Spin Dynamics In Storage Rings Research Articles

Spin tune mapping as a novel tool to probe the spin dynamics in storage rings

Precision experiments, such as the search for electric dipole moments of charged particles using storage rings, demand for an understanding of the spin dynamics with unprecedented accuracy. The ultimate aim is to measure the electric dipole moments with a sensitivity up to 15 orders in magnitude better than the magnetic dipole moment of the stored particles. This formidable task requires an understanding of the background to the signal of the electric dipole from rotations of the spins in the spurious magnetic fields of a storage ring. One of the observables, especially sensitive to the imperfection magnetic fields in the ring is the angular orientation of stable spin axis. Up to now, the stable spin axis has never been determined experimentally, and in addition, the JEDI collaboration for the first time succeeded to quantify the background signals that stem from false rotations of the magnetic dipole moments in the horizontal and longitudinal imperfection magnetic fields of the storage ring. To this end, we developed a new method based on the spin tune response of a machine to artificially applied longitudinal magnetic fields. This novel technique, called spin tune mapping, emerges as a very powerful tool to probe the spin dynamics in storage rings. The technique was experimentally tested in 2014 using polarized deuterons stored in the cooler synchrotron COSY, and for the first time, the angular orientation of the stable spin axis at two different locations in the ring has been determined to an unprecedented accuracy of better than 2.8 μ rad.8 MoreReceived 6 March 2017DOI:https://doi.org/10.1103/PhysRevAccelBeams.20.072801Published by the American Physical Society under the terms of the Creative Commons Attribution 4.0 International license. Further distribution of this work must maintain attribution to the author(s) and the published article’s title, journal citation, and DOI.Published by the American Physical SocietyPhysics Subject Headings (PhySH)Research AreasBaryogenesis & leptogenesisBeam code development & simulation techniquesBeam diagnosticsBeam dynamicsBig bang nucleosynthesisElectric momentMagnetic momentNuclear tests of fundamental interactionsPolarization phenomenaAccelerators & Beams

Calculations of spin response functions in rings with Siberian Snakes and spin rotators

The so-called spin response formalism, which is linear response theory applied to spin dynamics in storage rings, can calculate the resonance strengths for spin flippers in storage rings of arbitrary structure, including rings with Siberian Snakes and spin rotators. We calculate so-called spin response functions for a model of the RHIC lattice, for various scenarios of spin rotator settings.

Potential for measurement of the tensor magnetic polarizability of the deuteron in storage ring experiments

General formulas describing deuteron spin dynamics in storage rings with allowance for the tensor electric and magnetic polarizabilities are derived. It is found that an initially tensor-polarized deuteron beam can acquire a final horizontal vector polarization of the order of 1%. This effect allows one to measure the tensor magnetic polarizability of the deuteron in storage ring experiments. We also confirm an existence of the effect found by Baryshevsky and Gurinovich, hep-ph/0506135 and Baryshevsky, hep-ph/0510158; hep-ph/0603191 that the tensor magnetic polarizability of the deuteron causes the spin rotation with two frequencies and experiences beating for polarized deuteron beams in storage rings.

Exceptional orbits: a new class of spin trajectories in circular accelerators

We claim there is a new class of spin trajectories in circular accelerators, which are not accounted for in current theories of spin dynamics. We call them exceptional orbits. On such orbits the spin motion drives a secular growth of the orbital amplitude(s). Our results do not by themselves prove the spatial separation of spin states of a relativistic charged particle beam, but our findings are consistent with those of other workers. Our findings do invalidate the unconditional use of the semiclassical approximation to treat the orbital motion, to diagonalize the spin–orbit Hamiltonian. We analyze a simple model in detail to demonstrate our ideas. We review the canonical transformation theory of spin dynamics in storage rings, and extend it to account for exceptional orbits. We also examine how exceptional orbits affect map-based algorithms. We show that the algorithms can sometimes break down, in ways not hitherto suspected. We show that on an exceptional orbit the secular rate of spin phase advance depends explicitly on the orbital arc-length, in contradiction to claims that the spin tune depends only on the orbital amplitudes.