Thermal management for the underwater frontend and readout electronics of JUNO 20-inch PMTs

Background: The Jiangmen underground neutrino observatory (JUNO) is a new generation of long-term operation neutrino experimental platform under construction in Jiangmen, Guangdong province of southern China. The underwater frontend and readout electronics (F&R electronics) are placed nearby the 20-inch PMTs and readout current signals from three PMTs. The electronics are sealed in a stainless-steel underwater box to keep them dry, and temperature control of the electronics plays a significant role in their reliability. Methods: A conductive cooling structure based on the passive cooling method is designed for the 20-inch PMT F&R electronics. Both numerical simulation and experimental tests were performed to evaluate the cooling structures' thermal performance. Results: The results show that the case temperature of the respective chip for 20-inch PMT F&R electronics is less than 30 ℃ in ambient still water. Conclusion: The case temperature of the respective chip meets the strict temperature requirement for the F&R electronics. The JUNO collaboration has adopted this cooling structure for the 20-inch PMT readout electronics.