Meeting Minutes from MCBRDP4 – Mon. 25 ^th April 2022

Attendees:  Arnaud Foussat (AF), Veronica Ilardi (VI), Davide Tommasini (DT), Francois-Olivier Pincot (F-O), Ahmed Benfkih (AB), Glyn Kirby (GK)

Excused:, Helene Felice (HF), Cedric Urscheler (CU),

• NC on AP1 vacuum pressure impregnation : discussion and actions
  • The recording of the temperature profile along the AP1 former shown some failure at the 120 deg C on the third heater at end. The issue is confirmed by the same temperature readout on extremity inner and outer T sensor at 20 deg C below the plateau measured at 125 deg C on others 4 sensors .
  • As the issue occurred at the onset of  the 120 deg C curing plateau it might be linked to damage of solid state switch. F-O will check it.
  • DT mentioned that the outcomes of the resin post curing cycle tests performed on samples will be discussed next Wednesday in order to confirm which temperature cycle can be applied on the aperture partially cured. It was discussed  that it is not clear if this post-cycle would modify significantly the resin properties but nonetheless this will be applied as recommendation to be close to baseline process.
  • The necessity of extracting temperature records in an easy way and during the operation was discussed.         F-O will make a proposal of improvement. The pressure and flowmeters records are already accessible through Labview DAQ. 
  • The findings observed on the faulty impregnation heater during the VPI of AP1 will be reported in the coming NC prepared by VI for our first review

• NC on AP2 inner layer winding
  • Some local damage of the wrapped Kapton cable insulation is observed at the location of joint overlap in the heads corners on top side. The check of insulated cable seems to confirm the overall thickness of 0.97 mm produced of two overlapped layers of 25 microns ( 0.075 + 0.825 mm SC diameter + 0.05 mm + glue thickness)  insulation.
    • AF will take a Parsch and CGP wire insulated samples to EN MME to ask cut section dimension inspection and confirm the insulation layer layout.
    • At moment, the electrical test on dry AP2 inner winding at 500 V passed.
  • It was discussed that the relatively sharp edges of AP2 inner former anodised groove edges although deburred by hand could be one of the cause of cable insulation damage combined with the use of the guiding jig. AF noted that there is no specific tolerance on corner radius of groove walls defined in drawings MCBRD0029 nor 0030 except per the general ISO 2768mk ones.
  • Comparison with IHEP formers: The state of groove edges was checked on the recent delivered units by IHEP: the inspection shown much smoother edges and safer for windings. Unlike the CERN specification, drawing AF has checked that the IHEP drawings include a specified corner radius is 0.1 mm. It will be asked how this is achieved. The color of anodisation of IHEP anodised single sample seems to indicate a soft anodisation instead of hard one as per CERN one. This point will be checked with IHEP.
  • As the AP2 outer former is already anodised it is judged too difficult and risky to try to smooth the edges. Sprayed PTFE could be used to fill the edges of groove and ease the winding providing the product is compatible with the impregnation process. No resin bonding is needed in the groove.

• Additional IHEP formers metrology to be discussed with CERN lab

• In addition to the standard CMM metrology plan agreed, some more measurements were discussed :
  • Check on one inner and outer former of the apex groove on top and bottom angular position with respect to the pin holes per drawings.
  • Measurement of the anodisation layer thickness by EN MME on inner IHEP former