Superheavy

by Kit Chapman

  They didn’t. By the time they had produced both elements themselves, in 1954, a small team from the Nobel Institute of Physics in Stockholm, Sweden had contacted Seaborg to tell him they had created element 100. It was a blessing in disguise: if the elements existed in the lab in another country, there was no need to keep the US findings from the Ivy Mike blast a secret. Ten days after the Swedish team announced their discovery, Ghiorso’s own results appeared, taking care to mention ‘unpublished [classified] information’ to remove all doubt about who got there first. The Ivy Mike findings were finally declassified a year later, and elements 99 and 100 joined the periodic table.

  There was still the matter of the dispute between the US labs. After a face-to-face meeting in Chicago, the discovery was given to Berkeley (99 with the aid of Los Alamos). That night Seaborg wrote in his journal that he and Ghiorso enjoyed ‘an abundance of cocktails’, so much so they didn’t even remember flying home.

  The elements needed names. Bizarrely, they already seemed to have them: a talk by Luis Alvarez had been misinterpreted a few years earlier, and some textbooks already listed 99 and 100 as ‘athenium’ and ‘centurium’ respectively. The first kooks of the nuclear age had also emerged, with one laying claim to the elements in the Physical Review as ‘ninetynineum and centinium … I value and honor each atom at a million dollars’.

  Berkeley got to have the final say. Ghiorso made it strongly known that he wanted to name them after prominent scientists, and thought there were two obvious candidates: Albert Einstein and Enrico Fermi. Seaborg and the rest of the team agreed. Fermi was dying of stomach cancer, but Seaborg knew Emilio Segrè was in regular contact with his mentor and asked him to pass on the group decision. Segrè, blasé as ever, replied ‘that he was not interested enough to do so’. By the time einsteinium and fermium became official, in August 1955, both elements’ namesakes had died. Ghiorso had already written to Laura Fermi that element 100 would be named after her husband: ‘It was my good fortune and privilege to know your husband […] I can say from personal contact that science has lost a very warm-hearted human being as well as its greatest physicist.’

  * * *

  ‘Fermium’ was a fitting choice for element 100. The Italian maverick, frolicking with the sheer joy of science in a fish pond, piping in radioactive gas from basement safes and building nuclear reactors under sports stadiums, had brought in the atomic age; the element named after him would bring the age of atomic discovery to a close. With fermium, the nuclei become too unstable, with half-lives too short to make in large enough quantities. Fermium atoms are too large to beta decay, so neutron capture stops being viable. Worse, later research in the 1970s showed that fermium-259 has a spontaneous fission ‘disaster’ and tends to break apart on its own in about 0.038 milliseconds.

  The physicists of the time wondered if this was the limit of the periodic table. The idea that the nucleus acted like a drop of liquid was still in vogue; theoreticians had long showed that no element beyond fermium, element 100, could possibly exist. It would simply break apart before it had a chance to form.

  Yet minds were changing. In 1955 John Archibald Wheeler, one of the most eminent physicists in the US, announced that there was no reason more elements couldn’t be out there. At the International Conference on the Peaceful Uses of Atomic Energy, he put up a diagram highlighting the region where elements could have a half-life of more than 100 microseconds (100 millionths of a second). It stretched out to masses twice as heavy as those that had been found before. Soon, everyone was putting forward their own theories about where the periodic table would end. Richard Feynman, one of the most influential physicists of the twentieth century, used electron orbital models to suggest that the final element would be 137; other researchers suggested 172; yet more used quantum mechanics to suggest that the last true element would have 173 protons, before crashing into a ‘sea’ of particles with negative energy.

  The only thing for certain was that any elements past fermium would have to be made by fusion, one atom at a time. It would require work at scales smaller than human comprehension, and accelerator beams more intense than anything constructed before. It was just the kind of challenge Ghiorso and Thompson relished.

  Elements 101, 102 and 103 were part of Seaborg’s actinides.

  Beyond was the realm of the superheavy elements.

