Jay Theilacker, the head of the Accelerator Division’s Cryogenics Department, wrote this week’s column.
For more than 28 years, the Central Helium Liquefier, located in the building across the street from the Feynman Computing Center, has played an essential role in making the Tevatron work. It provides the liquid helium that flows through the veins of the Tevatron to cool more than 1,000 superconducting magnets.
In the 1980s, Fermilab management deemed the around-the-clock operation of the CHL so important that the laboratory built a second, redundant liquefier, using spare parts for its first CHL plant. Today, these plants are still the largest helium liquefiers in the world
It takes a dedicated staff of 11 people to operate and maintain the CHL, and the crew is on shift 24/7. Over the years, the CHL facility has achieved an astounding historical operating up-time of 99.5 percent. Even when the laboratory closed during the blizzard in February, the CHL crew kept things going.
In addition to its CHL responsibilities, the CHL group also monitors the status of the 24 satellite refrigerators that are located along the 4-mile Tevatron ring. Jerry Makara, who leads the Cryogenics Operations Group, coordinates all CHL operations and maintenance requirements together with the Tevatron run coordinator.
The original concept for the Tevatron called for the CHL to fill 500-liter dewars (special containers for cryogenic liquids) with liquid helium, which then would have been trucked to each of the 24 satellite refrigerators to cool the Tevatron’s magnets to minus 450 degrees Fahrenheit. This would have been an incredibly difficult system to operate. Fortunately, Fermilab developed and installed a thermally efficient, 4.5-mile-long transfer line, which continuously transfers liquid helium to each satellite refrigerator (see this FermiNews article for details). This award-winning system allows for a fast cool-down of the Tevatron magnets and a quick recovery of the system when a magnet quenches.
The end of Run II in September will mark 28 years of Tevatron operation. The reliability of the CHL system has served a critical role in the Tevatron’s success.
|An aerial shot of the Central Helium Liquefier building. Photo: Reidar Hahn.|