Winston
Lorenzo von Matterhorn
- Joined
- Jan 31, 2009
- Messages
- 9,560
- Reaction score
- 1,749
Why Physicists Put a Ferret in a Particle Accelerator
Felicia had a job to do.
2 Apr 2019
https://www.atlasobscura.com/articles/felicia-ferret-particle-accelerator-fermilab
Back in 1971, the design was a little different; for one thing, the injector and recycler rings didn’t exist. What did was an accelerator four miles around called the main ring. It was outfitted with magnets, which guide the beam through the accelerators: “774 dipole magnets—which steer the particle beam—and 240 quadrupole magnets—which focus the beam,” as the physicist Ryuji Yamada, who designed the dipole magnet, recalled.
These aren’t fridge magnets: Each is 20 feet long and weighs nearly 13 tons. At first, just two magnets failed when the glass fiber insulation around their coils broke. That soon became two a day. Over the next several months, the team replaced 350 magnets.
Yet on June 30, 1971, they managed to send a beam of particles all the way around the ring for the first time. By August, they sent one around 10,000 times. But when they tried to accelerate the particles above seven BeV, the magnets shorted out.
Yamada finally realized the cause: metal slivers left behind when they cut into the vacuum tubes. “So when the magnets were excited to a higher field,” he wrote, “they were pulled inside the magnet gap, stood up and stopped the beam, because they were slightly magnetic material.”
They had to get the slivers out. But how?
Robert Sheldon, a British engineer who’d been brought on to NAL to find “shortcuts and money-saving ideas,” suggested a ferret, equipped with a cleaning tool, could do the job, scampering through the vacuum tubes as if flushing rabbits out of a warren.
The ferret arrived by special delivery from the Wild Game and Fur Farm in Gaylord, Minnesota. At 15 inches long, she was the smallest ferret they’d had. Her fur was brown and black except for white patches on her face. They called her Felicia. She cost $35.
They placed a custom collar around Felicia’s neck and a diaper around her rear; ferret poop in a tube would stop a proton, too. They attached a string to the collar. Felicia was to bring the string from one end of a tube to the other. Then they’d attach a cleanser-dipped swab to the string and pull it through.
The NAL staff doted on Felicia, feeding her chicken, liver, fish heads, and raw hamburger—her favorite. Some employees even took Felicia to their home for the night when the mink farm she generally bunked at had no room for her.
Meanwhile, the engineer Hans Kautzky created a “magnetic ferret” to deal with the debris in the main ring. He attached a dozen Mylar disks to a stainless steel rod, along with a flexible, 700-meter stainless steel cable—the equivalent of Felicia’s string—and a metal-attracting permanent magnet—the counterpart to the cleaning swab. He shot the device through a section of the main ring with compressed air. “With 12 operations, we could make it around the entire ring,” Yamada wrote. “This way we could clean the whole vacuum pipe, though not perfectly.”
But it worked well enough, because over the next several months, the team steadily turned up the energy levels without shorting out the system, and on March 1, 1972, they got the accelerator to reach the target energy of 200 BeV.
After a dozen runs through the Meson Lab tubes—which, when joined, grew too long for her comfort—Felicia went into semi-retirement, and spent most of her time as a pet on the mink farm. One night the following spring, she was at the home of Charles Crose, a NAL employee, when she fell ill. Crose took her to a vet the next day. Under medical care, she briefly rallied, but within a couple of days she died, on May 9, 1972. A necropsy revealed a ruptured abscess in her intestinal tract.
Felicia emerges from a 300-foot-long vacuum pipe at Fermilab:
Felicia had a job to do.
2 Apr 2019
https://www.atlasobscura.com/articles/felicia-ferret-particle-accelerator-fermilab
Back in 1971, the design was a little different; for one thing, the injector and recycler rings didn’t exist. What did was an accelerator four miles around called the main ring. It was outfitted with magnets, which guide the beam through the accelerators: “774 dipole magnets—which steer the particle beam—and 240 quadrupole magnets—which focus the beam,” as the physicist Ryuji Yamada, who designed the dipole magnet, recalled.
These aren’t fridge magnets: Each is 20 feet long and weighs nearly 13 tons. At first, just two magnets failed when the glass fiber insulation around their coils broke. That soon became two a day. Over the next several months, the team replaced 350 magnets.
Yet on June 30, 1971, they managed to send a beam of particles all the way around the ring for the first time. By August, they sent one around 10,000 times. But when they tried to accelerate the particles above seven BeV, the magnets shorted out.
Yamada finally realized the cause: metal slivers left behind when they cut into the vacuum tubes. “So when the magnets were excited to a higher field,” he wrote, “they were pulled inside the magnet gap, stood up and stopped the beam, because they were slightly magnetic material.”
They had to get the slivers out. But how?
Robert Sheldon, a British engineer who’d been brought on to NAL to find “shortcuts and money-saving ideas,” suggested a ferret, equipped with a cleaning tool, could do the job, scampering through the vacuum tubes as if flushing rabbits out of a warren.
The ferret arrived by special delivery from the Wild Game and Fur Farm in Gaylord, Minnesota. At 15 inches long, she was the smallest ferret they’d had. Her fur was brown and black except for white patches on her face. They called her Felicia. She cost $35.
They placed a custom collar around Felicia’s neck and a diaper around her rear; ferret poop in a tube would stop a proton, too. They attached a string to the collar. Felicia was to bring the string from one end of a tube to the other. Then they’d attach a cleanser-dipped swab to the string and pull it through.
The NAL staff doted on Felicia, feeding her chicken, liver, fish heads, and raw hamburger—her favorite. Some employees even took Felicia to their home for the night when the mink farm she generally bunked at had no room for her.
Meanwhile, the engineer Hans Kautzky created a “magnetic ferret” to deal with the debris in the main ring. He attached a dozen Mylar disks to a stainless steel rod, along with a flexible, 700-meter stainless steel cable—the equivalent of Felicia’s string—and a metal-attracting permanent magnet—the counterpart to the cleaning swab. He shot the device through a section of the main ring with compressed air. “With 12 operations, we could make it around the entire ring,” Yamada wrote. “This way we could clean the whole vacuum pipe, though not perfectly.”
But it worked well enough, because over the next several months, the team steadily turned up the energy levels without shorting out the system, and on March 1, 1972, they got the accelerator to reach the target energy of 200 BeV.
After a dozen runs through the Meson Lab tubes—which, when joined, grew too long for her comfort—Felicia went into semi-retirement, and spent most of her time as a pet on the mink farm. One night the following spring, she was at the home of Charles Crose, a NAL employee, when she fell ill. Crose took her to a vet the next day. Under medical care, she briefly rallied, but within a couple of days she died, on May 9, 1972. A necropsy revealed a ruptured abscess in her intestinal tract.
Felicia emerges from a 300-foot-long vacuum pipe at Fermilab:
