Large-orbit gyrotron operation in the terahertz frequency range

Area of Science:

• Physics
• Quantum Optics
• Plasma Physics

Background:

• High-harmonic generation (HHG) is a crucial process for producing coherent radiation in the extreme ultraviolet and X-ray regions.
• Generating coherent terahertz (THz) radiation via HHG is challenging due to the lower photon energies and different plasma dynamics involved.
• Gyrotrons are vacuum electronic devices capable of generating high-power millimeter and sub-millimeter waves, but their application to HHG is less explored.

Purpose of the Study:

• To investigate the feasibility of generating coherent terahertz high-harmonic radiation (THz-HHG) in a gyrotron.
• To develop and optimize an electron-optical system for producing a suitable electron beam for THz-HHG.
• To characterize the generated THz-HHG in terms of frequency, power, and stability.

Main Methods:

• Utilized a gyrotron equipped with a specialized electron-optical system featuring a cusp gun and adiabatic magnetic compression.
• Formed an 80-keV/0.7-A electron beam of gyrating electrons by adjusting voltages and magnetic fields.
• Detected and analyzed the generated radiation using appropriate diagnostic tools to determine frequency, power, and pulse characteristics.

Main Results:

• Successfully obtained coherent terahertz high-harmonic radiation.
• Achieved stable single-mode generation with output power ranging from 0.3-1.8 kW in microsecond pulses.
• Observed generation at four distinct frequencies within the 0.55-1.00 THz range.
• Generation occurred at resonant magnetic fields between 10.5-14 T.

Conclusions:

• Demonstrated the successful generation of coherent THz-HHG in a gyrotron.
• The developed electron-optical system effectively produced the required electron beam parameters for THz-HHG.
• The results indicate the potential of gyrotrons as a viable platform for high-power, coherent THz radiation sources.