16 research outputs found
A NoâDepolarization Theorem for RotatorâAided Resonance Crossing
An rf frequency rotator magnet provides a useful tool for manipulating particle spins in any accelerator or storage ring with polarized beams. This note briefly demonstrates the general idea of the rotatorâaided crossing of spin resonance and sketches the proof of a general theorem about the process. The important question of whether this technique can be useful for a specific spin resonance at a particular accelerator involves a detailed analysis of the impact of the rotator on a range of machine parameters. © 2003 American Institute of PhysicsPeer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/87295/2/81_1.pd
Spin-flipping a stored polarized proton beam with an rf dipole
Frequent polarization reversals, or spin-flips, of a stored polarized high-energy beam may greatly reduce systematic errors of spin asymmetry measurements in a scattering asymmetry experiment. We studied the spin-flipping of a 120 MeV horizontally-polarized proton beam stored in the IUCF Cooler Ring by ramping an rf-dipole magnetâs frequency through an rf-induced depolarizing resonance in the presence of a nearly-full Siberian snake. After optimizing the frequency ramp parameters, we used multiple spin-flips to measure a spin-flip efficiency of 86.5±0.5%.86.5±0.5%. The spin-flip efficiency was apparently limited by the rf-dipoleâs field strength. This result indicates that an efficient spin-flipping a stored polarized beam should be possible in high energy rings such as RHIC and HERA where Siberian snakes are certainly needed and only dipole rf-flipper-magnets are practical. © 2000 American Institute of Physics.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/87561/2/662_1.pd
Single-Spin Observables and Orbital Structures in Hadronic Distributions
Within the light-quark sector of the standard model, P-odd observables are
generated from point-like electroweak processes while A_t- odd observables
(neglecting quark mass parameters) come from dynamic spin-orbit correlations
within hadrons or within larger composite systems, such as nuclei. The effects
of A_t-odd dynamics can be inserted into transverse-momentum dependent
constituent distribution functions and, in this paper, we construct the
contribution from an orbital quark to the A_t odd quark parton distribution.
Using this distribution, we examine the crucial role of initial- and
final-state interactions in the observation of the scattering asymmetries in
different hard-scattering processes. This construction provides a geometrical
and dynamical interpretation of the Collins conjugation relation between
single-spin asymmetries in semi-inclusive deep inelastic scattering and the
asymmetries in Drell-Yan production. Finally, our construction allows us to
display a significant difference between the calculation of a spin asymmetry
generated by a hard scattering mechanism involving color-singlet exchange (such
as a photon) and a calculation of an asymmetry with a hard-scattering exchange
involving gluons. This leads to an appreciation of the process dependence
inherent in measurements of single-spin observables.Comment: 35 pages, 6 figure
99.9% SpinâFlip Efficiency in the Presence of a Strong Siberian Snake
We recently studied the spinâflipping efficiency of an rfâdipole magnet using a 120âMeV horizontally polarized proton beam stored in the Indiana University Cyclotron Facility Cooler Ring, which contained a full Siberian snake. We flipped the spin by ramping the rf dipoleâs frequency through an rfâinduced depolarizing resonance. By adiabatically turning on the rf dipole, we minimized the beam loss, while preserving almost all of the beamâs polarization. After optimizing the frequency ramp parameters, we used up to 400 multiple spin flips to measure a spinâflip efficiency of 99.93 ± 0.02%. This result indicates that spin flipping should be possible in veryâhighâenergy polarized storage rings, where Siberian snakes are certainly needed and only dipole rfâflipper magnets are practical. © 2003 American Institute of PhysicsPeer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/87684/2/776_1.pd
Spin Flipping and Polarization Lifetimes of a 270 MeV Deuteron Beam
We recently studied the spin flipping of a 270 MeV vertically polarized deuteron beam stored in the IUCF Cooler Ring. We swept an rf solenoidâs frequency through an rfâinduced spin resonance and observed the effect on the beamâs vector and tensor polarizations. After optimizing the resonance crossing rate and setting the solenoidâs voltage to its maximum value, we obtained a spinâflip efficiency of about 94 ± 1% for the vector polarization; we also observed a partial spinâflip of the tensor polarization. We then used the rfâinduced resonance to measure the vector and tensor polarizationsâ lifetimes at different distances from the resonance; the polarization lifetime ratio Ïvector/Ïtensor was about 1.9 ± 0.4. © 2003 American Institute of PhysicsPeer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/87679/2/766_1.pd
Spin-flipping with an rf-dipole and a full Siberian snake
We recently used a vertical-field rf-dipole magnet to study the spin-flipping of a 120 MeV horizontally polarized proton beam stored in the presence of a nearly-full Siberian snake in the IUCF Cooler Ring. The spin was flipped by ramping the rf-dipoleâs frequency through an rf-induced depolarizing resonance. After optimizing the frequency ramp parameters, we used multiple spin-flips to measure a maximum spin-flip efficiency of 86.5±0.5%86.5±0.5% in April 2000, and 92.5±0.5%92.5±0.5% in June 2000. The spin-flip efficiency was apparently limited by the maximum achievable current in the rf-dipole. This result indicates that spin-flipping a stored polarized proton beam should be possible in high energy rings such as RHIC (and perhaps HERA in the future), where Siberian snakes are utilized and the dipole rf-flipper-magnets should be quite practical. During the June 2000 run, a new faster technique of locating the rf depolarizing resonance frequency was developed. © 2001 American Institute of Physics.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/87739/2/736_1.pd
Synchrotron-sideband snake depolarizing resonances
We recently created a snake depolarizing resonance using an rf solenoid magnet in a ring containing a nearly 100% Siberian snake. We found that the primary snake rf resonance also had two weaker synchrotron sidebands, which are second-order snake resonances; they were probably caused by the energy-dependent strength of the solenoid snake due to the Lorentz contraction of its longitudinal â« Bâ
dl.â«Bâ
dl. This was the first observation of an rf synchrotron-sideband depolarizing resonance in the presence of a nearly full Siberian snake. © 2001 American Institute of Physics.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/87740/2/893_1.pd