Intense terahertz pulses from SLAC electron beams using coherent transition radiation

Area of Science:

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

Background:

• SLAC National Accelerator Laboratory operates two advanced electron accelerators: the Linac Coherent Light Source (LCLS) and the Facility for Advanced Accelerator Experimental Tests (FACET).
• These accelerators produce high-charge, high-peak-current, femtosecond electron bunches, which are crucial for generating intense terahertz (THz) pulses.
• Intense broadband THz pulses are generated via coherent transition radiation.

Purpose of the Study:

• To characterize the properties of THz pulses generated from electron bunches at LCLS and FACET.
• To investigate the nonlinear response of materials when interacting with these intense THz pulses.

Main Methods:

• Utilizing the femtosecond electron bunches from LCLS and FACET to generate THz pulses through coherent transition radiation.
• Measuring THz pulse duration, spectral content, and energy.
• Conducting preliminary observations of nonlinear material interactions with the generated THz pulses.

Main Results:

• THz pulse durations of 20 fs RMS (LCLS) and 80 fs RMS (FACET) were achieved and are tunable.
• Emission spectra cover 3-30 THz (LCLS) and 0.5 THz-5 THz (FACET).
• Terahertz pulse energies of 0.2 mJ (LCLS) and 0.6 mJ (FACET) were recorded, with peak electric fields reaching 4.4 GV/m at LCLS.

Conclusions:

• SLAC's electron accelerators are capable of generating high-quality, intense broadband THz pulses.
• The generated THz pulses show potential for probing and driving nonlinear phenomena in materials.