[esa-t474] Draft 4.1

Sun Nov 4 20:29:37 GMT 2007

Hi Mark, some comments on the latest paper:
1.  abstract.  Need to state more clearly the following sentence:  "We demonstrate sub micron resolution and micron level stability over 20 hours for a 1 m long BPM triplet and over an hour for a 40 m long baseline."  Suggest something like "We demonstrate sub-micron BPM resolution and stability over 20 hours with a 1-meter long BPM triplet.  We find micron-level stability over 1 hour for 3 BPM stations distributed over a 40-meter long baseline."
2.  introduction.  Need a little more explanation on the LEP2 energy measurements.  Note that their primary method used NMRs and resonant depolarization.  The magnetic spectrometer had an accuracy (not resolution) of 170ppm, but required a calibration using resonant depolarization at lower energies.  Note that most of the methods used at LEP2 can't be used at ILC.  (can use information summary on this from slides 10 and 11 of http://www.slac.stanford.edu/grp/rd/epac/Meeting/200612/woods.pdf)
3.  introduction last paragraph.  Rephrase and state better using active voice.
4.  S2.1 line 108; "... To the electron North Damping Ring..."
5.  S2.1, Fig. 4 caption "The beta functions and dispersion in the Aline and ESA..."
6.  Figure 5 needs to be simplified.  Use A28 etc. for correctors, C1 and C2 for collimators and WS1 and WS2 for wire scanners.
7.  Table 2; I'm still surprised the x jitter is that large, but perhaps it was.  Do you have a plot of the jitter versus time for the 20-hour and 1-hour runs?
8.  S2.3 line 162-63; can you quantify how far from center of the BPM before get nonlinear effects?
9.  S2.3 line 189:  "...significant damage..."
10.  S2.4 line 205:  "...and phase adjustment is also possible."
11.  S2.4 line 218:  BPM32 signals are not split (SCP doesn't use these)
12.  Figure 10 caption.  Should note that sampling is at 119MHz.
13.  S2.5 line 288:  "occur"
14.  S2.6 LVDT accuracy noted to be 6 microns on line 305.  How well do LVDT and interferometer agree?
15.  S2.6 line 312:  "...with respect to interferometer heads on an aluminum table ..."
16.  S2.6 line 315:  "The interferometer heads are polarizing beam splitters that provide the ..."
17.  Table 4:  2nd column should be for "total motion" not "rigid motion"
18.  S2.6 line 329:  "other"
19.  S3.1 line 346 states that require 0.5mm offset to determine frequencies.  This is an important point and would be good
     to elaborate a little.  Would be good to quantify this more and perhaps distinguish what's needed for the lowQ versus
	highQ cavities.  Would be nice if only 100-micron offsets or beam jitter could be used to get this.
20.  Table 5, 3rd column should be w_y
21.  Figure 12:  vertical scale should be kHz?
22.  S3.1 line 391:  note of 100kHz change in BPM11x frequency.  Was this corrected for the numbers used in Table 5?
	Why wasn't it corrected for for later stability plots like Fig. 31?
23.  Table 6 caption.  Use resolution and drift rather than precision and accuracy.
24.  S3.1 line 404:  choosing sampling point where signal is decreased 10% is noted to ensure no monopole contamination;  I need to be educated a little--how does this work?  Different Q for monopole?
25.  S3.1 lines 413-414:  "to minimize this effect by tuning both the reference and ..."
26.  S3.2.  I would start with the mover scan for BPM4 and then move to corrector scans, indicating that we use a scaling correction for corrector scans based on the BPM4 results for mover and corrector scale factors.  
27.  Figure 13 should indicate which bpm is used.  Also in caption and in a number of other places "negligible" is mis-spelled.
28.  S3.2.1 line 451 states that only use central 3 points of corrector or mover scans.  I think we should be using all 5 points!  Would be good somewhere in paper to 
	note what we find for bpm linearity.  I don't see any evidence of bpm saturation.  And as you note later you're limited on scale factor uncertainties by the beam jitter;
	can improve that at least a factor 2 if use all 5 scan points.
29.  S3.2; what are limitations to using beam jitter to get the IQ phase?
30.  Figure 14, S3.2.2 and Eq. 19.  Just go straight to using I and Q phases!  We don't give any info on measuring beam slopes or tilts with the bpms so just avoid that here.
31.  S3.2.2 lines 494-497.  Should note that this procedure effectively minimizes the bpm residuals.
32.  SVD and minimization procedure.  Since the procedure minimizes residuals it doesn't necessarily ensure no dependence of residuals on beam position in each of the
	cavities.  What about a subsequent procedure that defines a chi**2 to minize that quantifies such a dependence??
33.  S3.2.2 last paragraph.  This shouldn't be a cross-check it should (and I think you've implemented as such) be part of the standard procedure!  You even note this is done
	in the 2006 results section.
34.  S3.3 algorithm optimization.  The necessary info should be put earlier in Section 3.1.
