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Published byCarlee Hightower Modified over 2 years ago

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Cables (/connectors) zSignal inventory ysignal types / characteristics yextra signals of pile-up zTypes of cables ytwisted pair vs. striplines yCable test zOther (open) issues ygrounding & shielding ybuffering on flange

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Scta beetle Optional buffer Receiver in racks 1.. 2 meter10.. 15 meter vacuum air unshieldedshielded

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Signal inventory zLow voltage power lines zAnalog outputs zDigital control (lvds / cmos) zDigital outputs (lvds, pile-up only) zOther signals ydetector bias ytemperature sensors

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Low voltage power zSimple calculation: y1/2 wheel = 16 frontend chips y16 * 500 mW = 8 Watts yIf Vdd = 2.5 volts => I= 3.2 Amp zCopper area needed > 1 mm 2 ycooling? y1 meter = 170 mW

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Analog output signals zBalanced output pair yfew hundred millivolts for 10 Mip signal yBandwidth >> 40 MHz ysensitive to pickup z4 pairs per frontend chip

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Digital control lines zLVDS (low voltage differential signalling) yclock, trigger, reset yfrequency: 40 MHz yline termination needed yclock / trigger per 4 / 8 / (16) chips zCMOS-level yI 2 C interface ylow frequency yline termination optional (series termination) yone set of signals for 1/2 wheel?

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LVDS Driver: 250 mV into 100 ohms Receiver: 100 mV differential Maximum cable attenuation = 8 dB (Z 0 = 100 ohms)

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Digital outputs zPile-up comparator outputs zLVDS @ 80 Mbit y16 pairs per frontend chip, 256 for 1/2 wheel yextra connectors on hybrid needed

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Other signals zBias for detector yhigh voltage, upto 500 Volts ? ylow current zTemperature sensors yspecification depends on sensor type yno-high speed, low current… y1 sensor for 1/2 wheel

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Summary

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Cable requirements zvacuum compatible zradiation hard zmoderate signal loss zflexible zthin zcharacteristic impedance of 100 ohms zpolyimide (kapton) isolation

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Cable “specifications” zCable impedance ygeometry ydielectric constant of isolation (~ 3) zLoss yDC resisitive loss ylosses due to skin effect, proximity effect ydielectric loss zDispersion

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Cable losses Wire resistance ~1.7 per meter for 0.01 mm 2 Skin depth ~10 m @ 40 MHz Dielectric loss low for good dielectrics dispersion

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Example zDiameter 0.1 mm yRdc = 1.3 / m yskin loss @ 40 Mhz adds a factor 2.5 y~20% signal loss for 2 meter zsame copper area for stripline (35 m Cu) ywidth = 0.225 mm yskin loss @ 40 Mhz adds a factor 1.5 y~13 % signal loss for 2 meter

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Impedance of cable D d For kapton Z0 ~ 100 ohms if D = 2*d Twisted pair h wsw Microstrip line See figure

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Grounding /shielding zQuestions yCentral (star) ground, where yshielded cables upto flange yvacuum cables run close to machine ground

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Buffering zRad-hard components zcooling problem

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