We claim: 1. A miniature refrigeration system, comprising: a compressor for pressurizing a gas mixture to a pressure of approximately 420 psia, said compressor having an inlet and an outlet; a hollow elongated supply tube, said supply tube having a proximal end and a distal end, said proximal end of said supply tube being connectable to said outlet of said compressor; a hollow elongated return tube disposable substantially coaxially over said supply tube, said return tube having a proximal end and a distal end, said proximal end of said return tube being connectable to said inlet of said compressor; a laminated counterflow heat exchanger mounted within said return tube, adjacent to said distal end of said return tube, said heat exchanger having a high pressure passageway and a low pressure passageway, said high pressure passageway having at least one proximal port and at least one distal port, said at least one proximal port of said high pressure passageway being connected to said distal end of said supply tube, said low pressure passageway having at least one distal port and at least one proximal port, said at least one proximal port of said low pressure passageway being connected with a lumen of said return tubes, said high pressure passageway and said low pressure passageway each following a respective tortuous flow path with a substantial portion of each said flow path being transverse to a longitudinal axis of said heat exchanger, to create turbulent flow; a Joule-Thomson expansion element mounted within said return tube, said expansion element being connected to said distal port of said high pressure passageway of said heat exchanger for isenthalpically expanding said gas mixture from said higher pressure to a lower pressure, said expanded gas mixture thereby cooling to a temperature of no greater than 183K, said expanded gas mixture being in fluid flow communication with said at least one distal port of said low pressure passageway; and a heat transfer body mounted to said distal end of said return tube adjacent said expansion element, said body having an inner surface exposed to said expanded gas mixture and an outer surface exposed to ambient, for transferring heat from said outer surface of said body to said inner surface of said body. 2. A miniature refrigeration system, comprising: a compressor for pressurizing a gas mixture to a pressure of approximately 420 psia, said compressor having an inlet and an outlet; a hollow elongated supply tube, said supply tube having a proximal end and a distal end, said proximal end of said supply tube being connectable to said outlet of said compressor; a hollow elongated return tube disposable substantially coaxially over said supply tube, said return tube having a proximal end and a distal end, said proximal end of said return tube being connectable to said inlet of said compressor; a laminated counterflow heat exchanger mounted within said return tube, adjacent to said distal end of said return tube, said heat exchanger having a high pressure passageway and a low pressure passageway, said high pressure passageway having at least one proximal port and at least one distal port, said at least one proximal port of said high pressure passageway being connected to said distal end of said supply tube, said low pressure passageway having at least one distal port and at least one proximal port, said at least one proximal port of said low pressure passageway being connected with a lumen of said return tube; a Joule-Thomson expansion element mounted within said return tube, said expansion element being connected to said distal port of said high pressure passageway of said heat exchanger for isenthalpically expanding said gas mixture from said higher pressure to a lower pressure, said expanded gas mixture thereby cooling to a temperature of no greater than 183K, said expanded gas mixture being in fluid flow communication with said at least one distal port of said low pressure passageway; and a heat transfer body mounted to said distal end of said return tube adjacent said expansion element, said body having an inner surface exposed to said expanded gas mixture and an outer surface exposed to ambient, for transferring heat from said outer surface of said body to said inner surface of said body; wherein said expansion element comprises: a substantially cylindrical metallic container open at both ends; and a plurality of microscopic metallic beads sintered into the interior of said metallic container to form a permeable flow impedance. 3. A miniature refrigeration system, comprising: a compressor for pressurizing a gas mixture to a pressure of approximately 420 psia, said compressor having an inlet and an outlet; a hollow elongated supply tube, said supply tube having a proximal end and a distal end, said proximal end of said supply tube being connectable to said outlet of said compressor; a hollow elongated return tube disposable substantially coaxially over said supply tube, said return tube having a proximal end and a distal end, said proximal end of said return tube being connectable to said inlet of said compressor; a laminated counterflow heat exchanger mounted within said return tube, adjacent to said distal end of said return tube, said heat exchanger having a high pressure passageway and a low pressure passageway, said high pressure passageway having at least one proximal port and at least one distal port, said at least one proximal port of said high pressure passageway being connected to said distal end of said supply tube, said low pressure passageway having at least one distal port and at least one proximal port, said at least one proximal port of said low pressure passageway being connected with a lumen of said return tube; a Joule-Thomson expansion element mounted within said return tube, said expansion element being connected to said distal port of said high pressure passageway of said heat exchanger for isenthalpically expanding said gas mixture from said higher pressure to a lower pressure, said expanded gas mixture thereby cooling to a temperature of no greater than 183K, said expanded gas mixture being in fluid flow communication with said at least one distal port of said low pressure passageway; and a heat transfer body mounted to said distal end of said return tube adjacent said expansion element, said body having an inner surface exposed to said expanded gas mixture and an outer surface exposed to ambient, for transferring heat from said outer surface of said body to said inner surface of said body; wherein said expansion element comprises: a first substantially cylindrical metallic container having a first diameter, said first container being open at both ends; a first plurality of microscopic metallic beads sintered into the interior of said first container to form a first permeable flow impedance, said first plurality of beads being sized to expand said gas mixture isenthalpically; a second substantially cylindrical metallic container having a second diameter greater than said first diameter, said second container being open at both ends; and a second plurality of microscopic metallic beads sintered into the interior of said second container to form a second permeable flow impedance, said second plurality of metallic beads being sized to expand said gas mixture isothermally. 