Superheavy

by Kit Chapman

  The JINR record states that ‘it was thanks to Yuri Oganessian that the Flerov Laboratory survived and demonstrated its vitality and resilience.’ It is an understatement. Thanks to the Armenian’s gift for bringing people together, the Russian programme had gone from the brink of destruction to leading the element charge into the twenty-first century. First, they would look for elements 114 and 116 before filling out the table.

  The future belonged to Dubna. But in the meantime, Sigurd Hofmann’s group at GSI were still leading the charge – and had already laid claim to a trio of new discoveries.

  * * *

  Germany in the 1990s was, in many respects, the reverse of Russia. Since the fall of the Berlin Wall, the two halves of a split nation had reformed, reforged and come together to become the dominant player in Europe. Reunification had been a shock to the economy and had sent it into a depression, but by 1994 things had begun to turn around and the country was buoyed with hope and optimism.

  At GSI, Sigurd Hofmann’s team had everything ready for another element discovery spree. The problem was beam time. The cross sections for the superheavies discovered by cold fusion were falling by around a factor of four per element. That suggested element 110 – the next in sequence – would have a fusion cross section of 1.5 picobarns. Half-lives were shrinking too. The first isotope of meitnerium found, meitnerium-266, had a half-live of just 1.7 milliseconds before it decayed. The Germans were neck-deep in the ‘sea of instability’, completely off the peninsula where nuclides were stable. To produce a single atom of meitnerium, GSI needed to run their beam continuously for two weeks. Under the same conditions, finding element 110 would mean continuous running of the machine for almost six months without breaks – 24 hours a day, every day.

  Such a challenge would have been daunting even if the Germans could commit to it. But GSI’s accelerator was in demand for other projects – there was more important research to do than fire ions at a lump of lead and hope something would happen. No one doubted that element 110 was there to be found. The argument was that it had no practical use and the experiment had no known purpose; even if the Germans did find it, all they would be able to do is say ‘hey, look what we did’. In some eyes, it was a vanity project that would cost millions.

  The only way to get the project greenlit was to make it more efficient. ‘We started thinking about looking for 110 in 1988,’ Hofmann recalls. ‘It was my work now. We had to gain a factor of 10; we had to reduce the beam time from 150 days to 15 days.’

  It took five years to improve the machine. ‘Behind where the beam stopped, we had water cooling,’ Hofmann says, remembering the result of one of their upgrades. ‘When we fired the beam, one of the plates failed. The beam intensity had become so strong that we immediately burned a hole into it.’ Perhaps the smartest innovation was to add a deliberate bend in their detector, SHIP. After passing through electrical and magnetic deflectors, any created elements would have to navigate a seven-degree kink in the pipe, aided by deflector magnets (anything else would end up slamming into the wall). It reduced the background noise, the fission debris and flying ions, by 90 per cent.

  Hofmann’s team had also picked up the new darling of the superheavy world. Victor Ninov was a whiz-kid from Bulgaria who brought a raw, infectious enthusiasm to the team. Young, energetic and with a short crop of curling black hair, the researcher was a Renaissance man: gifted at whatever task he turned his hand toward, whether it was science, music or sport. Ninov had a wacky sense of humour – his standard sign-off on emails was ‘Your crazy Bulgarian’. His hobbies were equally eclectic. Along with Matti Leino (now at GSI), he had taken to ‘testing’ the Italian restaurants in Darmstadt, ordering the same plate of spaghetti carbonara in a quest to find the best pasta in town. ‘We were quite close,’ Leino says. ‘He was supposed to come and play violin at my wedding but had a bicycle accident and hurt his violin thumb.’ Another passion was mountain climbing, and Ninov would stay at Heinz Gäggeler’s home in the High Alps of Switzerland between experiments. ‘He was brilliant,’ Gäggeler remembers. ‘He was the enthusiastic rising star … we all liked him.’ At work, Ninov’s role in the team was critical. ‘He was quite the expert in programming computers,’ Hofmann says. ‘In 1988 we got new computers and Victor became the expert.’ Ninov devised the programme, ‘Goosy’, that would analyse the ‘hits’ and report any new elements electronically. Gone were the days of racing a Volkswagen Beetle to see what you had made or crowding around analogue monitors hoping for a ping.

  Toward the end of 1994 a slot of beam time with the GSI UNILAC opened. Hofmann was faced with a tough decision: how hard should he fire the accelerator? For the past two decades, GSI’s team had been split about what would happen with the nucleus of superheavy elements. It was clear the finely balanced forces of repulsion and attraction that kept a nucleus together had started to shift as the elements got heavier. That gave the team two options. Either they could increase the energy of their beam – a theory called ‘extra push’ – or lower the energy to sneak over the Coulomb barrier. ‘Armbruster wanted to increase the energy [of the beam],’ Hofmann remembers. ‘I wanted to decrease it. We just couldn’t decide.’ Getting it wrong at this point would have meant the whole project would have been a waste: they’d spend their time searching in the wrong direction.

  The GSI team decided to experiment. ‘We needed to measure the excitation functions very accurately. We decided to produce hassium, element 108, before we did 110. We needed iron and lead,’ Hofmann recalls. ‘The problem is that we needed 4 grams of iron-58 if we were going to run for three or four weeks. At that time, 1 gram cost 500,000 Deutschmarks.’ Today that’s worth around £500,000. The Russians came to the rescue. ‘Dubna sent us the iron, almost 21 grams of enriched iron. I kept it in my desk – I was the richest man in Darmstadt!’ The Germans, aware that the Russians were struggling, didn’t hesitate to return the favour, sending Oganessian’s team electronics and detectors that they just couldn’t get elsewhere. Oganessian’s new approach of joint working was bearing fruit.

  The experiments with hassium helped, but it still wasn’t clear what the optimum beam energy would be. Meanwhile, a queue was building up at GSI: another team needed the accelerator. Hofmann had a window of four weeks to find the elusive element 110 but was still debating the best way to go with Armbruster. In the end, Hofmann decided to take matters into his own hands. ‘Armbruster had been away in Grenoble, and I’d made all these improvements without him. So, I thought I’d do the experiment without him too!’

  On 9 November 1994 Hofmann’s team changed the iron to nickel and lowered the intensity. ‘After one day, we had our first decay chain. One day! Four weeks later, we had the whole decay chain.’

  Once again, after a gap of 10 years, elements were being uncovered at GSI. Hofmann, Ninov and the rest of the team were delirious.

  Then they heard even more exciting news: the experiment that was queued up to use the accelerator after them wasn’t ready. GSI’s superheavy element hunters had another 17 days of beam time. Having discovered one element, why not make it two? ‘This was at the end of November,’ Hofmann says. ‘I thought I’d put in a bismuth target [one proton heavier than lead] to make element 111. By the end of December, we had three decay chains for that too. It was a good year.’ The news came not a moment too soon: on New Year’s Day 1995 Münzenberg received a phone call from Yuri Oganessian. The Russians had also been looking for element 110; GSI had been barely a month ahead of the Dubna–Livermore team.1

  Hofmann’s two new elements, 110 and 111, were undisputed. Now, the team – physically and mentally drained after 24-hour stints at the beam line – wondered if they could push any further. The cross sections had continued to plummet, and the half-lives of the newly created isotopes had slipped to as low as 170 microseconds. It was unlikely they would succeed, but in the end the temptation to at least try for another element was too strong to pass up. In January 1996 Hofmann, Ninov and the others were read
y to go again, this time firing zinc into lead to make 112. To the shock of everyone, GSI seemed to strike gold almost immediately.

  ‘After one week, Ninov came to me and said we’d observed something,’ Hofmann recalls. ‘I told him “OK, let’s have a look,” and asked him to print out the raw data. Energy, time, position. It was relatively simple to make such a printout. It was about lunchtime, and Ninov said, “Yeah, I’ll do it after lunch.” He didn’t do it, so I asked him again – it was just one command on the computer – but he just said “Yeah, yeah, I have no time now.” He came several hours later with the printout. Some of the data was missing and it wasn’t what I expected for a decay chain. I told him we couldn’t publish it, we’d have to wait for another event.

  ‘A week later, we got a perfect decay chain for element 112. Everything agreed: the energies and the positions. We were really happy. This was our main publication; the earlier [Ninov] chain was simply mentioned in the paper.’

  There is an uncomfortable pause.

