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Session 4: Chairman: S. Russenschuck, Scientific Secretary: R. Jones Other Issues affecting Beam Commissioning (I) Electrical Quality Assurance (Davide Bozzini) Report from the Magnet Polarity Coordinator (Stephan Russenschuck) Quench Protection System (Reiner Denz) Consequences of RF System Failures during LHC Beam Commissioning Stephan Russenschuck, CERN-AT-MEL (Trevor Linnecar) Initial Commissioning of Critical Beam Instrumentation Systems (Eva Barbara Holzer) The Estimation of Individual and Collective Intervention Doses for the LHC Beam Cleaning Insertions (Markus Brugger) The LHC Access System: Why do we put Doors (Luigi Scibile) 1 ELQA (1) Accessibility PS machine “warm”. Electrical circuits are easily accessible and visible Stephan Russenschuck, CERN-AT-MEL For diagnostics almost all senses can be used: hearing , visual, smell, touch LHC machine “cold” electrical circuits will not be directly accessible This picture shows the String 2 phase 1, i.e. 54 meters without access to the circuits. Diagnostic has been a nice exercise. LHC machine will be 2700 m! Diagnostic may require the local access to the circuit (opening of interconnections). 2 ELQA (2) Classification of the electrical faults Stephan Russenschuck, CERN-AT-MEL The notorious one’s Fault Consequence Detection Diagnostic method Inverted polarity of a magnet within a series (ex: MCS) Beam quality - BPM’s - Beam observations - Polarity check Open circuit of a main circuit Beam abort - QPS - Power converter - Continuity check - Transfer function Short to ground of a main circuit Beam abort - Power converter - High voltage test - Transfer function Loss of instrumentation used for magnet protection Beam abort - QPS - Continuity check - TDR …………….. ………………. …………………… ………………… The malicious one’s Fault Consequence Detection Diagnostic method Quench of bus bar segments or splices Beam abort - QPS ? Transitory shorts to ground or between circuits Beam abort - Power converters ? High ohmic resistance of bus bar interconnect ? - QPS - Cryo system ………………… 3 ELQA (3) Staff experience and resources Fundamental experience will be acquired during machine assembly and hardware commissioning Beam commissioning starts in 2007 most of the knowledge will be gone Success of ELQA activities during beam commissioning need experienced and well trained personnel 18 Beam commissioning and operation HNINP collaboration 16 Nr. of person Stephan Russenschuck, CERN-AT-MEL Interventions during beam commissioning and operation will have to deal with radiation Staff shall be familiar not only with the ELQA procedures but also with safety rules and tunnel environment Hardware commissioning Assembly FSU 14 Tech. Students 12 Staff 10 8 6 Sector test would be helpful for ELQA optimization 4 2 0 Q1 2005 Q2 2005 Q3 2005 Q4 2005 Q1 2006 Q2 2006 Q3 2006 Time Q4 2006 Q1 2007 Q2 2007 Q3 2007 Q4 2007 4 Progress Report of the Magnet Polarity Coordinator Share with me The confusion about the Magnet Polarity Conventions. The doubts about the Polarity of the Main Quadrupole. Stephan Russenschuck, CERN-AT-MEL The worries about the continuity of the Spool-piece Busbars. The passion for the following question: 9:00 or 3:00? 5 Stephan Russenschuck, CERN-AT-MEL LHC Magnet Polarities EDMS: 90042 6 Polarity (3) Conversion Table: Dipoles (and B3, B5, ..) MAD H Kicker V Kicker B1 B1 A1 A1 (B0n) (B0n) tilt (B0s) (B0s) tilt Clockwise Deflecting Clockwise out up in down up in EDMS Negative Negative Positive Positive Negative Positive 90042 dipole skew dipole skew skew dipole dipole A1 -A1 Stephan Russenschuck, CERN-AT-MEL Beam 1 (Polarity) Meas. dipole - B1 -A1 B1 dipole B1 Mag. Frame 7 Stephan Russenschuck, CERN-AT-MEL Polarity (4) Concern: Spool-piece Busbar Routing 8 Stephan Russenschuck, CERN-AT-MEL Polarity (5) Spool-piece Busbar Routing in the SSS 9 Stephan Russenschuck, CERN-AT-MEL Polarity (6) Continuity Checker 10 Protection of LHC superconducting elements Protection of LHC superconducting elements, commonly referred as Quench Protection System (QPS) – Concerns all superconducting circuits with I ≥ 600 A • Main dipoles and quads • Main busbars Stephan Russenschuck, CERN-AT-MEL • HTS current leads • Insertion region magnets and busbars • Corrector magnets and busbars – Quench detection systems, quench heater power supplies, energy extraction systems & data acquisition systems – 170 tons of electronic, 3820 quench detection systems 11 QPS (2) Conclusions QPS system will be fully commissioned and available prior to beam commissioning QPS equipment is designed for high reliability and availability – QPS test mode, high resolution mode for leads and 13 kA busbars Triggers of the protection system normally stop LHC In a significant number of cases failures of the QPS system will cause a Stephan Russenschuck, CERN-AT-MEL stop of the LHC (a faulty trigger a day keeps the Higgs away) Interventions are time consuming but cannot be avoided The QPS data acquisition systems provide valuable information on the status of the LHC cold mass and possible failures inside Magnets close to the interaction point are well protected but should not be necessarily regarded as “beam loss monitors” 12 Consequences of RF system failures during LHC beam commissioning. T.Linnecar, O. Brunner, E. Ciapala, Stephan Russenschuck, CERN-AT-MEL E. Shaposhnikova, J. Tuckmantel, AB-RF