Albert Ghiorso is a man who likes to decorate -- and has the power to dictate the feng shui of perhaps the most famous research institute in history. At the Lawrence Berkeley National Laboratory's Center for Beam Physics, in the conference room that bears his name, Ghiorso has posted his personal collection of oil paintings by Mel Brenner. Along one wall, however, a more pragmatic graphic display yellows beneath a glass frame: an ancient chart of isotopes, begun in 1948 by Ghiroso's longtime collaborator Glenn Seaborg, preserved at the former's request. As Seaborg and his colleagues discovered legions of heavy elements in the '50s, '60s, and '70s, the chart began to overflow with the new additions. Finally Seaborg was forced to cram Element 101, the last one that could fit, into the upper right-hand corner.
Downstairs in Ghiorso's personal laboratory, a second wall boasts mementos from his life. There's another Brenner oil hanging above aging clips from the New York Times and the Wall Street Journal, as well as a startling black-and-white photograph of the infamous 1969 riots when then-governor Ronald Reagan ordered helicopters to tear-gas captive protesters on the UC Berkeley campus. Ghiorso's son shot the picture of the helicopter's undercarriage just moments before the gas wafted down upon him.
This wall is much more than merely a place to display Ghiorso's personal effects, however -- it also contains the centerpiece of his life's work. Stretching from one end of the wall to the other hangs the vast "Chart of the Nuclides," a graph detailing the structure of every atomic nucleus that has ever been found to exist -- or coaxed into existence -- in the universe since the dawn of nuclear science. The chart hinges on two axes: The vertical axis refers to the number of protons in a nucleus, the critical factor which distinguishes, say, carbon from oxygen and dictates the properties of an element; the horizontal axis refers to the number of neutrons, which determines the different isotopes of each distinct atom. Documented on this chart are the nuclear cores of everything in the universe that has organized itself into atomic structure from simple hydrogen, in the lower left-hand corner, to the nameless and theoretical "superheavy" elements in the upper right.
Ghiorso began this chart thirty years ago, filling it as far as he could and leaving a void in the upper right-hand corner. This nuclear ellipse represented everything that high-energy nuclear physics had yet to discover but that Ghiorso knew lay just beneath the horizon, waiting for him. It represented the future. In the next three decades, Ghiorso played a personal role in filling in that gap, helping to discover the heavy elements rutherfordium, dubnium, and seaborgium -- the last of which he named after his famous peer. "I started the idea of naming elements after people," he says with a grin. "When I named element 106 after Seaborg, he said to me, 'You know Al, I think that's the greatest thing you've ever done.' Glenn had a very big ego, you see, but he was also a great scientist." Altogether, Ghiorso is credited with having discovered at least twelve elements, more than anyone else in history.
Put simply, Albert Ghiorso is a giant in his field, on a par with Andrei Sakharov, Robert Oppenheimer, and Ernest Lawrence. Now 86 years old, he has been in a state of semiretirement for twenty years, but still contributes to striking breakthroughs in nuclear physics. Early in 1999, Ghiorso designed a groundbreaking device known as the Berkeley Gas-filled Separator (BGS), a means to separate atomic particles by mass with an unprecedented degree of clarity. Mere weeks after the BGS came online, a team of Lawrence Berkeley Lab scientists led by Ken Gregorich and Darleane Hoffman used it to discover two nuclides that had never before been seen: elements 118 and 116. It was one of the most spectacular and internationally celebrated discoveries in the field of high-energy nuclear physics, and it allowed Ghiorso to post two more elements in the upper right-hand corner of his chart. In his honor, the research team tentatively announced that they planned to dub element 118 "Ghiorsium."
But it was never to be. On July 27, that same research team was forced to retract its discovery, and Ghiorso's name never made it onto the Periodic Table. Something had gone terribly wrong.
In 1940, Edwin McMillan and Ernest Lawrence discovered the elements neptunium and plutonium and transformed Berkeley's radiation lab into the undisputed international center for the discovery of new elements. Over the course of the next 34 years, Lawrence, Seaborg, Ghiorso, and Hoffman discovered a host of new elements, reorganized the Periodic Table, and netted three Nobel Prizes; it was their work that made possible both the atom bomb and nuclear energy, forever changing the global balance of power.
