IPAC2015 - List of Authors (Benson, S.V.)

Paper	Title	Page
MOPWI029	Electron Bombardment of ZnTe EO Bunch Charge Detector for Signal Lifetime Studies in Radiation Environment	1220
	J.E. Williams, S. Biedron, S.V. Milton CSU, Fort Collins, Colorado, USA S.V. Benson, S. Zhang JLab, Newport News, Virginia, USA
	Electro-optic detection of bunch charge distribution utilizing the nonlinear Pockel's and Kerr effect of materials has been implemented at various facilities as a method of passive detection for beam preservation throughout characterization. Most commonly, the inorganic II-VI material ZnTe is employed due to it's strong Pockel's EO effect and relatively high temporal resolution (~90 fs). Despite early exploration of radiation damage on ZnTe in exploration of semi-conductor materials in the 1970's, full characterization of EO response over radiation lifetime has yet to be performed. The following poster presents a method for ZnTe crystal characterization studies throughout radiation exposure at various energies and dosages by analyzing the changes in index of refraction including bulk uniformity, and THz signal response changes.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-MOPWI029
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TUPMA033	A Bunch Compression Method for Free Electron Lasers that Avoids Parasitic Compressions	1907
	S.V. Benson, D. Douglas, C. Tennant, F.G. Wilson JLab, Newport News, Virginia, USA D.C. Nguyen LANL, Los Alamos, New Mexico, USA
	Funding: This work was supported by U.S. DOE Contract No. DE-AC05-84-ER40150, the Air Force Office of Scientific Research, DOE Basic Energy Sciences. Virtually all existing high energy (>few MeV) linac-driven FELs compress the electron bunch length though the use of off-crest acceleration on the rising side of the RF waveform followed by transport through a magnetic chicane. This approach has at least three flaws: 1) it is difficult to correct aberrations- particularly RF curvature, 2) rising side acceleration exacerbates space charge-induced distortion of the longitudinal phase space, and 3) all achromatic "negative compaction" compressors create parasitic compression during the final compression process, increasing the CSR-induced emittance growth. One can avoid these deficiencies by using acceleration on the falling side of the RF waveform and a compressor with M56>0. This approach offers multiple advantages: 1) It is readily achieved in beam lines supporting simple schemes for aberration compensation, 2) Longitudinal space charge (LSC)-induced phase space distortion tends, on the falling side of the RF waveform, to enhance the chirp, and 3) Compressors with M56>0 can be configured to avoid spurious over-compression. We will discuss this bunch compression scheme in detail and give results of a successful beam test in April 2012 using the JLab UV Demo FEL
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-TUPMA033
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TUPMA034	Control of Synchrotron Radiation Effects During Recirculation with Bunch Compression	1910
	D. Douglas, S.V. Benson, R. Li, C. Tennant JLab, Newport News, Virginia, USA G.A. Krafft, B. Terzić ODU, Norfolk, Virginia, USA C.-Y. Tsai Virginia Polytechnic Institute and State University, Blacksburg, Virginia, USA
	Funding: This material is based upon work supported by the U.S. Department of Energy, Office of Science, Office of Nuclear Physics under contract DE-AC05-06OR23177. Studies of beam quality preservation during recirculation * have been extended to generate a design of a compact arc providing bunch compression with positive momentum compaction and control of both incoherent and coherent synchrotron radiation (ISR and CSR) effects using the optics balance methods of diMitri et al.. In addition, the arc/compressor generates very little micro-bunching gain. We detail the beam dynamical basis for the design, discuss the design process, give an example solution, and provide simulations of ISR and CSR effects. Reference will be made to a complete analysis of micro-bunching effects **. D. Douglas et al., these proceedings S. Benson et al., these proceedings * S. diMitri et al., Phys. Rev. Lett. 110, 014801, 2 January 2013 **** C.Y. Tsai et al., these proceedings
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-TUPMA034
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TUPMA035	Control of Synchrotron Radiation Effects during Recirculation	1913
	D. Douglas, S.V. Benson, A.S. Hofler, R. Kazimi, R. Li, Y. Roblin, C. Tennant JLab, Newport News, Virginia, USA G.A. Krafft, B. Terzić ODU, Norfolk, Virginia, USA C.-Y. Tsai Virginia Polytechnic Institute and State University, Blacksburg, Virginia, USA
	Funding: This material is based upon work supported by the U.S. Department of Energy, Office of Science, Office of Nuclear Physics under contract DE-AC05-06OR23177. Numerous proposals invoke recirculation and/or energy recovery for cost-performance optimization. These often encounter challenges with the beam-quality-degrading effects of incoherent and coherent synchrotron radiation (ISR and CSR). We describe a means of controlling of this degradation. The approach utilizes results by diMitri et al. , and invokes behavior observed during simulations of the recirculation process. The method is based on the use of periodically isochronous 2nd-order achromats; this not only insures that the conditions for the suppression of CSR-driven emittance growth are met, it also suppresses micro-bunching gain over a broad range of parameter space . Details of specific designs will be presented, and a reference to an analysis of micro-bunching effects provided. A planned test of the CSR suppression mechanism in CEBAF will be described. S. diMitri et al., Phys. Rev. Lett. 110, 014801, 2 January 2013. *C.Y. Tsai et al., these proceedings.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-TUPMA035
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WEXB1	Coherent Synchrotron Radiation in Energy Recovery Linacs	2387
	C.C. Hall, S. Biedron, A.L. Edelen, S.V. Milton CSU, Fort Collins, Colorado, USA S.V. Benson, D. Douglas, R. Li, C. Tennant JLab, Newport News, Virginia, USA B.E. Carlsten LANL, Los Alamos, New Mexico, USA
	Collective beam effects, including coherent synchrotron radiation (CSR), have been studied on free-electron lasers (FELs). Here we will discuss a particular case of the CSR effects, that in energy-recovery linacs (ERLs). Special consideration is given to these machines because of their high average beam power and the architecture of the machine for energy recovery forces extreme bends. A recent study conducted on the JLab IR FEL looked at how CSR impacts both average energy and the energy spectrum of the beam. Such studies are important, both broadly, to the understanding of CSR and more specifically for a number of proposed ERL projects. A few proposed examples include the MEIC bunched beam cooler ERL design and ERL FELs for potential lithography purposes that would operate in the EUV range.
	Slides WEXB1 [16.383 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-WEXB1
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Paper

