Refrigerator, and Method for Producing Very Low Temperature Cold

Abstract

The invention relates to a method for producing very low temperature cold through a dilution cycle wherein a two-phase mixture of the two isotopes 3 He and 4 He is created in a mixing chamber from liquid 3 He and 4 He added separately, wherein said mixture of the 3 He from a so-called concentrated phase is extracted so as to pass 3 He into a so-called diluted phase, and due to which the cold energy generated by passing the 3 He into the diluted phase is recovered, the phase separation of the two-phase mixture being carried out by monitoring the flows of pure 3 He and 4 He, added separately into the mixing chamber, and by gravity-independent capillary forces, the dilution cycle operating in a closed loop, the method including a first step of recovering and separating the two isotopes 3 He and 4 He from the fraction of the mixture extracted through a discharge duct; and a second step of adding the two isotopes 3 He and 4 He, separated during the first step, back into the mixing chamber. The invention also relates to a refrigerator.

1 - 16 . (canceled) 
     
     
         17 . A dilution refrigerator for obtaining very low temperatures comprising:
 a mixing chamber;   a first feed pipe having an upstream end connected to a source of helium isotope 3 ( 3 He) and a downstream end connected to the mixing chamber, a second feed pipe having an upstream end connected to a source of helium isotope 4 ( 4 He) and a downstream end connected to the mixing chamber;   a discharge pipe for discharging the mixture of  3 He- 4 He produced in the mixing chamber from the  3 He and the  4 He supplied respectively by the first and second pipes, the discharge pipe comprising an upstream end connected to the mixing chamber and a downstream end connected to a collecting volume for recovering the fraction of the discharged mixture, the downstream ends of the first and second pipes and the upstream end of the discharge pipe communicating fluidically at a common junction so as to form the mixing chamber, the phase separation between the mixtures of helium  3 He- 4 He being controlled by the flows of  3 He and  4 He in the pipes and the capillary forces in the pipes independently of gravity; and   a still constituting the collecting volume in which the mixture is recovered, the still keeping the mixture of the  3 He and  4 He at liquid-vapor equilibrium, the still forming both the source of  3 He and the source of  4 He, the first feed pipe comprising a pumping member adapted to selectively pump  3 He into the still in order to feed the mixing chamber with  3 He continuously and in a first closed loop, the second feed pipe comprising a pumping member adapted to selectively pump  4 He into the still in order to feed the mixing chamber with  4 He continuously and in a distinct second closed loop.   
     
     
         18 . The refrigerator of  claim 17 , wherein the still comprises a member for the containment of the liquid phase with respect to the gaseous phase. 
     
     
         19 . The refrigerator of  claim 18 , wherein the pumping member adapted to selectively pump the  4 He comprises a superleak in fluidic communication with the liquid phase contained by the containment member and a pump the intake of which is connected to the liquid phase via the superleak. 
     
     
         20 . The refrigerator of  claim 17 , wherein the first and second pipes and the discharge pipe are assembled in order to exchange heat between the still and the mixing box. 
     
     
         21 . The refrigerator of  claim 17 , wherein the pumping member of the first feed pipe is a pump for pumping gaseous  3 He selected from the group consisting of a mechanical pump, one or more adsorption pumps, and combinations thereof. 
     
     
         22 . The refrigerator of  claim 17 , wherein the upstream end of the first feed pipe and/or the pumping member of the first feed pipe opens into a zone of the still that collects predominantly  3 He from the  3 He- 4 He mixture at liquid-vapor equilibrium. 
     
     
         23 . The refrigerator of  claim 17 , wherein the pumping member of the second feed pipe is a pump for pumping liquid  4 He selected from the group consisting of a mechanical pump, a thermo-mechanical pump, a superfluid helium mechanical pump, and combinations thereof. 
     
     
         24 . The refrigerator of  claim 17 , wherein the upstream end of the second feed pipe and/or the pumping member of the second feed pipe opens into a zone of the still that collects predominantly  4 He from the  3 He- 4 He mixture at liquid-vapor equilibrium. 
     
