Superheavy

by Kit Chapman

  Currently, the ‘pitch drop’ holds the world record for the longest continuously running lab experiment. It produces a single drop about once a decade – so far it’s up to nine drops. The experiment (like Livermore’s light bulb) is monitored constantly by webcam. John Mainstone, who inherited the experiment from Parnell, never saw the drop despite watching the pitch almost religiously for over 50 years. In 1988 he missed the rare event by minutes. ‘I decided that I need a cup of tea or something like that, walked away, came back, and lo and behold it had dropped,’ he told National Public Radio with a heavy heart. ‘One becomes a bit philosophical about this.’

  The pitch drop has nothing on RIKEN. Heating up pitch and leaving it alone isn’t particularly expensive, and you can see when a drop is ready to fall for about a year in advance. RIKEN’s hope involved blasting 6 trillion ions a second for months at a time at their rotating bismuth targets, hoping to see an unpredictable event that wouldn’t even last a thousandth of a second.

  RIKEN’s control centre is organised chaos compared with the elegance of GSI or the industrial brutalism of Dubna; it feels like a cyberpunk lair. We’ve headed upstairs from the meeting room, into the workhorse section of the lab, away from the Lego models and into a realm of 24/7 science. Wires swarm out of circuit boards, monitors pile up and stained bins are filled with discarded energy drinks. The chairs are beaten and cosy. The whole place has a hum of sweat, perseverance and toil. Along the top of the control deck are two brightly coloured plush toys, a couple of creatures that look something like monkeys in space suits.

  ‘They are Wakō City’s mascots,’ one of my hosts remarks. I forgot everything in Japan has its own mascot. Cities. Fire departments. Schools. Does RIKEN have a mascot?

  Awkward silence. ‘Uh … yes and no. There was one, once. It was a sort of, uh, termite.’ A team member gives the Wakō mascots a reassuring pat. I get the distinct impression the space monkeys aren’t going to be replaced any time soon.

  I’m guided to a computer screen, a host of applications open on its desktop. To the side is a white block showing some kind of radioactive trace. In the centre of the screen is an immediate contrast: a black box with a red cross at its heart. It looks like an old computer game from the 1980s: no fancy graphics, just x marks the spot. ‘This is element 113,’ I’m told by my guide – they’ve called up the record of what they saw in 2012 to demonstrate what an event looks like. ‘This white screen, here, means there’s been an implantation event.’ That’s when a newly fused element ricochets off and implants on the detector. ‘A red cross means you have an alpha-like event.’ The ricochet has decayed. ‘Three of those, you get a new element.’

  It’s hard to imagine how seeing that little cross – a single atom of element 113 – must have felt. It reminds me of the old video game Desert Bus, in which the player drives on a straight road for eight hours. Complete one trip and you get one point. It’s so mind-numbing that gamers play it as an endurance feat to raise money for charity.3 Most beam line scientists describe a single night running their machines as a tough ask: a crucible under which tempers fray and everybody slowly goes a little insane. At RIKEN, a team of 50 scientists spent a cumulative total of 553 days of beam time just to see a little cross appear on a screen 3 times.

  They almost didn’t succeed. By 2011 Morita’s team had spent most of their budget, and the experiment was on the verge of being shut down. Bismuth and zinc are pretty cheap materials, but even so the team had burned through $3 million in electricity. There was also increased pressure to use RILAC for other, equally important experiments with a higher probability of success. Morita refused to back down. ‘I was not prepared to give up,’ he later said, ‘as I believed that one day, if we persevered, luck would fall upon us again’. Morita would head to nearby shrines and temples in his spare time and pray, placing exactly 113 yen as an offering to the gods.

  Then came an unlikely intervention. On 11 March 2011 the Tōhoku earthquake, the fourth largest quake ever recorded, shook Japan. It was the costliest disaster in history: almost 16,000 people were killed, almost 250,000 lost their homes and the destruction was valued at some $235 billion. In Fukushima, a nuclear power plant suffered three meltdowns, creating the largest nuclear incident since Chernobyl. In its aftermath, electricity prices across Japan skyrocketed. RIKEN’s Nishina Center – which has eye-watering electricity bills at the best of times – went into effective shutdown. The element hunters saw an opportunity.

  ‘It’s a bit strange,’ En’yo admits. ‘The earthquake starved us of electricity, so there was great pressure not to do a lot. So, we said “OK, we just want to do one experiment.” It meant we could run [the element search] most of the time. For two years, we shrank all of our operations except for the 113 search.’

  In August 2012 the third event appeared. ‘We had six alpha decays, seven after a beta decay,’ En’yo recalls, thinking back to the red cross appearing on the monitor. ‘And now there was no doubt about it – we had discovered element 113. We dedicated that third event to the people of Fukushima.’

  The result, coming off the back of nine years of solid work, turned the Japanese team into overnight legends among the superheavy community. ‘Imagine coming to work each 24-hour day for almost two years, and seeing no events on all but three days,’ wrote Walter Loveland and David Morrissey in Modern Nuclear Chemistry. ‘It requires an unusual degree of fortitude and courage.’ Dawn Shaughnessy’s praise is just as effusive: ‘The Japanese team were pretty hardcore. I have nothing but mad respect for what they did.’

  In 2015 the IUPAC working party met again. Both the Russian–American and Japanese teams had strengthened their cases. Researchers in Lund, Sweden, had confirmed the Dubna results, while the RIKEN group had directly synthesised new isotopes of bohrium, proving that it linked up with their recorded element 113 alpha decay chain.

  It was a dead heat, and the element could have been awarded to either team. But ultimately, the working party found that the Dubna–Livermore claim hadn’t fulfilled all criteria for discovering an element. The Russians were incensed: there was little doubt they had discovered the element first, and they had spent eight years and thousands of hours of beam time too. But the IUPAC decision was final – element 113 had been discovered by RIKEN.4

  For 100 years, Japan had dreamed of an element on the periodic table. Finally, it had one. The celebration was so large it was even attended by Crown Prince Naruhito, honouring the imperial family’s long-standing connections to RIKEN. ‘I am deeply moved by the addition of the new element,’ he stated – before observing that he used to copy out the periodic table by hand in high school. In Japan, there could be no higher praise.

  Dubna and Livermore had toasted their successful discovery of 114 and 116 with ‘flerovium’ vodka and ‘livermorium’ wine. RIKEN went a little further. In 2010 the Nishina Center team had put a batch of brewing yeast into their RILAC beam and induced mutagenesis – changing its genetic code to create an entirely new strain. The result was Nishina Homare sake (‘in honour of Nishina’). What better way to celebrate an element than mutant rice wine created from your own ion cannon?

  Perhaps the most cathartic moment was the choice of name. ‘Nipponium’ was out of the question – Ogawa had already used it for his misidentified ‘element 43’, and IUPAC’s rules were clear that a name couldn’t be repeated. But there are two words in Japanese for their homeland, the land of the Rising Sun: Nippon and Nihon. Element 113 became ‘nihonium’.

  * * *

  ‘Why produce new elements and isotopes? It’s a good question. They have short half-lives and no practical application.’ Hiromitsu Haba, one of the RIKEN chemists, takes his time as he thinks about the answer. Haba is one of the team who dedicated over a decade of their lives to hunting down element 113. What makes that level of commitment worth it?

  ‘The elements are very important for the universe, for the body, for everything!’ Haba says finally. ‘If we can understand such elemental pa
rticles, we can come up with good theories. Currently, we know 3,000 isotopes. But, theoretically, there are 10,000 isotopes. We only know a third of our world.’

  Haba is referring to the latest models. Since Maria Goeppert Mayer and Hans Jensen blew the understanding of the nucleus wide open with their shell model, physicists have been trying to work out just how far the periodic table stretches – how much of the building blocks of existence remain undiscovered. Usually, this is presented as the chart of nuclides – like RIKEN’s Lego model or Glenn Seaborg and Georgy Flerov’s drawings of the ‘sea of instability’. The borders of this map are the ‘drip lines’: beyond the neutron drip line, the nucleus kicks out a neutron before it forms; beyond the proton drip line, the same happens for protons. Anything between the drip lines is theoretically possible. Currently, the best guess – and it is only a guess – is that the elements as we know them stretch out to number 172.

