Multi-cryostat dilution refrigerator

Abstract

A dilution refrigerator and a method for operating same as described. The dilution refrigerator comprising a plurality of cryostats each comprising a plurality of temperature-controlled flanges inside a vacuum chamber, the temperature-controlled flanges cooled to progressively lower temperatures. Dilution units are disposed inside each of the cryostats and operable to cool at least a subset of the temperature-controlled flanges. A gas handling system is fluidly coupled to the plurality of cryostats and comprises a flow circuit and flow control devices interconnecting a gas mixture reservoir with the dilution units. A controller is coupled to the gas handling system and configured for operating the flow control devices in accordance with a sequence of operations that open and close paths in the flow circuit that allow a gas mixture to circulate between the gas mixture reservoir and the dilution units.

1 . A dilution refrigerator comprising:
 a plurality of cryostats each comprising a plurality of temperature-controlled flanges inside a vacuum chamber, the temperature-controlled flanges cooled to progressively lower temperatures;   dilution units disposed inside each of the cryostats and operable to cool at least a subset of the temperature-controlled flanges;   a gas handling system fluidly coupled to the plurality of cryostats, the gas handling system comprising a flow circuit and flow control devices interconnecting a gas mixture reservoir with the dilution units; and   a controller coupled to the gas handling system and configured for operating the flow control devices in accordance with a sequence of operations that open and close paths in the flow circuit that allow a gas mixture to circulate between the gas mixture reservoir and the dilution units.   
     
     
         2 . The dilution refrigerator of  claim 1 , wherein the gas handling system comprises a vacuum generator having a first pumping arrangement operable to apply a vacuum to each said vacuum chamber for evacuation thereof. 
     
     
         3 . The dilution refrigerator of  claim 2 , wherein the first pumping arrangement comprises an evacuation valve per cryostat, coupled to a respective one of the vacuum chambers, and a first set of pumps configured for evacuating the cryostats via a respective evacuation valve. 
     
     
         4 . The dilution refrigerator of  claim 1 , wherein the flow control devices comprise:
 a second pumping arrangement;   a first set of valves coupled between the gas mixture reservoir and the second pumping arrangement; and   a second set of valves coupled between the second pumping arrangement and the dilution units of the cryostats.   
     
     
         5 . The dilution refrigerator of  claim 4 , wherein the second pumping arrangement comprises a high vacuum pump, a backing pump, and a condensing pump. 
     
     
         6 . The dilution refrigerator of  claim 5 , wherein the condensing pump is isolated from a main circulation loop of the flow circuit by isolation valves. 
     
     
         7 . The dilution refrigerator of  claim 4 , wherein the first set of valves comprises at least one mixture supply valve and at least one mixture storing valve operable to regulate flow in and out of the mixture reservoir, and wherein the second set of valves comprises at least one inflow valve per cryostat and at least one outflow valve per cryostat operable to regulate flow in and out of the dilution units. 
     
     
         8 . The dilution refrigerator of  claim 1 , wherein the flow circuit and flow control devices define, for each cryostat, paths comprising:
 a mixture storing path;   a mixture admission path; and   a mixture circulating path.   
     
     
         9 . The dilution refrigerator of  claim 8 , wherein at least two of the paths share at least one of the flow control devices. 
     
     
         10 . The dilution refrigerator of  claim 9 , wherein all of the paths share at least one of the flow control devices. 
     
     
         11 . A method for operating a dilution refrigerator having a plurality of cryostats each comprising a vacuum chamber and a dilution unit disposed therein, the method comprising:
 receiving a request to transition the dilution refrigerator from a first operating state to a second operating state;   determining, in accordance with the request, a sequence of operations for flow control devices in a flow circuit of a gas handling system of the dilution refrigerator, the flow circuit interconnecting a gas mixture reservoir with the dilution units of the cryostats; and   operating the flow control devices in accordance with the sequence of operations that open and close paths in the flow circuit that allow a gas mixture to circulate between the gas mixture reservoir and the dilution units.   
     
     
         12 . The method of  claim 11 , wherein the first operating state comprises having at least a first one of the cryostats online, and the second operating state comprises having at least a second one of the cryostats online. 
     
     
         13 . The method of  claim 11 , wherein the request comprises taking at least one of the cryostats offline. 
     
     
         14 . The method of  claim 11 , wherein the request comprises bringing at least one of the cryostats online. 
     
     
         15 . The method of  claim 11 , wherein determining the sequence of operations comprises determining a current operating state of all the cryostats and a requested operating state of all of the cryostats. 
     
     
         16 . The method of  claim 15 , wherein determining the sequence of operations comprises retrieving the sequence of operations from a storage medium based on the current operating state of the cryostats and the requested operating state of the cryostats. 
     
     
         17 . The method of  claim 11 , wherein determining the sequence of operations comprises selecting from a list of a mixture storing path, a mixture admission path, and a mixture circulating path associated with each one of the cryostats. 
     
     
         18 . The method of  claim 11 , further comprising determining that the request requires bringing at least one of the cryostats from an offline status to an online status, and applying a vacuum to the vacuum chamber of the at least one of the cryostats. 
     
     
         19 . A non-transitory computer-readable medium having stored thereon program code executable by a machine for operating a dilution refrigerator having a plurality of cryostats each comprising a vacuum chamber and a dilution unit disposed therein, the program code executable for:
 receiving a request to transition the dilution refrigerator from a first operating state to a second operating state;   determining, in accordance with the request, a sequence of operations for flow control devices in a flow circuit of a gas handling system of the dilution refrigerator, the flow circuit interconnecting a gas mixture reservoir with the dilution units of the cryostats; and   operating the flow control devices in accordance with the sequence of operations that open and close paths in the flow circuit that allow a gas mixture to circulate between the gas mixture reservoir and the dilution units.   
     
     
         20 . The non-transitory computer-readable medium of  claim 19 , wherein the program code is further executable for determining that the request requires bringing at least one of the cryostats from an offline status to an online status, and applying a vacuum to the vacuum chamber of the at least one of the cryostats.