Generation of chaotic radiation in a driven TWT amplifier with delayed feedback

We have been investigating the use of traveling wave tube (TWT) amplifiers as sources of chaotic radiation. To generate chaos, the TWT amplifier is made to operate in a highly nonlinear regime by recirculating a fraction of the TWT output power back to the input in a delayed feedback configuration. The system can transition into a chaotic state by varying the feedback attenuation and phase. Additionally, a drive signal provides a constant external force to the system. Thus, the experimental system behaves like a forced nonlinear oscillator. The study illuminates the different transitions to chaos that result from the choice of feedback filter and other parameters such as the drive signal frequency or intensity and the setting of the phase shifter in the feedback circuit.