Cables connectors z Signal inventory ysignal types characteristics

Cables (/connectors) z. Signal inventory ysignal types / characteristics yextra signals of pile-up z. Types of cables ytwisted pair vs. striplines y. Cable test z. Other (open) issues ygrounding & shielding ybuffering on flange

vacuum Scta beetle air Optional buffer unshielded 1. . 2 meter Receiver in racks shielded 10. . 15 meter

Signal inventory z. Low voltage power lines z. Analog outputs z. Digital control (lvds / cmos) z. Digital outputs (lvds, pile-up only) z. Other signals ydetector bias ytemperature sensors

Low voltage power z. Simple calculation: y 1/2 wheel = 16 frontend chips y 16 * 500 m. W = 8 Watts y. If Vdd = 2. 5 volts => I= 3. 2 Amp z. Copper area needed > 1 mm 2 ycooling? y 1 meter = 170 m. W

Analog output signals z. Balanced output pair yfew hundred millivolts for 10 Mip signal y. Bandwidth >> 40 MHz ysensitive to pickup z 4 pairs per frontend chip

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

LVDS Driver: Receiver: 250 m. V into 100 ohms 100 m. V differential Maximum cable attenuation = 8 d. B (Z 0 = 100 ohms)

Digital outputs z. Pile-up comparator outputs z. LVDS @ 80 Mbit y 16 pairs per frontend chip, 256 for 1/2 wheel yextra connectors on hybrid needed

Other signals z. Bias for detector yhigh voltage, upto 500 Volts ? ylow current z. Temperature sensors yspecification depends on sensor type yno-high speed, low current… y 1 sensor for 1/2 wheel

Summary

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

Cable “specifications” z. Cable impedance ygeometry ydielectric constant of isolation (~ 3) z. Loss y. DC resisitive loss ylosses due to skin effect, proximity effect ydielectric loss z. Dispersion

Cable losses Wire resistance Skin depth Dielectric loss dispersion ~1. 7 per meter for 0. 01 mm 2 ~10 m @ 40 MHz low for good dielectrics

Example z. Diameter 0. 1 mm y. Rdc = 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

Impedance of cable d Twisted pair D For kapton Z 0 ~ 100 ohms if D = 2*d Microstrip line w s w See figure h

Grounding /shielding z. Questions y. Central (star) ground, where yshielded cables upto flange yvacuum cables run close to machine ground

Buffering z. Rad-hard components zcooling problem