Stefano Redaelli, CERN, BE-ABP for the Collimation Project and HL-LHC-WP5 teams The LHC Collimation...

Stefano Redaelli, CERN, BE-ABPfor the Collimation Project and HL-LHC-WP5 teams

The LHC Collimation

Baseline for HL-LHC

3rd Joint HiLumi LHC-LARP Annual MeetingNovember 11th-15th, 2013

Daresbury Laboratory - Warrington, UK

The HiLumi LHC Design Study is included in the High Luminosity LHC project and is partly funded by the European Commission within the Framework Programme 7 Capacities Specific Programme, Grant Agreement 284404.

S. Redaelli, 3rd HiLumi meeting 12/11/2013 2

Outline

Introduction

Where we are (140MJ@4TeV, 60cm β*)

OP feedback and upgrade plans

Advanced collimator concepts

Conclusions


Acknowledgements

B. Salvachua, R. Bruce and ABP collimation teamR. Losito, A. Lechner, F. Cerutti for the EN-STI team

G. Stancari, A. Valishev (FNAL)A. Bertarelli (EN-MME)T. Markiewicz (SLAC),

W. Scandale, D. Mirarchi (crystal studies)G.Arduini, O. Bruning, L. Rossi

R. Appleby (Manchester)

Core collimation team in the LHC accelerator physics group: R. Bruce, M. Cauchi, L. Lari, D. Mirarchi, E. Quaranta,M. Salvachua, A. Rossi, A. Marsili, G. Valentino.People who have recently left the team: R. Assmann, D. Wollmann, D. Deboy

Many thanks to R. Assmann!


Introduction

Superconducting coil: T = 1.9 K, quench limit

~ 15-50mJ/cm3

LHC 2012: 145 MJLHC design: 360 MJ

HL-LHC: 500MJ!

Factor 9.7 x 10 9

Aperture: r = 17/22 mm

LHC “Run 1” 2010-2013: No quench with

circulating beam, with stored energies up

to 70 times of previous state-of-the-art!


LHC collimation layout

Picture by C. Bracco

Two warm cleaning insertions, 3 collimation planes

IR3: Momentum cleaning1 primary (H)4 secondary (H)4 shower abs. (H,V)

IR7: Betatron cleaning3 primary (H,V,S)11 secondary (H,V,S)5 shower abs. (H,V)

Local cleaning at triplets8 tertiary (2 per IP)

Passive absorbers for warm magnets

Physics debris absorbers

Transfer lines (13 collimators)Injection and dump protection (10)

Total of 108 collimators (100 movable).Two jaws (4 motors) per collimator!

Momentumcleaning

Betatroncleaning


Collimator gaps in 2012

Transverse cuts from H, V and S primary collimators in IR7

3σ beam envelope

2012: achieved the our design 7 TeV primary collimator setting!Secondary collimator retraction still above nominal (~2.5σ retraction instead than 1σ).Possible limitations: impedance and OP efficiency (more frequent alignments).

60 cm flat active length, gap = ± 1.05 mmσv = 250 microns!

L. Gentini

Vertical primary collimators: 2012 settings

1 pound


Collimation cleaning at 4 TeV (β*=60cm)

Off-momentumDump

TCTs

TCTsTCTs

TCTs

Betatron

1/10000 0.00001

0.000001

Beam 1

Highest COLD loss location: efficiency of > 99.99% ! Most of the ring actually > 99.999%

B. Salvachua

Cle

anin

g in

effic

ienc

y [B

LM/B

LMtc

p]

Cleaning defined here as:


Stability of cleaning

Excellent stability achieved with 1 align-ment per year in IR3/6/7 (2x30 devices).

New alignments are only repeated for new physics configurations(it remains crucial to be efficient!)

PhD by G. Valentino: average alignment ➙time < 5 min per collimator using the BLMs.

B. Salvachua

Setup time per collimator (2010-2012)

Setup time per collimator (2010-2012)

G. Valentino

p-p runsp-p runs p-Pb/Pb-p runsp-Pb/Pb-p runs


Outline

Introduction




Conclusions


Why we need a collimation upgrade?

