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In this talk we are presenting the most recent results from the commissioning of unique Coherent Electron Cooling system, which is using an FEL amplifier to facilitate cooling of hadrons by an electron beam. We present achieved results as well as changes we encountered in the process., Proceedings of the 38th Int. Free Electron Laser Conf., FEL2017, Santa Fe, NM, USA

The coherent electron cooling proof-of-principle experiment is aimed to demonstrate new technique suitable for cooling of the high energy protons and is essential for a future electron-hadron collider. In this paper we present the current status of the equipment, achieved beam parameters, and progress of the experiment. Future plans are also discussed., Proceedings of the 11th Workshop on Beam Cooling and Related Topics, COOL2017, Bonn, Germany

In 2016 run of Coherent Electron Cooling, we have successfully tested the performance of a number of K2CsSb cathodes. These cathodes with QE of 6%-10% were fabricated in Instrumentation Division, a few miles away, transported to RHIC tunnel under UHV conditions, attached to the CeC gun, kept in storage, and inserted in the gun as needed. A maximum bunch charge of 4.6 nC was generated in the gun when the QE was 1.8 %. With careful conditioning at increasing accelerating fields, it was possible to maintain the QE of several cathodes for more than a week. For the cathodes that experienced degradation, the primary cause was multipacting when the power into the gun was increased. In the initial runs, the entire 20 mm substrate face was coated with the cathode material causing cathode induced multipacting. For subsequent measurements, the substrate was masked to coat only the central 9 mm of the substrate. By optimizing the procedure for boosting the power to the gun and covering all viewports to minimize dark current, we were able to minimize QE degradation. In this paper we discuss the cathode preparation, transfer to the gun and operational experience with the cathodes in 112 MHz gun., Proceedings of the North American Particle Accelerator Conf., NAPAC2016, Chicago, IL, USA

Coherent electron cooling is new cooling technique to be tested at BNL. Presently we are in the commissioning stage of the accelerator system. In this paper we present status of various systems and achieved beam parameters as well as operational experience. Near term future plans are also discussed., Proceedings of the North American Particle Accelerator Conf., NAPAC2016, Chicago, IL, USA

The Coherent Electron Cooling Proof-of-Principle (CeC PoP) experiment employs a high-gradient CW photo-injector based on the superconducting RF cavity. Such guns operating at high accelerating gradients promise to revolutionize many sciences and applications. They can establish the basis for super-bright monochromatic X-ray and gamma ray sources, high luminosity hadron colliders, nuclear waste transmutation or a new generation of microchip production. In this paper we report on our operation of a superconducting RF electron gun with a high accelerating gradient at the CsK2Sb photo-cathode (i.e. ~ 20 MV/m) generating a record-high bunch charge (above 4 nC). We give short description of the system and then detail our experimental results., Proceedings of the North American Particle Accelerator Conf., NAPAC2016, Chicago, IL, USA

BNL R&D ERL beam commissioning started in June 2014 [*]. The key components of R&D ERL are the highly damped 5-cell 704 MHz superconducting RF cavity and the high-current superconducting RF gun. The gun is equipped with a multi-alkaline photocathode insertion system. The first photocurrent from ERL SRF gun has been observed in November 2014. In June 2015 a high charge 0.5nC and 20 uA average current were demonstrated. In July 2015 gun to dump beam test started. The beam was successfully transported from the SRF gun through the injection system, then through the linac to the beam dump. All ERL components have been installed. In October 2015, SRF gun cavity has been found contaminated during severe cathode stalk RF conditioning. This cavity has been sent for repair and modification for later use in low-energy RHIC electron cooler (LEReC)[**]. LEReC scheduled to start commissioning in early of 2018. We present our results of BNL ERL beam commissioning, the measured beam properties, the operational status, and future prospects., Proceedings of the 28th Linear Accelerator Conf., LINAC2016, East Lansing, MI, USA

The ring-ring electron-ion collider eRHIC aims at an electron-ion luminosity in the range from 10³² to 10³³cm⁻²sec⁻¹ over a center-of-mass energy range from 20 to 140GeV. To minimize the technical risk the design is based on existing technologies and beam parameters that have already been achieved routinely in hadron-hadron collisions at RHIC, and in electron-positron collisions elsewhere. This design has evolved considerably over the last two years, and a high level of maturity has been achieved. We will present the latest design status and give an overview of studies towards evaluating the feasibility., Proceedings of the 8th Int. Particle Accelerator Conf., IPAC2017, Copenhagen, Denmark

Recent developments of the ERL-based design of future high luminosity electron-hadron collider eRHIC focused on balancing technological risks present in the design versus the design cost. As a result a lower risk design has been adopted at moderate cost increase. The modifications include a change of the main linac RF frequency, reduced number of SRF cavity types and modified electron spin transport using a spin rotator. A luminosity-staged approach is being explored with a Nominal design (L ~ 10³³ cm⁻² s⁻¹) that employs reduced electron current and could possibly be based on classical electron cooling, and then with the Ultimate design (L > 10³⁴ cm⁻² s⁻¹) that uses higher electron current and an innovative cooling technique (CeC). The paper describes the recent design modifications, and presents the full status of the eRHIC ERL-based design., Proceedings of the 7th Int. Particle Accelerator Conf., IPAC2016, Busan, Korea

We have started the first tests of the equipment for the coherent electron cooling proof-of-principle experiment. After tests of the 500 MHz normal conducting cavities we proceeded with the low power beam tests of a CW SRF gun. The results of the tests with record beam parameters are presented., Proceedings of the 37th International Free Electron Laser Conference, FEL2015, Daejeon, Republic of Korea

