Time and date: February 7, 2008 (Thursday), 3:30 P.M.
Venue: Seminar Hall
Title: How to attain temperatures below 1 K and down to < 1 mK and superfluidity in 3He
Speaker: Prof. R.G. Sharma, Nuclear Science Centre (IUAC), New Delhi
Abstract: Attaining temperatures closer and closer to absolute zero had been a passion with physicists ever since Kammerlingh Onnes succeeded in liquefying helium in 1908. The long search for superfluidity in the rare isotope of helium that is 3He led to a number of technological advancements for attaining low temperatures. I will talk about the 4He evaporator going down to 0.8 K, the 3He evaporator going down to 0.3 K for carrying out studies. Anomalous phase diagram of 3He and 4He mixture will be discussed and how the dilution refrigerator became a routine technique to obtain temperatures down to 10 mK in the laboratory. Finally, I will talk about the nuclear demagnetisation experiment whereby 3He has been refrigerated to below 1 mK and can be maintained for long durations for detailed experiments. Some peculiar properties of 3He and 4He superfluids will be discussed.