But as they pushed back the boundaries of the known universe, they began to worry that their work would eventually stall. The Chart of the Nuclides seemed to have a brake built into it; the heavier the element "discovered" or -- perhaps more accurately -- created by the LBNL team, the less stable the nucleus, until the heaviest elements existed for mere wisps of time before falling apart. While the longest-lived isotope neptunium has a half-life of 2.14 million years, the half-life of the longest-lived isotope of meitnerium, which was discovered in 1982 and is the last element to be named, is just 70 milliseconds. Even if scientists could create heavier elements in a laboratory setting, what good would come of making something that vanished as soon as they saw it? Starting in the '70s, a team of German scientists overtook LBNL researchers as the leaders in discovering new elements, but they also worried that their work had hit a dead end. Researchers around the world were beginning to admit that perhaps there was a limit to the universe of atomic structure.
Then about seven years ago, this once revolutionary but now faded field got a new lease on life. Since the '60s, a theoretician at the Berkeley lab named Wladyslaw Swiatecki had been arguing for the existence of "superheavy elements," whose nuclear structure would be far more stable than the heaviest "transuranic" elements discovered so far. (Transuranic elements are those that are heavier than uranium and virtually never occur outside the laboratory.) Swiatecki's theories proposed that well beyond the current boundaries of the Periodic Table there exist "islands of stability," elements whose half-lives could be measured not in milliseconds, but years or centuries. All we had to do was leapfrog over this "sea of transuranic instability," Swiatecki claimed, and we would stumble upon entire species and genera of new matter, whose properties and attributes we could only guess at -- and whose applications as fuel or terrifying new weapons were unimaginable.
In 1997, the prospect of landing on these islands of stability never seemed brighter. Armed with a new crop of fusion models, state-of-the-art detection equipment, and an infusion of young, enthusiastic scientists, research teams in Germany, Russia, and Berkeley began a little-noticed but fiercely competitive race to discover elements 114 and above, which would theoretically land us on the beach of Swiatecki's island. Lawrence Berkeley Lab, Germany's Institute for Heavy Ion Research (GSI), and the Joint Institute for Nuclear Research in Dubna, Russia, all began smashing particles together in a race to ultimately create an isotope of element 126, the theoretical peak of superheavy stability and the apogee of a new, glorious swath of undiscovered elemental territory.
In the spring of 1999, LBNL researchers thought they had come closer to this goal than ever. When they fired a beam of krypton particles at a lead target inside the lab's famed 88-inch cyclotron, the subsequent energy readings led them to believe that, for less than one millisecond, element 118 had come into existence before decaying into element 116, 114, and down the chain until reaching the relatively stable state of seaborgium. Berkeley came to believe that, for one brief instant, they had come within reach of an entire virgin continent of matter, a clan of ions and nuclides and probability clouds that to their knowledge had never before existed in the universe.
But they were wrong. It took two years of additional research, but finally Ken Gregorich's team was forced to admit that somehow, someone had misread the data, and no one had caught the mistake. Up in the Berkeley Hills, amid the tangled eucalyptus groves and particle accelerators, the nuclear physicists of Lawrence Berkeley Laboratory had pushed back the terra incognita of the universe, only to have it spill around their ankles once more.
It's fair to say that sixty years ago, Albert Ghiorso stumbled into what would become a stellar career as a nuclear physicist. He didn't rise through the ranks of academia; indeed, his credentials consisted of nothing more than the Bachelor's of Science degree in electrical engineering he received from UC Berkeley in 1937. He first met Seaborg while working for a company that built Geiger counters. "In the spring of 1942, I got a letter from Albert asking whether I would be willing to recommend him for some kind of job in the Navy," Seaborg wrote in The Transuranium People, the official LBNL account of the early years of heavy element research. "Actually, I didn't know Al very well. This is one of those cases where our wives took over. My wife, Helen, who had worked ... as Ernest Lawrence's secretary, was a very good friend of Al's wife, Wilma, who was working here in the laboratory.... When the letter came, Helen told me, 'You hire this guy.' ... He wasn't easy to convince; he was afraid that all I had in mind for him was to continue building Geiger counters."
