A cryogenic system for cooling an exterior surface of a cryoprobe shaft using nitrogen as a cryogen, the system comprising: a) a cryoprobe comprising: i) a cryoprobe shaft ii) a cryoprobe supply lumen, iii) a cryoprobe return lumen, and iv) a freeze zone in fluid communication with the cryoprobe supply lumen and the cryoprobe return lumen, the freeze zone having an interior surface in thermal communication with an external surface of the shaft; b) a dewar adapted to contain a liquid nitrogen bath, wherein the dewar includes a fill level that indicates a predetermined level that identifies the level in the dewar representing a full liquid nitrogen bath; c) at least one cryoengine, the cryoengine i) at least partially disposed within the dewar and positioned so about 40% to about 50% of the external surface area of the cryoengine is submerged within the liquid nitrogen bath in the dewar when the dewar contains a full liquid nitrogen bath, wherein the submersed external surface area of the cryoengine functions as a heat exchanger, and ii) capable of generating from a combination of liquid nitrogen and nitrogen vapor having a ratio of 0.75:1 to 1:0.75 liquid nitrogen to nitrogen gas, sub-cooled, pressurized nitrogen at a pressure of 6894.76 kPa or greater and a temperature of about -160°C or colder using one or more heat sources to pressurize the nitrogen, and heat exchange between the cryoengine and liquid nitrogen bath to sub-cool heat pressurized nitrogen in the cryoengine; d) a supply line through which sub-cooled, pressurized nitrogen is capable of flowing from the cryoengine to the freeze zone of the cryoprobe, and e) a valve, that when closed, prevents the flow of nitrogen from the cryoengine to the cryoprobe; wherein the system is adapted to provide continuous flow of sub-cooled, pressurized nitrogen from the cryoengine to the freeze zone of the cryoprobe at decreasing pressures starting at an initial pressure of about 6894.76 kPa or greater, and a temperature of about -160°C or colder and continuing to provide continuous flow of sub-cooled, pressurized nitrogen from the cryoengine to the freeze zone of the cryoprobe until the pressure of the sub-cooled, pressurized nitrogen flowing from the cryoengine to the freeze zone drops to between about 2757.90 kPa and 689.48 kPa, the temperature of the sub-cooled, pressurized nitrogen at the freezing zone being no warmer than about -158°C throughout the continuous flow of sub-cooled, pressurized nitrogen from the initial pressure of about 6894.76 kPa or greater to the final pressure of between about 2757.90 kPa and 689.48 kPa, the system is adapted to provide the pressurized nitrogen that is circulated from the cryoengine through the supply line, the supply lumen of the cryoprobe, the freeze zone of the cryoprobe and through the return lumen at a temperature that remains colder than the critical temperature of nitrogen. a) a cryoprobe comprising: i) a cryoprobe shaft ii) a cryoprobe supply lumen, iii) a cryoprobe return lumen, and iv) a freeze zone in fluid communication with the cryoprobe supply lumen and the cryoprobe return lumen, the freeze zone having an interior surface in thermal communication with an external surface of the shaft; i) a cryoprobe shaft ii) a cryoprobe supply lumen, iii) a cryoprobe return lumen, and iv) a freeze zone in fluid communication with the cryoprobe supply lumen and the cryoprobe return lumen, the freeze zone having an interior surface in thermal communication with an external surface of the shaft; b) a dewar adapted to contain a liquid nitrogen bath, wherein the dewar includes a fill level that indicates a predetermined level that identifies the level in the dewar representing a full liquid nitrogen bath; c) at least one cryoengine, the cryoengine i) at least partially disposed within the dewar and positioned so about 40% to about 50% of the external surface area of the cryoengine is submerged within the liquid nitrogen bath in the dewar when the dewar contains a full liquid nitrogen bath, wherein the submersed external surface area of the cryoengine functions as a heat exchanger, and ii) capable of generating from a combination of liquid nitrogen and nitrogen vapor having a ratio of 0.75:1 to 1:0.75 liquid nitrogen to nitrogen gas, sub-cooled, pressurized nitrogen at a pressure of 6894.76 kPa or greater and a temperature of about -160°C or colder using one or more heat sources to pressurize the nitrogen, and heat exchange between the cryoengine and liquid nitrogen bath to sub-cool heat pressurized nitrogen in the cryoengine; i) at least partially disposed within the dewar and positioned so about 40% to about 50% of the external surface area of the cryoengine is submerged within the liquid nitrogen bath in the dewar when the dewar contains a full liquid nitrogen bath, wherein the submersed external surface area of the cryoengine functions as a heat exchanger, and ii) capable of generating from a combination of liquid nitrogen and nitrogen vapor having a ratio of 0.75:1 to 1:0.75 liquid nitrogen to nitrogen gas, sub-cooled, pressurized nitrogen at a pressure of 6894.76 kPa or greater and a temperature of about -160°C or colder using one or more heat sources to pressurize the nitrogen, and heat exchange between the cryoengine and liquid nitrogen bath to sub-cool heat pressurized nitrogen in the cryoengine; d) a supply line through which sub-cooled, pressurized nitrogen is capable of flowing from the cryoengine to the freeze zone of the cryoprobe, and e) a valve, that when closed, prevents the flow of nitrogen from the cryoengine to the cryoprobe;