  CHAPTER SEVEN

  Presidents and Beetles

  It was midnight. The Volkswagen Beetle hurtled up the twisting roads of Blackberry Canyon, Al Ghiorso’s foot anchored to the accelerator. At his side, his assistant Gregory Choppin – a 20-something a couple of years into his research career – was clutching a test tube furiously, his body battered from side to side as Ghiorso hit the apex of each bend. The Beetle was supercharged (of course it was, it was Ghiorso’s), taking corners at breakneck speed as it covered the mile between the Berkeley accelerator and Stanley Thompson’s lab as quickly as possible.1 Below, the lights of the Bay Area drizzled into a sea of orange, but Ghiorso’s attention was on the shadows ahead at the security gate. Suddenly one of the dark shapes leaped out, levelling a gun at the oncoming vehicle.

  ‘Stop or I’ll shoot!’

  Ghiorso narrowed his eyes and tightened his grip on the wheel – he wasn’t about to stop for anyone. Playing chicken with a loaded gun, the engineer sped on. Wisely, the security guard decided to get the hell out of the way. Ghiorso’s Bug flew on up the hill and skidded to a halt outside Thompson’s building, where its two passengers rushed inside.

  ‘[The guard] was very much distressed,’ Ghiorso later wrote in The Transuranium People. ‘He came up to our lab afterwards and we apologised, but we told him we were too busy with the experiment to talk about the incident at the moment. We got away with it.’

  The reason for the late-night dash and the team’s disregard for lab security was simple: Ghiorso and Choppin were trying to make element 101 – and they didn’t have a second to lose.

  Berkeley in 1955 was a strange combination of free thinking and fear. Already the Beat Generation had descended on nearby San Francisco, creating a second renaissance of modern poetry. In the coming years, rock and roll, flower power and free love would all bloom within the West Coast’s premier science hub. It was a stark, colourful contrast to the monochrome of the ‘loyalty review boards’ that still dominated Eisenhower’s America. These, spearheaded by Senator Joseph McCarthy and the House Un-American Activities Committee, thrived on destroying the careers of anyone they didn’t like. In the past year, Robert Oppenheimer – the man who had led the Manhattan Project – had found his security clearance revoked for past interest in the Communist Party. It was a garbage charge and everyone knew it, but Oppenheimer had enemies who wanted him gone. Glenn Seaborg’s largely neutral testimony was one of six used to show the great Oppie’s ‘want of character’. The moment haunted the chemist for the rest of his life. ‘It was a chilling lesson,’ he would write in his autobiography, ‘about the consequences of making enemies, about powerful egos reacting to slights and retaliating.’

  Seaborg had more luck shielding Ghiorso from the ‘Red Scare’ witch-hunters. Wilma Ghiorso had been a communist; she and Helen Seaborg had also been engaged in ‘subversive’ activities such as attending band performances on ‘coloured’ nights – the music was better than the stuff played for white crowds. Either fact would have easily spelled the end of the outspoken Ghiorso’s career if it hadn’t been for his friend’s influence. ‘I never detected a hint of anything that would make anyone suspect any disloyalty,’ Seaborg recalled, ‘yet sometimes I had to fight like hell to keep the security people from revoking his clearance.’ The Beetle incident was yet another example of Ghiorso bending, breaking or completely ignoring the rules.

  Three years earlier, he’d been on a cross-country flight when a brilliant thought flashed, perfectly formed, into his mind. Scrambling around, he had grabbed the back of an envelope (it was that or the sick bag) and begun writing down some calculations. Nucl
ear physics had, by this point, reached sizes so small conventional measurements became pointless. Instead, the researchers had developed their own strange, informal language. A ‘shake’, for example, was 10 nanoseconds, the time a neutron takes to cause a fission event. This had come straight from the expression ‘two shakes of a lamb’s tail’ (a nuclear bomb, in case you’re wondering, goes off in about 50 to 100 shakes). The chance of a nuclear reaction occurring wasn’t measured in percentages, but in ‘cross sections’ – a peculiar mix of size and probability. Cross sections were measured in ‘barns’ (from the phrase ‘can’t hit the broad side of a barn’). A barn was roughly the size of a uranium nucleus: about 10-28m2. The bigger the cross section, the greater the chance of something happening. When it came to making new and heavier elements, the reaction cross sections were getting smaller at an alarming rate.

  Sat in his seat at cruising altitude, scrawling a literal back-of-an-envelope calculation, Ghiorso reckoned that if he could somehow get hold of 3 billion atoms of einsteinium and smack them with a beam of alpha particles, he would have a reaction cross section of about a millibarn – one atom of element 101 every five minutes.

