Chuyu Liu - Academia.edu (original) (raw)
Papers by Chuyu Liu
OSTI OAI (U.S. Department of Energy Office of Scientific and Technical Information), May 14, 2017
This report focuses on transverse and longitudinal emittance growth of polarized proton beam due ... more This report focuses on transverse and longitudinal emittance growth of polarized proton beam due to Intra-Beam Scattering (IBS) at RHIC. Simulations are presented which give guidance on the configuration of the RF systems to mitigate IBSinduced emittance growth. In addition, simulated growth rates are compared with measured emittances at injection, which show better agreement in longitudinal than transverse dimension. The results in this report will help us better understand the emittance evolution at injection for current RHIC operations and for future operations (eRHIC).
Physical review accelerators and beams, May 5, 2022
The Beam Energy Scan phase II (BES-II), performed in the Relativistic Heavy Ion Collider (RHIC) f... more The Beam Energy Scan phase II (BES-II), performed in the Relativistic Heavy Ion Collider (RHIC) from 2019 to 2021, explored the phase transition between quark-gluon plasma and hadronic gas. BES-II exceeded the goal of a fourfold increase in the average luminosity over that achieved during Beam Energy Scan phase I (BES-I), at five gold beam energies: 9.8, 7.3, 5.75, 4.59, and 3.85 GeV=nucleon. This was accomplished by addressing several beam dynamics effects, including intrabeam scattering, beam-beam, space charge, beam instability, and field errors induced by superconducting magnet persistent currents. Some of these effects are especially detrimental at low energies. BES-II achievements are presented, and the measures taken to improve RHIC performance are described. These measures span the whole RHIC complex, including ion beam sources, injectors, beam lifetime improvements in RHIC, and operation with the world's first bunched beam Low Energy RHIC electron Cooler (LEReC).
![Research paper thumbnail of Colliders for High Energy and Nuclear Physics [Proceedings]](https://attachments.academia-assets.com/117257134/thumbnails/1.jpg)
](US Particle Accelerator School, 24 Jan - 4 Feb 2022
The Electron-Ion Collider (EIC) at Brookhaven National Laboratory is a high luminosity, ( ∼ 10³⁴ ... more The Electron-Ion Collider (EIC) at Brookhaven National Laboratory is a high luminosity, ( ∼ 10³⁴ \textrm{cm}⁻² \textrm{s}⁻¹ ) accelerator facility colliding polarized electron beam with different ion species ranging from lighter nuclei (proton, deuterium) to heavier nuclei (gold, uranium). Design of a stripline injection kicker for the Hadron Storage Ring (HSR) of EIC for beams with the rigidity of ∼ 81 T-m poses some technical challenges due to expected shorter bunch spacing and higher peak current of EIC. This paper focuses on the optimization of the EIC hadron ring injection kicker. Starting from the 2D cross-section design which includes the selection of electrodes shape, we describe the optimization of the kicker's cross-section. Then we discuss converting this 2D geometry to 3D by adding essential components for the stripline kicker and the 3D optimization techniques that we employed. Finally, we show simulation results for the optimized geometry including wakefields and T...
Since the invention of the electron cooling technique its application to cool hadron beams in col... more Since the invention of the electron cooling technique its application to cool hadron beams in colliders was considered for numerous accelerator physics projects worldwide. However, achieving the required high-brightness electron beams of required quality and cooling of ion beams in collisions was deemed to be challenging. An electron cooling of ion beams employing a high-energy approach with RF-accelerated electron bunches was recently successfully implemented at BNL. It was used to cool ion beams in both collider rings with ion beams in collision. Electron cooling in RHIC became fully operational during the 2020 physics run and led to substantial improvements in luminosity. This presentation will discuss implementation, optimization and challenges of electron cooling for colliding ion beams in RHIC.
The Low Energy RHIC Electron Cooling (LEReC) facility at BNL demonstrated, for the first time, co... more The Low Energy RHIC Electron Cooling (LEReC) facility at BNL demonstrated, for the first time, cooling of ion beams using a bunched electron beam from an SRF accelerating cavity and photoinjector. LEReC is planned to be operational to improve the luminosity of the Beam Energy Scan II physics program in RHIC in the following two years. In order to establish cooling of the RHIC Au ion beam using a 20 mA, 1.6 MeV bunched electron beam; absolute energy, angular and energy spread, trajectory and beam size were precisely matched. A suite of instrumentation was commissioned that includes a variety of current transformers, capacitive pick-up for gun high voltage ripple monitor, BPMs, transverse and longitudinal profile monitors, multi-slit and single-slit scanning emittance stations, time-of-flight and magnetic field related energy measurements, beam halo loss monitors and recombination monitors. The commissioning results and performance of these systems are described, including the latest ...
In order to achieve higher instantaneous and integrated luminosities, the average Au bunch intens... more In order to achieve higher instantaneous and integrated luminosities, the average Au bunch intensity in RHIC has been increased by 30% compared to the preceding Au run. This increase was accomplished by merging bunches in the RHIC injector AGS. Luminosity leveling for one of the two interaction points (IP) with collisions was realized by continuous control of the vertical beam separation. Parallel to RHIC physics operation, the electron beam commissioning of a novel cooling technique with potential application in eRHIC, Coherent electron Cooling as a proof of principle (CeCPoP), was carried out. In addition, a 56 MHz superconducting RF cavity was commissioned and made operational. In this paper we will focus on the RHIC performance during the 2016 Au-Au run.
The brand new non-magnetized bunched beam electron cooler (LEReC) [1] has been built to provide l... more 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.
The design effort for the electron-ion collider eRHIC has concentrated on electron-proton collisi... more 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.
The Electron-Ion Collider (EIC) is being envisioned as the next facility to be constructed by the... more 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.
Precedent to electron cooling commissioning and collisions of Gold at various energies at RHIC in... more Precedent to electron cooling commissioning and collisions of Gold at various energies at RHIC in 2018, the STAR experiment desired an exploration of the chiral magnetic effect in the quark gluon plasma (QGP) with an isobar run, utilizing Ruthenium and Zirconium. Colliding Zr-96 with Zr-96 and Ru-96 with Ru-96 create the same QGP but in a different magnetic field due to the different charges of the Zr (Z=40) and Ru (Z=44) ions. Since the charge difference is only 10%, the experimental program requires exacting store conditions for both ions. These systematic error concerns presented new challenges for the Collider, including frequent reconfiguration of the Collider for the different ion species, and maintaining level amounts of instantaneous and integrated luminosity between two species. Moreover, making beams of Zr-96 and Ru-96 is challenging since the natural abundances of these isotopes are low. Creating viable enriched source material for Zr-96 required assistance processing fro...
Cornell's Lab of Accelerator-based Sciences and Education (CLASSE) and the Collider Accelerat... more Cornell's Lab of Accelerator-based Sciences and Education (CLASSE) and the Collider Accelerator Department (BNL-CAD) are developing the first SRF multi-turn energy recovery linac with Non-Scaling Fixed Field Alternating Gradient (NS-FFAG) racetrack. The existing injector and superconducting linac at Cornell University are installed together with a single NS-FFAG arcs and straight section at the opposite side of the the linac to form an Electron Energy Recovery (ERL) system. Electron beam from the 6 MeV injector is injected into the 36 MeV superconducting linac, and accelerated by four successive passes: from 42 MeV up to 150 MeV using the same NS-FFAG structure made of permanent magnets. After the maximum energy of 150 MeV is reached, the electron beam is brought back to the linac with opposite Radio Frequency (RF) phase. Energy is recovered and reduced to the initial value of 6 MeV with 4 additional passes. There are many novelties: a single NS-FFAG structure, made of permanent...
The low energy RHIC Electron Cooler (LEReC) will be operating with 1.6-2.6 MeV electron beams hav... more The low energy RHIC Electron Cooler (LEReC) will be operating with 1.6-2.6 MeV electron beams having up to 140 kW power. It was determined that under the worst case scenario the missteered electron beam can damage the vacuum chamber and in-vacuum components within 40 us. Hence, the LEReC requires a dedicated fast machine protection system (MPS). The LEReC MPS has been designed and built and currently is under commissioning. In this paper we describe the most recent developments with the LEReC MPS.
As the last step of phase 1 of the beam energy scan (BESI), aimed at the search for the critical ... more As the last step of phase 1 of the beam energy scan (BESI), aimed at the search for the critical point in the QCD phase diagram, RHIC collided gold ions at a beam energy of 7.3 GeV/nucleon during the FY 2014 run. While this particular energy is close to the nominal RHIC injection energy of 9.8 GeV/nucleon, it is nevertheless challenging because it happens to be close to the AGS transition energy, which makes longitudinal beam dynamics during transfer from the AGS to RHIC difficult. We report on machine performance, obstacles and solutions during the FY 2014 low energy run.
