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#### User name emily

#### Log entry time 18:17:10 on July 27, 2006

#### Entry number 175587

#### This entry is a followup to: 175449

keyword=BCM cal: Reason we need to do another one

Attached are plots of BCM calibration coefficients as a function of
beam current (uA) for BCM1 and BCM2. These data were taken from two
different runs (5am and 10am 26 July 2006). If the relationship between
beam current and coefficient is linear (as we think it should be), all
the points in a given BCM should lie about the same coefficient; they
don't. Two distinctly different coefficients are visible each of the
plots. For For the BCM1 calibration, at 10uA the coefficient is about
43.65, and at 20uA the coefficient is about 44.0. For BCM2, the 10uA
coefficient is about 44.45 and the 20uA coefficient is around 44.9.
BCM1 and BCM2 coefficients may be different from eachother, but data
from a single BCM should agree around one coefficient value.
To completely characterize the relationship, we must take at least one
really good calibration run, in which we log the BCMs' behaviour for
about 3 minutes at each of 5uA, 10uA, 15uA and 20uA against the 0L02.
The procedure for this will be posted on the LEDEX webpage and should
take only 15-20 minutes in total. This will allow us to see how linear
the coefficient relationship is and how well the 0L02 performs at low
currents. We will take a calibration run against the calorimeter later
on.

BCM1 Cal Plot

BCM2 Cal Plot