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The Electron-Ion Collider (EIC) at Brookhaven National Laboratory will provide spin-polarized collisions of electron and protons or light ion beams. In order to maximize the electron polarization and require less frequent beam re-injections to restore the polarization level, the stochastic depolarizing effects of synchrotron radiation must be minimized via spin matching. In this study, Bmad was used to perform first order spin matching in the Electron Storage Ring (ESR) of the EIC. Spin matches were obtained for the rotator systems and for a vertical chicane, inserted as a vertical emittance creator. Monte Carlo spin tracking with radiation was then performed to analyze the effects of the spin matching on the polarization., Proceedings of the 13th International Particle Accelerator Conference, IPAC2022, Bangkok, Thailand

Electron cooling of ion beams employing rf-accelerated electron bunches was successfully used for the RHIC physics program in 2020 and 2021 and was essential in achieving the required luminosity goals. This presentation will summarize experience and challenges with electron cooling of colliding ion beams in RHIC. We also outline ongoing studies using rf-based electron cooler LEReC., Proceedings of the 5th North American Particle Accelerator Conference, NAPAC2022, Albuquerque, NM, USA

The Electron Ion Collider (EIC) requires a cooling of protons at the top energy. The Ring Electron Cooler (REC) is a suitable option for such a cooling. In this paper we consider an effect of a proton-electron space charge (SC) focusing on the quality of the electron beam in the REC. We show that, with properly adjusted parameters of the Ring Electron Cooler, the SC focusing in the REC cooling section does not significantly affect the cooler performance., Proceedings of the 5th North American Particle Accelerator Conference, NAPAC2022, Albuquerque, NM, USA

The Electron-Ion Collider (EIC) presently under construction at Brookhaven National Laboratory will collide polarized high energy electron beams with hadron beams with design luminosities up to 1×10³⁴cm⁻²s⁻¹ in the center mass energy range of 20-140 GeV. We simulated the planned electron-proton collision of flat beams with Particle-In-Cell (PIC) based Poisson solver in strong-strong beam-beam simulation. We observed a much larger proton emittance growth rate than that from weak-strong simulation. To understand the numerical noises further, we calculate the beam size growth rate of macro-particles as function of their initial longitudinal and transverse actions. This method is applied to both strong-strong and weak-strong simulations. The purpose of this study is to identify which group of macro-particles contributes most of the artificial emittance growth in strong-strong beam-beam simulation., Proceedings of the 13th International Particle Accelerator Conference, IPAC2022, Bangkok, Thailand

The Electron Ion Collider (EIC) is under design at Brookhaven National Laboratory. The EIC aims at providing high luminosity and high polarization collisions for a large range of beam energies. Dynamic aperture (DA) of the EIC Electron Storage Ring (ESR) must be sufficiently large in both transverse and momentum dimensions. The latter is a challenge due to low-beta optics in up to two interaction regions (IR). We have developed an advanced technique for efficient non-linear chromaticity compensation compatible with the different ESR lattice configurations at different energies. The solution for the most challenging lattice with two IRs at 18 GeV is presented. The lattice is then evaluated with magnet errors, where the error tolerances are determined for reaching the desired DA., Proceedings of the 13th International Particle Accelerator Conference, IPAC2022, Bangkok, Thailand

The Electron Ion Collider aims to produce luminosities of 10³⁴ cm⁻²s⁻¹ . The machine will operate over a broad range of collision energies with highly polarized beams. The coexistence of highly radiative electrons and nonradiative ions produce a host of unique effects. Strong hadron cooling will be employed for the final factor of 3 luminosity boost., Proceedings of the 13th International Particle Accelerator Conference, IPAC2022, Bangkok, Thailand

The Electron-Ion Collider (EIC) is being designed for construction at Brookhaven National Laboratory. Activities have been focused on beam-beam simulations, polarization studies, and beam dynamics, as well as on maturing the layout and lattice design of the constituent accelerators and the interaction region. The latest design advances will be presented., Proceedings of the 13th International Particle Accelerator Conference, IPAC2022, Bangkok, Thailand

