IPAC2019 - List of Authors (Smith, K.S.)

Paper	Title	Page
MOZZPLS1	eRHIC Design Overview	45
	C. Montag, G. Bassi, J. Beebe-Wang, J.S. Berg, M. Blaskiewicz, A. Blednykh, J.M. Brennan, S.J. Brooks, K.A. Brown, K.A. Drees, A.V. Fedotov, W. Fischer, D.M. Gassner, W. Guo, A. Hershcovitch, C. Hetzel, D. Holmes, H. Huang, W.A. Jackson, J. Kewisch, Y. Li, C. Liu, H. Lovelace III, Y. Luo, F. Méot, M.G. Minty, R.B. Palmer, B. Parker, S. Peggs, V. Ptitsyn, V.H. Ranjbar, G. Robert-Demolaize, S. Seletskiy, V.V. Smaluk, K.S. Smith, S. Tepikian, P. Thieberger, D. Trbojevic, N. Tsoupas, S. Verdú-Andrés, W.-T. Weng, F.J. Willeke, H. Witte, Q. Wu, W. Xu, A. Zaltsman, W. Zhang BNL, Upton, Long Island, New York, USA E. Gianfelice-Wendt Fermilab, Batavia, Illinois, USA Y. Hao FRIB, East Lansing, Michigan, USA
	Funding: Work supported by Brookhaven Science Associates, LLC under Contract No. DE-AC02-98CH10886 with the U.S. Department of Energy. The Electron-Ion Collider (EIC) is being envisioned as the next facility to be constructed by the DOE Nuclear Physics program. Brookhaven National Laboratory is proposing eRHIC, a facility based on the existing RHIC complex as a cost effective realization of the EIC project with a peak luminosity of 10³⁴ cm^-2 sec^-1. An electron storage ring with an energy range from 5 to 18 GeV will be added in the existing RHIC tunnel. A spin-transparent rapid-cycling synchrotron (RCS) will serve as a full-energy polarized electron injector. Recent design improvements include reduction of the IR magnet strengths to avoid the necessity for Nb₃Sn magnets, and a novel hadron injection scheme to maximize the integrated luminosity. We will provide an overview of this proposed project and present the current design status.
	Slides MOZZPLS1 [5.428 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-MOZZPLS1
About •	paper received ※ 14 May 2019 paper accepted ※ 20 May 2019 issue date ※ 21 June 2019
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MOPMP051	56 MHz SRF System for SPHENIX Experiments at RHIC	562
	Q. Wu, M. Blaskiewicz, K. Mernick, S. Polizzo, F. Severino, K.S. Smith, T. Xin BNL, Upton, Long Island, New York, USA
	Funding: Work supported by by Brookhaven Science Associates, LLC under Contract No. DE-AC02-98CH10886 with the U.S. Department of Energy The sPHENIX experiment is a proposal for a new detector at the Relativistic Heavy Ion Collider (RHIC), that plans to expand on discoveries made by RHIC’s existing STAR and PHENIX research groups. To minimize the luminosity outside the 20 cm vertex detector and keeping the radiation to other detector components as low as possible, a 56 MHz SRF system is added to the existing RHIC RF systems to compress the bunches with less beam loss. The existing 56 MHz SRF cavity was commissioned in previous RHIC runs, and contributed to the luminosity at a voltage of 300kV with thermal limitations from the Higher Order Mode coupler at high field, and at 1MV while using its fundamental damper for HOM damping. In this paper, we will analyze and compare the effect of different RF systems at various scenarios, and discuss possible solutions to the Higher Order Mode (HOM) damping scheme to bring the cavity to 2 MV.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-MOPMP051
About •	paper received ※ 15 May 2019 paper accepted ※ 20 May 2019 issue date ※ 21 June 2019
Export •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

