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

RHIC BBLR design and new long-range beam-beam measurement. Wolfram Fischer R. Calaga, BNL, T. Sen, FNAL, U. Dorda, J.-P. Koutchouk, F. Zimmermann, CERN LARP Collaboration Meeting, Berkeley, 28 April 2006. Content. Long-range measurements in RHIC At injection – 23.8 GeV protons

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

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  1. 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

  2. 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

  3. 52.4 ns 15.7 m 45.0 ns 13.5 m 32.7 ns 9.8 m DX IP DX 5.1 ns bunch length 1.52 m RHIC Interaction Region • 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) BPM(x,y) BPM(x,y) Long-rangeinteractions with 360 bunches Long-range interactions with 180 bunches

  4. RHIC BBLR design – locations long-ranginteraction(vertical) long-rangecompensation(up) RHIC Sector 5 bi5 Dfx,y = 6 deg (b* = 1m) IP6 yo5 long-rangecompensation(down)

  5. Y: attempt to improve lifetime, small changes in (Qx,Qy) Long-range beam-beam effect at injection Collision at s = 10.6 m, Blue beam moved vertically Tunes B (0.739,0.727) Y (0.727,0.738)

  6. At injection – lifetime versus separation SPS : t 5ms (d/s)5 [measured 11/09/04] Tevatron: t ~ d3[reported in F. Zimmermann, LTC 11/24/04] RHIC : t~ d4 ord2 [measured 04/28/05, scan 4]

  7. 52.4 ns 15.7 m 45.0 ns 13.5 m 32.7 ns 9.8 m DX IP DX Long-range at store b* = 100m only smaller separations ~8s(needs to be explored) effect on Q, DQ large b* = 1m large separations possible (>40s) effect on Q, DQ small

  8. RHIC long-range experiments in 2006 Tune shift due to vertical separation y:

  9. Measurements in 2006 (1) by = 100m E = 100 GeV Nb 1.51011 Tunes: (0.687,0.685) Blue (0.690,0.695) Yellow Single Blue bunch interacting with single Yellow bunch • Beam lifetime responds to vertical separation • But vertical separation  4s

  10. Measurements in 2006 (2) by = 1m E = 100 GeV Nb 1.51011 Tunes: (0.694,0.683) Blue (0.693,0.686) Yellow Single 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 b*

  11. Further Measurements in 2006 • Beam lifetime changes observed at nominal long-range interaction point with separations  4s • 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?)

  12. 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)

  13. RHIC long-range beam-beam compensator design

  14. RHIC long-range beam-beam compensator design 3 air cooled heat sinks keep DT< 15K Loop at end reduces mechanicalstress on ceramic feedthrough Strong-back to reduce sagging

  15. 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

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