IPAC2016 - Classification: 01 Circular and Linear Colliders / A19 Electron-Hadron Colliders

Paper	Title	Page
WEPMW006	First Design of a Proton Collimation System for 50 TeV FCC-hh	2423
	M. Fiascaris, R. Bruce, D. Mirarchi, S. Redaelli CERN, Geneva, Switzerland
	We present studies aimed at defining a first conceptual solution for a collimation system for the hadron-hadron option for the Future Circular Collider (FCC-hh). The baseline collimation layout is based on the scaling of the present LHC collimation system to the FCC-hh energy. It currently includes a dedicated betatron cleaning insertion as well as collimators in the experimental insertions to protect the inner triplets. An aperture model for the FCC-hh is defined and the geometrical acceptance is calculated at top energy taking into account mechanical and optics imperfections. Based on these studies the collimator settings needed to protect the machine are defined. The performance of the collimation system is then assessed with particle tracking simulation tools assuming a perfect machine.
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WEPMW012	Injection Optics for the JLEIC Ion Collider Ring	2445
	V.S. Morozov, Y.S. Derbenev, F. Lin, F.C. Pilat, G.H. Wei, Y. Zhang JLab, Newport News, Virginia, USA Y. Cai, Y. Nosochkov, M.K. Sullivan, M.-H. Wang SLAC, Menlo Park, California, USA
	Funding: * Work supported by the U.S. DOE Contract DE-AC02-76SF00515. ** Authored by Jefferson Science Associates, LLC under U.S. DOE Contracts No. DE-AC05-06OR23177 and DE-AC02-06CH11357. The Jefferson Lab Electron-Ion Collider (JLEIC) will accelerate protons and ions from 8 GeV to 100 GeV. A very low beta function at the Interaction Point (IP) is needed to achieve the required luminosity. One consequence of the low beta optics is that the beta function in the final focusing (FF) quadrupoles is extremely high. This leads to a large beam size in these magnets as well as strong sensitivity to errors which limits the dynamic aperture. These effects are stronger at injection energy where the beam size is maximum, and therefore very large aperture FF magnets are required to allow a large dynamic aperture. A standard solution is a relaxed injection optics with IP beta function large enough to provide a reasonable FF aperture. This also reduces the effects of FF errors resulting in a larger dynamic aperture at injection. We describe the ion ring injection optics design as well as a beta-squeeze transition from the injection to collision optics.
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WEPMW013	Bunch Splitting Simulations for the JLEIC Ion Collider Ring	2448
	B.R.P. Gamage, T. Satogata ODU, Norfolk, Virginia, USA T. Satogata JLab, Newport News, Virginia, USA
	We describe the bunch splitting strategies for the proposed JLEIC ion collider ring at Jefferson Lab. This complex requires an unprecedented 9:6832 bunch splitting, performed in several stages. We outline the problem and current results, optimized with ESME including general parameterization of 1:2 bunch splitting for JLEIC parameters.
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WEPMW014	Development of the Electron Cooling Simulation Program for JLEIC	2451
	H. Zhang, J. Chen, R. Li, Y. Zhang JLab, Newport News, Virginia, USA H. Huang, L. Luo ODU, Norfolk, Virginia, USA
	Funding: Work supported by the Department of Energy, Laboratory Directed Research and Development Funding, under Contract No. DE-AC05-06OR23177 In the JLab Electron Ion Collider (JLEIC) project the traditional electron cooling technique is used to reduce the ion beam emittance at the booster ring, and to compensate the intrabeam scattering effect and maintain the ion beam emittance during collision at the collider ring. A new electron cooling process simulation program has been developed to fulfill the requirements of the JLEIC electron cooler design. The new program allows the users to calculate the electron cooling rate and simulate the cooling process with either DC or bunched electron beam to cool either coasting or bunched ion beam. It has been benchmarked with BETACOOL in aspect of accuracy and efficiency. In typical electron cooling process of JLEIC, the two programs agree very well and we have seen a significant improvement of computational speed using the new one. Being adaptive to the modern multicore hardware makes it possible to further enhance the efficiency for computationally intensive problems. The new program is being actively used in the electron cooling study and cooler design for JLEIC. We will present our models and some simulation results in this paper.
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WEPMW015	Evaluation and Compensation of Detector Solenoid Effects in the JLEIC	2454
	G.H. Wei, F. Lin, V.S. Morozov, F.C. Pilat, Y. Zhang JLab, Newport News, Virginia, USA
