Waveguide coupled rectangular grating periodic structure for low-voltage amplifiers

Summary form only given, as follows. The rectangular grating periodic structure is a slow wave device which offers higher power, low voltage, compact Ku band amplifiers, with the advantage of sheet beam compatibility. Experiments and theoretical modelling have been done for two types of gratings, one with a large groove depth to grating period (d/p=7.43) called the deep groove grating and the other with a smaller ratio (d/p=0.446) called the shallow groove grating. Phase measurements are obtained utilizing a probe signal in a slotted line. This is mixed with the reference signal and fast Fourier transformed (FFT) to yield the experimental, dispersion relation. The transmittance and growth analysis has provided information about the beam interaction for shallow and deep groove gratings. The amplifier measurements are done using a round probe beam of 1 mm diameter from a 10 kV, 0.25 A, electron gun, confined by a 1 kG focussing solenoidal magnetic field. The microwave power has been coupled to the grating system utilizing loops. The observed gain yields single particle amplification. To observe the linear gain regime for the amplifier, the loop coupling has been upgraded to a waveguide coupling scheme. A waveguide Tee section is used for launching the microwave power without affecting the beam launching. This enhances the power injected in the TE/sub Z10/ waveguide mode into the amplifier system which converts to the TE/sub X10/ hybrid mode in the grating periodic structure. The phase and linear gain measurements for the shallow groove backward wave amplifier with waveguide coupled power launching are presented. We have also begun PIC simulation of the beam grating amplifier system.