H.J.Simonis, IEKP Uni-Karlsruhe, SuperKEKB meeting, KEK 18.mar 2009 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 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 assumed power consumption: A thinned DEPFET Dummy 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! thick silicon

H.J.Simonis, IEKP Uni-Karlsruhe, SuperKEKB meeting, KEK 18.mar 2009 Now, the problem is the SW Simulation results: The two Institutes use different programms (COMSOL, COSMOS), and come to similar 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)

H.J.Simonis, IEKP Uni-Karlsruhe, SuperKEKB meeting, KEK 18.mar 2009 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 variation of three geometrical parameters (length, thickness, overlap): -10 ºC 0 ºC temperature of 10 ºC the heat-sink 20 ºC length [mm] K thickness [mm] K overlap [mm] K  T goes down! 25 ºC -> 10 ºC

H.J.Simonis, IEKP Uni-Karlsruhe, SuperKEKB meeting, KEK 18.mar 2009 We need measurements to verify the simulations! here - the IFIC-inventory: C. Mariñas, IFIC-Valencia 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) Air-fan to reach the DEPFET matrix and the switchers (Variable speed of air from 1.5 to 6 m/s) Copper heaters simulating SW and DCD power “Pixel” strip with a nickel spray (not used; unsafe) Pt100 resistors Measurements made on a small microstrip detector. The heater is placed in the middle of the sensor. Dimensions 34 x 14 mm 2 x 300  m Measurements made on a small microstrip detector. The heater is placed in the middle of the sensor. Dimensions 34 x 14 mm 2 x 300  m

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

H.J.Simonis, IEKP Uni-Karlsruhe, SuperKEKB meeting, KEK 18.mar 2009 Kapton cable 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= ; CVD-diamond: λ=1600 W/Km thinned DEPFET sensor (1) alu (2) 1.2 mm copper (3) 0.5 mm diamond DCD-Chip The cooling problem can only be solved in accordance with the mechanical structure, which restricts dramatically the possibilities (very little space). - position of the bar: on top of the chips?or simply underneath: (regard spacial restrictions!)

H.J.Simonis, IEKP Uni-Karlsruhe, SuperKEKB meeting, KEK 18.mar 2009 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 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) Heaters simulating 2 DCD in both ends Each chip will be powered ON all the time Heaters simulating 2 DCD in both ends Each chip will be powered ON all the time Array of heaters simulating switchers in one edge. Each chip will be powered ON/OFF sequentially Array of heaters simulating switchers in one edge. Each chip will be powered ON/OFF sequentially

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

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