BNL, Upton, Long Island, New York, USA
Stony Brook University, Stony Brook, USA
RHIC operations with heavy ion beams at energies below 10 GeV/nucleon are motivated by a search for the QCD Critical Point. An electron cooler is proposed as a means to increase RHIC luminosity for collider operations at these low energies. The electron cooling system should be able to deliver an electron beam of adequate quality over a wide range of electron beam energies (0.9-5 MeV). It also should provide optimum 3-D cooling for both hadron beams in the collider. A method based on bunched electron beam, which is also a natural approach for high-energy electron cooling, is being developed. In this paper, we describe the requirements for this system, its design aspects, as well as the associated challenges.
BNL, Upton, Long Island, New York, USA
In the 2013 RHIC polarized proton run, it was found that the RHIC bunch intensity has reached a limit due to the head-on beam-beam interaction at 2x1011, as expected by simulations. To overcome this limitation, two electron lenses will be used for compensation. We report on the commissioning of new lattices that reduce beam-beam driven resonance driving terms, and bunch-by-bunch proton diagnostic during 2013 run. The effect of electron beam transport solenoids on the proton orbit was tested. The instrumentation for Blue electron lens was tested and electron beam was propagated from the gun to the collector. A timing system was implemented for the electron beam. Control software, machine protection and synoptic display were developed and tested during commissioning. Both Blue and Yellow electron lens superconducting magnets are installed and their field straightness was measured and corrected in the tunnel using a magnetic needle. The Yellow vacuum system and backscattered electron detectors installation are also completed now.
BNL, Upton, Long Island, New York, USA
To commission some of the hard and software for the RHIC electron lenses (e-lenses), a test bench was built based on the EBIS test stand at BNL. After several months of operation, the electron gun, collector, high-voltage gun modulator, instrumentation, partial control system, and several software applications have been tested. The nominal DC beam current of 0.85 A was demonstrated and the electron beam transverse profiles were verified to be Gaussian. Some e-lens power supplies and the electronics for current measurement were also evaluated on the test bench. The properties of the cathode and the profile of the beam are measured. In this paper, we will present some experimental results.
BNL, Upton, Long Island, New York, USA
Niowave, Inc., Lansing, Michigan, USA
A 5-cell SRF cavity operating at 704 MHz will be used for Coherent Electron Cooling Proof of Principle (CeC PoP) system under development for the Relativistic Heavy Ion Collider (RHIC) at Brookhaven National Laboratory. The CeC PoP experiment will demonstrate the ability of relativistic electrons to cool a single bunch of heavy ions in RHIC. The cavity will accelerate 2 MeV electrons from a 112 MHz SRF gun up 22 MeV. Novel mechanical designs, including the super fluid heat exchanger, helium vessel, vacuum vessel, tuner mechanism, and FPC are presented. Structural and modal analysis, using ANSYS were performed to confirm the cavity chamber and He vessel structural stability and to calculate the tuning sensitivity of the cavity. This paper provides an overview of the design, the project status and schedule of the 704 MHz 5-cell SRF for CeC PoP experiment.
BNL, Upton, Long Island, New York, USA
A Quarter-Wave Resonator (QWR) type SRF gun operating at 112 MHz will be used for Coherent Electron Cooling Proof of Principle (CeC PoP) system under development for the Relativistic Heavy Ion Collider (RHIC) at Brookhaven National Laboratory. The CeC PoP experiment will demonstrate the ability of relativistic electrons to cool a single bunch of heavy ions in RHIC. This cavity is designed to generate a 2 MeV, high charge (several nC), low repetition rate (78 kHz) electron beam using a new fundamental power coupler (FPC) design approach. Structural and thermal analysis, using ANSYS were performed to confirm the FPC structural stability and to calculate the deflection due to heat load from RF power generation. This paper provides an overview of the design, structural and thermal analysis, test results, and FPC tuning drive system for the 112 MHz gun.
BNL, Upton, Long Island, New York, USA
Stony Brook University, Stony Brook, USA
Niowave, Inc., Lansing, Michigan, USA
Fermilab, Batavia, USA
SBU, Stony Brook, New York, USA
STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom
Efforts to experimentally prove a concept of the coherent electron cooling are underway at BNL. A short 22-MeV linac will provide high charge, low repetition rate beam to cool a single ion bunch in RHIC. The linac will consist of a 112 MHz SRF gun, two 500 MHz normal conducting bunching cavities and a 704 MHz five-cell accelerating SRF cavity. The paper describes the SRF and RF systems, the linac layout, and discusses the project status, first test results and schedule.
BNL, Upton, Long Island, New York, USA
Based on the beam emittance measurement from the pickup, the RHIC Stochastic Cooling kicker uses sixteen narrowband high Q cavities (from 5 to 8 GHz) to kick (or to cool) the bunched beam on each of the two transverse planes in the two rings. The cavities are integrated to two pairs of cavity plates and installed in two UHV chambers. The new kicker features scissor like driving mechanism, frictionless flexure joints, water cooled cavity plates, small frequency shift (less than 0.05%) during the operation and maintenance free. Novel mechanical designs, including cavity plate, vacuum, cooling, driving mechanism, and support structure design, are presented. Structural and thermal analyses, using ANSYS, were performed to confirm chamber structural stability and to calculate the cavity plate deformation due to thermal and mechanical load. Good agreement between the calculated cavity plate deflection and the expected plate deformation from the cavity frequency shift measurements has been achieved. Three assemblies utilizing this design (1 for the vertical and 2 for the horizontal plane) were completed for the FY2012 run. Successful performance has been reported.
BNL, Upton, Long Island, New York, USA
The RHIC transverse Stochastic Cooling Pickup uses a pair of high resolution 4-8 GHz frequency band planar loop arrays to measure the Schottky signals from the bunched beams in the two transverse planes of the two rings. Precision alignment between the two 381 mm long array boards was achieved by surveying two specially designed target fixtures outside the vacuum chamber and using a pair of high resolution, motor controlled, and force balanced actuators. Robust mechanical design was achieved by excluding wearable mechanical joints and fragile electronics inside the vacuum chamber. Both mechanical designs and structural analysis results, for the vacuum chamber and for the array board supports, are presented. Two horizontal and two vertical plane pickups have been fabricated and installed in RHIC for the FY2012 run. Successful performance has been reported.
BNL, Upton, Long Island, New York, USA
Mechanical analysis of the RHIC beam dump window has shown that present heavy ion beam intensities are close to the tolerable limit, and will likely exceed that limit in future runs. Different approaches to upgrade the abort system for those projected higher intensities have been studied, namely replacing the existing window, and adding a vertical kicker that distributes the individual bunches more evenly across the window, thus reducing the heat load. We present the results of these studies and the present status of the upgrade project.