LHC points

Cleaning efficiency 3, 7

Collimator impedance 3, 7

Operational improvements, β* all

Collimation in experiments (debris cleaning) 1, 2, 5, 8

Halo control mechanisms 4

Activation, full remote handling all

Collimator lifetime, consolidation all

Collimation cleaning not enough to define the LHC performance: beam lifetime and quench limits at 7 TeV must be must be understood.

Other important aspects: impedance contribution, settings hierarchy and β* reach.

Physics debris collimation: high-luminosity experiments for protons + ion operation.

Cannot cover all the topics - more focus on

aspects covered by HiLumi-WP5 + US-LARP.

Relying on many companion talks at this WS.


Minimum beam lifetime in 2012Beam intensity versus time Minimum (assumed)

beam lifetime Quench limit of SC magnets

Collimation cleaning at limiting cold location

Beam lifetime gives the loss rate on collimators. Cleaning η gives the peak losses in magnets. Collimator design: 500 KW!

SQUEEZESQUEEZE

ADJUSTADJUST

1 hour1 hour

1 hour1 hour

2012: Minimum lifetime with gaps equiv. to 7 TeV: 0.2 - 1 hour

Bea

m li

feti

me

[ h

]

B. Salvachua

See talk by E. Métral: to what extend this depends on collimators?


Collimation quench test

11 Gy/s at the TCP.B6R7.B2 in IR7 for a peak loss up to 1050 kW

Beam 2

Achieved controlled losses of 5.8MJ, about 3 Tevatron full beams, in 15 s.

Peak loss up to 1.05 MW, exceeding assumed quench limits by more than a

factor 3 without quenching!

Major effort undertaken to perform in Feb. 2012 quench tests with beam in operational

conditions.Unfortunately, not possible with ion beams...

B. Salvachua

Ongoing work on different CERN working

groups to understand this in detail.

E. Skordis (fluka team)


Predicted intensity reach from cleaning

Consider minimum lifetime of 0.2 h based on the 2012 experience- Perhaps pessimistic, but ~10% of fills reached τb<0.5-1h!- Reviewers felt that it could get worse (25ns vs 50ns, higher E, larger

impedance)

Different models to scale losses to 6.5 TeV: Intensity reach from proton cleaning in IR7 is 3 to 6 times the nominal LHC (3.2x1014p). Less margin at 7 TeV (different for 2 available quench models).HL-LHC intensity goal reduce this window by a factor ~2.

For more than a factor 2 above LHC design, we have to worry also about collimator robustness!

We might have to set BLM thresholds to protect the collimators!

Ions: ALICE luminosity upgrade target is at least a factor 2 above quench limits. Same limitations apply for IR1 and IR5 that have less priority for ion runs.

No additional limitations in IR1/5 until LS3 from physics debris thanks to the use of 3 TCL collimators.Expect the same result for HiLumi, but need to prove this with final IR layouts.Backup slide in case more details are needed. See also talk by L.Esposito.


DS collimation: requirements by IR

Until HL-LHC (before LS3)[L=2.5x1034cm-2s-1, Itot=3.2x1014p]

HL-LHC era (after LS3)(L=5x1034cm-2s-1, Itot=6.2x1014p)

Protons Ions Protons Ions

IR7 Betatron cleaning Needed?(unlikely)

Needed?(unlikely)

NeededTBC (ATS?)

Needed?

IR3Momentum

cleaningNot needed Not needed Not needed Not needed

IR1/5 ATLAS/CMS Not needed NeededNeeded?(unlikely) Needed

IR2 ALICE Not needed Needed Not neededNeeded

IR8 LHCb Not needed Not operating Not needed Not operating

Goal for the collimation project: have a solution available to address already in

LS2 possible cleaning limitations revealed by the post-LS1 operation.

Larger uncertainties for HL-LHC era, but more time to decide on DS collimation!

Uncertainty on quench limits and performance, solved in 2015.

Can we have 11 T dipoles in time? Do we need to consider alternative

layouts (moving magnets)?

Local collimation in DS addresses successfully limitations in all IRs!


Collimation review outcome

https://indico.cern.ch/event/251588

External review panel:Mike Seidel (PSI, Chair), Giorgio Apollinari (FNAL), Wolfram Fischer (BNL), Marzio Nessi (ATLAS), Rudiger Schmidt (CERN/ESS), Carsten Omet (GSI).