The Electron-Ion Collider (EIC) presently under construction at Brookhaven National Laboratory will collide polarized high energy electron beams with hadron beams, reaching luminosities up to 1×10³⁴cm⁻²s⁻¹ in center mass energy range of 20-140 GeV. We studied the planned electron-proton collisions using a Particle-In-Cell (PIC) based Poisson solver in strong-strong beam-beam simulation. We observed a much larger proton emittance growth rate than in weak-strong simulation. To understand the numerical noise and its impact on strong-strong simulation results, we carried out extensive studies to identify all possible causes for artificial emittance growth and quantify their contributions. In this article, we summarize our study activities and findings. This work will help us better understand the simulated emittance growth and the limits of the PIC based strong-strong beam-beam simulation., Proceedings of the 13th International Particle Accelerator Conference, IPAC2022, Bangkok, Thailand

The Electron-Ion Collider (EIC) will collide electrons with hadrons at center-of-mass energies up to 140 GeV (in the case of electron-proton collisions). A 3.8-kilometer electron storage ring is being designed, which will store electrons with a range of energies up to 18 GeV for collisions at one or two interaction points. At energies up to 10 GeV the arcs will be tuned to provide 60 degree phase advance per cell in both planes, whereas at top energy of 18 GeV a 90 degree phase advance per cell will be used, which largely compensates for the horizontal emittance increase with energy. The optics must be matched at three separate energies, and the different phase-advance requirements in both the arc cells and the straight sections make this challenging. Moreover, the spin rotators must fulfill requirements for polarization and spin matching at widely different energies while satisfying technical constraints. In this paper these challenges and proposed solutions are presented and discussed., Proceedings of the 13th International Particle Accelerator Conference, IPAC2022, Bangkok, Thailand

The design of the electron-ion collider EIC to be constructed at Brookhaven National Laboratory has been continuously evolving towards a realistic and robust design that meets all the requirements set forth by the nuclear physics community in the White Paper. Over the past year activities have been focused on maturing the design, and on developing alternatives to mitigate risk. These include improvements of the interaction region design as well as modifications of the hadron ring vacuum system to accommodate the high average and peak beam currents. Beam dynamics studies have been performed to determine and optimize the dynamic aperture in the two collider rings and the beam-beam performance. We will present the EIC design with a focus on recent developments., Proceedings of the 12th International Particle Accelerator Conference, IPAC2021, Campinas, SP, Brazil

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., Proceedings of the 12th International Particle Accelerator Conference, IPAC2021, Campinas, SP, Brazil

In order to minimize the systematic errors for the Relativistic Heavy Ion Collider (RHIC) spin physics experiments, flipping the spin of each bunch of protons during the stores is needed. Experiments done with single RF magnet at energies less than 2 GeV have demonstrated a spin-flip efficiency over 99%. At high energy colliders with Siberian snakes, a single magnet spin flipper does not work because of the large spin tune spread and the generation of multiple, overlapping resonances. Over past decade, RHIC spin flipper design has evolved and a sophisticated spin flipper, constructed of nine-dipole magnets, was developed to flip the spin in RHIC. A special optics choice was also used to make the spin tune spread very small. In recent experiment, 97% spin-flip efficiency was measured at both 24 and 255 GeV for the first time. The results show that efficient spin flipping can be achieved at high energies., Proceedings of the 12th International Particle Accelerator Conference, IPAC2021, Campinas, SP, Brazil

An electron cooling of ion beams employing a high-energy approach with rf-accelerated electron bunches was recently implemented at BNL using LEReC accelerator. Following successful cooling commissioning in 2019, it was used to cool ion beams in both collider rings with ion beams in collision. Electron cooler LEReC successfully operated for the RHIC physics program in 2020 and 2021 and was essential in achieving the required luminosity goals. Apart from its use in RHIC operations, LEReC is being used to study various aspects of electron cooling physics using short electron bunches. This presentation will summarize experience with electron cooling of colliding ion beams in RHIC, as well as ongoing studies., Proceedings of the 13th International Workshop on Beam Cooling and Related Topics, COOL2021, Novosibirsk, Russia

