Experimental considerations in electron beam transport on a nanophotonic chip using alternating phase focusing

Not long after the laser was invented, it has been marked as a candidate source of strong, high-frequency electromagnetic radiation for the acceleration of particles. Indeed, while today’s complex particle accelerator facilities are an astonishing culmination of decades of work contributed by generations of physicists, engineers, and a host of scientists, new trends and acceleration technologies have recently been proposed and demonstrated. One of these technologies involves the miniaturization of particle accelerators, which is achieved by replacing the radiofrequency (RF) electromagnetic fields accelerating the particles with fields in the optical frequency range using lasers. This entails using nanophotonics structures to provide the required field distribution. Recently, individual elements toward the nanophotonics counterpart of RF accelerators have been demonstrated. Similarly, active electron transport through such a structure has been shown, which was based on the concept of alternating phase focusing. In this contribution, we discuss and augment on the recently demonstrated principle of alternating phase focusing using optical frequencies and provide new insights from relevant simulations and experiments. In particular, we show how to identify possible imprecisions and parasitic effects from time-delay scans and discuss how the transmission of electrons through the nanometric structure depends on the temporal overlap between electron and laser pulses. We also show how the incidence angle of the electron beam can affect the measured transmission of electrons through the structure.