Integration issues - barrel strip layers

Current geometry

This image shows the VTX geometry as currently in CVS (see also this page.. The outer barrel layers (green) and the first endcaps (red) almost touch, and routing of cables and cooling services from these layers to the outside would be problematic.

In Yellow is indicated the 'interaction diamond', at x=y=0 and z=+-10cm. From the endpoints of this diamond, lines are drawn indicating the acceptance of the Muon arms in gray (12-35° and 10-35°) as well as of the central arms in red (eta=+-0.35).

The outer barrel layers extend substantially outside of the central arm acceptance. Here we explore possible different arrangements of the barrel strip components such that these integration issues can be ameliorated.



A - Proposed possible alternative

In the configuration shown on the right, the length of the barrel strip layers has been modified, and the radius if the outer barrel is increased. The geometry changes are summarized in the table below.
In simulation parlance, layers 1 and 2 are the barrel pixels, and layers 3 and 4 are the barrel strips (while 5-12 are the silicon endcaps).


  layer 3 layer 4
  # detectors per stave # detectors per stave radius staves per sector dphi
Before 5 6 14.0 cm 13 12.522°
After 4 5 15.9 cm 14 11.300°
This is the corresponding phnx.par file.

For layer 3 total number of detectors has gone from 2 sectors × 9 staves × 5 detectors = 90 to 2×9×4 = 72, and for layer 4 the total has gone from 2 sectors × 13 staves × 6 detectors = 156 to 2×14×5 = 140. This is a 14% reduction in the strip sensor count.

Below are the barrel cross sections at z=0 before and after. Black lines indicate the Central Arm acceptance
Layer 4 with 13 staves at r=14.0 cm Layer 4 with 14 staves at 15.9 cm. The central arm acceptance is indicated on one side only.


B - Another alternative

Another possibility is to take the current layers 3 and 4, and simply move them out to larger radii (14 and 17 cm, respectively) , without changing the chip count. As can be seen in the figure, the layers no longer interfere severely with the endcaps. The price paid for this is that the phi coverage is reduced, as can be seen on the cross section figure.

phnx.par for this configuration.
Last update 5 Jan 05 - HvH