Spin flipper experiments during RHIC Run 17 have demonstrated the 97% effectiveness of polarization sign reversal during stores. Zgoubi numerical simulations were setup to reproduce the experimental conditions. A very good agreement between the experimental measurements and simulation results was achieved at 23.8GeV, thus the simulations are being used to help optimize the various Spin Flipper parameters. The ultimate goal for these simulations is to serve as guidance towards a perfect flip at high energies to allow a routine Spin Flipper use during physics runs., Proceedings of the 10th Int. Particle Accelerator Conf., IPAC2019, Melbourne, Australia

The brand-new state of the art electron accelerator, LEReC, was built and commissioned at BNL. 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. Electron beam quality suitable for cooling in the Relativistic Heavy Ion Collider (RHIC) was achieved [1], which lead to the first demonstration of bunched beam electron cooling of hadron beams [2]. This presentation will discuss commissioning results, achieved beam parameters and performance of the LEReC systems., Proceedings of the North American Particle Accelerator Conference, NAPAC2019, Lansing, MI, USA

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., Proceedings of the 10th Int. Particle Accelerator Conf., IPAC2019, Melbourne, Australia

With the completion of the National Academies of Sciences Assessment of a US Electron-Ion Collider, the prospects for construction of such a facility have taken a step forward. This paper provides an overview of the two site-specific EIC designs: JLEIC (Jefferson Lab) and eRHIC (BNL) as well as brief overview of ongoing EIC R, Proceedings of the North American Particle Accelerator Conference, NAPAC2019, Lansing, MI, USA

The future electron-ion collider (EIC) aims at an electron-proton luminosity of 10³³ to 10³⁴ cm⁻² sec⁻¹ and a center-of-mass energy range from 20 to 140 GeV. The eRHIC design has been continuously evolving over a couple of years and has reached a considerable level of maturity. The concept is generally conservative with very few risk items which are mitigated in various ways., Proceedings of the North American Particle Accelerator Conference, NAPAC2019, Lansing, MI, USA

The Low Energy RHIC electron Cooler (LEReC) was recently constructed and commissioned at BNL. The LEReC is the first electron cooler based on the RF acceleration of electron bunches (previous electron coolers all used DC beams). Bunched electron beams are necessary for cooling hadron beams at high energies. The challenges of such an approach include generation of electron beams suitable for cooling, delivery of electron beams of the required quality to the cooling sections without degradation of beam emittances and energy spread, achieving required small angles between electrons and ions in the cooling sections, precise energy matching between the two beams, high-current operation of the electron accelerator, as well as several physics effects related to bunched beam cooling. Following successful commissioning of the electron accelerator in 2018, the focus of the LEReC project in 2019 was on establishing electron-ion interactions and demonstration of cooling process using electron energy of 1.6MeV (ion energy of 3.85GeV/n), which is the lowest energy of interest. Here we report on the first demonstration of Au ion cooling in RHIC using this new approach., Proceedings of the North American Particle Accelerator Conference, NAPAC2019, Lansing, MI, USA

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 design efforts of high-power electron beam transverse profile monitoring using a fast wire scanner, residual gas beam induced fluorescence monitor, and Boron Nitride NanoTube (BNNT) screen monitor, Proceedings of the 8th International Beam Instrumentation Conference, IBIC2019, Malmö, Sweden

The first ever electron cooling based on the RF acceleration of electron bunches was experimentally demonstrated on April 5, 2019 at the Low Energy RHIC Electron Cooler (LEReC) at BNL. The critical step in obtaining successful cooling of the Au ion bunches in the RHIC cooling sections was the accurate matching of average longitudinal velocities of electron and ion beams corresponding to a relative error of less than 5·10⁻⁴ in the e-beam momentum. Since the electron beam kinetic energy is just 1.6 MeV, measuring the absolute e-beam energy with sufficient accuracy and eventually achieving the electron-ion velocity matching was a nontrivial task. In this paper we describe our experience with measuring and setting the e-beam energy at LEReC., Proceedings of the North American Particle Accelerator Conference, NAPAC2019, Lansing, MI, USA