Main outcome on DS collimation:Due to the uncertainties on the extrapolations of beam lifetime and quench limits at 7 TeV, “The committee strongly encourages the development and prototyping of one 11 T (5.5 m) dipole magnet, and the cryogenic bypass collimator unit. … Build at least 4 units (1 unit consists of 2 magnets + bypass + collimator) since this would cover 2 possible cases…”Additionally: support for reduced impedance collimators and hollow elens works!

The review panel recognized that DS collimation:- is needed for ions in IR2/1/5, already in LS2 (ALICE upgrade).- is probably not needed in LS2 but we cannot guarantee that at this stage.- is certainly beneficial for the HL-LHC era (ATS optics). - this technology will be clearly useful for the HL-LHC era Recommendation to work hard to achieve a minimum of 4 by LS2!


Progress towards final layouts

R. Bruce

Finalized layouts and lattices for IR2 and IR7 (IR1/5 ongoing) with 11 T magnets.

Massive simulation campaigns (tracking + energy deposition) to understand the cleaning improvement and to determine key collimator parameters (length and material) specification for load cases are essentially ready.➙

Updated collimator design taking new constraints into account.

Provided inputs for the ongoing detailed integration studies.

Starting iteration with WP11 for studying quench limits and magnet protection.

This is part of the important HiLumi WP5 activity on the LHC collimation that will be discussed in details in the parallel WP5 section!

Beam

Improved design based on 80 cm length, EN-MEE


More pictures on DS collimators

Lot of preparatory work done in preparation of the 2011 baseline solution base on moving magnets. Major re-design and integration work is needed, though.

EN-MME,TE-MSC

M. Karppinen for WP11


New collimator materials

Main goal: reduce impedance of IR7 (and IR3) collimators, representing 90% of LHC impedance at top energy.

See talks by E. Métral and N. Mounet for motivation!

More robust tertiary collimators, might allow to push further beta*

All new collimators will used improved mechanical design with integrated BPMS.

LHC points

Cleaning efficiency 3, 7

Collimator impedance 3, 7

Operational improvements, β* all

Collimation in experiments (debris cleaning) 1, 2, 5, 8

Halo control mechanisms 4

Activation, full remote handling all

Collimator lifetime, consolidation all


Gain from new collimators

N. Mounet

The present collimators contribute to about 90% of the total machine impedance!The collimation contribution is reduced to 10 % if we consider a Mo coding (example here: Mo-Gr jaw coated by Mo).

This is considered as a main show stopper to achieve the HL-LHC high intensity goal!


TCTP prototype assembly

Timeline for new secondary collimators

Our ambitious plan: - Build a machine-ready prototype for installation in the Christmas stop 2015!- Based on post-LS1 experience and results of prototyping, launch a production line for action during LS2!

Many challenges ahead:- Finalize new collimator design- Production techniques for new materials, including coating- Beam validation of full scale prototype at CERN HiRadMat- Crucial tests of material properties under high irradiation Results expected from US-LARP (BNL) and Kurchatov See talk by N. Simos

Cu-CD Fracture Analysis

Mo-Gr composite

Cu-CD composite


Outline

Introduction




Conclusions


Hollow e-lens for the LHC

Tevatron hollow beams allow to control selectively (by amplitude) the diffusion ➙speed of halo particles control the ➙ “steady” tail population; decide when loosing halo (remove fast, erratic loss spikes); no affect on the beam core!

Why do we need it?1. If we are limited by quenches:Great advantage if we can control the time distribution of losses.This is the main motivation for the use of hollow e-lens for collimation!2. If we do not quench:Design lifetime (0.2h) with the HL-LHC intensity we will cause lossesexceeding the plastic deformation of primary/secondary collimators.3. Halo population control critical for operation with crab-cavities

CERN strategy, presented at the last US-LARP meeting:Focus present resources on achieving a conceptual design report by 2013, and a complete design report by end of 2014 to decide in 2015 about LHC installation.

Beam population

Diffusion speed

Talk by G. Stancari on Thursday


Status of activities with US-LARPAt CERN, we established links to achieve a design report by the end of 2014Collimation (S. Redaelli), beam instrumentation (R. Jones) and engineering team (A. Bertarelli).Synergy with halo monitoring H. Schmickler.➙

Planning now to setup an experimental test stand to characterize electron beams.

We are very happy with the collaboration with the US-LARP team (G. Stancari, V. Valishev) and we wish that this could continue further.

