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

EuCARD/ColMat kick-off meeting

17th June, 2009

Alessandro Bertarelli

Who at cern
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
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
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
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
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
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
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 v21
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
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 prototype1
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.