An AC dipole has been installed in the AGS booster as part of polarized beam developments for the future Electron Ion Collider (EIC). This will allow preserving helion beam polarization through two intrinsic resonances during acceleration to an energy corresponding to |Gγ| = 10.5. AC dipoles can preserve polarization by forcing the beam to undergo large amplitude vertical betatron oscillations. These coherent oscillations cause all particles to sample the strong horizontal fields of quadrupoles, and result in a full spin flip. In preparation for the AC dipole being used for polarized helions, it was first commissioned with polarized protons. The proton extraction energy was raised to allow protons to cross Gγ=0+νy = 4.8087. As an artifact of the experiment using polarized protons, the booster settings for bunch extraction interfered with the coherent oscillations and limited the maximum coherent amplitude. This interference will be well separated in the case of polarized helions. Polarized protons crossed the Gγ=0+νy intrinsic resonance with a full spin flip through use of the AC dipole. Simulations of the resonance crossing using Zgoubi accurately predict the polarization relative to the coherent amplitude.

RHIC provided Au+Au collisions at beam energies of 5.75 and 4.59 GeV/nucleon for the physics program in 2020 as part of the Beam Energy Scan II experiment. The machine configuration and operational experience at these energies are presented in this report with emphasis on their unique features which include but are not limited to the addition of a second RF system to enable large longitudinal acceptance and to reduce the intrabeam scattering rate at 5.75 GeV/nucleon, the exploration of the tune space for better performance, the use of lower frequency cavities for alleviating space charge effects, and the world-first operation of cooling on colliding beams with an RF-accelerated bunched electron beam.

In polarized proton collision experiments, spin flip is needed to reduce the systematic errors. At high energy colliders with Siberian snakes, a single magnet spin flipper does not work . A more sophisticated spin flipper, constructed of nine-dipole magnets, was used to flip the spin in the BNL Relativistic Heavy Ion Collider. A 97% spin-flip efficiency was measured at both 24 and 255 GeV. The spin flip experiment results are presented in this paper.

The p-carbon polarimeter working in the dp/p Coulomb Nuclear Interference (CNI) region has been used in the Brookhaven Alternating Gradient Synchrotron (AGS ) for many years. It has gone though several upgrades to improve its performance. With targets sweeping through beam vertically and horizontally, the polarimeter can provide polarization profile information. To preserve polarization, a pair of horizontal tune jump quads have been used to overcome horizontal intrinsic resonances. Recently, the polarization measurement on the energy ramp has been used to decide the beam energy as function of time on the ramp. This paper summarize the recent operation experience of AGS p-carbon CNI polarimeter.

Polarized 3He collisions are part of future RHIC physics programs and of the eRHIC project. The anomalous magnetic moment of 3He (G=-4.184) is roughly three times greater than that of protons (G=1.793), a polarized species that is already used at the Collider-Accelerator complex at BNL. Because of the higher anomolous magnetic moment and possibly injecting into the AGS at rigidities beyond 7 T • m, 3He may have to cross depolarizing intrinsic resonances while accelerating in the Booster. To overcome these strong intrinsic resonances we look to an AC-dipole, which will need to be installed in the Booster. An AC-dipole is a magnet that induces large betatron oscillations which forces the entire bunch to experience a stronger resonance and induce a spin flip of all particles. An artificial intrinsic resonance is created, with close proximity to the original intrinsic resonance, which requires simulations to gauge what magnet strength is required. Simulations have been performed using zgoubi regarding the resonances 0 + vy, 12 - vy, and 6 + vy and show that the AC-dipole is effective at overcoming these resonances. Benefits of avoiding the 0 + vy and crossing the 12 - vy and 6 + vy in the Booster presents the advantage of allowing injection above the 0 + vy in the AGS and minimizes the orbit distortions from the snakes.