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Title: Online Nonlinear Chromaticity Correction Using Off-Momentum Tune Response Matrix

Authors:
; ; ;
Publication Date:
Research Org.:
Brookhaven National Laboratory (BNL) Relativistic Heavy Ion Collider
Sponsoring Org.:
USDOE SC OFFICE OF SCIENCE (SC)
OSTI Identifier:
1061854
Report Number(s):
BNL-99413-2013-IR
KB0202011
DOE Contract Number:
DE-AC02-98CH10886
Resource Type:
Technical Report
Country of Publication:
United States
Language:
English
Subject:
43; relativistic heavy ion collider

Citation Formats

Luo Y., Fischer, W., Tepikian, S., and Trbojevic, D. Online Nonlinear Chromaticity Correction Using Off-Momentum Tune Response Matrix. United States: N. p., 2007. Web. doi:10.2172/1061854.
Luo Y., Fischer, W., Tepikian, S., & Trbojevic, D. Online Nonlinear Chromaticity Correction Using Off-Momentum Tune Response Matrix. United States. doi:10.2172/1061854.
Luo Y., Fischer, W., Tepikian, S., and Trbojevic, D. Mon . "Online Nonlinear Chromaticity Correction Using Off-Momentum Tune Response Matrix". United States. doi:10.2172/1061854. https://www.osti.gov/servlets/purl/1061854.
@article{osti_1061854,
title = {Online Nonlinear Chromaticity Correction Using Off-Momentum Tune Response Matrix},
author = {Luo Y. and Fischer, W. and Tepikian, S. and Trbojevic, D.},
abstractNote = {},
doi = {10.2172/1061854},
journal = {},
number = ,
volume = ,
place = {United States},
year = {Mon Jan 01 00:00:00 EST 2007},
month = {Mon Jan 01 00:00:00 EST 2007}
}

Technical Report:

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  • In this article, we propose a method for the online nonlinear chromaticity correction at store in the Relativistic Heavy Ion Collider (RHIC). With 8 arc sextupole families in each RHIC ring, the nonlinear chromaticities can be minimized online by matching the off-momentum tunes onto the wanted tunes given by the linear chromaticities. The Newton method is used for this multi-dimensional nonlinear optimization, where the off-momentum tune response matrix with respect to sextupole strength changes is adopted. The off-momentum tune response matrix can be calculated with the online accelerator optics model or directly measured with the real beam. In this article,more » the correction algorithm for the RHIC is presented. Simulations are also carried out to verify the method. The preliminary results from the beam experiments taken place in the RHIC 2007 Au run are reviewed.« less
  • .
  • Orbit Response Matrix (ORM) analysis is a technique used to diagnose and correct optics errors in storage rings. We report the results obtained from the use of ORM analysis at the KEK-ATF to reduce the equilibrium vertical emittance. Measurements of the vertical beam size using a laser wire indicate that the vertical emittance was successfully reduced from 12 pm to around 6 pm (at a bunch charge of 7 x 10{sup 9} particles) using ORM analysis.
  • A tracking study was done of the effects of a tune modulation, due to synchrotron oscillations and the tune dependence on momentum (chromaticity), on the dynamic aper­ ture. The studies were done using several RHIC lattices and tracking runs of about 1 x 10 6 turns. The dynamic aperture was found to decrease roughly linearly with the amplitude of the tune modulation and may be represented by A = A 0 (1-10 Δv) where A 0 is the dynamic aperture for Δv = 0, and Δv is the tune modulation amplitude. In Eq. (1), the range of Δv is suchmore » that lower order non-linear resonances, like the 1/3 and 1/4 resonance are not crossed because of the tune modulation. Three different cases were studied, corresponding to RHIC lattices with different β*, and with different synchrotron oscillation amplitudes. In each case, the tune modulation amplitude was varied by changing the chromaticity. In each case, roughly the same result, Eq. (1), was found. The result found here for the effect of a tune modulation due to chromaticity may be compared with the result found for the effect of a tune modulation due to a gradient ripple in the quadrupoles, which was A 0 (1-42 Δv). The effect of a Δv due to a gradient ripple appears to be about 4 times stronger than the effect of a Δv due to chromaticity and synchrotron oscillations.« less