Abstract
Hadron polarization control schemes for Spin Transparent (ST) synchrotrons are analyzed. The spin dynamics and beam polarization in such synchrotrons are controlled by spin navigators (SN) which are special small insertions of weak magnetic fields. An SN stabilizes the beam polarization and allows for setting any desirable spin orientation at an interaction point in the operational regime, including a frequent spin flip. We present a general approach to design of SNs. We distinguish different types of SNs, namely, those not causing closed orbit perturbation as well as those producing local and global orbit distortions. In the second case, the concept of the spin response function in an ST synchrotron is applied and expanded to reveal the effect of the SN strength enhancement by magnetic lattice of the synchrotron. We provide conceptual schemes for SN designs using longitudinal and transverse magnetic fields allowing for polarization control at low as well as high energies. We also develop the ST concept for ultra-high energies. This development may enable and stimulate interest in polarized beam experiments in possible polarized collider projects such as Large Hadron Collider (LHC), Future Circular Collider (FCC) and Super Proton Proton Collider (SPPC).
Highlights
Origin of the spin of a nucleon is one of the fundamental questions of modern nuclear physics [1]
In the Spin Transparent (ST) mode, the particles are technically in the region of a spin resonance (ST resonance) where the spin motion is highly sensitive to small perturbations in magnetic fields
We introduce a coefficient describing the enhancement of the navigator strength by the ring optics
Summary
Origin of the spin of a nucleon is one of the fundamental questions of modern nuclear physics [1]. In the ST mode, the particles are technically in the region of a spin resonance (ST resonance) where the spin motion is highly sensitive to small perturbations in magnetic fields This allows for flexible control of the polarization direction by weak-field SNs. For stability of the spin dynamics, the spin effect of the navigator fields must significantly exceed that due to imperfections and misalignments of the collider elements as well as the effect due to the orbital beam emittances. Let us emphasize the different roles of the weak navigator and strong structural magnetic fields The former “guide” the stable polarization direction nnav in the collider: a spin initially directed along nnav steadily repeats its orientation every particle turn while spins directed transversely to nnav are not stable and precess about nnav by a small angle every particle turn 2π νnav. We give examples of SN schemes for polarization control in different ranges of collider energies starting with low and ending with ultra-high energies
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