Albannay, Mohammed M., Joachim M.O. Vinther, Andrea Capozzi, Vitaliy Zhurbenko, and Jan Henrik Ardenkjaer-Larsen. “Optimized Microwave Delivery in DDNP.” Journal of Magnetic Resonance 305 (August 2019): 58–65.
Dissolution dynamic nuclear polarization (dDNP) has permitted the production of highly polarized liquid-state samples, enabling real-time imaging of metabolic processes non-invasively in vivo. The desire for higher magnetic resonance sensitivity has led to the development of multiple home-built and commercial dDNP polarizers employing solid-state microwave sources. Providing efﬁcient microwave delivery that avoids unwanted heating of the sample is a crucial step to achieve high nuclear polarization. Consequently, a process is described to reduce waveguide attenuation due to resistive loss thereby doubling the delivered power. A mirror and reﬂector are designed and tested to increase the microwave ﬁeld density across the sample volume resulting in a 2.3 dB increase of delivered power. Thermal considerations with regards to waveguide geometry and dDNP probe design are discussed. A thermal model of the dDNP probe is computed and experimentally veriﬁed.