Summary of Visit of CPL and IPJ from 7th to 8rh April 2011:

Participant Institute Function
Pawel Krawczyk IPJ general manager
Marcin Wojciechowski IPJ project coordinator
Marek Marczenko IPJ machining coordinator
Michal Grabowski IPJ machining
Grzegorz Brzezinski IPJ metrology
Jan Litwiniuk CPL director CPL
Frank Gerigk CERN project coordinator
Rolf Wegner CERN project coordinator
Maurice Favrel CERN machining

Presentations given, attached at the end or in separate files
Presentation Frank, "Frank Linac4 & PIMS Schedule - 2011_04_07", very short summary:

  • Linac4 schedule: cavity installation finished in March 2013, commissioning starts in May 2013
  • PIMS prototype successfully built and tested at CERN, will be 1st PIMS module
  • PIMS schedule: 1st cavity June 2011, last cavity (no 12) June 2012 delivered to CERN precise schedule after construction of 1st cavity

Presentation Marek, "Marek PIMS construction at IPJ 2011_04_06", very short summary:

  • Machining of Rings
  • Metrology of end disc, Metrology Lab and Tools
  • Temperature compensation for final machining
  • Transport boxes
  • Tools for final machining

Presentation Marek, " Marek foreseen PIMS schedule 2011_04_07", very short summary:

  • 1st cavity at CERN end of June 2011
  • 1 month construction stop
  • Machining of cavities in groups of 3 from August 2011 onwards
  • Last cavity at CERN mid July 2012

Description of CERN procedure, "Gilles - CERN Machining_Procedure"

  • Gilles has written a very compact and detailed description of machining procedure used at CERN. It was not discussed again but as it is an excellent reference, this document is attached again

Status:

  • 2 end discs are rough machined
  • 1 disc is rough machined
  • Several rings are being rough machined
  • Tools for milling tuner and RF ports are ordered. A standard angular head was used at CERN for holding the tool and avoiding vibrations (http://pibomulti.com/).
  • Ring used for first tests has too much deformation to be used for a PIMS cavity. Further tests will be conducted to see deformations of milling holes for tuner and RF ports, deformation changes after next turning operation, fine machining tests and maybe welding tests

Discussion of machining principle:

  • Milling of rings and discs: final machining is proposed to be done by milling
  • Doubts of surface quality, deformations during milling, tight tolerances, concentricity if machined from 2 sides
  • For compensation, several steps are foreseen, critical diameters are finished at latest state. Buncher cavity was milled and was ok, waveguide ring of CERN prototype was milled and was ok
  • IPJ is working on a backup solution in case final machining cannot be done by milling
  • Conclusion : test pieces of 2 end discs, 1 disc and 2 rings will be produced, measured at IPJ and sent to CERN for further inspections. 1st ring will be rough machined by turning and finished by milling, 2nd ring will be done by milling (rough and final machining).

Strategy and open questions:

  • Test pieces need to be evaluated to qualify the milling operations, especially for the fine machining of the rings.
  • No final machining of further parts until quality of test pieces has been confirmed
  • Influence on schedule. Open questions how to compensate the corresponding delay in production (see action list at end): Is the evaluation of these test pieces sufficient for quality assurance of all cavities? Is a full cavity (N) needed for qualification? Is a 2 month stop of machining needed after 1st cavity sent to CERN? This will be discussed at CERN with advice from the CERN design office and CERN workshop.

Machining strategy, baseline:

  • Rings: rough machining (turning) IPJ, cleaning IPJ, welding Juelich, X-ray IPJ, fine machining (milling) CPL, cleaning IPJ, metrology IPJ
  • Waveguide Rings: rough machining (milling) CPL, cleaning IPJ, stabilization IPJ, 2nd rough machining CPL, stabilization IPJ, cleaning IPJ, final machining CPL, cleaning IPJ, metrology IPJ, brazing IPJ, metrology IPJ, tests
  • Discs: rough machining (milling) CPL, fine machining (milling) CPL, pressure test IPJ, cleaning IPJ, metrology IPJ
  • End Discs: rough machining (milling) CPL, fine machining (milling) CPL, pressure test IPJ, cleaning IPJ, metrology IPJ
  • Tooling: IPJ

