1. STEAM Applications Part I The circuit point of view
4th STEAM Collaboration Meeting, Darmstadt, Sept. 2017
STEAM Applications Part I The circuit point of view
M. Prioli and the CERN side of STEAM
S. Ambjørndalen, B. Auchmann, L. Bortot, A. Fernandez, J. B. Ghini, M. Maciejewski, M. Mentink, A. Verweij

2. The circuit point of view
Simulation conventions: SPICE solvers, netlist format, modular libraries
Extended modelling capabilities to fit actual needs
* Quench Protection System
QPS*
Trim PC
Lfilt
Rfilt
Cfilt M1
M77
M78
M154
REE1 PC
REE2
SC Busbar
Cont.
CLIQ*
* Coupling Loss Induced Quench protection system
The behaviour of these additional components cannot be fully captured in the circuit model (nonlinearities, no equivalent lumped element model)
Dedicated models

3. Magnet impedance
Still “part” of this behaviour needs to be modelled in the circuit
Magnet impedance at the operating point
Why?
Mn: Model preconditioning → convergence, limit the number of iterations Evidence: simple inductor is enough
M1-M154: Accuracy in the circuit results Evidence: a simple inductor is not enough
Lfilt
Rfilt
Cfilt M1
M77
M78
M154
REE1 PC
REE2 Mn
Field-circuit coupling

4. Magnet impedance How ? Circuit measurements: MB
Magnet measurements: MB, 11 T, MQXF, magnet prototypes
FE models: future magnets

5. A. Circuit measurements
Lossy inductance model
Ap1
Ap2
X 154
-- measurement
– simulation
2 kA
10 kA

6. A. Circuit measurements
Influence of the rest of the chain of magnets
Fit accuracy decreases at higher frequencies
Is the obtained model accuracy enough for the STEAM applications?
S. Ambjørndalen Master Thesis (link)

7. Application 1: short to ground
A: short appearing
B: fuse blows
Continuous lines: measurement
Dashed lines: simulations A B A B NP PN
Quenched before the short
Family NP
Family PN

8. Application 1: short to ground
Simulations
Measurements
Seen as quenched
“Almost” seen as quenched

9. Application 2: double short to ground
Quenched before the shorts
Edebris 1,2 = 3 kJ
Eshort 1,2 = 22 MJ
E EE2 = 80 MJ
E EE1 = 800 MJ 9

10. Application 3: dipole circuit improvements
Damp the oscillations on the magnet voltage to reduce spurious triggers of the protection system
10Ω + 10mF

11. Application 4: inter-turn short
Assumptions:
Location of the short in the inner layer, pole block.
Inter-turn short only present at high current, disappearing at low current ( A).
Good agreement:
the observed QPS signals are compatible with the theory of an inter-turn short.
Courtesy of M. Maciejewski

12. B. Magnet measurements
Some applications indicate the need for more refined circuit models
Measurement conditions:
Current: 0 A ± 1 A rms
Temperature: 300 K K
From “Opportunities in High Magnetic Field Science”, 2005

13. B. Magnet measurements The persistent magnetization effect
𝑀 𝑃𝑒𝑟𝑠 ∝ 𝐽 𝑐 (𝐵,𝑇)
1 A
1 kA
S. Ambjørndalen Master Thesis (link)

14. C. FE models From COMSOL : “
In Which Regime Is Frequency Domain Wave Electromagnetics Modelling Appropriate?
Whenever we want to solve a modelling problem involving Maxwell’s equations under the assumption that:
All material properties are constant with respect to field strength
The fields will change sinusoidally in time at a known frequency or range of frequencies ”
Magnetic fields
frequency domain form
Electrostatic
S. Ambjørndalen Master Thesis (link)

15. Application 5: future accelerator circuits
Long chains
Of high-energy magnets
Nominal field [T]
Bnom [kA]
Differential inductance (2 apertures) [mH]
Stored Inom (2 apertures) [MJ]
LHC MB dipole
8.33
11.85 98 7
FCC Cos-theta 16
11.23
566 38

16. Application 5: future accelerator circuits
PCs 1
PCs 2
PS 1
PS 2
Half-arc
8 km
Proposal for FCC Powering Sectors (PS)
Proposed circuit layout to reduce the stored energy and limit the voltage to ground during the fast power abort:
4 circuits per PS
54 magnets per circuit

17. Application 6: future accelerator magnets
Hot-spot 300 K, Vgnd 800 V
Hot-spot 280 K, Vgnd 600 V

18. Future application 5 + 6 QPS Circuit model Lfilt CCLIQ M1 M2 M27 CfiltMn PC
REE
Rfilt M
M54
M53
M28 L1
ΔU1 R1 L2
ΔU2 R2
φ, R
2D Electro-thermal Field model I

19. Conclusion
Present circuit models were successfully employed for various applications
For future applications, we are still looking for the quadrature of the triangle
FE models
Magnet measurement
Circuit measurements