MOPRB072	eRHIC in Electron-Ion Operation	738
	W. Fischer, E.C. Aschenauer, E.N. Beebe, M. Blaskiewicz, K.A. Brown, D. Bruno, K.A. Drees, C.J. Gardner, H. Huang, T. Kanesue, C. Liu, M. Mapes, G.T. McIntyre, M.G. Minty, C. Montag, S.K. Nayak, M. Okamura, V. Ptitsyn, D. Raparia, J. Sandberg, K.S. Smith, P. Thieberger, N. Tsoupas, J.E. Tuozzolo, F.J. Willeke, A. Zaltsman, A. Zelenski BNL, Upton, Long Island, New York, USA
	Funding: Work supported by U.S. DOE under contract No DE-AC02-98CH10886 with the U.S. Department of Energy. The design effort for the electron-ion collider eRHIC has concentrated on electron-proton collisions at the highest luminosities over the widest possible energy range. The present design also provides for electron-nucleon peak luminosities of up to 4.7·10³³ cm^-2s⁻¹ with strong hadron cooling, and up to 1.7·10³³ cm^-2s⁻¹ with stochastic cooling. Here we discuss the performance limitations and design choices for electron-ion collisions that are different from the electron-proton collisions. These include the ion bunch preparation in the injector chain, acceleration and intrabeam scattering in the hadron ring, path length adjustment and synchronization with the electron ring, stochastic cooling upgrades, machine protection upgrades, and operation with polarized electron beams colliding with either unpolarized ion beams or polarized He-3.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-MOPRB072
About •	paper received ※ 14 May 2019 paper accepted ※ 20 May 2019 issue date ※ 21 June 2019
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MOPRB085	First Results from Commissioning of Low Energy RHIC Electron Cooler (LEReC)	769
	D. Kayran, Z. Altinbas, D. Bruno, M.R. Costanzo, K.A. Drees, A.V. Fedotov, W. Fischer, M. Gaowei, D.M. Gassner, X. Gu, R.L. Hulsart, P. Inacker, J.P. Jamilkowski, Y.C. Jing, J. Kewisch, C.J. Liaw, C. Liu, J. Ma, K. Mernick, T.A. Miller, M.G. Minty, L.K. Nguyen, M.C. Paniccia, I. Pinayev, V. Ptitsyn, V. Schoefer, S. Seletskiy, F. Severino, T.C. Shrey, L. Smart, K.S. Smith, A. Sukhanov, P. Thieberger, J.E. Tuozzolo, E. Wang, G. Wang, A. Zaltsman, H. Zhao, Z. Zhao 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 brand new non-magnetized bunched beam electron cooler (LEReC) [1] has been built to provide luminosity improvement for Beam Energy Scan II (BES-II) physics program at the Relativistic Heavy Ion Collider (RHIC) BES-II [2]. The LEReC accelerator includes a photocathode DC gun, a laser system, a photocathode delivery system, magnets, beam diagnostics, a SRF booster cavity, and a set of Normal Conducting RF cavities to provide sufficient flexibility to tune the beam in the longitudinal phase space. This high-current high-power accelerator was successfully commissioned in period of March -September 2018. Beam quality suitable for cooling has been demonstrated. In this paper we discuss beam commissioning results and experience learned during commissioning. [1] A. Fedotov et al., ’Status of bunched beam electron cooler LEReC’ in these proceedings. [2] C.Liu et al., ’Improving luminosity of Beam Energy Scan II at RHIC’ in these proceedings.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-MOPRB085
About •	paper received ※ 15 May 2019 paper accepted ※ 20 May 2019 issue date ※ 21 June 2019
Export •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

