11 T Dipole EM Design & Quench Analysis

11 T Dipole EM Design & Quench Analysis

B. Auchmann & M. Karppinen CERN TE-MSC

B. Auchmann & M. Karppinen CERN TE-MSC 2

Magnet Design Constraints

• ∫BdL = 119.2 Tm @ Inom = 11.85 kA• 2-in-1 design, intra-beam distance 194 m• Cold mass outer contour from MB• Heat exchanger location as in MB• Aperture: Sagitta: 11 m – 5.0 mm, 5.5 m – 1.3 mm

=> Ø60 mm aperture and straight cold mass • 20 % operation margin on the load-line at 1.9 K• Field harmonics at 10-4 level (TBC by AP)

13 May 2011, Collaboration Meeting


11 T Model Program



Cable & Insulation

250 m Nb3Sn cable produced Jc measurements underway

First CERN cabling run expected Beg-May



Measured Jc of OST 108/127 RRP strand (40-strand rectangular cable)

Courtesy of E. Barzi, FNAL



2D-Models used for Coil Optimization

1-in-1 Yoke ID/OD 130/400 160/400 200/400 200/550 160/550

B0(T) 11.66 11.22 10.76 11.20 11.67

11.21 T 6-Block design, 56 Turns, no core



Possible Coil X-Sections

6 Blocks56 turns

7 Blocks56 turns

6 Block SS Core58 turns

6 Blocks SS Core55 turns

7 Block SS Core55 turns



Parameters of Coil X-Sections



2-in-1 & 1-in-1 Models

B0(11.85 kA) = 11.21 T

B0(11.85 kA) = 10.86 T



Iron Saturation

Relative permeability Induction (T)

Relative FQ (units)


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EM Forces

Total Fxaperture = 634 ton/m (MB = 428 ton/m)



Working point & MarginsMeasured JcOST 108/127Ø0.70 mm10% degr.

80.4%

Bpeak(T)

Tmarg(K)Margin(%)



End DesignUp-right End Minimum Strain End

• Based on FNAL experience• Smaller voids to fill on yz-plane• More hard-way strain during winding• 2 winding blocks on the outer layer ends

• Based on CERN experience• Larger voids to fill on yz-plane• Minimum hard-way strain during winding• 3 winding blocks on the outer layer ends



Cotronics Ceramic Putty used at CERN



Selective Laser Sintering End Spacers (Stainless steel)



Coil Ends & Practice Coil

First practice coil wound with rectangular Cu-cableand stailess steel SLS end spacers

First Nb3Sn (114/127) practice coil will be woundas of 9 May.

Different end spacer designs will be used in lead and return ends.



3D Models

Yoke cut-back determined such that the Bp is in the straight section

1-in-1 Demonstrator DipoleYoke covers the ends.=> Bp = +0.25 T



Design Parameters

Note: Cryostat, beam-screen, beam-pipe, (slight) permeability of collars not included13 May 2011, Collaboration Meeting


MCBM 1.9 Tm @55 AMCBCM 2.8 Tm @100 AMCBYM 2.6 Tm @ 88 A

Transfer Function Correction

Below Inom 11 T Dipole is stronger than MB



C8 C9 C10 C11 C8

RB.A23

Total inductance:15.5 H (152x0.1H + 2x0.15H)Total resistance: 1mWOutput current: 13 kAOutput voltage: 190 V

Trim1

Trim2

Main Power Converter

0.1H

0.15H

Total inductance: 0.15 HTotal resistance: 1mWRB output current: ±0.6 kARB output voltage: ±10 V

TRIM Power Converters

(+)• Low current CL for the trim circuits• Size of Trim power converters

(-)• Protection of the magnets• Floating Trim PCs (>2 kV)• coupled circuits

New RB Circuit (Type 1)

Courtesy of H. Thiessen13 May 2011, Collaboration Meeting


Nested Trim Circuit

11 T Dipole current needs to be reduced



Coil MagnetizationMB (NbTi) 11 T Dipole Nb3Sn

Mid-Plane Inner LayerMid-plane Outer layerInner Layer PoleOuter Layer Pole

>10 X



Persistent Current Effects


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B. Auchmann & M. Karppinen CERN TE-MSC 2613 May 2011, Collaboration Meeting


dynamic aperture for ...ideal Nb3Sn dipoles (red) full error table (green)

and for completeness: limits in DA for the phase 1 upgrade study (blue)

for the experts: the plot shows the minimum DA for the 60 error distribution seeds used in the tracking calculations.

Field Quality: Dynamic Aperture StudiesCollision optics, 7 TeV

dyn aperture luminosity optics, 7 TeV, minimum of 60 seeds

Courtesy of B. Holzer



dynamic aperture for Nb3Sn case: full error table, b3 = 98 units (red) b3 reduced to 50 units (green)b3 reduced to 25 units (violett)b3 = 0 and to compare with: present LHC injection

for the experts: unlike to the collision case: at injection the b3 of the Nb3Sn dipoles is the driving force to the limit in dynamic aperture.A scan in b3 values has been performed and shows that values up to b3 ≈ 20 units are ok. Alternative solution: strong local spool piece corrector

Field Quality: Dynamic Aperture StudiesInjection optics, 450 GeV, no spool piece correctors

dyn aperture injection optics, minimum of 60 seeds

Courtesy of B. Holzer



Quench Heaters

Parameter Value

Conductor cross-section (mm2) 15.4

Cu/Sc ratio 1.106

RRR 100

Iultim. (A) for 12 T 13250

Diff. Inductance @ Iultim. (mH) 9.13

Stored energy @ Iultim. (kJ) 969

Temperature margin (K) 4 – 12



Protection Studies 1/2

Protection studies in progress in both labs:

• The 1-in-1 Demonstrator can be protected with energy extraction system and heaters

• The heater design and powering electronics are subject of R&D.• The Demonstrator test is a good opportunity for extensive

protection studies:• Extraction and heater delays• Heater efficiency and required coverage• Quench propagation• Quench-back



Protection Studies 2/2

Enthalpy margin to quench (mJ/cm3)

Protection-heater experiments will provethe efficiency of the protection system.

Simulation shows heater delays between2 and 20 ms.

Impact of instabilities and cable eddy-currents?(cored vs. non-cored cable)


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Summary• The magnetic design of the 11 T Dipole magnet is based on magnet technology

proven by the HFM programs and LHC magnet production.• Magnet design parameters meet the requirements of the LHC Collimation phase II

upgrade.• The engineering design of the 2-in-1 demonstrator is in progress. It will be the first

accelerator quality 2-in-1 Nb3Sn magnet. • First optics studies:

– Orbit error due to the TF of the 11 T Dipole can be corrected by using a significant factor of corrector strength outside of DS. Trim PC would solve the problem.

– b3 @450 GeV can be tolerated up to ˜20 units, which seems achievable (passive shimming, B3 corrector..).

• 1-in-1 Demonstrator magnet will demonstrate the quench performance and operation margin up to the design field of 12 T and give valuable experimental data on the magnetization effects:– Measured magnetization effects will serve to validate the numerical models.– The 1-in-1 Demonstrator dipole can be protected with an external dump resistor. – The 1-in-1 Demonstrator will serve to validate the protection system based on heaters for the

accelerator application.



R&D Topics• End part design• Magnetization effects control• Fast power abort tests (quench-back)• Quench protection:– Quench analysis tools– Heater system design– Heater studies


11 T Dipole EM Design & Quench Analysis

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