MM-wave sheet-beam traveling-wave tube development at Los Alamos

Summary form only given. A sheet beam traveling-wave amplifier has been proposed as a bighpower generator for rf from 95 to 300 GHz, using a microfahricated rf slow-wave structure [I]. The planar geometry of microfabrication technologies matches well with the nearly planar geometry of a sheet beam, and the greater allowable beam current leads to high-peak power, high-average power, and wide bandwidths. Simulations of nominal designs using a vane-loaded waveguide as a slow-wave structure have indicated gains in excess of 1 dB/mm, with extraction efliciencies greater than 20%. We have identified stable sheet beam formation and transport as the key enabling technology for this type of device. Also, due to the high aspect ratio in the slow-wave structure, the rf coupling is complicated and requires multiple input and output couplers. The rfmode must be transversely flat over the width of the electron beam, which impacts both the vane design and the input and output coupling. We are pursuing a high-power demonstration experiment using a 120- kV, 20-A sheet electron heam with transverse size of 1 cm by 0.5 mm. This beam will interact at 95 GHz with a, as follows. A Class of the hybrid optimal problem is formulated and a hybrid dynamic programming principle (DPP) is presented which constitutes a generalization of the celebrated dynamic programming principle of Richard Bellman.