Ir1 and ir5 aperture at 3 5 tev preliminary results
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IR1 and IR5 aperture at 3.5 TeV Preliminary results. S. Redaelli , C. Alabau Pons, R. Assmann , R. Bruce, M. Giovannozzi, G. Müller , F. Schmidt, R. Tomas, J. Wenninger , D. Wollmann Introduction Method for 3.5TeV Measurement results What we had at 450 GeV Preliminary conclusions

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Ir1 and ir5 aperture at 3 5 tev preliminary results

IR1 and IR5 aperture at 3.5 TeVPreliminary results

S. Redaelli, C. Alabau Pons, R. Assmann, R. Bruce, M. Giovannozzi, G. Müller, F. Schmidt, R. Tomas, J. Wenninger, D. Wollmann


Method for 3.5TeV

Measurement results

What we had at 450 GeV

Preliminary conclusions

Acknowledgements: S. Fartoukh, M. Lamont

LHC Studies WG - MG

Proposal for 3 5 tev measurements
Proposal for 3.5 TeV measurements


6 sigma envelope


Unlike at injection, we cannot lose the full beam!

We have to be very careful with damage and quenches, even with pilot beam!

Idea: local bumps in the triplet with safe, blown-up pilot bunch and tertiary collimators to protect the triplet

Even if we planned to work with safe beam, a detailed planning was submitted to rMPPfor approval.

Selective emittance blow-up tested in the MD with the ADT: looks very promising and opens the path for efficient measurements at top energy.

Thanks to ATLAS, CMS: special BCM settings

LHC Studies WG - MG

Example of 3 5 tev measurement
Example of 3.5 TeV measurement

Orbit at TCT and Q2

Procedure for “gentle” measurements:

1. Open TCT by 0.5 sigma (250-320μm in H-V)

2. Increase bump by 0.25 sigma 3. Check relative height of BLM spikes: TCT vs MQX (Q2)

Start from initial settings: TCTs at 11.8 sigmas.

TCT positions [mm]

18.8 σ

18.3 σ

17.8 σ

Q2 losses [Gy/s]

Loss spikes while the orbit is increased, touching TCT or MQX

TCT losses [Gy/s]

LHC Studies WG - MG

Overall measurement timeline
Overall measurement timeline


TCT gaps

Measurements completed in ~ 4h (H+V in IR1+IR5)

LHC Studies WG - MG

Summary of ir1 5 scans preliminary
Summary of IR1/5 scans (preliminary)

Figures quoted in the eLog, from online estimate:http://elogbook/eLogbook/eLogbook.jsp?lgbk=60&date=20110826&shift=1

IR1 - H (Sep) -> 19.8 - 20.3 sigmas

IR1 - V (Xing) -> 18.3 - 18.8 sigmas

IR5 - H (Xing) -> 19.8 - 20.3 sigmas

IR5 - V (Sep) -> > 20.3 sigmas

Resolution:0.5 sigmas from TCT step size

This means that we had to open the TCT by 6.0-7.5 sigmas to “see” the triplet aperture. Present assumptions: 2 sigma retraction.

Effect of bump shape (RBCX contribution) under investigation.

What could we do if these good aperture was confirmed?

Squeeze below 1m with tight collimator settings


Run at 1m with present relaxed collimator settings and 120 μrad crossing

In operation!

LHC Studies WG - MG

2011 injection measurements
2011 injection measurements

Measurements performed at the end of Feb. 2011.

- Essentially, the same geometry as 3.5 TeV was used: additional crossing angles added on top of reference orbit.

- Used a different method to “touch” the aperture: (emittance blow-up + local bump at the triplet).

- Measured absolute aperture and not retraction to TCT.

R. Bruce

LHC Studies WG - MG

Comparison ip5 crossing plane

450 GeV, injection optics, Feb. 2011

3.5TeV, squeezed, Aug.2011

Comparison (IP5, crossing plane)

This is where we saw losses!

LHC Studies WG - MG

Comparison a few numbers in mm
Comparison: a few numbers in mm

ModelBPM (COXing+ ΔCObump)

450 GeV IP5-H (crossing) COXing = 8.0 mm (170 μrad) ΔCObump = 8.3 mm 14. mmnσx σ = 16.0 mm 16. mmAmm = 32.3 mm 30 mm

ModelBPM (COXing+ ΔCObump)

3.5 TeV IP5-H (crossing) COXing = 5.8 mm (120 μrad) ΔCObump = 17.7 mm 24.4 mmnσx σ = 4.8 mm 4.8 mm(nσ= 4)Amm = 28.3 mm 29.2 mm

Mechanical aperture: 28.9 mm (30 mm without tolerance)

PRELIMINARY ANALYSIS. Error analysis under preparation.

Comparison table will be extended to all other available IRs / planes

LHC Studies WG - MG

3 5 tev loss maps at 1m xing 120 rad relaxed collimator settings
3.5 TeV loss maps at 1m,Xing = 120μrad, relaxed collimator settings

Loss maps done with remaining intensity of ~ e9p


Beam 2






Loss maps cannot easily be used to determine the margin TCT to triplet (MP relevant) but clearly the MQX were not exposed to beam halo.

Cleaning looks good. Seen some leakage TCT → MQX for B2, IR1-L.

LHC Studies WG - MG


  • We measured gently the aperture in the triplet region at 3.5 TeV.

    • Triplets in the shade of the TCT

    • 4 planes in 2 IPs: 1 fill, < 5h at top energy

  • Preliminary analysis: indicated a triplet aperture of ~ 18-20 sigmas.

    • Inferred from the retraction of the TCTs that sit at ~ 12 sigmas.

  • Comparison with previous injection measurements show that these figures are consistent with a few millimeters.

  • Triplet aperture compatible with a well-aligned machine, a well centredorbit and a ~ design mechanical aperture (small tolerance).

  • Parasitically tune and coupling were measured during the scans: they might provide information on triplet FQ.

LHC Studies WG - MG