Experience with the MVD

Living around the beam pipe

Components, connections, signals, systems

Hubert van Hecke - Los Alamos

1/2 MVD without coverpadsSi strips

MCM

Power/comm board End plates

Living around the beam pipe

• Every year we had to clear the beam pipe

The central magnet is moved every yearThe beam pipe was not where it was supposed to beThe beam pipe is supported in the CM iron/nosecone

Beam pipe

Official supports

Non-official supports

Nosecone

MVD support plate

Understand environment

Provide for easy movement of the NCC halves

or

Ensure that the NCC clears the beam pipe for all positions of the CM

Flanges, supports, bigger diameter

or

Have the supports mounted to the NCC itself

connections and signal paths

silicon strips and pads

Silicon strips5x8 and 5x5 cm256 strips200 um pitch

Silicon pads252 pads (12 cols, 21 rows) 2x2 - 6x6 mm double metal

traces lay over pads simplify connectionsIncur few % crosstalk

silicon to kapton cable

Dry adhesive was used to bond Silicon to KaptonWire bonds were encapsulated in black potting material(clear potting cured but stayed more sticky)cannot inspect bonds visually

kapton cables

6, 8, 14, 19 cm long

0.05mm KaptonTraces: 0.005mm Cu (x .5 area)Ground: 0.005mm Cu (x .1 area)

Kapton cables

The extreme thinness and the (almost) absence of shielding ground planes was driven by the requirement to keep the mass facing the central arms low.

noise pickup in thin cables

Fatal noise levels in the strip detectors

Si

MCM

Do system tests early

MCM

19 chips: 8 32-channel preamp / discriminators, 8 32-channel AMU / ADC, 2 Xilinx, 1 opamp in a 5x5cm package. Produces a digital data packet.

MCM

Low yield, but the ones that worked never failedDiscriminator never workedXilinx programming proved a vulnerability

Need more time for ASIC development have Xilinx programmer in-house

output cable

50 traces, 0.5mm pitch, controlled thickness and width

Analog, digital, reference voltages, 10, 40 MHz clocks, serial controls, data out.

Output cable

MCM to power/comm board

Power/comm board

ZIF connectors, Elco 0.5mm pitch. Rated for 50 open/close, good for much more

Vertical spacing to << 0.5mmLimited space, so made custom toolsfor opening/closing ZIF connectors

160-pin JAE

power/comm to motherboard

Board spacing 9mm

Fixture to hold and push up to 6 160-pin connectors

Trace density in vicinity of the 160-pin connectors forced the motherboard to be 14-layer

motherboard to cablesThe diameter of the MVD enclosure (60 cm) was determined by the area taken up by the cable connectors, not by the actual Si detectors.

Keeping moist air out is necessary if you run the detector below the dew point. Some connectors were very leaky, and required insulating foam barriers.

Signal cables were .05” pitch solid-core ribbons, vulnerable to bending failure. Strain relief clips were iron and not used because of the mag. field

Cables are flexible, bundles are not (recall the yearly uninstall / reinstall) Connectors were on a surface that was not accessible after installation.

Need ALL components designed before starting mechanical design

downstream electronics

Downstream electronics was badly designed and unsupported by the designers.

AIM - Arcnet Interface module: arcnet fiber to copperTCIM - Timing and Control Interface Module: mode bits fiber to copperDCIM - Data Collection Interface Module: data demultiplexing, multiplexing module, copper to fiber

Needed more development time

Need system tests, not just single boards

Need designers to remain on the team (long enough)

Xilinx programmers on the team

conclusions

Need to do complete system tests early

Need electronics systems engineer on the project

Need designers to remain on the project

Need more lead time for many components

(Other than the ones I’ve already marked)