Here is a note from Oleg Tsai (and attached file "wiresup.pdf" below) concerning source
measurements of the BSMD gain behavior near the nylon wire supports:

On Fri, 18 Jul 2008, tsai@physics.ucla.edu wrote:

>    Attached plot will help you to understand what you see close to
>  strips 58 and 105. There are two nylon wire supports in the chamber
>  at distances 34.882" and 69.213" from the (eta=0 end of the chamber,
>  not from the real eta 0). Gain drops near these supports. You can
>  see this in your plots also. The attached plot shows counting rate vs
>  strip id for a typical chamber. Don't pay attention to channels
>  near 0 and 150 - these effects are due to particular way co60 source
>  was collimated (counting profile was close to 0.1/0.2/0.4/0.2/0.1)
>  0.4 in central strip. From that I estimated that eta strips
>  56-60 and 104-107 should have calib. coefficients
>  (.95,.813,.875,.971,.984) (.99,.89,.84,.970.), I don't remember
>  if I was using counting rate vs HV to derive these numbers...
>  (this is my third and final attempt :-))
>