LHC circuit modeling Goal: Create a library of electrical models and results for each circuit Useful and usable for the next 20 years…… Web site cern.ch/LHC-CM

Our tools: PSpice Comsol QP3

LHC circuit modeling, using PSpice Describe and understand the electrical behaviour of a circuit, during ramp, plateau, fast discharge, and quench. Observe/detect anomalous behavior of a circuit in the machine, and understand the reason for this anomalous behavior. Improve the functioning of a circuit (if needed) Understand the coupling between circuits “What if …” simulations (for example: simulations of a short between bus and ground, or between two circuits)

TypeCircuitNr of circuits I_maxConverterMagnetNr of magnets RB RPTEMB154 RQ RQD RQF RPHEMQ47 / 51 RQX RPHFC+RPHGC+ RPMBC 2xMQXA+ 2xMQXB 4 IPD RD RPHFMBX1 RD RPHGBMBRC1 RD RPHFDMBRS2 RD RPHFDMBRB1 ! ! W W W Circuit is “in work” ! Circuit has high priority

TypeCircuitNr of circuits I_maxConverterMagnetNr of magnets IPQ RQ xRPHHMQY2 RQ xRPHGBMQML2 RQ xRPHGBMQML2 RQ xRPHGB2xMQM+2xMQML4 RQ xRPHGAMQM4 RQ xRPHGAMQML2 RQ xRPHGA2xMQM+2xMQMC4 RQ xRPHGAMQML2 ! ! W

TypeCircuit# of c.I_maxConverterMagnet# of m.EE 600 A RCD RPMBBMCD76 / 77EE RCS RPMBBMCS153 / 154EE ROD & ROF RPMBBMO8 / 11 / 13EE RQ6 8490RPMBBMQTLH6EE RQS 17600RPMBAMQS2No EE RQS 7600RPMBAMQS4EE RQT64600RPMBAMQT1No EE RQTD and RQTF32600RPMBBMQT8EE RQTL64600RPMBAMQTLI1EE RSD and RSF RPMBBMS9 / 10 / 11 / 12EE RSS15600RPMBBMSS4EE RCBXH24600RPMBBMCBXH1No EE RCBXV24600RPMBBMCBXV1No EE RQSX38600RPMBBMQSX1No EE RU2500RPMBBMU1EE ! )) W ! ! !

TypeCircuit# of c.I_maxConverterMagnet# of m A RCO 16110RPLBMCO77 RCBCH / 86RPLBMCBCH1 RCBCV / 86RPLBMCBCV1 RCOSX3 8110RPLBMCOSX1 RCOX3 8110RPLBMCOX1 RCSSX3 8110RPLBMCSSX1 RCSX38110RPLBMCSX1 RCTX38110RPLBMCTX1 RCBYH3877RPLBMCBYH1 RCBYV 3877RPLBMCBYV1 60 A RCBH 3761RPLAMCBH1 RCBV 3761RPLAMCBV1 )) )) )) W

Step 1: General model including current leads, power supplies (incl. crowbars, thyristors, …), ground connections, Energy Extraction (switch and dump). The magnet is modeled by a simple inductance and R=0 (with R par if present). Step 2a: If needed, replace L magnet by a more realistic L-R-C circuit based on spectrum analysis, or based on PM data from the machine. This is definitely needed for the MB’s and MQ’s with probably a current dependent L-R-C. Step 2b: Include the R(I,t) for a quenching magnet. Step 3: Validate the model as much as possible, using PM data from the machine, and data from B4, SM-18 etc. (Step 4): Combine models for mutual interaction.

Resources and Priorities for PSpice work in 2011 Manuel Dominguez Emmanuele Ravaioli Evangelina Antonopoulou Ongoing: RCBY circuit including R-L-C model of MCBY, and tests in spare magnets R-L-C model of MB and MQ at various currents (0-12 kA) RB circuit (emphasis on unbalanced aperture voltages, new snubbers, switch opening, frequency of converter ringing, R-L-C model of MB) Finalise RQ and RQ4 circuits RQS circuit 1 st priority other circuits: IT, RD2, RQ6 or RQ9, one 600 A circuit with high L and EE

Thermo-electrodynamic calculations, using Comsol and QP3 Quench behaviour (‘Hot spot’, propagation, …) Detailed stability analysis of joints and other circuit singularities Analysis of the future 13 kA shunt (for RB and RQ) Set/adapt QPS threshold values Set/ adapt BLM quench thresholds, and analyse beam-induced quenches

For each circuit at various currents (using QP3): T hot for quench starting in bus (with and without cooling). T hot for quench starting in magnet (adiabatic, peak field and average field, without inter-turn propagation). T hot and R(t) for quench starting in magnet (most realistic case for ‘critical’ circuits, possibly using Roxie). Typical propagation dV/dt at start of quench for different parts of the circuit. On request from Splices Task Force or others (using QP3, Comsol): Detailed analysis of singularities, e.g.: a badly cooled bus segment in-between 2 well-cooled segments. excessive joint resistance in a bus internal splice resistance in a coil defective 13 kA joint

Example of a singularity: plug 1.9 K 4.5 K Conductor 1: - cross-section - Cu/SC - RRR - insulation Conductor 2: - cross-section - Cu/SC - RRR - insulation L1L1 L3L3 L2L2 R splice Insulation

Ongoing Comsol work Daniel Molnar 3D models of non-shunted and shunted 13 kA RB and RQ joints (incl. different types of shunt, effect of non-uniform soldering, and setting of QC criteria). Mutual validation of Comsol and QP3. (Possible test in SM18 on adiabatic shunted RB joint) Ongoing QP3 work Arjan Quench propagation test in S56 during technical stop next week, and possibly others CSCM (aka ‘Thermal amplifier’) Adaptation the QPS threshold on the RQTD/F circuits BLM quench thresholds (to be partially transferred to BE-BI) Analysis of ‘wire scanner’ induced quenches. Manual + updates of the code

Foreseen library contents for each circuit:  Electrical description of the circuit, and the PSpice model (including converter, EE, QPS signals, earth connection, current leads, etc).  Description of the conductors in the bus and magnet (including insulation, splice configuration etc)  Response to a Fast Power Abort (during ramp and plateau, in some cases with quench back)  Response to a quench  Field map of a magnet (input from MSC group)  Simulated V(t) at start of a quench in bus and magnet for various currents  Simulated hot spot temperatures in bus, joint and magnet for various currents and conditions (adiabatic, 1.9/4.5 K, etc). For the moment not foreseen to include the current leads Priorities and resources of PSpice, Comsol and QP3 work may change due to issues coming up during machine operation