update on the lhc collimation system design : status, deadlines and next steps

Update on the LHC collimation system design : status,

deadlines and next steps

R. Assmann

AB/ABP

StatusStart of project

Definition of phased approachCollimator specifications for phase 1

System layout(optics, energydeposition, …)

Radiation,collimatorshielding

Collimatormechanical

design

Motors, controlelectronics

Budget

Prototyping, verification with SPS test

Series production

Phase 2 R&Ddesign, production

OCT02

JUL03

MAY-OCT04

2005-2006

Installation, commissioning2006-2007

Collimation projectLeader: R. Assmann

Project engineer: O. AberleOrganization, schedule, budget, milestones, progress monitoring,

design decisions

Project steeringE. Chiaveri report to

AB division(S. Myers, LTC)

LHC project(L. Evans)

Beam aspects R. Assmann, LCWG

System design, optics, efficiency, impedance (calculation, measure-ment), beam impact, tolerances, diffusion,

beam loss, beam tests, beam commissioning, functional specification

(8/03), operational scenarios, support of

operation

Energy deposition, radiation

A. Ferrari (collimator design, ions)

J.B Jeanneret (BLM’s, tuning)

M. Brugger(radiation impact)

FLUKA, Mars studies for energy deposition around the rings. Activation and handling requirements.

Collimator engineering & HW

support O. Aberle

Sen. advice: P. SieversConceptual collimator de-

sign, ANSYS studies, hardware commissioning, support for beam tests,

series production, installation,

maintenance/repair, electronics&local control, phase 2 collimator R&D

Mechanical eng-ineering (EST)Coord.: M. Mayer

Engin.: A. BertarelliSen. designer: R. PerretTechnical specification,

space budget and mecha-nical integration, thermo-mechanical calculations

and tests, collimator mechanical design, prototype testing,

prototype production, drawings for series

production.

Resources/planningR. Assmann, E. Chiaveri,

M. Mayer, J.P. Riunaud

Machine ProtectionR. Schmidt

VacuumM. Jimenez

Beam instrum.B. Dehning

Dump/kickersB. Goddard

Integration into operationM. Lamont

Supply & orderingO. Aberle, A. Bertarelli

Local feedbackJ. Wenninger

ControlsAB/CO

Electronics/radiationT. Wijnands rearranged Aug03

System layout

1. Space requirements1.2 m per primary collimator (was 0.4m)4.0 m per secondary collimator (was 0.7m)

2. Optics that provides required spaceoptimizes inefficiencyminimizes impedanceprovides basis for LHC layout IR3/7

3. Energy deposition for new opticsdetailed geometry including collimatorsdifferent shielding options

4. Final layout with required absorberswith required shielding (cooled?)with required handling

OCT03

JAN04

FEB04

Schedule as presented 12/02 and 6/03. Discussed and agreed with C. Hauviller et al again in 10/03 (some installation of services had started in IR3/7).

Remark on space coverageAvailable space between doglegs in V6.4:

340.9 m

Required for secondary collimators:

128.0 m (16 times 4 m times 2 beams)

(beam1 and beam2 collimators at different locations)

Space taken by collimators:

~ 40 % (~15% for phase 1 collimation)

(keep this in mind when talking about “local collimator shielding”)

Basic optics choices IR71. Standard solution with special phase advances

(DJ optimized, J.B. Jeanneret and D. Kaltchev)

2. Solution with 90 degree FODO

• Relax phase advance conditions• Match regular (close to 90 degree) lattice• Move collimators towards equal beta to minimize impedance• June03: Approach works for generic lattice (RA/VK), good

efficiency (twice better), low impedance (2-3 times better)

3. Something in between

Optics work done in ABP optics team, matching work done by D. Kaltchev, TRIUMF. Coordinated in collimation WG.

Cleaning efficiency: Full system

At 10 : 3.49·10-4 (full C, V6.2) → 1.66·10-4 (full C, 90)

RA/VK7/7/03

MADX #TCS Lmin(TCS) Beam1/2 Inefficiency Impedance

Option 0 standard6.4 16 0.7 m yes/yes 3.5e-4 10.2

Option 1 6.4new 16 4.0 m yes/yes 5.2e-4 9.3

Option 2 64imp12 12 4.0 m yes/no 12.3e-4 4.3

Option 3 regular 16 4.0 m yes/yes 9.7e-4 2.8

Option 4 IR7warmQ6 16 4.0 m yes/no 11.9e-4 ?

