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
Stony Brook University, Stony Brook, USA
A compact cathode preparation chamber for the high current high polarization gun for the proposed eRHIC project has been designed and assembled at Brookhaven National Laboratory. This preparation chamber will be used to activate GaAs photocathodes to be used in the Gatling gun. The chamber is capable of achieving XHV on a consistent basis. Bulk GaAs samples were activated in this chamber with standard QE for the respective wavelength. In this paper, we discuss the design of this vacuum system, the heat cleaning and the activation procedure for the GaAs sample which will eventually be followed for the Gatling gun.
BNL, Upton, Long Island, New York, USA
The proposed electron ion collider (eRHIC) at Brookhaven National Laboratory requires a polarized electron source with high average current, short bunch length, and small emittance. The-state-of-the-art single polarized electron photocathode is far from delivering the required 50mA current due to ion back-bombardment limiting the cathode’s lifetime and surface charge limit. In our funneling gun design, currently under construction, the electron bunches, generated from 20 photocathodes in a 220 kV DC gun, funnel to a single common beam axis. This article details our design of a high-average-current polarized electron gun’s optics, and presents our simulation of beam dynamics and combiner design. We also report the progress of funneling gun construction here.
BNL, Upton, Long Island, New York, USA
A code for determining the beam emittance from a multi-slit image has been developed. To verify its validity, we simulated a beam distribution in 4D phase space at the multi-slit position and the resulting image at a downstream profile measurement device. We applied the algorithm to this image pattern to recover the beam emittance at the slit position. The dependence of the relative difference of the inferred emittance and the input emittance on the slit width and drift length are studied in detail and presented in this report.