MOPRB093	eRHIC Electron Ring Design Status	794
	C. Montag, M. Blaskiewicz, C. Hetzel, D. Holmes, Y. Li, H. Lovelace III, V. Ptitsyn, K.S. Smith, S. Tepikian, F.J. Willeke, H. Witte, W. Xu BNL, Upton, Long Island, New York, USA E. Gianfelice-Wendt 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. For the proposed electron-ion collider eRHIC, an electron storage ring will be installed in the existing RHIC tunnel. To reach the high luminosity of up to 10³⁴ cm^-2 sec^-1, beam currents up to 2.5A have to be stored. Besides high luminosity the physics program requires spin polarization levels of 70 percent, with both spin "up" and spin "down" orientations present in the fill. This is only feasible by using a full-energy spin polarized injector that replaces bunches faster than the depolarization rate. To limit the repetition rate of that injector to about one hertz, the polarization lifetime in the storage ring has to be maximized by proper spin matching and countermeasures for the machine misalignments. We will give an overview of the electron storage ring design.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-MOPRB093
About •	paper received ※ 13 May 2019 paper accepted ※ 21 May 2019 issue date ※ 21 June 2019
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TUPTS078	Coherent Electron Cooling (CeC) Experiment at RHIC: Status and Plans	2101
	V. Litvinenko, K. Mihara Stony Brook University, Stony Brook, USA Z. Altinbas, J.C. Brutus, A. Di Lieto, D.M. Gassner, T. Hayes, P. Inacker, J.P. Jamilkowski, Y.C. Jing, R. Kellermann, J. Ma, G.J. Mahler, M. Mapes, R.J. Michnoff, T.A. Miller, M.G. Minty, G. Narayan, M.C. Paniccia, D. Phillips, I. Pinayev, S.K. Seberg, F. Severino, J. Skaritka, L. Smart, K.S. Smith, Z. Sorrell, R. Than, J.E. Tuozzolo, E. Wang, G. Wang, Y.H. Wu, B.P. Xiao, T. Xin, A. Zaltsman BNL, Upton, Long Island, New York, USA I. Petrushina SUNY SB, Stony Brook, New York, USA K. Shih SBU, Stony Brook, New York, USA
	Funding: Work supported by Brookhaven Science Associates, LLC under Contract No. DE-AC02-98CH10886 with the U.S. Department of Energy and NSF Grant No. PHY-141525 We will present currents status of the CeC experiment at RHIC and discuss plans for future. Special focus will be given to unexpected experimental results obtained during RHIC Run 18 and discovery of a previously unknown type of microwave instability. We called this new phenomenon micro-bunching Plasma Cascade Instability (PCI). Our plan for future experiments includes suppressing this instability in the CeC accelerator and using it as a broad-band amplifier in the CeC system.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-TUPTS078
About •	paper received ※ 19 May 2019 paper accepted ※ 22 May 2019 issue date ※ 21 June 2019
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TUPTS079	Overcoming Multipacting Barriers in SRF Photoinjectors	2105
	I. Petrushina SUNY SB, Stony Brook, New York, USA V. Litvinenko, G. Narayan, I. Pinayev, F. Severino, K.S. Smith BNL, Upton, Long Island, New York, USA V. Litvinenko Stony Brook University, Stony Brook, USA
	Superconducting RF (SRF) photoinjectors are considered to be a potential breakthrough in the area of high brightness electron sources. However, there is always the very important question of the compatibility of SRF cavities and high quantum efficiency (QE) photocathodes. A deposition of active elements from high QE photocathodes on the surface of a cavity makes it more vulnerable to multipacting (MP) and could affect the operation of an SRF gun. On the other side, MP can significantly reduce the lifetime of a photocathode. It is well known in the SRF community that a strong coupling, high forward power and sufficient cleanliness of cavity walls are the key components to overcome a low-level MP zone. In this paper we present a theoretical model of passing a MP barrier which could help estimate the desirable conditions for successful operation of an SRF gun. We demonstrate our results for the 113 MHz SRF photo-injector for Coherent electron Cooling (CeC) alongside with the experimental observations and 3D simulations of the MP discharge in the cavity. The results of the theoretical model and simulations show good agreement with the experimental results, and demonstrate that, if approached carefully, MP zones can be easily passed without any harm to the photocathode.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-TUPTS079
About •	paper received ※ 14 May 2019 paper accepted ※ 23 May 2019 issue date ※ 21 June 2019
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WEPRB102	Correction of Crosstalk Effect in the LEReC Booster Cavity	3051
	B.P. Xiao, K. Mernick, F. Severino, K.S. Smith, T. Xin, W. Xu BNL, Upton, Long Island, New York, USA
	Funding: Work is supported by Brookhaven Science Associates, LLC under contract No. DE-AC02-98CH10886 with the US DOE. The Linac of Low Energy RHIC electron Cooler (LEReC) is designed to deliver a 1.6 MeV to 2.6 MeV electron beam, with peak-to-peak dp/p less than 7·10^-4. The booster cavity is the major accelerating component in LEReC, which is a 0.4 cell cavity operating at 2 K, with a maximum energy gain of 2.2 MeV. It is modified from the Energy Recovery Linac (ERL) photocathode gun, with fundamental power coupler (FPC), pickup coupler (PU) and higher order mode (HOM) coupler close to each other. The direct coupling between FPC and PU induced crosstalk effect in this cavity. This effect is simulated and measured, and is further corrected using low level RF (LLRF) to meet the energy spread requirement.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-WEPRB102
About •	paper received ※ 14 May 2019 paper accepted ※ 23 May 2019 issue date ※ 21 June 2019
Export •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

