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Atlas Tracker Upgrade LSWG-On Detector cooling. Eric Vigeolas CPPM, May the 31th 2012. Inner tracker cooling lines. U-link and fittings. This talk will only cover cooling lines from PP1 to PP1 and mainly on our past experience of Pixel detector and actual developments on IBL

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Atlas tracker upgrade lswg on detector cooling

Atlas Tracker Upgrade LSWG-On Detector cooling

Eric Vigeolas CPPM, May the 31th 2012

Inner tracker cooling lines
Inner tracker cooling lines

U-link and fittings

  • This talk will only cover cooling lines from PP1 to PP1 and mainly on our past experience of Pixel detector and actual developments on IBL

  • A cooling line is a complex assembly with a high level of reliability requested

  • Designing a cooling loop request to develop and qualify several techniques:

    • Thin pipe procurement

    • Joining techniques for sleeves of fittings (Gluing, Brazing, EB welding, Laser Welding, TIG welding ….)

    • For any designed loop an electrical break will be needed

    • Fittings will for any design be necessary and in many cases will be home made fittings

  • This talk will focus on metallic pipes, this do not mean that Carbon pipes are not possible (has been studied on pixel and IBL but did not match the thermal requirements  the main problem comes from the transverse thermal conductivity and the joining techniques which have to be developed

Exhaust Pipes


Layer 1 and 2 ATLAS Pixel detector

Pipes procurement
Pipes procurement

  • Number of vendor very limited, Price very high and quality sometime hard to achieve (no way to force the vendor to improve their quality, quantity ordered too limited)

  • Up to now all the metallic pipe we studied was made by cold drawn process. This process gives some good mechanical properties but limit the minimal thickness. Would it be interesting to investigate other process?

    • Hot drawn process

    • Rolled and welded

    • ???

  • The pipe choice will be driven by many factors:

    • Corrosion resistant (this means also compatible with any choice made for the sleeves or fittings)

    • Small CTE close to the local supports made mainly with Carbone composites (ideally should be close to Si CTE and local support should be designed to be as close as possible to Si one also)

    • Compatible with joining techniques

    • In many cases easy to bend (good plasticity)

    • Good transverse thermal conductivity

    • Low X/X0 with good Mechanical properties (both parameters are linked)

    • Not magnetic

    • Activation is a concern which need to be studied



CuNi inclusion in 0.2 thick pipe

  • Several company have been tested on Pixel and IBL:

    • Tabexact (

      • Pixel Aluminum pipes

      • CuNi capillary pipes

      • IBL Stainless pipes

      • No capability for instance to produce Ti pipes

      • Good production quality and accuracy

    • Minitubes (

      • Specialized in very thin medical pipes

      • Good experience in Ti

      • Have a pipe length limitation to 2m long pipes

      • Very high price (The reason why not chosen for IBL)

      • Impressive pipe quality and capability to reach 0.05 thickness in Ti

    • LNI (

      • Good capability to any pipe shape (this company made the cooling line for the Arian 5 engine)

      • All prototyping on pixel made with this company but have been changed for production quality reasons and our impossibility to force quality improvements (metallically dust pollution during drawn process and too high cost to work in clean environment )

    • High tech tube  see Richard talk

    • Many other vendors contacted:

      • Most of the time no capability to produce thin pipe

      • Not interested by the quantities requested

      • Sometime no way to choose our material

Strip induced by dusts in a thin Al pipe

Material choice
Material choice

  • Aluminum:

    • Used in large number of inner trackers

    • Large amount of alloys available (but not all of them easy to weld of easy to anneal)

    • We met corrosion problem on Atlas Pixel detector (Brazing was a wrong choice  metal plating is risky and the use of highly corrosive flex request a difficult cleaning process)

    • Laser welding and EB welding can be performed easily and work fine

    • Good candidate for X0 reduction  Is that a good choice for High pressure

    • No clear proof of direct corrosion induced by carbon in Detector environment should we forget this material forever?

    • CTE is a week point

    • Difficult to produce reliable capillaries (brittle..) is that the case for small ID pipes?

    • High plasticity which make the bending easy to perform

  • Titanium:

    • Used in large number of detectors, actually selected for IBL project

    • Large number of alloys but not sure to have hall the material available for pipes

    • Possibility to produce thin pipes but the oxide layer is a concern and make production more tricky to control

    • High mechanical properties (Actual 0.125 mm thick IBL TI pipes can support 250 bars without damages)

    • Have a good plasticity

    • The most advantage is the low CTE which permit us to design lighter structures

    • Very high corrosion resistance

    • Joining techniques have been developed and are intensively studied actually


  • Stainless steel:

    • Large number of vendors

    • Used in large number of detectors

    • Corrosion resistant

    • Better CTE than Al but worth than Ti

    • Joining techniques known

    • Possibility to produce very thin pipes and no limitation in dimensions

    • Activation compare to TI?

  • CuNi:

    • Was used for pixel capillary

    • Not good candidate for X0 reduction

    • Neither for CTE

Corrosion on Pixel fittings

What we learned
What we learned

  • Concerning aluminum the minimal thickness we succeed to produce was 0.2 mm, we never found a vendor who accepted or succeeded to produce thinner pipes  this do not mean impossible

  • Concerning Titanium we can reach very thin pipe (Minitube produce 0.05 mm thick pipe for stents) but the main difficulties remain in the oxide layer which has to be maintained as small as possible (Vacuum oven of in inert environment  High cost, pickling will be dangerous for very thin pipes)

  • Stainless pipe are more common pipes in vendor shops but most of the material properties are not in favor of this material selection (X0, Activation, CTE…)

Potential remaining studies
Potential remaining studies

  • Depending on the pipe material and manufacturing process the roughness will be very different from one material to the other

  • Thermal conductivity should not be the only parameter to define the boiling channel performance

  • Should be interesting the investigate HTC vs Roughness of the pipe for boiling channels in Local supports

Few parameters on common materials
Few parameters on common materials

Very subjective analysis


  • Pipe selection for the cooling line is a very complex task

  • This depend highly on production available on the market

  • The relationship between the pipe vendor and us is crucial to reach the proper production quality  We should produce prototypes and production tubes in the same batch to avoid production quality fluctuations

  • This selection need to be combined with joining techniques development, bending ones and local supports prototyping