Snowmass 2001

RHIC Interaction Regions:Diagnostics and Correction

Fulvia Pilat

Snowmass, July 18, 2001Joint T1-T5-T9

F.Pilat – RHIC Interaction Regions

OutlineRHIC OverviewIR correction systems: motivation, design (RHIC, LHC, VLHC)RHIC IR’s: layout and configurationIR correction methodsLinear: IR bumps, action-jumpNonlinear: action kick, IR bumps, frequency analysisIR bumps method application to LHCResults for Run 2000Linear: local IR skew correction and global coupling correctionNonlinear: operational determination of IR nonlinear termsRun 2001: plans for machine development/ beam studiesBeam experiments for future hadron colliders


12:00 o’clock

2:00 o’clock

4:00 o’clock6:00 o’clock

8:00 o’clock

PHOBOS10:00 o’clock

BRAHMS

STARPHENIX

RHIC

AGS

LINACBOOSTER

TANDEMS

Pol. Proton Source

High Int. Proton Source Design Parameters:Beam Energy = 100 GeV/u No. Bunches = 57 No. Ions /Bunch = 1 109

Tstore = 10 hours

Lave = 2 1026 cm-2 sec-1

9 GeV/uQ = +79

1 MeV/uQ = +32

HEP/NP

g-2U-line

BAF (NASA)

RHIC Complex


RHIC Run 2000 and 2001

Run 2000May –July: commissioningAugust-September: operation and beam studiesReached 10% of design luminosity

Run 2001Started in MayMay-July: start-up and commissioningof new systems (PS, transition, PLL, etc.)End July-September: operations with Au-Au and machine development (MD)October-November : polarized p commissioning and operation (MD ?)December-January: Au-Au operations and MD program

Goal: design luminosity


IR Correction systemsMotivation: local correction of linear errors (coupling, gradient)Local correction of nonlinear errors ( IR magnets field errors)Beta squeeze, crossing angleBeam control, luminosity

Design:Multi-layer corrector packages installed next to IR triplet quadrupolesTypically, dipole dodecapoleIndependently powered RHIC LHC VLHC


LHC inner triplet - correctors

MQXA MQXB MQXB MQXA

MCBXA

MQSXA

MCBX

MCBX

BPM

BPM

LMQXB LMQXC LMQXA

LQXB LQXC LQXA

To IP

“Q3” “Q2” “Q1”

MCBX: b1 a1MCBX: b1 a1MQSXA: a2 a3 a4 b4 MCBXA: a1 b1 b3 b6Optimization process:Magnet design – correction system


IR Correction – VLHC Stage 2

D1A D1B

Q1a

Q2a

D2

IP

20m

12.1m 6m 22m

5.5m2m

16T 12T

400T/m 600T/m

12T

Q1b

Q2b

600T/m 600T/m

12.4m 12.4m7.9m 7.9m

3m

3m

a0a1a2a3

b0b2b3b5

BPMIR correctorPackage (skew)

IR correctorPackage

3m


RHIC IR’s - layout

6 o’clock IR8 o’clock IR:Dipole correctorsSkew quadrupolesNonlinear

Other IR’s:dipole correctorsSkew quadrupoles(nonlinear layersexist but no PSyet)


Run 2000 – IR correction linear

IR bump method Action-jump method

Determine local IR skew quadrupole correction strenghts (Cardona, Ptitsyn, Pilat)


RHIC Coupling correction

Global coupling correction: 3 families Combine 2 to get 2 orthogonal knobs(RHIC can be decoupled only with the families)Local correction of IR effects (alignment rollerror) is constant on the ramp, while globalcorrection changes on the ramp (orientationof vector varies ~10%)

Run2000

Run2001


IR Correction - linearFrom Run 2000 IR bump data and action jump data, we have predictions for the 12 IR skew quad correctors in each ring The results from the 2 methods agree (5-10%)The predicted values from the 2000 data analysis agree with the corrector settings found operationally in 2001 The residual coupling in the machine (not arising from the IR triplets) is corrected with skew quadrupole families by correcting the coupling resonance (minimum tune separation)

Configuration 2001 (blue ring) Q(min)Uncorrected 0.009Local correction IR8, IR10,IR2 0.019Local correction in all IR’s 0.008Local correction + global correction

0.0005 (tune meter resolution)