Seaborg had already achieved some renown as part of the team that discovered plutonium, but he was soon onto bigger and better things. By 1944, Ghiorso was working side by side with Seaborg on his latest project: the creation of elements 95 and 96 -- which would eventually be named americium and curium -- at the Metallurgical lab in Chicago. The tools for colliding elements and measuring the results were hopelessly crude by modern standards, and Seaborg was further distracted by his work extracting and purifying plutonium for the Manhattan Project, but eventually, he was able to set up a series of experiments at the cyclotrons at the University of Washington and the UC Berkeley Radiation Lab. Seaborg's team bombarded an isotope of plutonium (then the heaviest element known to man) with deuterons, or hydrogen nuclei with two neutrons. Over the next few months, researchers repeated the experiments, hoping to find the telltale signs that the two particles had fused into element 95, but found nothing. On July 8, 1945 Berkeley researchers tried bombarding plutonium with a helium ion instead, and over the course of the next few months were finally able to determine that the experiments had produced elements 95 and 96.
Seaborg intended to announce his discovery at a symposium of the American Chemical Society, but five days before the symposium, he served as a guest on Quiz Kids, a Chicago radio game show for children. While on the air, a child named Richard casually asked Seaborg, "Have there been any other new elements discovered, like plutonium and neptunium?" "Oh yes, Dick," Seaborg blurted before he realized what he was doing. "Recently there have been two new elements discovered -- elements with atomic numbers 95 and 96 out at the Metallurgical Laboratory here in Chicago. So now you'll have to tell your teachers to change the 92 elements in your schoolbook to 96 elements." Thus was one of the most remarkable breakthroughs in modern science announced to the world.
"When we discovered americium," Ghiorso remembers, "reporters were asking, 'What earthly good is this stuff going to do?' And we said, 'Oh, it's just because of our scientific curiosity.' Where is that element right now? It's in every household in the United States. It's in your smoke detector, one microcurie of americium."
Amid the excitement of these discoveries, Seaborg and Ghiorso confronted a bizarre conundrum: what to call the new elements. The previous three elements had been named after the planets in the outer limits of the solar system, but that option was exhausted with the naming of plutonium. Now, researchers had to come up with new rules to establish the nomenclature of heavy elements. Should the elements be named in honor of renowned scientists? Should they indicate where the discoveries had taken place? One researcher even suggested the two elements be named "pandemonium" and "delirium," in recognition of the frustrating, chaotic efforts to create and detect them.
Over the course of the next four decades, as more and more elements were discovered, the campaign to name them would be caught up in Cold War geopolitics. When LBNL scientists discovered element 101 in the '50s, for example, the researchers decided to name it "mendelevium," after the Russian chemist Dmitry Mendeleev. "At the 1955 Atoms for Peace Conference in Geneva," Ghiorso wrote in The Transuranium People, "the French chemist Haissinsky told me that our naming of element 101 in honor of a Russian scientist had probably done more good than anything that John Foster Dulles had ever done!"
By the mid-'50s, Seaborg's research team had attracted such international notice that, like Oppenheimer and Edward Teller, they found that they and their work had become inextricably bound up in Cold War diplomacy. They were no longer merely physicists pushing back the boundaries of the Periodic Table -- their work lent them a species of international renown and moral authority, a bully pulpit amid the diplomacy of nuclear brinkmanship. In 1951, Seaborg was awarded the Nobel Prize, but he and his colleagues were too busy grappling with a new dimension to their work to enjoy it. As a member of the Atomic Energy Commission's General Advisory Committee, Seaborg was drawn into the controversy over whether to build the hydrogen bomb, which ultimately cost Oppenheimer his security clearance. In addition, the loyalty oaths of 1949 cast a pall over the research lab, and Ghiorso nearly lost his job because security personnel considered him a subversive.
