THz-pump and X-ray-probe sources based on an electron linac

Area of Science:

• Physics
• Materials Science
• Spectroscopy

Background:

• Ultrafast time-resolved diffraction requires synchronized pump-probe capabilities.
• Existing methods may lack the necessary temporal resolution or flux for certain applications.
• Compact, efficient beamlines are crucial for broader accessibility in scientific research.

Purpose of the Study:

• To present a novel, compact THz-pump and X-ray-probe beamline.
• To demonstrate simultaneous generation of THz radiation and hard X-rays from an electron linac.
• To enable high-resolution ultrafast time-resolved diffraction studies.

Main Methods:

• Utilizing a compact electron linac to generate two high-energy electron bunches.
• Employing a multifoil radiator to simultaneously produce THz radiation and hard X-rays.
• Implementing an adjustable optical delay for precise synchronization of THz and X-ray pulses.
• Conducting GEANT4 simulations to optimize radiator design and predict X-ray yield.

Main Results:

• Achieved peak THz power of 0.14 GW from a multifoil radiator with a 200 pC electron bunch.
• Optimized carbon foil radiators (0.5-1.0 mm) for high yield of 10-20 keV hard X-rays (approx. 10^3 photons/(keV pC-electrons)).
• Demonstrated generation of ~10^7 X-rays per 1 keV energy bin per second at 100 Hz repetition rate.
• Observed X-ray pulse durations of 400-600 fs, with minimal radiator heating.

Conclusions:

• The developed beamline offers a compact and efficient solution for ultrafast time-resolved diffraction.
• The synchronized THz and X-ray pulses enable advanced studies of dynamic processes in materials.
• The system's design parameters suggest high potential for various scientific investigations.