Stato del sistema di raffreddamento del rivelatore spd di alice
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Stato del sistema di raffreddamento del rivelatore SPD di ALICE. Rosario Turrisi. Cooling : working principle. PP1. PP3. PP4. PP=patch panel. heaters. ~35m gas pipes 12/10-10/8 mm. ~40m liquid pipes 6/4 mm. capillaries. liquid pump. condenser. pressure. cooling tube.

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Stato del sistema di raffreddamento del rivelatore spd di alice

Stato del sistema di raffreddamento del rivelatore SPD di ALICE

Rosario Turrisi

Cooling working principle
Cooling: workingprinciple




PP=patch panel


~35m gas pipes 12/10-10/8 mm

~40m liquid pipes 6/4 mm


liquid pump



cooling tube

Filters (60μm)


p, T

two ‘knobs’:

liquid-side pressure flow

gas-side pressure temperature

  • Joule-Thomson cycle

    • suddenexpansion + evaporationatconstantenthalpy

  • Fluid C4F10: dielectric, chemicallystable, non-toxic, convenienteos

    • Nominalevaporation: 1.9 bar, 15°C

      • now: difficultprocurement


The issue
The issue

Start of LS1  <45%

  • extrapolation from last year

  • assumes constant trend

Performance worsening in time

Minimum acceptance reached: 62.5%, most because of cooling failure

Critical components
Critical components

SEM picture of the filter

(orange square=1mm2)

no access

PP=patch panel



D = 5.6 mm

T = 11.8 mm

X = 0.7 mm (~1 mm in the filtering area)


  • Capillaries (CuNi, 550 mm long, 0.5 mm i.d.)

  • Cooling pipes

    • Phynox, 40 μm wall thickness

    • Round 2.8 mm pipes squeezed to 0.6 mm inner size

  • Inline filters

    • Fundamental to protect previous items, 60 μmporosity

    • 1 accessible during beam stop

    • 1 accessible dismantling part of ALICE (~6 months job)

  • (Missing) filter at the plant

    • added after 1 year run a 2 μm filter at the liquid outlet

Chase the guilty
Chase the guilty

  • The filters mesh has 60 μm size in average

    • smaller sized particles can be stopped and bigger can go through!

    • some pollution can pass the first filter and stop on the second

  • Once clogged, the second (PP3, not reachable) filter causes:

    • pressure drop

    • lower flow rate

  • Add the heat-up of the fluid along the supply line, and you have:

    poor cooling performance & local inefficiencies

20 μm

  • Search and confirm the cause has been a long and painful process, 4 years long

  • All procedure tested on a dedicated test bench set up by our team with CERN

  • Many tests performed

    • SEM analysis of PP4 filters enlightening…

      • many particles of several materials, possible origin:

        • graphite from pumps, weldings, plant’s hydrofilter

The hard way drilling
The hard way: drilling


After several (unsuccesful) attempts (solvents, ultrasounds) we went ‘’the hard way’’ with the following procedure:

  • drilling:

    • tungsten carbide tip welded on 5 m long twisted ss cable, rotated by a drill

    • counter-flow at 200 mbar w/manometer to detect the presence of the hole (~50 mbar drop)

    • takes 2-3’

  • cleaning:

    • rilsan pipe connected to a rotary vane vacuum pump to aspire the drilling debris

    • walk inside the pipe with a twisted ss cable with a magnetic tip fixed at the end

    • cleaning machine to force counter-flow wise a cleaning fluid

    • repeat several times the previous steps

    • last, let the cleaning machine run overnight (or more) with a 60 m filter to collect particles

    • analyze this filter with an optical microscope and (if needed) the SEM

    • redo the cleaning procedure if not happy

Edwards RV3 rotary vane 2-stage pump


L=5 m, Ø=1.5 mm


tungsten carbide 5-faces tip

cleaning machine

Access point

Ø 2.5 mm ss twisted cable

4.5 m of ss pipe 4mm i.d.

Target point

The drill team
The drill team


Andrea Francescon

Samuel Rambaut

Claudio Bortolin

Rosario Turrisi

Royal straight: five nice cards but the strength is the team!

And we’re well backed by the whole SPD team!

Clean it
Clean it!

Material collected after

the cleaning procedure

Material collected by

vacuum cleaning after drilling

Analyses by Norberto Jimenez Mena and Maud Scheubel (EN-MME-MM)

Sector #9 drilled on Feb 14

Materials analyses
Materials analyses

stainless steel

silicon compounds

(a.k.a. ‘’dust’’…)

fluorine compounds

100 μm

100 μm

100 μm

Analyses by Norberto Jimenez Mena and Maud Scheubel (EN-MME-MM)

Interventions and results
Interventions and results

hs on











1.8 g/s = nominal value

new flow rate values

old flow rate values

drilled filters

  • Drilled 5 filters: sectors 9 (Feb 14), 7 (Feb 27), 6 (Mar 6), 4 & 5 (TS Apr 23-27)

  • Oldest flow rate values from last November

  • 8 sectors above nominal value

    • 5 drilled, 3 because of vacuum cleaning

  • Last cleaning of sector 3 restored the possibility to turn it on completely!

Recovered acceptance
Recovered acceptance

…to this!

cannot be recovered

could be recovered


65/120 modules ‘’on’’ - 62.5%

snapshot from November 10, 2011

112/120 modules ‘’on’’ - 93.3%


100% cooling efficiency !!!

Acceptance changed from this

Happy end
Happy end!

…and the SPDer’s

  • Recovered the cooling system to 100% efficiency

    • no more ‘’special maintenance’’ until pPb run (unless needed)

  • The plan for LS1 changed accordingly: no need to move TPC, ITS, etc. (>6 months job!)

    • If needed could do the drilling of the 5 left filters

  • Finally our soundtrack plays!

Attività SPD @ CERN

  • TS3 (17-21 Settembre 2012)

  • Test in pressionedellevecchielinee di input (2 pp x 4gg)

  • Durante LS1 (11 Febbraio 2013 – xx/xx/2014)

  • Rimozionenuovelinee input e subcooling (4 pp x 5gg)

  • Ripristinovecchielinee (pulizia, connessioni, leak test) (4 pp x 10gg)

  • Consolidamento rack impianto (CERN EN/CV/DC)

  • Installazionefiltroacqua (CERN EN/CV/DC)

  • Ricalibrazionevalvolesicurezza (CERN EN/CV/DC)

  • Ricalibrazionesensoritemperatura e pressione (2pp x 5gg)

  • Foraturafiltri di 5 settori (dipendente da andamentoprestazioni, 1ppx15gg +pers. CERN)