	Funding: Authored by Jefferson Science Associates, LLC under U.S. DOE Contracts No. DE-AC05-06OR23177 and DE-AC02-06CH11357. Work supported also by the U.S. DOE Contract DE-AC02-76SF00515. The JLEIC detector solenoid has a strong 3 T field in the IR area, and its tails extend over a range of several meters. One of the main effects of the solenoid field is coupling of the horizontal and vertical betatron motions which must be corrected in order to preserve the dynamical stability and beam spot size match at the IP. Additional effects include influence on the orbit and dispersion caused by the angle between the solenoid axis and the beam orbit. Meanwhile it affects ion polarization breaking the figure-8 spin symmetry. Crab dynamics further complicates the picture. All of these effects have to be compensated or accounted for. The proposed correction system is equivalent to the Rotating Frame Method. However, it does not involve physical rotation of elements. It provides local compensation of the solenoid effects independently for each side of the IR. It includes skew quadrupoles, dipole correctors and anti-solenoids to cancel perturbations to the orbit and linear optics. The skew quadrupoles and FFQ together generate an effect equivalent to adjustable rotation angle to do the decoupling task. Details of all of the correction systems are presented.
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WEPMW016	Towards a Small Emittance Design of the JLEIC Electron Collider Ring	2457
	F. Lin, Y.S. Derbenev, A. Hutton, V.S. Morozov, F.C. Pilat, Y. Zhang JLab, Newport News, Virginia, USA
	Funding: Authored by Jefferson Science Associates, LLC under U.S. DOE Contract No. DE-AC05-06OR23177 and DE-AC02-06CH11357. The electron collider ring of the Jefferson Lab Electron-Ion Collider (JLEIC) is designed to provide an electron beam with a small beam size at the IP for collisions with an ion beam in order to reach a desired high luminosity. For a chosen beta-star at the IP, electron beam size is determined by the equilibrium emittance that can be obtained through a linear optics design. This paper briefly describes the baseline design of the electron collider ring reusing PEP-II components and considering their parameters (such as dipole sagitta, magnet field strengths and acceptable synchrotron radiation power) and reports a few approaches to reducing the equilibrium emittance in the electron collider ring.
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WEPMW017	Ion Beam Polarization Dynamics in the 8 Gev Booster of the Jleic Project at Jlab	2460
	V.S. Morozov, Y.S. Derbenev, F. Lin, Y. Zhang JLab, Newport News, Virginia, USA Y. Filatov MIPT, Dolgoprudniy, Moscow Region, Russia A.M. Kondratenko, M.A. Kondratenko Science and Technique Laboratory Zaryad, Novosibirsk, Russia
	Funding: Authored by Jefferson Science Associates, LLC under U.S. DOE Contracts No. DE-AC05-06OR23177 and DE-AC02-06CH11357. In the Jefferson Lab's Electron-Ion Collider (JLEIC) project, an injector of polarized ions into the collider ring is a superconducting 8 GeV booster. Both figure-8 and racetrack booster versions were considered. Our analysis showed that the figure-8 ring configuration allows one to preserve the polarization of any ion species during beam acceleration using only small longitudinal field with an integral less than 0.5 Tm. In the racetrack booster, to preserve the polarization of ions with the exception of deuterons, it suffices to use a solenoidal Siberian snake with a maximum field integral of 30 Tm. To preserve deuteron polarization, we propose to use arc magnets for the race-track booster structure with a field ramp rate of the order of 1 T/s. We calculate deuteron and proton beam polarizations in both the figure-8 and racetrack boosters including alignment errors of their magnetic elements using the Zgoubi code.
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WEPMW019	Study of Beam Synchronization at JLEIC	2463
	V.S. Morozov, Y.S. Derbenev, J. Guo, A. Hutton, Y. Zhang JLab, Newport News, Virginia, USA
	Funding: Authored by Jefferson Science Associates, LLC under U.S. DOE Contracts No. DE-AC05-06OR23177 and DE-AC02-06CH11357. The ion collider ring of Jefferson Lab's Electron-Ion Collider (JLEIC) accommodates a wide range of ion energies, from 20 to 100 GeV for protons or from 8 to 40 GeV per nucleon for lead ions. In this medium energy range, ions are not fully relativistic, which means values of their relativistic beta are slightly below 1, leading to an energy dependence of revolution time of the collider ring. On the other hand, electrons with energy 3 GeV and above are already ultra-relativistic such that their speeds are effectively equal to the speed of light. The difference in speeds of colliding electrons and ions in JLEIC, when translated into a path-length difference necessary to maintain the same timing between electron and ion bunches, is quite large. In this paper, we explore schemes for synchronizing the electron and ion bunches at a collision point as the ion energy is varied.
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WEPMW022	Multi-Cell RF-Dipole Deflecting and Crabbing Cavity	2469
