IPAC2015 - List of Authors (Tsai, C.-Y.)

Paper	Title	Page
TUPMA020	PEPPo: Using a Polarized Electron Beam to Produce Polarized Positrons	1878
	A.H. Adeyemi, P.L. Gueye Hampton University, Hampton, Virginia, USA P.A. Adderley, M.M. Ali, H. Areti, J. F. Benesch, L.S. Cardman, J. Clark, S. Covert, C. Cuevas, A. Freyberger, S. Golge, J.M. Grames, P.L. Gueye, J. Hansknecht, P.L. Harrell, C. Hyde, R. Kazimi, Y. Kim, D. Machie, K.L. Mahoney, R.R. Mammei, J.L. McCarter, M.D. McCaughan, M. Poelker, M.L. Stutzman, R. Suleiman, C.-Y. Tsai, D.L. Turner, Y.W. Wang JLab, Newport News, Virginia, USA M.A. Baylac, E. Froidefond, M. Marton, J-F. Muraz, J-S. Real, E. J-M. Voutier LPSC, Grenoble Cedex, France P. Cole, D. Dale, T.A. Forest ISU, Pocatello, Idaho, USA O. Dadoun, A. Variola LAL, Orsay, France D. Dale, Y. Kim IAC, Pocatello, Idaho, USA EF. Fanchini INFN Genova, Genova, Italy S. Golge NCCU, , North Carolina, USA S. Golge, C. Hyde ODU, Norfolk, Virginia, USA J.L. McCarter UVa, Charlottesville, Virginia, USA C.-Y. Tsai Virginia Polytechnic Institute and State University, Blacksburg, Virginia, USA A. Variola IN2P3-CNRS, Orsay, France
	Polarized positron beams have been identified as either an essential or a significant ingredient for the experimental program of both the present and next generation of lepton accelerators (JLab, Super KEK B, ILC, CLIC). An experiment demonstrating a new method for producing polarized positrons has been performed at the Continuous Electron Beam Accelerator Facility at Jefferson Lab. The PEPPo (Polarized Electrons for Polarized Positrons) concept relies on the production of polarized e⁻/e⁺ pairs from the bremsstrahlung radiation of a longitudinally polarized electron beam interacting within a high Z conversion target. PEPPo demonstrated the effective transfer of spin-polarization of an 8.2 MeV/c polarized (P~85%) electron beam to positrons produced in varying thickness tungsten production targets, and collected and measured in the range of 3.1 to 6.2 MeV/c. In comparison to other methods this technique reveals a new pathway for producing either high energy or thermal polarized positron beams using a relatively low polarized electron beam energy (~10MeV) .This presentation will describe the PEPPo concept, the motivations of the experiment and high positron polarization achieved.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-TUPMA020
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MOPMA025	CSR Induced Microbunching Gain Estimation including Transient Effects in Transport and Recirculation Arcs	596
	C.-Y. Tsai Virginia Polytechnic Institute and State University, Blacksburg, Virginia, USA D. Douglas, R. Li, C. Tennant JLab, Newport News, Virginia, USA
	Funding: Authored by Jefferson Science Associates, LLC under U.S. DOE Contract No. DE-AC05-06OR23177. The coherent synchrotron radiation (CSR) of a high brightness electron beam traversing a series of dipoles, such as transport or recirculation arcs, may result in the microbunching instability (μBI). To accurately quantify the direct consequence of this effect, we further extend our previously developed semi-analytical simulation [C. -Y. Tsai et al., FEL Conference 2014 (THP022)] to include more relevant coherent radiation models than the steady-state free-space CSR impedance, such as the entrance and exit transient effects, which derive from upstream beam entering to and exiting from individual dipoles and propagating across the elements to downstream straight sections. Then we semi-analytically solve the linearized Vlasov equation for the amplification factor. The resultant gain functions and spectra for our example lattices are presented and compared with particle tracking simulation. Some underlying physics with inclusion of these effects are also discussed.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-MOPMA025
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MOPMN004	CSR Impedance for Non-Ultrarelativistic Beams	709
	R. Li JLab, Newport News, Virginia, USA C.-Y. Tsai Virginia Polytechnic Institute and State University, Blacksburg, Virginia, USA
	Funding: This work is supported by Jefferson Science Associates, LLC under U.S. DOE Contract No. DE-AC05-06OR23177. For the analysis of the coherent synchrotron radiation (CSR) induced microbunching gain in the low energy regime, such as when a high-brightness electron beam is transported through a low-energy merger in an energy-recovery linac (ERL) design, it is necessary to extend the CSR impedance expression in the ultrarelativistic limit to the non-ultrarelativistic regime. This paper presents our analysis of CSR impedance for general beam energies.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-MOPMN004
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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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Paper

