A HIGH-CURRENT, MICRO-PULSE ELECTRON SOURCE

A MICRO-PULSE ELECTRON GUN THAT APPEARS CAPABLE OF PEAK CURRENTS OF ABOUT 10 KA WITH A MICRO-PULSE LENGTH OF SEVERAL PICOSECONDS (PS) OCCURING AT FREQUENCIES OF UP TO 10 GHZ IS BEING PLANNED. THE MICRO-PULSES OR BUNCHES ARE PRODUCED BY RESONANTLY AMPLIFYING A CURRENT OF SECONDARY ELECTRONS IN A RADIO FREQUENCY (RF) CAVITY. BUNCHING OCCURS RAPIDLY AND IS FOLLOWED BY SATURATION OF THE CURRENT DENSITY WITHIN TENS OF RF PERIODS. ONE WALL OF THE CAVITY IS HIGHLY TRANSPARENT TO ELECTRONS BUT OPAQUE TO THE INPUT RF FIELD. THE TRANSPARENT WALL ALLOWS FOR THE TRANSMISSION OF THE ENERGETIC ELECTRON BUNCHES AND SERVES AS THE CATHODE OF A HIGH VOLTAGE INJECTOR. AXIAL AND RADIAL EXPANSION OF THE PULSE IS MINIMIZED OUTSIDE THE CAVITY BY USING RAPID ACCELERATION AND A COMBINATION OF ELECTROSTATIC AND MAGNETIC FOCUSING. INSIDE THE CAVITY, RADIAL EXPANSION IS CONTROLLED BY AN AXIAL MAGNETIC FIELD. BOTH ANALYTIC THEORY AND PARTICLE-IN-CELL SIMULATION VERIFY THIS CONCEPT. PRELIMINARY ANALYSIS YIELDS THE FOLLOWING EXAMPLE PARAMETERS: WITH THE CAVITY OPERATING AT 6.4 GHZ, A 5 PS, 9.3 KA MICRO-PULSE IS PRODUCED AT AN ENERGY OF ABOUT 50 KEV; THE PULSE IS THEN ACCELERATED IN A FIELD GRADIENT OF 20 MV/M TO 2 TO 4 MEV, WHERE THE PULSE WIDTH HAS INCREASED BY ABOUT 2 PS. PHASE I AIMS AT A DETAILED ANALYSIS TO ESTABLISH CREDIBLE ESTIMATES OF BEAM POWER, PULSE LENGTH, TRANSMISSION EFFICIENCY, BUNCH STABILITY, AND OTHER KEY PARAMETERS. PHASE II WILL BE EXPERIMENTAL.