ERL2019 - Table of Session: TUCOXBS (WG2: ERL beam dynamics and instrumentation)

Paper	Title	Page
TUCOXBS01	Beam Halo in Energy Recovery Linacs	23
	O.A. Tanaka KEK, Ibaraki, Japan
	The beam halo mitigation is a very important challenge for reliable and safe operation of a high energy machine. Since Energy Recovery Linacs (ERLs) are known to produce high energy electron beams of high virtual power and high density, the beam halo and related beam losses should be properly mitigated to avoid a direct damage of the equipment, an unacceptable increase in the vacuum pressure, a radiation activation of the accelerator components etc. To keep the operation stable, one needs to address all possible beam halo formation mechanisms, including those unique to each machine that can generate beam halo. Present report is dedicated to the beam halo related activities at the Compact ERL at KEK, and our operational experience with respect to the beam halo.
	Slides TUCOXBS01 [4.480 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-ERL2019-TUCOXBS01
About •	paper received ※ 16 September 2019 paper accepted ※ 01 November 2019 issue date ※ 24 June 2020
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TUCOXBS03	Beam Dynamics Layout of the MESA ERL	28
	F. Hug, K. Aulenbacher, D. Simon, C.P. Stoll, S.D.W. Thomas KPH, Mainz, Germany K. Aulenbacher GSI, Darmstadt, Germany K. Aulenbacher HIM, Mainz, Germany
	Funding: This work has been supported by DFG through the PRISMA+ cluster of excellence EXC 2118/2019 and by the European Union’s Horizon 2020 Research and Innovation programme under Grant Agreement No 730871. The MESA project is currently under construction at Johannes Gutenberg-Universität Mainz. It will be used for high precision particle physics experiments in two different operation modes: external beam (EB) mode (0.15 mA; 155 MeV) and energy recovery (ERL) mode (1 mA; 10⁵ MeV). The recirculating main linac follows the concept of a double sided accelerator design with vertical stacking of return arcs. Up to three recirculations are possible. Acceleration is done by four TESLA/XFEL 9-cell SRF cavities located in two modified ELBE cryomodules. Within this contribution the recirculation optics for MESA will be presented. Main goals are achieving best energy spread at the experimental setups in recirculating ERL and non-ERL operation and providing small beta-functions within the cryomodules for minimizing HOM excitation at high beam currents.
	Slides TUCOXBS03 [5.077 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-ERL2019-TUCOXBS03
About •	paper received ※ 16 September 2019 paper accepted ※ 06 November 2019 issue date ※ 24 June 2020
Export •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

TUCOXBS04	The LHeC ERL - Optics and Performance Optimizations	34
	S.A. Bogacz JLab, Newport News, Virginia, USA
	Funding: Work has been authored by Jefferson Science Associates, LLC under Contract No. DE-AC05-06OR23177 with the U.S. Department of Energy. The LHeC 60 GeV ERL baseline design features a racetrack composed of two linacs, completed with 6 return arcs, including vertical spreaders and recombines at the arcs ends. Here, we consider a design strategy aiming at ’downsizing’ the ERL e.g. to 50 GeV, while preserving its performance in terms of synchrotron radiation effects. This results in a significant reduction of accelerator components. The optimization explores tuning of each arc, which takes into account the impact of synchrotron radiation at different energies. At the highest energy, it is crucial to minimize the emittance dilution; therefore, the cells are tuned to minimize the dispersion in the bending sections, as in a theoretical minimum emittance lattice. At the lowest energy, one compensates for the bunch elongation with a negative momentum compaction setup which, additionally, contains the beam size. The intermediate energy arcs are tuned to a double bend achromat lattice, offering a compromise between isochronicity and emittance dilution. Finally, a feasibility of a ’dogbone’ ERL is discussed.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-ERL2019-TUCOXBS04
About •	paper received ※ 16 September 2019 paper accepted ※ 07 November 2019 issue date ※ 24 June 2020
Export •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

TUCOXBS05	Beam Timing and Cavity Phasing	39
	R.M. Koscica, N. Banerjee, G.H. Hoffstaetter, W. Lou, G.T. Premawardhana Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA
	In a multi-pass Energy Recovery Linac (ERL), each cavity must regain all energy expended from beam acceleration during beam deceleration. The beam should also achieve specific energy targets during each loop that returns it to the linac. To satisfy the energy recovery and loop requirements, one must specify the phase and voltage of cavity fields, and one must control the beam flight times through the return loops. Adequate values for these parameters can be found by using a full scale numerical optimization program. If symmetry is imposed in beam time and energy during acceleration and deceleration, the number of parameters needed decreases, simplifying the optimization. As an example, symmetric models of the Cornell BNL ERL Test Accelerator (CBETA) are considered. Energy recovery results from recent CBETA single-turn tests are presented, as well as multi-turn solutions that satisfy CBETA optimization targets of loop energy and zero cavity loading.
	Slides TUCOXBS05 [5.186 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-ERL2019-TUCOXBS05
About •	paper received ※ 13 September 2019 paper accepted ※ 01 November 2019 issue date ※ 24 June 2020
Export •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