4. A miniature refrigeration system, comprising: a compressor for pressurizing a gas mixture to a pressure of approximately 420 psia, said compressor having an inlet and an outlet; a hollow elongated supply tube, said supply tube having a proximal end and a distal end, said proximal end of said supply tube being connectable to said outlet of said compressor; a hollow elongated return tube disposable substantially coaxially over said supply tube, said return tube having a proximal end and a distal end, said proximal end of said return tube being connectable to said inlet of said compressor; a laminated counterflow heat exchanger mounted within said return tube, adjacent to said distal end of said return tube, said heat exchanger having a high pressure passageway and a low pressure passageway, said high pressure passageway having at least one proximal port and at least one distal port, said at least one proximal port of said high pressure passageway being connected to said distal end of said supply tube, said low pressure passageway having at least one distal port and at least one proximal port, said at least one proximal port of said low pressure passageway being connected with a lumen of said return tube; a Joule-Thomson expansion element mounted within said return tube, said expansion element being connected to said distal port of said high pressure passageway of said heat exchanger for isenthalpically expanding said gas mixture from said higher pressure to a lower pressure, said expanded gas mixture thereby cooling to a temperature of no greater than 183K, said expanded gas mixture being in fluid flow communication with said at least one distal port of said low pressure passageway; and a heat transfer body mounted to said distal end of said return tube adjacent said expansion element, said body having an inner surface exposed to said expanded gas mixture and an outer surface exposed to ambient, for transferring heat from said outer surface of said body to said inner surface of said body; wherein said heat exchanger comprises a plurality of laminated members, said laminated members being constructed and arranged to establish said high pressure passageway and said low pressure passageway; and wherein said laminated members comprise: a plurality of flat plates and a plurality of flat spacers stacked axially along said heat exchanger, said plates being alternated with said spacers; a first plurality of openings formed through said plates and said spacers to establish said high pressure passageway, with said proximal high pressure port at a proximal end of said stack and said distal high pressure port at a distal end of said stack, said first plurality of openings in each said plate being transversely offset from said first plurality of openings in adjacent said plates, to create a tortuous high pressure flow path with a substantial portion of said high pressure flow path being transverse to a longitudinal axis of said heat exchanger to create turbulent high pressure flow; and a second plurality of openings formed through said plates and said spacers to establish said low pressure passageway, with said proximal low pressure port at said proximal end of said stack and said distal low pressure port at said distal end of said stack, said second plurality of openings in each said plate being transversely offset from said second plurality of openings in adjacent said plates, to create a tortuous low pressure flow path with a substantial portion of said low pressure flow path being transverse to a longitudinal axis of said heat exchanger to create turbulent low pressure flow. 5. A miniature refrigeration system, comprising; a compressor for pressurizing a gas mixture to a pressure of approximately 420 psia, said compressor having an inlet and an outlet; a hollow elongated supply tube, said supply tube having a proximal end and a distal end, said proximal end of said supply tube being connectable to said outlet of said compressor; a hollow elongated return tube disposable substantially coaxially over said supply tube, said return tube having a proximal end and a distal end, said proximal end of said return tube being connectable to said inlet of said compressor; a laminated counterflow heat exchanger mounted within said return tube, adjacent to said distal end of said return tube, said heat exchanger having a high pressure passageway and a low pressure passageway, said high pressure passageway having at least one proximal port and at least one distal port said at least one proximal port of said high pressure passageway being connected to said distal end of said supply tube, said low pressure passageway having at least one distal port and at least one proximal port, said at least one proximal port of said low pressure passageway being connected with a lumen of said return tube; a Joule-Thomson expansion element mounted within said return tube, said expansion element being connected to said distal port of said high pressure passageway of said heat exchanger for isenthalpically expanding said gas mixture from said higher pressure to a lower pressure said expanded gas mixture thereby cooling to a temperature of no greater than 183K, said expanded gas mixture being in fluid flow communication with said at least one distal port of said low pressure passageway; and a heat transfer body mounted to said distal end of said return tube adjacent said expansion element, said body having an inner surface exposed to said expanded gas mixture and an outer surface exposed to ambient, for transferring heat from said outer surface of said body to said inner surface of said body; wherein said