Speaker
Description
Laser-plasma accelerators (LPAs) are highly promising drivers for compact X-ray free-electron lasers (XFELs). However, fully exploiting their ultrashort, high-current bunches requires mitigation of the percent-level energy chirp commonly present in LPA beams as well as diagnostics capable of resolving femtosecond temporal structure. Recent demonstrations using conventional radiofrequency (RF) cavities have successfully achieved active chirp correction of LPA beams, but the long RF wavelengths require millimeter-scale longitudinal bunch decompression to access sufficient field variation, reducing the peak current critical for FEL gain. Likewise, RF transverse deflecting structures can achieve excellent temporal resolution, but typically require large-scale infrastructure and sophisticated synchronization systems.
Terahertz (THz) fields provide a wavelength regime naturally matched to the native longitudinal scales of LPAs. For dechirping, a 1 THz driver ($\lambda \approx 300~\mu$m) requires only tens of micrometers of beam stretching to compensate correlated energy spread while largely preserving peak current, with estimated THz pulse energies in the ~1 mJ range. For diagnostics, THz streaking structures supporting GV/m fields can provide high-gradient transverse deflection with the potential for sub-10-fs temporal resolution. Because LPAs are intrinsically laser-driven, generating THz pulses directly from the LPA drive laser also provides optical synchronization to the electron beam, avoiding the timing complexity and residual jitter associated with external RF systems.
These applications are enabled by recent advances in high-energy THz generation and THz-driven accelerator technology. Laser-based nonlinear down-conversion techniques have recently enabled the generation of spectrally tailored mJ-class THz pulses suitable for accelerator applications. Concurrently, THz-driven accelerator structures have demonstrated high-gradient acceleration, compression, and streaking from the keV to multi-MeV regime, including recent operation at beam energies up to ~35 MeV.
This presentation will discuss recent work investigating the feasibility of applying THz-driven accelerator technology to direct manipulation of LPA beams. Initial calculations indicate that THz-driven dechirping and streaking are not only feasible, but offer substantial advantages for preserving ultrahigh peak current while enabling femtosecond-scale longitudinal diagnostics relevant to next-generation compact light sources. Recent progress in THz-source development and experimental validation of THz-driven accelerator structures will also be summarized to clarify the technological readiness of this approach.
| Working group | WG5 |
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