Meaningful prediction and enhancement of spin-polarization in the RHIC/EIC accelerator complex relies on accurate modeling of each sub-component. Here we describe a symplectic field approximations of both Siberian Snakes in the AGS, enabling practical long-term tracking calculations. Without such symplectic representations, particle motion destabilizes very quickly close to injection energy. This optical instability manifests in $O(10^3)$ turns, and makes dynamic aperture smaller than realistic emittances. Combined with optimization using the Bmad toolkit, we implement steering and optical corrections of the snake effects at 80 distinct energies from injection to extraction, mimicking the measured lattice conditions at each energy. This process unveils unforeseen snake distortions of the vertical dispersion near injection energy, which are addressed. By interpolating between such optimized lattice configurations, Bmad's tracking capabilities allow advanced simulation of polarization transmission through the full AGS cycle.

We report on a week-long study of a conceptual design of EUV FEL light source based on an energy recovery linac with on-orbit laser plasma accelerator injection scheme. We carried out this study during USPAS Summer 2023 session of Unifying Physics of Accelerators, Lasers and Plasma applying the art of inventiveness TRIZ. An ultrashort Ti-sapphire laser accelerates electron beams from a gas target with mean energy of 20 MeV, which are then ramped up to 1 GeV in a five-turn scheme with a series of fixed field alternating magnets and two superconducting RF cavities (100 MeV per cavity per turn). The electron beam is then bypassed to an undulator line optimized to generate EUV light of 13.5 nm at kW level in a single pass.

The model of spin depolarization invoking isolated resonances hinges on a closed-form solution of energy ramping with the Single Resonance Model by Froissart and Stora. However, for non-resonant orbital tunes, resonant depolarization by single resonance crossing is impossible in the SRM while using a pair of Siberian Snakes since the amplitude-dependent spin tune is then fixed to one-half. Polarization loss in RHIC demonstrates that the isolated resonances model is not a good approximation of polarization dynamics with two Siberian Snakes. We therefore extend the model in which a pair of resonances in close proximity push the amplitude-dependent spin tune away from one-half in the presence of Siberian Snakes, allowing the crossing of higher-order spin resonances associated with depolarization. We present results from applying Machine Learning methods that establish spin transport models with two overlapping resonances from tracking data.

Meaningful prediction and enhancement of spin-polarization in the RHIC/EIC accelerator complex relies on accurate modeling of each sub-component. Here we describe a symplectic field approximations of both Siberian Snakes in the AGS, enabling practical long-term tracking calculations. Without such symplectic representations, particle motion destabilizes very quickly close to injection energy. This optical instability manifests in $O(10^3)$ turns, and makes dynamic aperture smaller than realistic emittances. Combined with optimization using the Bmad toolkit, we implement steering and optical corrections of the snake effects at 80 distinct energies from injection to extraction, mimicking the measured lattice conditions at each energy. This process unveils unforeseen snake distortions of the vertical dispersion near injection energy, which are addressed. By interpolating between such optimized lattice configurations, Bmad's tracking capabilities allow advanced simulation of polarization transmission through the full AGS cycle.

In December 2021, damage to a couple of RHIC power supplies forced one of two Siberian Snakes in the Blue ring to operate as a partial Siberian Snake and with a different snake axis of rotation. The time-averaged polarization for that run actually ended up higher than in the Yellow ring, after casting the undamaged snake as a partial snake as well. In this work, we simulate polarization transmission through a series of increasingly realistic models of the Blue ring in the “dangerous region” of polarization loss. At first the bare lattice has a perfect closed-orbit and ideal magnet strengths. Then the measured magnet-to-magnet field strength variations were added to the lattice. Finally, the six Interaction Region 5mm closed orbit bumps were implemented. Each of these model lattices compared the use of a pair of partial snakes against a pair of a full snakes, and in simulations with realistic emittances, realistic polarization losses were not reproducible without inclusion of nonzero RMS lattice misalignments.

Slow resonant extraction plays a crucial role in delivering a high-quality continuous beam to experiments. Simulating extraction and transport of charged particle beams require a process of careful modeling and experimentation. There are various particle tracking simulation tools available to use. Each has its merits and deficiencies. In this work we have used long-term tracking based on the Bmad toolkit to run third integer resonant extraction simulations of beams of various ion species in the booster synchrotron at Brookhaven National Laboratory. In this paper, we will present results of detailed slow extraction, multi-particle tracking simulations, and we will describe the features that make Bmad a useful tool for this work. We will show comparisons to other simulation tools of our results.

The Ring Electron Cooler (REC) is currently under design for use in the Electron Ion Collider (EIC) for hadron cooling. In this device the hadrons are cooled by the electrons and the electrons are cooled through radiation damping, which is enhanced by a number of 4 meter-long wigglers with 2.4 T field. When optimizing the beam envelope, intra beam scattering and Touschek scattering are also considered. Using a field configuration with additional focusing to keep the emittance at an acceptable value, these wigglers make up a substantial portion of the ring, with the wiggler section contributing the majority of the ring’s chromaticity. In this paper, the effects of the REC’s unusual properties on dynamic aperture are analyzed and a correction scheme is proposed.

The Electron Ion Collider calls for collisions of helion beam on polarized electron beams. Polarized helions will be injected into the Hadron Storage Ring at |Gγ| = 49.5 and have a maximum energy corresponding to |Gγ| = 820. Simulations of helions in this energy range have been performed using zgoubi. These studies quantify the polarization transmission with six snakes and also categorize the lattice constraints.

Pairs of Siberian Snakes allow the avoidance of first-order spin resonances during energy ramping. However, a high density of first-order resonances correlates with the presence of higher-order resonances after the installation of snakes. Thus, one effective tactic of mitigating higher-order resonances is by weakening the surrounding first-order ones, equivalent to minimizing the spin-orbit coupling integrals. Such a proxy helps sidestep a multi-hour polarization transmission simulation for each lattice configuration. In a three-fold super-periodic ring, using 12 snakes is a sufficient condition for completely eliminating the spin-orbit coupling integrals at all energies and tunes. Since the HSR will only have up to 6 snakes, we opt to focus on suppressing the strongest first-order resonances instead of the whole spectrum. By varying the snake reflection axes and the betatron phase advance in two of the arcs, we search in a 7-dimensional lattice space for the weakest resonance structure using a variety of metrics and find the configuration with highest polarization transmission.

The RHIC heavy ion program relies on a series of RF bunch merge gymnastics to combine individual source pulses into bunches of suitable intensity. Intensity and emittance preservation during these gymnastics require careful setup of the voltages and phases of RF cavities operating at several different harmonic numbers. The optimum setting tends to drift over time, degrading performance and requiring operator attention to correct. We describe a reinforcement learning approach to learning and maintaining an optimum configuration, accounting for the relevant RF parameters and external perturbations (e.g., a changing main dipole field) using a physics-based simulator at Brookhaven Alternating Gradient Synchrotron (AGS).