  RIKEN is hard at work to fill in these blanks. Between 2016 and 2018, the team discovered 73 new nuclides, from isotopes of manganese to erbium. Each contained more neutrons than ever before seen. All of them were created using fission. Rather than trying to avoid the element splitting apart, the Japanese team have revelled in it, blasting uranium at a target made of beryllium – one of the lightest elements – in the hope that the uranium atoms would break into interesting fragments.

  While these isotopes may seem pointless, Haba is quick to point out that history says otherwise. ‘Technetium was the first human element made,’ he says, thinking back to how Emilio Segrè found element 43 from one of Ernest Lawrence’s leftovers. At first, it didn’t seem too interesting. ‘Now, technetium is very important for nuclear medicine. Every year, 1 million people use radioisotopes in Japan … [and] the lanthanides are used in magnets or mobile phones. Nobody knew they would be used that way at the time they were discovered. Each element is similar, but each has its own use. Neodymium and lanthanum are similar, but they have their own uses … element 113 [and the other superheavy elements] may have a use too.’

  One of Haba’s interests is the superheavy element seaborgium. As with Robert Eichler, Haba and his colleagues are doing rapid-fire chemistry experiments to see how their fleeting products work. RIKEN even have robots to control the process, buying them valuable half-seconds in the world’s fastest chemistry experiments. ‘This is an example,’ Haba says, bringing up a molecular structure on his computer. The seaborgium atom is in the centre of a six-pointed, three-dimensional star. At each point is carbon, then oxygen. It’s a classic chemical structure known as a hexacarbonyl. ‘We produced two seaborgium isotopes, separated them and caught them. Then we added carbon monoxide (CO) here, so we can see if it interacts. Now we know that this hexacarbonyl compound exists. By heating the molecules, we can destroy them and investigate the bond strength between the seaborgium and carbon. We can then compare them with theoretical calculations.’

  All of this is again part of rewriting the periodic table. Seaborgium is, supposedly, in the same group as tungsten. But what if it doesn’t behave like tungsten at all? ‘The structure of the periodic table is not going to change,’ Haba stresses. ‘The element is put on the periodic table irrelevant of its properties … but it’s very difficult to get used to the chemistry on this row of the periodic table.’

  Not everyone agrees. As with the weight of the kilogram, science has a habit of self-correcting. While an element’s number on the periodic table is static, positions can move about: after all, until Glenn Seaborg came along, uranium had been placed under tungsten, the very position seaborgium occupies today. ‘As a chemist, the usefulness of the periodic table is the periodicity – if shown that these new elements belong in a different group, they should be moved there,’ observes Nancy Stoyer. ‘The periodic table is a living construct.’

  If this debate sounds pointless, it’s anything but. By working out how the relativistic effects change the elements, how they stop following rules that science has trusted for centuries, we can work smarter and find new ways to use the elements we have discovered. Remember the search for naturally occurring superheavy elements in the 1970s, with the US and Russian teams launching expeditions into hot springs or the depths of the Gobi Desert to try and find them? Today’s researchers know those searches were looking in all the wrong places: they were basing their hunt on incorrect assumptions about how superheavy elements behave. Years were wasted because we didn’t understand the rules of physical reality.

  It’s only by discovering more elements that we can work out what those rules really are.

  * * *

  RIKEN – like the rest of Japan – isn’t satisfied with one element. Already, its researchers are hunting for more. RILAC is being reconfigured for new experiments; the Nishina Center’s oldest cyclotron has already started the search. Both machines are going to run in parallel to hunt for elements 119 and 120 until they are found. With the new elements’ cross sections predicted to be orders of magnitude lower than nihonium, there’s no point trying cold fusion. Three hits could take centuries. Instead, the RIKEN team have taken a leaf from Oganessian’s playbook and switched to hot fusion.

