Expander in a pulsation tube cooling stage

Abstract

In an expander in a pulse tube cooling stage of a cooling system which pulse tube cooling stage comprises a pressure generator, a pulse tube cooling unit connected to the pressure generator and including a regenerator and a pulse tube with a heat exchanger arranged therebetween and a buffer volume in communication with the pulse tube and an expander arranged functionally between the pulse tube and the buffer volume, the expander includes capillary flow passages consisting of a material with high heat conductivity for dissipating heat from the gas flowing through the capillary flow passages.

What is claimed is:  
     
         1 . An expander in a pulse tube cooling stage in a cooling system, said pulse tube cooling stage comprising essentially a pressure generator, a pulse tube cooling unit connected to said pressure generator and including a regenerator ( 4 ), a pulse tube ( 6 ) with a heat exchanger ( 5 ) arranged therebetween and a buffer volume ( 21 ) in communication with said pulse tube ( 6 ) and an expander ( 20 ) arranged functionally between the pulse tube ( 6 ) and the buffer volume ( 21 ), said expander ( 20 ) including capillary flow passages in a material with high heat conductivity.  
     
     
         2 . An expander according to  claim 1 , wherein said expander comprises a plurality of capillary tubes of equal length and diameter.  
     
     
         3 . An expander according to  claim 1 , wherein said expander consists of a rod of a sintered, porous, heat-conductive material disposed in a gas and liquid tight housing.  
     
     
         4 . An expander according to  claim 1 , wherein said pressure generator includes an inlet and an outlet and is connected to said regenerator ( 4 ) by way of a line including a first branch ( 14 ) connected to the inlet and a second branch ( 15 ) connected to the outlet, each branch including a control valve ( 16   a ,  16   b ).  
     
     
         5 . An expander according to  claim 4 , wherein said buffer volume ( 21 ) includes a control volume which is separated from the buffer volume in a gas and liquid tight manner and which is non-compressible and by which the buffer volume is adjustable.  
     
     
         6 . An expander according to  claim 4 , wherein said expander ( 20 ) is disposed in a housing connected to a cooling circuit for cooling the expander ( 20 ).  
     
     
         7 . An expander according to  claim 5 , wherein said expander extends at least partially into said buffer volume  21  and the buffer volume walls consist of a material with high heat conductivity.  
     
     
         8 . An expander according to  claim 6 , wherein said buffer volume is connected to the pressure generator ( 2   a ) by way of a line ( 24 ) including a control valve ( 25 ).  
     
     
         9 . An expander according to  claim 1 , wherein said buffer volume wall is provided with surface increasing means of heat conductive material for dissipating heat from said buffer.