Stato del sistema di raffreddamento del rivelatore SPD di ALICE

1. Stato del sistema di raffreddamento del rivelatore SPD di ALICE Rosario Turrisi

2. Cooling: workingprinciple 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 Filters (60μm) compressor 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 enthalpy

3. 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

4. Critical components SEM picture of the filter (orange square=1mm2) no access PP=patch panel X T D = 5.6 mm T = 11.8 mm X = 0.7 mm (~1 mm in the filtering area) D • 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

5. 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

6. The hard way: drilling TESTED BY DRILLING > 100 FILTERS ! 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

7. Edwards RV3 rotary vane 2-stage pump Fiberscope L=5 m, Ø=1.5 mm magnet 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

8. The drill team YannickLesenechal 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!

9. 200 μm

10. 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

11. 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)

12. Interventions and results hs on 12 11 12 12 10 11 11 11 12 10 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!

13. Recovered acceptance …to this! cannot be recovered could be recovered hot 65/120 modules ‘’on’’ - 62.5% snapshot from November 10, 2011 112/120 modules ‘’on’’ - 93.3% NOW RUNNING 100% cooling efficiency !!! Acceptance changed from this

14. 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!

15. 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)