1. An alternative approach to the design of the corrector magnets
Giovanni Volpini CERN 21 January 2015

3. Giovanni Volpini CERN 21 January 2015
Sextupole lay-out
Giovanni Volpini CERN 21 January 2015

4. Giovanni Volpini CERN 21 January 2015
Working principle
Ampère’s law, of course, but beware of the intregration circuit! C
In the limit µr=∞, net contributions to integral come from AB and EF only B
Return yoke A D E
High saturation zone F
Pole Expansion
Giovanni Volpini CERN 21 January 2015

5. Giovanni Volpini CERN 21 January 2015
Coil budgetary design
Superconductor :
Tape 3 x (0.5(SC) +0.2(Cu) ) mm², Ni-matrix, external Cu stabilized, multifilamentary, ex-situ MgB2 by Columbus Superconductors, Genova, Italy
Ic T, T, 4.2 K (high purity B powder)
Insulation scheme :
SC tape : S2 tape, 0.1 mm thick (per side)
Ground and layer-to-layer : 0.2 mm thick impregnated fiberglass
Coil type :
36 x 2 turn double pancake, ID OD height = 8 mm
MgB2 tape has a minimum bending diameter >120 mm, so it is definitely OK
Jop = 100 A / mm²
Giovanni Volpini CERN 21 January 2015

6. Giovanni Volpini CERN 21 January 2015
Field Map
Giovanni Volpini CERN 21 January 2015

7. Giovanni Volpini CERN 21 January 2015
Field Map
Superconductor :
Tape 3 x (0.5(SC) +0.2(Cu) ) mm², Ni-matrix, external Cu stabilized,
Giovanni Volpini CERN 21 January 2015

8. Giovanni Volpini CERN 21 January 2015
L iron 200 mm
Jop = 100 A / mm²
∫ b T·m, b9 ~ 2.5 units (real iron)
∫ b T·m, b9 ~ 4 units (linear iron)
Design ∫ b3 = T·m
Giovanni Volpini CERN 21 January 2015

9. Stray flux
Some improvement of performances could arrive from an optimized design of the pole profile which reduces the stray flux
Pole Side 6.4/1.9
Pole Back 4.4/1.9
Pole Tip 5.1/1.6
Flux in mWb
Linear Iron/Real Iron

10. Giovanni Volpini CERN 21 January 2015
conclusions
Simpler coil design, very well suited to strain-sensitive supercoductors
especially adapted to higher order correctors
Not (yet) competitive with the «traditional» design; the limitation comes from the saturation in region near the coil:
Performances could be boosted by use of FeCo in the high-saturation region and by an optimized iron design.
e.g. a b14
Giovanni Volpini CERN 21 January 2015