Accelerator Update

About the Fermilab Accelerators

The operation of the Fermilab accelerators requires the use of various types of gases. The three main gases used are helium, nitrogen, and argon. Liquid helium and nitrogen are the gases used to cool the Tevatron magnets down to superconducting temperatures. Argon is mostly used in devices that monitor the beam's position and intensity.

Safety first when using liquefied gases

A large leak of cryogenic gases in a tunnel could be a problem. Liquid helium, nitrogen, and argon are inert, colorless, odorless, and extremely cold. Inert means these gases are stable; they don't react with other substances easily, which is good thing. They are not poisonous. Nitrogen and argon, along with oxygen, make up the normal air you breathe. But being colorless and odorless means that a person can not sense the gas's presence without the use of a device made for that purpose. When warmed from their liquid state back to their gaseous state, these gases expand dramatically, on the order of 800 times to one, and will displace the normal atmosphere.

The air you breathe contains about 21% oxygen, 78% nitrogen, and 1% argon. If you are in a confined place where the oxygen level has dropped to 17%, your breathing volume increases as does your heartbeat. At 16% you begin feeling dizzy and your reaction time slows. Lower levels of oxygen pose even more severe health threats.

Fermilab educates its employees about the care they have to take when entering confined spaces that contain liquefied-gas sources. We take precaution in several ways. One, we identify the areas that have potential Oxygen Deficiency Hazards (ODH). Two, we control these areas with keys that must be signed out (lock-out policy), warning signs, fixed oxygen monitoring equipment, and ventilation systems. Three, we only allow medically approved personal into these areas. Four, we only allow people trained for oxygen deficient hazards into the areas. Five, we require all people entering most ODH areas to have a portable air bottle and their own oxygen monitoring device that alarms at 19.5%. Six, in most areas we require that a minimum of two people enter and stay together.

If an ODH accident happens the people are trained to don their air mask and head for an exit. If there's a false alarm of just one monitoring device, even if the other devices read okay, people still immediately exit and try to figure out what happened from a safe place. Fermi has very few areas where an exit is more than one minute away; those areas that are more confined have heavier restrictions placed on those who enter.

Fermilab makes safety a priority and this is only a brief list of one aspect. But as you can see, the women and men who work here have to know much more than just their job.