1. TE-MPE-CP, RD, 09-June-2011 1 Enhanced Diagnostics & Supervision for Quench Heater Circuits R. Denz TE-MPE-CP

2. TE-MPE-CP, RD, 09-June-2011 2 Outline  Introduction  Quench Heater Discharge Power Supply exploitation  Enhanced quench heater diagnostics  System integration  Cost estimate and timeline  Hardware – status of development  Vincent’s talk

3. TE-MPE-CP, RD, 09-June-2011 3 Introduction  6076 quench heater circuits in LHC used for active magnet protection –4928 x MB, 784 x MQ, 364 x IPQ, IPD, IT –Quench heater power supply type DQHDS performance in principal good but spoiled to a certain extent by one faulty component (see next slide)  At present the quench heater circuits are hardly used and stressed but this will change significantly once LHC increases energy –Magnet training campaigns, more beam induced quenches  In most cases the loss of a quench heater circuit would be acceptable but there is a risk of serious (non acceptable) collateral damage, i.e. a short to coil, which could require an exchange of a magnet –QPS supervision should indicate a potential failure of a quench heater circuit  Enhanced diagnostics must be properly integrated into existing system –Sufficient resources must be provided (material cost + manpower)

4. TE-MPE-CP, RD, 09-June-2011 4 Quench Heater Discharge Power Supply (DQHDS) exploitation  Failure rate of DQHDS basically determined by one component, the infamous main switch –Material analysis performed by CERN specialists confirmed wrong ratio of components (overshoot of hardener) in a moulded plastic part –Replacement campaign launched in 2010 (~1600 / 6076 switches so far exchanged) –Additional software interlock to take into account quench heater redundancy of the MB protection QPS_OK flag to be corrected accordingly (deployment started ~20% done together within radiation upgrade) –MTBF currently ~ 1 Mh (1.16 Mh in 2010) MTBF_MQ > 4 Mh (all updated, no faults so far), MTBF_MB ~ 0.8 Mh  Discharge tests during QPS-IST at lower energy –Successfully tested (U_HDS ~ 100 V) with IPQs during winter shutdown –Software application for fully automatic execution and analysis still to be developed

5. TE-MPE-CP, RD, 09-June-2011 5 Enhanced quench heater diagnostics - motivation  Increase diagnostic capabilities for qualification and possible fault detection of the LHC main dipole quench heater circuits –Present system monitors quench heater voltage – sufficient for healthy heater circuits and DQHDS integrity check –Some dipole magnets are equipped with quench heaters which may show problems during LHC exploitation –Magnet expert wish list: Monitor discharge current Check electrical continuity of quench heater after discharge Check quench heater sanity (if possible) Check for eventual earth faults Perform discharge tests with lower energy  see exploitation –Extension to other magnet types, e.g. MQ? This needs to be clarified quickly as system integration is quite different for MB, MQ, IT, IPQ and IPD

6. TE-MPE-CP, RD, 09-June-2011 6 Enhanced quench heater diagnostics - constraints  Significant but successful effort from 2009 through 2011 to stabilize QPS –System is now working correctly and reliable –Any modification must minimize impact on existing systems At this level it is by far easier to get it wrong than to get it right  Modification of existing electronics, i.e. Local Protection Unit and Quench Heater Discharge Power Supplies, not wishful: –Potentially radioactive material  special workshop etc. –High risk of collateral damage –ALARA principle  LS01 2013/2014 is one of the few occasions to perform this upgrade –Major work in the LHC tunnel due to splice consolidation Collateral damage expected Extensive re-testing of equipment required in any case

7. TE-MPE-CP, RD, 09-June-2011 7 Enhanced quench heater diagnostics – possible upgrades

8. TE-MPE-CP, RD, 09-June-2011 8 Enhanced quench heater diagnostics – feasibility studies I  Monitoring of discharge voltage and current –Feasible if installed as separate new data acquisition system Data acquisition at significantly higher sample rates (~20 kHz) Current measurement by dedicated tailor-made current transformer –Affordable resolution is one per mil  100 mA –Two different technical solutions elaborated Microcontroller based (integrated 12 Bit ADC) –12 Bit  25 mA / 250 mV resolution FPGA based with external 16 Bit ADC Both solutions have already been tested for radiation tolerance in previous projects –Only useful if combined with powerful analysis software –Implicates as well a change of the QPS supervision 3 PM data blocks instead of one: the selected board, the other board, heater supervision

9. TE-MPE-CP, RD, 09-June-2011 9 Enhanced quench heater diagnostics – feasibility studies II  Electrical continuity and heater sanity –Old almost discarded approach of DC resistance measurements has been re-evaluated recently Measurements performed by Joaquim Mourao R0 = 4.907 mΩ ΔR = 1.782 mΩ w0 = 15 mm Δw = 14.7 mm

10. TE-MPE-CP, RD, 09-June-2011 10 Enhanced quench heater diagnostics – feasibility studies II  Test results indicate that an ohmmeter with ~100 µΩ resolution should be able to detect the onset of a potential rupture of the quench heater strip –Bipolar measurements required in order to compensate thermals –I = ± 100 mA  U = ± 1.2 V (R Heater ~ 12 Ω)  Measurement system must only be used with unpowered magnets –Radiation tolerance not required as system can be switched off during operation with beam –One system per protection system sufficient Also wishful in order to compare better the different heater circuits of a magnet –Design of such a system seems to be feasible at “moderate” cost (but not for free!) –Type testing of hardware ongoing  more news from Vincent

11. TE-MPE-CP, RD, 09-June-2011 11 System integration I  System integration will strongly depend on the magnet type –MB, MQ systems are different –IT, IPQ and IPD systems similar but quite different from the other two Very long cables  difficult for resistance measurement  All new systems must communicate with QPS supervision through the DAQ systems of the magnet protection –Local communication bus to be extended  new measurement electronics has to be integrated into a new protection crate For MB (1232) and MQ (392) new crates are required –Power supplies and quench detectors can be re-used –Fieldbus coupler (DQAMC) must be able to address 6 clients –Present controller used for MB and MQ can only address 4 clients  new fieldbus couplers for MQ required IT, IPD and IPQ: integration into old crates feasible –Should be done within nQPS upgrade of these systems

12. TE-MPE-CP, RD, 09-June-2011 12 System integration II  Electrical distribution boxes for racks type DYPB and DYPQ (“Crawford boxes”) to be modified as well –Necessary manipulations to be indentified and to be checked with RP whether this work can be performed on systems currently installed in the tunnel (see Vincent’s presentation) –Purchase of new boxes is most probably not significantly more expansive than the modification of the old boxes  QPS fieldbus network in the tunnel should be reconfigured in order to increase the maximum data transmission rate –Current network is loaded already up to 90% –To be done anyhow for the exploitation of the NanoFip boards  QPS supervision to be upgraded as well –New signals to be defined etc. (straight forward but tedious...) –Post mortem data transmission to be modified  QPS-IST for main circuits to be revised and extended

13. TE-MPE-CP, RD, 09-June-2011 13 Cost estimate & timeline  Table shows a first price estimate (hardware only) for the update of MB and MQ protection systems –Manpower not yet included but significant (also a lot of “donkey work”)  Time constraints –Specification and R&D phase to be completed in 2011 –Type testing early 2012 (including tests in LHC) –Purchasing procedures to be launched as well early 2012 (potential bottleneck, especially for orders > 200 kCHF) –Production 2 nd half 2012, 2013 –Test & installation during LS01 2013/2014