1. CMS Upgrade Meeting @ CERN April 27, 2010 W. Bertl PSI Power & Cooling: Design Status of BPIX

2. CMS Upgrade Meeting @ CERN April 27, 2010 W. Bertl PSI BPIX Upgrade Goals:Schedule: Improve tracking precision >2014 –More hits / track → add a 4 th detection layer (Phase I) –Innermost layer closer to IP (smaller beam pipe!) –Less material to obstruct tracks –Full digitization at the detector ( → ROC modification) Adapt for higher luminosity (>2*10 34 cm -2 s -1 )>2017 –→ requires new ROC design to keep efficiency high (Phase II) –power and cooling concept likely to be reworked

3. CMS Upgrade Meeting @ CERN April 27, 2010 W. Bertl PSI Implications of a 4 th layer # of modules increase (from 768 to 1216) → need for more power → need for more readout channels → new design to keep material budget low → cooling reconsidered

4. CMS Upgrade Meeting @ CERN April 27, 2010 W. Bertl PSI More Power for BPIX Modified ROC (full digitization, higher read-out bandwidth, buffer size, but no changes in analog and column part, some simplifications of present design) : Assumption: Power consumption equal: Modified ROC ↔ Present ROC Ianalog = 25.4 mA / ROC Idigital = 27.35 + 0.17 * #Hits[MHz/cm 2 ] mA/ROC BPIX Detector power (L=10 34 ): 1612 W (2008) → 2576 W (2014) (+60%) Power Cables: replacement/upgrade virtually impossible ! →→ BPIX Cable losses (L=10 34 ): 1540 W (2008) → 3887 W (2014) (+152%) BPIX Supply power ( “ ): 3150 W (2008) → 6444 W (2014) (+105%) Very inconvenient ratio used/wasted power) ! Cable losses could result in thermal overload in cable trays Present power supplies unable to fulfill request Doubled luminosity: cable losses increase by >200% ►use DC-DC-Converter

5. CMS Upgrade Meeting @ CERN April 27, 2010 W. Bertl PSI DC-DC-Converter Mounted on outer end of service tube (close to PP0) What conversion ratio ? LumiConv. Ratio* Long Cable loss Total Power PS Power max PS Curr. max PS Volt. max Conv. Curr. max 2x10 34 21590 W6070 W108 W8.6 A8.6 V4.9 A 2x10 34 3707 W5188 W89 W5.7 A10.7 V4.9 A 2x10 34 4398 W4879 W83 W4.3 A13.3 V4.9 A 4x10 34 4566 W6683 W114 W5.6 A15.7 V7.9 A * Converter efficiency: 80% ↑ limit:120 ↑ limit:14 ↑ limit:10.5V Phase I : Ratio 2 chosen → present PS o.k. Phase II : replace converter with ratio>2, replace PS Aachen: converter development based on Cern-ASIC. Test with modules soon!

6. CMS Upgrade Meeting @ CERN April 27, 2010 W. Bertl PSI Summary: BPIX power If I presentROC ~ I newROC and ε converter ~ 80% Then (*) present CAEN power supplies can be used up to L=2x10 34 (minor mod.) 2:1 Converter developed in Aachen/Cern fit on service tube converter output 4.9A ev. to high, can be solved by changing assignment converter test with 4 real modules connected to CAEN PS in preparation ► stability/noise test under realistic load conditions Else modify power supplies to deliver higher voltage Converter with higher ratio to be developed (*) should be known in one year from now

7. CMS Upgrade Meeting @ CERN April 27, 2010 W. Bertl PSI More read-out channel Read-out: increase bandwidth from 40 to 320 MHz (full digitization on module!) One fiber/module is sufficient for L<2x10 34 (presently layer 1&2: 2 fibers/module) ►increase of fibers from 1184 to 1216 Contrary to the number of power cables there exist (4) multiribbon spares New lasers with new fibers required for service tube Few additional FEDs required, all FEDs upgraded to 320 MHz ► new piggy board developed in Vienna

8. CMS Upgrade Meeting @ CERN April 27, 2010 W. Bertl PSI Material budget 768 modules (3 layer)1744g23% mechanics (no pipes)1607g21% cooling (pipes,C 6 F 10,manifolds)2245g30% cables, prints, connectors1990g26% Present BPIX (detector only) 7586g100% Service tube (up to z=820mm)9308g 1216 modules (4 layer)1738g48% mechanics (no pipes)728g20% cooling (pipes 1.4mm, CO 2 )705g20% cables, prints, connectors429g12% 2014 BPIX (detector only) 3599g100% Service tube (up to z=820mm)1632g Scaling detector to 4 layers: ~13000g (w/o ST) (with ST: ~ 4.4 * BPIX 2014 !!!) 2014 BPIX w C 6 F 10 cooling: ~6800g (w/o ST) (53% of weight devoted to cooling !) Total mass within η = 2.17: 16894g (3.3 * more) Total mass within η = 2.17: 5231g

9. CMS Upgrade Meeting @ CERN April 27, 2010 W. Bertl PSI

10. CMS Upgrade Meeting @ CERN April 27, 2010 W. Bertl PSI CO2 Two-phase Cooling Substitution of CO 2 for C 6 F 10 gains ~3.2kg on detector weight and even more if service tube is also considered. How is this possible?High latent heat → low mass flow Micro sized pipes (d i =1.4mm) can be used density = 1.03 g/cm 3 long loops can be used → no manifolds needed Further advantages:radiation hard low liquid/vapor density ratio low viscosity high heat transfer coefficient cheap Problems:high pressure on supply pipes at room temperature (60bar) two-phase flow in micro tubes difficult to calculate

11. CMS Upgrade Meeting @ CERN April 27, 2010 W. Bertl PSI Difficulties with CO2 Cooling High pressure: Supply tubes through CMS reach elastic limit at 150bar → o.k. for 60bar Lancashire fittings between PP1 and PP0 must be replaced Flow calculation:Evaporating liquid changes flow pattern with increasing heat transfer Pressure drop is driven by frictional loss which depends on flow pattern no adequate theoretical model seems to exist for our setup But our composition of parallel cooling loops require reliable pressure drop calculations for variable operating conditions: different loop length; beam on/off; operating temperature; luminosity etc.

12. CMS Upgrade Meeting @ CERN April 27, 2010 W. Bertl PSI Cern meas. vs Friedel correlation T= -20 [C] | X= 0 % | P= 223 [W] | m= 1.5 [g/s]

13. CMS Upgrade Meeting @ CERN April 27, 2010 W. Bertl PSI

14. CMS Upgrade Meeting @ CERN April 27, 2010 W. Bertl PSI Summary Cooling CO2 cooling could save more than 3 kg of material budget Test setups have been studied at Cern, Lyon, Aachen demonstrating that e.g. 220W on a 5.5m long pipe (d=1.5mm) can be handled But it turned out difficult to explain the measurements by calculations. This is needed to prove that all conceivable operation modes can be handled without a local cooling deficit. Further studies/tests needed: optimize carbon fiber material concerning heat transfer large pressure drop results in a drop of saturation temperature (up to ~12°C) → thermal stress on modules! flow parameters for supply pipes to be determined stability of prototype cooling plant with realistic pipe layout / load