Phase II Collimators at CERN: design status and proposals
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Phase II Collimators at CERN: design status and proposals. EuCARD/ColMat kick-off meeting 17 th June, 2009. Alessandro Bertarelli. Who at CERN. Mechanical Engineering: Alessandro Bertarelli, Alessandro Dallocchio, Ricardo de Morais Amaral

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Phase II Collimators at CERN: design status and proposals

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Phase II Collimators at CERN: design status and proposals

EuCARD/ColMat kick-off meeting

17th June, 2009

Alessandro Bertarelli

Who at CERN

Mechanical Engineering: Alessandro Bertarelli, Alessandro Dallocchio, Ricardo de Morais Amaral

Material Science: Gonzalo Arnau Izquierdo, Romain Blanchon, PhD student

Mechanical Design: Roger Perret, Arnaud Bouzoud, Bruno Feral, Marc Timmins

Manufacturing: G. Favre, L. Ferreira, A. Cherif

Plus many more from EN, TE and BE departments

Limits of Phase I Collimators

  • Resistive Impedance According to RF simulations, Phase I Collimator Impedance would limit LHC beam intensity to ~40% of its nominal value!

  • Cleaning efficiencyCleaning efficiency (i.e. ratio escaping protons / impacting protons) should be better than 99.998% to limit risks of quench in Super Conducting magnets. Simulations predict a beam intensity limited to ~40% of Inom for perfect collimators.

  • Radiation HardnessOngoing tests anticipate risks of degradation of Carbon/Carbon jaws (reduction of thermal and electrical conductivity, swelling, dust …)

  • Set-up and calibration timeStandard methods, based on measurement of beam loss generated by jaw adjustment, lengthy, requiring specific low intensity fills

Phase II goals

  • Gain factor ≥10 in cleaning efficiency.

  • Gain factor ≥10 in impedance.

  • Gain factor ≥10 in set-up time (and accuracy?).

  • Radiation hardness and easy handling.

  • Improved geometrical stability (in operating conditions) 20 mm

  • Sufficient robustness (like Phase I?).

  • RWA May 2008

Phase II Design Features

  • Jaw design

    • Modular design (a common baseline for the jaw assembly allows the use of alternative materials for the jaw).

    • Back-stiffener concept to allow maximum geometrical stability (improves collimator efficiency).

    • Adjustable system to allow jaw flatness control and compensate gravity sag (2 versions being studied … )

    • Optimized internal cooling circuit to absorb higher heat-loads.

    • Integrated BPMs to minimize set-up time.

  • Jaw materials (goals)

    • Tailored electrical conductivity to improve RF stability.

    • High thermo-mechanical stability and robustness.

    • Higher density (high-Z) to improve collimation efficiency.

    • Strong resistance to particle radiation.

Phase II Design options

…depending on RF and cleaning efficiency specifications…

Alternative Materials

Metal jaw (high electrical conductivity) vs. Ceramic jaw (non-conductive) on metal conductive support...

Phase II Design baseline (v1)

Modular concept to fit in alternative jaw materials ...





Equipped Jaw (v1)

1st version of equipped jaw (1 adjustable support) … SiC absorber shown …

Ceramic tiles SiC brazed on metal (conductive) support …Cu-CD is favorite candidate

Machined cooling circuit with brazed cover.

Fine adjustment system

Design Baseline (v2)

RF contacts ensure electrical conductivity between jaw pieces

Alternative design of equipped jaw based on 2 intermediate adjustable supports …

Fine adjustment system

Mo Back - Stiffener

Cut jaw: each piece is independently supported on the back stiffener. Enhanced geometrical stability

Design Baseline (v2)

3-pieces jaw independently cooled by three separate brazed coolers


Jaw - Stiffener

Machine cooling circuit with brazed covers

Back - Stiffener

Cooler prototype

Using high Z-material leads to higher energy deposition (up to a factor 5 increase w.r.t. Phase I). Higher cooling capacity is essential to ensure geometrical stability…

Two prototypes including machined circuit, brazed cover and jaw mock-up have been produced and successfully tested…

Cooler prototype

The goal is to define a complete and standardized procedure according to UHV specs. in order to qualify the design.

Jaw mock-up

Test successfully performed:

  • He leak detection

  • Ultrasound cartography of the brazing surfaces

  • Pressure test (100 bar over 1h)

  • Final He leak detection.

Machined circuit

Brazed cover

BPM functional prototype

Graphite inserts

BPM cables

OFE-Cu jaw support


  • Lab. tests to start April/ May 2009

  • Beam tests in SPS during 2010 run (installation dates to be determined …)

Mechanical design of simplified jaws featuring BPMs…


BPM buttons

Motivation: BPMs integration strongly influences the design of the whole system. A rapid testing in the SPS of the BPM embedded system is mandatory to validate the concept.

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