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Thermal studies for the DEPFET Pixel Detector

Thermal studies for the DEPFET Pixel Detector. IFIC – University of Valencia (Spain) C. Lacasta, C. Marinas, M. Vos IEKP – University of Karlsruhe (Germany) T. Barvich, O. Brovchenko, H.J. Simonis, T. Weiler. The DEPFET pixel system:

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Thermal studies for the DEPFET Pixel Detector

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  1. Thermal studies for the DEPFET Pixel Detector IFIC – University of Valencia (Spain) C. Lacasta, C. Marinas, M. Vos IEKP – University of Karlsruhe (Germany) T. Barvich, O. Brovchenko, H.J. Simonis, T. Weiler H.J.Simonis, IEKP Uni-Karlsruhe, SuperKEKB meeting, KEK 18.mar 2009

  2. The DEPFET pixel system: -> a highly sophisticated tiny apparatus firmly enclosed in the middle of superBelle, needs to get rid of ~150 Watt thermal power First step: look at an individual DEPFET module: Big advantage of DEPFET: the individual pixel is off for most of the time! assumed power consumption: A thinned DEPFET Dummy A Silicon rectangle, 138mm x 15mm;thickness 450μm – active area thinned to 50μm Three sources of power: 1) The DEPFET Matrix 2) The switcher chips 3) The DCD Readout chips thick silicon H.J.Simonis, IEKP Uni-Karlsruhe, SuperKEKB meeting, KEK 18.mar 2009

  3. Simulation results: DCDs are always active: The hottest points T ~ 140 ºC If the DCDs are cooled: only 2 Switchers + 2 pixel rows active: -> still hot! (T ~ 100 ºC) Now, the problem is the SW The two Institutes use different programms (COMSOL, COSMOS), and come to similar results. H.J.Simonis, IEKP Uni-Karlsruhe, SuperKEKB meeting, KEK 18.mar 2009

  4. How can we get rid of the heat: Introduce thermal contact: in this simulation use a strip of aluminum (12x30x1 mm³) at both ends, coupled to a heat sink -10 ºC 0 ºC temperature of 10 ºC the heat-sink 20 ºC T goes down! 25 ºC -> 10 ºC variation of three geometrical parameters (length, thickness, overlap): 330 - 375 K 316 - 350 K 325 - 360 K 20 40 60 80 100 length [mm] 0.6 1.0 1.4 1.8 thickness [mm] 2 4 6 8 10 overlap [mm] H.J.Simonis, IEKP Uni-Karlsruhe, SuperKEKB meeting, KEK 18.mar 2009

  5. We need measurements to verify the simulations!here - the IFIC-inventory: • Cooling blocks at both ends of the silicon • Air-fan to reach the DEPFET matrix and the switchers (Variable speed of air from 1.5 to 6 m/s) • Pt100 resistors • Measurements made on a small microstrip detector. • The heater is placed in the middle of the sensor. • Dimensions 34 x 14 mm2 x 300 mm “Pixel” stripwith a nickelspray (notused; unsafe) Copper heaters simulating SW and DCD power H.J.Simonis, IEKP Uni-Karlsruhe, SuperKEKB meeting, KEK 18.mar 2009 C. Mariñas, IFIC-Valencia

  6. DCD -temperature, as a function of speed of air for 3 Watt of power. (Simulation) T_air = 14 ºC Influence of air flow Switcher-temperature, for different temperatures of the cooling blocks, as a function of speed of air for 1 Watt of power. (Measurement) T_air = 26 ºCcooling Liquid: ■ 26ºC ■ 7 ºC already a moderate air flowimproves the thermal environment significantly! 0 1 2 3 4 5 v [m/s] SuperBelle preKEK Meeting, Valencia, March 2009 H.J.Simonis, IEKP Uni-Karlsruhe, SuperKEKB meeting, KEK 18.mar 2009 C. Mariñas, IFIC-Valencia

  7. first conclusions: glueing aluminum strips to both ends of the DEPFET sensor is not sufficient we need air flow (and more detailed studies about air flow have to be done) Further Parameters have to be investigated: - which material (copper: λ=360; carbonfiber: λ=300-500; CVD-diamond: λ=1600 W/Km - position of the bar: on top of the chips? or simply underneath: (regard spacial restrictions!) (2) 1.2 mm copper DCD-Chip (1) alu Kapton cable thinned DEPFET sensor (3) 0.5 mm diamond The cooling problem can only be solved in accordance with the mechanical structure, which restricts dramatically the possibilities (very little space). H.J.Simonis, IEKP Uni-Karlsruhe, SuperKEKB meeting, KEK 18.mar 2009

  8. Next steps: • MPI produces dummy silicon of different degree of genuineness: • bare silicon slabs for mechanical mockups • thinned silicon slabs for detailed thermal studies etc. • thinned silicon slabs with a structured aluminum layer on top to be close to • the thermal and mechanical behavior of the real DEPFET • Array of heaters simulating switchers in one edge. • Each chip will be powered ON/OFF sequentially • Heaterssimulating 2 DCD in bothends • Each chip willbepowered ON allthe time Another important point: Once the heat is out of the sensors – how do we dissipate the power from the support structure? The most elegant method is to delegate this to the cooling of the beam pipe  the IR-group should be aware of the additional power (~150 W) H.J.Simonis, IEKP Uni-Karlsruhe, SuperKEKB meeting, KEK 18.mar 2009

  9. Backup H.J.Simonis, IEKP Uni-Karlsruhe, SuperKEKB meeting, KEK 18.mar 2009

  10. H.J.Simonis, IEKP Uni-Karlsruhe, SuperKEKB meeting, KEK 18.mar 2009

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