THz two-beam acceleration

Future accelerators require compact methods to generate very high accelerating fields. One promising approach is THz two-beam acceleration, where an intense drive beam generates terahertz radiation, and that radiation accelerates a separate main beam.

This research studies how to realize efficient THz-based acceleration in a practical beamline. Key questions include how to generate strong THz fields, how to maintain stable drive-beam transport, and how to extend the interaction length between the THz field and the accelerated beam.

The goal is to develop compact accelerator concepts that can provide high gradients beyond conventional RF acceleration.

THz two-beam acceleration uses two separate beams: a drive beam and a main beam. The drive beam passes through a wakefield structure and generates a strong electromagnetic wake. This wake is then transferred to the main beam, where it can be used for acceleration. In this concept, the drive beam acts as the power source, while the main beam receives the accelerating field.

To realize this concept at THz frequencies, we are developing compact corrugated structures with very small geometric features. The fabrication approach uses thin metallic plates, typically 50–200 μm thick, which are stacked to form a beam aperture of about 1 mm diameter. This plate-based approach provides a practical route toward structures operating at hundreds of GHz, where conventional machining becomes difficult.

We have fabricated and tested a 200 GHz corrugated wakefield structure as an important step toward THz two-beam acceleration. Wakefield measurements confirmed the presence of the expected electromagnetic wake, and the measured field structure showed good agreement with simulations. This result demonstrates that high-frequency wakefield structures can be fabricated and characterized experimentally, providing a foundation for future THz acceleration experiments.