Novel approach for spin-flipping a stored polarized beam

The traditional method of spin-flipping a stored polarized beam is based on slowly crossing an rf induced depolarizing resonance. This paper discusses a novel approach where the polarization reversal is achieved by trapping the beam polarization into a stable spin-flipping motion on top of the rf induced resonance at a half-revolution frequency.Comment: 8 pages, 2 figures, submitted to Phys. Rev. S.T.- Accel. & Beam

Radio-frequency polarimetry

A method of fast non-destructive absolute spin monitoring for a bunched beam in an accelerator ring based on use of the RF techniques is considered. The coherent spin of the beam is driven by RF magnets in the spin echo regime. A passive superconducting resonator is proposed to respond to the flipping spin. A possibility is established to enhance the spin-related excitation of the resonator using the charge-resonator dipole interaction and spin-orbit coupling induced by the quadrupoles. It is shown that the spin impedance can be gauged via measurements of the beam dipole impedance. The noise demands are evaluated. Numerical examples are given. © 1998 American Institute of Physics.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/87441/2/191_1.pd

On possibilities of fast cooling of heavy particle beams

Two methods of fast cooling of intensive beams are described. The first one, coherent electron cooling, is based on enhancement of friction effect in the electron cooling method using a microwave instability of electron beam specially arranged in the cooling section. This method is effective for cooling of high‐temperature circulating beams. The second one, self‐cooling, is based on use of the intrabeam Coulomb scattering of particles during the adiabatic processes of beam acceleration and transverse compression. This method allows frequent decrease emittance of an intensive beam issued by a low‐temperature source.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/87364/2/103_1.pd

The stimulated Stern‐Gerlach effect in charged particle storage rings

The results of the study of possibilities to use spin‐orbital force in order to split a circulating beam to two polarized beams are presented in this report. It is shown that the original spin‐splitter idea which is based on using intrinsic spin‐orbital resonance is not sufficient for splitting, in principle, because the spin’s long lasting effect on particle betatron oscillations is reduced just to a small tune shift. The theorem on the conservation of the sum or difference of quantum orbital and spin numbers, i.e. the combined spin‐orbital invariance, is established for this case. The resonant RF magnetic field parallel to the plane of splitting is introduced in order to stabilize spin in the plane of its precession and remove the combined invariance. The new double‐resonance invariants are established, which describe the spin dynamics and the splitting process.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/87412/2/327_1.pd

Strength of Higher-Order Spin-Orbit Resonances

When polarized particles are accelerated in a synchrotron, the spin precession can be periodically driven by Fourier components of the electromagnetic fields through which the particles travel. This leads to resonant perturbations when the spin-precession frequency is close to a linear combination of the orbital frequencies. When such resonance conditions are crossed, partial depolarization or spin flip can occur. The amount of polarization that survives after resonance crossing is a function of the resonance strength and the crossing speed. This function is commonly called the Froissart-Stora formula. It is very useful for predicting the amount of polarization after an acceleration cycle of a synchrotron or for computing the required speed of the acceleration cycle to maintain a required amount of polarization. However, the resonance strength could in general only be computed for first-order resonances and for synchrotron sidebands. When Siberian Snakes adjust the spin tune to be 1/2, as is required for high energy accelerators, first-order resonances do not appear and higher-order resonances become dominant. Here we will introduce the strength of a higher-order spin-orbit resonance, and also present an efficient method of computing it. Several tracking examples will show that the so computed resonance strength can indeed be used in the Froissart-Stora formula. HERA-p is used for these examples which demonstrate that our results are very relevant for existing accelerators.Comment: 10 pages, 6 figure

RF-resonance beam polarimeter Part I. Fundamental concepts

The possibility of an RF-resonance polarimeter (RFP) for fast non-destructive measurement of beam polarization in an accelerator ring is considered. In order to accumulate the transition radiation from the free oscillating coherent spin of the beam, a passive superconducting cavity is proposed. The increase of effective voltage in the cavity with time (related to beam polarization) is calculated here. The efficiency of the polarimeter does not decrease with beam energy and is proportional to the average beam current. A possible scheme of measurement of the accumulated voltage is presented. The noise limitations are taken into account and evaluated. Siberian snakes can be used in order to provide a sufficiently small value for the spin tune spread. Numerical examples are given.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/30447/1/0000071.pd

A tracking algorithm for the stable spin polarization field in storage rings using stroboscopic averaging

Polarized protons have never been accelerated to more than about $25$GeV. To achieve polarized proton beams in RHIC (250GeV), HERA (820GeV), and the TEVATRON (900GeV), ideas and techniques new to accelerator physics are needed. In this publication we will stress an important aspect of very high energy polarized proton beams, namely the fact that the equilibrium polarization direction can vary substantially across the beam in the interaction region of a high energy experiment when no countermeasure is taken. Such a divergence of the polarization direction would not only diminish the average polarization available to the particle physics experiment, but it would also make the polarization involved in each collision analyzed in a detector strongly dependent on the phase space position of the interacting particle. In order to analyze and compensate this effect, methods for computing the equilibrium polarization direction are needed. In this paper we introduce the method of stroboscopic averaging, which computes this direction in a very efficient way. Since only tracking data is needed, our method can be implemented easily in existing spin tracking programs. Several examples demonstrate the importance of the spin divergence and the applicability of stroboscopic averaging.Comment: 39 page