heat exchanger comprises a plurality of laminated members, said laminated members being constructed and arranged to establish said high pressure passageway and said low pressure passageway; and wherein said laminated members comprise: a first sheet having a first flow channel etched therein to form said high pressure passageway, with said proximal high pressure port at a proximal edge of said first sheet and said distal high pressure port at a distal edge of said first sheet; and a second sheet having a second flow channel etched therein to form said low pressure passageway, with said proximal low pressure port at a proximal edge of said second sheet and said distal low pressure port at a distal edge of said second sheet; wherein said first and second sheets are rolled into a cylindrical shape having said proximal ports at a proximal end and said distal ports at a distal end. 6. A miniature refrigeration system, comprising: a compressor for pressurizing a gas mixture to a pressure of approximately 420 psia, said compressor having an inlet and an outlet; a hollow elongated gas mixture supply tube, said supply tube having a proximal end and a distal end, said proximal end of said supply tube being connectable to said outlet of said compressor; a hollow elongated gas mixture return tube disposable substantially coaxially over said supply tube, said return tube having a proximal end and a distal end, said proximal end of said return tube being connectable to said inlet of said compressor; a substantially cylindrical counterflow heat exchanger mounted within said return tube, adjacent to said distal end of said return tube, said heat exchanger comprising a plurality of laminated members, each of said laminated members having a first plurality of openings transversely offset from openings in adjacent said laminated members, establishing a first tortuous path for said supply gas mixture with a substantial portion of said first tortuous path being transverse to a longitudinal axis of said heat exchanger to create turbulent high pressure flow, and each of said laminated members having a second plurality of openings transversely offset from openings in adjacent said laminated members, establishing a second tortuous path for said return gas mixture with a substantial portion of said second tortuous path being transverse to a longitudinal axis of said heat exchanger to create turbulent low pressure flow, said supply path having at least one proximal port and at least one distal port, said at least one proximal port of said supply path being connected to said distal end of said supply tube, said return path having at least one distal port and at least one proximal port, said at least one proximal port of said return path being connected with a lumen of said return tube; a Joule-Thomson two stage expansion element mountable within said return tube, said expansion element having an inlet connected to said distal port of said supply path of said heat exchanger, said expansion element having an outlet for releasing said gas mixture to enter said distal port of said return path of said heat exchanger adjacent said distal end of said return tube; a first, isenthalpic, expansion stage in said expansion element for expanding said gas mixture from said supply pressure to a lower pressure, said expanded gas mixture thereby cooling to a temperature of no greater than 183K to allow said expanded gas mixture to absorb heat from surrounding components; a second, isothermal, expansion stage in said expansion element, downstream of said first stage, for further expanding said gas mixture to absorb additional heat from surrounding components; and a metallic heat transfer element sealingly mounted through an aperture in a wall of said return tube adjacent said expansion element, said heat transfer element having an inner surface exposed to said twice expanded gas mixture and an outer surface exposed to ambient, for transferring heat from ambient to said gas mixture. 7. A method for cooling a remote body, comprising the steps of: providing a gas mixture capable of isenthalpically expanding to a temperature below 183K from a pressure of no more than 420 psia; providing a miniature refrigeration system having a compressor for pressurizing said gas mixture to a pressure of no more than 420 psia, a supply tube having an inlet end connected to an outlet of said compressor, and a return tube disposed coaxially over said supply tube and having an outlet connected to an inlet of said compressor; providing a laminate construction counterflow heat exchanger within a distal section of said return tube, said heat exchanger having a high pressure section and a low pressure section, said high pressure section having an inlet connected to an outlet of said supply tube and said low pressure section having an outlet connected to an inlet of said return tube said high pressure section and said low pressure section each following a respective tortuous flow path with a substantial portion of each said flow path being transverse to a longitudinal axis of said heat exchanger, to create turbulent flow; providing a two stage Joule-Thomson expansion element having an inlet connected to an outlet of said high pressure section of said heat exchanger and having an outlet adjacent to a metallic heat transfer element and adjacent to an inlet of said low pressure section of said heat exchanger; placing said heat transfer element in contact with said remote body to be cooled; compressing said gas mixture to no more than 420 psia; conducting said compressed gas mixture to said high pressure inlet of said heat exchanger via said supply tube; precooling said compressed gas mixture via turbulent gas flow in said high pressure section of said heat exchanger by transferring heat to turbulent gas flow in said low pressure section of said heat exchanger; isenthalpically expanding said gas mixture in a first stage of said expansion element to cool said gas mixture to below 183K, allowing said expanded gas mixture to absorb heat from surrounding components; isothermally expanding said gas mixture in a second stage of said expansion element, allowing said further expanded gas mixture to absorb additional heat from surrounding components; absorbing heat from said heat transfer element by contact with said further expanded gas mixture, to cool said heat transfer element to below 180K; and absorbing heat from said item to be cooled, by contact with said heat transfer element.