Paper

Title

Page

eRHIC Design Overview

45

C. Montag, G. Bassi, J. Beebe-Wang, J.S. Berg, M. Blaskiewicz, A. Blednykh, J.M. Brennan, S.J. Brooks, K.A. Brown, K.A. Drees, A.V. Fedotov, W. Fischer, D.M. Gassner, W. Guo, A. Hershcovitch, C. Hetzel, D. Holmes, H. Huang, W.A. Jackson, J. Kewisch, Y. Li, C. Liu, H. Lovelace III, Y. Luo, F. Méot, M.G. Minty, R.B. Palmer, B. Parker, S. Peggs, V. Ptitsyn, V.H. Ranjbar, G. Robert-Demolaize, S. Seletskiy, V.V. Smaluk, K.S. Smith, S. Tepikian, P. Thieberger, D. Trbojevic, N. Tsoupas, S. Verdú-Andrés, W.-T. Weng, F.J. Willeke, H. Witte, Q. Wu, W. Xu, A. Zaltsman, W. Zhang
BNL, Upton, Long Island, New York, USA
E. Gianfelice-Wendt
Fermilab, Batavia, Illinois, USA
Y. Hao
FRIB, East Lansing, Michigan, USA

Funding: Work supported by Brookhaven Science Associates, LLC under Contract No. DE-AC02-98CH10886 with the U.S. Department of Energy.
The Electron-Ion Collider (EIC) is being envisioned as the next facility to be constructed by the DOE Nuclear Physics program. Brookhaven National Laboratory is proposing eRHIC, a facility based on the existing RHIC complex as a cost effective realization of the EIC project with a peak luminosity of 10³⁴ cm^-2 sec^-1. An electron storage ring with an energy range from 5 to 18 GeV will be added in the existing RHIC tunnel. A spin-transparent rapid-cycling synchrotron (RCS) will serve as a full-energy polarized electron injector. Recent design improvements include reduction of the IR magnet strengths to avoid the necessity for Nb₃Sn magnets, and a novel hadron injection scheme to maximize the integrated luminosity. We will provide an overview of this proposed project and present the current design status.

Slides MOZZPLS1 [5.428 MB]

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-MOZZPLS1

About •

paper received ※ 14 May 2019 paper accepted ※ 20 May 2019 issue date ※ 21 June 2019

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MOPMP051

56 MHz SRF System for SPHENIX Experiments at RHIC

562

Q. Wu, M. Blaskiewicz, K. Mernick, S. Polizzo, F. Severino, K.S. Smith, T. Xin
BNL, Upton, Long Island, New York, USA

Funding: Work supported by by Brookhaven Science Associates, LLC under Contract No. DE-AC02-98CH10886 with the U.S. Department of Energy
The sPHENIX experiment is a proposal for a new detector at the Relativistic Heavy Ion Collider (RHIC), that plans to expand on discoveries made by RHIC’s existing STAR and PHENIX research groups. To minimize the luminosity outside the 20 cm vertex detector and keeping the radiation to other detector components as low as possible, a 56 MHz SRF system is added to the existing RHIC RF systems to compress the bunches with less beam loss. The existing 56 MHz SRF cavity was commissioned in previous RHIC runs, and contributed to the luminosity at a voltage of 300kV with thermal limitations from the Higher Order Mode coupler at high field, and at 1MV while using its fundamental damper for HOM damping. In this paper, we will analyze and compare the effect of different RF systems at various scenarios, and discuss possible solutions to the Higher Order Mode (HOM) damping scheme to bring the cavity to 2 MV.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-MOPMP051

About •

paper received ※ 15 May 2019 paper accepted ※ 20 May 2019 issue date ※ 21 June 2019

Export •

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

MOPRB072

eRHIC in Electron-Ion Operation

738

W. Fischer, E.C. Aschenauer, E.N. Beebe, M. Blaskiewicz, K.A. Brown, D. Bruno, K.A. Drees, C.J. Gardner, H. Huang, T. Kanesue, C. Liu, M. Mapes, G.T. McIntyre, M.G. Minty, C. Montag, S.K. Nayak, M. Okamura, V. Ptitsyn, D. Raparia, J. Sandberg, K.S. Smith, P. Thieberger, N. Tsoupas, J.E. Tuozzolo, F.J. Willeke, A. Zaltsman, A. Zelenski
BNL, Upton, Long Island, New York, USA

