From simulation to fabrication: Realizing silicon crystalline undulators with silicon nitride stressor layer patterning

A crystalline undulator is a crystal exhibiting periodic deformations that cause channeled particles to oscillate, generating coherent electromagnetic waves. In this study, stressor layer patterning has been employed to induce the desired deformations on a silicon substrate. Finite element method simulations were performed to optimize the geometric parameters of the undulator. The primary focus was on achieving sinusoidal deformation with sub-millimeter period and amplitude exceeding 1 nm, utilizing the silicon (110) plane for its superior channeling properties. Key parameters, such as substrate thickness and undulator period, were meticulously refined to ensure uniform deformation while minimizing the impact of higher harmonics, which could degrade performance. Based on the simulation results, a crystalline undulator, 160 $\mu \text{m}$ thick and consisting of 10 periods with a period length of 334 $\mu \text{m}$, has been successfully fabricated. The final device demonstrates structural integrity and a uniform deformation extending up to 20 $\mu \text{m}$ from the surface. Specifically designed for use with 5–30  GeV particle beams, the undulator is capable of generating gamma photons in the 5–15  MeV range. This work effectively integrates advanced simulation techniques with precise fabrication methods, demonstrating the feasibility of crystalline undulators as high-performance devices for generating gamma radiation.