[esa-t474] 3rd Draft of Paper
Bino Maiheu
bino at hep.ucl.ac.uk
Wed Sep 26 13:09:00 BST 2007
Hi Mark,
Here are the combined comments from Alex and myself for the first two
chapters of the paper. Our comments on the rest of the paper we will
bundle by friday.
Cheers,
bino
-------------------------------------------------------------------------
0. Global remark : check out the tense of the paper, do we want all in
present or past, or setup in present, what we've done in past ?
1. Title of paper too long,
-> suggest : "The S Band Cavity BPM system for ILC spectrometer
tests at ESA in SLAC"
2. Author list... alfabetically etc..., will prob be requested by NIM.
3. Add "Acknowledgements" at the end : Work supported by EuroTeV, DOE,
bla bla...
4. Abstract : doesn't read fluently,
-> line 16. : get rid of "this year".
-> maybe already quote some basic results in the abstract...
-> suggest rewrite :
The main physics programme of the International Linear Collider
(ILC)
requires a measurement of the beam energy at the interaction
point with
an accuracy of $10^{-4}$ or better. To achieve this goal a
magnetic spectrometer
using high resolution beam position monitors (BPM) has been
proposed. This
paper reports on the cavity BPM system that was deployed. We
demonstrate sub micron
resolution and micrometer level stability over a few hours for a
40 m long base line.
The understanding of the behaviour and response of the BPMs
gained from this work
allowed spectrometer tests to be carried out at a later stage.
-> or something like that...
5. Introduction
-> general comment: reads very influently, bad english !!
-> line 19 : "...to control the collision energy" :
The energy measurements don't control the collision energy !
and get rid of the \sqrt{s}
-> line 22 : "... particle resonances in the continuum", "scalar top
sector", etc..
to heavy : just keep something like "... threshold cross
section measurement and
reconstruction of particle resonances. To achieve the required
accuracy.... "
and kill lines 21 -> 25, we 're not discussing the standard model.
-> line 26, line 28 : 2x accuracy... replace!
-> line 30 : not "displaced", but "deflected",
-> line 30 : "by the an angle" -> "by an angle"
-> line 32, 33 : "where c is the speed [...] along which the beam
travels."
replace by : "where c is the speed of light, q the electic
charge of the particle,
E_b the energy of the bunch, B the magnetic field
and dl the path segment ...."
-> lines 34 -> 39 : suggest replace by :
"Two identical magnets with opposite field allow the beam energy
to be measured as a function of an induced horizontal
displacement $x$, given by
--> equation (3),
in case of small deflection angle $\theta$."
-> line 40 : "thus..."
suggest : "Therefore the precision and accuracy of the measured
offset $x$, contributes directly to the
uncertainty....".
-> line 44 : LEP -> LEP2 ( everywhere ! )
-> line 43 : check reference [3], is this really quoted in this
paper ? CHECK !!
-> line 50 : "of the beam displacement measurement" : too heavy
suggest : "of the measurement"
-> line 51 : "revolutons" : typo
-> line 51,52 : "(the bunch averaging ... used.)" : get rid of
this, other wise one has to explain.
-> Figure 1 : don't like the style of this figure, too bulky.
change to something similar to figure 2
-> Figure 1 : is'nt the orientatio nof the magnets reverse ? (
check pink floyd "Dark Side of the Moon" :) ! )
-> line 53 : get rid of the 1 $\mu$m
-> line 58 : 10${-4}$, already mentioned, don't have to repeat it
-> line 57->61 : too much bla bla, rewrite !
"These constraint make the requirements for the BPM system of
the ILC spectrometer much more stringent than at LEP2."
-> line 60 : either move [4] after "deflection", or consider better
reference ( e.g. RDR or so)
-> line 61,63 : "However, designing..." : from "la la"-land
suggest :
"However a better performing BPM system would allow smaller
deflection, and therefore reduce the emmittance growth due to
synchrotron radiation."
-> line 63 -> 66 : rewrite : "In addition, the system has to be
stable to the level of 500 nm over multiple hours..."
-> line 67 : get rid of "In addition to the spectrometer
application".
-> line 69,70 : "...must be tuned...", "... must be measured with a
resolution of 1 um for orbit correction and emmittance
preservation. High resolution BPMs are also required for
the beam delivery system (BDS)."
-> line 74 : "require" -> "requires"
-> line 76, 82 : sounds too much like an abstract,
suggestions :
- get rid of "unique environment" : not promo-talk + mentioned
in next chapter !
