[Halld-tagger] active collimator signal vs translation stage displacement

[Richard Jones]

Hovanes and all,

I have attached a plot of what I think you wanted to see: the difference over the sum of currents in the two inner wedges as a function of displacement of the translation stage carrying the active collimator across the beam.  Notice that in the central linear region of high sensitivity, the error bars are much larger than outside this region, where the sensitivity to position decreases.  The error bars in the low slope regions on either side of the plot are a good indication of the intrinsic resolution of the device.  The gain of the central linear region is about 1.8/cm.

In this plot you can see slow drifts in the beam position as bumps and wiggles in the otherwise smooth transition from the region of -1 to +1.  I estimate the intrinsic resolution at 15nA electron beam current on a 10^-4 radiation length target to be less than 50 microns at 600 Hz bandwidth.

-Richard Jones


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