Recently we explored an exchange student program in collaboration with EPFL (L. Rivkin). Can we extend the Toohig fellow to PhD student? Giulio and Sasha suggested to consider the Fermilab joint PhD program as a model.

Topics that we are going to address:- Analysis of Tevatron data relevant for LHC- Tracking simulations hollow e-lens excitation

(continuation of V. Previtali, Toohig fellow)- Measurements of hollow beam in lab test stands

(at Fermilab and CERN)- Analysis of diffusion model at the LHC

(continuation of measurements done in 2012)

V. Moens, Diploma thesis, Sep. 2013.


Crystal collimation studies

Several open questions: - Can crystal collimation compete with the present very good cleaning system? - Uncertainty for the scaling to higher energy (e.g.: single diffractive losses). - Operational challenges for the complex operational cycle (ramp, squeeze, etc...). - Some outstanding machine protection concerns must be addressed. - Can we absorb more than 1 MW in one single block?Real need to improve the present system will be assessed in 2015 within the context of the collimation upgrade plans.

Primary

Secondaries

Absorbers

Beam

Standard collimation

Beam

Absorber

Crystal

???

Crystal-based collimation

Promises of crystal collimation:1. Improved DS cleaning in channeling;2. Reduce impedance: less secondary collimators and larger gaps;3. Much improved cleaning for ion beams.Note: only applicable to IR7 betatron cleaning, not useful for physics debris!

Promising results at the SPS.

Uncertainties on the extrapolation to unknown

energy territories and operational challenges call

for solid experimental validation before this

technology can be relied upon for future designs.


Status of crystal proposal for LHC

•Converged on IR7 layouts for machine studies in horizontal and vertical planes.

•Existing secondary collimators to be used as absorbers during low-intensity MD’s only. Worked out preliminary settings that optimize cleaning of a crystal-based system.

•Identified locations of additional detectors.

•LHC engineering change request (ECR) under approval with the following proposal:

•Cabling for complete experiment;

•Installation of 2 goniometers;

•Space reservations for detectors.(nice to have but not essential for the initially feasibility demonstration)

Talk by W. Scandale on Thursday!


Update on SLAC rotatory collimator

Nice concept. Might be reconsider it in light of the recent material tests and updated safe limits? Cannot be considered as candidate until fully validated by beam tests (HRM, SPS?)A beam test strategy will be established as soon as we have the chance to test it at CERN!Being shipped to CERN now!

See talk by T. Markiewicz on Thursday!


Scope of collimation consolidation“Optimistic” ballpark figures assuming that all upgrades discussed here are adopted for HL-LHC:- 22-30 new secondary collimators;- 4 more robust TCT collimators;- additional collimators in IR’s (new);- several DS collimator (new).

THIS LEAVES IN THE MACHINE AT LEAST 70 HIGH-PRECISION COLLIMATORS THAT WILL HAVE MORE THAN 15 YEARS BY LS3!

Several concerns:Mechanical wear in operationChallenging radiation environmentRadiation wear of componentsPerformance reduction from

thermo-mechanical and electrical property degradation due from radiation.

Talk by N. Simos tomorrow


ConclusionsThe LHC collimation upgrade is an integral part of HL-LHC

The present upgrade baseline was discussed. We have solutions to address the main critical issues identified for the

HL era! For us, important guidelines on upgrade strategy can only come in 2015,

as also recognized by a recent external review that supported our baseline.

From design to construction project:We are well advanced in terms of layouts, machine slots, space

reservations.TCLD + 11T dipoles: converged on baseline layouts for critical IR’s.New collimator materials: slots essentially ready, further improved in LS1.Outstanding issue: integration of hollow e-lens in IR4 PLC!➙

We set aggressive timelines to be ready for possible actions in LS2Very challenging schedule for 11 T dipoles (DS collimators in the shade)Working hard to get a fully validated prototype for tests after 2015 to improve the LHC impedance.

Solid solutions for the main challenges, but keep pushing new ideas: Advanced collimator concepts are more then ever on the table! Considering improved settings and operational conditions to address other limitations: some discussed in WP5 sessions, other in the pipeline.

Stefano Redaelli, CERN, BE-ABP for the Collimation Project and HL-LHC-WP5 teams The LHC Collimation...

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