Real LHC solutions IR7

VERY PRELIMINARY RESULTS – STUDIES ONGOING…

Impressions: We cannot get close to 1.7e-4 inefficiency, even with 16 secondary collimators!

Clear trade-off inefficiency – impedance!

Optics “6.4new” has smallest changes to V6.4 optics.

How to decide?Phased approach:Phase 1: Maximum robustness at impedance limit with good efficiency.

Phase 2: Same optics as phase 1 but fix impedance problem with hybrid collimators.

IMPORTANT: Optics choice fixes best achievable inefficiency (forever?).

Criteria for decision:1. Solution should provide best inefficiency!

2. Fix impedance with hybrid secondary collimators.

3. Phase 2 collimation remains indispensable (after 1 year)!

Supported by results from ABP collective effects team: Possible gain in impedance not sufficient to rely only on phase 1 collimation!

Margin in inefficiencyCleaning inefficiency is the most important performance measure of the cleaning system:

Required: 10e-4

Best IR7 optics: 5e-4

Uncertainty in inefficiency: up to factor 3 higher

Effects of imperfections: loose factor 1.5-3.0

THERE IS NO MARGIN! (Gain with tertiary collimators factor 2-10?)

More detailed studies in ABP with new fellow and new PhD student:

More realistic tracking with all errors an imperfections.Beam-based tuning of collimator settings.

Phase 1: Used for early physics as a 3-stage system

Phase 1 (early physics): Operating at impedance limit with high robustnessOperating at impedance limit with high robustness (7/10.5/13.5).

Relaxed tolerancesRelaxed tolerances: mechanical and for orbit/beta beat, good

efficiency.

Triplet protection and local cleaning at tripletsTriplet protection and local cleaning at triplets.

15

10

5

0

-5

-10

-15

Scraper

Primary Ccollimator

Secondary Ccollimator

SC triplet

Primary beam & halo

Secondary halo

Tertiary halo

Offset()

IR7 LHC experimental insertion

+- 13.5

orbit

Tertiary Cucollimator

Quartiary

Present conclusion for IR7• Not enough space in IR7 to make 90 degree lattice work (with cold

Q6).

• Warm Q6 does not help either (a little bit puzzling)!?

• Achievable best efficiency (with V6.4 modified) is already at limit with 16 secondary collimators.

• Reduced number of collimators (as foreseen) will cost a little more in efficiency.

• Impedance is not reduced by this optics!

• Phase 2 collimation is indispensable (after 1 year?)!

Other collimator regions

IR3: New optics should be re-matched without problem (no re-design, just make space).

TCSH: Included into IR3/IR7 design.

TCSP: Short objects, not yet included in IR3, IR7 design (should be no problem).

TCT: Start engineering change requests soon (agreed with LHC installation).

TCLI: Space as reserved in layouts has not been respected. Can we live without them?

TCLP: In layout. No change expected. Integration problem with TOTEM (phasing).






design


Budget


Series production


OCT02

JUL03

MAY-OCT04

2005-2006


Material choiceFirst action after approval of phased approach with first phase graphite collimators:

Ordering of jaw material (graphite C, fiber-reinforced graphite CC).

Companies:

STEINEMANN Carbon AG (DE), SNECMA Propulsion Solide (FR), POCO Graphite (US), Tatsuno Company Limited (JP), SGL Carbon AG (CH), ERODEX LTD (UK/US)

Delivery delays: 3-7 months promised

Sufficient material now at CERN for material studies, clamping test, early prototyping, …

Best electrical resistivity: 7 /m with CC (O. Aberle)

(twice better than assumed gain ~ 25% in impedance)

Material of choice: Low resistivity fiber-reinforced graphite

Ordering 9 jaws now for SPS test (min. 3 required)from 3 different companies…

Mechanical collimator designEffort led by strong EST team:A. Bertarelli, M. Mayer, R. Perret, …

assisted by AB/AT:O. Aberle, R. Assmann, P. Sievers, …

Collimator design meeting (organized by M. Mayer)

Some dates:

Dec03 Test of clamping for graphite on metallic cooling support

May04 Prototypes of secondary collimator ready

Aug04 Installation into SPS

Dec04 Drawings for series production

Status of mechanical designA flexible design for all secondary (and primary) collimators has been developed with…

– IR3/IR7 space constraints (small inter beam distance)

– required cooling for graphite jaw

– required impedance measures (tapering, RF contacts)

– required mechanical precision movements

– no local shielding

– LEP type motors close to the jaws

Design is being verified with ANSYS calculations and experimental tests (clamping & cooling Dec03).

