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RHIC BBLR design and new long-range beam-beam measurement

Wolfram FischerR. Calaga, BNL, T. Sen, FNAL,

U. Dorda, J.-P. Koutchouk, F. Zimmermann, CERN

LARP Collaboration Meeting, Berkeley, 28 April 2006

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Content

• Long-range measurements in RHIC– At injection – 23.8 GeV protons– At store – 100 GeV protons

• Compensator design for RHIC– Location– Strength– Wire temperature– Positioning range and accuracy– Power supply

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RHIC Interaction Region

DX IP DX

9.8 m

13.5 m15.7 m52.4 ns

45.0 ns32.7 ns

5.1 ns bunch length 1.52 m BPM(x,y)

BPM(x,y)

Long-rangeinteractions

with 360 bunches

Long-range interactions with 180 bunches

• LRBB important effect in LHC, under investigation in LARP• With >120 bunches cannot avoid long-range beam-beam interactions (eRHIC)• RHIC is a good test bed for a wire compensator (more difficult in Tevatron)

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RHIC BBLR design – locations

long-ranginteraction(vertical)

long-rangecompensation

(up)

long-rangecompensation

(down)

x,y = 6 deg (* = 1m)

RHIC Sector 5

IP6

yo5

bi5

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Long-range beam-beam effect at injection

Collision at s = 10.6 m, Blue beam moved verticallyTunes B (0.739,0.727) Y (0.727,0.738)

Y: attempt to improve lifetime, small changes in (Qx,Qy)

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At injection – lifetime versus separation

SPS : 5ms (d/)5 [measured 11/09/04]

Tevatron: ~ d3 [reported in F. Zimmermann, LTC 11/24/04]

RHIC : ~ d4 or d2 [measured 04/28/05, scan 4]

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Long-range at store

DX IP DX

9.8 m

13.5 m15.7 m52.4 ns

45.0 ns32.7 ns

* = 1m large separations possible (>40) effect on Q, Q small

* = 100m only smaller separations ~8(needs to be explored) effect on Q, Q large

20

2 y

rNQ yb

y

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RHIC long-range experiments in 2006

Tune shift due to vertical separation y:

20

2 y

rNQ yb

y

2005 2006 (1) 2006 (2)

y [m] 20 100 1

26 107 107

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Measurements in 2006 (1)

y = 100m E = 100 GeV Nb 1.51011

Tunes: (0.687,0.685) Blue (0.690,0.695) YellowSingle Blue bunch interacting with single Yellow bunch

• Beam lifetime responds to vertical separation• But vertical separation 4

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Measurements in 2006 (2)

y = 1m E = 100 GeV Nb 1.51011

Tunes: (0.694,0.683) Blue (0.693,0.686) YellowSingle Blue bunch interacting with single Yellow bunch

• No beam lifetime changes from vertical separation (lifetime changes above are from tune changes due to orbit changes)

• But small *

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Further Measurements in 2006

• Beam lifetime changes observed at nominal long-range interaction point with separations 4

• Need to explore vertical separation at nominal long-range interaction point

• Need to increase sensitivity of beam loss measurement (more interacting bunches?, introduce other nonlinearities?, use experimental background signals?)

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RHIC long-range beam-beam compensator design

• 1 unit in each ring, side-by-side• vertically movable (wire in shadow of adjacent beam pipe when not in use)

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RHIC long-range beam-beam compensator design

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RHIC long-range beam-beam compensator design

3 air cooled heat sinks keep T< 15K

Loop at end reduces mechanicalstress on ceramic feedthrough

Strong-back to reduce sagging

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Summary

• Long-range experiments at store still being refined– Best observable not yet defined– Vertical separation range not fully explored– May need to introduce additional nonlinearity

• Long-range compensator design completed

• Construction under way

• Plan to install in summer 2006

• Discussions about pulsed operation under way