MPE actions: update Third LHC Splice Review, November 12-14, 2012 Rüdiger Schmidt, TE-MPE reporting for ….. Circuit Documentation: S.Pemberton, K.Pereira Splice Resistance Measurements on DFBXs: R.Mompo, G.d’Angelo, M.Bednarek Circuit Modelling: A.Verweij, B.Auchmann, Z.Charifoulline, D.Molnar, D.E.Rasmussen, E.Ravaioli, H.Riihimaki S.Rowan, + many others 1

MPE actions from last review and circuits screening Second LHC Splice Review, November 28-30, 2011 Rüdiger Schmidt, TE-MPE reporting for ….. R.Mompo, G.d’Angelo, M.Bednarek, N.Catalan-Lasheras A.Verweij, E.Ravaioli, S.Rowan, D.Molnar K.Dahlerup-Petersen, M.Zerlauth S.Pemberton, K.Pereira A.Ballarino, H.Thiesen, A.Siemko + others

2011: Overview Magnets Electrical Circuits Screening 1.Information on magnet and powering system 2.Electrical and thermodynamic modelling of the magnets / circuits 3.HV testing – K.Dahlerup-Petersen 4.Issues related to cold diodes – F.Savary 5.Related to CSCM - Wednesday 6.Others 7.Not discussed 3 NrCircuitsShort descriptionMain Responsible 1AllInformation libraryMPE 2AllElectrical integration drawingsMPE 3AllPeak DC voltage checkMPE 4All E-model (e.g. PSPICE), transient voltage, effects of faultsMPE 5AllHot spot temperatureMPE 6AllGround insulation current monitorEPC 7AllPeriodic automatic test of insulationMPE 8AllProtection resistors for V tapsMPE / MSC 9AllIn-situ test plan for circuits not tested to full loadMPE 10AllTest simultaneously main and corrector circuitsMPE 11RBDiodes: qualify design or engineer repair solutionMPE / MSC 12RB/RQInternal voids in T connection to diodesMPE 13RB/RQImprove spider insulationMSC 14RB/RQConsolidate main splicesMSC 15RQDiodes: qualify design or engineer better solution 16 17ITDefine repair planMSC 18ITTest & document splicesMPE 196kAQuench studiesMPE 20Cur LeadsRedundant temperature sensors in safety chainCRG / MPE 21Cur LeadsTop temperature sensors in safety chainCRG / MPE 22Cur LeadsRisk of electrical breakdown due to He leaksMSC 23DFBRepair 13kA splices or prove them healthyMSC / MPE 24DFBBB deflection studiesMSC

Stephen Pemberton TE-MPE-EE 4 LHC Electrical Drawings: Status S.Pemberton

Stephen Pemberton TE-MPE-EE 5 Status  All 8 sectors were graphically complete by the end of  Each sector has been internally verified against all our gathered data (EDMS Drawings, Procedures, etc) and the XML circuit definition from the Layout Database.  This labor intensive process lasted many months but now enables us to be confident in the accuracy of the drawings.  All individual cell drawings have been exported into DWFx format then uploaded onto the Electrical Drawings Navigator. This allows people to view and manipulate the drawings without having to install AutoCAD on their PC.  Due to recent changes in the AutoCad plug-in: new users are experiencing difficulties viewing the drawings, currently being addressed.  Potential users should become aware of the availability of the drawings and user instructions will be provided.  There should be a period of general use by different groups to establish any underlying problems concerning the usability of the navigator.  We would value any feedback as to the legibility of the drawings and would eventually be happy to perform any upgrades.

Stephen Pemberton TE-MPE-EE 6 Drawings for electrical circuits (S.Pemberton & K.Pereira)  Future work and comments –Adding of QPS signals: would make the drawing unreadable, better to include information on separate drawings –Non – conformities: still to be added after starting to use the drawings –Also required for addressing quench propagation: variation of cooling conditions due to different insulation (number of layers of insulation), helium conditions (liquid at 1.9K or 4.3K, gaseous) – to be defined how to do it

Stephen Pemberton TE-MPE-EE 7 Navigator Screen Shots

TE/MPE-MS 10/05/2012, Richard Mompo 8 Splice Resistance Measurements on DFBXs

There are eight DFBXs in the LHC. Four have an additional D1 magnet connected. Two measuring set-up were prepared in order to measure two DFBXs at a time. Measurements took place at the end of the Xmas break during the powering phase. Circuits RQX/RTQX2 were powered together with a Mexican pyramid. Use of standard power cycle “PNO.D11” with 3 current plateaus reduced to 10 min. each (instead of 1h). D1 magnets were measured separately using of standard cycle power “PNO.c2” Overview

DFBX Layout in LHC During PNO.D11, RTQX1 power converter is OFF.

