Design Discussion of Mechanical / Electrical Interfaces

Bill Cooper (Fermilab)

(Layer 1)

VXD

From Marvin Johnson’s October 2009 Talk

• Don’t need full bandwidth over entire rod– Rate drops by half at half

distance from IP in inner layer

• Design optic chip with 4 inputs

– use one chip to read 4 half sensors in outer part of inner layer

– one chip per 8 half sensors in outer layers

• Connector through carbon f rod

– Minimizes mass

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Green is carbon fiber supportYellow is sensorRed is interposerBlue is read out chip

Tan is Kapton bussGreen-red is DC-DCCyan is fiber driver

By pass caps

Changes from earlier Drawings

• Interposer details– Propose that they be changed to be consistent with a symmetric

silicon interposer for the moment– Modify that as more information becomes available.

• Note that the drawing assumed connectors at interposers.– Propose that connectors move to cable juncture with CF, as

Marvin has shown.

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Connector

Change from asymmetric to symmetric interposers to allow cables from left and right edges

Move connector to this region

Changes from earlier Drawings

• Cooling tubes were assumed to be stainless steel and drawn as 2 mm OD,1.3 mm ID last April.– Propose changing that to 2.3 mm OD, 1.8 mm ID aluminum.

• Features to support and method to install DC-DC converters and feed through power need to be developed.

• Fiber optic connectors and fiber mounts need to be developed.

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Provide features for mounting and installing DC-DC converters and feeding power through.

Change size and material of cooling tubes

Provide mounts and feed-throughs for fiber optics.

Module Installation and Grounding

• Clear regions will be needed at edges to hold modules in place.

• Provisions for grounding will be needed.– Carbon fiber laminate can provide a good high frequency

connection.– In the past, we’ve used co-cured copper mesh on kapton to

allow a connection.

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Module fasteners

Space for module fasteners needs to be preserved.

Grounding Starting Point

• In the absence of specific measures, CF laminate pieces will not be well-connected electrically.

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3 electrically separate CF pieces

Electrically separate CF pieces on two module surfaces

Electrically separate cooling tubes

Possible Grounding Assumptions

• What should be the electrical connectivity of the various carbon fiber laminate pieces? How is it achieved?

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Connections between each module and box via flex-circuits

Common ground for the two CF pieces and interposer of a module

Do we need explicit electrical connections between the flanges and the box?

Copper Mesh on Kapton

• For D0 L0, almost all of the CF support cylinder was covered with co-cured mesh copper on kapton. – A circuit at each sensor connected the sensor ground to

the cylinder ground.– A ground connection was also made between each

readout hybrid and the cylinder.– The cylinder coverage may have been more extensive

than necessary.• For CMS, is it sufficient to cover a local region of the

cylinder at each module?• Is gold-plating plus modest pressure sufficient to provide

a reliable electrical connection? That would simplify module installation and removal.

• Testing will needed.

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D0 L0 Copper Mesh Circuits

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Sensor region Hybrid region

Analogue flex-cables connected sensors to hybrids.In the sensor and hybrid regions, each mesh circuit covered roughly 180o of circumference.Sensor and hybrid mesh circuits were connected with three jumpers.Two of the three jumpers also connected the two mesh circuits of a region.

Proposal

• Start with a CF box structure of length at least 650 mm.– That covers z-locations of three sets of modules.

• Provide three pairs of local copper mesh circuits with two circuits to cover 360o.

• Measure impedance versus frequency from circuit to circuit to determine whether circuits should be larger (in z).

• Connect circuits with jumpers if measurements show that to be desirable.

• Provide features to allow connections to DC-DC converter grounds and to flex-cables from modules.

• Populate with modules and test when modules are available.

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A Reminder of the Rod Mechanical Fabrication Sequence• Each piece needs to be prototyped and tested.• The assembly needs to be prototyped and tested at each stage.

Track Trigger Meeting – 12 January 2010