Brightness Measurements Of Electron Beams Photoemitted From Multicrystalline LaB 6 And The Effects Of Environmental Pressure

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Abstract
Lanthanum hexaboride has been tested as a photoemitter when irradiated by unpolarized UV lasers. For photon energies of 5 eV or less, the material, in a multicrystalline form, is measured to have a quantum efficiency at least an order of magnitude greater than that of simple metals. Maximum currents, from a 1.27 cm2 sample, limited by the available laser power, were recorded to be 52, 36, and 0.9 A at irradiating wavelengths of 193, 248, and 308 nm, respectively. At 193 and 248 nm the corresponding normalized rms brightnesses were 6.7 x 106 and 2.6 x 106 A/cm2-rad2. The results appear insensitive to chamber pressure in, at least, the range of 10-5 to 10-8 toff.

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