77k

77 Kelvin (77 K) is a temperature on the Kelvin scale. It corresponds to −196.15 °C and is the approximate boiling point of liquid nitrogen at standard atmospheric pressure (about 1 atm, 101.3 kPa).

In practical terms, 77 K is a common operating temperature in cryogenics and laboratory work because liquid nitrogen is inexpensive and readily available. A vessel containing LN2 can maintain a temperature near 77 K as long as boil-off continues, with the temperature set by the latent heat of vaporization and the ambient pressure.

77 K has wide use in science and technology. It is employed to cool infrared detectors, cryogenic shields, and various experimental setups that require low temperatures without resorting to liquid helium. The temperature is also relevant in superconductivity research; many high-temperature superconductors have critical temperatures above 77 K, so cooling to this point with LN2 enables superconducting experiments without helium cooling. In instrumentation and calibration, 77 K serves as a convenient reference temperature for certain cryogenic stages and detectors.

Safety considerations are important when working at 77 K. Liquid nitrogen displaces oxygen in the air, creating asphyxiation hazards in poorly ventilated spaces, and contact with LN2 or cryogenic equipment can cause severe cold burns. Proper ventilation, insulating dewars, eye protection, gloves, and training are essential for safe handling.