	S.U. De Silva, J.R. Delayen, H. Park ODU, Norfolk, Virginia, USA
	Single cell superconducting rf-dipole cavities operating at 400 MHz, 499 MHz and 750 MHz have been designed, fabricated and successfully tested at cryogenic temperatures. These cavities have been shown to have attractive rf properties: high deflecting gradients, low electric and magnetic peak surface fields, and high shunt impedance. The single cell rf-dipole geometry has no lower order modes and has widely separated higher order mode spectrum. In this study we are investigating a multi-cell superconducting rf-dipole cavity operating at 952.6 MHz intended for the Jefferson Lab Energy Electron-Ion Collider. The analysis investigates the dependence of beam aperture variation and other cavity parameters on rf properties including cavity gradient, surface fields, shunt impedance and higher order mode separation.
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WEPMW023	Higher Luminosity eRHIC Ring-Ring Options and Upgrade	2472
	R.B. Palmer, J.S. Berg, M. Blaskiewicz, A.V. Fedotov, C. Montag, B. Parker, H. Witte BNL, Upton, Long Island, New York, USA
	Funding: This manuscript has been authored by employees of Brookhaven Science Associates, LLC under Contract No. DE-SC0012704 with the U.S. Department of Energy. Lower risk ring-ring alternatives to the BNL linac-ling~[linacring] eRHIC electron ion collider (EIC) are discussed. The baseline from the Ring-Ring Working Group~[ringring] has a peak proton-electron luminosity of ≈§I{1.2e33}{cm^-2.s^-1}. An option has final focus quadrupoles starting immediately after the detector at 4.5~m, instead of at 32~m in the baseline. This allows the use of lower β^*s. It also uses more, 720, lower intensity, bunches, giving reduced IBS emittance growth and requiring only low energy pre-cooling. It has a peak luminosity of ≈§I{7e33}{cm^-2.s^-1}. An upgrade of this option, requiring magnetic, or coherent, electron cooling, has 1440 bunches and peak luminosity of ≈§I{15e33}{cm^-2.s^-1}.
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WEPMW025	Optimizing the Design of Linear Non-scaling Fixed Field Alternating Gradient Arcs for the Electron Rings of eRHIC	2475
	J.S. Berg BNL, Upton, Long Island, New York, USA
	Funding: This manuscript has been authored by employees of Brookhaven Science Associates, LLC under Contract No. DE-SC0012704 with the U.S. Department of Energy. I describe a process for producing optimal linear non-scaling fixed field alternating gradient (FFAG) arc designs for the electron rings of eRHIC, an electron-ion collider in the RHIC tunnel at Brookhaven National Laboratory. The electrons are accelerated in two FFAG rings (low and high energy), which in addition to the arcs optimized here, contain straight sections, splitter/combiner sections, and a linac shared between the rings. The optimization process I use has two layers, an inner one meeting constraints and an outer optimization that minimizes a target function. The target function is an approximation to the FFAG arc cost, for which I give the function used and the basis for that choice. While reducing synchrotron radiation is important, I show that optimizing for synchrotron radiation alone leads to significant cost an performance penalties for the rest of the machine design for very little reduction in synchrotron radiation. I describe important constraints on the design, in particular minimum drift lengths, maximum and minimum tunes, and clearance from the beam to the beam pipe. Finally, I present possible eRHIC FFAG parameters resulting from this optimization.
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WEPMW026	Beam-Beam Simulation With Crab-Cavities for Erhic	2479
	Y. Luo, Y. Hao, Y.C. Jing, V. Ptitsyn, D. Trbojevic BNL, Upton, Long Island, New York, USA
	Funding: Work supported by Brookhaven Science Associates, LLC under Contract No. DE-AC02-98CH10886 with the U.S. Department of Energy. To avoid the luminosity loss due to cross-angle collision, crab cavities are being considered for the electron-ion collider designs at Brookhaven National Laboratory. In this article, we study the effects of crab cavities on the proton beam dynamics without and with beam-beam interactions. Dynamic apertures are to be calculated with various parameters of crab cavities. To minimize the distortion from a single crab cavity, harmonic crab cavities are also considered.
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WEPMW027	The ERL-based Design of Electron-Hadron Collider eRHIC	2482
	V. Ptitsyn, E.C. Aschenauer, I. Ben-Zvi, J.S. Berg, M. Blaskiewicz, S.J. Brooks, K.A. Brown, J.C. Brutus, O.V. Chubar, A.V. Fedotov, D.M. Gassner, H. Hahn, Y. Hao, A. Hershcovitch, H. Huang, W.A. Jackson, Y.C. Jing, R.F. Lambiase, V. Litvinenko, C. Liu, Y. Luo, G.J. Mahler, B. Martin, G.T. McIntyre, W. Meng, F. Méot, T.A. Miller, M.G. Minty, B. Parker, I. Pinayev, V.H. Ranjbar, T. Roser, J. Skaritka, R. Than, P. Thieberger, D. Trbojevic, N. Tsoupas, J.E. Tuozzolo, E. Wang, G. Wang, H. Witte, Q. Wu, C. Xu, W. Xu, A. Zaltsman BNL, Upton, Long Island, New York, USA S.A. Belomestnykh Fermilab, Batavia, Illinois, USA
