Influence of crystallography and purity on brightness of LaB6 cathodes

摘要

The brightness of single‐crystal cathodes of LaB6 oriented in the 〈100〉, 〈110〉, and 〈111〉 directions and six other random directions has been measured. The 〈111〉 cathodes produced currents and brightnesses significantly lower than all other orientations. The other orientations studied produced maximum brightnesses in the range 0.7–1.0 MA/cm2 sr, although the 〈100〉 orientation consistently produced currents higher than other orientations and brightnesses as high or higher than most orientations. A change in impurity level from 1540 ppm to less than 1 ppm had no statistical effect on brightness for crystals of the same orientation.