1. Update on the CCT Option
EuroCirCol WP5-CM 17
Bernhard Auchmann (CERN/PSI), C. Calzolaio, R. Deckardt, R. Felder, C. Hug, M. Negrazus, S. Sanfilippo, S. Sidorov (PSI), L. Brouwer, S. Caspi (LBNL)

2. Overview 3-D E-mag design Towards 3-D mech design
Former manufacturing status

3. Peak-Field Enhancement
Assumption: since CCT magnet does not have a structural discontinuity between straight section and ends, it shall suffice to avoid any peak field enhancement in the ends.
Study: 240 turns of CCT yield 2-D conditions in the magnet center.
Peak-field enhancement for yoke-length = coil length: T (deemed acceptable).
Study by Marco Negrazus

4. Magnetic Length vs. Phys. Length
Mag. length without iron: #turns x pitch length, 240 x mm = 2.65 m.
With iron extended over whole coil: m, almost identical!
Physical length: 3.2 m.
Nb3Sn/Nb-Ti splice is made within the coil length.
Assuming that no endplates are needed for CCT, this compares well to 11-T numbers:
Study by Marco Negrazus
From F. Savary, ”The 11 T Dipole for HL-LHC – CERN”, June 2016

5. Coil Peak Field 3-D Calculation
Without iron, ROXIE-like peak-field calculation (without self field) agrees with Opera calculation to within 0.02 T.
With iron, Opera yields 0.14 T peak field enhancement.
Strand self field from 0.21 T (1st layer) to 0.3 T (4th layer).

6. V3 with Updated Peak Field
Coil data
Current: A
Conductor use
Total: 9.77 kt (+0.3 kt)
NonCu: 3.75 kt
Cu: 6.02 kt
Total inductance: 19.2 mH/m, Total energy: 3.2 MJ/m
Layer # nS
cuNc
“nTurn”
loadline
marg.
current
Tpeak
[K]
Vgrnd
[V]
Jcu
[A/mm2] 1 29
0.8
18.0
14.3
111
292
1133
1237 2 25
1.1
32.
14.4 95
342
1264
1217 3 22
1.95
43.5 74
310
1156
1096 4 20
2.6
54.5
15.7 71
338
1144
1103

7. Combined Function CCT
Idea, implement FD quad strength into the dipoles.
Antoine Chance (CEA) computed a feasible lattice with B2 = 25.5 T/m in the dipoles and B1 = T.
On the peak-field conductor this yields T.
The reduced cell-length of m wrt. standard 215 m requires ~5% more dipoles, i.e., the scheme cannot pay off, in my opinion.
Moreover, the strong quadrupole component is difficult to implement.
(The naïve assumption of 400 T/m x 1.5 m / (6 x 14.3 m) = 7 T/m with unchanged cell length had looked promising, but was flat-out wrong.)

8. Overview 3-D E-mag design Towards 3-D mech design
Former manufacturing status

9. Axial Thermal Contraction Problem
In 2-D, we can choose between plane stress and plane strain, usually selecting plane stress.
For a periodic 3-D model, we must impose a constraint on pairs of nodes on the respective periodic planes.
Plane strain corresponds to coupled movement in z, or ∆z = 0 (difference in axial movement between nodes vanishes).
Plane stress would corresponds to ∆z values that make the axial forces on the respective nodes vanish (determined iteratively).
Or should we cancel the overall integrated axial force by setting a single ∆z value for all node pairs?
Or should we apply the latter procedure per component (shell, yoke, coil)? LBNL tends towards the latter.

10. Status
Gabriella Rolando created a 3-D periodic model with scissor laminations.
Initial results for ∆z = 0 (plane strain indicate) large axial strain, as was expected.
Peak stress at boundary surface indicates artefacts from improper boundary condition.
Further optimization of the model is under way in preparation of much more detailed study.

11. Overview 3-D E-mag design Towards 3-D mech design
Former manufacturing status

12. Former-Manufacturing Challenge
LBNL
Conventional machining:
Deep grooves (>10:1 aspect ratio).
Tilted wrt. radial position  5-axis machinig.
So far one company found who dares to quote for con- ventional CNC machining, but quote not yet received.
6 companies have declined.
Alternatives:
3-D printing in stainless steel.
Issue with surfaces hanging at angles < 45˚
Build volumes require combination of parts.
Printing of thin “skin”, to be honed off later, might help with both issues.
Building former from thin laminations.
Process-development under way with Swiss company and Frauenhofer institute to set up an additive-manufacturing process based on steel laminations and laser spot-welding.
PSI