Present: Grillo, Jaros, Maruyama, Odian, Nelson
Please send corrections or comments to the whole gang.

1. Data Rates, Radiation Dose, Layout
Takashi present the attached slides, which have a couple of important developments.

The present dead zone is define by +/- 15mr from the target. Takashi has actually placed the silicon within 5 mr of the beam; then the active area, beyond the guard ring, is at 15 mr in the first layer. The result is that the guard ring area is heavily radiated--something like 4 x 10**16 electrons/ cm **2.

Question is: can the sensor take this rad dose in the guard region?

Data rates have been more carefully estimated, which should be of use to DAQ considerations. Although the inner most strips of layer 1 have >4% occupancy, this high rate falls off very rapidly. The average number of hits in the different layers is very manageable, ranging from 6.2 in layer 1 to 0.3 in layer 4/ per 25 ns time slice. Accounting for strip multiplicity and both H and V in layers 1,2,and 4, gives about 30 strips hit per 25 ns time bin.  Each strip requires a 2 byte address, and about 10 bytes for the amplitude information of 6 adjacent time samples (assuming the APV readout chip). Hence, the si tracker gives about 360 bytes of data/trigger from signals. Including a conservative estimate on noise hits, gives a total (S+B) of 500 bytes/trigger.
 
Takashi also proposed a simple layout for the first three layers, which ca n have reduced solid angle coverage and still maintain full acceptance. The scheme is shown in his talk: Layer 1 has 6 V sensors and 4 H sensors; layer 2  has 8 V, 8 H; layer 3 has 10 V sensors; and layer 4 has 10 V and 12 H sensors. There will likely be in addition a layer or two of small angle stereo, still undefined.
 
Finally, Takashi considered increasing the horizontal acceptance, which is possible because the magnet gap is 18 inches wide. Adding extra sensors boosted acceptance by roughly 25%., but would complicate reading out a horizontal detector which would no longer have its hybrid out of the acceptance.
 
2. APV vs ABCD.
Work is still going on to characterize the efficiency loss with irradiation for both ABCD and APV. This work will be valuable in discussing radiation damage in the sensors for the proposal, but those present agreed it did not really bear on the selection of one readout chip over the others.
 
Those present, and Matt and Rich (offline), concurred that we should use the APV25 chip. It offers the potential for somewhat better signal to noise, and therefore better radiation tolerance and resolution, but it's principle advantage is that it can provide few ns timing. This can reduce occupancy significantly and thereby reduce fakes.