WACH4 26/11/2002 Julien Cogan CERN/EP/CMA-1-

M0 COOLING IN H4• Cooling is a key issue :

– APD gain : ~ -2.4 % / C– XTAL response (scintillation) : ~ -1.9 % / C(“nominal values” from “old” measurements)

• Strict requirement :– contribution to (E)/E : < 0.5 %

– avoid to apply correction constant temperature of XTAL & APD : 0.05 C

• Goals in H4 this year :– provide stable conditions for the data taking

– validate some cooling principles for the future (cooling units, VFE cooling)

– better understanding of the system

• heat transfer (electronics ADPs & XTALs)

• dynamic of the system (characteristic time constant of ADPs & XTALs)

WACH4 26/11/2002 Julien Cogan CERN/EP/CMA-2-

OUTLINE• M0 cooling :

– mechanic

– cooling units & circuits

– next year strategy

• Thermal stability during the data taking :– water circuits

– environment

– APDs (capsules)

– failures

• Thermal studies (covered in next talks)– heat transfer, temperature rise when electronics is turned on (P. Baillon)

– temperature steps (Roberto Salerno, J. Cogan)

WACH4 26/11/2002 Julien Cogan CERN/EP/CMA-3-

COOLING MECHANIC (1)• Bare module = fully equipped module with 400 crystals

– final grid (cooled through 9 holes drilled along z)

– thermal shield ( attached to the APD connector mechanical assembly 10 lines)

– special thermal screen (2 layers of pipes around the 5 faces of the crystal basket)

– module isolated from its support by 4 cooled blocks of aluminum

– module isolated from the environment by 4 cm of rock wool

WACH4 26/11/2002 Julien Cogan CERN/EP/CMA-4-

COOLING MECHANIC (2)• Electronics = 20 VFE cards 10 blocks 100 channels

– FPPA + ADC + GLINK (+DRIVER) ( ~2.5W/Ch)

– copper housing manufactured to compensate for the different height of the components (minimal thickness = 0.7 mm)

– 0.5 mm thick gap pad between the copper housing and the components + contact at the bottom of the cards (1 mm thick 4 mm wide gap pad)

– 10 lines of cooling pipes ( 3/4 mm) brazed on the copper housing

WACH4 26/11/2002 Julien Cogan CERN/EP/CMA-5-

COOLING UNITS & CIRCUITS (1)

WACH4 26/11/2002 Julien Cogan CERN/EP/CMA-6-

COOLING UNITS & CIRCUITS (2)• Regulating circuit : flows through the grid and then on the thermal shield

– q = 0.22 l/s (80 % of nominal flow) T(OUT-IN) typically few 1/100 C– water regulation and circulation done by a LAUDA

• Ambient circuit : flows in the thermal screen and on the insulating al. blocks

– q 0.1 l/s T(OUT-IN) typically few 1/10 C– water regulation and circulation done by a LAUDA

• Power circuit : cools the VFE boards

– q 0.14 l/s (M0) (+ ~0.14 l/s by pass) T(OUT-IN) typically few 1/10 C ; P 1.5 bar

– water under pressure (P~2.5 bar)

– water regulation and circulation :

• heat removal : chilled water + heat exchanger

• water regulation : heater (max = 2kW) controlled by a regulator (PID)

WACH4 26/11/2002 Julien Cogan CERN/EP/CMA-7-

NEXT YEAR STRATEGY• Cooling circuit : only one circuit

– cooling unit similar to this year power circuit

– work is in progress (dimensioning of the circuit, buying of the elements, control loop)

• Cooling of the electronics (is being decided)– from cooling point of view : same principle as this year (?)

– mechanically : cooling bars instead of brazed tubes (?)

– introduction of a mother board and additional kapton cables between the VFE and the APD connector

PID

Simplified schematic of the foreseen cooling unit

Mixed water

14.5 C

17.8 C

18.8 C

17.8 C

WACH4 26/11/2002 Julien Cogan CERN/EP/CMA-8-

SHORT-TERM STABILITY : WATER (1)Regulation circuit Power circuit

INLET

INLET

OUTLET OUTLET

0.05 C

1 week

WACH4 26/11/2002 Julien Cogan CERN/EP/CMA-9-

LONG-TERM STABILITY : WATER

0.05 C

Regulation circuit Power circuit

INLET INLET

OUTLET OUTLET

3 months (aug/sept/oct)

2 o’clock jumps

Lauda remote control off Power cut

?

WACH4 26/11/2002 Julien Cogan CERN/EP/CMA-10-

STABILITY : ENVIRONMENTRoom

(measured on a copper plate near the module)MEM

(output water temperature)

2 C3 months (aug/sept/oct)

1 C

Ambient circuit (inlet & outlet)

2 C

0.5 C

Primary circuit (inlet)

out of water

WACH4 26/11/2002 Julien Cogan CERN/EP/CMA-11-

STABILITY : CAPSULES

3 months (aug/sept/oct)

0.1 CLV block A

LV block B0.1 C

WACH4 26/11/2002 Julien Cogan CERN/EP/CMA-12-

STABILITY : FAILURES• Laudas remote control :

– setting of the Lauda controlled by a computer (to be able to change the temperature form the control room)

– induce instabilities and mysterious jumps ( ~0.02C) at 2 AM (related to computer activity ?)

– remote control disabled after 2nd temperature step (16/08/02) : small change in the setting (~0.02C )

• Chilled water failures :– Pb with chilled water in the area happened twice (last for less than 1 day) :

• 12/08/02

• 23/09/02

– induced a rise of temperature of the power circuit (~1C )

– induced a small rise of temperature on the APD

WACH4 26/11/2002 Julien Cogan CERN/EP/CMA-13-

CONCLUSION

• STABILITY : – Generally good thermal stability during all the data taking :

• constant temperature of the cooling water well within 0.05C

• constant temperature of the capsule well within 0.1C Probably no need to correct for temperature effect

– Very few failures

• M0’ cooling system :– validation of some principles for :

• cooling units

• VFE cooling

– give confidence for the future