Overview Run-6 - RHIC Overview Run-6 - RHIC

Vadim Ptitsyn

C-AD, BNL

RHIC Spin Workshop 2006

V.Ptitsyn

RHIC Run-6 TimelineRHIC Run-6 Timeline

1 Feb – Start of the Run-6. Start of the cooldown to liquid He temperatures. 12 Feb - End of cooldown and PS tests 5 Mar – Start of the 100 GeV Physics Run. Participating experiments: STAR and PHENIX. PHENIX – radial pol ; STAR – long pol 6 Apr – PHENIX – radial pol ; STAR – vertical pol 14 April –21 April – unscheduled shutdown (investigation of electric accident) 26 Apr – PHENIX – longitudal pol; STAR – vertical pol 10 May – PHENIX – longitudal pol; STAR – longitudinal pol 5 Jun – End of 100 GeV run. (12 weeks total ) 5 Jun-6 Jun, 11 GeV accelerator development 6 Jun – Start of 31.2 GeV Physics Run. Participating experiments: STAR, PHENIX and BRAHMS PHENIX – longitudal pol; STAR and BRAHMS– vertical pol 20 Jun - End of 31.2 GeV Run. (Two weeks total) 20 Jun – 26 Jun. 250 GeV accelerator development 26 Jun - 30 Jun warm-up to liquid N temperatures. 30 Jun - End of Run-6. (21.2 weeks of cryo operation)

RHIC Spin Workshop 2006

V.Ptitsyn

Physics run lattices Physics run lattices

IP6 IP8 IP10 IP12 IP2 IP4

Injection 10 10 10 10 10 10

Store, 100 GeV 1 1 10 10 10 10

Store, 31.2 GeV 3 3 10 10 3 10

Lattice modifications:- minimized excursion of dispersion function in IR6 and IR8 in the store at 100GeV

- decreased gamma_t lattice at the injection

Working points: (0.72-0.73) box at the injection; (0.68-0.695) box at the storeTune swing done: 100GeV: at the very end of the acceleration, but before final beta-squeeze part of the ramp

31.2GeV: right before the last stone of the ramp

Beta* configuration (in meters):

RHIC Spin Workshop 2006

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Polarized protons performance at 100 Polarized protons performance at 100 GeV (last three runs)GeV (last three runs)

Parameter Unit 2004 20052005 20062006

No. of bunches -- 56 106106 111111

 bunch intensity 1011 0.7 0.90.9 1.351.35

* m 1 1 1  1 1 

emittance mm mrad 18 2828 1818

peak luminosity 1030cm-2s-1 6 1010 3535

average luminosity 1030cm-2s-1 4 6 6  20 20 

collision points -- 4 33 22

time in store % 41 5656 4646

average polarization, store

% 46 4747   65%65%

Luminosity gain in run-6:

2.2 X 1.5 = 3.3

Increased bunch intensity Improved emittance control

AGS cold snake:polarization

Reduced number of collision points

RHIC Spin Workshop 2006

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Integrated luminosity; 100 GeV runIntegrated luminosity; 100 GeV run

Run6 100 x 100 GeV pp Integrated Luminosity (Final Delivered) for Physics

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RHIC Spin Workshop 2006

V.Ptitsyn

Average integrated luminosity per store Average integrated luminosity per store hour and Time in storehour and Time in store

8 weeks luminosity improvement period

Considerable amount of down time in the middle and at the end of the run

Luminosity slides at the end of the run due to longer stores

RHIC Spin Workshop 2006

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Golden store #7909 of 100 GeV runGolden store #7909 of 100 GeV runL

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osity

RHIC Spin Workshop 2006

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polarization for Run 6, 100x 100 GeV - final

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Polarization during 100 GeV runPolarization during 100 GeV run

RHIC Spin Workshop 2006

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100 GeV run: Luminosities and 100 GeV run: Luminosities and transverse emittancestransverse emittances

Improved transverse emittance control was important item at this run

During the run the improvements to achieve smaller transverse emittance were done both in the injectors and in the RHIC:•Transverse scraping in Booster•Strict control of emittance from AGS (golden values) •appropriate choice of working point (to avoid coherent beam-beam)•keeping bunch length long enough

W.Fischer

RHIC Spin Workshop 2006

V.Ptitsyn

Transverse emittanceTransverse emittance Run-5 emittance

troubles: Larger emittance with

larger number of bunches

Larger emittance from AGS on several fills

In Run-6 those problems were avoided

Helped by vaccuum system improvements:

additional NEG pipe coating (180m) added between the runs

upgrade in cold region vaccuum

S.Y.Zhang

RHIC Spin Workshop 2006

V.Ptitsyn

Integrated luminosity; 31.2 GeV runIntegrated luminosity; 31.2 GeV run

Run6 RHIC pp Integrated Luminosity for Physics (Final)31.2 x 31.2 GeV

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STARPHENIXBRAHMSMinMaxPoly. (Min)Poly. (Max)

RHIC Spin Workshop 2006

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Major operation achievementsMajor operation achievements Successful application of tune/decoupling feedback for the initial ramp

development. Fast collimation. Regular orbit correction at the beginning of the store (before the

cogging) to provide the store reproducibility against 24h orbit variation. IR nonlinear corrections: used not only at the store but also on the ramp

(after the beta-squeeze). 2/3 resonance correction Successful demonstration of “quad pumping” technique to provide better

AGS-to-RHIC longitudinal emittance matching. Unfortunately, could not be effectively used because of the transverse emittance deterioration.

Developed Beam Transfer Function measurement diagnostic. Rotator reconfiguration (done 5 times during the run). Takes 8h + 2-3 stores.

RHIC Spin Workshop 2006

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Factors limiting machine performanceFactors limiting machine performance

Store lifetime: Qx=2/3 resonance beam-beam effects large momentum spread

Factors affecting transverse emittance: small longitudinal emittance and higher beam intensity (enhanced electron

cloud effect) emittance increase on the ramp (?)

Deterioration of ramp transmission with the beam intensity Beam oscillations with parasitic frequencies 10Hz, 60Hz,

…

(coming from cryo and power supply systems)

RHIC Spin Workshop 2006

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Further plansFurther plans Christoph Montag is the Run coordinator for next polarized proton run. Goal: doubling the luminosity, by bunch intensity increase and increased time in store

RHIC Spin Workshop 2006

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Luminosity improvement factors for Luminosity improvement factors for next runnext run

Nonlinear chromaticity correction 10Hz IR orbit feedback 2/3 resonance compensation New working point test, ~(0.92;0.93) Additional NEG pipes (~45m)

Reliability of various machine systems is seriously addressed in this shutdown.

In more remote plans the application of new 9.3Mhz RF cavity system is considered (M.Brennan).

This should allow for smaller longitudinal emittance and smaller bunch length in the store, but long enough bunch length at the injection.

RHIC Spin Workshop 2006

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ConclusionsConclusions

On accelerator part we believe the run was quite successful. Good side: Luminosity goals are achieved. Improved machine

parameters (beam intensities, emittances, polarization). Bad side: Machine reliability problems. Goal for the time in store was

not achieved.

Continue go forward. For next run: Further luminosity improvements (by factor 2). Improved machine reliability