- have to mention here that this is in the context of the T474
experiment ( hasn't been mentioned so far ) + refer to the
T474 propsal !!
- Suggest beginning :
"In the framework of the T474 test beam experiment at End
Station A (ESA) several BPM stations were installed the
40 m of drift space available."
- line 80 : "Extensive testing"
more something like "deployment, commissioning and
optimisation"
6. Chapter 2 : ESA Beam etc..
-> Sectioning is to detailed, suggest :
Section 2 : "ESA Beam and Hardware Configuration"
2.1 : "End Station A Facility"
-> bring all the stuff under beam config, (
currently 2.1,2.2,2.2.1,2.2.2) optics, etc in
here !
2.2 : "The BPM System"
2.2.1 : "Cavity specifications"
--> include current 2.3.1 and 2.3.2
2.2.2 : "Processing electronics and DAQ"
--> include current 2.4 and 2.5
2.2.3 : "Mover system and mechanical stability
monitoring"
--> inlude current 2.6 and 2.7
-> line 84 -> 90 : suggest rewrite :
"End station A as SLAC which witnessed the discovery of quarks
in the seventies has in recent years become host to serveral
experiments mainly developing instrumentation for the
ILC. Energy spectrometry experiments, both BPM and
synchrotron light based, collimator wakefield measurements,
novel bunch length and profile monitors all profit from the
unique high energy beam with key properties similar to those of
the ILC."
-> table 1. : - bunch charge more like 1.6e10
- number of bunches per train no longer valid i think,
refer to latest value ( RDR )
-> line 92,... :
suggest rewrite :
"The ESA beam is produced by the main SLAC LINAC with a
maximum energy of 50 GeV."
-> put [8] behind the 50 GeV ??
-> line 97,98 : "was set at 10 Hz" -> "was set to 10 Hz"
-> line 98 : "containing up to 2e10"
-> line 100 : is beam switchyard branching off to PEP-II ?
suggest rewrite :
"beam switchyard, where it was directed in to the A - Line
leading up to ESA."
-> line 104, 105 : get rid of first sentence, actually get rid of
everything up to line 107, up to "On entering.." : doesn't give
any info, just confuses !!
-> line 107 -> 109 : get rid of "100 m in length." and make 1
sentence: "... a bending section consisting of two identical..."
-> Figure 2: Need to explain what wakefield box mean, or change to
"collimator wakefield experiment"
-> line 111, 112 : sentence doesn't really make sense, rewrite !
-> line 113 : symmetry quadrupole ???
-> line 117 : get rid of "as wel as to give flexibility.", not a
promo talk !
-> line 117 : "steel dipole" -> "dipole". Steel is irrelevant.
-> line 119 : "This second dipole pair" : refer to figure 2 : xcor
28,32, ycor 29,33...
-> line 127 : the beam profile monitor is not in the diagram
-> line 128 : replace the word "straddled", Belgian, and Russian
guys present here !!!!
-> entire section 2.2.2 : everything is "located", variation needed
!!
-> line 128, 129 : bad sentence construction
-> line 129 : replace "collimator wakefield box used by the T480" by
"the collimator wakefield experiment, T480, ....
-> line 132 : get rid of wakefield "box" -> "T480 setup"
-> line 135 : replace "ion chambers" by "beam loss monitors"
-> line 136: refer to figure 2 already at the top of this paragraph,
after the first sentence !
-> line 137,138 : kill the first sentence, is described afterwards
-> line 138 141 : suggest rewrite :
"A position feedback system taking the response of
BPMs 31,32,1 and 2 stabilised large scale beam drifts to about 10
um. It used trim coils on corrector magnets 28,29.... etc."
something like this
-> Figure 3: Suspect that the optics displayed doesn't match the
beamline above !! e.g. the last focussing quadrupole doesn't
match the last maximum of the betx function. Was the top part
shifted ? Also the experimental hall doesn't contain quadrupoles
as could be inferred from the beamline division above the plot
!!!!!!!
-> line 141 : "A similar... to control... " -> "An other... to
stabilise... "
-> line 146 : "Using the toroids..."
-> suggest replace by
"Using charge sensitive toroids, the absolute value of the
bunch charge could be measured.
-> line 147 : "give user feedback" -> "monitor"
-> line 148 -> 150 : Hmm, think about how to phrase this, depends on
the used optics obviously. Comparison to measurement ??? ->
Mention paper from frank ??
-> Table 2 :
- think the frequency of the ILC LINAC BPMs is 2859 and not
2856, have to check !!
