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Novel Powering Schemes for the CMS Tracker Upgrade - R&D at RWTH Aachen University Meeting of the Joint Atlas/CMS Powering WG 7th of April, 2008 Lutz Feld, Rdiger Jussen, Waclaw Karpinski, Katja Klein, Jennifer Merz, Jan Sammet 1. Physikalisches Institut B, RWTH Aachen University

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The current CMS tracker and its powering scheme Plans for R&D at RWTH Aachen University System test with commercial DC-DC converters The converter Setup and methodology First preliminary results Summary & Outlook Katja KleinCMS tracker R&D on novel powering schemes at RWTH Aachen University2 Outline

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Katja KleinCMS tracker R&D on novel powering schemes at RWTH Aachen University3 The Current CMS Tracker 2.5 m 5.8 m Pure silicon tracker: 1m 2 pixel area + 200m 2 strip area 15 148 silicon strip modules, 29 different types 10 Million Strips, 84 Million pixels Operating temperature < -10 C

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Katja KleinCMS tracker R&D on novel powering schemes at RWTH Aachen University4 The Current CMS Tracker Frontend-Hybrid with - 4 or 6 APV25 readout chips - PLL chip for timing - Multiplexer chip (MUX) - DCU chip for control APV25 readout chip: - 0.25 m CMOS - 128 strips per APV - analogue readout - per channel: pre-amplifier, CR-RC shaper, 4 s pipeline - = 50ns Typical strip module Supply voltages: 1.25V & 2.5V for analogue readout and 2.5V for digital control ring Currents per APV: 0.118A at 2.5V and 0.061A at 1.25V Power consumption of 4 (6) APV module including optical conversion: 1.8W (2.7W)

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Katja KleinCMS tracker R&D on novel powering schemes at RWTH Aachen University5 Powering the Current CMS Tracker Total strip tracker FE power consumption: 33kW Total power supplied to strip tracker: 68kW 34kW = 50% is lost in the cables Inside cold volume, 36% is lost in the cables Several modules (typically 8) are powered in parallel Custom CAEN power supply system (EASY 4000) - A3486 AC/DC converter provides 48VDC - A4601/4602 provide 2.5V, 1.25V & bias voltage Copper low impedance cables from racks to patch panel just outside of tracker volume ( 50m) Aluminium or copper multiservice cables from patch panel to tracker structures (few metres) Patch panel

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Significant R&D effort started slowly due to ongoing work for current tracker Strawman tracker designs are being worked out Main focus of current R&D on simulation of strawmen A new big challenge: integration of tracker into Level1 trigger Re-design of readout chip has not yet started future chip parameters not known all system tests on powering schemes still have to be done with APV25 Boundary conditions for powering to be understood - must current cables be re-used? Serious thinking on powering schemes has started about half a year ago; no prejudice for serial powering or DC-DC conversion Tracker power working group is being set up Katja KleinCMS tracker R&D on novel powering schemes at RWTH Aachen University6 CMS Tracker R&D for SLHC

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Lutz Feld: team leader Waclaw Karpinski (+ workshop team): electronics engineer Katja Klein: HGF Fellow (4 years) Three diploma students: Jan Sammet: System test measurements with DC-DC converters Rdiger Jussen: Development and test of radiation hard magnetic field tolerant DC-DC converter (in collaboration with CERN PH-ESE group, see later) Jennifer Merz: Simulation of material budget of various powering schemes Katja KleinCMS tracker R&D on novel powering schemes at RWTH Aachen University7 Working Group at RWTH Aachen University

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No prejudice wrt serial powering and DC-DC conversion investigate and learn about both schemes before decision can be taken DC-DC conversion started Contributions to the development of a rad. hard, magnetic field tolerant buck converter (development of PCB), in coll. with CERN PH-ESE (F. Faccio et al.) Characterization of this custom converter: magnetic field test, irradiation tests Integration into and system test with current & future tracker structures Preparation of setups & first system tests with of-the-shelf converter ongoing In the longer term: study of general system issues 1-step or 2-step conversion? Converter on chip/hybrid/PCB? Interplay with new readout chip etc. Serial powering not started yet Integration of serial powering scheme into current/future tracker system System performance test R&D proposal submitted and approved (Dec.) within CMS Katja KleinCMS tracker R&D on novel powering schemes at RWTH Aachen University8 Plans for R&D at Aachen

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Katja KleinCMS tracker R&D on novel powering schemes at RWTH Aachen University9 A Commercial DC-DC Converter Market survey (W. Karpinski) with main criteria: - high switching frequency small size of passive components - high conversion factor - sufficient current (~ 1A) & suitable output voltages (1.25V and 2.5V) Enpirion EN5312QI (studied) and Micrel MIC3385 (delivered recently) Characteristics of EN5312QI: Small footprint: 5mm x 4mm x 1.1mm f s 4 MHz V in = 2.4V 5.5V (rec.) / 7.0V (max.) I out = 1A Integrated planar inductor with iron-manganese-zinc core Custom rad. hard converter under development, delivery expected for summer start with a commercial of-the-shelf converter to prepare setups, to learn about system behaviour and to gain experience

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Katja KleinCMS tracker R&D on novel powering schemes at RWTH Aachen University10 Integration into CMS End Cap System 4-layer adapter PCB Plugged between Tracker End Cap (TEC) motherboard and FE-hybrid 2 converters provide 1.25V and 2.5V for FE-hybrid Input and output filter capacitors on-board Input power external or via TEC motherboard

