Glossary
A cold lip filament CL is a shorter version of the standard filament SF. It does not reach up to the orifice part of the crucible. This fact and some additional shielding leave the crucible lip clearly cooler than the lower parts. This is required for Aluminum evaporation for example.
Alternative filament types are Standard Filament SF, Tip Filament TF, Hot Lip Filament HL and Dual Filament DF: