CLAUDIO BORTOLIN SPD Cooling Status INFN – PD / CERN

SPD Cooling station ~50 m SPD ~8 m R mi = 39.3mm R mo = 73.6mm L zs = 282mm Silicon Pixel Detector (SPD) SPD SIDE C SIDE A

3

SPD Sector 9 SPD Sector 7 SPD Sector 6 SPD Sector 5 SPD Sector 3

Bellows C side A side Collector from the plant to the plant 5 1 cooling line feeds 6 staves input: collector box, 6 capillaries 550 mm long, 0.5 mm i.d. output: collector box, 6 minipipes ~10 cm long, 1.1 mm i.d. 2 bellows in a row, ¼” tube diameter, 6” and 12” length

Joule-Thomson cycle: sudden expansion + evaporation at constant enthalpy liquid pump capillariescondenser compressor cooling tube enthalpy pressure Temp [ ° C] Pres [bar] Fluid C 4 F 10 : dielectric, chemically stable, non-toxic, convenient Eq. of state Adjustable Parameters Liquid pressure ≡ Flow Gas Pressure ≡ Evap. Temperature

Corrosion: no corrosive of other materials; Condensation: the temperature of the half staves must be close to the room temperature to avoid condensation; Temperature gradient: to minimize it along the staves; Budget: to keep the material budget as low as possible; Compatibility: high chemical and electrical compatibility; 7

8 liquid pump capillaries condenser compressor cooling tube enthalpy pressure Last installations: 10 Pressure regulators + 10 Flow Meters Filters inline in SS (60 μ m) 2 per line (PP4 and PP3) filters in PP3 (not reachable) PP4 PP3 PP1

Cooling pipes installed by the team from Padova after they had been cleaned 9 The system was tested in DSF at CERN for ~ 3 years very stable even if parameter settings were changed (1-2 sectors at a time) 100% efficiency until installed in the cavern: SPD was installed in the cavern in 2007; the 2 half barrels were tested one at time detector at full power (~150 W/sector)

October % OFF (17/120 half-staves, 14 because of cooling) several hs ‘cured’ (lower current ⇒ lower power) (P.liq 4 bar, P.gas 1.9 bar)

85 HSs ON 35 HSs OFF (32 due to cooling, 3 due to other issues) 29% of SPD was OFF

12 the SPD performance worsened: no clear reasons for this During the winter shutdown the following equipment was installed: 1 heat exchanger on the plant to undercool the fluid before the pump (to prevent cavitatio) 1 μ m filter after the pump and after the hydro filter 10 connections in PP1 (before the layout of the services was different) ◊ length ∼ 2 m ◊ straightest path than the previous one

clean filter 13 Analysis of a filter removed from PP4 (it had been in place for ~ 1 year) Results and conclusions: “In the used filters several exogenous fragments were located clogging the filter. There were several fragments containing different composition elements. In addition to elements from the Stainless steel, the following traces of elements were found: O, Al, K, C, Sn, Cu, P, Ca, Cu, Na, Cl and Zn.”

1.Liquid pressure increased line by line: the performance improved as the flow increased; 2. Lines swapping: a ‘good’ performance input line was connected to a bad sector and vice versa to test what happened before the detector (slight improvement on temperatures with regard to the original) 3. One input line was replaced (inox, non-insulated) with: ● a plastic input line ● insulated multi-layer pipes (no proven effects) 4. “Ice age” test 14

15 An ‘intercooler’ was installed on the freon line in PP4 (close to SPD) 8 m of plastic pipe in a bucket filled with ice freon reached ~8 °C in PP4 test done on 2 bad sectors (#6 and #5) Observed: increase of flow in one case ( ∼ 50%) clear improvement of performance:  in both cases 6/7 half staves were recovered !

 Clear low flow rate in the bad sectors (best guess: filters in PP3 partially clogged); Consequent steps:  new liquid-side pipes were installed (shorter, less elbows)  new heat exchangers in PP4 were installed to cool the freon close to the detector  Filters in PP3 were cleaned: C6F14 was flushed in the opposite direction  Possible unfavorable thermodynamic conditions due to the inlet temperature in PP4 (partial evaporation of freon before the capillaries); 16

view from side A (front) side ‘I’side ‘O’ 5HX5HX 10 New pipes 5HX5HX ~ 10 ˚C ~ 20 ˚C ~ 10 ˚C 5 pipes

100 HSs ON and stable (average temperature 30.5 °C)- 20 HSs OFF (17 because of cooling, 3 other issues): 83 % of SPD was ON A C After cleaning (24h/sector), new liquid-side pipes path and new heat-ex s installed = 15 more HSs turned on (out of 32) OK Hot Other issues 19

Pressure regulators: Swagelok KPR series, stainless steel with dedicated “peek” gaskets; ● Adjustable pression: bar Flow-meters: Bronkhorst ‘Mini Cori Flow’: Coriolis Principle of operation ● 0.08 to 8 g/s Precision : 0.2% 20

150 W/sector~1.8 g/s 22 The needed flow was calculated (safety factor= 2)

Very low flow rate in sectors 7 and The flow had to be fine tuned sector by sector 23

108 HSs ON and “stable” (average temperature 29.4 °C); 12 HSs OFF (10 due to cooling, 2 due to other issues); February A C OK Hot Hot&Other Other issues 24

-11% of flow in 2 months To vacuum the bad loops before the restart can help to recover the flow

94/120 hs on (78%) last update December 2010: 90 hs on (75%) Power distribution Nominal: 12.5 W Temperature distribution Average: ∘ C (design: 25 ∘ C)

The system worked in the laboratory:100% efficiency, safety factor ~2 Reduced performance once in experimental area (few differences w.r.t. the lab installation): 1) piezometric head 2) inline filters Reduced performance possibly due to: inline filters local thermodynamical conditions close to the detector One possible highly effective cure: take out the filters 27 Setup a test bench to reproduce this behavior and determine any possible reason to justify an expensive intervention in the experiment

Reynold’s number vs. pressure 2300