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Description
ntroduction
Tungsten filaments are used in all major brands of scanning and transmission electron microscopes (SEM / TEM). These high quality, high stability tungsten EM filaments, also called cathodes or electron emitters, are manufactured to exceed the specifications of the original equipment manufacturers. These superior cathodes are made using high quality ceramic discs, exact size contact pins and high grade tungsten filament wire. Special tools are used to produce the correct shape of the tungsten filament. All tungsten filaments are precisely aligned and annealed in high vacuum to reduce stress in the filament. This will guarantee optimum stability, maximum brightness, longer lifetime and overall lower running costs.
Exclusive features of the EM-Tec tungsten EM filaments are:
- Minimum tip radius for coherent beam
- Rigid attachment of filament wire to post to increase stability
- Fully stress relieved for enhanced cathode lifetime
- Polished post ends
- Precise dimensions
- Better long term economy
General tips for using and handling tungsten SEM/TEM filaments:
- Tungsten filaments are fragile – handle with care and make sure that when replacing a filament that the tip is not touched by the Wehnelt cylinder.
- Adjust the filament so that the tip is central in the opening of the Wehnelt cylinder.
- Be careful not to over saturate the tungsten filament. Lifetime is longer when the filaments are operated just under full saturation. Check after a few days; to achieve saturation, the heating current reduces over lifetime.
- If possible, ramp up the heating current in small and slow steps. Same for ramping down.
- If possible, wait until the filament is cooled down before venting the SEM. Venting with dry nitrogen is preferred
Please consult the following table for the correct type of tungsten filament for your SEM, TEM or Microprobe. The EM-Tec tungsten filaments are available for TFS, FEI, Philips, Hitachi, ISI, JEOL, Tescan, Zeiss, LEO, Cambridge Instruments, and Leica Electron Microscopes
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