  The reconfiguration of the linear accelerator is the big challenge. It has already cost $40 million just to make the changes required. ‘Not all of the linear accelerator’s parts are superconducting,’ En’yo explains. ‘That lets you go to a lower charge state more effectively. To convert it requires two years, which is why we decided to use the cyclotron as well. The cyclotron isn’t better than the linear accelerator, but with a good ion source we can overcome that and get a reasonable enough intensity to start the 119 search until the linear accelerator is remodelled with a stronger beam.’

  This revamped machine will bring new demands. When the team discovered nihonium, shooting zinc into bismuth, the main cost was electricity: zinc and bismuth are cheap. Conversely, hot fusion requires curium targets, created and shipped over especially from Oak Ridge’s HFIR. The search will cost $1 million a year. But it doesn’t matter if the new experiment costs millions or takes another nine years to produce its success: as it has proved time and time again, RIKEN doesn’t back down.

  ‘We’ll keep running the experiment until we make the discovery,’ En’yo says. ‘Or someone else does.’

  The someone else is Yuri Oganessian. While the Japanese were searching for nihonium, he had finished the seventh row of the periodic table.

  Notes

  1 It’s a source of amusement to the Japanese team that neptunium – which could have been Nishina’s – still ended up as ‘Np’ on the periodic table: it’s the symbol that would have been used for ‘nipponium’.

  2 As with the Allied effort, the generals in charge of Ni-Go didn’t really grasp the concept of a nuclear bomb. On one occasion, Nishina’s military liaison, Major General Nobuji, asked him why, if a bomb needed 10kg (22lb) of uranium, they couldn’t just use 10kg of conventional explosives instead?

  3 Desert Bus was initially created as a performance art piece by magicians Penn & Teller; even so, each year the marathon game session ‘Desert Bus for Hope’ raises over $500,000.

  4 To make matters worse, the IUPAC finding was littered with technical errors; to this day, the Dubna–Livermore group feel robbed. ‘Details matter, and the sloppy IUPAC report is unsatisfactory,’ Mark Stoyer notes. ‘I think all the hard-working scientists in this field have again been done a disservice.’

  CHAPTER TWENTY

  The Edge of the Unknown

  Commercial airlines carry all kinds of curios in their cargo holds. The average passenger flight has a couple of tonnes of freight on board: everything from the post and pets (several million animals fly around the world each year), to rarer items such as live lobsters for restaurants or stacks of gold bullion. In 2012 a crocodile being transported from Brisbane to Melbourne escaped its container and roamed the cargo hold of a Qantas jet until it was discovered by the baggage handlers. Generally, if something needs to arrive in a hurry – be it a he
art on ice for a transplant or a sample of horse semen for breeding – a commercial airline is the way to go.

  The person with the final say over what comes on board a plane is the captain. With almost complete power, a pilot can decide whether to refuse a passenger, turn away a piece of cargo going in the hold or even abort the flight entirely.

  In 2009 an unusual package made its way to JFK Airport, New York, and onto a Delta flight bound for Moscow. As the captain checked the manifest, he raised an eyebrow at the strange cargo: a piece of metal about the weight of a sesame seed that was encased in lead and plastered with radioactive warnings. It was a sample of element 97, berkelium. And this was the fifth time it was about to cross the Atlantic Ocean.

  For years, Yuri Oganessian had been trying to make element 117. All the other ‘missing’ elements of the seventh row – 118, 115 and 113 – had, by then, solid evidence for their existence. The problem was that if the team were to stick with a calcium-48 beam, they needed a berkelium target. There just wasn’t enough of it to make one.

  As mentioned in Chapter 3, there are only two places on Earth capable of producing large quantities of berkelium: the Research Institute of Atomic Reactors at Dimitrovgrad, and HFIR at Oak Ridge. As berkelium has no commercial use, neither the US nor the Russians had any reason to make it directly. Instead, it was usually found as a by-product of its daughter element, californium, which could be used to start up nuclear reactors, identify gold and determine the geology of oil wells. In stark contrast to its neighbour on the periodic table, in the 60 years since it was first created californium had become the most valuable metal on the planet. Today, the asking price is around $27 million a gram.

  Oganessian repeatedly tried to convince Dimitrovgrad to supply any leftover berkelium from a californium production run, but had no success. Instead, he turned his attention to Oak Ridge.