First full prototype in May 2004.

Risks1. Clamping technique cannot be used adopt state-of-the-art

technique as used for example for ITER (2-3MCHF + 2years).

2. Heating of metallic collimator parts (cooling everywhere?)

3. The need for shielding may require different collimator design (see SNS).

4. Major design changes if motors must be put outside of shielding or far away from jaws (LEP motors require yearly human maintenance).

5. …

Simple and fast collimator design is being pursued and will ensure to provide prototypes for SPS test.

However, we realize that boundary conditions are very difficult.

Accept risks in order to ensure that LHC collimators are ready in time for phase 1.

Advanced solutions

Low radiationLow radiation SNS design(courtesy G. Murdoch)

Consumable NLC design(courtesy J. Frisch)

Liquid metal recoatable NLC colli-mator(courtesy J. Frisch)

High robustnessHigh robustness

Bent crystral collimator (courtesy V.M. Biryukov et

al)

Design of other collimators

TCS Being worked out.TCP Short version of TCS.TCSP Short version of TCS?TCT Special design, specific to IR’s.TCLI Special design.TCLP Use TCS basic design with Cu jaw?TCSH Advanced design done with SLAC?

Lot’s of work still ahead…






design


Budget


Series production


OCT02

JUL03

MAY-OCT04

2005-2006


Motors, electronics, controlResponsibility of AB/ATB with support from AB/CO.

We must realize: <10 micron step size~15 micron reproducibility of settings35 mm maximum travelInitially: ~300-400 motorsMaximum: ~600 motors

BIG SYSTEM: RELIABILITY IS CRUCIAL!

Difficult access to motors: High radiation close to jaw…Inside shielding?

LEP motors might not be adequate: Yearly human maintenance!?

AB/ATB effort will be starting to review possible solutions.AB/CO will provide interface to control system (SPS test).






design


Budget


Series production


OCT02

JUL03

MAY-OCT04

2005-2006


Radiation & collimator shielding

Radiation a concern from the start onwards:

Work in CWG with M. Brugger / S. Roesler

Phased approach relies on the possibility to install collimators after one year of running.

This was verified without shielding:

Intense tracking campaign with graphite collimators (M. Brugger).

Recent news: Shielding at collimators is required!

Dose rate for a carbon collimator - One day of coolingAll results are shown in mSv/h.

Collimator Pipe Shield

Tunnel without shield Tunnel with shieldM. Brugger, S. Roesler

1h40m intervention to change a carbon collimator (1 day cooling):1h40m intervention to change a carbon collimator (1 day cooling):

Primary collimator0.7 mSv (unshielded) 10 mSv (shielded)

Secondary coll. 0.07 mSv (unshielded) 1 mSv (shielded)

We do not want shielding at the collimators, if at all possible!We do not want shielding at the collimators, if at all possible!

The shielding problem in IR7Goal: Reduce environmental impact from collimators by factor 12.

20cm full shielding: gives factor 3-4

Complete shielding: gives factor 12

Complete shielding is one attractive option!?

Problems: - Very restricted space.

- Increase dose rate per human intervention by factor 15.

- Collimators cover up to 40% of longitudinal space (local shielding is important).

Studies are ongoing. Still various lines of attack!?

The loss in IR7 (critical)Memo S. Roesler to R. Assmann (23.10.2003):

Environmental studies: 5e16 p/year

Induced radioactivity, etc: 2e16 p/year

Assumed scenarios (I take nominal, they use ultimate):

Scenario Filled in 180days Fraction lost in IR7*

one 20h fill/day 6e16 p/year 83%

two 8h fills/day 12e16 p/year 42%

*Assume all losses in betatron cleaning.

Gain a factor 2-4 on these assumptions? Factor 12 seems hard for nominal running (would require IR7 losses < 3-7% at 7 TeV)?

However, losses at 7TeV are most important, …

Switching momentum (10 times lower losses) and betatron cleaning NO.

Phased approach for shielding in cleaning insertions?

Further detailed analysis is required for losses in IR3/IR7!






design


Budget


Series production


OCT02

JUL03

MAY-OCT04

2005-2006


SPS testThe SPS is an ideal test-bed to verify the performance of an LHC prototype collimator in various important aspects (and gives us some additional rigid deadlines):

1.The robustness of the proposed Carbon-based jaw can be tested with the specified LHC maximum shock impact of protons on the collimator face (impact of a full 450 GeV SPS batch – 4 PS batches).

