32c. Integrated Photonic Structures for Bunch Shaping in Structure Wakefield Accelerators

Future beam-driven gigavolt-per-meter structure wakefield accelerators for a TeV scale lepton collider will require extremely high wall plug efficiency, which in turns requires extracting the maximum amount of energy from the drive beam. Bunchlet trains can suppress the dipole wakes that limit the maximum energy extraction from the drive beams. These trains are currently produced using masks, which throw away a substantial fraction of the beam. A technique to produce uniformly spaced bunchlet trains without sacrificing total charge is critical for achieving the wall plug efficiency required for a future collider. Integrated photonics structures can be used to manipulate the electric fields on the surface of a photoemitter cathode. These shaped surface fields can be used to produce tailored transverse emission profiles, which can be turned into a longitudinal profile using emittance exchange. This project will design such an integrated photonics structure suitable for producing bunchlet trains to drive a structure wakefield accelerator. In Phase I, high-fidelity simulations will be conducted of an accelerator facility suitable for a proof-of-concept experiment. Those models will then be used to backtrack an ideal distribution from the end of an emittance exchange beamline to the cathode surface. That emission pattern will then be used to design an integrated photonics structure. An experimental design will be produced for a proof-of-concept experiment to take place during Phase II. The ability to design arbitrary emission patterns from a cathode will improve future accelerator designs, enabling novel ring-shaped beams for instance, or more efficient structure wakefield accelerator driven free-electron lasers. It will also open up new experimental possibilities with transmission electron microscopy.