Cryogenic cooling system

A cryogenic cooling system comprising:

• a) a cryocooler coldhead having a first stage;
• and
• b) a coolant circuit containing a gaseous cryogen and including:
• 1) a gas circulator having a low pressure input orifice and a high pressure output orifice;
• 2) a valve having:
• (a) a high pressure port in fluid communication with said high pressure output orifice of said gas circulator;
• (b) a low pressure port in fluid communication with said low pressure input orifice of said gas circulator;
• (c) a primary port;
• (d) a secondary port;
• and
• (e) means for making and switching fluid connections of said high and low pressure ports each to a corresponding one of said primary and secondary ports;
• 3) a first heat exchanger having a primary portion and a secondary portion each in thermal contact with said first stage of said cryocooler coldhead;
• 4) a first primary regenerator in fluid communication with and disposed fluidly between said primary port of said valve and said primary portion of said first heat exchanger;
• 5) a first secondary regenerator in fluid communication with and disposed fluidly between said secondary port of said valve and said secondary portion of said first heat exchanger;
• and
• 6) a first coolant flow path distinct from said valve, having a first end in fluid communication with said primary portion of said first heat exchanger, and having a second end in fluid communication with said secondary portion of said first heat exchanger.