Recent developments of the ERL-based design of future high-luminosity electron-hadron collider eR... more 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 ($$L \sim 10^{33} {\rm cm}^2 {\rm s}^{-1}$$) that employs reduced electron current and could possibly be based on classical electron cooling, and then with the Ultimate design ($$L \gt 10^{34} {\rm cm}^{-2} {\rm s}^{-1}$$) 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.
A multiple-pass, high-energy ERL experiment at the JLab CEBAF will be instrumental in providing n... more A multiple-pass, high-energy ERL experiment at the JLab CEBAF will be instrumental in providing necessary information and technology testing for a number of possible future applications and facilities such as Linac-Ring based colliders, which have been designed at BNL (eRHIC) and CERN (LHeC), and also drivers for high-energy FELs and 4th GLS. ER@CEBAF is aimed at investigating 6D optics and beam dynamics issues in ERLs, such as synchrotron radiation effects, emittance preservation, stability, beam losses, multiple-pass orbit control/correction, multiple-pass beam dynamics in the presence of cavity HOMs, BBU and other halo studies, handling of large (SR induced) momentum spread bunches, and development of multiple-beam diagnostics instrumentation. Figure 1: 12 GeV CEBAF recirculating linac. Location of chicane and dump line for ER@CEBAF. Since it was launched 2+ years ago, the project has progressed in defining the necessary modifications to CEBAF (Fig. 1, Tab. 1, 2), including a 4-d...
A collaboration between Cornell University and Brookhaven National Laboratory has designed and is... more A collaboration between Cornell University and Brookhaven National Laboratory has designed and is constructing CBETA, the Cornell-BNL ERL Test Accelerator on the Cornell campus. The ERL technology that has been prototyped at Cornell for many years is being used for this new accelerator, including a DC electron source and an SRF injector Linac with world-record current and normalized brightness in a bunch train, a high-current linac cryomodule optimized for ERLs, a high-power beam stop, and several diagnostics tools for high-current and high-brightness beams. BNL has designed multi-turn ERLs for several purpose, dominantly for the electron beam of eRHIC, its Electron Ion Collider (EIC) project and for the associated fast electron cooling system. Also in JLEIC, the EIC designed at JLAB, an ERL is envisioned to be used for electron cooling. The number of transport lines in an ERL is minimized by using return arcs that are comprised of a Fixed Field Alternating-gradient (FFA) design. Th...
Low Energy RHIC Electron cooler (LEReC) project is presently under commissioning at Brookhaven Na... more Low Energy RHIC Electron cooler (LEReC) project is presently under commissioning at Brookhaven National Laboratory (BNL). LEReC requires high average current up to 85mA and high-quality electron beam [1]. A 400 kV DC gun equipped with a photocathode and laser system has been chosen to provide a source of high-quality electron beams. We started testing the DC gun during the RHIC run 2017. First electron beam from LEReC DC gun was delivered in April 2017 [2]. During the DC gun test critical elements of LEReC such as laser beam system, cathode exchange system, cathode QE lifetime, DC gun stability, beam instrumentation, the high-power beam dump system, machine protection system and controls have been tested. Average current of 10 mA for few hours of operation was reached in August 2017. In this paper we present experimental results and experience learned during the LEReC DC gun beam testing. PURPOSE OF LEReC GUN TEST The gun beam test (see Fig. 1) is the first stage of LEReC commission...
The first part of RHIC Run 15 consisted of ten weeks of polarized proton on proton collisions at ... more The first part of RHIC Run 15 consisted of ten weeks of polarized proton on proton collisions at a beam energy of 100 GeV at two interaction points. In this paper we discuss several of the upgrades to the collider complex that allowed for improved performance. The largest effort consisted in commissioning of the electron lenses, one in each ring, which are designed to compensate one of the two beam-beam interactions experienced by the proton bunches. The e-lenses raise the per bunch intensity at which luminosity becomes beam-beam limited. A new lattice was designed to create the phase advances necessary for a beam-beam compensation with the e-lens, which also has an improved off-momentum dynamic aperture relative to previous runs. In order to take advantage of the new, higher intensity limit without suffering intensity driven emittance deterioration, other features were commissioned including a continuous transverse bunch-by-bunch damper in RHIC and a double harmonic RF cature schem...
