A high-power, high-repetition-rate THz source for pump-probe experiments at Linac Coherent Light Source II.

Area of Science:

• Accelerator Physics
• Ultrafast Science
• Terahertz (THz) Science

Background:

• Experiments at X-ray free-electron laser (XFEL) facilities require synchronized THz and X-ray pulses.
• Existing THz pulse generation methods may not meet the stringent requirements for XFEL experiments, such as tunability, narrow bandwidth, phase stability, and high fields.
• Linac Coherent Light Source II (LCLS-II) demands specific THz pulse characteristics for pump-probe experiments.

Purpose of the Study:

• To investigate a novel two-bunch scheme for generating THz radiation at LCLS-II.
• To achieve frequency-tunable (3-20 THz), narrow bandwidth (∼10%), carrier-envelope-phase-stable THz pulses with high fields (>1 MV/cm).
• To ensure precise synchronization between the generated THz pulses and X-ray pulses from LCLS-II.

Main Methods:

• Utilized a two-bunch electron beam scheme at LCLS-II.
• The first bunch generated THz radiation in an electromagnet wiggler placed after the X-ray undulator.
• Optimized the initial time delay between the two bunches to compensate for THz transport path differences.

Main Results:

• Demonstrated the feasibility of generating THz radiation using the two-bunch scheme.
• Detailed the beam dynamics, THz wiggler performance, and radiation characteristics.
• Described the transport system for delivering THz pulses to the experimental hall.

Conclusions:

• The proposed two-bunch scheme is a viable method for producing the required THz pulses at LCLS-II.
• This approach enables high-field, tunable, and synchronized THz-X-ray experiments.
• The study provides a comprehensive description of the generation and transport system for these advanced experiments.