Lanthanum hexaboride filaments

Kimball Physics single crystal lanthanum hexaboride (LaB₆) cathodes are available for most makes of electron microscopes and other electron beam instruments where a suitable gun vacuum in the region of  10^-7 Torr is attainable. The filament heater can then be driven by the normal power supply of the microscope.
Brightness above 1 x 10⁶ Amp/cm² steradian is achievable.
For SEM applications, the higher brightness provides better imaging resolution and improved efficiency for microanalysis. For TEM, the low energy spread of the LaB₆ filament is particularly advantageous for high resolution imaging. Alternatively, LaB₆ filaments may be used where a long filament life is important; lifetimes in excess of six months continuous operation are regularly achieved.