User name R. Michaels
Log entry time 14:48:41 on July24,2005
Entry number 149296
Followups:
keyword=septum scan resultsAs the septum was scanned +10% and then +20% the elastic peak
moved towards +P. This put more of the elastic peak on the detector,
see fig 1. That is for the Left arm, the Right arm is similar.
The triggers shown are S0 triggers only (unbiased, we think).
(The relative peak sizes don't mean anything.)
But one must be VERY CAREFUL about interpreting this. The rate
observed depends not only on how centered is the elastic peak, but
on acceptance chopping. A first glance at the tradeoff is in fig 2.
Shown in black is the predicted rise in rate due to integration
of the radiative tail (BTW, this may answer the question some had
about how sensitive is our alignment, could we be losing 20%, etc).
This prediction is based on data analysis of the observed tail.
The blue/red points in fig 2 is the increase in scaler rates
(normalized to beam current) for the HAPPEX detector trigger in
each HRS. The two points correspond to +10 and +20% septum, and
the numbers were given in halog 149236.
As the septum current increases the rate increased
beyond what was expected from the radiative tail, suggesting a
better septum optics (???), but at 20% there was clearly a
diminishing return. At present, it looks like 10% is a reasonable
place to run, if it provides better septum cooling but I would not
go for 20%.
I have more to check...
FIGURE 1
FIGURE 2
