Depolarizing 'beat' Resonances in the Brookhaven AGS

While accelerating polarized protons in the Brookhaven AGS we found a variant of the standard imperfection and intrinsic depolarizing resonances which has some of the properties of both types. Imperfection resonances occur at Gγ = k, when the number of spin precessions per revolution, Gγ, equals a h...

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Bibliographic Details
Published inIEEE transactions on nuclear science Vol. 32; no. 5; pp. 2635 - 2637
Main Authors Terwilliger, K. M., Krisch, A. D., Courant, E. D., Ratner, L. G.
Format Journal Article
LanguageEnglish
Published IEEE 01.10.1985
Subjects
Acceleration
Amplitude modulation
Frequency
Laboratories
Magnetic fields
Magnetic resonance
Particle beams
Polarization
Protons
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Summary:While accelerating polarized protons in the Brookhaven AGS we found a variant of the standard imperfection and intrinsic depolarizing resonances which has some of the properties of both types. Imperfection resonances occur at Gγ = k, when the number of spin precessions per revolution, Gγ, equals a harmonic of the depolarizing field, k. Intrinsic resonances occur at Gγ = nP±νZ, when the AGS gradient periodicities, nP, modulate free vertical betatron oscillations to create the sum and difference frequencies. The variant resonance is a beat between nP and an imperfection driven betatron oscillation of periodicity k'. These occur at Gγ = nP±k', and are strongest when the driven betatron oscillation is largest. The effect was most dramatic at the strong Gγ = 27 resonance. Since νZ = 8.8 for the AGS, and there is a major nP = 36 AGS periodicity, a strong beat resonance should exist at Gγ = 36-9 = 27. Applying a 27th harmonic correction directly was unsuccessful, but a 9th harmonic correction removed the depolarization.
ISSN:0018-9499
1558-1578
DOI:10.1109/TNS.1985.4334005