	Funding: Work supported by Brookhaven Science Associates, LLC under Contract No. DE-AC02-98CH10886 with the U.S. Department of Energy. Recent developments of the ERL-based design of future high luminosity electron-hadron collider eRHIC focused on balancing technological risks present in the design versus the design cost. As a result a lower risk design has been adopted at moderate cost increase. The modifications include a change of the main linac RF frequency, reduced number of SRF cavity types and modified electron spin transport using a spin rotator. A luminosity-staged approach is being explored with a Nominal design (L ~ 10³³ cm^-2 s^-1) that employs reduced electron current and could possibly be based on classical electron cooling, and then with the Ultimate design (L > 10³⁴ cm^-2 s^-1) that uses higher electron current and an innovative cooling technique (CeC). The paper describes the recent design modifications, and presents the full status of the eRHIC ERL-based design.
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WEPMW039	JLEIC SRF Cavity RF Design	2522
	S. Wang, J. Guo, R.A. Rimmer, H. Wang JLab, Newport News, Virginia, USA
	The initial design of a low higher order modes (HOM) impedance superconducting RF (SRF) cavity is presented in this paper. The design of this SRF cavity is for the proposed Jefferson Lab Electron Ion Collider (JLEIC). The electron ring of JLEIC will operate with electrons of 3 to 10 GeV energy. The ion ring of JLEIC will operate with protons of up to 100 GeV energy. The bunch lengths in both rings are ~12 mm (RMS). In order to maintain the short bunch length in the ion ring, SRF cavities are adopted to provide large enough gradient. In the first phase of JLEIC, the PEP II RF cavities will be reused in the electron ring to lower the initial cost. The frequency of the SRF cavities is chosen to be the second harmonic of PEP II cavities, 952.6 MHz. In the second phase of JLEIC, the same frequency SRF cavities may replace the normal conducting PEP II cavities to achieve higher luminosity at high energy. At low energies, the synchrotron radiation damping effect is quite weak, to avoid the coupled bunch instability caused by the intense closely-spaced electron bunches, low HOM impedance of the SRF cavities combined with longitudinal feedback system will be necessary.
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WEPMW043	Frequency Scaling Study of Crab Cavity for Future Colliders with Crab Crossing	2532
	Y. Hao, V. Ptitsyn BNL, Upton, Long Island, New York, USA
	Funding: Work supported by Brookhaven Science Associates, LLC under Contract No. DE-AC02-98CH10886 with the U.S. Department of Energy. Crab crossing is an essential concept in the newly proposed colliders or the upgrades. It enables crossing angles to achieve lower β^* without a loss of luminosity. The frequency of the crab cavity shall be chosen with various considerations, including the luminosity degradation, emittance growth due to synchro-beta resonances and RF noises. We use the figure of merits and related simulation to establish the frequency scaling relations with important beam parameters, which guide the choice of crab cavity frequency for new designs.
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WEPOY057	The 2015 eRHIC Ring-Ring Design	3126
	C. Montag, E.C. Aschenauer, J. Beebe-Wang, J.S. Berg, M. Blaskiewicz, J.M. Brennan, A.V. Fedotov, W. Fischer, V. Litvinenko, R.B. Palmer, B. Parker, S. Peggs, V. Ptitsyn, V.H. Ranjbar, S. Tepikian, D. Trbojevic, F.J. Willeke BNL, Upton, Long Island, New York, USA
	Funding: Work supported by Brookhaven Science Associates, LLC under Contract No. DE-AC02-98CH10886 with the U.S. Department of Energy. To reduce the technical risk of the future electron-ion collider eRHIC currently under study at BNL, the ring-ring scheme has been revisited over the summer of 2015. The goal of this study was a design that covers the full center-of-mass energy range from 32 to 141 GeV with an initial luminosity around 10³³ cm^-2 sec^-1, upgradeable to 10³⁴ cm^-2 sec^-1 later on. In this presentation the baseline design will be presented, and future upgrades will be discussed.
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WEPOY058	Design of the 2015 Erhic Ring-Ring Interaction Region	3129
	C. Montag, B. Parker BNL, Upton, Long Island, New York, USA
	Funding: Work supported by Brookhaven Science Associates, LLC under Contract No. DE-AC02-98CH10886 with the U.S. Department of Energy. The 2015 ring-ring design study of the electron-ion collider eRHIC aims at an e-p luminosity around 10³³ cm^-2 sec^-1 over a center-of-mass energy range from 32 to 141 GeV, while at the same time providing the required detector geometry and acceptance for the proposed physics program. The latest interaction region design will be presented.
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Paper