OSTI OAI (U.S. Department of Energy Office of Scientific and Technical Information), May 14, 2017
This report focuses on transverse and longitudinal emittance growth of polarized proton beam due ... more This report focuses on transverse and longitudinal emittance growth of polarized proton beam due to Intra-Beam Scattering (IBS) at RHIC. Simulations are presented which give guidance on the configuration of the RF systems to mitigate IBSinduced emittance growth. In addition, simulated growth rates are compared with measured emittances at injection, which show better agreement in longitudinal than transverse dimension. The results in this report will help us better understand the emittance evolution at injection for current RHIC operations and for future operations (eRHIC).
Physical review accelerators and beams, May 5, 2022
The Beam Energy Scan phase II (BES-II), performed in the Relativistic Heavy Ion Collider (RHIC) f... more The Beam Energy Scan phase II (BES-II), performed in the Relativistic Heavy Ion Collider (RHIC) from 2019 to 2021, explored the phase transition between quark-gluon plasma and hadronic gas. BES-II exceeded the goal of a fourfold increase in the average luminosity over that achieved during Beam Energy Scan phase I (BES-I), at five gold beam energies: 9.8, 7.3, 5.75, 4.59, and 3.85 GeV=nucleon. This was accomplished by addressing several beam dynamics effects, including intrabeam scattering, beam-beam, space charge, beam instability, and field errors induced by superconducting magnet persistent currents. Some of these effects are especially detrimental at low energies. BES-II achievements are presented, and the measures taken to improve RHIC performance are described. These measures span the whole RHIC complex, including ion beam sources, injectors, beam lifetime improvements in RHIC, and operation with the world's first bunched beam Low Energy RHIC electron Cooler (LEReC).
US Particle Accelerator School, 24 Jan - 4 Feb 2022
The Electron-Ion Collider (EIC) at Brookhaven National Laboratory is a high luminosity, ( ∼ 10³⁴ ... more The Electron-Ion Collider (EIC) at Brookhaven National Laboratory is a high luminosity, ( ∼ 10³⁴ \textrm{cm}⁻² \textrm{s}⁻¹ ) accelerator facility colliding polarized electron beam with different ion species ranging from lighter nuclei (proton, deuterium) to heavier nuclei (gold, uranium). Design of a stripline injection kicker for the Hadron Storage Ring (HSR) of EIC for beams with the rigidity of ∼ 81 T-m poses some technical challenges due to expected shorter bunch spacing and higher peak current of EIC. This paper focuses on the optimization of the EIC hadron ring injection kicker. Starting from the 2D cross-section design which includes the selection of electrodes shape, we describe the optimization of the kicker's cross-section. Then we discuss converting this 2D geometry to 3D by adding essential components for the stripline kicker and the 3D optimization techniques that we employed. Finally, we show simulation results for the optimized geometry including wakefields and T...
Since the invention of the electron cooling technique its application to cool hadron beams in col... more Since the invention of the electron cooling technique its application to cool hadron beams in colliders was considered for numerous accelerator physics projects worldwide. However, achieving the required high-brightness electron beams of required quality and cooling of ion beams in collisions was deemed to be challenging. An electron cooling of ion beams employing a high-energy approach with RF-accelerated electron bunches was recently successfully implemented at BNL. It was used to cool ion beams in both collider rings with ion beams in collision. Electron cooling in RHIC became fully operational during the 2020 physics run and led to substantial improvements in luminosity. This presentation will discuss implementation, optimization and challenges of electron cooling for colliding ion beams in RHIC.
The Low Energy RHIC Electron Cooling (LEReC) facility at BNL demonstrated, for the first time, co... more The Low Energy RHIC Electron Cooling (LEReC) facility at BNL demonstrated, for the first time, cooling of ion beams using a bunched electron beam from an SRF accelerating cavity and photoinjector. LEReC is planned to be operational to improve the luminosity of the Beam Energy Scan II physics program in RHIC in the following two years. In order to establish cooling of the RHIC Au ion beam using a 20 mA, 1.6 MeV bunched electron beam; absolute energy, angular and energy spread, trajectory and beam size were precisely matched. A suite of instrumentation was commissioned that includes a variety of current transformers, capacitive pick-up for gun high voltage ripple monitor, BPMs, transverse and longitudinal profile monitors, multi-slit and single-slit scanning emittance stations, time-of-flight and magnetic field related energy measurements, beam halo loss monitors and recombination monitors. The commissioning results and performance of these systems are described, including the latest ...
