The large gain in brightness and long operating life of Lanthanum Hexaboride cathodes are well known. Kimball Physics' LaB6 cathodes are at least equal in these respects to other cathodes and they also offer a price advantage.
Additionally, Kimball designed their cathodes with a much larger crystal and a one-piece base. The result is greater robustness and much improved life when the operating conditions are less than optimal, such as a vacuum of not quite the desirable 10-8 torr. Lesser vacua result in a contamination layer on the crystal. Overheating the cathode will remove this, but frequently leads to early failure of the Vogel mount design employed by other LaB6 cathode manufacturers. Accidental overheating of the cathode is much better tolerated by Kimball's design.
We recommend Kimball LaB6 cathodes for all electron beam instruments equipped with ion getter or turbo molecular pumps and nitrogen backfill of the column.
- Greater brightness that is available results in higher resolution, better EDS count rates in high power TEM and much greater uninterrupted operating life.
- For low power work where high brightness is less important, cathode life can be over 5000 hours. Even with less than ideal vacua, cathode life of more than 1000 hours is expected.
- Beam current stability is superb. This makes LaB6 cathodes suitable for quantitative microanalyses, provided the instrument has a suitable vacuum system.
In summary: Kimball's LaB6 cathodes are less risky to operate; their lower cost and long operating life yield savings in cathodes, instrument downtime and operator's time. If your instrument is suitable, then these better performing LaB6 cathodes are more economical to use for routine operation than standard tungsten filaments.
- The angle of the cone makes very little difference to LaB6 performance. All cathodes except for those with very small micro flats are supplied with a 90-degree cone. The top of the cone is machined to provide a micro flat.
- Micro Flats: Larger flats provide a larger illuminated area and greater longer-term beam stability, as is required for microprobes, but less brightness. Conversely, smaller micro flats result in greater brightness with a smaller illuminated area at given settings compared to larger micro flats. Cathodes with 15 or 20 square micrometer flats are most commonly sold to users who routinely need high magnifications. The 20 square micrometer flats are excellent for labs working mostly on sectioned specimens; they are a compromise that offers the LaB6 long cathode life and gives some additional brightness over W filaments. 40 square micrometer flats are available, but at considerably greater cost. At the other end of the scale we can provide a 60-6, which is especially suitable for constant very high-resolution work, these cost only ~AUD50 more than standard cathodes.
Please request a quotation for special cones/flats. Specials are generally on 5 weeks delivery.
Kimball Physics have extensive information on the use, optimisation and vacuum dump recovery of these cathodes. All of this available online at http://www.kimballphysics.com/
ProSciTech also supplies any other Kimball products, including tantalum disc and Thorium oxide emitters.
To order, indicate make and model of instrument. The size of the normally supplied microflat is 15 square micrometers
E.g.: LaB6 Cathode 90-15 for Cambridge S-410