Regen
Regen turns up in 2 fields: photonics, vacuum. Here is what it means to the people in each one.
Regen in photonics
Clipped form of regenerative amplifier, the cavity that traps a seed pulse for many passes of gain before releasing it.
A laser cavity with its own gain medium in which a Pockels cell captures one pulse from a seed oscillator, holds it for tens of round trips while it grows from nanojoules to millijoules, then switches it out. Regens are the standard first stage of femtosecond CPA systems at kHz rates. Getting Pockels cell timing, build-up time and seed matching right is everyday regen work.
"Regen build-up looks fine on the photodiode, 18 round trips, so the energy drop has to be after the dump."
Regen in vacuum
Clipped form of regeneration: warming a cryopump to drive off the gas it has captured, then cooling it again.
The cycle that empties a saturated cryopump: the cold stages are warmed, usually with heaters and a dry nitrogen purge, the released gas is roughed away, and the pump is cooled back to operating temperature. A full regen takes several hours, while a fast or partial regen warms only part of the pump. Techs schedule regens by accumulated argon or hydrogen load, or when the second-stage temperature drifts above about 20 K.
"Cryo on PVD 2 is in regen till about 3 a.m., don't queue any lots on that chamber."