We developed modeling capabilities, within the Vorpal particle-in-cell code, for three-dimensional (3D) simulations of surface effects and electron emission from semiconductor photocathodes. They include calculation of emission probabilities using general, piece-wise continuous, space-time dependent surface potentials, effective mass and band bending field effects. We applied these models, in combination with previously implemented capabilities for modeling charge generation and transport in diamond, to investigate the emission dependence on applied electric field in the range from approximately 2 to 17 MV/m along the [100] direction. The simulation results were compared to experimental data when using different emission models, band bending effects, and surface-dependent electron affinity. Simulations using surface patches with different levels of hydrogenation lead to the closest agreement with the experimental data., Proceedings of the 6th Int. Particle Accelerator Conf., IPAC2015, Richmond, VA, USA

A 112 MHz superconducting RF photoemission gun was designed, fabricated and installed in RHIC for the Coherent electron Cooling Proof-of-Principle (CeC PoP) experiment at BNL. The gun was commissioned first without beam. This was followed by generating the first photoemission beam from a multi-alkali cathode. The paper presents the commissioning results., Proceedings of the 17th International Conference on RF Superconductivity, SRF2015, Whistler, BC, Canada

A prototype of a high average current polarized electron funneling gun as an eRHIC injector has been built at BNL. The gun was assembled and tested at Stangenes Incorporated. Two beams were generated from GaAs photocathodes and combined by a switched combiner field. We observed the combined beams on a YAG crystal and measured the photocurrent by a Faraday cup. The gun has been shipped to Stony Brook University and is being tested there. In this paper we will describe the major components of the gun and recent beam test results. High voltage conditioning is discussed as well., Proceedings of the 6th Int. Particle Accelerator Conf., IPAC2015, Richmond, VA, USA

An ampere class 20 MeV superconducting Energy Recovery Linac (ERL) is presently under commissioning at Brookhaven National Laboratory (BNL) for testing of concepts relevant for high-energy coherent electron cooling and electron-ion colliders. The injector subsystems tests and installation were finished in fall 2013. The injector includes: SRF photoelectron gun with 1 MW amplifier, 10W green drive-laser system, multi-alkaline cathode deposition system, cathode transport system, beam instrumentation and control. * The first photo current from ERL SRF gun has been observed in fall 2014 after second attempt. Completion of the ERL returning loop components installation is scheduled for April 2015 following full power ERL commissioning. After ERL commissioning in BLDG912 the ERL will be relocated to RHIC IP2 to be used as low energy RHIC electron cooler., Proceedings of the 56th ICFA Advanced Beam Dynamics Workshop on Energy Recovery Linacs, ERL2015, Stony Brook, NY, USA

The talk shall cover two SRF photoemission electron guns under commissioning at BNL: a 704 MHz elliptical ERL gun and a 112 MHz quarter-wave gun for coherent electron cooling experiment. In particular, the speaker shall report on generating first photoemission beam current from the 704 MHz SRF gun, multipacting issues in the SRF guns, photocathode behavior as well as other commissioning experiences and results., Proceedings of the 17th International Conference on RF Superconductivity, SRF2015, Whistler, BC, Canada

Two electron beams from two activated bulk GaAs photocathodes were successfully combined during the recent beam test of the High Current High Polarization Electron gun for eRHIC. The beam test took place at Stangenes Industries in Palo Alto, CA, where the cathodes were placed in radially opposite locations inside the high voltage shroud. No significant cross talking between the cathodes were found for the pertinent vacuum and low average current operation, which is very promising towards combining multiple beams for higher average current. This paper describes the cathode preparation, transport and cathode performance in the gun for the combining test, including the QE and lifetimes of the photocathodes at various steps of the experiment., Proceedings of the 6th Int. Particle Accelerator Conf., IPAC2015, Richmond, VA, USA

The 704 MHz superconducting RF gun successfully generated the first photoemission beam on Nov. 17 2014. This paper will report the latest results of SRF beam commissioning, including the SRF cavity performance, cathode QE measurements, and beam parameter measurements. The beam commissioning setup is described in the paper as well., Proceedings of the 6th Int. Particle Accelerator Conf., IPAC2015, Richmond, VA, USA

The Coherent electron Cooling Proof-of-Principle (CeC PoP) experiment at BNL includes a short electron linac. During Phase I a 112 MHz superconducting RF photoemission gun and two 500 MHz normal conducting bunching cavities were installed and commissioned. The paper describes the Phase I linac layout and presents commissioning results for the cavities and associated RF, cryogenic and other sub-systems., Proceedings of the 6th Int. Particle Accelerator Conf., IPAC2015, Richmond, VA, USA

The BNL SRF gun cavity was operated well at CW mode up to 2 MV. However, the performance suffered due to multipacting in the quarter-wavelength choke-joint. A new multipacting-free cathode stalk was designed and will be conditioned. This paper will describes RF and thermal design of new cathode stalk and conditioning results., Proceedings of the 6th Int. Particle Accelerator Conf., IPAC2015, Richmond, VA, USA

Stangenes Industries is working closely with Brookhaven National Lab in the United States to develop the eRHIC future ion collider. The collider requires a polarized electron source with high average current, short bunch length and small emittance. An array of photocathodes with their beams funneled into a common trajectory is utilized to achieve the required beam current and cathode lifetime. Stangenes Industries is charged with delivering the prototype injector for preliminary beam studies that will lead to full implementation by 2020. This study focuses on the development of the of beam transport system extending from cathode to beam dump. A majority of the complexity involves the so called "combiner magnet" that acts as a high frequency-rotating dipole to bend each beam into the final common trajectory. Preliminary experiments into the feasibility of such a system are analyzed., Proceedings of the 5th Int. Particle Accelerator Conf., IPAC2014, Dresden, Germany