  Ghiorso had smelled blood. How could he resist?

  * * *

  There’s a moment in Iron Man 2 where Tony Stark, played by the sharp-tongued Robert Downey Jr, makes a new element based on some architectural plans his dad left him. It’s the sort of thing that gets mocked regularly by scientists ... as if a movie whose villain is a dude with a magical electric whip was striving for factual accuracy.

  Stark makes his beam line using anything to hand (including Captain America’s shield), then twists it where it needs to go without any regard for lab safety. He makes his corrections on the fly, using little more than a wrench and scientific intuition, setting the rest of the room on fire as he shifts the beam. You don’t see his private cyclotron, but I’ll give him a pass – Stark is the kind of rich arsehole that probably already has one built in his garage. The crazy thing about this scene is that it’s not actually that ridiculous: Ghiorso, if he’d ever owned a TV, would have found Stark a kindred spirit.

  The real problem with the Iron Man 2 scene isn’t the way Stark’s equipment is set up. It’s not his dad’s strange legacy, either (sometimes element creators have to wait until the right technology is available, even if building schematics is an odd way to preserve your ideas). The issue is that the moment Stark twists his beam onto his target it instantly turns every atom into his desired element.2 Cross sections don’t work like that. If they did, we’d have filled the periodic table a long time ago.

  For Ghiorso and the Berkeley team, the challenges of the ‘atom-at-a-time’ science needed to make element 101 were staggering. First, they had to rebuild their cyclotron. Ghiorso’s calculations hinged on firing a beam of 1014 alpha particles. The problem was that no machine in the world could do that. ‘The assumption of beam intensity was about an order of magnitude greater than had ever been obtained,’ Ghiorso later wrote, ‘but I blithely assumed that this problem could be overcome.’ He was right – once Seaborg obtained the funds, Ghiorso tweaked his machine and somehow managed to increase the beam’s intensity 100-fold.

  Next, the team needed to get hold of einsteinium. ‘We calculated that a one-year irradiation of plutonium would yield about one billion atoms of [einsteinium],’ Choppin recalled in Chemical & Engineering News. Einsteinium-253 had a half-life of around three weeks. Berkeley would have to wait a full year to get the bare minimum they needed for a target and then would have, at best, a few months to shoot for element 101.

  Einsteinium couldn’t be placed in the machine on its own – weighing less than a billionth of a milligram, the amount was so small it could only be seen under a microscope. Instead, it was stuck to a thin layer of gold foil. Here, Ghiorso added a twist: instead of facing the beam, the einsteinium was placed facing the wrong way. Knowing that most of a beam’s ions missed their target, Ghiorso was counting on the beam shooting straight through the gold without any problem. If the beam then hit the einsteinium and caused fusion, any newly created element 101 atoms would be sent recoiling from the force of the impact.

  It was a brilliant idea. To discover an element, all Ghiorso needed to do was place another layer of gold foil at the back of his beam line to act as a sort of chemical catcher’s net. Each night, the net could be replaced and checked for any signs of element 101 – there was no need to interfere with the einsteinium target or the beam line at all.

  The final hurdle to element discovery was time. Element 101 would likely have a half-life of minutes. For previous elements, this wasn’t an issue: as a rule of thumb, it takes around 10 half-lives for a reasonable quantity of material to decay away. But when you’re producing a single atom at a time, a split second could be the difference between discovery and your product vanishing forever. Ghiorso knew he had to get his sample from the cyclotron on campus to Thompson’s chemistry lab at the top of the hill faster than lab protocols would allow – which led to his midnight run with the Volkswagen Beetle.

  The hunt for element 101 started off badly. The einsteinium wouldn’t stick to the gold foil, and every time the team tried to make it adhere the whole experiment had to be restarted from scratch, recovering and repurifying every precious atom. ‘We made something like five targets before we had a successful one,’ Ghiorso recalled. The team tried everything they could think of – including welding it on with a blow torch – before another team member, Bernard Harvey, solved the problem with electroplating. They had a target. ‘It was remarkable,’ Seaborg recalled, ‘in that this was the first time that such a small amount of target material was used. An invisible amount – and I mean a really invisible amount.’

  You can see a recreation of what happened next on YouTube: a few years later, KQED, a local educational TV station, asked the team to re-enact their discovery.3 Ghiorso, in a heavy lab coat, loads up the einsteinium into Berkeley’s 60-inch cyclotron with forceps. Then he adds the gold catcher foil. The machine starts up and launches alpha particles at the foil. After three hours, Ghiorso and Harvey force open the thick lead safety door to the radioactive chamber. It’s so heavy both men have to kick their legs against the wall just to prise it open.

  A foot race begins, man against the clock. Harvey runs inside, grabs the catcher foil and sprints upstairs. Ghiorso dashes outside. Harvey hands the foil to Choppin, who drops it into a test tube filled with nitric acid and hydrochloric acid. As the foil begins to dissolve, he grabs the test tube and rushes out to Ghiorso’s Beetle, leaping into the passenger side. Ghiorso hits the accelerator before Choppin has even closed the door, hurtling the car around Berkeley and racing up to the lab. The Bug skids to a halt outside the chemistry building. Quickly, the test tube is whisked from the car and handed to Thompson, who runs the tube’s contents through a series of chemical reactions to get rid of the gold, acid and fission products. Then all the team have to do is load the suspected element 101 into an alpha radiation detector and wait for it to decay.

  On 19 February 1955 the team got their first hit. Not wanting to sit around all night checking the machine, Ghiorso had jury-rigged the lab’s fire alarm to the detector, setting it to ring if there was any sign of alpha decay. Just before dawn, as the team wolfed down their breakfast of bacon and eggs, the fire alarm sounded. Choppin recorded the incident in a 1978 high school chemistry book: ‘We all gave a loud, enthusiastic cheer […] Bernie Harvey wrote “Hooray” on the chart beside the deflection […] When the fire alarm went off a second time, indicating that a second atom of 101 had decayed, Bernie wrote “Double Hooray”, and after the next deflection, he wrote “Triple Hooray”.’

  Exhausted and elated, Ghiorso went home to bed, safe in the knowledge that he had discovered yet another chemical element. The next morning, he found himself summoned to the office of an irate Glenn Seaborg. There had been a fourth decay from their sample of element 101. In his excitement, Ghiorso had forgotten to unhook the detec
tor from the alarm and had sent the laboratory’s staff and students fleeing the area in panic. Ernest Lawrence had sent Seaborg a note congratulating him on the discovery… and reminding him it was lab policy not to tamper with the fire alarms.

  * * *

  The discovery of element 101 was confirmed with just 17 atoms. It was an incredible feat of science and engineering. Emboldened, Ghiorso also chose a name for it that was designed to fly in the face of McCarthyism. When the element was announced in the June 1955 edition of Physical Review, the team declared that it would be called ‘mendelevium’, in honour of Dmitri Mendeleev, the man who had come up with the periodic table. It was an audacious choice: at the height of the Cold War, Ghiorso was taking an American discovery and naming it after a Russian. ‘We felt that an aggressive approach might be in order,’ he reasoned, ‘that if we just called it “mendelevium”, maybe it would be all right.’

  It soon turned out that the move would be a vital olive branch in East–West relations. A few years later, US Vice President Richard Nixon went to Moscow for negotiations with Soviet Premier Nikita Khrushchev. Seaborg was acquainted with Nixon and passed on his anecdotes about the element’s discovery. After the visit, Seaborg received a package from the US embassy in Moscow. It contained a signed 1889 copy of Mendeleev’s Fundamentals of Chemistry and a note from a Russian fan. Nixon had used the story of Ghiorso’s escapades and made a powerful impression.

  Mendelevium marked the end of the most successful element-hunting team in history. Shortly after its discovery, Thompson took a sabbatical to another lab and left the project. Although he would continue to play a major role at Berkeley on his return, his element-hunting days were over. Seaborg’s direct involvement in the lab also began to dwindle. Already, he had been an observer at atomic bomb tests for presidents Truman and Eisenhower, had worked as a member of the Science Advisory Committee and had authored books on atoms and the wonders of the nuclear age. A few years before the mendelevium discovery, he had also taken an interest in college sports, revitalising the West Coast programme and leading to the founding of what is now the Pac-12 – the most successful college athletics conference in the US. In 1958 he would also become chancellor of the University of California, Berkeley, balancing a tricky political climate enriched by student activism and stifled by staunch conservatism.