AMONG THE MANY SKETCHES THAT LINGERED IN DUDLEY BUCK’S notebook as he flitted between multiple projects was a design for a device made from two small wires, which he called a Bismutron. Bismuth is a brittle white metal, often confused with lead at first sight. It can be made extremely resistant to electricity using magnets; with just a small magnetic force it can block electricity altogether. Buck believed that resistance could be used to create computer “bits.” The first iteration of the idea was noted in the spring of 1952, two days before he was flown to Corona, California, to be inducted back into the intelligence community. He started working on it in the lab soon thereafter.
He took two bismuth wires and managed to use them to rig up a basic computer circuit. If he passed a current briefly through the first loop of wire, the circuit could represent a zero. If he did the same to the second, it represented a one. As a pair, the two wires could create a binary digit, and do so quickly. They could show zero or one. One of the best things about it was that it had no moving parts.
The idea worked neatly and was witnessed in Buck’s notebook by his lab partner Ken Olsen, who would go on to make a fortune creating Digital Equipment Corporation, one of America’s first office computer companies. There was a problem, however. To make the Bismutron work, it had to be hooked up to other computer circuits using the existing technologies of valves and switches. And it needed the small amount of current to keep passing through it in order to maintain the one or zero that had been stored.
The Bismutron was a bit pointless, in other words. For a brief moment, Buck was the laughingstock of the Digital Computing Laboratory at MIT. That did not stop him from mentioning his new gadget to his peers at the NSA, however. For he was confident the idea was a good one.
In between his day job testing magnetic memories for the Whirlwind computer and his extracurricular activities with nuclear mud from the bottom of the Pacific, Buck used his time in the lab to plug away at his idea.
Throughout this time, Jackie hardly saw her fiancé. He was out of town a lot, and when he was back in Boston he was often in the lab for hours at a time. He and Olsen were at their most productive period on the Whirlwind project, designing and patenting computer components that would go on to generate millions of dollars for MIT.
Although he had not yet even been awarded his doctorate by MIT, Buck was being asked to lecture all over the country. Also, through his NSA connections, he had picked up another occasional consulting contract with the RAND Corporation in Santa Monica, California, earning him the princely sum of forty-five dollars a day.
For Jackie, dates with Buck became five-minute sandwich lunches over his workbench in MIT’s Digital Computing Laboratory.
The Bismutron was stuck in Buck’s head. Although he acknowledged it did not work, he was certain there was a valid idea in there somewhere. Eventually, the cold Massachusetts winter sparked a brain wave.
It was Saturday, December 15, 1953. Buck had taken on the running of the Wilmington Scout Troop, mostly out of interest for his foster son, Glenn Campbell. That morning he had arranged a brisk winter hike out to their campground, five miles north of town. The land had been donated to the scouts by a local attorney and it played host to an annual “camporee” every May. Throughout the year Buck would make the boys hike out to the camp and back fairly regularly.
It appears that on that wintry ten-mile round-trip, Buck came up with a modification to his Bismutron idea. What about making a switch that operated at subzero temperatures?
His experiments with deuterium had taught him a little about cryogenic substances, as had the Ivy Mike hydrogen bomb. At MIT, meanwhile, the physics department had perfected the art of making liquid helium—which was allowing all manner of experiments to be carried out at temperatures as low as -269 degrees Celsius. Temperatures that low opened up the world of superconductors—metals that conduct electricity with no resistance at all if they are cold enough.
If Buck used superconductors for his tiny switches, the current would only need to be applied once for it to maintain a zero or one, solving one of the key problems with the Bismutron. It had also been proven that superconductors stopped conducting electricity instantly once exposed to a magnetic field. It should be possible, therefore, to use that rapid change of state to create an ultrafast switch. Superconducting metals, in their cryogenic state, would register as a one. The interrupting force of the magnetic field could then flip it back to zero.
