Log entry time 10:51:28 on August29,2005

Entry number 153743

This entry is a followup to: 153320

The "4-peak" history effect I was wondering about in last Thursday's beam 
studies has a relatively simple explaination (and actually rather obvious, once 
you pay attention). The key is that the "outer separation" is not hugely 
different from the "inner separation". Specifically, this means that the effect 
is not due to helicity windows which are asymmetric due to the history of what 
came before, but only the order that the windows arrive. 

We have seen similar effects in the past.  Specifically, we know that our DAQ 
is subject to pick-up of the "pair-sync" signal, which creates a false 
asymmetry depending on which window arrived first.  So, is this effect pickup 
in the DAQ, or is the beam somehow getting kicked by pairsync?  

The top row of Figure 1 shows the battery in the injector crate, with cuts on 
which window came first.  The bottom row shows the bpm1I06x position 
difference.  One can see that the position difference shows clear 
pairsynch-correlation, and the battery does not.  (The data is a chain of all 
of slug 57). While this doesn't rule out pedestal pick-up somewhere in the bpm 
electronics, it does seem to suggest that there isn't a strong pick-up at the 
DAQ.

So, the "separation" is less mysterious, given that it doesn't require pickup 
of helicity signal to be explained.  It is weird that we are so senstive to a 
pair-synch induced pickup.  We could various test this by disconnecting 
pair-synch from the injector DAQ, or possibly disconnecting it altogether.  
This must be done with care, since I am not certain about the requirements of 
our DAQ or the polarimeter DAQs with regards to pairsynch.