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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