Fermi National Laboratory

Accelerator Update

Wednesday November 5 through Friday November 7
All shifts began in shutdown.

On Wednesday, early on the day shift, operators accessed the Booster and Linac to search for a possible nitrogen leak. Near noon, experts reported that the Tevatron (TeV) had been successfully ramped to 980 GeV. By 6 PM, the TeV had been ramped to 1005 GeV. Operations turned on the Antiproton Source power supplies.

On Thursday, at 1 AM a CHL technician reported that they had lost their nitrogen plant due to a power glitch. A cryo expert had the plant recovered by 4 AM. Near the end of the midnight shift the cryo coordinator had warmed up the cryo systems at TeV sectors B1, D1, and F1 for scheduled work. The High Voltage expert reported that a trip on feeder 31 caused CHL's power glitch. Linac and Booster techs accessed their tunnels all morning. Operations established beam to Booster at 1 PM. Booster began a beam study period.

On Friday, at 7:30 AM a cryo expert reported a bad Kautzky valve in the TeV sector F2. He's warming up the cryo system at F2 to replace the bad valve.


  • The magnet unrolls at sector B16 are half way done.
  • The D0 low beta quad girder move began on November 5th and will continue through today.
  • Techs have begun repairing small LCW leaks at sector F0.
  • Techs began checking smart bolt cold lifts on November 5.
  • The F0 Lambertson final laser tracker survey will begin on November 10.
  • The A 48 collimator needs to be resurveyed
  • The Collider Detector Facility (CDF) low beta magnets as founds will begin on November 10.
  • Install the poly beads at CDF sometime after November 11th.
  • Begin filling all fire stops beginning November 10.

A Compressor takes low pressure, low temperature gas and compresses it into a high pressure, high temperature gas. The Condenser accepts the gas from the compressor and, through some cooling medium, condenses it to a high pressure, cool temperature liquid. The liquid line then feeds the Thermal Expansion Valve or device where the liquid expands and flashes to a gas and cools. The final part of this basic system is the Evaporator. It is a heat exchanger where the expanded cold gas exchanges heat with the area being cooled. (This area may be your refrigerator, your living room, or a meat locker. The fluid is just normal air.)

What you see in the above description is a basic refrigeration cycle. The compressor and thermal expansion valve are the boundaries for the high and low sides.

It's important to understand that a refrigerator is a heat engine that operates in reverse. Energy is transferred from a low level to high level, which is contrary to the spontaneous processes that occur in nature. To accomplish this transfer, an amount of work must be supplied dependent on the temperatures involved. Energy gets added to this workload to compensate for the inefficiencies inherent in heat transfer, inefficiencies that arise from heat exchange equipment and the irreversible behavior of compression or expansion equipment.

Some of the same principles used in this basic system apply to normal cryogenic refrigeration systems as well.

Accelerator Update Archive

More Information
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last modified 11/7/2003   email Fermilab