Frequency-chirped dynamic nuclear polarization with magic angle spinning using a frequency-agile gyrotron

Area of Science:

• Magnetic Resonance Spectroscopy
• Physical Chemistry
• Materials Science

Background:

• Dynamic Nuclear Polarization (DNP) enhances Nuclear Magnetic Resonance (NMR) signals.
• Continuous-wave (CW) DNP is a standard technique, but signal enhancement can be limited.
• Magic Angle Spinning (MAS) is crucial for high-resolution solid-state NMR.

Purpose of the Study:

• To investigate the efficacy of frequency-chirped DNP combined with MAS.
• To compare the signal enhancement achieved by frequency-chirped DNP against CW-DNP.
• To detail the development and performance of a custom frequency-agile gyrotron for this application.

Main Methods:

• Implementation of frequency-chirped DNP using a custom frequency-agile gyrotron.
• Application of MAS NMR at 7 Tesla magnetic field strength.
• Utilized the TEMTriPol-1 biradical for DNP experiments.

Main Results:

• Achieved a DNP enhancement factor of 137 with frequency-chirped DNP.
• Observed a 19% increase in enhancement compared to CW-DNP (enhancement factor of 115).
• Developed a gyrotron capable of >10 W output power over a 335 MHz bandwidth.

Conclusions:

• Frequency-chirped DNP with MAS provides superior NMR signal enhancement compared to CW-DNP.
• The developed frequency-agile gyrotron is effective for advanced DNP applications.
• This technique holds significant promise for advancing magnetic resonance.