The Cryogenics Laboratory at Ohio State University

[13] Soon after his arrival at Ohio State University in 1929 as an assistant professor of chemistry, Herrick L. Johnston (1898-1965) prepared plans for a cryogenics laboratory to match that of his preceptor, William F. Giauque of the University of California at Berkeley. This was ambitious planning, for Giauque's laboratory and one at the Bureau of Standards in Washington were among the very few in the country capable of research at the temperatures of liquid hydrogen. Giauque and Johnston had just published their revolutionary discovery that atmospheric oxygen contains atoms of mass 17 and 18, as well as 16, a discovery that set into motion a chain of experiments leading to the discovery of heavy hydrogen by Harold C. Urey in 1939 (appendix A-3).

Unfortunately for Johnston, his move to Ohio took him out of the mainstream of the swiftly moving research of low-temperature phenomena, and his dream of a cryogenics laboratory lay dormant a decade for lack of funding. In 1939, Johnston, a full professor and still pushing for his cryogenics laboratory, got a big break. The year before, William McPherson, a former head of the chemistry department, was called out of retirement to be acting president of the university. The first annual alumni development fund drive in 1939 included plans for a cryogenics laboratory and McPherson personally contributed the first $1000. This amount was augmented by $5000 from the university budget and Johnston was quick to start spending it. He ordered a hydrogen compressor and other equipment needed for a liquefier but soon encountered another obstacle-no space for the equipment. This problem was solved when federal funds-part of a plan to involve universities in war research-became available for a building. It was bluntly named the War Research Building. Johnston was initially allocated part of the first floor for a cryogenics laboratory, but later he took over the first two floors.⁴

Construction of the building began about mid-1942, but before the foundation and framework were completed, another crisis threatened to shatter Johnston's dreams for a laboratory. The government had decided to push forward the research necessary to build and test an atomic bomb. Part of the urgently needed research was for more information on hydrogen and deuterium as likely moderators. The university received word that its low-temperature equipment was needed elsewhere for war research, and Johnston was requested to set up and direct a cryogenics laboratory in the East. By some remarkably fast footwork and persuasion, university officials and Johnston managed to get the government to locate the cryogenics laboratory at Ohio State University. By mid-November, Johnston had a research contract.

Johnston worked best under pressure and short deadlines. He quickly recruited a staff including Gwynne A. Wright, an engineer who was to remain with him for 16 years, and Dr. Thor A. Rubin, a research chemist and another pupil of Giauque. Wright was placed in charge of installing the liquefier equipment. Typically, Johnston drove himself and his men hard. During December and most of January they worked [14] in overcoats, for the building was still under construction and without heat. On 2 February 1943, Johnston and Wright produced their first batch of liquid hydrogen (fig. 1) and Rubin lost no time in making use of it in an experiment.⁵

[15] By the end of his Manhattan Project research contract in 1946, Johnston had a fine cryogenics laboratory. Included were air, hydrogen, and helium liquefiers and other low-temperature equipment. He organized five sublaboratories-calorimetric, high pressure, spectroscopic, electrical and magnetic, and high temperature. The last, capable of reaching temperatures up to 2700 K, indicates that Johnston viewed a cryogenics laboratory in very broad terms.

The hydrogen system comprised five major components. Gaseous hydrogen was generated by electrolysis of water and the equipment was capable of producing 2 cubic meters per hour. The hydrogen was purified by a series of steps including heating to 570 K to remove oxygen, chilling to remove moisture, and use of a liquid-air trap to remove other condensable impurities. The third component was a three-stage compressor with an Output Of 1.7 cubic meters per minute at 300 atmospheres pressure. The hydrogen liquefier, a group of heat exchangers, was capable of 25 liters of hydrogen per hour. A large vacuum pump, capable of handling 5 cubic meters at a vacuum of 0.03 atmosphere, comprised the last component.

The hydrogen liquefier was modeled after the one developed by Glauque which was, in turn, a refinement of the basic process of regenerative cooling used by James Dewar in the first liquefaction of hydrogen in 1898. The process consisted of cooling highpressure gaseous hydrogen as close as possible to the boiling point of liquid hydrogen (20.3 K) and then expanding the gas through a valve. Expansion provided the final cooling needed to liquefy part of the gas. Dewar used boiling liquid air for part of the hydrogen cooling and passed the cold, expanded hydrogen gas through a coil containing the incoming high-pressure gas on its way to the expansion valve. Giauque and Johnston did the same, although they used a total of eight heat exchangers to increase liquefaction efficiency. The liquefier (fig. 2) was diagramed and described by Johnston in 1946.

In steady-state operation, liquid hydrogen was in the left column (fig. 3). This column had four heat exchangers: the three upper ones, A', B, and F, used escaping cold gaseous hydrogen as a coolant; the bottom heat exchanger, G, was immersed in the liquid hydrogen, which served as a coolant. The right column also had four heat exchangers; the two upper ones, A and C, used escaping cold gaseous nitrogen and oxygen, from liquid air boiling under reduced pressure, as coolants. The two lower heat exchangers, E and D, were immersed in liquid air as coolant. The liquid air was in two containers connected by a float valve, to ensure that the escaping gases were nitrogen-rich. (if the gas were oxygen-rich, it would burn when in contact with the oil of the pump.)

Incoming hydrogen gas at room temperature and a pressure of about 125 atmospheres was split between the two columns and received its first cooling in heat exchangers A and A'. The two hydrogen streams then combined and passed, successively, through heat exchangers B, C, D, E, F, and G, getting progressively colder until (at G) the gas was near the boiling point of liquid hydrogen, 20.3 K. Finally, the high pressure, cold hydrogen gas expanded through valve H and about 20 percent of it liquefied. The rest passed up through the heat exchangers and cooled the incoming high pressure hydrogen as previously mentioned. The liquefier produced about 25 liters per hour.