Inventing a thingamajig for NuMI's "mission impossible"
Sometimes, it takes doing the nearly impossible to keep physics experiments running smoothly. It also takes a sense of humor. And a thingamajig.
Crews in Fermilab’s NuMI/MINOS experiment recently extracted and replaced a difficult to access piece of equipment using a homemade device. They replaced the experiment’s hadron monitor, a key piece of equipment that helps to align and monitor the beam quality.
In order for particles to get to the hadron monitor, protons enter the experiment, collide with a graphite target and then break apart. Another piece of equipment then focuses these resulting particles into a pipe, called the decay pipe, where the particles decay, or transform into other particles. The monitor is located in front of the decay pipe, an area where workers can’t go and that is difficult for machines to access.
“The hadron monitor wasn’t designed to be replaced, and now we have to replace it. This is a challenge,” said NuMI Shutdown Coordinator Mike Andrews before the repair.
When problems started to exist with the hadron monitor two years ago, NuMI/MINOS collaborators solicited the help of an expert team of engineers and technicians from the accelerator and particle physics divisions to conceive, design, and create a device that could remotely extract and replace the monitor.
The answer was an Erector Set-looking device with no name. The one-of-a-kind 3,000-pound device stood about 14 feet tall, was 5 feet long and 5 feet wide, and had its nickname, thingamajig, scrawled on its center steel beam in permanent marker.
“We didn’t know what to call it,” said Al Legan of the Accelerator Division Controls Department.
Legan, who used to work on manipulators and fixed-target experiments, designed seven motors for the device--one for each of its movable parts. He worked with Vladimir Sidorov, an Accelerator Division engineer, and Jerry Judd from the Particle Physics Division's mechanical support department.
Sidorov designed the device’s structure and mechanics, while Judd was responsible for the device’s assembly. Both previously worked on the Main Injector’s collimator system.
The expert team spent six months working in constant communication to create the device--sharing designs and ideas via e-mail and in person.
The result was a remotely operated and motorized device made from steel beams, pulleys, motors, and three pan-and-tilt and six miniature mounted cameras. The cameras allowed the replacement crew to guide the device. The team had to wait until a long shutdown to extract and replace the monitor.
A test run of the fully-constructed device took place in late June. The team of Judd, Legan, Sidorov, and the other Meson Assembly Building technicians, welders, engineers, safety professionals, and machinists who helped to put it together watched as the team remotely extended and lowered the device’s metal arm before raising and retracting it.
“It did exactly what I wanted it to do,” Sidorov says.
The next challenge was getting the giant device into the cramped absorber hall area. That meant disassembling it, hand carrying each of the pieces underground, and removing staircases, electrical components, and ventilation elements in that area before it could be reassembled.
On August 5, the day of the extraction, crews worked behind the existing absorber pile, approximately 50 feet of shielding, and using the cameras mounted to the device as guides, remotely moved the device in place. Much like using a well-engineered claw game at the arcade, Legan lined up the end of the device over the monitor and then guided down its metal frame into the pit where the monitor sat. The metal box covered the monitor on the first try and Legan remotely lifted the monitor. Once fully extracted, Legan manipulated the device to retract the end of the device and slide the monitor back to the center frame and released it into an aluminum box waiting below. The team then slid a new monitor into place.
Collaborators from the University of Texas-Austin wired the new monitor once it was in place.
Dave Erickson, Meson Assembly Building supervisor, applauded his team’s efforts and credited them for doing the impossible during the past few decades. Erickson specifically credited Lenny Harbacek, the Meson Assembly Building welder, for his work assembling the thingamajig.
“A lot of people utilize us because we are one of the only shops around that do this kind of work all the way through,” Erickson says. “People regularly come in and drop off projects or need services such as this.”
The thingamajig, its purpose served, will become part of the project it helped to fix. It remains where it was constructed in the tunnel and a walkway has been built over it.