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Katja KleinCMS tracker R&D on novel powering schemes at RWTH Aachen University11 Integration into CMS End Cap System Front-end hybrid L-type: Larger flat PCB,1 piece TEC motherboard (InterConnect Board, ICB) S-type: Smaller inclined PCB, 2 pieces

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Katja KleinCMS tracker R&D on novel powering schemes at RWTH Aachen University12 EN5312QI: Inductor & Magnetic Field Tolerance MEMS technology: spiral inductor betw. magnetic cores Decrease of efficiency in magnetic field Total breakdown for fields below 1T (no surprise) Lower magnetic field tolerance for higher duty cycles D D = T on / T = V out / V in Tolerance depends on orientation of converter in field magnet (B < 1.2T) V out = 1.25V Axial: Tangential: B-probe X-ray, U = 35kV, 5 minutes

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Katja KleinCMS tracker R&D on novel powering schemes at RWTH Aachen University13 EN5312QI: EMI Measurements Standardized EMI test setup at CERN (details in talk by G. Blanchot) Standalone test of converter noise (common & differential mode) Different converters and PCB designs can be compared Low noise emission of EN5312QI (only S type measured) Duplication of setup in Aachen has started Common mode Differential mode Load EMI receiver Filters Current probe EMI Setup at CERN

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Katja KleinCMS tracker R&D on novel powering schemes at RWTH Aachen University14 System Test Setup TEC petal with InterConnect Board Four ring-6 modules powered & read out Petal housed in grounded metall box Optical readout Optical control communication Thermally stabilized at +15C Final components (spares) Official DAQ software 6.1 6.4 6.36.2

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Katja KleinCMS tracker R&D on novel powering schemes at RWTH Aachen University15 Effect of Converter (Position 6.4) Pos. 6.4 ---- No converter ---- L type ---- S type Powered via ICB Preliminary Raw noise increases by 5-10% Design of PCB has significant impact Further optimization seems possible

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Katja KleinCMS tracker R&D on novel powering schemes at RWTH Aachen University16 Effect of Converter (Position 6.4) Pos. 6.4 ---- No converter ---- L type ---- S type Powered via ICB Preliminary Broader common mode distribution Huge increase of noise at module edges, APV edges and bad strips effect is not yet understood

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Katja KleinCMS tracker R&D on novel powering schemes at RWTH Aachen University17 Effect of Converter (Different Positions) Pos. 6.2 Pos. 6.3Pos. 6.4 ---- No converter ---- L type ---- S type (Comparison for position 6.1 not possible because L type does not fit) Powered via ICB Preliminary

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Katja KleinCMS tracker R&D on novel powering schemes at RWTH Aachen University18 Common Mode Subtraction ---- Raw noise without converter ---- Raw noise with converter ---- CM calculated per APV (128 strips) ---- CM calculated for 32 strips ---- Linear CM subtraction L Type Powered externally Pos. 6.4 L type Preliminary Additional noise completely subtractable with proper common mode algorithm Noise increase due to higher common mode

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Katja KleinCMS tracker R&D on novel powering schemes at RWTH Aachen University19 Cross Talk L Type Powered externally Pos. 6.4 L type Pos. 6.3 ---- No converter ---- Converter on all positions ---- Converter on 6.4 only ---- No converter ---- Converter on 6.4 Preliminary Performance with converter does not depend on # of modules operated with converter A converter on position 6.4 does not spoil the performance of modules without converter (e.g. 6.3)

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Katja KleinCMS tracker R&D on novel powering schemes at RWTH Aachen University20 Cross Talk Pos. 6.3 Pos. 6.4 Strip number Correlation coefficient Preliminary Study correlations between pairs of strips i, j (R = raw data): Corr ij = ( - ) / ( i j ) No cross-talk between neighbouring modules observed High correlations only within single modules (common mode) With converters on 6.3 and 6.4 Without converters Strip number

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Katja KleinCMS tracker R&D on novel powering schemes at RWTH Aachen University21 Noise versus Input Voltage Pos. 6.4 L type Pos. 6.4 L type Preliminary Mean noise increases with input voltage or conversion ratio g (g = V in / V out ) Expectation for output voltage ripple V out (with duty cycle D = V out / V in ): Mean noise per module Preliminary

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We have started to a programm to understand the issues related to operation of CMS tracker modules with DC-DC converters First measurements with a commercial converter indicate an increase of the module noise due to a higher common mode by up to 10% Increase of edge strip noise to be studied Further optimization of adapter PCB seems possible No indication for cross talk when powering with DC-DC converters Many more interesting measurements are in the pipeline Operation of a complete petal with Enpirion converters Noise injection on silicon modules Micrel converter with 8 MHz switching frequency Integration of EN5312QI with external air coil Combination of DC-DC converter with voltage regulator Hope to start similar studies with custom converter (CERN) this summer Katja KleinCMS tracker R&D on novel powering schemes at RWTH Aachen University22 Summary & Outlook

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Back-up

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Katja KleinCMS tracker R&D on novel powering schemes at RWTH Aachen University24 Different Methods of Powering Pos. 6.4 L type Pos. 6.4 S type ---- No converter ---- L/S type powered externally ---- L/S type powered via ICB; many filter capacitors Preliminary Sensitivity to input voltage ripple to be strudied, but sensitivity seems to be small

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Katja KleinCMS tracker R&D on novel powering schemes at RWTH Aachen University25 Effect of Output Filter Capacitance Powered externally Pos. 6.4 L type Pos. 6.4 S type ---- No converter ---- Standard output filter capacitors ---- Additional 22 F capacitor ---- Additional 100 F capacitor Preliminary Noise can be reduced further by larger output filter capacitances