Alex Bogacz

Operated by the Jefferson Science Associates for the U.S. Depart. Of Energy

Thomas Jefferson National Accelerator Facility ISS Workshop, UC Irvine, August 21, 2006.

Alex Bogacz, Acceleration in RLAs – Design Choices

Alex Bogacz

‘Racetrack’ vs ‘Dogbone’ configuration

multi-pass linacs focusing

orbit separation

simultaneous acceleration of both + - species

10 GeV Two-step-Dogbone RLA

Quadrupole focusing scheme – Triplet vs FODO lattices

multi-pass linac

matching to the Arcs

vertical injection double-chicane

Acceleration in RLAs – Design Choices




‘Racetrack’ vs ‘Dogbone’ RLA (n-pass)

E/2

total arc length: (2n - 1) R

E/2

E

n arcsn - 1 arcs

E0

E0 + n E

total arc length: 2n (7/6) R

n/2 dropletsn/2 droplets

E0 + (n + ½) E

E0

mis- focusing factor: 1 + (n-1) E/E0

mis- focusing factor: 1 + n E/E0

orbit separation factor: [E0 + n E]/[E0 + (n-1) E] ≃ n/n-1

orbit separation factor: [E0 + (n+½) E]/[E0 + (n-2+½) E] ≃ n/n-2




‘Racetrack’ vs ‘Dogbone’ RLA (both + and - species )




10 GeV Two-step-Dogbone RLA

0.9 GeV to 3.0 GeV 3.0 GeV to 10 GeV3.33… ext/inj energy ratio

0.9 GeV0.2 GeV

1.5 GeV to 5.0 GeV

0.6 GeV/pass3 GeV

2 GeV/pass10 GeV




Injection double-chicane

900

Wed Apr 26 00:28:03 2006 OptiM - MAIN: - D:\ISS_dogbone\Chicane\Chicane_dogleg.opt

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FODO vs Triplet focusing structure

FODO

The same lengthThe same phase advance per cell (x= 900 = y)

Triplet

Advantages:

much weaker quads (~3 times)shorter quads (total)easier chromaticity correction

120

Tue Dec 06 15:45:30 2005 OptiM - MAIN: - D:\ELIC\Figure-8\Triplet\cell_in.opt

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Advantages:

longer straight sectionssmaller vertical beta-functionuniform variation of betas and

dispersion




Multipass linac - Triplet vs FODO focusing (900 phase adv/cell)

1-pass

2-pass

192.80

Sun Aug 20 23:59:26 2006 OptiM - MAIN: - D:\RLA_linacs\FODO\90deg\NL_1.opt

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3-pass

192.80

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194.70

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194.70


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194.70


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Mon Aug 21 00:32:19 2006 OptiM - MAIN: - D:\RLA_linacs\FODO\90deg\NL_3.opt

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Straight-Arc Periodic transition

1170

Wed Nov 30 01:22:41 2005 OptiM - MAIN: - D:\ELIC\Figure-8\tran.opt

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Triplet

FODO

1080

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Summary

‘Dogbone’ RLA – preferred configuration (compared to the ‘Racetrack’)

better orbir separation for higher passes

more efficient use of the rf (extra half-pass)

offers symmetric solution for simultaneous acceleration of + and -

FODO lattice more favorable (compared to the triplet) to accommodate large number

of passes

uniform phase advance decrease in both planes

smaller variation of Twiss function – easier match to the Arcs

allows to maintain 900 phase advance per cell for lowest passes

Proposed 10 GeV two-step-dogbone RLA (30 mm rad acceptance)

3.0-10GeV ‘dogbone’ with 400MHz SRF?

Needed: front-to-end simulation, magnet error/misalignment sensitivities etc.

Alex Bogacz

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