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| WEPOB25 |
Analytical Modeling of Electron Back-Bombardment Induced Current Increase in Un-Gated Thermionic Cathode Rf Guns |
953 |
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- J.P. Edelen
Fermilab, Batavia, Illinois, USA
- J.R. Harris
Directed Energy Directorate, Air Force Research Laboratory, Albuquerque, USA
- J.W. Lewellen
LANL, Los Alamos, New Mexico, USA
- Y. Sun
ANL, Argonne, Illinois, USA
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In this paper we derive analytical expressions for the output current of an un-gated thermionic cathode RF gun in the presence of back-bombardment heating. We provide a brief overview of back-bombardment theory and discuss comparisons between the analytical back-bombardment predictions and simulation models. We then derive an expression for the output current as a function of the RF repetition rate and discuss relationships between back-bombardment, field-enhancement, and output current. We discuss in detail the relevant approximations and then provide predictions about how the output current should vary as a function of repetition rate for some given system configurations.
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| DOI • |
reference for this paper
※ https://doi.org/10.18429/JACoW-NAPAC2016-WEPOB25
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| WEPOB26 |
Observation of Repetition-Rate Dependent Emission From an Un-Gated Thermionic Cathode Rf Gun |
956 |
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- J.P. Edelen
Fermilab, Batavia, Illinois, USA
- J.R. Harris
Directed Energy Directorate, Air Force Research Laboratory, Albuquerque, USA
- J.W. Lewellen
LANL, Los Alamos, New Mexico, USA
- Y. Sun
ANL, Argonne, Illinois, USA
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Recent work at Fermilab in collaboration with the Advanced Photon Source and members of other national labs, designed an experiment to study the relationship between the RF repetition rate and the average current per RF pulse. While existing models anticipate a direct relationship between these two parameters we observed an inverse relationship. We believe this is a result of damage to the barium coating on the cathode surface caused by a change in back-bombardment power that is unaccounted for in the existing theories. These observations shed new light on the challenges and fundamental limitations associated with scaling an un-gated thermionic cathode RF gun to high average current.
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| DOI • |
reference for this paper
※ https://doi.org/10.18429/JACoW-NAPAC2016-WEPOB26
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| WEPOB39 |
Photo-Injector Optimization and Validation Study with the OPAL Beam Simulation Code |
984 |
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- L.D. Duffy, K. Bishofberger, J.W. Lewellen, S.J. Russell, D.Y. Shchegolkov
LANL, Los Alamos, New Mexico, USA
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A 42 keV x-ray free electron laser (XFEL) is a plausible technology alternative for the Matter Radiation Interactions in Extremes (MaRIE) experimental project, a concept developed by Los Alamos National Laboratory. An early pre-conceptual design for such an XFEL calls for 100 pC electron bunches with very low emittance and energy spread. High fidelity simulations that capture all beamline physics will be required to ensure a successful design. We expect to use the beam simulation code OPAL as one of the tools in this process. In this study, we validate OPAL as a photo-injector design tool by comparing its performance with published PITZ experimental data and simulations.
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| DOI • |
reference for this paper
※ https://doi.org/10.18429/JACoW-NAPAC2016-WEPOB39
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