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For brighter electron sources: a cryogenically cooled photocathode and DC photogun

Author
Lee, Hyeri
Abstract
Electron beams produced by photoinjectors have a wide range of applications including colliders for high energy and nuclear physics experiments, Free Electron Lasers (FEL), Energy Recovery Linacs (ERL), and Ultrafast Electron Diffraction (UED) with a variety of uses. These applications have been made possible by recent advancement in photocathode and photoinjector research. The key factor is building a compact high-brightness electron source with high voltage and electric field at the photocathode to maximize the electron emission and minimize emittance growth due to space-charge effect. Achieving high brightness from a compact source is a challenging task because it involves an often-conflicting interplay between various requirements imposed by photoemission, acceleration, and beam dynamics. This thesis presents three important results; (i) cryogenically cooled photocathode. From 300K to 90 K, the MTE reduction has been measured from 38±meV to 22 ±1meV. (ii) transmission photocathode. MTEs generated from the photocathode operated in transmission mode is smaller by 20% in comparison with the reflection mode operation, which is accompanied by a corresponding QE decrease of about a factor of 2. (iii) a new design of a DC photoemission gun and beamline constructed at Cornell University, along with demonstration of a cryogenically cooled photocathode and transmission photocathode. This photoemission gun can operate at ~200kV at both room temperature (RT) and cryogenic temperature (low T) with a corresponding electric field of 10MV/m.
Date Issued
2017-08-30Subject
Physics; bright electron beam; cryogenic cathode; photoemission; photoemission gun; transmission cathode; ultrafast electron diffraction
Committee Chair
Bazarov, Ivan
Committee Member
Kourkoutis, Lena Fitting; Dunham, Bruce Matthew; Sethna, James Patarasp
Degree Discipline
Physics
Degree Name
Ph. D., Physics
Degree Level
Doctor of Philosophy
Rights
Attribution-NoDerivatives 2.0 Generic
Type
dissertation or thesis
Except where otherwise noted, this item's license is described as Attribution-NoDerivatives 2.0 Generic