Segmentation, Occupancy and Radiation Damage

The process e e — and the subsequent decays produce charged particle mul- 

All issue of primary importaiu e that d( p( Mcls critically on segnientation is the rate of background hits that can be tolerated. There aro two major sources of background  

Botli of these sources can cause signals aljove threshold in the silicon detector. Such signals may influence tlie position resolution if a hit is close to a particle track or if hits in different layers line up to fake a track segment and contribute to the trigger or affect [lattern recognition. Both of tlu se effects become severe at a strij) occupancy of about 1% per trigg( r. 

We can estimate the occupancy for tlu iiinerniost barrel layer, wln ii these backgrounds are most. severe. The calculation of occu))aiu y is liased on an integration period of 1 //,s, which is longer than we will likely use, but this leaves room for substantial improvement in case the strip occupancy is worse than estimated. 

The expected integrated radiation level for the first layer of silicon is 10 kRad/yoar, well within this conservative limit. It should be noted that the radiation dose is distributed fairly uniformly along the beaniline, but peaks sharply in the plane of tlic accelerator l)ends. The maximum dose occurs at ( = 0° and 180°, where it is approximately 150 krad/year with an rms spread of about 1°. This exceeds our limit however it will be concentrated on a very small area of the detector ( 1%) and primarily affects the first layer. 

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