Examination of two-stream instability for high power broadband RF amplifiers

Exploiting the two-stream instability to amplify radio frequency signals is an attractive concept because the interaction is extremely broadband and co-propagating beams of different energies make the instability convective instead of absolute, thus enabling operation as an amplifier. This holds out the possibility of bandwidth performance that rivals that of helical traveling wave tubes (helix TWT's) at much higher powers. Previous attempts1 at two-stream amplifiers were abandoned due to poor efficiency compared to helix TWTs. More recent work2 3 has indicated that the use of relativistic beams can increase the efficiency, perhaps as high as 50%.