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., Proceedings of the 10th Int. Particle Accelerator Conf., IPAC2019, Melbourne, Australia

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., Proceedings of the 7\textsuperscript{th} Int. Beam Instrumentation Conf., IBIC2018, Shanghai, China

Low Energy RHIC electron cooling (LEReC) [1] is the first bunched electron cooler, designed to cool low energy ion beams at RHIC. The beam quality, including the transverse beam emittance, is critical for the success of cooling. The transverse electron beam emittance was characterized with a multi-slit and moving-slit device at various locations in the beamline. The beam emittance measurement and analysis are presented in this report., Proceedings of the 7\textsuperscript{th} Int. Beam Instrumentation Conf., IBIC2018, Shanghai, China

The electron-ion collider eRHIC aims at a luminosity around 10³⁴cm⁻²sec⁻¹, using strong cooling of the hadron beam. Since the required cooling techniques are not yet readily available, an initial version with a peak luminosity of 3*10³³cm⁻²sec⁻¹ is being developed that can later be outfitted with strong hadron cooling. We will report on the current design status and the envisioned path towards 10³⁴cm⁻²sec⁻¹ luminosity., Proceedings of the 9th Int. Particle Accelerator Conf., IPAC2018, Vancouver, BC, Canada

Non-magnetized bunched electron cooling of ion beams during low energy RHIC operation requires electron beam energy in the range of 1.6-2.6 MeV, with an average current up to 45 mA, very small energy spread, and low emittance. A 400 kV DC gun equipped with a photocathode and laser system will provide a source of high-quality electron beams. During 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 has been tested under near- operational conditions [1]. We present the status, experimental results and experience learned during the LEReC DC gun beam testing., Proceedings of the 59th ICFA Advanced Beam Dynamics Workshop on Energy Recovery Linacs, ERL17, Geneva, Switzerland

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. 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 *. 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., Proceedings of the 9th Int. Particle Accelerator Conf., IPAC2018, Vancouver, BC, Canada

Spin flipper experiments during RHIC Run 17 were performed to study its effectiveness as a method for polarization sign reversal during stores. Numerical simulations are reported here, which were performed in accompaniment of these, and are being pursued with the aim of accurately reproducing the experimental conditions and providing thorough insight in the role of various key parameters participating in the dynamics of the spin flip, such as the sweep rate of the AC dipole, chromatic orbit control at RHIC snakes, RF parameters, possible effects of non-linear spin resonances, mirror resonance, tolerance on flipper magnet parameters, etc. The ultimate goal is for these simulations to serve as a guidance toward perfect flip to allow routine use during physics Runs., Proceedings of the 9th Int. Particle Accelerator Conf., IPAC2018, Vancouver, BC, Canada

Low Energy RHIC electron Cooling (LEReC) is planned during a 7.7 - 20 GeV/n run with Au+79 starting in 2019 (200 GeV/n center-of-mass typical), to explore the existence and location of the QCD critical point. An electron accelerator for LEReC is being constructed to provide a beam to cool both the blue & yellow RHIC ion beams by co-propagating a 10 - 50 mA electron beam of 1.6 - 2.7 MeV. For effective cooling of the ion beam, the electron and ion beam energies must be matched with 10⁻⁴ accuracy. As the energy of the RHIC ion beam can be known to, Proceedings of the 6th Int. Beam Instrumentation Conf., IBIC2017, Grand Rapids, MI, USA