11 Q2 is seeing 9700 Amps! Cycle with voltage measurements

Number of splices in DFBX 12

13 D1 splices belong to another family and should be compared to other IPDs

TE/MPE-MS 10/05/2012, Richard Mompo 14 assuming that all splices are identical! DVM3 and DVM7 of DFBXB.R1 are slightly outside of the Gaussian curve

Conclusions All eight DFBXs during were measured during the Xmas break. Q1, Q2a, Q2b and Q3 internal splices (splices between poles) were not measured Nominal resistance value for the two groups of splices: –Around 0.5 E-09 Ohms for Q1, Q2 and Q3 splices –Around 1 E-09 Ohms for D1 splices (comparable with other IPDs magnets) An internal note similar to the one written for IPDs and IPQs is (

Circuit modeling SoftwareUsed forDescription QP3Conductor In-house Fortran code, especially developed for electro-thermal calculations of 1D conductors with helium cooling. RoxieMagnet In-house Fortran code, especially developed for field optimization of accelerator magnets. PSpiceCircuit Commercial software for the electrical modeling of entire circuits. COMSOL Specific parts Commercial multiphysics modeling and engineering simulation software. We mainly use the following simulation software: Arjan Verweij

Performed simulations/studies using QP3 Type of simulationCircuit / magnet Hot spot calculations600 A bus, 600 A magnet, 6 kA bus BLM threshold study6 kA MQM, MBRB, MB, MQ, MQTLH QPS threshold study6 kA MQM & bus Quench propagation studyRB & RQ magnet, RB and RQ bus, 13 kA pigtail Bus protection for defective jointsRB & RQ bus Simulation of the 2008 accidentRB bus Temperature increase in the interlayer spliceMB Safe current in case of a defective interpole joint MB Safe current for a defective bus joint in LHe and GHe. Joint with and without shunt. RB and RQ, incl. magnet, bus and diode Simulation of experimental tests on jointsSeveral tests in FRESCA, Q8-Q9 test in SM18 CSCM for 4-5 TeV and & TeV validation, for various types of current cycles RB and RQ Arjan Verweij

Roxie Code for the electromagnetic simulation and optimization of accelerator magnets  Field maps, field errors, AC losses, magnetization. Models available for all LHC magnets.  2D and 3D quench simulation with discretization of a few cm. Possibility for heater firing, beam losses, cooling, and quench back. Models available and validated for MB and MQ. Quench models for a few other magnets will be made soon.  Output often used as input in QP3 / PSpice / Comsol. Arjan Verweij

PSpice Electrical modeling of entire circuits, including PC, leads, ground, magnets, switches, etc. - Circuits with thousands of elements are simulated rather quickly. - Effective thermal modeling is included (e.g. resistive built-up of a quenching magnet) but needs input from other programs. Possibility to discretize a magnet in several parts. - RB, RQ, RQX, RD2, RQ4, RQ10, RQS, RQTL, RQTD/F, RCBY models are done. For each model, the simulations of a Fast Power Abort and a quench (training and/or heater induced) are compared to experimental data from the machine. - Any other circuit can be quickly modeled if needed, starting from one of the existing models Arjan Verweij

CircuitSpecial studies / Failure cases RB Effect of delay in switch opening. Effect of snubber capacitor (including short-to-ground). Effect of PC configuration (additional resistor, inversion of crowbar and filter in PC). Effect of earthing point position. Effect of AC behaviour of magnet. Effect of unbalanced apertures on the QPS detection. Simulation of AUG event of 14/5/2011. Short circuit to ground. RQX Short circuit to ground. Non-opening of a thyristor. Opening of FWD during ramp down. RQ4 Short circuit to ground. Non-firing of quench heater. Inter-turn short. RQTD/FQuench-back. Lack of parallel resistance. Decrease of the EE resistance. RCBYHInter-turn short. CSCM Effect of spread in diode opening voltage. Effect of the use of 0, 1, or 2 EE's. Non-opening of a by-pass diode. PSpice Arjan Verweij

COMSOL Multiphysics modeling and engineering simulation software  Thermo-electrical modeling of specific parts of circuits requiring 3- D approach, such as shunts on 13 kA joints, bolted ‘half-moon’ connection to diode, ‘praying hands’ 6 kA joints, current leads, etc.  Model of the 13 kA joint is ready (RB & RQ, shunted & non- shunted). EDMS report under approval.  Model of the dipole and quad diode is ready including the diode leads and contacts. Model is partially validated using SM18 measurements. Cooling to LHe and GHe is included.  Model of a HTS ‘sandwich’ is under development.  If needed, a realistic model of the 6 kA and/or 13 kA current leads can be made. Arjan Verweij

Conclusion  During the last year we have largely increased our expertise of thermo-electrical modeling of (parts of) the LHC circuits.  One of the Roxie experts has joined our section, so that we now have experts for the conductor, magnet, and circuit modeling.  The COMSOL models have been transferred last year from a technical student to a staff member (and another technical student), so as to guarantee long term know-how in this field.  We will focus next year on having validated quench models of most types of magnet, and incorporation of effective quench models in the circuit models. This is important to be prepared for the larger number of (normal and beam- induced) quenches expected after LS1. Arjan Verweij

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