Orbit Correctors in D2 and Q4 Design options J. Rysti and E. Todesco 17/09/2014 xxx

Requirements Integrated field 4.5 Tm. Multipoles below 10 units at all operational fields and configurations. First-guess layout (baseline): 3 T field, two units 1.5 m long, one H and one V. 105 mm diameter apertures Cross-talk problem Not enough iron between apertures 17/09/2014 xxx

How to fix the problem? Here we have tried to see how to optimize the field quality with the given constraints in a twin aperture configuration. This is not a detailed design proposal. Reduce aperture diam. 105 mm -> 100 mm. H/V configuration For H/H: B3 > 120 units at 2.7 T and for H/V: ~10 units). 17/09/2014 xxx

Various designs studied 17/09/2014 xxx

Best found design 17/09/2014 xxx

H/H vs. H/V 17/09/2014 xxx

Best found design 17/09/2014 xxx

Multipoles in aperture 1 (left) All other multipoles are below 1 at all fields 17/09/2014 xxx

Multipoles in aperture 2 (right) All other multipoles are below 1 at all fields 17/09/2014 xxx

The other magnet turned off 17/09/2014 xxx

Low field, changing other magnet 17/09/2014 xxx

How to implement this design Collars from soft iron or thin steel collars? Iron strong enough, but pre-stress lost in cooling. Thin steel collar (6 mm) not strong enough and difficult to make. No collars, compress entire yoke? Challenging & cannot test magnets individually. Increase collar thickness: At 6 mm: max field 2.73 T At 10 mm: max field 2.65 T At 15 mm: max field 2.56 T 17/09/2014 xxx

15 mm collars 6 mm ”collars” 17/09/2014 xxx

6 mm vs. 15 mm collar/spacer 17/09/2014 xxx

Laminated iron/steel collars? Make the ”floating collars” from iron. Using stacking factor 0.5 in ROXIE iron file. Preliminary results not very good (B3 > 100). Fessia & Perini, IEEE Trans. Appl. Supercond. 12, 202 (2002). 17/09/2014 xxx

Other options Nested H & V dipoles in a single aperture. Staggered magnets (double required length). Exotic possibilities: NbTi sheets between apertures to shield fields? 17/09/2014 xxx

Conclusions Requirements fulfilled up to 2.7 T. 15 cm per magnet more length copared to baseline (1.5 m). Mechanically difficult. With realistic collars (15 mm) max field down to around 2.5-2.6 T. 25-30 cm per magnet more length compared to baseline (1.5 m). 17/09/2014 xxx

Remarks If aperture 1 goes from 3 T to 0 T, aperture 2 changes 0.02 T (0.8 %). If aperture 2 goes from 3 T to 0 T, aperture 1 changes 0.03 T (1 %). In aperture 1, ~15 units of A2 at 3 T. In aperture 2, >20 units of A3 & B3 at 3 T. Some constant multipoles around or above 10 units (B7/A7 ~11 units, B5/A5 ~8 units). These may be possible to correct with further optimization of the configuration. 17/09/2014 xxx

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