1. Aron Fish Imperial College Mice Video Conference 01/02/06
Tracker Autopsy
Aron Fish
Imperial College
Mice Video Conference
01/02/06

2. Disassembly, Mapping & Mirroring
The Tracker prototype has now been disassembled at Imperial, checks have been made on all possible damage, loose connections of waveguides and mapping information and the search for the ~30% loss of photons in the 4th station has begun.
By injecting light using a filtered LED, we have checked the light output from the D0 --> bulkhead --> station connector and vice versa by eye.
There was no major light loss notable by eye. This will need to be checked again quantitively, once the CCD camera set-up arrives.
The dead channels and mapping information from this has also been noted. This will be put together to produce a final (correct) version of the fibre and waveguide mapping.
For a first look at the mirroring on the 4th station, we used a red LED to illuminate the scintillating fibres at the station connectors.
We found that light was coming through the mirrored ends, but not for all the fibres. We also saw a similar amount of loss for the 3 old stations, which indicates that the mirroring isn’t solely causing the loss of photons, but again this was only a first look by eye, so could be misleading.
Also, we found an interesting effect that light across the planes was delineated by light being scattered out? (See picture on next slide.)

3. Excuse bad photo out of focus
Mirrored end, bright spot
Bright spot, light loss by damage? glue?
Injected light

4. Also whilst checking the mapping of the waveguides we came across a couple of the drilled holes in the bulkhead connector, offset by a reasonably large amount.
This lead to the question could the dowels for example on the bulkhead connectors (only used on 4th station) be slightly misaligned?
Initial measurements have now been taken on the external and internal bulkhead connectors (No.s 105 & 5, which mate together) and a significant offset has been found. We have taken an x,y measurement of the dowels and all 128 holes on both the internal and external connectors. These measurements were then put into AutoCAD and the two connectors were overlapped (see picture, bottom right) and an area of ~25% was calculated to be obscured.
Again, sorry for bad pictures but you can still clearly see the offset

5. Next Steps….
Do the same measurements on the other 4 bulkhead connectors.
Once we have an estimate for the offset on all the bulkhead connectors, we can read off the overlap areas and compare it to Malcolm's light yield in station D as a fraction of the 3 old stations.
Similar measurements will also be taken for the station connectors and analyzed in the same way.
When the QA equipment arrives (CCD Camera, video capture cards etc.) we can check all the other possible causes of light loss i.e. mirroring, scintillating fibres and station connectors, so that we can convince ourselves that we have found and understood the reason(s) for the loss of photons and have a solution for the construction of the final tracker.