Present requirements to the photocathode DC gun of the low energy RHIC electron cooling (LEReC) project is to produce 100 ps long bunch of electrons with 130 pC charge. The laser pulse of required length will be produced with the stacking of multiple few picosecond long sub-pulses. Depending on the choice of the laser sub-pulse length and on the relative delay between these sub-pulses one can obtain laser pulse with various longitudinal intensity modulations. The longitudinal modulation of laser intensity creates longitudinal modulation of electron bunch charge. Such modulation is known to cause the growth of e-beam uncorrelated energy spread in photoinjectors - the effect we would like to avoid. In this paper we estimate growth of e-beam energy spread due to its initial density modulation and set requirements to the maximum allowable depth of longitudinal modulation of photocathode laser intensity., Proceedings of the 8th Int. Particle Accelerator Conf., IPAC2017, Copenhagen, Denmark

The RHIC Low Energy Cooler will be based on a 400 keV DC electron gun with a photo-cathode and a 2.2 MeV SRF booster cavity. Electron that leave the cathode at the wrong time may be decelerated and turned around in the booster and return to the cathode with energies up to 1 MeV. On the way back these electron will encounter the defocussing EM fields up to nine following electron bunches. Such electrons may be created for various reasons: Cosmic rays, stray laser light including a catastrophic failure of the laser timing system or as secondaries of returning electrons. We present tracking results from the GPT program* and discuss the consequences for the machine protection system., Proceedings of the 8th Int. Particle Accelerator Conf., IPAC2017, Copenhagen, Denmark

A Low-energy RHIC Electron Cooler (LEReC) system is presently under construction at Brookhaven National Laboratory. This device shall enable gold ion collisions at energies below the design injection energy with sufficient luminosity. Electron beam with energies between 1.6, 2.0 and 2.6 MeV are necessary. This machine will be the first to attempt electron cooling using bunched electron beam, using a 703 MHz SRF cavity for acceleration. Special consideration must be given to the effect of space charge forces on the transverse and longitudinal beam quality. We will present the current layout of the cooler and beam parameter simulations using the computer codes PARMELA., Proceedings of the North American Particle Accelerator Conf., NAPAC2016, Chicago, IL, USA

The goal of future operation of the low energy RHIC Electron Cooling (LEReC) accelerator is to cool the RHIC ion beams. To provide successful cooling, the velocities of the RHIC ion beam and the LEReC electron beam must be matched with 10⁻⁴ accuracy. While the energy of ions will be known with the required accuracy, the e-beam energy can have an initial offset as large as 5%. The final setting of the e-beam energy will be performed by observing either the Schottky spectrum of debunched ions co-traveling with the e-beam or the recombination signal. Yet, to start observing such signals one has to set the absolute energy of the electron beam with an accuracy better than 10⁻², preferably better than 5·10⁻³. In this paper we discuss how such accuracy can be reached by utilizing the LEReC 180 degree bend as a spectrometer., Proceedings of the North American Particle Accelerator Conf., NAPAC2016, Chicago, IL, USA

The cooling section (CS) of the low energy RHIC electron cooler (LEReC) consists of two 20 m long parts each containing six solenoids with trajectory correctors placed inside the solenoids and the BPMs located downstream of each solenoid. The solenoids are used to minimize the scalloping of the electron beam envelope. To obtain the cooling it is required to keep the overall RMS electron angles in the cooling section below 100 urad. Possible mechanical misalignment, such as shift and inclination of the CS solenoids can cause an unacceptable misalignment of the e-beam trajectory with respect to the ideal trajectory set by ions. Therefore, it is critical to perform a beam based alignment of the CS solenoids. In this paper we suggest a procedure for such an alignment., Proceedings of the 8th Int. Particle Accelerator Conf., IPAC2017, Copenhagen, Denmark

To improve the luminosity of beam energy scan of low energy Au-Au collision, a electron machine is under con- struction to cool ion beams in both RHIC rings with pulsed electron beam. Over the course of the project, a multi- slit device is needed to characterize the transverse beam emittance of three energies, 0.4, 1.6 and 2.6 MeV. This re- port shows the optimization and compromise of the design, which include the slit width, slit spacing, and drift space from the multi-slit to the downstream profile monitor., Proceedings of the North American Particle Accelerator Conf., NAPAC2016, Chicago, IL, USA

