LHC optical model and necessary corrections (aperture model, tune, - - PowerPoint PPT Presentation

LHC optical model and necessary corrections (aperture model, tune, β-beat, coupling, chromaticity...)

• M. Aiba, C. Alabau, R. Calaga, J. Cardona,
• O. Dominguez, M. Giovannozzi, S. Fartoukh, V. Kain,
• M. Lamont, E. Mcintosh, R. Miyamoto, G. Mueller,
• S. Redaelli, F. Schmidt, R. Tomás,
• G. Vanbavinckhove, J. Wenninger, S. White and
• F. Zimmermann

LHC beam commissioning workshop - 2010

Rogelio Tom´ as Garc´ ıa LHC

• ptical

model and necessary corrections – p.1/31

Contents

• Effect of precycling (prehistory)
• LHC status (optics and aperture)
• Optics error sources at injection:
• Errors in IR3 and IR7 (warm)
• Triplet errors in IR2 and IR8
• Dipole b2 correction
• IR5 squeeze
• Software needs
• Commissioning needs

Rogelio Tom´ as Garc´ ıa LHC

• ptical

model and necessary corrections – p.2/31

The effect of precycling - Beam 2

• 0.4
• 0.2

0.2 0.4 0.6 5000 10000 15000 20000 25000 ∆β/βy Longitudinal location [m] precycling not precycling

• 0.4
• 0.2

0.2 0.4 ∆β/βx IR1 IR2 IR3 IR4 IR5 IR8 IR6 IR7

Large differences! → Must precycle

Rogelio Tom´ as Garc´ ıa LHC

• ptical

model and necessary corrections – p.3/31

Beam 2, 2008-2009

0.2 0.4 0.6 0.8 1 0.05 0.1 0.15 0.2 0.25 0.3 0.35 0.4 0.45 ∆ β/βy,peak ∆ β/βx,peak Simulations, observations and tolerances LHCB2 2008 450GeV LHCB2 2009 450GeV Measured b2+5units

• Sext. misalignments 2mm

Measured b1 and b2 Tolerances LHCB2 2009 1.18TeV

Injection optics still far from tolerances

Rogelio Tom´ as Garc´ ıa LHC

• ptical

model and necessary corrections – p.4/31

Beam 2, 2008-2009

0.2 0.4 0.6 0.8 1 0.05 0.1 0.15 0.2 0.25 0.3 0.35 0.4 0.45 ∆ β/βy,peak ∆ β/βx,peak Simulations, observations and tolerances LHCB2 2008 450GeV LHCB2 2009 450GeV Measured b2+5units

• Sext. misalignments 2mm

Measured b1 and b2 ? Tolerances LHCB2 2009 1.18TeV

Why the large difference between 450GeV and 1.18TeV?

Rogelio Tom´ as Garc´ ıa LHC

• ptical

model and necessary corrections – p.5/31

LHC optics status summary

Beam 1 Beam 2 Tol. E [TeV] 0.45 1.18 0.45 1.18 ∆βx/βx [%] 35 20 40 15 14 ∆βy/βy [%] 50 16 55 20 16 ∆Dqf

x /Dqf x

[%] 19 11 16 ? 30 ∆Dqd

y /Dqf x

[%] 8 12 11 ? 28 Dispersion is within tolerances even at injection!

Rogelio Tom´ as Garc´ ıa LHC

• ptical

model and necessary corrections – p.6/31

Aperture measurements (IR6 example)

+8σ

• 7σ

Measured closed orbit + 3σ envelope using measured

• ptics and ǫx,n = 3.5µm. 5R6 losses expected, 11R6

losses to be understood.

Rogelio Tom´ as Garc´ ıa LHC

• ptical

model and necessary corrections – p.7/31

Summary of aperture measurements

Rogelio Tom´ as Garc´ ıa LHC

• ptical

model and necessary corrections – p.8/31

Aperture tolerance with measured β-beat

• ✁

• ✁

• Measured

lines at N1=7σ

Beam 1 Traditional values ǫn = 3.75 µm, and CObudget=4mm. Aperture is out of budget due to β-beating

• measured CO and

lower ǫn help

• Rogelio

Tom´ as Garc´ ıa LHC

• ptical

model and necessary corrections – p.9/31

LHC aperture status

• Beam clearance seems to be OK, above or equal

to 7σ.

• Some measured bottlenecks agree with model

predictions using measured β functions.

• Aperture is out of budget due to the large

β-beating, N1 < 7σ even reducing the CObudget to the measured ≈3.2mm peak CO.

• Correcting β-beating is mandatory.

