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Once upon a time, before the days of computers on every desktop and in every bag, there were scanners. These were people, up to twenty at a time, who worked at scanning the results of physics experiments conducted in the particle accelerators of the US and Europe. From the 1960s until 1980, the scanners, mostly women, toiled day and night in the physics department of the Weizmann Institute of Science. Their job: to help discover and study the properties of subatomic particles and the forces that act between them.
“We all started out as young single women,” says Helen Katz, “and by the time we finished, we were all married and mothers. Now, as we are retiring from the Institute, many of us are grandmothers.” “It wasn’t that men weren’t hired,” according to Nitzhona Akshuti. “It was just that the women were the ones who stayed.” The story of the Weizmann scanners is more than the story of a group of hired workers who were trained to identify the tracks of elusive particles in image after image. It is also the story of a group of women who became fast friends over the years, celebrating marriages and births together and helping one another through hard times. As some point, they gave themselves the name “the scanners” (scanneriot in “Hebrish”). Even today, they are happy for an excuse to get together to exchange news and talk about their scanning days.
Beginning of an era
Scanning, as a job, began in the 1950s, when particle physicists began using a new apparatus to uncover the secrets of the particles locked up inside atoms: the bubble chamber. The late Prof. Gideon Yekutieli of the Weizmann Institute wrote in 1963: “Now, the era of the photographic plate is over, and a new one has begun: that of the bubble chamber. The laboratory landscape has changed accordingly. Microscopes and photographic emulsions have vanished. In their place have appeared scanning tables and special apparatus for measuring photographs, cine-camera spools and IBM punch-cards.”
Bubble chambers were large containers of liquid – usually hydrogen – kept under pressure just below the boiling point. The containers were attached to accelerators – for example, the SLAC linear accelerator at Stanford. In these accelerators, beams of such particles as electrons were shot at high energies through a target, causing new particles to come into existence. Those particles left tracks of tiny bubbles of heated gas as they sped through the liquid hydrogen. Each particle left a signature track, depending on its energy, mass and lifetime. Most of the particles were unstable: Some broke down into other particles within mere fractions of nanoseconds. So a new particle might be identified by the tracks of its secondary particles.
The bubble chambers produced moving films of the particle events in 3-D – that is, special high-speed cameras filmed the experiments from three angles. The results were then shipped to the Weizmann Institute in giant rolls of film that had to be analyzed, frame by frame, from all three angles, often two or three times to be sure that any findings were correct.
A demanding task
To be a scanner, one had first to travel to Jerusalem and pass a series of tests in the Hadassah Institute. “With all the tests they gave us, we thought we were being tested for air force pilot training,” says Anat Shaibin. Hand-eye coordination was important, as was attention to detail, good eyesight and the ability to work well in a team. Tova Presman remembers applying for the job when she was a new immigrant and still having difficulty with the Hebrew instructions. Helen, who was also undergoing the tests, helped her out.
Scanning was conducted in a darkened room; the scanners viewed their frames on special tables or, later, screens. Operating the apparatus took some skill and a certain amount of coordination: foot pedals and stick controls were needed to move the frames along, and coordinates had to be carefully noted. In less than a second, a practiced scanner could determine whether there were any particle tracks of interest among the patterns of lines and swirls on the image and move on. Some 35 years later, they can still hear the swooshes and clicks of the frames spooling past.
Yekutieli reported in the summer of 1963 that the Weizmann team had received 30,000 frames. The scanning capacity of one table, he said, was 200 pictures a day. Three days’ worth of experimental results – some 60,000-100,000 images – translated, back then, into two years of work for the scanners. With time, new equipment improved the scanners’ efficiency, and extra shifts were added to speed up the process and make better use of the equipment. By the time that Yaffa Berko was hired – in 1975 – some of the measuring was no longer done by hand but passed on to the computer operators. Still, the main job – scanning frame after frame for signs of the desired particle trace – remained a demanding yet repetitive task.
For many years, Prof. Yehuda Eisenberg headed the Weizmann physics group that employed the scanners. “He always treated us with respect, as a part of the team,” say the women. “We never felt that we had a different status than those with more education.” In fact, education and learning were no less important to the scanners than to the top physicists. Every Thursday the scanners would stop their work for a few hours and meet for lectures, including talks on the physics that produced the lines and circles on the frames.
