History of Ultra-Low Temperatures in Dubna from 1966 to 2023

A frozen spin polarized targets cooled by the 3He/4He dilution refrigerator developed at the JINR, Dubna is described. In polarized targets of this type, dynamic polarization of target nuclei has to be a continuous process to support the achieved level of polarization, since polarization relaxation processes at temperatures of about 1 K are quite intensive. Experience with continuously-polarized targets (dynamic mode) and achieving of very low temperatures in 1966 (JINR) gave rise to the idea of using radically new technique based on dissolving 3He in 4He to the frozen spin polarized target. The short history (1966-2023) of the development of such proton and deuteron targets at JINR for different accelerators (Dubna, Protvino, Gatchina, Prague, Mainz and Bonn) is given. Currently, our group is considering the possibility of participating in such experiments.