1. Rosario Turrisi INFN Padova
SPD-cooling status
Rosario Turrisi
INFN Padova

2. Foreword: working principle
Evaporative system
Joule-Thomson cycle: sudden expansion + evaporation at constant enthalpy
Fluid: C4F10
Dielectric
Chemically stable
Non-toxic
Temp [°C]
Pres [bar]
16.0
1.99
20.0
2.28
22.0
2.43
26.0
2.77
liquid pressure ≡ flow
gas pressure ≡ temperature

3. Simplified schema 2 filters (60 μm) before SPD, in PP4, PP3
Detector side
2 filters (60 μm) before SPD, in PP4, PP3
Read-out of p,T per line up- (PP4) and downstream (PP1) the detector
Detector side not accessible, except PP4, PP1
Plant side

4. Actions taken
Additional heat exchangers to further subcool the fluid close to the detector
10 HX’s (one per line), redundant exchange factor (more than 5 times)
use leakless system with water cooled down at 7.5 °C
Installation of new liquid-side pipes
dedicated path of new lines, more straight (less elbows), shorter
inox SS316L, 6/4 o/i diameter (same as before) - no insulation (useless)
Flushing each line counter-flow wise
drain particles clogging the filters outside the line
redundant protection against overpressure: 2 safety valves (mechanical) + pressure switch (electronic)
2 filters, stainless steel, 1 μm grid, on the “washing machine”
24 h washing cycle per each sector

5. Room for improvement? From LHCC meeting November 16
Out of 10 “missing” 9 half-staves have cooling issues
Beyond the number of hs, SPD needs also stability
Following actions need to be taken on solid base, understanding the behaviour in running conditions (lots of variables play...)
Actions for the short term:
remote control of water flow
installation of per-line flowmeters and pressure regulators
repeat the cleaning on worse sectors (7,9) for longer time
not needed
The real schedule is of course dependent on when/how long we’ll have access to the experimental area...

6. ‘Ice age’ test #2
We wanted to verify if subcooling the freon can help the performance on “critical” sectors (#7 & #9)
We installed in PP4 (close to SPD) ~8 m of plastic pipe in a bucket filled with snow
freon reached ~8 °C in PP4
Test done on the two worst sectors (#7 and #9)
No significant change of the performance observed
Values of the bus current
for the 6 hs of side A
- missing means off

7. Measurement of flow good bad flow [g/s] p [bar]
We measured the flow on a few sectors with a single flowmeter (on a common line)
Better understanding of the performance can be achieved measuring the flow (and then the impedance) by a non evaporating fluid (we’ll use C6F14)
Special care to be taken, the non- evaporative flow prevents control of the pressure inside the detector but by regulating the input
Will be done as soon as we can have a reliable readout of flow and the cleaning of the “bad” sectors is done (use the same device)
flow [g/s]
good
p [bar]
bad

8. New hardware - 1 Pressure regulator on each line:
allows a dedicated tuning of liquid pressure → flow
Flowmeter on each line:
allows the monitor of the flow → fundamental for performance monitoring along the lifetime of the system and debugging of possible problems
Hardware installation completed (sensors + cabling)
Readout system close to completion (next week), integrated in DCS

9. New hardware -2
Pressure regulators: Swagelok KPR series, stainless steel with dedicated “peek” gaskets
Flowmeters: Bronkhorst ‘Mini Cori Flow’:
very expensive but necessary to handle the low flows of SPD
based on Coriolis-forces effects, no needles/balls/whatever in the fluid path

10. A few pictures...

14. Planning
to week 4
Commissioning delayed to week 4 (25th-29th Jan)
to allow longer cleaning of sectors #7 and #9
today

15. Critical tasks today to week 4
Commissioning delayed to week 4 (25th-29th Jan)
to allow longer cleaning of sectors #7 and #9

16. Summary Hardware upgrade of the system completed
A few maintenance interventions to go
Cleaning of the worst lines ongoing (sects. #7 & #9)
By the end of January:
measurement of the flow with non-evaporating fluid
commissioning