Measurement of velocity spread of axis-encircling electron beam

Summary form only given. To achieve high efficient harmonic gyro-amplifier, gyro-peniotron research is underway at NRL using axis-encircling beam and magnetron-type slotted waveguide structure. The device performance depends critically on the quality of the electron beam. After several years´ efforts, a new type axis-encircling gun with triple pole piece and center post, has been designed and fabricated by Litton. Electron ray trajectory calculations for the gun, performed using the deformable mesh code DEMEOS at Litton, indicate that the beam of /spl Delta/v/sub z//v/sub z/<3% and /spl Delta/rg/rg<6% can be realizable at beam velocity ratio(/spl alpha/) of 2 using 70 kV, 3.5 A beam. The microperveance of the beam was measured to be 0.216 up to 70 kV. Experimental work is in progress to characterize the electron beam a and electron beam alignment using capacitive probes, and axial velocity spread using a movable collector. Initial test shows the measurement agrees reasonably well with the simulation. The detailed experimental results will be presented and compared with simulation.