The first pulse-tube pre-cooled dilution units were developed simultaneously in Japan, Germany and France in the late 90's, in research and industrial environments, when efficient pulse-tube cryocoolers became available.
A 41 mK hybrid refrigerator (Gifford - McMahon and pulse-tube) was built very early in Japan. The pulse-tube was used as 4K stage, making this machine a genuine pulse-tube based dilution unit. The performance was poor, however, due to the Gifford - McMahon high temperature stage.
Kurt Uhlig, in Garching, developed several machines of increasing performance. The first refrigerator reached 15 mK with a continuous heat exchanger (2002). A new model with a double mixing-chamber reached 4.3 mK (2004). A different machine with step heat exchangers allowed reaching T<10 mK (2012):
A commercial pulse-tube dilution refrigerator was developed in 1999 in Grenoble (France) by H. Godfrin and Ch. Gianèse (CNRS) and the company l'Air Liquide. The first commercial machine (PT-DR1, picture on the right) was delivered to A. Giuliani (Cuoricino experiment) in 2003. With 4 sintered silver heat exchangers, the refrigerator had a base temperature of 5 mK. Because of patents and industrial know-how agreements, details were published later:
The cryostats PT-DR1 (industrial version version delivered in 2003), PT-DR2 (2007, version presented at the Industrial Exhibition of LT25, Amsterdam, 2008), and PT-DR4 (Pulse-tube dilution for neutron scattering, 2021 version shown):