Title

Page

First Design of a Proton Collimation System for 50 TeV FCC-hh

2423

M. Fiascaris, R. Bruce, D. Mirarchi, S. Redaelli
CERN, Geneva, Switzerland

We present studies aimed at defining a first conceptual solution for a collimation system for the hadron-hadron option for the Future Circular Collider (FCC-hh). The baseline collimation layout is based on the scaling of the present LHC collimation system to the FCC-hh energy. It currently includes a dedicated betatron cleaning insertion as well as collimators in the experimental insertions to protect the inner triplets. An aperture model for the FCC-hh is defined and the geometrical acceptance is calculated at top energy taking into account mechanical and optics imperfections. Based on these studies the collimator settings needed to protect the machine are defined. The performance of the collimation system is then assessed with particle tracking simulation tools assuming a perfect machine.

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WEPMW012

Injection Optics for the JLEIC Ion Collider Ring

2445

V.S. Morozov, Y.S. Derbenev, F. Lin, F.C. Pilat, G.H. Wei, Y. Zhang
JLab, Newport News, Virginia, USA
Y. Cai, Y. Nosochkov, M.K. Sullivan, M.-H. Wang
SLAC, Menlo Park, California, USA

Funding: * Work supported by the U.S. DOE Contract DE-AC02-76SF00515. ** Authored by Jefferson Science Associates, LLC under U.S. DOE Contracts No. DE-AC05-06OR23177 and DE-AC02-06CH11357.
The Jefferson Lab Electron-Ion Collider (JLEIC) will accelerate protons and ions from 8 GeV to 100 GeV. A very low beta function at the Interaction Point (IP) is needed to achieve the required luminosity. One consequence of the low beta optics is that the beta function in the final focusing (FF) quadrupoles is extremely high. This leads to a large beam size in these magnets as well as strong sensitivity to errors which limits the dynamic aperture. These effects are stronger at injection energy where the beam size is maximum, and therefore very large aperture FF magnets are required to allow a large dynamic aperture. A standard solution is a relaxed injection optics with IP beta function large enough to provide a reasonable FF aperture. This also reduces the effects of FF errors resulting in a larger dynamic aperture at injection. We describe the ion ring injection optics design as well as a beta-squeeze transition from the injection to collision optics.

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WEPMW013

Bunch Splitting Simulations for the JLEIC Ion Collider Ring

2448

B.R.P. Gamage, T. Satogata
ODU, Norfolk, Virginia, USA
T. Satogata
JLab, Newport News, Virginia, USA

We describe the bunch splitting strategies for the proposed JLEIC ion collider ring at Jefferson Lab. This complex requires an unprecedented 9:6832 bunch splitting, performed in several stages. We outline the problem and current results, optimized with ESME including general parameterization of 1:2 bunch splitting for JLEIC parameters.

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WEPMW014

Development of the Electron Cooling Simulation Program for JLEIC

2451

H. Zhang, J. Chen, R. Li, Y. Zhang
JLab, Newport News, Virginia, USA
H. Huang, L. Luo
ODU, Norfolk, Virginia, USA

Funding: Work supported by the Department of Energy, Laboratory Directed Research and Development Funding, under Contract No. DE-AC05-06OR23177
In the JLab Electron Ion Collider (JLEIC) project the traditional electron cooling technique is used to reduce the ion beam emittance at the booster ring, and to compensate the intrabeam scattering effect and maintain the ion beam emittance during collision at the collider ring. A new electron cooling process simulation program has been developed to fulfill the requirements of the JLEIC electron cooler design. The new program allows the users to calculate the electron cooling rate and simulate the cooling process with either DC or bunched electron beam to cool either coasting or bunched ion beam. It has been benchmarked with BETACOOL in aspect of accuracy and efficiency. In typical electron cooling process of JLEIC, the two programs agree very well and we have seen a significant improvement of computational speed using the new one. Being adaptive to the modern multicore hardware makes it possible to further enhance the efficiency for computationally intensive problems. The new program is being actively used in the electron cooling study and cooler design for JLEIC. We will present our models and some simulation results in this paper.