35.  S3.4 should be described earlier, probably at end of Section 2 and then 2006 results noted in Section 4.
36.  Table 9 should note this was for the 20-hour run?  Is that true?
37.  S4.1 Eq. 23 and line 566.  Should note that sigma_i is the residual not the "combined resolution"
38.  S4.1 lines 570-571:  leave out (or even environmental data)
39.  Table 10 is very useful.  Suggest that column headings should be Measured Resolution, Electronics Noise,  Vibration Noise (last column is added for bpm4 only).  
40.  S4.1 lines 575-577.  Why are 1x and 11x included in linked system if they have known problems?  (though 11x can be corrected for)
41.  S4.2 Eq. 24:  this should be put in Section 3 as part of the standard calibration procedure!
42.  S4.2 lines 624-634 note problems with 1x and 11x.  Why isn't 11x just corrected for and why are 1x, 11x included in the linked system?
43.  S4.2 line 640:  "consistent"
44.  S4.2 lines 642-647:  tilt should be beam slope!
45.  Fig. 18 notes limitations of using only central 3 points in calibration scans;  why can't we use all 5?
46.  For all plots that show changes in scales or IQ phase, should start them all at phase=0 and scale=1 at t=0 rather than forcing the averages to be 0 or 1!
47.  Figure 19:  should note that these results are anti-correlated with Fig. 17.  Strongly suggests there's a better calibration procedure!
48.  Figure 19a,c:  would make much more sense if applied the frequency change correction.
49.  Is Table 11 really needed?  It's just the simple scaling noted in Eqs 25,26.  Could summarize in text the results.  Why is the x resolution for 1x in table 11 so large?
50.  S4.2 line 660:  tilt should be beam slope.
51.  Figure 21.  Use BPMx1 rather than x41 (also Fig. 22).  And in caption "between".  Each point is for 1000-event block?
52.  Fig. 22.  Why so few entries??  Why not for 1000-event blocks?  Are all runs used?  Only calibration runs??
53.  S4.3.  Relabel Section Heading to something like "Stability of BPM Offsets and Resolution
54.  S4.3 line 675:  "were significant".  Does this indicate changes in scale or errors in scale determination??
55.  Fig. 23.  Horizontal scale should be mm, not microns?  How is the plot generated and what do the error bars mean?  Is this from 1000-event blocks?
	What happens if you make this plot over a short run where just have jitter and no drifts?  Suggests that an improved calibration scheme to take out a correlation
	could work.
56.  Figs. 23 and 24.  Why does vertical scale go to -8 microns in Fig. 24 and only -6 microns in Fig. 23?
57.  Fig. 25 caption:  "between"
58.  Figs 23, 28 and 33 are very useful.  Would be good to elaborate on these and do more evaluation.  Appear to be different regions in the plots, presumably corresponding
	to different time periods that have different scale calibration errors/changes.
59.  Fig. 31;  as stated before should just fix this frequency change for x.
60.  S4.3 line 703:  "...to remove the mechanical..."
61.  S4.3 line 715: for linked system, should remove 1x and 11x (or fix 11x)...
62.  Figure captions don't match figures for Figs 32-37
63.  Figs 36-38 -- explanation or comment on different slopes??
64.  no plot of linked residual over 20 hours is shown
65.  Fig. 38 caption.  First point is 100 MeV setpoint?
66.  S5 conclusions line 743-744.  Can we show a plot that demonstrates the cross coupling for BPM1?
67.  S5 conclusions:  need to note 1-meter and 40-meter baselines when discussing the results for each station and for linked statons.
68.  S5 concusions statements on upgrades.  Note upgrades without stating "most major" or "most significant".  Would be good to itemize them.  Need to include also
	use of the Helmholtz coils for fast calibrations with correctors, so can avoid/reduce beam drift problems in corrector scan calibrations.

mike

-----Original Message-----
From: Mark Slater [mailto:slater at hep.phy.cam.ac.uk]
Sent: Friday, November 02, 2007 3:41 PM
To: esa-t474 at hep.ucl.ac.uk
Subject: [esa-t474] Draft 4.1

Dear All,

I've now finished going through the English and finalised the arguments for the last section on stability. As always, it can be found here:

http://cvs.hep.ucl.ac.uk/viewcvs/papers/esaBpmNote/built/?root=ILC+Accelerator+code

In order to try to get everyone to sign off on the last few plots, would it be possible to have a phone meeting after/instead of the ESA meeting on Monday? Mike/Yury, would you be able to sort the phone conference out if it's not already booked? Thanks! I'll also try to remember the UK clocks have gone back and phone in at the right time :)

Thanks,

Mark

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

_______________________________________________
esa-t474 mailing list
esa-t474 at hep.ucl.ac.uk
https://mail.hep.ucl.ac.uk/mailman/listinfo/esa-t474
-------------- next part --------------
An HTML attachment was scrubbed...
URL: https://mail.hep.ucl.ac.uk/pipermail/esa-t474/attachments/20071104/71a7dc7e/attachment-0001.html