Optimally designed traveling wave tube for operation backed off from saturation

A traveling wave tube comprising:

• a tube member;
• a helix member located within the tube member, the helix member provided with an input end for receiving a microwave input signal having a power level and an output end for supplying a microwave output signal having a power level;
• an electron gun assembly adjacent the input end of the helix member for injecting electrons as an electron beam along an axial path through the helix member;
• three Boron Nitride (BN) supporting rods engaged between the tube member and the helix member for supporting and transferring heat away from the helix member, each of the three BN supporting rods having a plurality of layers, wherein each of the three BN supporting rods is oriented in a direction perpendicular to the plurality of layers between the helix member and the tube member;
• and
• a magnetic focusing device for generating a magnetic field having a strength to confine the electron beam to the axial path, wherein the strength of the magnetic field is sufficient to confine the electron beam only when the power level of the microwave input signal is selected such that the power level of the microwave output signal is at least 6 dB lower than a power level of the microwave output signal at saturation.

A method for operating a traveling wave tube provided with a slow wave structure (SWS) having an input end for receiving a microwave input signal having a power level and an output end for supplying a microwave output signal having a power level, the method comprising:

• injecting electrons at the input end of the SWS to form an electron beam along an axial path through the SWS;
• applying the microwave input signal to the input end of the SWS;
• and
• generating a magnetic field having a strength to confine the electron beam to the axial path, wherein the strength of the magnetic field is sufficient to confine the electron beam only when the power level of the microwave input signal is selected such that the power level of the microwave output signal is at least 6 dB lower than a power level of the microwave output signal at saturation.