"Al's success in science has stemmed from the fact that he has always been an original and creative thinker," Seaborg wrote in his autobiography Adventures in the Atomic Age. "His unwillingness to adopt a 'go along to get along' attitude and his undiplomatic insistence on pointing out the ludicrous nature of some of the security regulations only made the security people more intransigent.... The security people complained that before the war his wife Wilma had been a communist. Even if that had been true, during the Depression years, when capitalism had thrown millions out of work on what appeared to be a permanent basis, it was not unusual for people to have socialist or communist leanings.... By the early 1950s I'd worked and socialized with Al on a daily basis for a decade. I never detected a hint of anything that would make one suspect disloyalty, yet sometimes I had to fight like hell to keep the AEC security people from revoking his clearance."
Although a liberal Democrat, Seaborg adopted a discreet approach to politics, and his laboratory enjoyed an uninterrupted wave of patronage and funding. In 1947, the lab's 184-inch cyclotron came online, and Seaborg and Ghiorso could now accelerate deuterons to 180 million electron volts. LBNL's bevatron followed in 1953, and in 1957 the heavy ion linear accelerator, whose decommissioned carcass still lies next to Ghiorso's lab, could accelerate particles as heavy as neon. Finally, in 1961, the lab's 88-inch cyclotron, which would be used in the experiment to produce element 118, came online. Armed with these tools, Seaborg and Ghiorso discovered a rash of new elements: berkelium in 1949, californium in 1950, einsteinium and fermium in 1952, lawrencium in 1961. When John F. Kennedy took office that year, he appointed Seaborg to chair the Atomic Energy Commission, a post he was to hold for a decade.
But as the '60s began to wind down, the prestige associated with discovering heavy elements began to wane in America, and a research team in West Germany began to overtake the lab. The Germans built an enormous particle accelerator and pioneered a technique known as "cold fusion," which in the '80s would lead to a series of breakthrough discoveries. At the same time, the Department of Energy was showing less enthusiasm for Seaborg's original line of inquiry, and the lab began to diversify its scope of research, until today the work that was once the centerpiece of LBNL's mission is a lonely stepchild. The more advances Seaborg, Ghiorso, and Hoffman made in nuclear science, the less there was to learn, and the less interested the lab's directors were in pursuing them.
"Nuclear science was much more mysterious than it is today, we really hadn't figured anything out about it," says Pier Oddone, the deputy director for research at LBNL. "Today, the laboratory's centerpieces are much different: It's the work that we do with X-rays, and a huge program with biology and material sciences, trying to understand at the atomic level how materials are put together. Investigating protein structure, for example, is much, much bigger than looking at heavy elements. In a $400 million lab, I'd say there's maybe a million dollars worth of work in that line today."
Ghiorso believes that the lab lost a critical opportunity to stay at the cutting edge of heavy element research in the late '60s when the perverse national priorities of the era wiped out the budget of the LBNL heavy element team. "I'll tell you what the key thing was here: the Vietnam War," he says. "We were designing a machine here called the Omnitron, and it was going to be the first complicated accelerator in the world. It would still be the best machine in the world today, and if we had built it, we would have gone all the way. But we estimated that the Omnitron would have cost $30 million at the time. During the Vietnam War, we would shoot $30 million [in ordnance] every shift, three times a day, every day. And there was nothing we [at LBNL] could do about it. If I'm gonna blame anyone, I'm gonna blame Johnson's and Nixon's war."
Of course, it didn't help that conventional wisdom within the nuclear science establishment of the '60s predicted a natural end to heavy element research. In 1964, Swiatecki first published his "islands of stability" theories, but most researchers suspected that we had reached the limit of new elements waiting to be discovered. In 1976, Ghiorso himself told the New York Times that he didn't believe in the existence of superheavy elements, even as he was overseeing the laboratory team that was trying to find them.
To understand Ghiorso's skepticism, you have to understand the internal nature of an atomic nucleus, which is perhaps best described as suffering from multiple personality disorder. The nucleus of every atom is composed of neutrons, which provide mass but carry a neutral charge, and protons, which carry a positive charge. It is the protons that are the key factor in determining the element's distinctiveness and its atomic number; a carbon atom, for example, is defined by the fact that it has six protons in its nucleus. But protons don't actually want to be in nuclei. According to the theory of electric repulsion, particles with like charges repel one another, and while the electrons in the atomic orbital shells are separated from each other by comparatively vast distances, protons are crammed together in nuclei, even as they fight to get away from one another.
