Quantum efficiency and thermal emittance of metal photocathodes

Modern electron beams have demonstrated the brilliance needed to drive free electron lasers at x-ray wavelengths with major advances occurring since the invention of the photocathode gun and the realization of emittance compensation. These state-of-the-art electron beams are now becoming limited by...

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Bibliographic Details
Published in:Physical review special topics. PRST-AB. Accelerators and beams 2009-07, Vol.12 (7), p.074201, Article 074201
Main Authors: Dowell, David H., Schmerge, John F.
Format: Article
Language:English
Subjects:
Cathodes
Efficiency
Electron beams
Electron distribution
Emittance
Free electron lasers
Nickel
Photocathodes
Quantum efficiency
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Summary:Modern electron beams have demonstrated the brilliance needed to drive free electron lasers at x-ray wavelengths with major advances occurring since the invention of the photocathode gun and the realization of emittance compensation. These state-of-the-art electron beams are now becoming limited by the intrinsic thermal emittance of the cathode. In both dc and rf photocathode guns details of the cathode emission physics strongly influence the quantum efficiency and the thermal emittance. Therefore improving cathode performance is essential to increasing the brightness of beams. It is especially important to understand the fundamentals of cathode quantum efficiency and thermal emittance. This paper investigates the relationship between the quantum efficiency and the thermal emittance for metal cathodes using the Fermi-Dirac model for the electron distribution. We use a consistent theory to derive the quantum efficiency and thermal emittance, and compare our results to those of others.
ISSN:1098-4402
1098-4402
2469-9888
DOI:10.1103/PhysRevSTAB.12.074201