Abstract
Depolarization response for a system of two orthogonal snakes at irrational tunes is studied in depth using lattice independent spin integration. In particular we consider the effect of overlapping spin resonances in this system, to understand the impact of phase, tune, relative location and threshold strengths of the spin resonances. These results are benchmarked and compared to two dimensional direct tracking results for the RHIC e-lens lattice and the standard lattice. Finally we consider the effect of longitudinal motion via chromatic scans using direct six dimensional lattice tracking.
Highlights
A major limitation for the luminosity in colliders is due to head-on beam-beam collisions that lead to emittance blow-up at sufficiently high intensity
In order to compensate for the beam-beam collision, an electron lens (e-lens) [1,2,3] has been installed in each ring of the Relativistic Heavy Ion Collider (RHIC)
Compared with the standard lattice used during run 2012, both the Blue and Yellow ring e-lens lattices had lower values for the three very strong intrinsic spin resonances above 100 GeV
Summary
A major limitation for the luminosity in colliders is due to head-on beam-beam collisions that lead to emittance blow-up at sufficiently high intensity. The neighboring weak resonances were larger than in the run 2012 lattice (see Fig. 1) This we attribute, at least in part, to the asymmetric phase advances around the RHIC rings imposed by the operational requirements of the new e-lens lattices. The initial expectation was that polarization transmission through the RHIC ramp would improve, since each individual intrinsic resonance was well below the depolarization threshold in the presence of two snakes. The results from the 2013 polarized proton run did not, show strong evidence of the expected improvement; polarization transmission through the RHIC ramp may have suffered To understand this effect, we used the newly-developed code TEASPINK [9] to perform twodimensional (2D) and six-dimensional (6D) spin-orbit tracking on a platform using both message passing interface (MPI) and graphical processing units (gpu). We present a possible approach to greatly expand the polarization aperture by minimizing the neighboring resonances
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