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[atf2-magnet 30] on ATF2 magnet production



Dear Mr. Jiuqing Wang

This is Ryuhei Sugahara of KEK. We, Masayuki Kumada, Mika Masuzawa and myself,
visited SLAC for May 10-12, and had meetings with Cherrill Spencer and her
colleagues on ATF2 magnets, field measurement, power supplies and movers. Please
take a look at the summary of these meetings posted in the following web site:
http://acfahep.kek.jp/subg/ir/minutes/transparency/d050518/sugahara.pdf

In this meeting, discussion has been made on who is responsible for each part of
job, and decided as follows:
   Coordination --> Cherrill Spencer (SLAC), Ryuhei Sugahara (KEK), and
                    Junji Urakawa (KEK on budget)
   Magnet design --> Masayuki Kumada and Cherrill Spencer
   Magnet field measurement --> Mika Masuzawa
   Power supplies --> Masayuki Kumada and Cherrill Spencer
   Movers --> Ryuhei Sugahara and SLAC

e-mail addresses of these people are
   Cherrill Spencer: cherrill@xxxxxxxxxxxxxxxxx
   Ryuhei sugahara: sugahara@xxxxxxxxxxx
   Masayuki Kumada: mkumada@xxxxxxxxx
   Mika Masuzawa: mika.masuzawa@xxxxxx

You can take contact with these people on each subject.

Following is a part of the summary of meetings at SLAC on magnets and field
measurement. I have inserted comments and questions to you, IHEP people, after
"=>" marks. Please read this and respond to me.

1. Variety and number
                                                   Number     L (cm)[given in
optics deck]
     B-mag                                            9           100
     Q-mag (except for final doublet)     25+1(spare)    20
     Final doublet Q-mag                         2          40/50
     Sextupole-mag                                 5            20
     Octupole-mag                                  3       10/20/30 --> all 20?
     --> In the oct-mag area,  spaces between adjacent magnets are as tight as
         only 2.5cm. Are those octupoles really needed? How about some very
         short permanent magnets?
     Steering-mag
     --> Some number of steering magnets will be necessary. Beam optics people
         should study how many magnets are necessary and where, and let us
         know.
    * All the magnets should have some number of spare coils.

- Production of all the magnets except for those reused from SLAC magnets will
  be ordered to IHEP. Fabrication specification should be sent to IHEP before
  end of June.
  --> Cherrill and Masayuki are responsible for designing magnets. They will try
      to make a technical specification before middle of June, and will ask IHEP
      to make the fabrication drawings that need to be changed from the KEK
      design.

=> No magnets will be reused from SLAC magnets at present.
=> Production of some number (about 20?) of Q-mag will be ordered to IHEP
     this fiscal year (April 2005 - March 2006). You should be able to deliver
     all of these after field measurement before the end of March 2006. How many
     Q-mag can you make this fiscal year?
=> We want to ask production of more magnets to IHEP next fiscal year. Those
     should be delivered before the end of September 2006. How many and which
     type of magnets can you make?
=> We, Spencer, Kumada, Sugahara, and possibly Masuzawa, will visit IHEP
     around middle of June after making specification for magnet production.

- Want to make the shape of dipole magnet rectangular (=not pole face rotated).
-Should the core be lamination type or block type?
  --> Lamination type is preferable because of the speed of response, says
      Kumada-san, but there is not agreement yet on this point- need more
      discussion, and to talk with IHEP engineers.

=> I think you have a capability of making lamination type magnets. Do you
     have any preference on lamination type or block type?

2. Tolerances --> Beam optics people are working on this matter.
 Definition of  Good field region
      B-mag:  X = +/- ???mm,  Y = */- ???mm
                   dBL/BL < ??? (we need to know from beam opticians)
      Q-mag:  r = 10mm
      Sx, Octu-mag:  r=10mm

on Q-mag
   Amplitude of multi-pole component (allowed component)
      < 10^ -2
   Amplitude of multi-pole component (not allowed component)
      < 4*10^ -4  for n=3 component in usual Q-mag
      < 10^ -4 for n=3 component in the final doublet  -->  need some correction
        scheme in beam optics in case we cannot achieve this?
Stability
      Short term stability
      Long term stability --> may both be corrected by feed back scheme.

3. Restriction from cavity BPM on Q-mag
     Coils and fixing plates between poles should keep out of the area r=100mm.
      Edge of coils should not far from the edge of magnets 60mm or more.
      --> This tolerance has been relaxed to 70mm after talking to Honda on
          May 26.
      Need to install some tapped holes to fix BPM at the end plate of magnets.

4. Magnetic field measurement
- All magnets should be measured at IHEP to check out possible fabrication
  errors, and feed it back immediately if there are any errors.
  IHEP has a capability of measurement with rotating coils.

=> Can you measure  magnetic field with rotating or harmonic coils? Radius of
     measuring coils should be less than 15mm because bore radius of Q-mag
     is 16mm. 10mm is preferable because the magnetic field and multi-pole
     component amplitude should be defined at r=10mm.
     Required precision on sextupole component measurement will be the most
     strict.
     Measurement least value should be B2(r=10mm)/B1(r=10mm) ~ 10^-4,
     where B1(r=10mm) is Q-field at r=10mm, and B2(r=10mm) is Sx-field
     at r=10mm.

- KEK should have measuring capability to compare IHEP results with measurement
  of ATF magnets. And interference between Q-mag and adjacent steering magnets
  may be measured.
- ATF group's rotating coil is available. They have one set.
       Long coil: 400mm long, and 30mm in diameter.
       Short coil: ??? long, and 30mm in diameter.
       Both have no bucking coils or second coil.

- SLAC has three rotating coil rods which have the diameter 25mm and the length
   ???/???/???. Those have double coils.
   But it is not good idea to send magnets from IHEP to SLAC, then from SLAC to
   KEK for the field measurement because it is time and money consuming.

- If the tolerance for the amplitude of multi-pole component 10^-3 or looser in
  the ratio of B(n-1)/B1 at r=10mm, no bucking coil will be necessary.
  SLAC is making a new rotation coil 25.4mm with two coils.  If double coil is
  necessary in ATF2 magnet measurement, SLAC can make extra coils for KEK and
  IHEP as well.