What keeps protons from splitting a nucleus apart is a phenomenon known as strong nuclear force. Each proton and neutron (which are collectively known as nucleons) are composed of smaller particles known as quarks. The forces that hold the quarks together in a nucleon create a residual force that causes nucleons to attract one another. When a batch of neutrons and protons are crammed close together, strong nuclear force overrides electric repulsion and keeps the structure of a nucleus intact. But strong nuclear force has a very short range, while the range of electric repulsion is much longer.
This is why Seaborg and Ghiorso had to use particle accelerators to discover, or build, heavy elements. Seaborg's team would take a light element like helium and use radio waves to infuse it with energy. That energy would be expressed kinetically, i.e., the element wanted to move very fast. They then steered it down a path and collided it into a target, typically a thin strip of a heavy element like plutonium. The protons in plutonium and helium don't want to get anywhere near each other, but Seaborg and Ghiorso infused the helium with so much energy that it overrode the mutual repulsion and got just close enough to the plutonium nucleus to come within range of the strong nuclear force. At that moment, the two nuclei would latch onto one another and fuse.
This creates an interim particle known as a compound nucleus, which churns and seethes with excess energy, literally warping its own nuclear architecture. (It also happens to be moving at an incredible rate of speed.) That excess energy can be expended in one of two ways: Either the compound nucleus spits out a neutron and settles down into a relatively stable state, or it splits in two in a process known as fission. In the lab's early glory years, Ghiorso and Seaborg's team struggled to infuse a light element with just enough energy to fuse the two nuclei together, but not so much that it would immediately split apart.
"You have to understand that the nucleus is very small compared to the size of the atom, and it's positively charged," says Rollie Otto, the director of LBNL's Center for Science and Engineering Education. "So the energy it takes to push one nucleus that close to another gets larger and larger the closer you get. Because strong nuclear forces are only short-range, you don't feel any attraction initially, you just keep pushing them down, and it takes millions of electron volts to get them that close. When they finally get close enough, the nuclear forces take over, and they amalgamate just like two liquid drops. In fact, a liquid drop is a good way to think about the nucleus. If you had two liquid drops, and you got them to touch, the surface tension would cause them to become one big drop.
"But now that compound nucleus is very excited, it's got a lot of excess energy in it. Now the question becomes, how can that nucleus survive? The lab spent its time trying to get it to survive by spitting off a neutron [rather than splitting in the process of fission]. So what [Ghiorso] and his team did over the years is find that delicate balance of getting them just close enough to fuse, but not give them so much energy that they end up falling apart. The energy level is very critical. Too little, and they don't get together. Too much, and they break in two."
As Seaborg and Ghiorso's team produced ever-heavier elements, they began to run up against a brick wall. The more protons they crammed into a nucleus, the more their electric repulsion tore at the nuclear structure. Strong nuclear force could only compensate so much, especially as the nucleus swelled in size, and nucleons on the edge of the nucleus edged out of the range of their sisters. Seaborg and Ghiorso tried to compensate by creating heavier isotopes, in hopes that additional neutrons would dilute the power of electric repulsion. But by 1974, when LBNL researchers discovered seaborgium, their last confirmed element, that particle had a half-life of just twenty seconds before decaying. They were finally confronted with what seemed to be the natural end of the spectrum of elements in the universe, and the lab's illustrious work appeared to be over.
Still, throughout the '70s and '80s, Swiatecki's theories continued to tantalize high-energy physicists around the world. If what he postulated was correct, the seemingly impermeable barrier of ever-dwindling half-lives was merely a rough patch that researchers had to slog through in order to find regions of nuclear stability unglimpsed by human beings -- a roster of new, superheavy elements that could last for millennia. All they had to do was find the right combination of isotopes to collide.
A useful analogy can be found in chemistry, in examining the so-called "noble" gases. According to atomic theory, protons and neutrons inhabit the nucleus, which is surrounded by electrons in what are variously called orbital shells or probability clouds. Each shell has a specific energy level associated with it and wants to have a certain number of electrons within it; the first orbital shell, for example, wants to have two electrons, and if that shell is unfilled, the hydrogen or helium ion will seek out an electron and absorb it. This is the essence of what is called "covalent bonding," and it's the reason why oxygen gas consists of two atoms of oxygen bonded together. Each oxygen atom hungers for two additional electrons, and when two atoms are close enough, each will latch onto an electron in the other's outermost shell and treat it as its own, thereby locking it into a symbiotic relationship with its twin. But the so-called "noble gases" such as neon, argon, and krypton are elements whose electron shells are completely filled; they have no such desire to seek out another electron and are dubbed "noble" because their behavior is aloof. They have achieved stability -- they don't want to change.