- do we have more accurate values for the Q values ?
-> Figures 4 and 5 : make smaller, put next to each other and
replace figure 5 by a better picture ( maybe just one single
BPM).
-> for entire section 2.3.1 ( lines 157->169 )
- line 157 : "Rectangular cavites made up"... rewrite !!!
- probably mention the problems here already with BPM 41 ( or
which one was it )
- refer to Q as "loaded Q", or "Q_L"
- mention the dipole modes for rectangular cavity TM120, TM210
with a reference
- lines 167->169 : all this is mentioned in table 2, just refere
to that table!!!
- mention that the rectangular cavities were tuned with external
tuners
- results from VNA measurements ( Yury ?? )
- explain briefly in the text what the frequency ( freq of
dipole mode), aperture, Q factor ( what means the quality
factor... )
-> line 184 : "coupled from" -> "coupled out of"
-> line 185 : "just prior" -> "prior"
-> line 186 : have to mention the attenuators and the phase shifter in
the text as well.
-> line 187 : mention the bandwitdh in text, not by having "\Delta
\omega", but saying "is being filtered using a band pass filter
around 2856 MHz with a 20 MHz bandwidth"
-> line 188 : not really "maximise" the dynamic range.. think about
this !!
-> line 192, 193 : get rid of the variable attenuator sentence, this
was originally the frond-end attenuator, not present on the back
end.
-> line 195 : we don't mention the counting house up to this,
introduce it.
-> line 199 : 3 dB ? think it was 6 dB
-> line 202 : LINAC RF -> "LINAC main RF drive line (2856 MHz)" <--
mention ! "
-> line 203 -> 207 : needs a bit of thinking and rewriting !!! check
yury's mail + discuss : more info needed !
-> figure 7 : do we need this ? doesn't add anything to the paper
and not very informative ! -> add some of its info to the text
-> lines 218 -> 221 : get rid of the itemisation, write it out in
text!!
-> line 226 : "2mm per revolution screw" -> "2 mm pitch screw"
-> line 240 : only mention "a measurement of the relative velocity",
probably want to mention the position as well ;)
-> line 242 : as we quote \lambda / 2048, we need to give the
frequency of the laser as well
-> line 249 : "a generalised version of the SVD method" : leave out
or refer to something or explain what you mean by this !
-> line 250 : Is it not the aluminium support which induces
larger vibration as well and not solely the mover brackets !!
-> table 3 :
- change layout of table, next to each other, make wider!
- run 1421 : quote as a time, not as runnumber, doesn't mean
anything
- is NRB an accepted abbriviation ? only use it a couple of
times, so write in full each time... avoid having too many
consultancy-style abbreviations !
On Sun, 2007-09-23 at 22:01 -0700, Woods, Michael B. wrote:
> Hi Mark, a lot of good progress! I still have a number of issues
> though and think it needs some more work. Would be good if we could
> schedule a 2-hr block of time this week for a meeting for several of
> us to discuss. Some comments (especially note comment 15 regarding
> calibration procedure and suggestion to modify):
>
> 1. author list -- R. Arnold (not Arnolds); should include Doug
> McCormick (see notes below on mover system)
>
> 2. lots of spelling errors; need to run spellcheck
>
> 2.5 should consider having an index
>
> 3. Introduction. On p.3, centering and stability of the beam orbit
> to 1 micron in the Linac is not needed to maximize acceleration;
> presumably it's for wakefields and emittance growth (Chris Adolphsen
> should comment)
>
> 4. Table 1. leave out line on polarization, since we aren't using
> that (not running with polarized gun). For bunch charge in ESA,
> should probably give 1.6e10 (or whatever we ran with in july 2006)
>
> 5. Section 2 on ESA beam
> - I need to give you some text here (still, promise soon really!)
> borrowing some from Frank Jackson (Technote 2006-1,
> http://www-project.slac.stanford.edu/ilc/testfac/ESA/TechNotes/TN-2006-1.pdf)
>
> - Figure 2; would be good to clean up text on figure. Use A28, A29
> for xcor28 and xcor29 and similarly a32 and a33. Use C1 for first
> collimator and C2 for second collimator. Use WS1 and WS2 for
> wirescanners. Move "to beam dump east" text lower. Then in caption,
> include "C1 and C2 are collimators. WS1 and WS2 are wire scanners.
> A28 (29) and A32 (A33) are horizontal (vertical) correctors.
