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Proceedings Article

Physics of high-intensity nanosecond electron source

[+] Author Affiliations
Alberto Herrera-Gomez, William E. Spicer

Stanford Univ. (USA)

Proc. SPIE 2022, Photodetectors and Power Meters, 51 (October 15, 1993); doi:10.1117/12.158588
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From Conference Volume 2022

  • Photodetectors and Power Meters
  • Kenneth J. Kaufmann
  • San Diego, CA | July 11, 1993


A new high intensity, short time electron source is now being used at the Stanford Lineal Accelerator Center (SLAC). By using a GaAs negative affinity semiconductor in the construction of the cathode, it was possible to fulfill the operation requirements, such as peak currents of tens of amperes, peak widths of the order of nanoseconds, hundreds of hours of operation stability, and electron spin polarization. The cathode is illuminated with high intensity laser pulses, and photoemitted electrons constitute the yield. Because of the high currents, some non-linear effects are present. Very noticeable is the so called Charge Limit (CL) effect, which consist of a limit on the total charge in each pulse, that is, the total bunch charge stops increasing as the light pulse total energy increases. In this paper we will explain the mechanism of the CL and how it is caused by the photovoltaic effect. The treatment is based on the Three Step model of photoemission. We will relate the CL to the characteristics of the surface and bulk of the semiconductor, such as doping, band bending, surface vacuum level, and density of surface states. We also discuss possible ways to prevent the CL to take place.

© (1993) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

Alberto Herrera-Gomez and William E. Spicer
"Physics of high-intensity nanosecond electron source", Proc. SPIE 2022, Photodetectors and Power Meters, 51 (October 15, 1993); doi:10.1117/12.158588; http://dx.doi.org/10.1117/12.158588

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