Frequency-agile gyrotron for electron decoupling and pulsed dynamic nuclear polarization

Area of Science:

• Physics
• Spectroscopy
• Materials Science

Background:

• Nuclear Magnetic Resonance (NMR) spectroscopy benefits from advanced microwave control for dynamic nuclear polarization (DNP).
• Existing gyrotron technology has limitations in frequency agility and response speed for pulsed NMR applications.

Purpose of the Study:

• To develop and characterize a frequency-agile gyrotron for synchronized pulsed control of electron and nuclear spins.
• To demonstrate the application of this device in frequency-swept DNP experiments.

Main Methods:

• Utilizing an arbitrary waveform generator (AWG) to control microwave frequency via anode voltage modulation.
• Achieving frequency sweeps at rates of 20 MHz/μs over a 670 MHz bandwidth.
• Recording frequency-swept DNP enhancement profiles for endofullerenes.

Main Results:

• Demonstrated rapid frequency response by varying anode voltage, surpassing electron emitter potential changes.
• Achieved high frequency sweep rates and bandwidth in a static magnetic field.
• Observed narrow DNP linewidths (<10 MHz) for endofullerenes, indicating frequency and phase stability.

Conclusions:

• The frequency-agile gyrotron provides a powerful tool for advanced NMR techniques, including pulsed DNP mechanisms.
• The device's stability and agility enable efficient frequency-swept DNP experiments without altering NMR hardware.
• Potential exists for converting commercial continuous-wave gyrotrons into similar agile microwave sources.