In order to achieve higher instantaneous and integrated luminosities, the average Au bunch intens... more In order to achieve higher instantaneous and integrated luminosities, the average Au bunch intensity in RHIC has been increased by 30% compared to the preceding Au run. This increase was accomplished by merging bunches in the RHIC injector AGS. Luminosity leveling for one of the two interaction points (IP) with collisions was realized by continuous control of the vertical beam separation. Parallel to RHIC physics operation, the electron beam commissioning of a novel cooling technique with potential application in eRHIC, Coherent electron Cooling as a proof of principle (CeCPoP), was carried out. In addition, a 56 MHz superconducting RF cavity was commissioned and made operational. In this paper we will focus on the RHIC performance during the 2016 Au-Au run.
The brand new non-magnetized bunched beam electron cooler (LEReC) [1] has been built to provide l... more 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.
The design effort for the electron-ion collider eRHIC has concentrated on electron-proton collisi... more 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.
The Electron-Ion Collider (EIC) is being envisioned as the next facility to be constructed by the... more 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.
Precedent to electron cooling commissioning and collisions of Gold at various energies at RHIC in... more Precedent to electron cooling commissioning and collisions of Gold at various energies at RHIC in 2018, the STAR experiment desired an exploration of the chiral magnetic effect in the quark gluon plasma (QGP) with an isobar run, utilizing Ruthenium and Zirconium. Colliding Zr-96 with Zr-96 and Ru-96 with Ru-96 create the same QGP but in a different magnetic field due to the different charges of the Zr (Z=40) and Ru (Z=44) ions. Since the charge difference is only 10%, the experimental program requires exacting store conditions for both ions. These systematic error concerns presented new challenges for the Collider, including frequent reconfiguration of the Collider for the different ion species, and maintaining level amounts of instantaneous and integrated luminosity between two species. Moreover, making beams of Zr-96 and Ru-96 is challenging since the natural abundances of these isotopes are low. Creating viable enriched source material for Zr-96 required assistance processing fro...
Cornell's Lab of Accelerator-based Sciences and Education (CLASSE) and the Collider Accelerat... more Cornell's Lab of Accelerator-based Sciences and Education (CLASSE) and the Collider Accelerator Department (BNL-CAD) are developing the first SRF multi-turn energy recovery linac with Non-Scaling Fixed Field Alternating Gradient (NS-FFAG) racetrack. The existing injector and superconducting linac at Cornell University are installed together with a single NS-FFAG arcs and straight section at the opposite side of the the linac to form an Electron Energy Recovery (ERL) system. Electron beam from the 6 MeV injector is injected into the 36 MeV superconducting linac, and accelerated by four successive passes: from 42 MeV up to 150 MeV using the same NS-FFAG structure made of permanent magnets. After the maximum energy of 150 MeV is reached, the electron beam is brought back to the linac with opposite Radio Frequency (RF) phase. Energy is recovered and reduced to the initial value of 6 MeV with 4 additional passes. There are many novelties: a single NS-FFAG structure, made of permanent...
The low energy RHIC Electron Cooler (LEReC) will be operating with 1.6-2.6 MeV electron beams hav... more The low energy RHIC Electron Cooler (LEReC) will be operating with 1.6-2.6 MeV electron beams having up to 140 kW power. It was determined that under the worst case scenario the missteered electron beam can damage the vacuum chamber and in-vacuum components within 40 us. Hence, the LEReC requires a dedicated fast machine protection system (MPS). The LEReC MPS has been designed and built and currently is under commissioning. In this paper we describe the most recent developments with the LEReC MPS.
As the last step of phase 1 of the beam energy scan (BESI), aimed at the search for the critical ... more As the last step of phase 1 of the beam energy scan (BESI), aimed at the search for the critical point in the QCD phase diagram, RHIC collided gold ions at a beam energy of 7.3 GeV/nucleon during the FY 2014 run. While this particular energy is close to the nominal RHIC injection energy of 9.8 GeV/nucleon, it is nevertheless challenging because it happens to be close to the AGS transition energy, which makes longitudinal beam dynamics during transfer from the AGS to RHIC difficult. We report on machine performance, obstacles and solutions during the FY 2014 low energy run.