In a similar fashion, nucleons are organized into shells within the nucleus -- and want to fill up their own shells. There are separate, concentric shells for protons and neutrons, and once they are filled up, the nucleus achieves a certain nonreactive quality. The proton shells of helium, oxygen, calcium, and tin, for example, are all completely filled; they have accumulated what is known as a "magic number" of protons and have achieved a certain crystalline equilibrium; protons are arranged within each shell in such a way as to set the electric repulsion of each particle against one another, and the protons are held in an abeyance that lends a particular stability to the nucleus. When the shells of both protons and neutrons are filled, the nucleus is said to be "doubly magic," and particularly stable. Creating these doubly magic isotopes outside the known limits of the Periodic Table is at the heart of the quest for superheavy elements that continues to this day.
"Magic numbers provide the same kind of stability as closed electron shells," says Lee Schroeder, the director of LBNL's Nuclear Science Division. "With that abeyance [of protons], you have a unique situation where the nucleus doesn't want to do anything or have things done to it, you have a nice closure on both the protons and the neutrons. In nuclear physics, the letter Z refers the number of protons in the nucleus, and as you push Z further [into the heavy elements], you have this peninsula running out, and then you go into deep water, and then there's this island that magically rises out there, which according to theoretical musings has a kind of stability. It was just a question of developing the tools that allow you to push out into that regime where you might see it."
In the mid-'90s, a convergence of events sparked a little-known but dramatic contest to finally reach Swiatecki's islands of stability. Lab engineers were perfecting a new generation of equipment to detect the signature "alpha decay chains" of superheavy elements; theoreticians developed new models of isotopic collision that might make such elements possible; and an incoming class of young researchers breathed new life into the endeavor. By 1998, three research teams -- the GSI lab in Germany, the LBNL team, and a consortium of researchers from Lawrence Livermore and Dubna, Russia -- were racing to put together experiments that would result in the discovery of an isotope of element 114, one of the "doubly magic" isotopes that could last as long as centuries. Since the Nixon years, GSI scientists have been the undisputed masters of heavy element work, discovering five of the last six known elements. For LBNL researchers, the race presented a chance to finally regain dominance in the field of heavy element research, dominance it had ceded more than twenty years ago. "Every island has a shore, and discovering elements 112 and 114 would be kind of like landing on the shore of this thing," Schroeder says.
In January 1999, just months after Seaborg suffered the stroke that ended his life, researchers with the Dubna/Livermore consortium announced that after bombarding plutonium with a calcium isotope for forty days, they had observed a single decay chain that fit the pattern predicted by the creation of element 114. After more than a month of bombardment, the Russians had seen just one atom of the element -- but it looked, nonetheless, like the Russian researchers had finally taken the first step onto the magic island, and, with this discovery, had put the world on notice that they were now serious players in the discovery of heavy elements.
Berkeley scientists immediately began preparing to repeat the experiment in order to confirm the discovery, but soon realized that they didn't have enough raw material to proceed. Fortunately, Polish theoretician Robert Smolanczuk was working at the lab on a Fulbright scholarship and proposed a different project to researcher Darleane Hoffman: Now that Ghiorso's Berkeley Gas-filled Separator was up and running, the lab could test Smolanczuk's prediction that firing high-energy particles of krypton gas at a lead target would produce not element 114, but element 118. Far beyond stepping onto the island's shore, Smolanczuk suggested, if his theory was correct the lab would have hiked deep into the island's brush.
