BNL, Upton, Long Island, New York, USA
Fermilab, Batavia, Illinois, USA
FRIB, East Lansing, Michigan, 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.
BNL, Upton, Long Island, New York, USA
The QCD (Quantum Chromodynamics) phase diagram has many uncharted territories, particularly the nature of the transformation from Quark-Gluon plasma (QGP) to the state of Hadronic gas. The Beam Energy Scan I (BES-I) at the Relativistic Heavy Ion Collider (RHIC) was completed but measurements had large statistical errors. To improve the statistical error and expand the search for first-order phase transition and location of the critical point, Beam Energy Scan II will commence in 2019 with a goal of improving the luminosity by a factor of 3-4. The beam lifetime at low energies was and will be limited by some physical effects of which the most significant are intrabeam scattering, space charge, beam-beam, persistent current effects. This article will review these potential limiting factors and introduce the countermeasures which will be in place to improve BES-II luminosity.
BNL, Upton, Long Island, New York, USA
The design effort for the electron-ion collider eRHIC has concentrated on electron-proton collisions at the highest luminosities over the widest possible energy range. The present design also provides for electron-nucleon peak luminosities of up to 4.7·1033 cm-2s−1 with strong hadron cooling, and up to 1.7·1033 cm-2s−1 with stochastic cooling. Here we discuss the performance limitations and design choices for electron-ion collisions that are different from the electron-proton collisions. These include the ion bunch preparation in the injector chain, acceleration and intrabeam scattering in the hadron ring, path length adjustment and synchronization with the electron ring, stochastic cooling upgrades, machine protection upgrades, and operation with polarized electron beams colliding with either unpolarized ion beams or polarized He-3.
BNL, Upton, Long Island, New York, USA
KEK, Ibaraki, Japan
LBNL, Berkeley, California, USA
In the eRHIC, to compensate the geometric luminosity loss, local crab cavities on both sides of the interaction points are to adopted. The previous strong-strong beam-beam simulations showed that the luminosity degradation depends on the crab cavity frequency, proton synchrotron tune, proton bunch length and so on. In this article, we apply a combined strong-strong and weak-strong beam-beam simulation to investigate the incoherent and coherent beam motions with crabbed collison, and to calculate more realistic beam emittance growth rates and luminosity degradation rate.
BNL, Upton, Long Island, New York, USA
Fermilab, Batavia, Illinois, USA
For the proposed electron-ion collider eRHIC, an electron storage ring will be installed in the existing RHIC tunnel. To reach the high luminosity of up to 1034 cm-2 sec-1, beam currents up to 2.5A have to be stored. Besides high luminosity the physics program requires spin polarization levels of 70 percent, with both spin "up" and spin "down" orientations present in the fill. This is only feasible by using a full-energy spin polarized injector that replaces bunches faster than the depolarization rate. To limit the repetition rate of that injector to about one hertz, the polarization lifetime in the storage ring has to be maximized by proper spin matching and countermeasures for the machine misalignments. We will give an overview of the electron storage ring design.
BNL, Upton, Long Island, New York, USA
The future eRHIC collider * will collide 5, 10, and 18 GeV polarized electrons with 250 GeV polarized protons, 210 GeV/u polarized 3He ions and other heavy ion species which are already produced by the RHIC accelerator. To increase the luminosity during collisions the number of circulating hadron bunches will increase to 330 and this requires a modification of the injection hadrons into the RHIC accelerator. This paper describes this injection scheme which is compatible with a design option which uses two hadron rings, one ring for accelerating the hadron beam and the other ring for storing the circulating beam to increase even further the integrated luminosity of the electron-hadron collisions. This two-hadron-rings option will be presented in the conference.
tsoupas@bnl.gov
* ICFA BD Newsletter No. 74 http://icfa-bd.kek.jp/