# Presentation: 394460

## Pixel Fall-Back Options

- M. Gilchriese

## Assumptions

- Fall-back options are needed in case of continued difficulties with the FE electronics or later difficulties with module production and assembly.
- Schedule(time) and funds(cost) are both concerns
- Attempt to maintain continuity of the design - avoid or postpone to latest possible time radical changes in direction.
- Meet the apparent need to have an initial detector capable of “doing physics” ready by July 2005.
- But which might be completed, if necessary, 9-12 months later.
- “Real” LHC schedule likely not known until 2002.

## Scope Possibilities

- 		_Possibility_			   _No. of Modules_		 _%_
- A. Current baseline			 	2146		100
- B. 2 hits(remove Layer 1, 2x3 disks)		1254		  58
- C. Layer 2, 2x2 disks + “double” B-Layer		1618		  75
- D. “Double” B-layer only			 	  650		  30
- E. Current B-layer only				  286		  13
- (B)
- Current B-layer(286 modules). “Fixed” part is 968 modules.
- (C)
- “Double” B-layer(guess total of 650 modules). “Fixed” part remains 968 modules. Roughly current B-layer + another as close as possible in R. “Double” can be inserted from outside ID.
- Of course, one can imagine other scenarios eg. start with (B) and replace with (C), or.........

## Performance

- The 2 vs 3 hit scenario was studied in 1997 with the layout(s) at that time - see INDET-NO-188.
- The desirability of 3 pixel hits was indicated by this study.
- 2 vs 3 hit study should be updated with the most recent layout, material,......
- It would seem premature to study the performance of options C, D or E at this time(is there agreement on this...?)

## FE- Electronics Options/Milestones

- DMILL(87-100%)/HSOI(13-0%)
- If FE-D2 is not complete failure on arrival, what is date for go/no go with DMILL(Kevin.......)
- If FE-D2 good, do we need another “turn”, date for start of (pre) production is(Kevin...)
- DMILL fails
- Certain schedule delay => implement fallback option #1
- HSOI/0.25 micron(ratio not known)
- When do we know if HSOI could meet spec(Kevin...)
- Cost of HSOI option(Gil....)
- If FE-H1good, do we need another “turn”, date for start of (pre)production is (Kevin)
- When do we know if 0.25 micron could meet spec(Kevin..)
- Decision date for fraction HSOI/0.25 micron(......)
- HSOI fails(for any reason, technical, cost,...)
- Very likely more delay => if so, fallback option #2, if necessary.
- Entire project depends on 0.25 micron
- Date for start of (pre)production is(Kevin...)

## Sensors

- Currently way ahead...can this be sensibly slowed if FE delayed?
- Preproduction fab this year and then evaluate through summer test beam in 2001?
- Begin production after yes/no decision on DMILL, first fall back option then known.
- Continue to split non-B-layer from B-layer.
- Tender limitations(Renate....)

## Module Production

- What is needed....
- See notes from Norbert http://www.physik.uni-bonn.de/~wermes select ATLAS and then "descoping_00.ppt”
- My conclusion: should understand in detail what is required to realistically produce all modules(all steps) in 1.5 years.

## Mechanics Implications

- Some slow down is inevitable.
- Mechanics scope must follow critical FE IC decisions.
- Shift _some_ more focus to solving outstanding problems not related to structure - coolant connections, cabling and related termination, module attachment,...........
- Decoupling SCT and pixel thermal barriers will arise again in any option but current baseline.
- Serious design of “double” B-layer can be postponed but is this feasible at all needs to be looked at now(Eric, Marco....)

## Conservative(?) Schedule