STEAM Applications Part I The circuit point of view 4th STEAM Collaboration Meeting, Darmstadt, 21-22 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

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

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

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

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

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)

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

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

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

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

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 (300-600 A). Good agreement: the observed QPS signals are compatible with the theory of an inter-turn short. Courtesy of M. Maciejewski

B. Magnet measurements Some applications indicate the need for more refined circuit models Measurement conditions: Current: 0 A ± 1 A rms Temperature: 300 K - 1.9 K From “Opportunities in High Magnetic Field Science”, 2005

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

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)

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

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

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

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

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