Participant: H Prin (HPN), J Rysti (JRI), G Kirby (GKY), A Foussat (AFT)

CERN Interface meeting MQYY (Q4) , MBRD(D2), MCBYY MCBRD – 2016-05-12

1)     HEX holes position:

•  The HEX holes of both MQYY (Q4) and MBRD (D2) shall be aligned with respect to the position of the corrector holes optimised for field quality: Dia 60mm at 180 from center.
• A solution of replacement of HEX tubes by some finger type exchanger is been assessed by Cryostat, cryogenics and cold mass team;

2)     Alignment surface features :

• CERN alignment tooling dimensioning shall be used to provide the features to mount magnets on the existing alignment table. The distance between two machined reference surfaces of 334 mm shall be respected to match this adjustment tooling

3)     Option of 13kA busbars routing on D2 / Interface with correctors

• The option to connect the D2 on the QQS side was discussed next to the MCBYY location which does not seem the most convenient and reliable especially in terms of maintenance according to HPN. The other option to connect the D2 on the non connection side is more suitable in terms of manufacture access and maintenance. Corrector team proposes to use the right hand side of the top busbar slot on both Q4 and D2 cold masses when looking from QQS side.

4)     Review of the Layout drawings of D2, Q4 cold mass:

•  The updated dimension of the correctors magnetic length has been checked within the layout drawing which is 1890 mm (MCBRD) and (MCBYY). The mechanical lengths for Q4 and D2 are 2175 mm. The interdistance between correctors is minimal to 80 mm on latest integration drawings version ( dated 12/05/2016). GKY mentioned that he would like to study and increase of the mechanical length of correctors up to 2190 mm if possible. ( minimum inter distance between corrector  is 25 mm). As for the distance between correctors and D2, Q4 of minimum 80 and 90 mm, the distances are fixed until INFN and CEA respectively confirm the mechanical length including the structure envelops.

• The pending question of further reduction of distance between correctors , or correctors main magnet is subject to the check of stray head fields: GKY shall provide the stray integral field profile of correctors, and institutes for Q4 and D2 into the extremity heads.

5)     Lifting feature vs. Busbars slots in MCBRD, MCBYY correctors

• Bus-bar slots are compatible with existing lifting tools, and standard design for bus-bar box channel.

• It was noted, we will make a complete study of lifting tools modifications when the design are consolidated.

6)      Mid plane shell welding undercut, limitation on manufacture and field quality

• Small precision undercut 20 mm wide on both sides on horizontal axis,  this is for a stainless steel backing strip that is welded into the yoke providing cold mass alignment and protection for the back of the cold mass weld. Position of this in can be fixed for the CEA  Q4 yoke, however D2 assembly is still under discussion as to the position of this feature. AFT pointed out that this may move depending on final assembly orientation with respect to welding, as we weld half shells together. However, this is not the preferred option and INFN recently confirmed that they could accommodate an undercut, this is to be confirmed once the design is checked by beginning  June.
• Note:  If D2 assembly must finally be welded into cold mass with the apertures one above the other vertically, and the welded shell horizontally either side.  The corrector would need also to  be rotated through 90° and assembled adjacent to D2. However Correctors would then need to move the precision 20 mm slot in the corrector yoke accordingly.  It would not be possible to move the bus bar / lifting / alignment features due to field quality. They would have small modifications that stay essentially where they are in the attached drawing. New lifting tool would be needed. 

• Some extra lengths of shells shall be considered up to 14 m for manufacture prices and welds NDT inspection. 

7)      Shell inner diameters of MCBRD, MCBYY correctors

• Outer diameter of yoke is fixed at 614 mm.  Compatible with future bat180 assembly tooling.  D2 +2 orbit correctors,   and Q4 +2 orbit correctors cold mass assembly tooling should all fit in one design.

8)     Cold mass Shell dimensions of D2:

• HPN mentioned that current shell supplier is limited by 12 m long shells, AFT to check what is impact on the D2 13.1 m long shells on supply cost and schedule

9)     Specific alignment feature of MCBRD, MCBYY correctors

• There is one detail of the external yoke lamination profile that is specific only to the orbit corrector yoke and is not relevant for Q4 or D2 which is the 69.9 flat surface for alignment purpose.

10) Standardisation question of inter aperture distances

• GKY raised the proposal to use a standard interdistance of 194 mm ( same as on Q4 correctors) onto the D2 correctors coupled with the 188 mm interdistance of the D2. This would ease the standardised production of the correctors  and would lower the costs. It seems that geometrically this design would be compatible with the beam shape and a possible shift of the cold tube inside D2 corrector. To be checked by WP3 leader and Beam optics team.

11) D2 corrector Shielding:

• GKY mentioned the option to use the gap between the coil former and the yoke to insert a shielding material.