Log entry time 03:09:23 on November10,2005

Entry number 159654

This entry is a followup to: 159648

Followups:

• 160047 11/13/05 21:21 lkaufman follow-up to cavity crosstalk

So, I have done some further investigation into the cavity monitor behavior, 
and it seems to me the main culprit of the cavity double-peaking is crosstalk 
between the charge and postion cavities.

Figure 1 contains plots of position differences vs charge asymmetry of 4 
different BCMs from slug 1 and figure 2 contains the same plots for slug 13 
(after the cavity crate was reset).

Figure 1: The upper left plot is the cav2y position difference vs. asym_bcmcav2 
- clearly not flat.  The upper right plot is the cav2y position difference vs 
asym_bcmcav3 - also not flat and a more discreet jump as the charge asymmetry 
crosses through zero.  The bottom 2 plots are the cav2y position differences 
vs. asym_bcm3 (left) and asym_bcm1 (right) which are both much more flat.  It 
seems the position differences have one distribution for positive charge 
asymmetry and a second one for negative charge asymmetry - only as measured by 
the new cavity bcms and not the standard hall A bcms.

In figure 2, the same plots appear to be much more flat than before, and as a 
result we don't see the double-peaking in the position differences.

I compared the charge asymmetries of the new cavities vs the old bcms, and 
things look linear.  There is no apparent change between slug 1 and slug 13 in 
these distributions.

Could this be a phase issue or maybe a reference signal issue if the cavities 
lock in a different place every time the crate is reset?