Rogelio Tom´ as Garc´ ıa LHC

• ptical

model and necessary corrections – p.10/31

Error sources @ injection

Estimated impact of sources ordered by size: Beam 1 Beam 2 ∆βx/βx ∆βy/βy ∆βx/βx ∆βy/βy IR3 15 10 15 10 IR7 15 6 12 8 IR2 6 9 6 10 IR8 8 8 8 8

• dip. b2

6 7 5 9

Rogelio Tom´ as Garc´ ıa LHC

• ptical

model and necessary corrections – p.11/31

IR7 local error @ 450GeV & 1.18 TeV

• 0.02
• 0.01

0.01 0.02 0.03 0.04 16400 16600 16800 17000 17200 17400 ∆φx[2π] 1.18 TeV 450 GeV

• 0.02
• 0.01

0.01 0.02 0.03 0.04 16400 16600 16800 17000 17200 17400 ∆φy[2π] s [m] K1L IP7 LHCB1

IR3 and IR7 errors disappear at 1.18 TeV, why?

Rogelio Tom´ as Garc´ ıa LHC

• ptical

model and necessary corrections – p.12/31

Suspects of IR7 and IR3 errors

MQW, courtesy of P. Hagen

• Q6 in IR7 and IR3 are also suspects since they were

not precycled

Rogelio Tom´ as Garc´ ıa LHC

• ptical

model and necessary corrections – p.13/31

IR7 proposed local correction - Beam 1

• 0.02
• 0.01

0.01 0.02 0.03 0.04 0.05 16400 16600 16800 17000 17200 17400 ∆φx[2π] Measurement Q6L-1%, MQWA+3%

• 0.02
• 0.01

0.01 0.02 0.03 0.04 0.05 16400 16600 16800 17000 17200 17400 ∆φy[2π] s [m] K1L IP7 LHCB1

Q6 and MQWA seem to correct IR7 beam 1

Rogelio Tom´ as Garc´ ıa LHC

• ptical

model and necessary corrections – p.14/31

Same IR7 corr for Beam 2

• 0.01

0.01 0.02 0.03 0.04 0.05 0.06 0.07 0.08 22700 22800 22900 23000 23100 23200 23300 23400 23500 23600 ∆φx[2π] Measurement Q6L-1%, MQWA+3%

• 0.02
• 0.01

0.01 0.02 0.03 0.04 0.05 0.06 22700 22800 22900 23000 23100 23200 23300 23400 23500 23600 ∆φy[2π] s [m] K1L IP7 LHCB2

Same correction is not fully satisfactory for beam 2

Rogelio Tom´ as Garc´ ıa LHC

• ptical

model and necessary corrections – p.15/31

What about IR3?

• 0.02
• 0.01

0.01 0.02 0.03 0.04 0.05 0.06 3000 3200 3400 3600 3800 4000 ∆φx[2π] Measurement MQWA+3%

• 0.02
• 0.01

0.01 0.02 0.03 0.04 0.05 0.06 3000 3200 3400 3600 3800 4000 ∆φy[2π] s [m] K1L IP3 LHCB1

Similar correction in IR3 (MQWA+3%) rather effective

Rogelio Tom´ as Garc´ ıa LHC

• ptical

model and necessary corrections – p.16/31

IR3 and IR7 local error summary

• MQWA (main quads) seem to be effective for a

good fraction of the correction

• Q6 also effective to a lesser extent
• The precycling of Q6 should be attempted in

2010 (even if in MD mode)

• The residual errors should be corrected iteratively

with MQWB (the IR3/7 trims)

Rogelio Tom´ as Garc´ ıa LHC

• ptical

model and necessary corrections – p.17/31

Dipole b2 correction - Beam 1

• 0.2
• 0.1

0.1 5000 10000 15000 20000 25000 ∆φy [2π ] s[m] Before b2 correction After b2 correction

• 0.1

0.1 0.2 ∆φx [2π ] IR3 IR4 IR5 IR6 IR7 IR2 IR8 IR1

The magnetic dipole b2 is used to compute the required correction with KQT → Excellent agreement!

Rogelio Tom´ as Garc´ ıa LHC

• ptical

model and necessary corrections – p.18/31

Also from injection tests - Beam 2 arcs8-6

• 6
• 4
• 2

2 4 6 6000 7000 8000 9000 10000 11000 12000 y [mm] Longitudinal location [m]

• 6
• 4
• 2

2 4 6 6000 7000 8000 9000 10000 11000 12000 x [mm] KCS.A67.B2 Exp. No b2, b3 Dipole b2, b3

The magnetic dipole b2 and b3 were also confirmed during sector tests. Congratulations to magnet experts and MAD modelers!

Rogelio Tom´ as Garc´ ıa LHC

• ptical

model and necessary corrections – p.19/31

Predicted IP2 local correction - Beam2

50 100 150 200 250 300 350 400 6000 6200 6400 6600 6800 7000 βx[m] Measurement Design with initial cond ktqx2.l2=-5e-5;ktqx2.r2=7e-5 50 100 150 200 250 300 350 6000 6200 6400 6600 6800 7000 βy[m] s [m] K1L IP2 LHCB2

50/70 units in QX2R/L seemed to correct IR2

Rogelio Tom´ as Garc´ ıa LHC

• ptical

model and necessary corrections – p.20/31

Measured IP2 local correction - Beam2

• 0.04
• 0.03
• 0.02
• 0.01

0.01 0.02 6100 6200 6300 6400 6500 6600 6700 6800 6900 7000 ∆φx[2π]

• 0.04
• 0.03
• 0.02
• 0.01

0.01 0.02 6100 6200 6300 6400 6500 6600 6700 6800 6900 7000 ∆φy[2π] s [m] Before IR2 corr. After IR2 corr. K1L IP2 LHCB2

The measurement confirmed a good correction

Rogelio Tom´ as Garc´ ıa LHC

• ptical

model and necessary corrections – p.21/31

Beam 1 β-beat after b2,IR8,IR2 correct.