The particle zoo
Prof. Uri Karshon began his career in physics around that time, getting his PhD at the Weizmann Institute in 1967. In that period, he recalls, the field seemed to be a “zoo of particles.” The underlying theory that would hold them together – now known as the Standard Model of Particle Physics – was still being hammered out. The Israeli scientists, as members of small international research groups, would travel to Stanford, Brookhaven in New York, Fermilab near Chicago and CERN in Europe to conduct the particle-beam experiments. In time the Standard Model solidified and became accepted. “In all the physics experiments done since, including the recent ones conducted at the giant LHC facility at CERN, nothing has been discovered that contradicts or disproves that model,” says Karshon. Among the theorists working on the Standard Model was Israel’s Prof. Yuval Neeman, who played a major role in laying the foundations of modern particle physics.
The particles that popped up in the Institute scans included such particles as pi- and K- mesons – particles made up of a quark and an antiquark; and resonances – particles that are extremely short-lived, even for the subatomic products of particle collisions. Karshon credits the scanners with exceptionally good work. As an example, he points to his own doctoral research, supervised by Prof. Gideon Alexander, which involved the collision of a neutral particle with a proton. Since neutral particles do not leave tracks in the bubble chamber, the resulting trace in the images was a very brief, tiny blip “appearing out of nowhere,” produced by the scattered proton, followed by two charged particles that decayed from the neutral one. These were very hard to see; but the resulting work, he says, was important. That paper is still cited today – a rarity in a scientific field that has seen so many changes. “It’s safe to say that without the work of the scanners, what I accomplished in my PhD research would not have been possible,” he says.
Sisters
In 1971, Hana Goldshtein was 19 years old. That was the year she came with her parents to Israel from Lithuania, which was then a part of the USSR. She had dreamed of becoming a musical conductor and had even started her studies, but now she needed to work and help support her family. Her parents’ only daughter, she recalls feeling isolated and lonely in her new home. But a short time after Hana began working in the scanning room, Nitzhona, whose family originally came from Yemen, “told me she was going to adopt me as a sister. This group of women has been family to me ever since. We helped one another through all sorts of hard times, and we are still close – sometimes closer than our real families,” says Goldshtein.
Anna Weisman also came to Israel from the former Soviet Union. Although she had an advanced degree in biochemistry, the only work she could find in the beginning was scanning. The women in the group, however, decided that she should have a job in her profession, and encouraged her to move on. Together, they found her a position in one of the Weizmann Institute labs, where she continued to work until recently.
Marvelous machines
Yekutieli wrote, back in 1963: “One day we hope to scan automatically… When we can teach the computer to detect forms and distinguish efficiently among them, a new chapter will open in data-processing… With the merest flick of a finger, we will start the operation, and after days, weeks or months, our marvelous machine will eject a completely finished work – all set for print.”
Indeed, during the 1970s, not only were computers starting to replace humans in jobs such as scanning, but particle accelerator technology was also changing. Instead of beams of particles aimed at a target, the new accelerators held two beams traveling in opposite directions, generating high-speed particle collisions. Instead of bubble chambers and film, new types of particle detectors were connected directly to computers that could automatically record collision events. This collider design is basically the same as the one used to build the LHC – the Large Hadron Collider – at CERN under the France-Switzerland border, which recently gave us proof for the existence of the Higgs boson, the final “missing piece” of the Standard Model.
As the scanning room was closing down in 1980, new opportunities were opening. The LEP – Large Electron-Positron Collider – a 27-km-long underground ring for particle physics experiments – was being planned. The Weizmann Institute was in on the project from the beginning, taking on the design and construction of the particle detectors. The scanning team members were offered jobs building the detectors.
Hana and Anat were the first to make the move, helping to build the prototypes. They were later joined by several of the others. “I started as a scanner, but I became a welder and ‘engineer’,” says Geula, with some pride. Other members of the group spread out over the Weizmann Institute, many of them going on to various administrative positions. Now, most of them have retired, but they still feel the Weizmann Institute is their second home. They speak of a sense of belonging – both to the Institute and to the work. Through the long hours of scanning, they say, they took pride in the importance of the work – in the contribution they were making to the advancement of science. Nitzhona has even, on a trip to the US, gone to visit the SLAC facility at Stanford, to see where all those frames she scanned originated. And they point out that the experience of scanning had some positive effects on their daily lives. “For instance, we are all better drivers,” says Geula. “We immediately pick out the important details in our field of vision.”
Today, says Karshon, another era may be closing for particle physics, with the final piece of the Standard Model in place, but a new one will be opening, maybe even when the LHC starts up again. “We know there are other particles out there – beyond those in the Standard Model – that we can’t yet see,” he says. Hana Goldshtein is one of the few former scanners remaining at the Institute. She still works in the Mexico building on campus, where particle detectors are today being assembled for the LHC, which replaced the LEP collider in its tunnel – though she has moved on from assembly to administration. Among other things, she is helping work out the details for a new type of detector they are building. “But that,” she says, “is another story. When I think back on my days as a scanner, even with all of the hard parts – those were the best days of my life.”
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