Funding: Work supported by U.S. DOE under contract No DE-AC02-98CH10886 with the U.S. Department of Energy.
The design effort for the electron-ion collider eRHIC has concentrated on electron-proton collisions at the highest luminosities over the widest possible energy range. The present design also provides for electron-nucleon peak luminosities of up to 4.7·10³³ cm^-2s⁻¹ with strong hadron cooling, and up to 1.7·10³³ cm^-2s⁻¹ with stochastic cooling. Here we discuss the performance limitations and design choices for electron-ion collisions that are different from the electron-proton collisions. These include the ion bunch preparation in the injector chain, acceleration and intrabeam scattering in the hadron ring, path length adjustment and synchronization with the electron ring, stochastic cooling upgrades, machine protection upgrades, and operation with polarized electron beams colliding with either unpolarized ion beams or polarized He-3.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-MOPRB072

About •

paper received ※ 14 May 2019 paper accepted ※ 20 May 2019 issue date ※ 21 June 2019

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MOPRB085

First Results from Commissioning of Low Energy RHIC Electron Cooler (LEReC)

769

D. Kayran, Z. Altinbas, D. Bruno, M.R. Costanzo, K.A. Drees, A.V. Fedotov, W. Fischer, M. Gaowei, D.M. Gassner, X. Gu, R.L. Hulsart, P. Inacker, J.P. Jamilkowski, Y.C. Jing, J. Kewisch, C.J. Liaw, C. Liu, J. Ma, K. Mernick, T.A. Miller, M.G. Minty, L.K. Nguyen, M.C. Paniccia, I. Pinayev, V. Ptitsyn, V. Schoefer, S. Seletskiy, F. Severino, T.C. Shrey, L. Smart, K.S. Smith, A. Sukhanov, P. Thieberger, J.E. Tuozzolo, E. Wang, G. Wang, A. Zaltsman, H. Zhao, Z. Zhao
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 brand new non-magnetized bunched beam electron cooler (LEReC) [1] has been built to provide luminosity improvement for Beam Energy Scan II (BES-II) physics program at the Relativistic Heavy Ion Collider (RHIC) BES-II [2]. The LEReC accelerator includes a photocathode DC gun, a laser system, a photocathode delivery system, magnets, beam diagnostics, a SRF booster cavity, and a set of Normal Conducting RF cavities to provide sufficient flexibility to tune the beam in the longitudinal phase space. This high-current high-power accelerator was successfully commissioned in period of March -September 2018. Beam quality suitable for cooling has been demonstrated. In this paper we discuss beam commissioning results and experience learned during commissioning.
[1] A. Fedotov et al., ’Status of bunched beam electron cooler LEReC’ in these proceedings.
[2] C.Liu et al., ’Improving luminosity of Beam Energy Scan II at RHIC’ in these proceedings.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-MOPRB085

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paper received ※ 15 May 2019 paper accepted ※ 20 May 2019 issue date ※ 21 June 2019

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MOPRB093

eRHIC Electron Ring Design Status

794

C. Montag, M. Blaskiewicz, C. Hetzel, D. Holmes, Y. Li, H. Lovelace III, V. Ptitsyn, K.S. Smith, S. Tepikian, F.J. Willeke, H. Witte, W. Xu
BNL, Upton, Long Island, New York, USA
E. Gianfelice-Wendt
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.
For the proposed electron-ion collider eRHIC, an electron storage ring will be installed in the existing RHIC tunnel. To reach the high luminosity of up to 10³⁴ cm^-2 sec^-1, beam currents up to 2.5A have to be stored. Besides high luminosity the physics program requires spin polarization levels of 70 percent, with both spin "up" and spin "down" orientations present in the fill. This is only feasible by using a full-energy spin polarized injector that replaces bunches faster than the depolarization rate. To limit the repetition rate of that injector to about one hertz, the polarization lifetime in the storage ring has to be maximized by proper spin matching and countermeasures for the machine misalignments. We will give an overview of the electron storage ring design.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-MOPRB093

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paper received ※ 13 May 2019 paper accepted ※ 21 May 2019 issue date ※ 21 June 2019

