THE PHASE-LOCKED MAGNETRON ARRAY: A PRACTICAL RF SOURCE FORTHE NEXT LINEAR COLLIDER

A PHASE-LOCKED MAGNETRON ARRAY IS PLANNED AS AN RF-SOURCE FOR THE NEXT LINEAR COLLIDER (NLC) AT THE STANFORD LINEAR ACCELERATOR CENTER. THE PLANNED ARRAY CONSISTS OF A LARGE NUMBER (ABOUT 60) OF MODERATE POWER (ABOUT 5 MW), SHORT PULSELENGTH (ABOUT 100 NS), VERY EFFICIENT (ABOUT 70%), VERYSIMPLE 11.4 GHZ MAGNETRONS, POWER-COMBINED AND PHASE-LOCKED THROUGH A NETWORK OF DIRECTIONAL COUPLERS. ONE ARRAY IS USED PER FEED. THE APPROACH IS PRACTICAL BECAUSE ALL OF THEABOVE PARAMETERS HAVE BEEN DEMONSTRATED PREVIOUSLY IN RELATED CROSSED-FIELD DEVICES, AND THE PHASE-LOCKING SCHEME WAS RECENTLY DEMONSTRATED IN A SMALL, LOW POWER MAGNETRON ARRAY. THE COMBINING POWER FROM MULTIPLE TUBES APPEARS TO IMPROVE PHASE COHERENCE DRAMATICALLY AND MAY LEAD TO BENEFITS IN RELIABILITY AS WELL. IT APPEARS THAT BECAUSE OFTHEIR SMALL SIZE, THE USE OF SECONDARY-EMITTING CATHODES (COMMON IN HIGH POWER, CROSSED-FIELD TUBES), AND THE SHARING OF CERTAIN PARTS AND COMPONENTS BETWEEN TUBES, THE MAGNETRONS MAY ULTIMATELY COST WITHIN AN ORDER OF MAGNITUDE OF MICROWAVE OVEN MAGNETRONS. THIS DEVELOPMENT, TOGETHER WITH MODULATOR COST SAVINGS CAUSED, FOR EXAMPLE, BY LOW OPERATING VOLTAGE AND HIGH TUBE EFFICIENCY, WOULD MAKE THIS APPROACH THE MOST COST-EFFECTIVE NLC RF SOURCE BY AN ORDER OF MAGNITUDE. THE PHASE I EFFORT IS MAKING STRIDES TOWARD DEMONSTRATING EACH OF THESE ASSERTIONS.