CLASSE Safety Handbook

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Cryogenic Safety

Cryogens are very cold liquids kept at temperatures of -100 F (200 K, or -73 C) or below. Our most commonly used cryogens are liquid helium and liquid nitrogen. They have several uses at CLASSE, such as the CESR superconducting RF cavities (SRF), the CESR superconducting wiggler magnets, and test SRF cavities at the Horizontal Test Cryostat (HTC) testing area in the NW corner of L0 in Wilson Lab, and in Newman Lab. Liquid nitrogen is used in CHESS to cool some target samples.

Two types of cryogens are commonly used at the lab: liquid helium (LHe) and liquid nitrogen (LN2). Both are non-flammable, odorless, and non-toxic. They can, however, pose burn, asphyxiation, fire, and explosion hazards if they are not treated with great care. Mitigation of these hazards, discussed more below, generally involves
  • Proper use of containers, material transfer apparatus, and thermal insulation
  • Use of personal protective clothing (gloves, face shields, lab coats, etc.)
  • Minimization of the quantity of cryogen involved for the purpose at hand
  • Correct placement of pressure relief devices (no "trapped" liquid volumes)
  • Use of cryogens in adequately ventilated spaces and properly sized vent lines

Due to the large volumes of cryogens frequently involved, system failures posing a safety risk (which are rare) can be dramatic, with significant volume breaches being accompanied by loud bangs and hissing associated with large clouds of water vapor. If you suspect a cryogenic failure, stay clear of the failure, calmly exit the area immediately, and notify the cryogenics group, the CESR operator, your supervisor, or the facility manager.

End of Cryogenic Safety
Topic revision: r14 - 02 Apr 2013, bkh
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