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TUPTS078

Coherent Electron Cooling (CeC) Experiment at RHIC: Status and Plans

2101

V. Litvinenko, K. Mihara
Stony Brook University, Stony Brook, USA
Z. Altinbas, J.C. Brutus, A. Di Lieto, D.M. Gassner, T. Hayes, P. Inacker, J.P. Jamilkowski, Y.C. Jing, R. Kellermann, J. Ma, G.J. Mahler, M. Mapes, R.J. Michnoff, T.A. Miller, M.G. Minty, G. Narayan, M.C. Paniccia, D. Phillips, I. Pinayev, S.K. Seberg, F. Severino, J. Skaritka, L. Smart, K.S. Smith, Z. Sorrell, R. Than, J.E. Tuozzolo, E. Wang, G. Wang, Y.H. Wu, B.P. Xiao, T. Xin, A. Zaltsman
BNL, Upton, Long Island, New York, USA
I. Petrushina
SUNY SB, Stony Brook, New York, USA
K. Shih
SBU, Stony Brook, New York, USA

Funding: Work supported by Brookhaven Science Associates, LLC under Contract No. DE-AC02-98CH10886 with the U.S. Department of Energy and NSF Grant No. PHY-141525
We will present currents status of the CeC experiment at RHIC and discuss plans for future. Special focus will be given to unexpected experimental results obtained during RHIC Run 18 and discovery of a previously unknown type of microwave instability. We called this new phenomenon micro-bunching Plasma Cascade Instability (PCI). Our plan for future experiments includes suppressing this instability in the CeC accelerator and using it as a broad-band amplifier in the CeC system.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-TUPTS078

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paper received ※ 19 May 2019 paper accepted ※ 22 May 2019 issue date ※ 21 June 2019

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TUPTS079

Overcoming Multipacting Barriers in SRF Photoinjectors

2105

I. Petrushina
SUNY SB, Stony Brook, New York, USA
V. Litvinenko, G. Narayan, I. Pinayev, F. Severino, K.S. Smith
BNL, Upton, Long Island, New York, USA
V. Litvinenko
Stony Brook University, Stony Brook, USA

Superconducting RF (SRF) photoinjectors are considered to be a potential breakthrough in the area of high brightness electron sources. However, there is always the very important question of the compatibility of SRF cavities and high quantum efficiency (QE) photocathodes. A deposition of active elements from high QE photocathodes on the surface of a cavity makes it more vulnerable to multipacting (MP) and could affect the operation of an SRF gun. On the other side, MP can significantly reduce the lifetime of a photocathode. It is well known in the SRF community that a strong coupling, high forward power and sufficient cleanliness of cavity walls are the key components to overcome a low-level MP zone. In this paper we present a theoretical model of passing a MP barrier which could help estimate the desirable conditions for successful operation of an SRF gun. We demonstrate our results for the 113 MHz SRF photo-injector for Coherent electron Cooling (CeC) alongside with the experimental observations and 3D simulations of the MP discharge in the cavity. The results of the theoretical model and simulations show good agreement with the experimental results, and demonstrate that, if approached carefully, MP zones can be easily passed without any harm to the photocathode.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-TUPTS079

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paper received ※ 14 May 2019 paper accepted ※ 23 May 2019 issue date ※ 21 June 2019

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WEPRB102

Correction of Crosstalk Effect in the LEReC Booster Cavity

3051

B.P. Xiao, K. Mernick, F. Severino, K.S. Smith, T. Xin, W. Xu
BNL, Upton, Long Island, New York, USA

Funding: Work is supported by Brookhaven Science Associates, LLC under contract No. DE-AC02-98CH10886 with the US DOE.
The Linac of Low Energy RHIC electron Cooler (LEReC) is designed to deliver a 1.6 MeV to 2.6 MeV electron beam, with peak-to-peak dp/p less than 7·10^-4. The booster cavity is the major accelerating component in LEReC, which is a 0.4 cell cavity operating at 2 K, with a maximum energy gain of 2.2 MeV. It is modified from the Energy Recovery Linac (ERL) photocathode gun, with fundamental power coupler (FPC), pickup coupler (PU) and higher order mode (HOM) coupler close to each other. The direct coupling between FPC and PU induced crosstalk effect in this cavity. This effect is simulated and measured, and is further corrected using low level RF (LLRF) to meet the energy spread requirement.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-WEPRB102

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paper received ※ 14 May 2019 paper accepted ※ 23 May 2019 issue date ※ 21 June 2019

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