Control system for actively cooled cryogenic biological preservation unit

Abstract

A control system for an actively cooled cryogenic biological preservation unit wherein vapor flow into or out of the unit or a proxy thereof is sensed by a flow sensor signaling a controller which modulates cryocooler refrigeration into the unit.

1 . An actively cooled cryogenic biological preservation unit comprising: 
 (A) an insulated vessel having a vessel interior, and a cryocooler positioned to provide refrigeration to the insulated container;    (B) an exhaust line in communication with the vessel interior, and a flow sensor on the exhaust line; and    (C) a controller, means for passing a signal from the flow sensor to the controller, and means for passing a signal from the controller to the cryocooler.    
   
   
       2 . The actively cooled cryogenic biological preservation unit of  claim 1  wherein the cryocooler is a pulse tube refrigerator.  
   
   
       3 . The actively cooled cryogenic biological preservation unit of  claim 1  containing at least one biological sample within the vessel interior.  
   
   
       4 . The actively cooled cryogenic biological preservation unit of  claim 1  wherein the controller is a proportional integral derivative controller.  
   
   
       5 . The actively cooled cryogenic biological preservation unit of  claim 1  further comprising a heater, and means for passing a signal from the controller to the heater.  
   
   
       6 . The actively cooled cryogenic biological preservation unit of  claim 5  further comprising a second controller, and wherein the means for passing a signal from the controller to the cryocooler includes the second controller.  
   
   
       7 . A method for operating an actively cooled cryogenic biological preservation unit comprising: 
 (A) providing refrigeration to the interior of an insulated vessel having an exhaust line in communication with the vessel interior;    (B) sensing the flow of gas within the exhaust line; and    (C) adjusting the amount of refrigeration provided to the vessel interior based on the gas flow sensing.    
   
   
       8 . The method of  claim 7  wherein refrigeration is provided to the vessel interior from a cryocooler.  
   
   
       9 . The method of  claim 7  wherein the gas flow sensing senses gas flowing away from the vessel interior, and the refrigeration adjustment comprises increasing the amount of refrigeration provided to the vessel interior.  
   
   
       10 . The method of  claim 7  wherein the gas flow sensing senses gas flowing toward the vessel interior, and the refrigeration adjustment comprises decreasing the amount of refrigeration provided to the vessel interior.  
   
   
       11 . The method of  claim 7  wherein the gas flow sensing senses gas flowing toward the vessel interior, and the refrigeration adjustment comprises providing heat to the vessel interior.  
   
   
       12 . The method of  claim 11  wherein the refrigeration adjustment further comprises decreasing the amount of refrigeration provided to the vessel interior.