Ph.D Thesis

Ph.D StudentHanuka Adi
SubjectStructure-Based Laser-Driven Optical Accelerators
DepartmentDepartment of Electrical and Computers Engineering
Supervisor PROF. Levi Schachter
Full Thesis textFull thesis text - English Version


Particle accelerators are ubiquitous, we rely on them for numerous medical, scientific and industrial uses daily. However, today's accelerators are yet relatively large, expensive and specialized machines. This has spawned great interest in the development of more compact and economical accelerators. Dielectric Laser Accelerators (DLAs) are an attractive approach over conventional RF accelerators. Most notably, the reduction of 4-5 orders of magnitude in wavelength facilitates a dramatic reduction in size of the machine, and secondly, DLAs are able to support accelerating fields 1-2 orders of magnitude higher than conventional RF machines.

In this thesis we present designs, electrodynamics simulations, and experimental results regarding structure based laser driven accelerator. Our findings contribute to the realization of the envisioned optical Acceleration Module on Chip (AMC).

Presented next in the order of occurrence we consider first a tapered Bragg waveguide to serve as a coupler which ensures efficient injection of laser power in an acceleration structure, or as an optical booster that aims to capture low energy electrons from the injector into the accelerator; while the structures look alike, the design in both cases is quite different. We investigate the dynamics of the trapping process and determine its optimal operation point. 

Next, we propose a general approach to determine the optimal parameters for DLAs in a self-consistent way, both in a single and in a train of electron microbunches. Accounting for beam-loading effect on the material and the laser, we demonstrate that the accelerating electric field in the DLA could be ~10 GV/m, namely 3 orders of magnitude higher than in RF accelerators. We also show that the maximum acceleration efficiency could be doubled by using artificial materials with permeable properties, instead of dielectrics.

In addition, two experiments were carried out at SLAC National Accelerator Laboratory (Stanford, California, USA) and at Fermi National Lab (Illinois, USA). In the first experiment, we develop unique damage measurement tools that are critical for the evaluation and optimization of DLA structures, since it provides an upper limit on the achievable accelerating electric field in the accelerator. In the second experiment, we report a single-pass amplifier optimization to achieve a stabilized laser pulse train required for uniform acceleration.

Our work lays the ground for a wafer scale accelerator in the range of MeV to GeV, thus bringing us one step closer to realizing the envisioned AMC.