# Presentation: 410685

## Pixel Layouts

- On behalf of many contributors
- Pixel General Meeting
- October 2, 2000

## Current Baseline Layout

## Rapidity Coverage Z=11cm

## Baseline Layout

- SCT Forward
- Envelope

## Reduced Layout

- To cope with delays in rad-hard electronics and possibilities of other future delays.
- A reduced layout was proposed - see next pages
- Respected current envelopes, in particular forward SCT bore of R=110mm.
- Maintains possibility of 3-hit coverage
- Keeps mechanical design concepts same as baseline
- But decreases “fixed” part to be inserted into SCT/TRT barrel in Sprin 2004(current schedule) and
- Increases insertable/removable part - “double B-layer” - that can be installed later(about one year) and removed during short access configuration.
- Proposed at Inner Detector Steering Group(IDSG) meeting on September 7.
- Reaction was to request study of fully-insertable option
- requires change in SCT envelopes and SCT barrel thermal barrier
- requires reduction in pixel outer envelope
- requires modification to pixel installation plan and services routing(services must exit both sides for part of system).
- Preliminary study of this possibility completed and presented here.

## Proposed Reduced Layout

## Reduced Layout - Barrel End View

## Reduced Layout - Side View

## Reduced Layout Rapidity Coverage Z=11cm

## Material

## Minimal, 2-hit Fallback

- Continuous black lines: nominal active area
- dotted black lines: largest active area radius

- 770

- Double B-layers + 2x1 disk

## Proposal for Insertable Layout

- Complete clam shell not necessary if beam pipe at end ID is not present
- During initial installation or Long Access configuration  liquid argon endcap is pulled back => beam pipe is broken at end of ID.
- Clam shelling of B-layer is always necessary to clear beam pipe flange
- Shrink pixel envelope
- Global support frame is not clam-shelled but reduced in radius
- Staves same and Barrels same in design but different radii
- Disks must be reduced in radius, number of sectors. Open gaps of about 2.3% and 3.8%, averaged over disk, for 9 and 8 sector disks, respectively.
- B-layer is the same. Module same
- Non-B-layer services exit both ends....much more complicated installation.

## Insertable Layout

## Fully Insertable(9-8-8 disks)

- Barrel-to-disk two hit hole

## End View

- 1/2 B-Layer services

- Nominal clearance

- Minimum clearance

- Fittings clear ears

- ENVELOPE

- Frame outer radius

- Disk outer radii

- This assumes non-B-layer
- services exit from both
- ends of inner detector
- if services must exit one
- side then add about 10mm

## Elevation View

## Perspective View

- Barrel Services need to be reduced in width to fit through and on a narrower panel
- Only 4 less staves than in baseline, so 4 octants have the same number of barrel services as baseline but in less space.
- 9-sector disk for first disk to reduce acceptance losses
- Considerable uncertainties remain in services => this is not a conservative layout.

## Coverage Z=11cm

- 2.3% for 9 sector

## Preliminary Material Estimate

## Simplified Schedule Comparison

- Assumes 40 modules/week, 75% module yield.

## Schedule Impact on Mechanics

- Rough estimate of impact on mechanics schedule _relative to current baseline_
- Reduced layout
- No delay in starting on local supports and global support frame
- Double B-layer likely more difficult but work just started in any case in this area, long time for design => likely no delay.
- Insertable layout as we propose
- Depends critically on ability to do quickly joint design of forward SCT thermal barrier and rails to freeze dimensions and acceptance by ATLAS of consequences of insertable system.
- Considerable uncertainty. (eg. prototyping rail system) may be on critical path for mechanics.
- Rough estimate is 6 months delay.
- Insertable layout with complete redesign(ie. fully clamshelled)
- Delay independently estimated by Marco, Eric and Bill to be _two years+_

## What Ifs for Insertable Layout

- We were asked...what if
- Considerable uncertainty.......need to be prudent...
- Reduce pixel envelope further by 5 mm(from 230 mm to 225 mm)
- drop 9-sector disk for 8-sector disk. Loss(2 hits rather than 3 hits assuming 100% efficiency) goes from about 0.8% to 2% of tracks.
- increased risk of violating services envelope
- Reduce pixel envelope by 10 mm(from 230 to 220 mm)
- go to 2 hit layout

## Fully Insertable(8-8-8 disks)

- Barrel-to-disk two hit hole

## SCT-Pixel Envelope Clash

- Pixel envelope R=230

- SCT envelope R=237

- Assumption is that 15 mm
- needed between SCT and
- Pixel envelopes.
- Current SCT and Pixel
- envelopes clash by about
- 8mm. Need detailed work
- to see if this can be solved

## SCT-Pixel Envelopes

- Pixel envelope

- SCT thermal barrier

- SCT disk

- Currently 7mm - need 15mm minimum

## Possible Choices

- A) Reduced layout
- proceed on current schedule for mechanics
- if delay in ICs and later module production => 2-hit layout and major intervention required for 3-hit system or later replacement.
- B) Fully insertable layout as proposed by pixel community
- delay mechanics schedule until SCT/pixel envelopes and impact of services running along SCT bore understood. Delay in mechanics roughly 6 months but uncertain.
- Primary risk is that cannot solve SCT-pixel clash for 3 hits=> 2 hit pixel system.
- C) Other fully insertable layout(fully clam-shelled structure)
- complete(unknown) redesign. Two-year+ delay in mechanics.
- _Not acceptable_