SSP25-504_L-Band Buncher PH2

Sem-Sol proposes a Phase II SBIR effort to construct an L-band pre-buncher for operation with an X-band linear accelerator (LINAC). The pre-buncher encodes information on an electron beam in the form of current and voltage modulation. The beam is then accelerated to highly relativistic energies by the X-band LINAC, still carrying the encoded information. Sem-Sol’s approach for the L-band buncher is to use a helical slow-wave structure (SWS) based on that of helix TWT, with dimensions chosen to provide bunching of the electron beam for any L-band frequency. The helical structure is inherently broadband and helix TWTs can achieve as much as two octaves of instantaneous bandwidth. The current for the buncher is provided by an e-gun operating at 30 kV, with the current provided by a thermionic cathode. RF modulation of the beam is powered by an RF input amplifier that is capable of generating arbitrary waveform signals over 2 kW across the entire band of 1?2 GHz. The electron beam is guided through the pre-buncher by the magnetic field of a solenoidal magnet. The RF output of the buncher is used as a frequency diagnostic and dissipated into an RF load. A tungsten grid at the downstream end of the pre-buncher allows the electron beam to pass into the LINAC while isolating the pre-buncher from the RF fields of the LINAC.