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Material in Detector




Dear Collaborators,

During the integration session on Monday and the collaboration meeting
following, there was considerable discussion regarding the amount of
(dead) material in the detector. This is the first time we are looking
into this issue in detail. Curtis included what he considered "reasonable"
quantities of dead material in the MCFast simulations, so the simulations
have some degree of reality, but probably do not present a complete
picture.

I wanted to summarize the material for the inner detectors which I know
about and perhaps the list can be updated with input for everyone else:

From the target out:

1. Vacuum/scattering chamber

2. Start counter (5 mm)
3. Vertex detector cylinder (6 mm)
4. Vertex detector cone (6 mm)
==> Total Start/Vertex Material = 17 mm (0.043 radlen)

5. CDC proper (windows, gas, wires)
6. CDC endplates (1 cm Al, 2.7 g/cm2, 0.11 radlen )

7. Frame for Drift Chambers
   This rests on calorimeter, may or not be retracted with
   drift chambers during maintenance

8. Cables for FDCs. (7 ribbon cables thick, 0.9 g/cm2, 0.035 radlen)
   Very likely cables will be routed using drift chamber frame for
   support and cable routing.

9. FDC chambers (windows, gas, wires, cathodes)

10. FDC frame to hold wire feedthrougs. Probably needs to be about 1"(?)
    thick Al

11. Internal support for calorimeter. Not clear this is required, but
    could also double with drift chamber frame (#7).

Notes:

For material near the barrel calorimeter, material should be compared to
thickness of one layer of Pb. For KLOE design, 0.5 mm Pb, this is 0.56
g/cm2 and 0.09 radlen.

Multiple scattering angle = 0.0136 sqrt(radlen)/ (beta*p)
                          = 3 mrad for radlen = 0.05, beta=p=1

-- 
Elton Smith
Jefferson Lab
elton@jlab.org
(757) 269-7625