Testing of 10 MW multibeam klystrons for the european X-ray fel at DESY

For the European XFEL project multi-beam klystrons, which can produce RF power of 10 MW, at an RF frequency of 1.3 GHz, 1.5ms pulse length and 10Hz repetition rate, were chosen as RF power sources. So far we have three companies which produce this kind of new klystron. At DESY we installed a new test stand dedicated for testing this new type of RF power source. So far we have tested several tubes from Thales (TH1801), Toshiba (E3736) and CPI (VKL8301) in our test stand. In this paper we give an overview of the test facilities and we summarize the current test results of the L-band multi-beam klystrons (MBK).