Work required to have a proposal in June

(for discussion)

RA, CPM, 15/4/03

Goal: Present a conceptual proposal to the LTC in June. “How we believe we could build a working collimation system”

Level of detail required: No time to have very detailed studies ready.

However, need to show that proposed solution is basically adequate (no show-stopper):

• Collimators must survive operation with LHC beams

• Mechanical tolerances can be met (~ 25 m surface flatness, …)

• Collimator opening can be guaranteed at all times (error < 50 m)

• Collimators can be moved by small steps (~ m, ~rad)

• Settings must be reproducible to < 20 m

• Vacuum is manageable (T<50˚C, small surface, good outbaking)

• Local e-cloud is manageable (installing clearing electrodes, solenoids?)

• Collimators can be serviced and exchanged in high-radiation area

• Downstream equipment is OK for considered cases

• Reliability must be sufficiently good

• Impedance is manageable (~ 110 MΩ/m) for the overall system

• Operational tolerances (orbit/beta beat) are manageable

• Cleaning efficiency is sufficient

• Loss rates are acceptable (no quenches, acceptable background)

Discussion of work done and required:

A lot of work was done over the last months.

The worst case (1 module dump pre-trigger) went down by a factor 2.5 (thanks to the work in BT).

Graphite looks hopeful for survival and vacuum concerns, bad for impedance (three-stage system?).

New major problem was discovered (impedance).

Beryllium seems not OK for survival (might still be used for some jaws).

Work was presented at several occasions and feedback was positive and encouraging (people were happy seeing the results and progress on the different fronts).

However, in spite of all the work: No complete picture yet available.

More work ahead of us!

What do we need to do by June to go ahead? (my understanding)

What feedback and outcome do we want in June?

Get basic approval for the solution that we want to adopt.

• We must show that our proposal addresses the major concerns and does not impose new problems (e.g. background at IP’s, safety problems).

• We must give a basic idea of the required budget and schedule.

Support for starting design and construction of collimator prototypes.

• Proposal must be complete enough to avoid another iteration for addressing open and serious questions.

Freeze the cleaning insertions and start finalizing their layout.

• The basic space requirements must have been understood and specified.

Accelerator physicsFeasibility of three-stage system:

• Implement three stage system into tracking.• Predict proton loss rates around the ring.• Estimate power deposition (quench thresholds).• Cleaning efficiency.

Input to FLUKA/ANSYS:

• Define ion case.• More detailed slow case once generic case was studied.

Impedance:

• More final estimates on impedance and budget.• Impedance for detailed configurations (mechanical layout, tank, …).

E-cloud:

• First rough estimate on order of magnitude (requires FLUKA input).

System design:

• Determine all required collimators / absorbers (some additional absorbers)

FLUKAGeneric cases for material selection:

• Slow case• Energy deposition in downstream tank and pipe walls (requires engineering estimate)• Ion case• Cu doped C• Carbon-carbon (simple Graphite might be used?)• E-cloud

Checks for background in experiments for three-stage system:

• Showering in tertiary collimators• Tracking of showers through the IP’s (IP1, IP5, IP8, IP2) and detectors• Evaluation of expected background, false trigger rate

ANSYS and Scheme for CollimatorDamage and fatigue analysis:

• Static stresses for all cases• Dynamic stresses if static stresses are OK for generic configuration

Select BEST material

Basic mechanical layout (conceptual) of jaws in tank:

• Identify relevant options (standard solution, pipe collimators, …)• For each option: Schematic drawing

Cooling schemeTemperature mappingPrediction of achievable tolerances (deformations, …)

Outgassing estimatee-cloud estimate (depends on wall-to-wall distance)

Impedance issues (tapering, trapped modes, …)

Vacuum requirements (baking, pumps, clearing electrodes, solenoids)

Scheme for determining collimator gap (fail safe)

Select BEST option (know length/space requirements)

Maintenance and HandlingEstimate of personnel exposure:

• Guesstimates of required number of interventions and their duration.• Rough estimate of personnel exposure. (TIS)

Decide on level of required remote handling.(know space requirements)

Consequences for mechanical design:

• Implement basic features that result from handling requirements. (cost?)• Decision might influence the favorite option for collimators.

LTC Preparation• Do a set of calculations for final choices of primary and secondary collimators

with new dump re-triggering time.

• Collect all results and prepare presentations explaining the technical reasoning behind the proposal, addressing ALL difficulties and open questions.

• Present ONE convincing and coherent proposal from the collimation team.

• Establish a rough budget.

• Establish a rough schedule.

• Pose a clear request to the LTC (approval, budget, support, …)

ConclusionExcellent technical work has been done.

Time is extremely short and many questions must still be addressed.

No delays can be accepted without missing our goal (basic proposal before Summer). Reducing the number of CPM’s to free a few hours…

A delay would be significant (September/October) and would harm our prospects to support the LHC schedule.

We need a good and realistic work plan now. Feedback from all team members required. (what is forgotten, what can be delayed, what is not important, …)

The good news: If we succeed with the proposal in June we should be sailing ahead smoothly…