====== Precooling issues: 1K pot, or no 1K pot? ======

===== The continuous "1K pot" =====
  * Continuously operating 4He evaporation refrigerator. Rev Sci Instrum (1971);42:147–50.  https://doi.org/10.1063/1.1684846
  * Low dead time 1 K cryostat, J.Talpe and V.Bekeris, Cryogenics 29, 854-856 (1989). https://doi.org/10.1016/0011-2275(89)90161-6
  * Design and performance of a 4He-evaporator at <1.0 K, N.K. Das ⇑, J. Pradhan, Md.Z.A. Naser, A. Roy, B.Ch. Mandal, C. Mallik, R.K. Bhandari, Cryogenics 52 (2012) 679–684, https://doi.org/10.1016/j.cryogenics.2012.04.013


===== The "1K loop" in pulse-tube based dilution refrigerators =====
  * Dry dilution refrigerator with 4He-1K-loop, K. Uhlig, Cryogenics 66, 2015, 6-12. https://doi.org/10.1016/j.cryogenics.2014.10.004

===== Condensing the 3He at high pressure  =====

{{ condensing3he.jpg?400 |Condensing 3He}}
At 4.2 K the minimum enthalpy (vs. Pressure) is Hm ≈ 42 J/mol near 3 bars, just above the enthalpy of the vapor at 0.7 K (35 J/mol). Steady state is possible using a heat exchanger to precool the incoming 3He:
  * J. Kraus, Cryogenics 17, 173 (1977) [[https://doi.org/10.1016/0011-2275(77)90279-X]] 
  * A.T.A.M. de Waele, A.B. Reekers, H.M. Gijsman, Cryogenics 17, 175 (1977) [[https://doi.org/10.1016/0011-2275(77)90280-6]]