Modification of MEA modulator-klystron units enabling short pulse injection into a pulse-stretcher ring

In order to modify the present 500-MeV, 1% duty factor Medium Energy Accelerator (MEA) into a 900 MeV, 0.1% duty factor injector for a planned pulse-stretching ring, the present modulator-klystron units have to be adapted from the 4-MW, 2% duty factor mode of operation into the 10-Mw, 0.2% duty factor mode. The design principles of the modulators are discussed. Special attention is given to the video-pulse shape requirements, dictated by the future performance of the pulse stretcher. This device is required to deliver low-emittance, high-duty-factor (~90%) beams for nuclear physics experiments. Some prototype tests of the video-pulse forming modifications are presented