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Title: A Standard FODO Lattice with Adjustable Momentum Compaction

Abstract

An existing lattice made of identical FODO cells can be modified to have adjustable momentum compaction.

Authors:
 [1];  [1]
+ Show Author Affiliations
  1. Brookhaven National Lab. (BNL), Upton, NY (United States)
Publication Date:
Research Org.:
Brookhaven National Lab. (BNL), Upton, NY (United States)
Sponsoring Org.:
USDOE Office of Science (SC)
OSTI Identifier:
1119528
Report Number(s):
BNL-102243-2013-IR
DOE Contract Number:
AC02-98CH10886
Resource Type:
Technical Report
Country of Publication:
United States
Language:
English
Subject:
43 PARTICLE ACCELERATORS

Citation Formats

Trbojevic, D., and Courant, E. D. A Standard FODO Lattice with Adjustable Momentum Compaction. United States: N. p., 1997. Web. doi:10.2172/1119528.
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Trbojevic, D., & Courant, E. D. A Standard FODO Lattice with Adjustable Momentum Compaction. United States. doi:10.2172/1119528.
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Trbojevic, D., and Courant, E. D. Mon . "A Standard FODO Lattice with Adjustable Momentum Compaction". United States. doi:10.2172/1119528. https://www.osti.gov/servlets/purl/1119528.
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@article{osti_1119528,
title = {A Standard FODO Lattice with Adjustable Momentum Compaction},
author = {Trbojevic, D. and Courant, E. D.},
abstractNote = {An existing lattice made of identical FODO cells can be modified to have adjustable momentum compaction.},
doi = {10.2172/1119528},
journal = {},
number = ,
volume = ,
place = {United States},
year = {Mon May 12 00:00:00 EDT 1997},
month = {Mon May 12 00:00:00 EDT 1997}
}
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Technical Report:
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DOI:  10.2172/1119528
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    An existing lattice made of identical FODO cells can be modified to have adjustable momentum compaction. The modified lattice consists of repeating superperiods of four FODO cells where every two cells have different horizontal phase advance. In existing FODO cell rings an additional quad bus is required for every two consecutive cells. This allows tuning of the momentum compaction or {gamma}{sub t} could be an imaginary number. A drawback of this modification is relatively large values of the dispersion function (two or three times larger than in the regular FODO cell design).

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    A storage ring with tunable momentum compaction has the advantage in achieving different RMS bunch length with similar RF capacity, which is potentially useful for many applications, such as linear collider damping ring and pre-damping ring where injected beam has a large energy spread and a large transverse emittance. A tunable bunch length also makes the commissioning and fine tuning easier in manipulating the single bunch instabilities. In this paper, a compact ring design based on a supercell is presented, which achieves a tunable momentum compaction while maintaining a large dynamic aperture.

  • At present, the PEP-II bunch length and vertical beta function {beta}*{sub y} at the Interaction Point (IP) are about of the same size. To increase luminosity, it is planned to gradually reduce {beta}*{sub y}. For the maximum effect, bunch length has to be also reduced along with {beta}*{sub y} to minimize luminosity loss caused by the hourglass effect at IP. One of the methods to achieve a smaller bunch length is to reduce momentum compaction factor. This paper discusses a lattice option for the High Energy Ring, where the nominal 60{sup o} cells in four arcs are replaced by 90{supmore » o} cells to reduce momentum compaction factor by 30% and bunch length by 16%. The increased focusing in 90{sup o} cells results in 40% stronger arc quadrupoles and 150% stronger arc sextupoles due to reduced dispersion and larger chromaticity. Tracking simulations predict that dynamic aperture for this lattice will be {ge} 10 times the rms size of a fully coupled beam for a horizontal emittance of 30 nm and {beta}*{sub y} = 1 cm. The lattice modification and results of simulations are presented.« less

  • ; ;
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