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Title: An improved analytic model of electron back-bombardment in thermionic-cathode RF guns

Authors:
 [1]; ORCiD logo [2];  [1];  [1];  [1]
  1. Colorado State Unviersity, Fort Collins, CO
  2. Los Alamos National Laboratory
Publication Date:
Research Org.:
Los Alamos National Lab. (LANL), Los Alamos, NM (United States)
Sponsoring Org.:
Universities/Institutions
OSTI Identifier:
1392788
Report Number(s):
LA-UR-17-28082
DOE Contract Number:
AC52-06NA25396
Resource Type:
Conference
Resource Relation:
Conference: 2015 International Particle Accelerator Conference ; 2015-05-03 - 2015-05-03 ; Richmond, Virginia, United States
Country of Publication:
United States
Language:
English
Subject:
Accelerator Design, Technology, and Operations; electron thermionic cathode back bombardment

Citation Formats

Edelen, J. P., Lewellen, John W. IV, Biedron, S. G., Harris, J. R., and Milton, S. V. An improved analytic model of electron back-bombardment in thermionic-cathode RF guns. United States: N. p., 2017. Web.
Edelen, J. P., Lewellen, John W. IV, Biedron, S. G., Harris, J. R., & Milton, S. V. An improved analytic model of electron back-bombardment in thermionic-cathode RF guns. United States.
Edelen, J. P., Lewellen, John W. IV, Biedron, S. G., Harris, J. R., and Milton, S. V. 2017. "An improved analytic model of electron back-bombardment in thermionic-cathode RF guns". United States. doi:. https://www.osti.gov/servlets/purl/1392788.
@article{osti_1392788,
title = {An improved analytic model of electron back-bombardment in thermionic-cathode RF guns},
author = {Edelen, J. P. and Lewellen, John W. IV and Biedron, S. G. and Harris, J. R. and Milton, S. V.},
abstractNote = {},
doi = {},
journal = {},
number = ,
volume = ,
place = {United States},
year = 2017,
month = 9
}

Conference:
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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, fieldenhancement, 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.
  • DC high voltage GaAs photoguns are key components at accelerator facilities worldwide. New experiments and new accelerator facilities demand improved performance from these guns, in particular higher current operation and longer photocathode operating lifetime. This conference submission explores bulk GaAs photocathode lifetime as a function of beam current, active photocathode area, laser spot size and the vacuum of the gun and beam line. Lifetime measurements were made at 100 microamps, a beam current relevant for accelerators like CEBAF, and at beam currents of 1 milliamps and 5 milliamps, a regime that is interesting for high current Free Electron Laser (FEL)more » and Energy Recovery Linac (ERL) operation.« less
  • Preliminary calculations using the computer code PARMELA indicate that it is possible to achieve peak currents on the order of 1 kA using a thermionic-cathode rf gun and ballistic bunch compression. In contrast to traditional magnetic bunching schemes, ballistic bunch compression uses a series of rf cavities to modify the energy profile of the beam and properly chosen drifts to allow the bunching to occur naturally. The method, suitably modified, should also be directly applicable to photoinjector rf guns. Present work is focusing on simultaneously compressing the bunch while reducing the emittance of the electron beam. At present, the calculatedmore » normalized rms emittance is in the neighborhood of 6.8 {pi} mm mrad with a peak current of 0.88 kA, and a peak bunch charge of 0.28 nC from a thermionic-cathode gun.« less
  • This paper presents a comparison between simulation results and a first principles analytical model of electron back-bombardment developed at Colorado State University for single-cell, thermionic-cathode rf guns. While most previous work on back-bombardment has been specific to particular accelerator systems, this work is generalized to a wide variety of guns within the applicable parameter space. The merits and limits of the analytic model will be discussed. This paper identifies the three fundamental parameters that drive the back-bombardment process, and demonstrates relative accuracy in calculating the predicted back-bombardment power of a single-cell thermionic gun.
  • This paper discusses the following topics in electron guns: self fields; external fields; thermal-emittance-limited guns; and guns for electron linacs. 20 refs., 3 figs.