Title

Page

Electron Bombardment of ZnTe EO Bunch Charge Detector for Signal Lifetime Studies in Radiation Environment

1220

J.E. Williams, S. Biedron, S.V. Milton
CSU, Fort Collins, Colorado, USA
S.V. Benson, S. Zhang
JLab, Newport News, Virginia, USA

Electro-optic detection of bunch charge distribution utilizing the nonlinear Pockel's and Kerr effect of materials has been implemented at various facilities as a method of passive detection for beam preservation throughout characterization. Most commonly, the inorganic II-VI material ZnTe is employed due to it's strong Pockel's EO effect and relatively high temporal resolution (~90 fs). Despite early exploration of radiation damage on ZnTe in exploration of semi-conductor materials in the 1970's, full characterization of EO response over radiation lifetime has yet to be performed. The following poster presents a method for ZnTe crystal characterization studies throughout radiation exposure at various energies and dosages by analyzing the changes in index of refraction including bulk uniformity, and THz signal response changes.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-MOPWI029

Export •

reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

TUPMA033

A Bunch Compression Method for Free Electron Lasers that Avoids Parasitic Compressions

1907

S.V. Benson, D. Douglas, C. Tennant, F.G. Wilson
JLab, Newport News, Virginia, USA
D.C. Nguyen
LANL, Los Alamos, New Mexico, USA

Funding: This work was supported by U.S. DOE Contract No. DE-AC05-84-ER40150, the Air Force Office of Scientific Research, DOE Basic Energy Sciences.
Virtually all existing high energy (>few MeV) linac-driven FELs compress the electron bunch length though the use of off-crest acceleration on the rising side of the RF waveform followed by transport through a magnetic chicane. This approach has at least three flaws: 1) it is difficult to correct aberrations- particularly RF curvature, 2) rising side acceleration exacerbates space charge-induced distortion of the longitudinal phase space, and 3) all achromatic "negative compaction" compressors create parasitic compression during the final compression process, increasing the CSR-induced emittance growth. One can avoid these deficiencies by using acceleration on the falling side of the RF waveform and a compressor with M56>0. This approach offers multiple advantages: 1) It is readily achieved in beam lines supporting simple schemes for aberration compensation, 2) Longitudinal space charge (LSC)-induced phase space distortion tends, on the falling side of the RF waveform, to enhance the chirp, and 3) Compressors with M56>0 can be configured to avoid spurious over-compression. We will discuss this bunch compression scheme in detail and give results of a successful beam test in April 2012 using the JLab UV Demo FEL