Metrology:

  • Metrology lab well equipped
  • Precision better than 2.5 um
  • Repetitive tests have been performed with hit points and scanning (see attachments), excellent agreement was found.
  • Temperature is compensated in the range of 18 to 22 degrees.
  • The metrology lab needs to be temperature stabilised: 1 degree temperature increase let rings of 540 mm expand by 9 um. The specified tolerance for this outer diameter is 10 um!
  • Windows will be exchanged and sun-blinds will be installed to avoid heating of measurement table or parts by the sun
  • Equipment available to measure and calculate temperature compensation in machining hall (summer time)

Transport:

  • Wooden boxes for transport have been developed and built by IPJ. Robust design, several boxes can be positioned on top of each other
  • CERN experience for transport of fragile parts:
  • A layer of styrofoam (expanded polystyrene) is placed on the wooden base plate and shaped according to the parts to be transported (flat styrofoam plate for rings, styrofoam plate with hole for noses of discs). Thickness: At least 20 to 30 mm of styrofoam should carry the weight.
  • A layer of bubble wrap is placed below the copper parts to protect sensitive surfaces / edges (http://www.google.de/images?q=bubble%20wrap)
  • Cleaned copper parts are placed in plastic bags which are filled with Nitrogen
  • Flanges are protected with plastic covers, for the waveguide flange a protection cover should be machined (design SPLACPMT0102)

Cleaning, "Marina - Cleaning copper procedure":

  • Procedure used at CERN for cleaning copper parts is attached again
  • Further details have been discussed:
  • Waveguide rings: full procedure before brazing (steps 1 to 11)
  • Standard rings: full procedure (steps 1 to 11) for ports before brazing and full procedure (steps 1 to 11) for rings before welding tuner ports. After brazing, etching is not allowed anymore (oxidation of brazing). So after welding and final machining only degreasing (steps 1 to 3) and final cleaning (steps 8 to 11)
  • Discs: degreasing of discs and cooling channels (steps 1 to 3), closing of cooling channels important as acids will remain in channels otherwise, pickling and passivation of discs (steps 4 to 7 D), steps 8 to 11 also for cooling channels

Agreement on relaxation of tolerances:

  • Copper rings deform after relaxation from clamping devices
  • Average diameter (defined by circumference / pi) must be within tolerance
  • Ring profile measured with at least 120 points to determine deviation from perfect circle
  • An ellipticity of 0.2 mm can be tolerated after final machining Ellipticity meaning a deviation from perfect circle in form of an ellipse, having 2 maxima and 2 minima in radius over the full 360 degrees - compare metrology reports attached (with other words, having 1 semimajor axis and 1 semiminor axis). Deformations that have more than 2 maxima / minima can not be accepted because assembly and disassembly are too difficult as more than 2 places would need to be deformed at the same time.
  • After rough machining, an ellipticity of 0.1 mm might correspond to the acceptable ellipticity after fine machining (indication, needs to be verified)
  • Remark: A technique to cure large deviations by plastic deformation of rings with a press (in emergency situation) can be applied between rough machining operations. However a further rough machining operation is required afterwards, otherwise deformation with more than 2 maxima / minima in radius might remain.

Material:

  • One copper ring has been found with 2 material faults, which were discovered during rough machining. Hopefully they are not deep so that they disappear after rough machining.

Discussions:

  • Machining of pin holes for metrology targets into discs. At CERN the pin holes were machined as last operation of discs (compare "Gilles - CERN Machining_Procedure"). Action: Please check the position and orientation of the pin holes in the test disc carefully to verify the procedure of machining the pin holes in two steps.

Next visit:

  • Planned around mid May

Production of target holders needs to be delayed until the design is updated.

We would like to thank our Polish colleagues for the good time and the extraordinary hospitality!



More details and attachments here: (restricted access) https://edms.cern.ch/document/1141661

-- RolfWegner, 12. April 2011

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