Paper

Title

Page

Beam Halo in Energy Recovery Linacs

23

O.A. Tanaka
KEK, Ibaraki, Japan

The beam halo mitigation is a very important challenge for reliable and safe operation of a high energy machine. Since Energy Recovery Linacs (ERLs) are known to produce high energy electron beams of high virtual power and high density, the beam halo and related beam losses should be properly mitigated to avoid a direct damage of the equipment, an unacceptable increase in the vacuum pressure, a radiation activation of the accelerator components etc. To keep the operation stable, one needs to address all possible beam halo formation mechanisms, including those unique to each machine that can generate beam halo. Present report is dedicated to the beam halo related activities at the Compact ERL at KEK, and our operational experience with respect to the beam halo.

Slides TUCOXBS01 [4.480 MB]

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-ERL2019-TUCOXBS01

About •

paper received ※ 16 September 2019 paper accepted ※ 01 November 2019 issue date ※ 24 June 2020

Export •

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

TUCOXBS03

Beam Dynamics Layout of the MESA ERL

28

F. Hug, K. Aulenbacher, D. Simon, C.P. Stoll, S.D.W. Thomas
KPH, Mainz, Germany
K. Aulenbacher
GSI, Darmstadt, Germany
K. Aulenbacher
HIM, Mainz, Germany

Funding: This work has been supported by DFG through the PRISMA+ cluster of excellence EXC 2118/2019 and by the European Union’s Horizon 2020 Research and Innovation programme under Grant Agreement No 730871.
The MESA project is currently under construction at Johannes Gutenberg-Universität Mainz. It will be used for high precision particle physics experiments in two different operation modes: external beam (EB) mode (0.15 mA; 155 MeV) and energy recovery (ERL) mode (1 mA; 10⁵ MeV). The recirculating main linac follows the concept of a double sided accelerator design with vertical stacking of return arcs. Up to three recirculations are possible. Acceleration is done by four TESLA/XFEL 9-cell SRF cavities located in two modified ELBE cryomodules. Within this contribution the recirculation optics for MESA will be presented. Main goals are achieving best energy spread at the experimental setups in recirculating ERL and non-ERL operation and providing small beta-functions within the cryomodules for minimizing HOM excitation at high beam currents.

Slides TUCOXBS03 [5.077 MB]

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-ERL2019-TUCOXBS03

About •

paper received ※ 16 September 2019 paper accepted ※ 06 November 2019 issue date ※ 24 June 2020

Export •

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

TUCOXBS04

The LHeC ERL - Optics and Performance Optimizations

34

S.A. Bogacz
JLab, Newport News, Virginia, USA

Funding: Work has been authored by Jefferson Science Associates, LLC under Contract No. DE-AC05-06OR23177 with the U.S. Department of Energy.
The LHeC 60 GeV ERL baseline design features a racetrack composed of two linacs, completed with 6 return arcs, including vertical spreaders and recombines at the arcs ends. Here, we consider a design strategy aiming at ’downsizing’ the ERL e.g. to 50 GeV, while preserving its performance in terms of synchrotron radiation effects. This results in a significant reduction of accelerator components. The optimization explores tuning of each arc, which takes into account the impact of synchrotron radiation at different energies. At the highest energy, it is crucial to minimize the emittance dilution; therefore, the cells are tuned to minimize the dispersion in the bending sections, as in a theoretical minimum emittance lattice. At the lowest energy, one compensates for the bunch elongation with a negative momentum compaction setup which, additionally, contains the beam size. The intermediate energy arcs are tuned to a double bend achromat lattice, offering a compromise between isochronicity and emittance dilution. Finally, a feasibility of a ’dogbone’ ERL is discussed.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-ERL2019-TUCOXBS04

About •

paper received ※ 16 September 2019 paper accepted ※ 07 November 2019 issue date ※ 24 June 2020

Export •

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

TUCOXBS05

Beam Timing and Cavity Phasing

39

R.M. Koscica, N. Banerjee, G.H. Hoffstaetter, W. Lou, G.T. Premawardhana
Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA

In a multi-pass Energy Recovery Linac (ERL), each cavity must regain all energy expended from beam acceleration during beam deceleration. The beam should also achieve specific energy targets during each loop that returns it to the linac. To satisfy the energy recovery and loop requirements, one must specify the phase and voltage of cavity fields, and one must control the beam flight times through the return loops. Adequate values for these parameters can be found by using a full scale numerical optimization program. If symmetry is imposed in beam time and energy during acceleration and deceleration, the number of parameters needed decreases, simplifying the optimization. As an example, symmetric models of the Cornell BNL ERL Test Accelerator (CBETA) are considered. Energy recovery results from recent CBETA single-turn tests are presented, as well as multi-turn solutions that satisfy CBETA optimization targets of loop energy and zero cavity loading.

Slides TUCOXBS05 [5.186 MB]

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-ERL2019-TUCOXBS05

About •

paper received ※ 13 September 2019 paper accepted ※ 01 November 2019 issue date ※ 24 June 2020

Export •

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