Amanda Shing

Massachusetts Institute of Technology

Griffin Laboratory
Mentor: Galia Debelouchina

Summer 2007

Instrumentation for Solid State NMR with Dynamic Nuclear Polarization

The focus of this project is the design and construction of a new Magic Angle Spinning (MAS) Solid State Nuclear Magnetic Resonance (SSNMR)/Dynamic Nuclear Polarization (DNP) probe for 1 H Larmour frequency of 211MHz (4.96 Tesla).   The probe will contain four channels: 1H, 13C, and 15N detection channels, as well as a waveguide to deliver microwaves to the sample for DNP.   DNP is a method that enhances signal to noise of NMR spectra by several orders of magnitude, therefore allowing reduced acquisition times.   A DNP sample typically contains sources of unpaired electrons.   When the sample is irradiated with microwaves of the proper frequency, they polarize the unpaired electrons.   The polarization is then transferred to the nuclei, creating greater sensitivity.   Additionally, low temperatures allow the process to be more efficient; therefore, new solid state probe will be able to reach temperatures as low as 90K. Because DNP involves cryogenic temperatures, time must be taken to cool the sample and probe inside the magnet.   Thus, removing or exchanging the sample proves to be quite time consuming, as the entire probe must be removed, dried of condensed water, and re-cooled in order to begin another experiment.   However, the probe will also contain a sample ejection system, which prevents the need to remove the probe, and much time can be saved.   Currently, the mechanical design is based on a modified design for a recently developed probe which incorporates a sample eject.   The electronic portion will be modeled after a circuit from another existing NMR probe.   Both these probes were also constructed in the Griffin Research Group.