IR nonlinear correction methodsdead-reckoning: action-kick minimization (Wei)

order-by-order prescription, assumes field errors known(off-line code – “IR filter”- to set corrector strengths)

operational: beam based + off-line analysis IR bumps: measure and fit observables vs. bump amplitude:(Koutchouk) rms orbit (BPM’s, linear, sextupole)(Ptitsyn, Pilat) tunes (Tune Meter, up to dodecapole)

(tune spread) (Schottky, octupole, dodecapole?) frequency analysis: “better FFT” detect and correct nonlinear(Schmidt) sidebandsSUSSIX


IR bumps method - principleClosed local orbit bump (triplet)Observable as function of bump amplitude:rms orbit outside the bumpz=(x,y) cn=(an,bn) zba=bump amplitude

dsRzc

BB

Qzcfrmsz nba

nzN

z

arczban 1)(

sin22),()(

The orbit perturbation depends in the plane of the bump (H,V)And the parity of the multipole order

tune shiftArises from normal gradients (DQ) or repelling effect of linear coupling (measured by c)

dsRz

cBBnzcgQ n

nba

nN

ban 1

2

41),(

dseRz

aBBnzchc yxi

n

nba

nyxN

ban)(

1

2

21),(

Selection of one or the other effect depends on the plane of the bump, whether the multipoleis skew or normal and on the parity of the multipole order


IR bumps: simulation, performance

Use MAD to compute orbit and tune response to H and V orbit bumps in theLHC IP5, assuming:0.1% gradient error (/~20%), 1 mrad roll (c~0.04)Multipoles set to 10 units in Q2B.

Orbit response:(assuming 20 data points)

Tune response:Assuming 20 measurements and tune resolutionof 2 10-4 resolve multipoles up to b6 (dodecapole)

DC offset of BPM can be eliminated by subtracting 2 orbits

Accuracy can be improved by increasing the number of measurements

Perturbation BPM resolutionroll 0.1 mrad 15 m rmsb3 = 7.6 10-4 8 m rmsb4 = 7.2 10-4 3.5 m rms


Run 2000–IR correction nonlinear

RHIC IR bumps – beam experimentBump data at IR2, IR6, IR8, blue & yellowMostly H bumps, some V bumpsTune resolution run 2000: 0.001Bump amplitude typically to 6Orbit linear, sextupoleTune 5th order polynomial

Tune resolution 2001 (0.0002) decapole dodecapole? 2001: automatic bump set-up

triplet

b3 a3 b4 b5 a5 b6

YO5 0.94 -0.55 0.03 -0.08 0.11 -0.01YI6 -0.95 0.14 0.36 0.03 -0.06 -0.03YI7 1.01 -0.22 0.81 0.36 -0.17 -0.15YO8 3.81 -0.47 -1.85 0.06YO1 0.32 -0.14 0 0YO2 1.51 0.76 -0.75 -0.21


Run 2001 – Machine Development

Plan for RUN 2001:Scheduled MD time every week: 12h - wednesdayWeekly meetings – friday – to discuss plan and resultsWeekly report to “time meetings” – tuesday

MD coordinator – F.PilatMD starts when RHIC in operation mode – end July

(first collisions at 100 GeV/u Monday this week! )Program to continue till end of the run ~end January


MD Program 2001

IR studies (V.Ptitsyn)IBS, Nonlinear, Beam-Beam (W.Fischer)Background, Collimation, Luminosity (A.Drees)Optics, AC Dipole (M.Bai)Impedance (S-Y Zhang)Longitudinal/RF studies (M.Brennan)Transition studies (J.Kewisch)Deuterons in AGS/RHIC (K.Gardner)

www.agsrhichome.bnl.gov/AP/RHIC2001/BeamStudies/index.html


Collaborative beam studiesCollaborations during Run 2000:

IR studies: J-P. Koutchouk, CERN T.Sen, FNALNonlinear studies: F.Schmidt, CERNInstrumentation: H.Schmickler, CERNOperations: M.Lamont, CERN

During Run 2001 (and 2002)Continue existing collaborationsExperiment plan for future hadron colliders discussed at Snowmass:RHIC, FNAL, HERA,….LHC?Phase 1: included in machine development plansPhase 2: formally approved beam experiments with collaborating institutions

Beam experiments as a test bench for GAN ?


SummaryUse of IR correction system started at RHIC during Run 2000Local IR decoupling has been demostrated

integrates with the global coupling correctionOperational identification of IR nonlinear errors is possible (IR bumps technique)Experiment work will continue during MD time in Run 2001Collaborative beam experiments are discussed to validate future hadron collider design and performance

Snowmass 2001

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