On May 22, 2007 Dr cooled down to 20mK and after 1 hour it warmed up! Signs of leak in IVC from gas handling system. DR was taken apart and leak from the same leaky heat exchanger pancake(the second from bottom) was confirmed(see the picture). The pancake was cleaned and soldered using UTP 570 flux and soldering wire.
DR pumped down and leak checked was ok(leak rate: 1E-8torr.lit/sec). On Jun 5 and 6 condensing was ok until the He3 Alcatel pump failed. The pump replaced with the Leybold He3 pump and system worked fine after.