[esa-t474] Re: Run 1421

[Woods, Michael B.]

Hi, need to compare bpm data on this run and make sure bpm calibrations are well known so don't get confused by beam trajectory drifts and scale errors.  T474 log entries 38 and 42 compare zygo and interferometer on run 1141; a similar drift of ~300nm on x3-x4 is seen and there is some correlation noted with the interferometer.  The beam data will be able to tell us whether the drifts measured by the interferometer are meaningful or whether the interferometer measurements have their own drift systematics.  mike

-----Original Message-----
From: esa-t474-bounces at hep.ucl.ac.uk [mailto:esa-t474-bounces at hep.ucl.ac.uk] On Behalf Of Michael Albrecht
Sent: Friday, July 21, 2006 9:34 PM
To: esa-t474 at hep.ucl.ac.uk; Prof. Mike Hildreth
Subject: Re: [esa-t474] Re: Run 1421

The interferometer did not report any problem with the electronics during that run.
I suppose it would be possible for the optical table to move, though since all three distances increase it would mean that the center BPM is drifiting in the same direction as the table.  It could also be that all three BPMs shrunk equally in both directions, with the center BPM drifting.  Do you see the effects of this in the center BPM?  If not, since this drift would be at about the same scale as the vibrations seen in the middle BPM, could the vibrations be "washing out" the drift?
-Mike

----- Original Message -----
From: "Yury Kolomensky" <yury at physics.berkeley.edu>
To: "Michael Albrecht" <malbrec2 at nd.edu>
Cc: <esa-t474 at hep.ucl.ac.uk>; "Prof. Mike Hildreth" <mhildret at nd.edu>
Sent: Friday, July 21, 2006 8:49 PM
Subject: Re: [esa-t474] Re: Run 1421


> Hi Mike,
>
> it is odd that the middle BPM has the smallest drift -- especially since 
> we know it is flimsier than the rest. The sign of the drift appears to be 
> the same on both ends, and from what I recall, we do not see drifts at 
> this level from the BPMs (at least for the difference between x3 and x4). 
> Is there any chance the optical path is drifting, or there is some other 
> problem in the interferometer hardware ?
>
> Yury
>
> On Jul 21, 2006, at 1:30 PM, Michael Albrecht wrote:
>
>> I've been able to access a few of the data files and pull out the 
>> interferometry data.
>> Here's a link to some plots I've generated from Run 1421 ( a 20k event 
>> stability run), both long term and zoom-in plots of each end.
>> http://www.nd.edu/~malbrec2/interferometry/run-1421.html
>>
>> It appears there is a 600 nm drift in the mean value of BPM 3, a 500nm 
>> drift for BPM 5, and just a 25nm drift in the mean value of BPM 4 over 
>> the course of the run.
>> The RMS values, on the other hand, stay fairly constant.
>>
>> -Mike A.
>> _______________________________________________
>> esa-t474 mailing list
>> esa-t474 at hep.ucl.ac.uk
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> 

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