2.Predictions on shower development and heating downstream of shock beam impact can be verified.

3.The functionality of a prototype collimator can be tested with minimum gaps down to 3.0 mm, close to LHC minimum closure (SPS stored beam at 270 GeV and collimators at 3 ).

4.The impedance of the carbon jaws can be measured with the SPS beam in various ways: detuning of a dense single bunch, threshold for beam instability with closing jaws (real time measurement with 100k turn BPM set-up), dipole kick, tune shift.

5.Unforeseen HOM’s would be observed.

6.The beam loss maps downstream of the installed LHC collimator can be recorded with Beam Loss Monitors and then compared with simulations.

7.The LHC type orbit feedback can be tested close to a collimator with special emphasis on studying systematic effects induced by beam loss and associated showers.

8.Vacuum behavior close to the Carbon-based jaws can be monitored during the robustness test and “regular” operation.

LHC collimator test in the SPSGoal: Show that the LHC collimator has the required functionality and properties (mechanical movements, tolerances, impedance, vacuum, loss maps, …).

Equipment: Full LHC V collimator prototype (secondary collimator, length with flanges = 2.0 m). Includes two fully movable carbon-based jaws (1.2 m), all motors, cables, cooling water, all local monitoring, tapering, RF contacts, local electronics and controls, interface to SPS/LHC

control system, simple controls application, outbaking equipment, …Jaws without coating…Maximum full gap is 60 mm.

Installation: 11 Aug 2004

Location: QF522

Beam: 270 GeV stored beam, single bunch plus LHC type beam

Time: 9 shifts (3 setup, 6 measurements)

Approved last week…

TT40 robustness testGoal: Show that an LHC collimator jaw survives its expected maximum

beam load without damage (no damage to jaw material nor metalliccooling support nor water leak).

Equipment: Single carbon collimator jaw (secondary collimator, length = 1.2 m)Installed on regular metallic support with coolingRemote moving mechanism, coating must be decidedJaw is under vacuum

Installation: 11 Aug 2004

Location: Upstream of TED dump

Beam: Nominal LHC extracted batch (450 GeV, 3e13p, nom emittance, 2.3 MJ)

Time: 3 shifts (1 setup, 1 measurements, 1 experiment by RS/VK)

Approved last week…

Summary of milestones1) System layout:

Oct 2003 Choose optics (1 month late), start MARS/FLUKA

Nov 2003 ECR for tertiary collimators in IR1/IR2/IR5/IR8

Start first loop in IR3/IR7 with installation group

Decide on TCLI collimators

Jan 2004 Review energy deposition calculations

Feb 2004 Freeze cleaning insertions

2) Mechanical design:

Oct 2003 Order jaw material for prototypes

Nov 2003 Start preparatory work for SPS test (support, …)

Dec 2003 Clamping and cooling test

May 2004 Delivery of prototypes for SPS test

Jun 2004 Start design of other collimator types

Aug 2004 Installation of prototypes into SPS and TT40

Dec 2004 Drawings for series production

3) Motors/electronics/controls:

Nov 2003 Order/organize cables for SPS test

Review radiation impact on motors

Start work with AB/CO

Dec 2003 Discuss market survey and MTBF

Order a few candidates

Feb 2004 Radiation hardness tests?

…

Jun 2004 Install motors on prototype

Jul 2004 Test local and remote control

Aug 2004 Everything ready for SPS test

Jan 2005 Order motors, electronics, cables, …

4) Radiation and shielding:

Nov 2003 Start calculations for different shielding options

Review loss assumptions

Decision on collimator shielding (TCC)?

Critical challenges1) Show that fast and simple clamping technique works. (Dec03)

2) Show that layout with carbon collimators has acceptable energy deposition. (Feb04)

3) Show that motors can survive close to the jaws. (Mar04?)

4) Show that the developed collimators and required shielding can co-exist, including remote handling equipment. (Mar04?)

Each of these challenges can cause deep trouble (money, time, …)!

5) Show that efficiency is good enough and that system can be optimized as required with beam. (2004/5)

Here we do the best possible (IR3/7, tertiary collimators). No way out!?

6) Low impedance design for secondary hybrid collimators!

update on the lhc collimation system design : status, deadlines and next steps

Documents

collimator mechanical

ferrari collimator design

primary collimator

beam tests

beam commissioning

secondary collimators

system layout optics

optics thatprovides