Laser-Free RF-Gun as a Powerful THz Source

THz technology has a rapidly growing number of potential applications in solid-state, nuclear physics, medicine, biology, remote sensing, imaging, industry and communications. However, THz radiation facilities based on FELs, electron storage rings, and/or energy recovery linacs are too large, expensive, and not readily available for a broader community of users to operate it on a flexibly customized, on-demand, and independent basis. In this project we are developing a compact and much less expensive coherent terahertz source that allows generation of high peak and average power. The approach uses microbunching provided by the beam compression in an alpha-magnet, beam pre-bunching in the RF gun, and resonant Cherenkov radiation in a robust radiator. The THz radiation in the source can be accompanied by synchronized, intense, sub-ps bursts of hard X-ray radiation for additional capabilities. Phase II tasks have been completed and all objectives were met. All the source components including the THz beamline, 2D steerable radiator integrated with antenna and bending magnet, table-top alpha magnet with moveable scraper and diagnostics ports have been designed and assembled at the APS Injector Test Stand facility. THz radiation was successfully produced at 0.52 mm wavelength, ~ 330 J/cm2 macropulse energy density, and 7% bandwidth, which is close to that simulated. In response to the desires of our beta customer, the APS light source, in Phase IIA we will design, fabricate, assemble, and commission a prototype of a turnkey tunable THz source. A new system will be designed and tested to provide frequency and spectrum tunability. The system will allow in-vacuum manipulation to change the gap, angle, absolute and relative positioning of the slow wave radiating structure. One part of the radiator system will be designed to provide radiation frequencies over 2 THz by using a CVD diamond coated structures and 3D periodic micro-structures. Another part of the radiator system will provide broadband radiation by using a tapered structure in combination with a micro-wiggler. A novel steering system with capability of precise beam translation would enable to maximize the radiation intensity and switch the beam interaction with the radiator parts having different dispersion. The components and entire system will be tested and commissioned at APS Injector Test Stand facility.