An experimental clustered-cavity<sup>TM</sup>KlystronR.S. Symons, Bernard Arfin, R.E. Boesenberg, P. Ferguson, M. Kirshner, J.R.M. Vaughan1987 International Electron Devices Meeting1987The theory of the Clustered-Cavity<sup>TM</sup>Klystron (CCK) is discussed. Experimental results for two iterations of an experimental 13-cavity megawatt CCK are presented. Record bandwidth for a klystron of this power and length has been achieved.