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WEPMW015

Evaluation and Compensation of Detector Solenoid Effects in the JLEIC

2454

G.H. Wei, F. Lin, V.S. Morozov, F.C. Pilat, Y. Zhang
JLab, Newport News, Virginia, USA

Funding: Authored by Jefferson Science Associates, LLC under U.S. DOE Contracts No. DE-AC05-06OR23177 and DE-AC02-06CH11357. Work supported also by the U.S. DOE Contract DE-AC02-76SF00515.
The JLEIC detector solenoid has a strong 3 T field in the IR area, and its tails extend over a range of several meters. One of the main effects of the solenoid field is coupling of the horizontal and vertical betatron motions which must be corrected in order to preserve the dynamical stability and beam spot size match at the IP. Additional effects include influence on the orbit and dispersion caused by the angle between the solenoid axis and the beam orbit. Meanwhile it affects ion polarization breaking the figure-8 spin symmetry. Crab dynamics further complicates the picture. All of these effects have to be compensated or accounted for. The proposed correction system is equivalent to the Rotating Frame Method. However, it does not involve physical rotation of elements. It provides local compensation of the solenoid effects independently for each side of the IR. It includes skew quadrupoles, dipole correctors and anti-solenoids to cancel perturbations to the orbit and linear optics. The skew quadrupoles and FFQ together generate an effect equivalent to adjustable rotation angle to do the decoupling task. Details of all of the correction systems are presented.

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WEPMW016

Towards a Small Emittance Design of the JLEIC Electron Collider Ring

2457

F. Lin, Y.S. Derbenev, A. Hutton, V.S. Morozov, F.C. Pilat, Y. Zhang
JLab, Newport News, Virginia, USA

Funding: Authored by Jefferson Science Associates, LLC under U.S. DOE Contract No. DE-AC05-06OR23177 and DE-AC02-06CH11357.
The electron collider ring of the Jefferson Lab Electron-Ion Collider (JLEIC) is designed to provide an electron beam with a small beam size at the IP for collisions with an ion beam in order to reach a desired high luminosity. For a chosen beta-star at the IP, electron beam size is determined by the equilibrium emittance that can be obtained through a linear optics design. This paper briefly describes the baseline design of the electron collider ring reusing PEP-II components and considering their parameters (such as dipole sagitta, magnet field strengths and acceptable synchrotron radiation power) and reports a few approaches to reducing the equilibrium emittance in the electron collider ring.

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WEPMW017

Ion Beam Polarization Dynamics in the 8 Gev Booster of the Jleic Project at Jlab

2460

V.S. Morozov, Y.S. Derbenev, F. Lin, Y. Zhang
JLab, Newport News, Virginia, USA
Y. Filatov
MIPT, Dolgoprudniy, Moscow Region, Russia
A.M. Kondratenko, M.A. Kondratenko
Science and Technique Laboratory Zaryad, Novosibirsk, Russia

Funding: Authored by Jefferson Science Associates, LLC under U.S. DOE Contracts No. DE-AC05-06OR23177 and DE-AC02-06CH11357.
In the Jefferson Lab's Electron-Ion Collider (JLEIC) project, an injector of polarized ions into the collider ring is a superconducting 8 GeV booster. Both figure-8 and racetrack booster versions were considered. Our analysis showed that the figure-8 ring configuration allows one to preserve the polarization of any ion species during beam acceleration using only small longitudinal field with an integral less than 0.5 Tm. In the racetrack booster, to preserve the polarization of ions with the exception of deuterons, it suffices to use a solenoidal Siberian snake with a maximum field integral of 30 Tm. To preserve deuteron polarization, we propose to use arc magnets for the race-track booster structure with a field ramp rate of the order of 1 T/s. We calculate deuteron and proton beam polarizations in both the figure-8 and racetrack boosters including alignment errors of their magnetic elements using the Zgoubi code.

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WEPMW019

Study of Beam Synchronization at JLEIC

2463

V.S. Morozov, Y.S. Derbenev, J. Guo, A. Hutton, Y. Zhang
JLab, Newport News, Virginia, USA

Funding: Authored by Jefferson Science Associates, LLC under U.S. DOE Contracts No. DE-AC05-06OR23177 and DE-AC02-06CH11357.
The ion collider ring of Jefferson Lab's Electron-Ion Collider (JLEIC) accommodates a wide range of ion energies, from 20 to 100 GeV for protons or from 8 to 40 GeV per nucleon for lead ions. In this medium energy range, ions are not fully relativistic, which means values of their relativistic beta are slightly below 1, leading to an energy dependence of revolution time of the collider ring. On the other hand, electrons with energy 3 GeV and above are already ultra-relativistic such that their speeds are effectively equal to the speed of light. The difference in speeds of colliding electrons and ions in JLEIC, when translated into a path-length difference necessary to maintain the same timing between electron and ion bunches, is quite large. In this paper, we explore schemes for synchronizing the electron and ion bunches at a collision point as the ion energy is varied.

