BNL, Upton, Long Island, New York
Funding: Work supported by Brookhaven Science Associates, LLC under Contract No. DE-AC02-98CH10886 with the U.S. Department of Energy.
After having provided collisions of polarized protons at a beam energy of 100 GeV since 2001, the Relativistic Heavy Ion Collider~(RHIC) at BNL reached its design energy of polarized proton collision at 250 GeV. With the help of the two full Siberian snakes in each ring as well as careful orbit correction and working point control, polarization was preserved during acceleration from injection to 250~GeV. During the course of the Physics data taking, the spin rotators on either side of the experiments of STAR and PHENIX were set up to provide collisions with longitudinal polarization at both experiments. Various techniques to increase luminosity like further beta star squeeze and RF system upgrades as well as gymnastics to shorten the bunch length at store were also explored during the run. This paper reports the performance of the run as well as the plan for future performance improvement in RHIC.
BNL, Upton, Long Island, New York
A linac-ring eRHIC design requires a high-intensity CW source of polarized electrons. An SRF gun is viable option that can deliver the required beam. Numerical simulations presented elsewhere have shown that ion bombardment can occur in an RF gun, possibly limiting lifetime of a NEA GaAs cathode. In this paper, we analytically solve the equations of motion of ions in an RF gun using the ponderomotive potential of the RF field. We apply the method to the BNL 1/2-cell SRF photogun and demonstrate that a significant portion of ions produced in the gun can reach the cathode if no special precautions are taken. Also, the paper discusses possible mitigation techniques that can reduce the rate of ion bombardment.
BNL, Upton, Long Island, New York
This paper will present the preliminary results of the testing of the 703 MHz SRF cryomodule designed for use in the ampere class ERL under construction at Brookhaven National Laboratory. The preliminary VTA cavity testing, carried out at Jefferson Laboratory, demonstrated cavity performance of 20 MV/m with a Qo of 1x1010, results we expect to reproduce in the horizontal configuration. This test of the entire string assembly will allow us to evaluate all of the additional cryomodule components not previously tested in the VTA and will prepare us for our next milestone test which will be delivery of electrons from our injector through the cryomodule to the beam dump. This will also be the first demonstration of an accelerating cavity designed for use in an ampere class ERL, a key development which holds great promise for future machines.
BNL, Upton, Long Island, New York
MIT, Middleton, Massachusetts
Funding: Work performed under US DOE contract DE-AC02-98CH1-886
Design of a medium energy electron-ion collider (MEeIC) is under development at Collider-Accelerator Department, BNL. The design envisions a construction of 4 GeV electron accelerator in a local area inside the RHIC tunnel. The electrons will be produced by a polarized electron source and accelerated in the energy recovery linac. Collisions of the electron beam with 100 GeV/u heavy ions or with 250 GeV polarized protons will be arranged in the existing IP2 interaction region of RHIC. The luminosity of electron-proton collisions at 1032 cm-2 s-1 level will be achieved with 40 mA CW electron current with presently available parameters of the proton beam. Efficient cooling of proton beam at the collision energy may bring the luminosity to 1033 cm-2 s-1 level. The important feature of the MEeIC is that it would serve as first stage of eRHIC, a future electron-ion collider at BNL with both higher luminosity and energy reach. The majority of the MEeIC accelerator components will be used for eRHIC.