Recent developments of the ERL-based design of future high-luminosity electron-hadron collider eR... more 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 ($$L \sim 10^{33} {\rm cm}^2 {\rm s}^{-1}$$) that employs reduced electron current and could possibly be based on classical electron cooling, and then with the Ultimate design ($$L \gt 10^{34} {\rm cm}^{-2} {\rm s}^{-1}$$) 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.
A multiple-pass, high-energy ERL experiment at the JLab CEBAF will be instrumental in providing n... more A multiple-pass, high-energy ERL experiment at the JLab CEBAF will be instrumental in providing necessary information and technology testing for a number of possible future applications and facilities such as Linac-Ring based colliders, which have been designed at BNL (eRHIC) and CERN (LHeC), and also drivers for high-energy FELs and 4th GLS. ER@CEBAF is aimed at investigating 6D optics and beam dynamics issues in ERLs, such as synchrotron radiation effects, emittance preservation, stability, beam losses, multiple-pass orbit control/correction, multiple-pass beam dynamics in the presence of cavity HOMs, BBU and other halo studies, handling of large (SR induced) momentum spread bunches, and development of multiple-beam diagnostics instrumentation. Figure 1: 12 GeV CEBAF recirculating linac. Location of chicane and dump line for ER@CEBAF. Since it was launched 2+ years ago, the project has progressed in defining the necessary modifications to CEBAF (Fig. 1, Tab. 1, 2), including a 4-d...
A collaboration between Cornell University and Brookhaven National Laboratory has designed and is... more A collaboration between Cornell University and Brookhaven National Laboratory has designed and is constructing CBETA, the Cornell-BNL ERL Test Accelerator on the Cornell campus. The ERL technology that has been prototyped at Cornell for many years is being used for this new accelerator, including a DC electron source and an SRF injector Linac with world-record current and normalized brightness in a bunch train, a high-current linac cryomodule optimized for ERLs, a high-power beam stop, and several diagnostics tools for high-current and high-brightness beams. BNL has designed multi-turn ERLs for several purpose, dominantly for the electron beam of eRHIC, its Electron Ion Collider (EIC) project and for the associated fast electron cooling system. Also in JLEIC, the EIC designed at JLAB, an ERL is envisioned to be used for electron cooling. The number of transport lines in an ERL is minimized by using return arcs that are comprised of a Fixed Field Alternating-gradient (FFA) design. Th...
Low Energy RHIC Electron cooler (LEReC) project is presently under commissioning at Brookhaven Na... more Low Energy RHIC Electron cooler (LEReC) project is presently under commissioning at Brookhaven National Laboratory (BNL). LEReC requires high average current up to 85mA and high-quality electron beam [1]. A 400 kV DC gun equipped with a photocathode and laser system has been chosen to provide a source of high-quality electron beams. We started testing the DC gun during the RHIC run 2017. First electron beam from LEReC DC gun was delivered in April 2017 [2]. During the DC gun test critical elements of LEReC such as laser beam system, cathode exchange system, cathode QE lifetime, DC gun stability, beam instrumentation, the high-power beam dump system, machine protection system and controls have been tested. Average current of 10 mA for few hours of operation was reached in August 2017. In this paper we present experimental results and experience learned during the LEReC DC gun beam testing. PURPOSE OF LEReC GUN TEST The gun beam test (see Fig. 1) is the first stage of LEReC commission...
The first part of RHIC Run 15 consisted of ten weeks of polarized proton on proton collisions at ... more The first part of RHIC Run 15 consisted of ten weeks of polarized proton on proton collisions at a beam energy of 100 GeV at two interaction points. In this paper we discuss several of the upgrades to the collider complex that allowed for improved performance. The largest effort consisted in commissioning of the electron lenses, one in each ring, which are designed to compensate one of the two beam-beam interactions experienced by the proton bunches. The e-lenses raise the per bunch intensity at which luminosity becomes beam-beam limited. A new lattice was designed to create the phase advances necessary for a beam-beam compensation with the e-lens, which also has an improved off-momentum dynamic aperture relative to previous runs. In order to take advantage of the new, higher intensity limit without suffering intensity driven emittance deterioration, other features were commissioned including a continuous transverse bunch-by-bunch damper in RHIC and a double harmonic RF cature schem...