Title

Page

PEPPo: Using a Polarized Electron Beam to Produce Polarized Positrons

1878

A.H. Adeyemi, P.L. Gueye
Hampton University, Hampton, Virginia, USA
P.A. Adderley, M.M. Ali, H. Areti, J. F. Benesch, L.S. Cardman, J. Clark, S. Covert, C. Cuevas, A. Freyberger, S. Golge, J.M. Grames, P.L. Gueye, J. Hansknecht, P.L. Harrell, C. Hyde, R. Kazimi, Y. Kim, D. Machie, K.L. Mahoney, R.R. Mammei, J.L. McCarter, M.D. McCaughan, M. Poelker, M.L. Stutzman, R. Suleiman, C.-Y. Tsai, D.L. Turner, Y.W. Wang
JLab, Newport News, Virginia, USA
M.A. Baylac, E. Froidefond, M. Marton, J-F. Muraz, J-S. Real, E. J-M. Voutier
LPSC, Grenoble Cedex, France
P. Cole, D. Dale, T.A. Forest
ISU, Pocatello, Idaho, USA
O. Dadoun, A. Variola
LAL, Orsay, France
D. Dale, Y. Kim
IAC, Pocatello, Idaho, USA
EF. Fanchini
INFN Genova, Genova, Italy
S. Golge
NCCU, , North Carolina, USA
S. Golge, C. Hyde
ODU, Norfolk, Virginia, USA
J.L. McCarter
UVa, Charlottesville, Virginia, USA
C.-Y. Tsai
Virginia Polytechnic Institute and State University, Blacksburg, Virginia, USA
A. Variola
IN2P3-CNRS, Orsay, France

Polarized positron beams have been identified as either an essential or a significant ingredient for the experimental program of both the present and next generation of lepton accelerators (JLab, Super KEK B, ILC, CLIC). An experiment demonstrating a new method for producing polarized positrons has been performed at the Continuous Electron Beam Accelerator Facility at Jefferson Lab. The PEPPo (Polarized Electrons for Polarized Positrons) concept relies on the production of polarized e⁻/e⁺ pairs from the bremsstrahlung radiation of a longitudinally polarized electron beam interacting within a high Z conversion target. PEPPo demonstrated the effective transfer of spin-polarization of an 8.2 MeV/c polarized (P~85%) electron beam to positrons produced in varying thickness tungsten production targets, and collected and measured in the range of 3.1 to 6.2 MeV/c. In comparison to other methods this technique reveals a new pathway for producing either high energy or thermal polarized positron beams using a relatively low polarized electron beam energy (~10MeV) .This presentation will describe the PEPPo concept, the motivations of the experiment and high positron polarization achieved.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-TUPMA020

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MOPMA025

CSR Induced Microbunching Gain Estimation including Transient Effects in Transport and Recirculation Arcs

596

C.-Y. Tsai
Virginia Polytechnic Institute and State University, Blacksburg, Virginia, USA
D. Douglas, R. Li, C. Tennant
JLab, Newport News, Virginia, USA

Funding: Authored by Jefferson Science Associates, LLC under U.S. DOE Contract No. DE-AC05-06OR23177.
The coherent synchrotron radiation (CSR) of a high brightness electron beam traversing a series of dipoles, such as transport or recirculation arcs, may result in the microbunching instability (μBI). To accurately quantify the direct consequence of this effect, we further extend our previously developed semi-analytical simulation [C. -Y. Tsai et al., FEL Conference 2014 (THP022)] to include more relevant coherent radiation models than the steady-state free-space CSR impedance, such as the entrance and exit transient effects, which derive from upstream beam entering to and exiting from individual dipoles and propagating across the elements to downstream straight sections. Then we semi-analytically solve the linearized Vlasov equation for the amplification factor. The resultant gain functions and spectra for our example lattices are presented and compared with particle tracking simulation. Some underlying physics with inclusion of these effects are also discussed.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-MOPMA025

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MOPMN004

CSR Impedance for Non-Ultrarelativistic Beams

709

R. Li
JLab, Newport News, Virginia, USA
C.-Y. Tsai
Virginia Polytechnic Institute and State University, Blacksburg, Virginia, USA

Funding: This work is supported by Jefferson Science Associates, LLC under U.S. DOE Contract No. DE-AC05-06OR23177.
For the analysis of the coherent synchrotron radiation (CSR) induced microbunching gain in the low energy regime, such as when a high-brightness electron beam is transported through a low-energy merger in an energy-recovery linac (ERL) design, it is necessary to extend the CSR impedance expression in the ultrarelativistic limit to the non-ultrarelativistic regime. This paper presents our analysis of CSR impedance for general beam energies.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-MOPMN004

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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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