Kilohertz Laser Plasma Acceleration and Inverse Compton Scattering Light Source

In this project, we seek to advance high intensity laser technologies of interest to laser plasma acceleration (LPA) of electrons, as well as for applications of laser-accelerated electrons for light source applications including Inverse Compton Scattering gamma sources and betatron x-ray sources. Past experience in laser science has proven that progress in understanding and optimizing any application is greatly accelerated when the process can be implemented with high repetition- rate kHz lasers: this not-only increases the average power and data acquisition rate, but also allows data acquisition at frequencies well above the “1/f noise” spectrum typical of experimental applications, allowing for faster optimization. Furthermore, the more-interactive nature of experimentation facilitates the discovery of new regions of parameter space and new phenomena. To-date, few experiments have made use of kHz lasers for laser plasma acceleration, because of the very high peak power requirement to accelerate electrons to relativistic energies of ~25-100 MeV, while maintaining the narrow energy spread necessary for the majority of applications. However, several recent developments have made such a prospect both interesting and feasible. Several groups have used very short-duration, sub-TW pulses to accelerate electrons to few-MeV energy with broad spectral bandwidth—proving that LPA at kHz repetition rates is possible. Also, several experiments done with lower rep-rate lasers have demonstrated that low energy spread electron beams in the range of 30-100 MeV can be generated using pulses of few-TW peak power. The development of a kHz repetition-rate, multi-TW laser will make it possible to access this parameter range—and is a feasible prospect. In the past, KMLabs has delivered ~ 1 TW/ 1 kHz lasers to customers; but to-date the laser technology has not as-yet reached any known physical limit. In this project, we plan to explore in Phase I, and implement in Phase II, the first, to our knowledge, multi-TW kHz repetition-rate laser. Our goal will be to demonstrate near-diffraction- limited focusability, a 15-20 fs pulse duration, a peak focused intensity consistent with all laser parameters, and a laser that can relaibly operate 24/7 without drift in parameters. This performance is possible using advanced pulse shaping and beam characterization methods, as well as optimized cryogenic cooling in Ti:sapphire amplifiers. To keep within the budget parameters of Phase II, we will make use of existing equipment at KMLabs—with the goal of implementing a sub-scale demonstration, and then collaborating with Lawrence Berkeley National Laboratory to implement the full system (100 mJ, 1 kHz, <20 fs) in Phase III, using a mix of SBIR-developed and new hardware. Working with LBNL will be the most direct method to prove out the laser capabilities, to directly contribute to advancement laser plasma electron acceleration science, technology, and applications. This will help to answer many critical questions for the field—whether LPA can be implemented with long-term stable output parameters, for applications such as implementing intense x-ray and gamma-ray sources.