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WEPMW022

Multi-Cell RF-Dipole Deflecting and Crabbing Cavity

2469

S.U. De Silva, J.R. Delayen, H. Park
ODU, Norfolk, Virginia, USA

Single cell superconducting rf-dipole cavities operating at 400 MHz, 499 MHz and 750 MHz have been designed, fabricated and successfully tested at cryogenic temperatures. These cavities have been shown to have attractive rf properties: high deflecting gradients, low electric and magnetic peak surface fields, and high shunt impedance. The single cell rf-dipole geometry has no lower order modes and has widely separated higher order mode spectrum. In this study we are investigating a multi-cell superconducting rf-dipole cavity operating at 952.6 MHz intended for the Jefferson Lab Energy Electron-Ion Collider. The analysis investigates the dependence of beam aperture variation and other cavity parameters on rf properties including cavity gradient, surface fields, shunt impedance and higher order mode separation.

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WEPMW023

Higher Luminosity eRHIC Ring-Ring Options and Upgrade

2472

R.B. Palmer, J.S. Berg, M. Blaskiewicz, A.V. Fedotov, C. Montag, B. Parker, H. Witte
BNL, Upton, Long Island, New York, USA

Funding: This manuscript has been authored by employees of Brookhaven Science Associates, LLC under Contract No. DE-SC0012704 with the U.S. Department of Energy.
Lower risk ring-ring alternatives to the BNL linac-ling~[linacring] eRHIC electron ion collider (EIC) are discussed. The baseline from the Ring-Ring Working Group~[ringring] has a peak proton-electron luminosity of ≈§I{1.2e33}{cm^-2.s^-1}. An option has final focus quadrupoles starting immediately after the detector at 4.5~m, instead of at 32~m in the baseline. This allows the use of lower β^*s. It also uses more, 720, lower intensity, bunches, giving reduced IBS emittance growth and requiring only low energy pre-cooling. It has a peak luminosity of ≈§I{7e33}{cm^-2.s^-1}. An upgrade of this option, requiring magnetic, or coherent, electron cooling, has 1440 bunches and peak luminosity of ≈§I{15e33}{cm^-2.s^-1}.

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WEPMW025

Optimizing the Design of Linear Non-scaling Fixed Field Alternating Gradient Arcs for the Electron Rings of eRHIC

2475

J.S. Berg
BNL, Upton, Long Island, New York, USA

Funding: This manuscript has been authored by employees of Brookhaven Science Associates, LLC under Contract No. DE-SC0012704 with the U.S. Department of Energy.
I describe a process for producing optimal linear non-scaling fixed field alternating gradient (FFAG) arc designs for the electron rings of eRHIC, an electron-ion collider in the RHIC tunnel at Brookhaven National Laboratory. The electrons are accelerated in two FFAG rings (low and high energy), which in addition to the arcs optimized here, contain straight sections, splitter/combiner sections, and a linac shared between the rings. The optimization process I use has two layers, an inner one meeting constraints and an outer optimization that minimizes a target function. The target function is an approximation to the FFAG arc cost, for which I give the function used and the basis for that choice. While reducing synchrotron radiation is important, I show that optimizing for synchrotron radiation alone leads to significant cost an performance penalties for the rest of the machine design for very little reduction in synchrotron radiation. I describe important constraints on the design, in particular minimum drift lengths, maximum and minimum tunes, and clearance from the beam to the beam pipe. Finally, I present possible eRHIC FFAG parameters resulting from this optimization.

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WEPMW026

Beam-Beam Simulation With Crab-Cavities for Erhic

2479

Y. Luo, Y. Hao, Y.C. Jing, V. Ptitsyn, D. Trbojevic
BNL, Upton, Long Island, New York, USA

Funding: Work supported by Brookhaven Science Associates, LLC under Contract No. DE-AC02-98CH10886 with the U.S. Department of Energy.
To avoid the luminosity loss due to cross-angle collision, crab cavities are being considered for the electron-ion collider designs at Brookhaven National Laboratory. In this article, we study the effects of crab cavities on the proton beam dynamics without and with beam-beam interactions. Dynamic apertures are to be calculated with various parameters of crab cavities. To minimize the distortion from a single crab cavity, harmonic crab cavities are also considered.

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WEPMW027

The ERL-based Design of Electron-Hadron Collider eRHIC

2482

V. Ptitsyn, E.C. Aschenauer, I. Ben-Zvi, J.S. Berg, M. Blaskiewicz, S.J. Brooks, K.A. Brown, J.C. Brutus, O.V. Chubar, A.V. Fedotov, D.M. Gassner, H. Hahn, Y. Hao, A. Hershcovitch, H. Huang, W.A. Jackson, Y.C. Jing, R.F. Lambiase, V. Litvinenko, C. Liu, Y. Luo, G.J. Mahler, B. Martin, G.T. McIntyre, W. Meng, F. Méot, T.A. Miller, M.G. Minty, B. Parker, I. Pinayev, V.H. Ranjbar, T. Roser, J. Skaritka, R. Than, P. Thieberger, D. Trbojevic, N. Tsoupas, J.E. Tuozzolo, E. Wang, G. Wang, H. Witte, Q. Wu, C. Xu, W. Xu, A. Zaltsman
BNL, Upton, Long Island, New York, USA
S.A. Belomestnykh
Fermilab, Batavia, Illinois, USA

