Depending on specific applications and differing requirements of the evaporants several effusion cells like, e.g., WEZ, NTEZ or PEZ can be equipped with different filament types:
Schematic of filament types Standard Filament SF, Cold Lip Filament CL, Tip Filament TF, Hot Lip Filament HL and Dual Filament DF
Standard Filament SF
A standard wire filament SF heats the crucible evenly along its entire length. A thermocouple TC is fixed near the bottom of the crucible.
Cold Lip Filament CL
A cold lip filament 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.
Tip Filament TF
A tip filament practically is the upper filament of a dual filament. Only the topmost part of the crucible is being heated. This design provides the maximum temperature gradient between crucible bottom and lip.
Hot Lip Filament HL
A hot lip filament is wired more densely at the upper part than the standard heating assembly. This way a higher temperature near the crucible lip is achieved by using only one power supply for the heating.
Dual Filament DF
A dual filament is composed of two heaters that can be independently operated by two PID controlled power supplies.
Dual filament design provides several operation possibilities depending on which operation mode is chosen. Independent operation of the filaments is possible as well as hot lip, top heated or cold lip operation.