  ‘It is fortunate we did it this way.’

  Notes

  1 Berkeley also had an (albeit weak) claim for element 110; using cold fusion, Ghiorso et al. reported making a single atom in June 1994. But, as Ghiorso himself would concede, one atom was not enough proof, and in element discovery there is no second place.

  CHAPTER SEVENTEEN

  The Ninov Fraud

  Darleane Hoffman sat in her office on the hilly rise above the Berkeley campus, admiring the view across San Francisco Bay. In the distance she could look out and see the old federal prison on Alcatraz, the city’s main tourist attraction, and past that, the rolling fog slipping like white sheets under the Golden Gate Bridge. It was Monday, 19 April 1999. It would have been Glenn Seaborg’s eighty-seventh birthday.

  Almost 50 years earlier, she had missed the discoveries of einsteinium and fermium while she sat outside Los Alamos, waiting for HR to realise that women could be scientists too. Now, her team leaders wanted to tell her something important. She had feared the worst but had been reassured on the phone that it was good news.

  In her early seventies, Hoffman gave the impression of being someone’s sweet grandmother. Foolishly, some graduates tried to get into her group assuming she’d be a pushover. It was an opinion that was quickly dispelled – particularly if you dared to call element 105, officially dubnium, anything other than ‘hahnium’. Tough and supportive in equal measure, universally respected across the chemical world, Hoffman had dedicated her life to making sure nuclear chemistry wouldn’t die, even if she had to resuscitate it one student at a time.

  Berkeley was still playing catch-up with the other labs, but finally seemed to have turned a corner. Super-HILAC had been turned off in 1993, and the experiments had moved to the 88-inch cyclotron; SASSY had also been replaced by a new gas-filled separator (this time with a more fitting emergency valve). With it, the team hoped to hit even lower detection limits.

  Matti Nurmia had returned to Finland. In his place came three additions. The first was Darleane Hoffman’s former postdoc Ken Gregorich. Tall and wiry, with a neatly trimmed goatee and a crop of hair skirting a bald crown, Gregorich was the epitome of the ‘work hard, play hard’ attitude of nearby Silicon Valley. In the lab he was a relentless and meticulous researcher; at home he ran ultra-marathons for fun. He had worked with Hoffman since the mid-1980s and was at the vanguard of a new generation not poisoned by the Cold War. Sharp, measured and precise in his approach, to Gregorich the transfermium storms were water under the bridge. He just wanted to do good science.

  Next, on a Fulbright scholarship from the Soltan Institute for Nuclear Studies in Warsaw, Poland, was Robert Smolańczuk (Berkeley didn’t have the budget for another permanent member of the team, so the secondment was the best solution). A theoretical physicist, while Smolańczuk had been at GSI he had published some eyebrow-raising calculations. According to his theory, the cross sections for the elements beyond 114 wouldn’t vanish into the realms of statistical improbability, but rather be large enough to detect: a massive 670 picobarns. In the 1940s such a low limit would have felt impossible; by the turn of the millennium, the element hunter’s toolbox had improved so dramatically it felt like it was easy pickings – the kind of cross section that could produce hundreds of atoms a week. If Berkeley was willing to give Smolańczuk a shot, he was confident they could leap beyond anything Dubna were trying to do and find element 118. It was controversial, flying against all known wisdom. But then, wasn’t that what element hunting was all about?

  The final new arrival was considered a coup: Berkeley had tempted element superstar Victor Ninov to leave GSI and join their team. Ghiorso, technically retired but still doggedly riding his recumbent bike into work every morning, saw the newcomer as the future of element discovery. ‘Victor Ninov,’ Ghiorso would tell anyone who would listen, ‘reminds me of a young … well, a young Al Ghiorso!’ On the back of her colleague’s glowing recommendation – and letters praising his talent from his colleagues at GSI – Hoffman had placed complete faith in him; while Gregorich led the team in running the machines, Ninov had brought over his unique computer program from GSI to analyse the results. He was the only one who knew how it worked, but Berkeley didn’t need anyone else: he was the best in the world at what he did.

