10 valves 90 92 94 96 control the flow of fluid immediately going to the pump 42 and immediately coming from the 77k heat exchanger 46 second fluid which may be gaseous hydrogen helium or neon is shown coming from outside cold box 24 and entering through second fluid fill port 48 and going to 77k heat exchanger 46 after passing through 77k heat exchanger 46 the second fluid travels via heat exchanger connecting pipe segment 49 to main heat exchanger 50 where the second fluid is turned into a desired product such as liquid hydrogen slush hydrogen a mixture of liquid and solid hydrogen liquid neon or cooled helium gas the desired product is then conveyed to liquid reservoir 52 by drain pipe 98 the desired product can be removed from liquid reservoir 52 by outlet pipe 100 also shown in fig1 arbitrarily starting the circuit description for the fluid as it emerges from the pump 42 and the fluid is at 85k the fluid enters 77k heat exchanger 46 which is cooled by liquid nitrogen at 77k the liquid nitrogen enters cold box 24 via liquid nitrogen fill port 41 and the vaporized nitrogen leaves via vent port 44 the liquid nitrogen bath could be replaced by another refrigerator cold stage the fluid leaves the 77k heat exchanger 46 at 77k and flows through first.