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-TUPMA033

Export •

reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

TUPMA034

Control of Synchrotron Radiation Effects During Recirculation with Bunch Compression

1910

D. Douglas, S.V. Benson, R. Li, C. Tennant
JLab, Newport News, Virginia, USA
G.A. Krafft, B. Terzić
ODU, Norfolk, Virginia, USA
C.-Y. Tsai
Virginia Polytechnic Institute and State University, Blacksburg, Virginia, USA

Funding: This material is based upon work supported by the U.S. Department of Energy, Office of Science, Office of Nuclear Physics under contract DE-AC05-06OR23177.
Studies of beam quality preservation during recirculation * have been extended to generate a design of a compact arc providing bunch compression with positive momentum compaction ** and control of both incoherent and coherent synchrotron radiation (ISR and CSR) effects using the optics balance methods of diMitri et al.***. In addition, the arc/compressor generates very little micro-bunching gain. We detail the beam dynamical basis for the design, discuss the design process, give an example solution, and provide simulations of ISR and CSR effects. Reference will be made to a complete analysis of micro-bunching effects ****.
* D. Douglas et al., these proceedings
** S. Benson et al., these proceedings
*** S. diMitri et al., Phys. Rev. Lett. 110, 014801, 2 January 2013
**** C.Y. Tsai et al., these proceedings

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-TUPMA034

Export •

reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

TUPMA035

Control of Synchrotron Radiation Effects during Recirculation

1913

D. Douglas, S.V. Benson, A.S. Hofler, R. Kazimi, R. Li, Y. Roblin, C. Tennant
JLab, Newport News, Virginia, USA
G.A. Krafft, B. Terzić
ODU, Norfolk, Virginia, USA
C.-Y. Tsai
Virginia Polytechnic Institute and State University, Blacksburg, Virginia, USA

Funding: This material is based upon work supported by the U.S. Department of Energy, Office of Science, Office of Nuclear Physics under contract DE-AC05-06OR23177.
Numerous proposals invoke recirculation and/or energy recovery for cost-performance optimization. These often encounter challenges with the beam-quality-degrading effects of incoherent and coherent synchrotron radiation (ISR and CSR). We describe a means of controlling of this degradation. The approach utilizes results by diMitri et al. *, and invokes behavior observed during simulations of the recirculation process. The method is based on the use of periodically isochronous 2nd-order achromats; this not only insures that the conditions for the suppression of CSR-driven emittance growth are met*, it also suppresses micro-bunching gain over a broad range of parameter space **. Details of specific designs will be presented, and a reference to an analysis of micro-bunching effects ** provided. A planned test of the CSR suppression mechanism in CEBAF will be described.
*S. diMitri et al., Phys. Rev. Lett. 110, 014801, 2 January 2013.
**C.Y. Tsai et al., these proceedings.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-TUPMA035

Export •

reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

WEXB1

Coherent Synchrotron Radiation in Energy Recovery Linacs

2387

C.C. Hall, S. Biedron, A.L. Edelen, S.V. Milton
CSU, Fort Collins, Colorado, USA
S.V. Benson, D. Douglas, R. Li, C. Tennant
JLab, Newport News, Virginia, USA
B.E. Carlsten
LANL, Los Alamos, New Mexico, USA

Collective beam effects, including coherent synchrotron radiation (CSR), have been studied on free-electron lasers (FELs). Here we will discuss a particular case of the CSR effects, that in energy-recovery linacs (ERLs). Special consideration is given to these machines because of their high average beam power and the architecture of the machine for energy recovery forces extreme bends. A recent study conducted on the JLab IR FEL looked at how CSR impacts both average energy and the energy spectrum of the beam. Such studies are important, both broadly, to the understanding of CSR and more specifically for a number of proposed ERL projects. A few proposed examples include the MEIC bunched beam cooler ERL design and ERL FELs for potential lithography purposes that would operate in the EUV range.

Slides WEXB1 [16.383 MB]

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-WEXB1

Export •

reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)