Funding: Work supported by Brookhaven Science Associates, LLC under Contract No. DE-AC02-98CH10886 with the U.S. Department of Energy.
Recent developments of the ERL-based design of future high luminosity electron-hadron collider eRHIC focused on balancing technological risks present in the design versus the design cost. As a result a lower risk design has been adopted at moderate cost increase. The modifications include a change of the main linac RF frequency, reduced number of SRF cavity types and modified electron spin transport using a spin rotator. A luminosity-staged approach is being explored with a Nominal design (L ~ 10³³ cm^-2 s^-1) that employs reduced electron current and could possibly be based on classical electron cooling, and then with the Ultimate design (L > 10³⁴ cm^-2 s^-1) that uses higher electron current and an innovative cooling technique (CeC). The paper describes the recent design modifications, and presents the full status of the eRHIC ERL-based design.

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WEPMW039

JLEIC SRF Cavity RF Design

2522

S. Wang, J. Guo, R.A. Rimmer, H. Wang
JLab, Newport News, Virginia, USA

The initial design of a low higher order modes (HOM) impedance superconducting RF (SRF) cavity is presented in this paper. The design of this SRF cavity is for the proposed Jefferson Lab Electron Ion Collider (JLEIC). The electron ring of JLEIC will operate with electrons of 3 to 10 GeV energy. The ion ring of JLEIC will operate with protons of up to 100 GeV energy. The bunch lengths in both rings are ~12 mm (RMS). In order to maintain the short bunch length in the ion ring, SRF cavities are adopted to provide large enough gradient. In the first phase of JLEIC, the PEP II RF cavities will be reused in the electron ring to lower the initial cost. The frequency of the SRF cavities is chosen to be the second harmonic of PEP II cavities, 952.6 MHz. In the second phase of JLEIC, the same frequency SRF cavities may replace the normal conducting PEP II cavities to achieve higher luminosity at high energy. At low energies, the synchrotron radiation damping effect is quite weak, to avoid the coupled bunch instability caused by the intense closely-spaced electron bunches, low HOM impedance of the SRF cavities combined with longitudinal feedback system will be necessary.

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WEPMW043

Frequency Scaling Study of Crab Cavity for Future Colliders with Crab Crossing

2532

Y. Hao, V. Ptitsyn
BNL, Upton, Long Island, New York, USA

Funding: Work supported by Brookhaven Science Associates, LLC under Contract No. DE-AC02-98CH10886 with the U.S. Department of Energy.
Crab crossing is an essential concept in the newly proposed colliders or the upgrades. It enables crossing angles to achieve lower β^* without a loss of luminosity. The frequency of the crab cavity shall be chosen with various considerations, including the luminosity degradation, emittance growth due to synchro-beta resonances and RF noises. We use the figure of merits and related simulation to establish the frequency scaling relations with important beam parameters, which guide the choice of crab cavity frequency for new designs.

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WEPOY057

The 2015 eRHIC Ring-Ring Design

3126

C. Montag, E.C. Aschenauer, J. Beebe-Wang, J.S. Berg, M. Blaskiewicz, J.M. Brennan, A.V. Fedotov, W. Fischer, V. Litvinenko, R.B. Palmer, B. Parker, S. Peggs, V. Ptitsyn, V.H. Ranjbar, S. Tepikian, D. Trbojevic, F.J. Willeke
BNL, Upton, Long Island, New York, USA

Funding: Work supported by Brookhaven Science Associates, LLC under Contract No. DE-AC02-98CH10886 with the U.S. Department of Energy.
To reduce the technical risk of the future electron-ion collider eRHIC currently under study at BNL, the ring-ring scheme has been revisited over the summer of 2015. The goal of this study was a design that covers the full center-of-mass energy range from 32 to 141 GeV with an initial luminosity around 10³³ cm^-2 sec^-1, upgradeable to 10³⁴ cm^-2 sec^-1 later on. In this presentation the baseline design will be presented, and future upgrades will be discussed.

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WEPOY058

Design of the 2015 Erhic Ring-Ring Interaction Region

3129

C. Montag, B. Parker
BNL, Upton, Long Island, New York, USA

Funding: Work supported by Brookhaven Science Associates, LLC under Contract No. DE-AC02-98CH10886 with the U.S. Department of Energy.
The 2015 ring-ring design study of the electron-ion collider eRHIC aims at an e-p luminosity around 10³³ cm^-2 sec^-1 over a center-of-mass energy range from 32 to 141 GeV, while at the same time providing the required detector geometry and acceptance for the proposed physics program. The latest interaction region design will be presented.

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