Analysis: Loss of one or more 400 MHz cavities Issues: Hardware protection beam induced over-voltage 3 MV max power induced by beam in load 300 kW max. Effects on the beam transient effects – emittance blow-up, beam loss instability from cavity impedance reduced voltage for acceleration – beam stored lifetime 13 RF Failures and Consequences Beam present during trip – Beam should survive with a trip of 2 cavities up to ½ nominal beam current. – To do this, work at ½ de-tuning and lower Qext. (possible because power is available – Coupler and tuner must remain under control. Beam dump interlock should come from Vcas and Pload New injection Stephan Russenschuck, CERN-AT-MEL – Can inject and accelerate with up to 4 cavities off, up to ½ nominal beam current (with reduced luminosity) – Work at ½ de-tuning and lowest possible Qext. – Frequency stability of the passive cavity must be 0.75 kHz (He pressure 5 mbar). General – Beam dump interlock from Pload and Vcav (also He pressure for quenches), not from a trip. 14 Beam Instrumentation (1) BPM Polarity (still some errors possible) – Cryostat cabling (no mix-up, pre-formed cables) – Errors in front of the electronics are impossible to verify remotely after installation – will be seen with beam and can be visually inspected. – Errors after electronics are easier to track down (mixed up BPMs) and should be spotted during hardware commissioning as each station is turned on individually. – Same electronics and procedure had been used in TI8: • 3 planes of 51 gave problems (5%) Stephan Russenschuck, CERN-AT-MEL • 5% for LHC would imply 50 incorrect or broken planes per beam. Database Issues – Position of beam 1 and beam 2 (especially for turned cryo-magnet assemblies) – Calibration / linearization database errors • wrong BPM type wrong position readings • wrong linearization / calibration constants reduced accuracy 15 Beam Instrumentation (2) Sector Test BPM – Commissioning of BPMs in the sector (polarity checks, timing, database issues) and a part of the functionality of the BPM system. – Possibility to find problems and fix them before LHC start-up. BLM Stephan Russenschuck, CERN-AT-MEL – Commissioning of a part of the functionality of the BLM system (dump signal, setting of thresholds and beam flags, database issues, logging, post mortem, offline analysis). – Quench level calibration: Controlled beam loss in cold magnet equipped with several BLMs. – Longitudinal loss patterns (only way for measurements before LHC start-up). – Possibility to find problems and fix them before LHC start-up. – Could prove very useful considering the complexity of the system and the time needed to implement changes or fix problems. 16 Intervention Doses Individual and Collective Doses at IR7 Issues and goals – Strong activation of components due to high losses causing significant residual dose rates! – Time-consuming interventions can be expected for base-line layout. – Installation of Phase 2 collimators in highly radioactive area. – Optimization of the design to minimize individual and collective doses received by personnel during interventions and machine upgrades. Stephan Russenschuck, CERN-AT-MEL – Estimates of individual and collective dose are legally required (INB documents, external companies must be certified) Methods – Results on residual dose rates are available from detailed FLUKA Monte Carlo simulations (for IR7). – Intervention scenarios are needed from intervening groups (uncertainty in the interventions, not in the dose rates). 17 Stephan Russenschuck, CERN-AT-MEL Collimator Exchange – All Steps 18 Intervention Doses Individual and Collective Doses at IR7 Results – Significant individual and collective doses, exceeding those of so far received during SPS interventions. – Therefore, optimization of the design is of utmost importance for a fast collimator exchange. – Based on the results of the calculations first design modifications have already been implemented: Stephan Russenschuck, CERN-AT-MEL • fast connections for flanges (chain clamps instead of bolts) • optimization of the orientation of magnets (connections away from high loss points) – Further optimization will be necessary, e.g,: • remote bakeout system • remote alignment system • use of radiation-hard components/cables where possible • use of mock-ups for intervention planning • implementation of procedures 19 LHC Access Control System Goals: – Manage access right – Identify user – Verify authorization (training) – Automatic or remote access control Stephan Russenschuck, CERN-AT-MEL Status – Contract running – System engineering completed – Site acceptance of “LHC 0” June 2005 (operational prior to machine commissioning) 20 Stephan Russenschuck, CERN-AT-MEL LHC Access Safety System Goals: – Protect personnel during Beam operation – Allows Access operation when safety conditions are met • No radiation hazards (LHC beam, RF) – Distributed, highly reliable interlock system – Completely tested before Cold Checkout Status: – Specifications review EDMS 456549 (Access Safety Working Group) – HW and SW Architecture prototyping (Siemens Safety Matrix) – Contract for the system integration, installation and commissioning. – On going safety studies Special request to AB: – To finalize the list of equipment which needs to be interlocked with the access (RF test when during HW commissioning). 21