Log entry time 09:59:14 on October17,2005

Entry number 157202

Followups:

• 157292 10/18/05 13:19 paschke Not really news, but ... position differences still small.

Helicity correlated position differences are small... very small.  This is 
apparently some combination of our success on the source table and what appears 
to be terrific damping in the machine.  

First, a note on the beam optics in the Hall A line.  They are significantly 
different then during Helium, in that the 4ax and 4by 30 Hz jitter is 
approximately 10 micron. These were 25-30 and 15-25 micron (respectively) 
during Helium.  One expects that the position difference will automatically 
scale down by this factor, regardless of other work down.  Even with this in 
mind, the position differences are smaller than during Helium.

First, I don't have good information from the 100 keV region over the weekend, 
as I don't have a way to filter the times that Hall B is on. Figure 1 shows 
BPMs in the injector (100 keV and 5 MeV regions) for approximately the setup we 
ran with during the weekend.  This is a reasonable guess at what is going on 
there now: up to a few hundred nanometers, but well controlled.  (This data was 
before Chao's work was complete in the injector, so the 5MeV points may be 
better damped now.)

Figure 2 shows data, averaged over a significant portion of the weekend, from 
the 5 MeV region and the Hall. 0L01, 0L02 are in the 5MeV region, bpm12=1C20 in 
the Hall A arc, bpms 4a and 4b are closest to the target.  The position 
differences are all under 100 micron,
and consistent with zero in Hall A.  Error bars here are <15nm. 

The exact factor for damping is hard to discern, only because the measurements 
are pretty much consistent with zero in the Hall.  But it is reasonable to 
guess that we gain a factor of 10-20 over the position differences in the 100 
keV region, and at this time we can't rule out a higher factor of suppression.

Sometime in the next few days we hope to be able to say something more about 
damping using the helicity magnets.  Meanwhile, it is clear that we are so far 
doing very well in terms of beam properties.