• 0.4
• 0.2

0.2 0.4 5000 10000 15000 20000 25000 ∆β/βy Longitudinal location [m] IR8+IR2 corr Baseline

• 0.4
• 0.2

0.2 0.4 ∆β/βx IR3 IR4 IR5 IR6 IR7 IR2 IR8 IR1

Good steps towards full correction but large errors re- main in IR7 (hor.) and IR3 (vert.)

Rogelio Tom´ as Garc´ ıa LHC

• ptical

model and necessary corrections – p.22/31

Squeeze in IR5 - Beam 2, 1.18 TeV

50 100 150 200 250 βx [m] Exps. Models β*=11m β*=9m β*=7m 50 100 150 200 250 16.1 16.2 16.3 16.4 16.5 16.6 16.7 16.8 16.9 βy [m] longitudinal position [km] K1L IP5 LHCB2

Excellent! (see Stefano’s talk for more details)

Rogelio Tom´ as Garc´ ıa LHC

• ptical

model and necessary corrections – p.23/31

β∗ knobs

2.5 3 3.5 4 4.5 5 5.5 6

• 4
• 3
• 2
• 1

1 2 3 4 Beta*(m) Knob Value HorizontalPlane Trimx VerticalPlane Trimx HorizontalPlane Trimy VerticalPlane Trimy

Valididyinterval:+/-20% (~linear)

β∗ knobs were tested without beam... to be validated in 2010 with measurements

Rogelio Tom´ as Garc´ ıa LHC

• ptical

model and necessary corrections – p.24/31

Kick amplitude and BPM noise in 2009

0.2 0.4 0.6 0.8 1 1.2 0.2 0.4 0.6 0.8 1 # of Occurences [x 104] BPM Noise [mm]

Specification

Uncorrelated BPM Noise

Horizontal Vertical 0.2 0.4 0.6 0.8 1 1.2 2 4 6 8 10 # of Occurences [x 104] Kick Amplitude [mm]

Specification

Kick Amplitude

Horizontal Vertical

(MKQ or injection offset)

We need larger kicks, MKA (hardware tested last week!) and/or AC dipole (not tested).

Rogelio Tom´ as Garc´ ıa LHC

• ptical

model and necessary corrections – p.25/31

Software needs

• BPM-bunch synchronization changed between

exps:

• BI expert needs single bunch for this

synchronization

• Could this be automatized and run everyday?
• Kick-bunch synchronization via OASIS usually

takes 30min! Any idea?

• Presently measured optics is made available via a

web page, should this be put in LSA database?

Rogelio Tom´ as Garc´ ıa LHC

• ptical

model and necessary corrections – p.26/31

Commissioning needs

• Dipole b2 correction could be on from day 1
• Shall we try to precycle Q6?
• Aperture kicker and/or AC dipole absolutely

required for 2010.

• After every β-beating correction tunes, coupling,

chromaticity, injection settings and collimators need adjustments.

• The IR3 and IR7 local corrections will require

various shifts and iterations

• IR2 and IR8 seem to be much easier

Rogelio Tom´ as Garc´ ıa LHC

• ptical

model and necessary corrections – p.27/31

Support slides

Rogelio Tom´ as Garc´ ıa LHC

• ptical

model and necessary corrections – p.28/31

Reproducibility - worst case difference

• 0.15
• 0.1
• 0.05

0.05 0.1 0.15 5000 10000 15000 20000 25000 ∆βy/βy (after 4 days, Beam 1) Longitudinal location [m]

≈5% β-beat difference in 4 days. Source very hard to spot with this poor measurement, need 1000 turns

Rogelio Tom´ as Garc´ ıa LHC

• ptical

model and necessary corrections – p.29/31

β-beating during squeeze - Beam 1

• 0.4
• 0.2

0.2 0.4 5000 10000 15000 20000 25000 ∆β/βy Longitudinal location [m] β*=11m β*=7m

• 0.4
• 0.2

0.2 0.4 ∆β/βx IR3 IR4 IR5 IR6 IR7 IR2 IR8 IR1

Rogelio Tom´ as Garc´ ıa LHC

• ptical

model and necessary corrections – p.30/31

β-beating during squeeze - Beam 2

• 0.4
• 0.2

0.2 0.4 5000 10000 15000 20000 25000 ∆β/βy Longitudinal location [m] β*=11m β*=7m

• 0.4
• 0.2

0.2 0.4 ∆β/βx IR1 IR2 IR3 IR4 IR5 IR8 IR6 IR7

Rogelio Tom´ as Garc´ ıa LHC

• ptical

model and necessary corrections – p.31/31