Hybrid structure-wakefield accelerator with a plasma photocathode

STATEMENT OF THE PROBLEM High brightness beams are needed for applications ranging from high-energy physics, and biological imaging such as ultrafast electron microscopy. The recent demonstration of a plasma photocathode showed that high brightness beams are achievable in a plasma wakefield accelerator. However, the practicality of realizing the concept is challenging experimentally. TECHNICAL APPROACH In order to employ the plasma photocathode process, we replace the plasma wakefield accelerator with a dielectric wakefield accelerator. This accomplishes two goals. First, the technical challenge of generating and maintaining a hot, dense plasma is replaced with a solid-state structure. Second, the associated synchronization requirements are relaxed because a longer wavelength is used for acceleration. As a side benefit, since the dielectric sustains moderate gradients compared to plasma, the respective energy spread of the resultant beam can be lower resulting in high six-dimensional brightness. PHASE I PLANS The Phase I project aims to further optimize the plasma photocathode process based on lessons learned from prior experiments. Specifically, we will aim to upgrade the drive beam at the facility and employ tapered or pillbox-shaped structures to enhance the trapping potential, explore different laser parameters to optimize the ionization process, continue experimental work to optimize the drive beam parameters for high field, and conduct simulations to support the design and data analysis, in preparation for a full-scale experiment. COMMERCIAL APPLICATIONS AND OTHER BENEFITS The program results will yield a compact package of a plasma photocathode that can be driven by traditional radio-frequency based sources or novel advanced sources such as laser plasma accelerators. The unit will be designed for applications that require high brightness.