Two things about this experiment were particularly appealing: Neither the particle nor the target was radioactive, which reduced the health and safety precautions; and Smolanczuk's model predicted results in just a few days, which promised not to monopolize use of the 88-inch cyclotron for very long (so many research teams compete for "beam time" on the cyclotron that for every project approved, two are rejected). In addition, Berkeley researchers feared that unless they ran Smolanczuk's experiment immediately, the Germans or the Russians would beat them to the punch yet again. "Smolanczuk had had some success with this model, and that gives you a little bit of a backbone," Schroeder says. "Well, here's a possible pathway, let's go off and try it." On April 8, 1999, researchers Ken Gregorich, Darleane Hoffman, and Victor Ninov fired up the cyclotron and went to work.
The key factor in any particle accelerator is a simple tenet of physics: A charged particle moving in a magnetic field will always bend in a direction that can be predicted. Line up enough magnets in just the right sequence, and you can move a charged particle any direction you want. So the first step is to take a particle and apply a charge to it -- in this case, by stripping electrons from particles of krypton to create positively charged ions. How do you strip electrons from krypton? You cook it.
"Krypton starts as a gas," Schroeder says. "You put it into an oven and heat it up, giving it random thermal motion, which eventually starts spitting some electrons off. You then apply a voltage by injecting the gas into a device called an 'electron cyclotron resonance ion source.' There are enormous radio frequency fields running around, which further create a plasma. What you're trying to do is get as many electrons off there as possible. Then you spit it out of the ion source. You then have krypton with a particular charge, which you then guide into the cyclotron."
Imagine a cyclotron as a record with a skip in it. Researchers deposit charged krypton particles in the center of the record and use magnets to move it in a circle. There is a continuous field of radio waves bisecting the cyclotron at a fixed position -- the skip -- and every time the particle passes through the field, it gets a jolt of energy, moves a little faster, and edges farther from the center, out toward the periphery of the cyclotron. It passes through the scratch again, gets more energy, and picks up speed, until it is moving at the velocity you need to collide it into your target. Once again using magnets, researchers then steer it out of the cyclotron and aim it at the target.
"You've got a positively charged krypton ion injected axially, which means down the center, and every time it goes past a gap where there's a radio frequency field, it gets a voltage kick," Schroeder says. "So when it crosses that gap, an electric field appears and gives it a higher energy, it gets a little voltage increase, and as it does it moves to a higher orbit. So it starts in the center and spirals out, until there's a little hole where it comes out. In the cyclotron, this isn't just a little blurp of stuff. You have a continuous beam of particles extracted from the machine, and with magnets, they are delivered to your target area."
In the experiment to produce element 118, the target was a thin strip of lead. But it wasn't merely an inert piece -- the lead was deposited on a thin foil that was constantly spinning. Researchers tried to collide a krypton nucleus into a lead nucleus, but with such infinitesimal particles, the odds of smacking them exactly together are remarkably slim. Typically, the krypton interacts instead with the electron cloud surrounding the nucleus, and this generates heat -- enough heat, over time, to ruin the experiment. "This is a lot of what's called beam power, and as the krypton goes through the lead foil, it's constantly knocking electrons off until it finally collides with the nucleus," Schroeder says. "There's the core nucleus, but there's also this electron cloud around it, and there's a very high probability of knocking electrons off, which causes it to loses energy. That amount of energy is not very much, when you take into account the fact that it's being lost in this lead multiplied by so many particles, that's a lot of heat being generated. So they have to have a target that's spinning, so you're not hitting one isolated piece constantly. The lifetime of the target is a big consideration in this."
For eleven days, Gregorich's team stripped electrons from krypton gas, spun it around the cyclotron, and fired it at a spinning foil of lead. Then on April 19, Gregorich called Hoffman into his office and showed her some startling results. Victor Ninov had been going over the energy levels recorded by the collision and found three alpha decay chains. (Lab researchers never actually detect such heavy elements, merely the alpha particles that spin off when heavy elements decay into more stable matter.) According to the data, they had produced exactly three atoms of element 118. Berkeley researchers appeared to have cracked the mystery of the superheavy elements and, after a drought of more than twenty years, planted their flag on the firm soil of the magic island. The experiment worked so perfectly, the results were so accurately predicted by Smolanczuk's model, that Ninov exclaimed, "Does Robert talk to God or what?"