A Low Energy RHIC electron Cooler (LEReC) is presently under construction at BNL to improve the luminosity of the Relativistic Heavy Ion Collider (RHIC). The required electron beam will be provided by a photoemission electron gun and accelerated by a RF linear accelerator. As a result, LEReC will be first bunched beam electron cooler. In addition, this will be the first electron cooler to cool beams under collisions. The achievement of very tight electron beam parameters required for cooling is very challenging and is being addressed by a proper beam transport and engineering design. In this paper, we describe accelerator physics requirements, design considerations and parameters, as well as associated challenges of such electron cooling approach., Proceedings of the North American Particle Accelerator Conf., NAPAC2016, Chicago, IL, USA

Non-magnetized bunched electron cooling of low-energy RHIC requires electron beam energy in range of 1.6-2.6 MeV, with average current up to 45 mA, very small energy spread, and low emittance [1]. A 400 kV DC gun equipped with photocathode and laser delivery system will serve as a source of high-quality electron beam. Acceleration will be achieved by an SRF 704 MHz booster cavity and other RF components that are scheduled to be operational in early 2018. The DC gun testing in its installed location in RHIC will start in early 2017. During this stage we plan to test the critical equipment in close to operation conditions: laser beam delivery system, cathode QE lifetime, DC gun, beam instrumentation, high power beam dump system, and controls. In this paper, we describe the gun test set up, major components, and parameters to be achieved and measured during the gun beam test., Proceedings of the North American Particle Accelerator Conf., NAPAC2016, Chicago, IL, USA

The Low-energy RHIC electron Cooler (LEReC) system has been approved to be build at the Brookhaven National Laboratory. The electron cooling system will be able to deliver an electron beam of adequate quality in a wide range of electron beam energies (1.6-5 MeV). While existing electron coolers use a DC electron beam this will be the first application of using a bunched electron beam provided by an ERL, paving the way for future electron coolers at higher energies., Proceedings of the 56th ICFA Advanced Beam Dynamics Workshop on Energy Recovery Linacs, ERL2015, Stony Brook, NY, USA

The spin physics program in Relativistic Heavy Ion Collider (RHIC) requires fast polarimeter to monitor the polarization evolution on the ramp and during stores. Over past decade, the polarimeter has evolved greatly to improve its performance. These include dual chamber design, monitoring camera, Si detector selection (and orientation), target quality control, and target frame modification. The preamp boards have been modified to deal with the high rate problem, too. The ultra thin carbon target lifetime is a concern. Simulations have been carried out on the target interaction with beam. Modification has also been done on the frame design. Extra caution has been put on RF shielding to deal with the pickup noises from the nearby stochastic cooling kickers. This paper summarizes the recent operation performance of this delicate device., Proceedings of the 6th Int. Particle Accelerator Conf., IPAC2015, Richmond, VA, USA

We present our studies on various aspects of the beam dynamics in ’racetrack’ design of the first stage electron-ion collider at RHIC (eRHIC), including transverse beam break up instabilities, electron beam emittance growth and energy loss due to synchrotron radiation, electron beam losses due to Touschek effects and residue gas scattering, beam-beam effects at the interaction region and emittance growth of ion beam due to electron bunch to bunch noises. For all effects considered above, no showstopper has been found., Proceedings of the 1st International Particle Accelerator Conference, IPAC2010, Kyoto, Japan

Superconducting RF (SRF) electron guns deliver higher brightness beams than DC guns because the field gradient at the cathode is higher. SRF guns with metal cathodes have been successfully tested. For the production of polarized electrons a Gallium-Arsenide (GaAs) cathode must be used, and an experiment to test this type of cathode is under way at BNL. Since the cathode will be normal conducting, the primary concern is cathode-driven heat load. We present measurements of the electric resistance of GaAs at cryogenic temperatures, a prediction of the heat load, and verification by measuring the quality factor of the gun with and without the cathode., Proceedings of the 1st International Particle Accelerator Conference, IPAC2010, Kyoto, Japan