Abstract: Dissolution dynamic nuclear polarization (dDNP) involves polarizing the sample under microwave irradiation at a low-temperature and strong-magnetic field, dissolving it by the solvent of high-temperature and high-pressure, then injecting it rapidly into an NMR/MRI for the detection. The dissolution system is a critical component in the dissolving and injecting process, and its performance directly affects the melting and transfer efficiency and the high polarization retention. We present an automated dissolution system using a dual-loop PID control algorithm to maintain the pressure around 1.7 MPa within 9 minutes. The system can dissolve a solid sample of -271 ℃in the self-developed 5 T dDNP polarizer and transfer it to the 7 T NMR system at an distance of 11.2 m for detection in 4 s . The enhancement of the ¹³C NMR signal of sodium [1-¹³C]-pyruvate at room temperature is 9 050. Our work developed an automated dissolution system that simplifies the operation steps, ensures detection consistency, and improves experimental safety.

Key words: dynamics nuclear polarization, double-loop PID control algorithm, dissolution system, high temperature and high pressure