When Gregorich's team published the results of its experiment in Physical Review Letters, it caused an immediate sensation. Secretary of Energy Bill Richardson called it a "stunning discovery, which opens the door to further insights into the structure of the atomic nucleus," while others suggested that the Berkeley researchers could be on the "road to the Stockholm." Scientists at Germany's GSI lab began the process of confirming the lab's work, meticulously replicating the experiment and searching for alpha chains. Soon, troubling news was leaking back to the Lawrence lab: GSI couldn't find element 118 despite weeks of work. Scientists at the GANIL heavy-ion research lab in France and at Japan's Institute of Physical and Chemical Research also came up with nothing. At first, LBNL researchers thought that because of the rarity of the element, even the slightest change in the equipment could ruin the results; their discovery might still stand if they could repeat the experiment. The second time the experiment was run, however, element 118 never showed up.
Gregorich's team dug up its old data and reanalyzed the results of the first experiment. Soon the awful truth began to emerge: No one could find the original chain of alpha decay. It had just vanished. Had someone misread the data? Had the instruments failed? The Lawrence Lab convened a technical committee to find out what had gone wrong, and the results of the investigation are still pending. Meanwhile, Gregorich's team had to bite the bullet. On July 27, they retracted their announcement. Element 118 was gone. "I'm glad Glenn didn't live to see this," Ghiorso says. "Because if he had lived, he probably would have become a coauthor, just because we're sentimental and we would have included him. It would've killed him to find out he was wrong. None of us are happy about it; we don't like to make mistakes. But if you do make mistakes, you have to admit them as soon as you find out."
The retraction was an international embarrassment, a deeply disappointing moment for the Berkeley researchers, some of whom had been with Seaborg's original team in the lab's glory years. Now, when their life's work is written, an awkward coda will haunt them at the end of their careers.
But such is the nature of the work they have chosen, and so Ghiorso, Gregorich, Hoffman, and Ninov will soldier on, searching for that elusive Magic Island of Stability. At the moment, the world of nuclear physics is abuzz with word that the Dubna team has detected a few scant atoms of Element 116; if confirmed, the Russians will fairly own the field of superheavy research, and we will be at the precipice of a brave new world on the other side of the Periodic Table. "They've got pretty damn good evidence that they've found 116," Ghiorso says. "It's too early to give them the credit -- in fact, they haven't demanded the credit yet. But as far as I'm concerned, the Russians have topped everyone. That was the prize, you see. In fact, Georgi Flerov had a polar bear fleece, this beautiful white fleece, and he used to tell me, 'That's for the first person who discovers superheavy elements. And I wanted to tell [the Russian team], 'Well, if that fleece is still around, you get it.'"
Witnessing such breathtaking events has been the currency of Albert Ghiorso's career. In 1942, he was a glorified techie, tinkering with circuit boards; in his sixty-year career he has stood atop the world of high-energy nuclear physics, stared down McCarthy-era witchhunters, and been witness to countless quiet moments when paradigms have shifted and the world changed shape. This time, he watched his colleagues commit an international blunder, an error so prominent that when a panel of Department of Energy officials visited the lab last month for the cyclotron's annual review, the missteps of Element 118 were on everyone's lips. But Ghiorso's seen these moments before, and he knows that in the march of time, this too shall pass.
"When I started working with Seaborg, I was just maintaining his Geiger counters. I didn't even consider myself a scientist, and I was really blown over when we found element 95, and Seaborg came around and said, 'You know, you're gonna be the coauthor of the discovery of that element.' I said, 'Who, me? I'm just a technician.' I'll tell ya, it's just as exciting now as it ever was."
Posted next to Ghiorso's Chart of the Nuclides, hovering somewhere above the isotopes of scandium and titanium, is a yellowing ink print, etched in the classic style of socialist realism. A steadfast man, surrounded by the inky black of the night sky, holds a small lantern in the palm of his hand. Twenty-five years ago, Georgi Flerov, the physicist who directed the Soviet Union's atomic bomb project in 1948, sent Ghiorso this print after an international team confirmed his discovery of rutherfordium. Inside the lantern's flame, Florov has penciled in the atomic number 104. In the margin underneath, he has written, "Ghiorso will finally see the light!"
Seven Days - March 22, 5:57 PM
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