Formation of Polarized Proton Beams in the NICA Collider-Accelerator Complex

Abstract

Two schemes of the polarized proton beam formation are considered for the NICA accelerator complex. In the first scheme, the polarized proton beams are injected from the LILAC linear accelerator into the Nuclotron, where they are accelerated up to a kinetic energy of 1.5–2 GeV and then extracted to the Collider. The injected proton beams are accumulated in the Collider using the RF barriers and electron cooling. After accumulation, the protons are accelerated by the RF1 induction voltage up to the critical relativistic factor γ_tr = 7.089, where a jump of the betatron frequency occurs. After transition through the critical energy, the protons are accelerated up to the energy of the experiment. For this scheme, a specialized optical lattice is considered. The critical proton energy (γ_tr = 18.6) for this lattice is larger than the maximal energy of the experiment (12.6 GeV). The so-called spin transparency mode is planned to be used for formation of polarized beams in the Collider. In the second scheme, the polarized proton beams are injected into the Booster from LILAC. The protons are cooled in the Booster, accelerated, and extracted to the Nuclotron. During their acceleration in the Nuclotron, the protons cross the integer spin and spin-betatron resonances. After accelerating protons to the kinetic energy of the experiments of 6–10.86 GeV, the vertically polarized proton beams are transferred to the Collider. At the integer spin resonances following each other with the energy interval of 0.523 GeV, the partial Siberian snake permits the longitudinal polarization to be formed for beams used in the SPD and MPD detectors.