Speaker
Description
The process of Dynamic Nuclear Polarization (DNP) requires a magnetic field that is simultaneously very strong (2.5 - 5 T) and very uniform (dB/B ≤ 10-4). Often, this is achieved by supplementing an existing strong field already incorporated into a spectrometer with small correction coils internal to the target. This active polarization technique allows for continuous polarization while operating at temperatures near 1 K. In experiments using spectrometers which are incompatible with large external magnets, the frozen spin technique is instead employed. In this approach, targets are temporarily placed into a separate external field during an initial polarizing phase before being removed and positioned within the spectrometer. There, polarization is maintained using small internal holding coils at temperatures near 30 mK. Although extremely successful, the low temperature required for frozen spin limits beam intensity. A new strategy is proposed wherein small internal polarizing coils produce sufficiently strong and uniform fields for active DNP without the need for external magnets. I will present the current status of these developments and discuss their potential benefits to experimental efficiency and flexibility.
