PAC2013 - List of Authors (Harris, J.R.)

Paper	Title	Page
MOPAC07	Photonic Crystal as a Passively Driven Structure to Boost Beam Energy	87
	B.R. Poole LLNL, Livermore, California, USA J.R. Harris, S.V. Milton CSU, Fort Collins, Colorado, USA
	Funding: Parts of this work were performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344. The use of electromagnetic structures to couple energy to a charged particle beam is well known. These structures are usually driven by an external source of electromagnetic energy and the structure distributes that energy is such a way as being favorable to accelerate charged particles. Photonic crystals typically consist of periodic arrays of metal and/or dielectric structures spaced on a scale comparable to the wavelength of interest, have been investigated for use both as sources of microwave radiation and particle accelerators. In this case we consider driving a photonic crystal structure using a repetitive sequence of charge bunches driven from a photo-injector to resonantly excite the structure to produce an acceleration field to accelerate a suitably-delayed witness charge bunch to high energy. We examine the generation of the acceleration field as well as spurious modes. The dynamics of the witness bunch are examined to determine the longitudinal dynamics of the bunch and the energy spectra.

TUPSM09	A Two Frequency Gun for High Current Thermionic Cathode Electron Injector Systems	649
	J.P. Edelen, S. Biedron, J.R. Harris, S.V. Milton CSU, Fort Collins, Colorado, USA J.W. Lewellen LANL, Los Alamos, New Mexico, USA
	Funding: Office of Naval Research This paper discusses work done on designing a Radio Frequency, thermionic cathode electron gun for high current injection systems. The background and previous work on the subject is overviewed as well as an introduction to other facilities operating thermionic cathodes and their particular configuration. We discuss using a two frequency TM010 electron gun at the Colorado State University accelerator facility and we discuss theory and simulation of exotic mode electron guns. Results are compared using both PARMELA and SPIFFE and for high current electron beams we have simulated CW operation with very-low back-bombardment levels.

WEPSM17	Non-Invasive Beam Detection in a High-Average Power Electron Accelerator	1082
	J.E. Williams, S. Biedron, J.R. Harris, S.V. Milton CSU, Fort Collins, Colorado, USA S.V. Benson, P.E. Evtushenko, G. Neil, S. Zhang JLAB, Newport News, Virginia, USA
	For a free-electron laser (FEL) to work effectively the electron beam quality must meet exceptional standards. In the case of an FEL operating at infrared wavelengths in an amplifier configuration the critical phase space tends to be in the longitudinal direction. Achieving high enough longitudinal phase space density directly from the electron injector system of such an FEL is difficult due to space charge effects, thus one needs to manipulate the longitudinal phase space once the beam energy reaches a sufficiently high value. However, this is fraught with problems. Longitudinal space charge and coherent synchrotron radiation can both disrupt the overall phase space, furthermore, the phase space disruption is exacerbated by the longitudinal phase space manipulation process required to achieve high peak current. To achieve and maintain good FEL performance one needs to investigate the longitudinal emittance and be able to measure it during operation preferably in a non-invasive manner. Using the electro-optical sampling (EOS) method, we plan to measure the bunch longitudinal profile of a high-energy (~120-MeV), high-power (~10kW or more FEL output power) beam.

THPAC19	Temperature Dependence of Photoemission from Copper and Niobium	1184
	J.R. Harris CSU, Fort Collins, Colorado, USA C.W. Bennett, M.D. Galt, A.D. Holmes, A. Kara, R. Swent NPS, Monterey, California, USA J.W. Lewellen LANL, Los Alamos, New Mexico, USA J. Sears Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA
	Funding: This work was funded by the Office of Naval Research and the High Energy Laser Joint Technology Office. Photocathodes remain the principal electron sources for many particle accelerators. With the increasing interest in the use of superconducting radiofrequency electron guns, it is important to understand how operation at cryogenic temperatures affects the performance of photocathodes. Here we report measurements of the quantum efficiency of copper and niobium under illumination with 266 nm light at temperatures between 85K and 400K. The quantum efficiency of copper was found to vary strongly over this range, while there was only a minimal change in the quantum efficiency of niobium.

