BCAL Cell Cross Talk

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Before the installation of PMTs, the light guide box alignment was ajusted (iteratively) for cross talk between light guides has been performed, and here is the final result:

       N                           S    
       1                     No leakage 
       2                     4 fibers(F)in 1
       3                     0.5 rows (R) in 2
       4                     0.5R in 3; 0.5R in 5
       5                     1R in 6
       6                     2F in 12
       7                     1R in 8; 5F in 1
       8                     0.5R in 9
       9                     1R in 10; 1R in 3
      10                     1R in 4; 1R in 11
      11                     0.5R in 12; 0.5R in 5
      12                     2F in 18
      13                     1R in 14; 5F in 7
      14                     5F in 8; 0.5R in 15
      15                     0.5R in 9; 1F in 10; 0.5R in 16
      16                     1R in 10; 1R in 17
      17                     0.5R in 11; 1R in 18
      18                     1F in 12  

Each readout light guid has 1.5in x 1.5in (3.81cm x 3.81cm) surface. There are 18 readout cells (3 by 6) and the total readout surface is 11.43cm x 22.86cm (261.29cm^2). The BCAL module has 13cm x 23.2cm (301.6cm^2) readout surface, which means that light guides collect only about 85% of the lights.

Also, to keep this 'cross talk' in perspective recall the following. The fiber pitch horiontally and vertically in the beam test configuration leads to 32 and 28 fibers in each cell along each dimension, for a total number of 911 fibers per cell (no joke!) Therefore, a leak corresponding to one row horizontally (left-right leak) leads to a 32/911->3.5% effect, while vertically it results in 28/911=3.0%. It is unlikely that this is discernable even in MC simulations, due to the sampling fluctuations/resolution. Therefore, the above alignmemt is adequate for our needs since we never have more than one row affected.