>
> - in last paragraph of 2.2, I believe the jitter was much smaller than
> 190 microns in x (probably about 50 microns in ESA at 3bpm1,2 and
> maybe about 80 microns at 31,32 in aline). Will want to quote
> spotsizes and emittances too. I can work with Frank on text for the
> beam section.
>
> 6. Section 2.3 Cavity Specifications (suggest Cavity BPM
> Specifications)
> - "as described in Section 2.2" rather than "as mentioned
> - Table 2; would think that 31,32 apertures are 51 mm
> - 2.3.1: "BPMs 31, 32, 1 and 2 were built for the A-line." ...(see
> Figure 4)
> - give part # / description for tuners; at this point for the slac
> bpms should reference paper by Yury and Whittum (ref 14)
>
> - 2.3.2, "thus reducing monopole contamination of the dipole mode..."
> also, regarding the lower Q value just simply state that the Q factor
> is ~500 and is chosen to be relatively low so as to achieve short
> enough decay time to resolve single bunches with 300ns spacing at the
> ILC (I don't see that signal analysis and processing become more
> difficult, though the resolution will be a little worse)
>
> 7. 2.4 Processing Electronics (suggest BPM Processing Electronics)
> - Figure 6; should give part numbers for devices shown; need
> description for variable attenuator and phase shifter before first
> BPF; need description for the test port for calibration signals and
> limiter; need to show final attenuator before adc?
>
> - spllitting of signals for 31,32,1,2 need a little more description
> (Yury or I can probably do this)
>
> 8. 2.5 Data Acquisition
> - should have Zen review
> - note that SIS digitizers are VME modules;
> - other 10hz event data recorded included 3 bad spill monitors (3c1,
> 3wake1 and 3c2) and the ws1 and ws2 pmts; these should be used for
> beam quality cuts
>
> 9. 2.6
> - should get parts specification and terse description from Doug
> McCormick
>
> 10. 2.7
> - should provide a schematic for the interferometer to indicate light
> paths, beam splitters, retroreflectors etc and give parts list
>
> - Table 3; should have this as a single 3-column table. In caption,
> suggest for last sentence "The errors quoted are the spread of the rms
> jitter measured in 20 blocks of 1000 events within a 30-minute run
> (run 1421)."
>
> 11. 3.1
> I get confused in this section with which voltage and frequencies we
> are discussing; would be good to add references to figure 6. Equation
> 10 is stated to be at the bpm output coupler, but then after that
> equation is a sentence that "…waveform described by equation 10 is
> what is recored at the digitizer." what about the IQ mixer shown in
> Figure 6? This paragraph should then make clear that the second
> downconversion is done in software and call it digital down conversion
> DDC.
>
> - figure 9, should label as a), b), c)
> - would be good if paper gave some results for capability of bunch
> tilt measurements, noting its importance at ilc for diagnosing
> wakefields; perhaps there are some references?
>
> 12. 3.2
> - is this the first time precision and accuracy are mentioned? Need
> to define! For precision would prefer instead to use resolution;
> isn't that much more commonly used? Accuracy seems to refer to the
> stability of BPM residuals.
>
> - for these 5 systematics, in results section would be good to have a
> table summarizing their contributions
> - in 3.2.2, "both" appears twice in 3rd sentence of 2nd paragraph
>
> 13. 4.1
> - need to explain the different frequencies, starting with the BPM
> frequency and how the ~36MHz frequencies in Table 5 arise from
> sampling the 83MHz downmixed signals at 119MHz
>
> - figure 10, should note this is the stability of the mean frequency
> listed in Table 5. horizontal axis for this and other related 20-hour
> plots should be like Fig. 23. Since this can be done independent of
> calibrations, would be better to show more results distributed
> throughout 20 hours. Should show correlation with bpm10 temperature
> or refer to Fig. 30.
>
> - how did you determine that the large systematics in bpms 1,2
> frequency determination were from monopole leakage and x,y coupling?
>
> - for table 6 and associated text on p.19, need to clarify what
> precision and accuracy are
>
> 14. 4.2.1
> - "…After computing the change in beam position due to the change in
> corrector current, the measured position was plotted against the
> predicted position… the slope of which was used to determine the scale
> factor."
>
> -" … in the corrector dipoles themselves."
