First Observation of a Snake Depolarizing Resonance

Phelps, R. A.; Anferov, V. A.; Blinov, B. B.; Crandell, D. A.; Koutin, S. V.; Krisch, A. D.; Liu, T. J.; Ratner, L. G.; Wong, V. K.; Chu, C. M.; Lee, S. Y.; Rinckel, T.; Schwandt, P.; Sperisen, F.; Stephenson, E. J.; Przewoski, B. von; Sato, Hikaru

doi:10.1103/physrevlett.78.2772

Cited by 19 publications

(15 citation statements)

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“…The apparatus used for this experiment, including the rf dipole, the IUCF Cooler Ring, and the polarimeter, were discussed earlier [6,[9][10][11][12][13][14][15][16][17][18][19][20][21][22][23] and are shown in Fig. 1.…”

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Spin flipping with an rf dipole and a full Siberian snake

Blinov

Derbenev

Kageya

et al. 2000

Phys. Rev. ST Accel. Beams

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We recently used an 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 Indiana University Cyclotron Facility Cooler Ring. We flipped the spin by ramping the rf dipole's frequency through an rf-induced depolarizing resonance. After optimizing the frequency ramp parameters, we used multiple spin flips to measure a spin-flip efficiency of 86.5 6 0.5%. The spin-flip efficiency was apparently limited by the field strength in the rf dipole. This result indicates that spin flipping a stored polarized proton beam should be possible in high energy rings such as the Brookhaven Relativistic Heavy Ion Collider and HERA where Siberian snakes are certainly needed and only dipole rf-flipper magnets are practical. PACS numbers: 29.27.Bd, 29.27.Hj, 41.75.Ak Polarized beam experiments are now a major component of the programs in storage rings such as the Indiana University Cyclotron Facility (IUCF) Cooler Ring [1], the MIT-Bates Storage Ring [2], the Brookhaven Relativistic Heavy Ion Collider [3], and HERA at DESY [4]. Frequent reversals of the beam polarization direction can significantly reduce the systematic errors in an experiment's spin asymmetry measurements. An rf solenoid was used earlier to spin flip a horizontally polarized proton beam stored in the Cooler Ring containing a Siberian snake [5] with 97 6 1% spin-flip efficiency [6]. However, a solenoid's spin rotation decreases linearly with energy because of the Lorentz contraction of its R B dl; thus, a solenoid is impractical for spin flipping in high energy rings. Fortunately, a dipole's spin rotation is energy independent. Therefore, we recently used an rf dipole to spin flip a 120 MeV horizontally polarized proton beam stored in the IUCF Cooler Ring with a nearly full Siberian snake.In any flat circular accelerator or storage ring with no horizontal magnetic fields, each proton's spin precesses around the vertical fields of the ring's dipole magnets. The spin tune n s , which is the number of spin precessions during one turn around the ring, is proportional to the proton's energywhere G ͑g 2 2͒͞2 1.792 847 is the proton's gyromagnetic anomaly and g is its Lorentz energy factor. This vertical spin precession can be perturbed by the horizontal rf magnetic field from either an rf solenoid or an rf dipole. This perturbation can induce an rf depolarizing

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confidence: 99%

Spin flipping with an rf dipole and a full Siberian snake

Blinov

Derbenev

Kageya

et al. 2000

Phys. Rev. ST Accel. Beams

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“…[2]. As stated above, experimental observations of snake resonances have been made at the IUCF Cooler Ring [5] and RHIC [6]. We now arrive at what seems to be the heart of the criticisms in BEH.…”

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confidence: 88%

Comment on “Quasiperiodic spin-orbit motion and spin tunes in storage rings”

Lee

Mane

2005

Phys. Rev. ST Accel. Beams

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“…This is the same condition as for full snake resonances [11,12]. The polarization was measured as a function of the vertical betatron tune in the vicinity of several intrinsic resonances.…”

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Overcoming Depolarizing Resonances with Dual Helical Partial Siberian Snakes

et al. 2007

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Acceleration of polarized protons in the energy range of 5 to 25 GeV is challenging. In a medium energy accelerator, the depolarizing spin resonances are strong enough to cause significant polarization loss but full Siberian snakes cause intolerably large orbit excursions and are also not feasible since straight sections usually are too short. Recently, two helical partial Siberian snakes with double pitch design have been installed in the Brookhaven Alternating Gradient Synchrotron (AGS). With a careful setup of optics at injection and along the energy ramp, this combination can eliminate the intrinsic and imperfection depolarizing resonances otherwise encountered during acceleration to maintain a high intensity polarized beam in medium energy synchrotrons. The observation of partial snake resonances of higher than second order will also be described.

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First Observation of a Snake Depolarizing Resonance

Cited by 19 publications

References 14 publications

Spin flipping with an rf dipole and a full Siberian snake

Spin flipping with an rf dipole and a full Siberian snake

Comment on “Quasiperiodic spin-orbit motion and spin tunes in storage rings”

Overcoming Depolarizing Resonances with Dual Helical Partial Siberian Snakes

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