     
         25 . The refrigerator of  claim 23 , wherein the pumping member of the second feed pipe or the upstream end of the second feed pipe opens into a zone of the still via an element for selective filtration of  4 He. 
     
     
         26 . A method for producing cold at very low temperature, using a dilution cycle in which a diphasic mixture of the two isotopes  3 He and  4 He is created in a mixing chamber from liquid  3 He and liquid  4 He which are introduced separately via respective feed pipes, in which method  3 He from a phase known as the concentrated phase is extracted from said mixture, via a discharge pipe, in order to cause the  3 He to enter a phase known as the dilute phase, and by virtue of which the cold energy generated by the  3 He entering the dilute phase is recovered; the phases of the diphasic mixture being separated by controlling the flows of pure  3 He and  4 He introduced separately into the mixing chamber and the capillary forces in the pipes independently of gravity, characterized in that the dilution cycle operates in a closed loop, the method comprising the steps of:
 recovering and separating the two isotopes  3 He and  4 He from the fraction of mixture extracted by a discharge pipe; and   re-introducing the two isotopes  3 He and  4 He separated during the first step into the mixing chamber.   
     
     
         27 . The method of  claim 26 , wherein said step of recovering and separating the two isotopes is carried out in a still configured to keep the  3 He- 4 He mixture at liquid-vapor equilibrium. 
     
     
         28 . The method of  claim 26 , wherein said step of re-introducing the two  3 He and  4 He isotopes into the mixing chamber is performed using respective pumping members. 
     
     
         29 . The method of  claim 26 , wherein the mixture of the two isotopes  3 He and  4 He is kept in the mixing chamber at a temperature between 10 mK and 300 mK. 
     
     
         30 . The method of  claim 26 , wherein a pumping pressure of the pumping member of the first pipe is between 0.1 and 50 mb. 
     
     
         31 . The method of  claim 26 , further comprising, between said step of recovery and separation and said step of re-introduction, a step of respectively cooling one or each of the separated isotopes between 1 and 2K. 
     
     
         32 . The method of  claim 26 , wherein said method is performed to produce cold energy at a temperature below 2K. 
     
     
         33 . The method of  claim 26 , wherein said method is performed to produce cold energy at a temperature below 1K. 
     
     
         34 . The method of  claim 30 , wherein the pumping pressure of the pumping member of the first pipe is approximately equal to 5 mbar. 
     
     
         35 . The method of  claim 26 , further comprising, between said step of recovery and separation and said step of re-introduction, a step of respectively cooling one or each of the separated isotopes between 1.4 and 1.5K. 
     
     
         36 . The method of  claim 26 , wherein said method utilizes a dilution refrigerator comprising a mixing chamber, a first feed pipe having an upstream end connected to a source of helium isotope 3 ( 3 He) and a downstream end connected to the mixing chamber, a second feed pipe having an upstream end connected to a source of helium isotope 4 ( 4 He) and a downstream end connected to the mixing chamber, a discharge pipe for discharging a fraction of the mixture of  3 He- 4 He produced in the mixing chamber from the  3 He and the  4 He supplied respectively by the first and second pipes, the discharge pipe comprising an upstream end connected to the mixing chamber and a downstream end connected to a collecting volume for recovering the fraction of the discharged mixture, the downstream ends of the first and second pipes and the upstream end of the discharge pipe communicating fluidically at a common junction so as to form the mixing chamber, the phase separation between the mixtures of helium being controlled by the flows of  3 He and  4 He and the capillary forces in the pipes rather than by gravity, the refrigerator further comprising a still constituting the collecting volume in which the mixture is recovered, the still keeping the mixture of the  3 He and  4 He at liquid-vapor equilibrium, the still forming both the source of  3 He and the source of  4 He, the first feed pipe comprising a pumping member for selectively pumping  3 He into the still feeding the mixing chamber with  3 He continuously and in a first closed loop, the second feed pipe comprising a pumping member for selectively pumping  4 He into the still feeding the mixing chamber with  4 He continuously and in a second closed loop.