>
> 15. 4.2.2
> - "…using data from the two neighbouring BPMs, the beam jitter and
> drift could be removed …"
> - Figure 13, one plot does not have axes labeled
> - the SVD gets used to tweak the relative calibration constants for
> the "prediction" bpms with respect to the bpm under test; here it's
> described for bpm4 using predictions from bpms3 and 5. Seems that
> when used in combination with the mover scan, this should give good
> accurate calibration constants not just for bpm4 but also for bpms 3
> and 5. Can then apply this to other bpms; ex. Use bpms 1 and 9
> instead of 3,5. why can't we use beam jitter plus the bpm4 mover
> calibration to get all the calibration constants for all the bpms?
>
> 16. 4.3.1
> - it's noted that variation in trigger time was negligible. Would be
> good to quantify this.
> - Table 9; results for bpm4?
>
> 17. 4.5
> - need to quantify results. Linearity to 1%? 0.1%? Should show a
> signed result in Fig. 14 and perhaps show a plot of residuals wrt a
> linear fit. Which bpms are plotted?
>
> 18. 5.2
> - should use standard set of axes in plots for the 20-hour run
> - for figure 16, should comment why bpm4 results are so stable;
> presumably since just use the mover determined scale; indicates that
> similar stability should be achievable at least for 3,5 and likely
> also for 9-11. I think by including a modified calibration procedure
> described above in comment 15 might achieve this.
>
> 19. 5.3
> - prefer a different title for section
> - table 11; why large values for precision for bpm1 and bpm11?
> - figure 19, should label figures a and b (this happens for a number
> of figures); 2nd plot should be 41y? Should comment about not being
> able to remove angle effects with only 2 bpms?
>
> - need more explanation and plot of frequency change in x11
> - need more discussion/investigation of jumps in residual stability
> plots in fig. 23, 25, 26. why are the rms blown up to 20 microns for
> x10,y10 etc.
>
> 20 5.4
> - "one of the primary goals of the commissioning was to investigate
> the dependence …"
>
> 21. 5.4.2
> - give part numbers and references for flux gate monitors; also
> measurement results -- how stable?
> - give equation for prediction of orbit change due to energy change
>
> 22. 5.4.3
> - figure 33 refers to top and bottom plots, but only 1 plot is shown
> - for the 400 micron drift observed, show calculation for expected
> drift versus temperature and plot correlation with temperature. Seems
> too large? Must be 400nm?
>
> 23. 5.4.4
> - would like to see plots of linked residual versus x4, y4, energy, Q;
> need to bin data in figures 34-36
>
> 24. no mention was made of neslab chiller to stabilize bpm cavity
> temperatures; should note this in hardware section
>
> 25. no mention is made of beam quality cuts; do we really make no
> cuts on beam data? Would think we would want cuts on beam loss
> monitors like the bad spill counters and the wire scanner pmt signals;
> also cuts on energy bpm and on pulses with unexpected large orbit
> deviations
>
> mike
>
>
>
> -----Original Message-----
> From: Mark Slater [mailto:slater at hep.phy.cam.ac.uk]
> Sent: Monday, September 10, 2007 4:02 PM
> To: esa-t474 at hep.ucl.ac.uk
> Subject: [esa-t474] 3rd Draft of Paper
>
> Dear All,
>
> I've just uploaded the 3rd draft of the paper to UCL's CVS:
>
> http://cvs.hep.ucl.ac.uk/viewcvs/papers/esaBpmNote/built/?root=ILC
> +Accelerator+code
>
> (note the change in address)
>
> This includes almost all the comments discussed at SLAC during the
> July run with a couple of exceptions, most notably that I could not
> find a way of improving the stability by performing the SVD for every
> set of events as Yury was suggesting. It turns out though, that I
> doubt this would help as we seem to be dominated (with a couple of
> exceptions) by changes in scale based on temperature changes than from
> IQ Phase variations. However that said, we can now demonstrate
> stability of +-100nm over 8 hours which is better than a kick in the
> teeth :)
>
> Additionally, I believe the paper is now self consistent and as much
> as is possible, explains the results that we've reported. However,
> PLEASE CHECK THIS!!! If you could spend some time going over the paper
> and make sure there is nothing missing/contradictory/incorrect/just
> plain dumb. I've now got to the point where I can't really see the
> wood for the trees and so will probably have missed several things.
>
> The plan now is to give 10-14 days for everyone to go over the paper,
> after which, if you could send me comments, that would be very much
> appreciated. Any UK people who can make it (and anyone else for that
>
> matter!) will then hopefully devote a full day to going through and
> making sure everyone's happy. If all goes well, I will then submit the
> paper to NIM by the end of September.
>
> I hope this all makes sense,
>
> Many Thanks,
>
> Mark
>
> _______________________________________________
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>
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