[esa-t474] T-474 PAC paper

[Woods, Michael B.]

Thanks Alexey, it's looking quite good.  A few comments:
1.  for the LEP comparison, very useful to give some additional notes.  First, you should note this is for LEP-II.  I believe the overall precision achieved was 120ppm and the bpm spectrometer was basically a cross check only measured a few times and had a precision of 170ppm.  Primary technique at LEP-II used resonant depolarization and scaling from the Z-pole to higher energies with NMR probes to get the B-fields and then rf and bpm measurements to get the closed orbit length.  LEP-II was also able to use a synchrotron tune technique to get the beam energy.  And the bend angle available for the bpm spectrometer was 3.8mrad.  Neither the resonant depol nor the synchrotron tune are applicable at ilc.  A brief overview of some of that is in slide 11 of my epac talk, http://www.slac.stanford.edu/grp/rd/epac/Meeting/200612/woods.pdf but of course more details are in the reference you give.  It's also important to point out that at LEP-II the bpm spectrometer was calibrated at lower
energies with resonant depol and only gave useful energy measurements close in time to a resonant depol measurement (probably within an hour or two).  By contrast, at the ILC we will do our calibration by changing the polarity of the chicane -- I don't think this is described in the paper and needs to be.  
2.  For figure 1, should give more precise z distances.  See z locations noted in http://www-project.slac.stanford.edu/ilc/testfac/ESA/ESA_beamline/ESA_zlocations1.pdf, http://www-project.slac.stanford.edu/ilc/testfac/ESA/ESA_beamline/ESA_zlocations2.pdf
http://www-project.slac.stanford.edu/ilc/testfac/ESA/ESA_beamline/ESA_zlocations_07Mar07.pdf
3.  last paragraph of Test Setup, suggest "The SLAC linac provided bunches of 1.6 x 10^10 electrons at 10Hz, parasitic to PEP-II operation.  The transverse rms beams size through the spectrometer BPMs in ESA was ~200 microns vertical and ~500 microns horizontal; the rms bunch length was ~500 microns.  The beam orbit was stabilized with a BPM-corrector feedback system.  Feedback correctors and later also Helmholtz coils were used to calibrate the BPMs.
4.  Performance of the BPM system
i) first paragraph, "...long term precision and stability of the ..."
Ii) should define more precisely the "linked resolution"; for example determined from the residual measured by BPM5 to the prediction using BPMs 1,2,9,10,11.
Iii) paragraph after table 1 should mention electronic gains drifts as well as mechanical motion drifts, both due in part to temperature drifts
Iv)  last sentence should state that Temperature correlations were seen in the new calibration data, not just that temperature drifts were seen.
5.  Suggest renaming "Chicane Magnets" section to "4-Magnet Chicane"
i) suggest for  1st paragraph in this section "...Measurements at SLAC's magnetic measurement test facility found the field and field integral to be uniform to the level of 10^-4 in a region of +-15mm horizontally.  The field integral was found to have a 60ppm per degree C temperature dependence, which is acceptable for these tests. ... The magnets have been instrumented in ESA with Hall and NMR probes to monitor ...
Ii) should note that we choose B~1kgauss and the mid-chicane dispersion to be 5mm, which are both similar to the current ILC design.
6.  First energy measurements section
- should describe calibration procedure here if not done already; ie. polarity reversal, moving bpm and tracking motion with interferometer (and note that this replaces the Z-pole/resonant depol calibration at lep-ii)
i) last sentence should read "...at the high dispersion points in the A-line delivering beam to ESA and a good ..."
7.  I couldn't find in the text where reference [2] was referred to.

Cheers, mike

-----Original Message-----
From: Alexey Lyapin [mailto:al at hep.ucl.ac.uk] 
Sent: Friday, June 15, 2007 10:49 AM
To: esa-t474 at hep.ucl.ac.uk
Subject: Re: [esa-t474] T-474 PAC paper


Hi All,

Stewart and I went through the paper today, the new version is on cvs:

http://cvs.hep.ucl.ac.uk/viewcvs/PAC07_paper/pac2007_paper.pdf?cvsroot=LC+Energy+Spectrometer

Cheers,
Alex

Alexey Lyapin wrote:
> Dear All,
> 
> I've got the first draft of the paper ready at 
> http://cvs.hep.ucl.ac.uk/viewcvs/PAC07_paper/pac2007_paper.pdf?cvsroot
> =LC+Energy+Spectrometer
> 
> (use the "download" link)
> 
> Please, check the list of the authors and affiliations carefully. Any 
> suggestions on the contents are of course welcome as well. I would 
> appreciate any feedback sent to me by June 15.
> 
> Cheers,
> Alex
> 
> 


--
===================================

Dr. Alexey Lyapin
Department of Physics and Astronomy
University College London
Gower Street
London
WC1E 6BT

Tel: +44 (0)20 7679 3454
Fax: +44 (0)20 7679 7145

===================================
Making good choices we win,
making bad ones we learn
===================================

_______________________________________________
esa-t474 mailing list
esa-t474 at hep.ucl.ac.uk
https://mail.hep.ucl.ac.uk/mailman/listinfo/esa-t474