Buck got into the lab first thing on Monday morning, grabbed his notebook, and scribbled down the idea: “Use hysteresis of superconductors as the basis for a superconducting matrix memory. The superconducting state could represent a ONE and the normal state a ZERO.” The note was witnessed by another researcher named John B. Goodenough, a name that rarely popped up in Buck’s notes either before or after this time. He seems to have been the only other person in the lab that early who was qualified to declare that Buck’s idea had been “discussed and understood.”
Superconductors had been known about for forty-two years, but no one had found any practical use for them. They were just one of those interesting physical phenomena discovered almost by accident.
A scientist at Leiden University in the Netherlands named H. Kamerlingh Onnes had worked out how to liquefy helium in about 1908. Three years later he started experimenting on how various metals behaved in this new extremely cold environment he had created. He found that the resistance of mercury suddenly dropped to zero after the temperature reached a certain point. Other metals—such as aluminum and titanium—did the same thing at different temperatures.
Superconductors sounded too good to be true. What they promised was, in essence, perpetual motion: if there was genuinely zero resistance to an electric current it would keep running indefinitely until some other force was applied. The only problem was that the phenomenon only existed at these extremely low temperatures that had to be artificially created by using huge amounts of energy.
S. C. Collins at MIT had built his own machine to liquefy helium immediately after the war, and had taken the experiments to whole new levels. He found that metals that were normally good at conducting electricity—like gold, silver, and copper—were unchanged by exposure to the low temperatures.
Yet some metals that naturally blocked an electric current at room temperature became superconductors once they were steeped in a vat of liquid helium; the most extreme examples were lead and two much rarer metals named tantalum and niobium.
It was this last group of superconductors that Buck was interested in. If he applied a magnetic force at the right temperature, these largely unknown metals could potentially become the backbone for a minuscule, and ultrafast, computer.
Buck knew that to expand on his theory he would have to get hold of wire made from these different superconducting elements and a reasonable amount of liquid helium.
With the university closed for Christmas, he worked day and night on experiments for the Whirlwind project and assorted jobs for the NSA. On New Year’s Eve he filed a big report on magnetic computer memories for General Electronic Laboratories in Boston related to a contract they had won to build a computer for the US Bureau of Ships.
As 1954 arrived, he was working furiously on his new idea, leaving the house in Wilmington at the crack of dawn and returning late in the evening. By January 6 he had worked up detailed sketches of how to build and test his new “superconducting switch”—and then start to hook it up to other circuits, assuming it could be made to work.
After a brief trip to New York to give a lecture on his Whirlwind work for the American Institute of Electrical Engineers, Buck cleared his diary to press on with the work.
By February 10, he had successfully begged Collins to give him regular access to his helium tanks, with the agreement he would rent them out hour by hour. He then conceived a test to check that the metals were indeed in a superconducting state inside the helium flask, witnessed by his lab partner Bill Papian. He took further measurements to check the temperature range at which the metals would remain in this state, again witnessed by Papian. Buck also had to build a special metal contraption to lower his gadget into the cryogenic freezer of liquid helium—which spewed plumes of dry ice clouds across the room. By Valentine’s Day, he had worked out how to get a strip of tantalum with holes punched in it. The magnetic control wires that would switch it on and off were to be fed through the holes.
To the untrained eye, Buck’s device was just one bit of wire with a slightly different colored wire wrapped around it, strapped to the end of a metal pole. By February 18, 1954, after one failed test run, the superconducting switch he had conceived appeared to work. It had been able to switch from conducting a current, to resisting it.
When he returned to the lab on Monday, Buck got back to his new pet project with all guns blazing. He only took a break to have lunch (again, sandwiches in the lab) with Jackie, who had not seen him all weekend; he had been leading the first scout camp of the year.
They chatted over the steaming vat of liquid helium that Buck was using for his experiments. He explained to his future wife in loose terms what it was he had found.
“What are you going to call it?” she asked.
He confessed that the term “superconducting switch” lacked a certain lyrical quality. He was toying with the idea of calling it a “cryistor”—smashing together the words “cryogenic” and “transistor.” It was literal enough for the scientists to get it, and yet had a futuristic ring to it.
Jackie wasn’t so sure. The word looked a bit ugly. “Why don’t you call it the cryotron?”