at high temperature and under vacuum has been accomplished by means of high power deposition from an electron gun. Results from these tests are presented.