Paper

Title

Page

Photonic Crystal as a Passively Driven Structure to Boost Beam Energy

87

B.R. Poole
LLNL, Livermore, California, USA
J.R. Harris, S.V. Milton
CSU, Fort Collins, Colorado, USA

Funding: Parts of this work were performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344.
The use of electromagnetic structures to couple energy to a charged particle beam is well known. These structures are usually driven by an external source of electromagnetic energy and the structure distributes that energy is such a way as being favorable to accelerate charged particles. Photonic crystals typically consist of periodic arrays of metal and/or dielectric structures spaced on a scale comparable to the wavelength of interest, have been investigated for use both as sources of microwave radiation and particle accelerators. In this case we consider driving a photonic crystal structure using a repetitive sequence of charge bunches driven from a photo-injector to resonantly excite the structure to produce an acceleration field to accelerate a suitably-delayed witness charge bunch to high energy. We examine the generation of the acceleration field as well as spurious modes. The dynamics of the witness bunch are examined to determine the longitudinal dynamics of the bunch and the energy spectra.

TUPSM09

A Two Frequency Gun for High Current Thermionic Cathode Electron Injector Systems

649

J.P. Edelen, S. Biedron, J.R. Harris, S.V. Milton
CSU, Fort Collins, Colorado, USA
J.W. Lewellen
LANL, Los Alamos, New Mexico, USA

Funding: Office of Naval Research
This paper discusses work done on designing a Radio Frequency, thermionic cathode electron gun for high current injection systems. The background and previous work on the subject is overviewed as well as an introduction to other facilities operating thermionic cathodes and their particular configuration. We discuss using a two frequency TM010 electron gun at the Colorado State University accelerator facility and we discuss theory and simulation of exotic mode electron guns. Results are compared using both PARMELA and SPIFFE and for high current electron beams we have simulated CW operation with very-low back-bombardment levels.

WEPSM17

Non-Invasive Beam Detection in a High-Average Power Electron Accelerator

1082

J.E. Williams, S. Biedron, J.R. Harris, S.V. Milton
CSU, Fort Collins, Colorado, USA
S.V. Benson, P.E. Evtushenko, G. Neil, S. Zhang
JLAB, Newport News, Virginia, USA

For a free-electron laser (FEL) to work effectively the electron beam quality must meet exceptional standards. In the case of an FEL operating at infrared wavelengths in an amplifier configuration the critical phase space tends to be in the longitudinal direction. Achieving high enough longitudinal phase space density directly from the electron injector system of such an FEL is difficult due to space charge effects, thus one needs to manipulate the longitudinal phase space once the beam energy reaches a sufficiently high value. However, this is fraught with problems. Longitudinal space charge and coherent synchrotron radiation can both disrupt the overall phase space, furthermore, the phase space disruption is exacerbated by the longitudinal phase space manipulation process required to achieve high peak current. To achieve and maintain good FEL performance one needs to investigate the longitudinal emittance and be able to measure it during operation preferably in a non-invasive manner. Using the electro-optical sampling (EOS) method, we plan to measure the bunch longitudinal profile of a high-energy (~120-MeV), high-power (~10kW or more FEL output power) beam.

THPAC19

Temperature Dependence of Photoemission from Copper and Niobium

1184

J.R. Harris
CSU, Fort Collins, Colorado, USA
C.W. Bennett, M.D. Galt, A.D. Holmes, A. Kara, R. Swent
NPS, Monterey, California, USA
J.W. Lewellen
LANL, Los Alamos, New Mexico, USA
J. Sears
Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA

Funding: This work was funded by the Office of Naval Research and the High Energy Laser Joint Technology Office.
Photocathodes remain the principal electron sources for many particle accelerators. With the increasing interest in the use of superconducting radiofrequency electron guns, it is important to understand how operation at cryogenic temperatures affects the performance of photocathodes. Here we report measurements of the quantum efficiency of copper and niobium under illumination with 266 nm light at temperatures between 85K and 400K. The quantum efficiency of copper was found to vary strongly over this range, while there was only a minimal change in the quantum efficiency of niobium.