  Hoffman’s hand had been twisted toward Smolańczuk’s madcap idea. When Dubna claimed element 114 had been found, the Berkeley team had been a mere eight months behind them, ready to do the same experiment. However, they hadn’t been able to get hold of the large quantities of plutonium-244 or calcium-48 needed (or the permission required to use plutonium in the hills above one of the most populous metro areas in the US). Options narrowed; all that was left was ‘Robert’s reaction’: firing krypton into lead.

  Hoffman and Ghiorso had both urged doing it as soon as possible – if Smolańczuk was right, there was nothing to stop GSI or Dubna doing it first. ‘[It was] a strange reaction that no one thought would go,’ Ghiorso would later recall for the New York Times, ‘but because it was relatively easy, we thought, “What the heck, we have nothing to lose.”’ Gregorich had agreed, arguing that the efficiency of the 88-inch cyclotron was so high that even if they didn’t find 118, it would give him a chance to improve its systems. Finally, Ninov relented and threw himself into the analysis with his usual verve.

  The experiment had started on 8 April 1999 and ran for four days. At first, nothing happened. The team departed for the Easter break, leaving Ninov to check their results. Now, almost two weeks later, Hoffman watched as a trio of researchers – Gregorich, Ninov and Walter Loveland, on sabbatical from Oregon State University and there to soak up how Berkeley conducted their experiments – entered her office. They brought with them a sheet of data.

  While the experiment ran, Ninov’s analysis tool, Goosy, had found three distinct alpha decay chains resulting from fusion. Two of them matched Smolańczuk’s predictions perfectly. The numbers coming from Ninov’s analysis were too good to put down to random chance.

  Ninov laughed. ‘Does Robert talk to God, or what?’

  Berkeley had discovered element 118.

  The reaction from the team had been a mix of excitement and disbelief, even before their results had made their way to Hoffman’s desk. Loveland’s first response had been ‘What the hell is going on?’; Gregorich was surprised too; Ninov had been so taken aback he had urged his collaborators to keep the results quiet and not tell Hoffman (Loveland and Gregorich overruled him). For her part, Hoffman felt a pinch of excitement, but kept her cool. Science, she knew, thrives on verification: the experiment had to be repeated or the results were meaningless. She was too seasoned to get her hopes up on what could be a phantom.

  ‘OK,’ she said. ‘Let’s do it again.’

  The Berkeley team started a second experiment running ‘Robert’s reaction’. By the first week of May, they had another perfect chain that matched Smolańczuk’s calculations (the previous chain that didn’t follow the pattern
was discarded). Dubna’s single atom of 114 wasn’t enough to convince IUPAC of a discovery; Berkeley’s three atoms were solid, unchallengeable proof. Hoffman and Ghiorso began to dream of snatching another element out from under Oganessian’s nose. Already, thoughts turned to its name. Berkeley had seaborgium; why not ‘ghiorsium’ too?

  Wary of the false reports of discoveries throughout the Cold War, Berkeley Lab decided to proceed with caution, conducting an internal review to rule out any embarrassing mistakes. The staff double-checked everything: the ion source, the accelerator and the detectors. Nothing was wrong. Finally convinced, in June 1999 Hoffman and Ghiorso called a press conference and published their claim in full. Anyone who had been near to the experiment was added to the paper, with Ninov as first author. ‘Needless to say,’ Hoffman and Ghiorso wrote in The Transuranium People, published that year, ‘this news is an enormous surprise to the scientific world. Now there is no question, the Superheavy Island [of Stability] actually exists! […] We have convincing evidence of 114, 116 and 118! This opens up a whole new region for study.’

  Finally, on Glenn Seaborg’s birthday, Darleane Hoffman had her element. It seemed too good to be true.

  It was.

  Hoffman, Ghiorso and their team had just fallen victim to the most audacious fraud in science history.

  * * *

  Every scientist makes mistakes. Science functions by ‘failing forward’, constantly tinkering ideas, experiments and approaches to get things a little closer to right each time. Research fraud – faking your results, lying to yourself and the world – is the opposite of everything science stands for. When you’re caught (and you always are), it destroys your reputation, your colleagues’ reputation and your lab’s reputation. In physics, the best-known scandal is probably the work of Jan Hendrik Schön, who seemed to have made miracle breakthroughs in semiconductors that were nothing of the sort. When news of his scientific misconduct broke, it saw 28 papers in leading journals retracted.