Vahid Ranjbar

ACCURATE AND EFFICIENT SPIN INTEGRATION FOR PARTICLE ACCELERATORS

Accurate spin tracking is a valuable tool for understanding spin dynamics in particle accelerators and can help improve the performance of an accelerator. In this paper, we present a detailed discussion of the integrators in the spin tracking code gpuSpinTrack. We have implemented orbital integrators based on drift-kick, bend-kick, and matrix-kick splits. On top of the orbital integrators, we have implemented various integrators for the spin motion. These integrators use quaternions and Romberg quadratures to accelerate both the computation and the convergence of spin rotations. We evaluate their performance and accuracy in quantitative detail for individual elements as well as for the entire RHIC lattice. We exploit the inherently data-parallel nature of spin tracking to accelerate our algorithms on graphics processing units.

Re-visiting RHIC snakes: OPERA fields, n 0 dance

Tech. Note C-A/AP/590 BNL C-AD

Polarized e-bunch acceleration at Cornell RCS: Tentative tracking simulations

An option as an injector into eRHIC electron storage ring is a rapid-cyclic synchrotron (RCS). Rapid acceleration of polarized electron bunches has never been done, Cornell synchrotron might lend itself to dedicated tests, which is to be first explored based on numerical investigations. This paper is a very preliminary introduction to the topic. eRHIC Note 57 BNL C-AD Sept. 2017

RHIC Performance with Stochastic Cooling for Ions and Head-on Beam-beam Compensation for Protons

The Relativistic Heavy Ion Collider (RHIC) has two main operating modes with heavy ions and polarized protons respectively. In addition to a continuous increase in the bunch intensity in all modes, two major new systems were completed recently mitigating the main luminosity limit and leading to significant performance improvements. For heavy ion operation stochastic cooling mitigates the effects of intrabeam scattering, and for polarized proton operation head-on beam-beam compensation mitigates the beam-beam effect. We present the performance increases with these upgrades to date, as well as an overview of all operating modes past and planned.

Beam-beam Interaction in the Asymmetric Energy Gold-gold Collision in RHIC

In this article, we study the beam-beam interaction in a possible future gold-gold collision with different particle energies in the Relativistic Heavy Ion Collider (RHIC). Since RF harmonic numbers are different for the two rings, bunches collide in 110 or 111 turn followedby 10 turns without collision. We will carry out 6-D numeric simulations to study the stability of bunch centers and the transverse emittance growth. The nonlinear beam-beam interaction force, chromaticities, and synchrotron motion are included. Both weak-strong and strong-strong simulation models are used.

Optics Setup in the AGS and AGS Booster for Polarized Helion Beam

Future RHIC physics program calls for polarized helion beam. The helion beam from the new EBIS source has a relative low rigidity which requires delicate control of injection and RF setup in the Booster. The strong depolarization resonance strength in both AGS and AGS Booster requires careful consideration of beam energy range and optics setup. Recently, the unpolarized helion beam was accelerated to 11GeV/n in the AGS. The optics with special tune path has been tested in both AGS and the Booster. The near term goal of 4×10/bunch at RHIC injection requires several RF bunch merges in both AGS and the Booster. The beam test results are presented in this paper.

Design and Interpretation of Colliding Pulse Injected Laser-Plasma Acceleration Experiments

The use of colliding laser pulses to control the injection of plasma electrons into the plasma wake of a laser‐plasma accelerator is a promising approach to obtaining GeV scale electron bunches with reduced emittance and energy spread. Colliding Pulse Injection (CPI) experiments are being performed by groups around the world. We present recent particle‐in‐cell simulations, using the parallel VORPAL framework, of CPI for physical parameters relevant to ongoing experiments of the LOASIS program at LBNL. We perform parameter scans in order to optimize the quality of the bunch, and compare the results with experimental data. Effect of non‐ideal gaussian pulses and laser self‐focusing in the plasma channel on the trapped bunch are evaluated. For optimized parameters accessible in the experiment, a 20 pC electron beam can be accelerated to 300 MeV with percent level energy spread.