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Safe Injection into the LHC V.Kain AB/CO

Safe Injection into the LHC V.Kain AB/CO. Contents and scope The need for machine protection at injection Interlocking – hardware and software Passive protection systems – collimators Protection level simulation results Commissioning aspects Conclusions.

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Safe Injection into the LHC V.Kain AB/CO

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  1. Safe Injection into the LHCV.Kain AB/CO • Contents and scope • The need for machine protection at injection • Interlocking – hardware and software • Passive protection systems – collimators • Protection level simulation results • Commissioning aspects • Conclusions Input from B. Goddard, M. Lamont, J. Wenninger, H. Burkhardt Verena Kain, AB-CO

  2. Machine Protection at Injection • 2.4MJ in 450 GeV injected beam • Damage limit around 100 J/cc ~2x1012p+, ~5 % of injected batch • 7.5s LHC aperture at 450GeV • Tight aperture in transfer line (MSI ~7s) Holes in Cu : 450 GeV LHC p+ beam (from 2004 TT40 materials test) 8x1012p+= ¼ of full batch 5.3x1012p+= 1/6 of full batch Inside, damage visible over ~1m (melted steel) Verena Kain, AB-CO

  3. What can go wrong: magnet trips, kicker flashovers, wrong settings… • Magnet trips can move trajectory by many s in short time (MSE: 40s in 1ms) • Kicker erratics, missings, timing etc. • Operator error • Corrupted settings Slow failures: • 10s in > 2-3ms: relying on interlocking Fast failures: • 10s in < 2-3ms: interlocking + collimators Ultra-fast failures: • 10s in few ms: collimators Verena Kain, AB-CO

  4. Machine Protection Strategy • Avoidance: • Procedures to avoid dangerous situations • e.g. never inject intensity above damage level into empty LHC (beam presence condition) • Protection systems: • Active: surveillance + interlocks to inhibit injection • Software – typical reaction time: ~seconds • Hardwired – typical reaction time: • normal power converter surveillance (PCS): ≥2-3ms • (possible) fast current decay monitors (FCDM): ~ 1ms • Passive: collimators for fast and ultra-fast faults • Collimators must be robust enough to withstand full injected batch → low Z material (C, hBN). Verena Kain, AB-CO

  5. Beam Presence condition • Injection of beam above damage level only possible if beam already circulating in LHC (beam presence) • Hardwired interlock ! • SPS and LHC intensity must be monitored reliably • Reliability and availability – 2 independent BCTs per machine/ring? Protects against many of the failures in the LHC (trips, settings, …) Verena Kain, AB-CO

  6. Hardwired Interlocks LHC energy LHC intensity SPS intensity SPS beam SPS HW Extraction HW bumped BP MSE current, girder MKE bumper currents Settings Transfer line HW Fast beam losses LHC beam permit LHC Settings LHC HW Injection HW BTV screens Transfer line collimators SPS Beam Interlock Controller LHC Beam Interlock Controller + SLP TDI position TED position Injection permit Extraction permit Movable TED beam dumps (stoppers) +TBSE beam SPS extraction kicker LHC injection kicker TDI injection stopper + TCDD Timing Timing SPS Transfer Line LHC Power Convertor Surveillance (PCS) and Fast Current Decay Monitoring (FCDM) are critical parts of the HW interlock system ! Verena Kain, AB-CO

  7. Software interlocks • Software interlocks • Mostly used for less critical parameters and for redundancy: • beam quality, trajectory and losses in transfer line, etc. • Much slower than hardware interlocks, not failsafe… • Local reference values in front-ends for equipment surveillance compared with central reference values • Reference values are machine mode dependent Verena Kain, AB-CO

  8. Passive Protection for fast and ultra-fast failures • Protection of LHC aperture and MSI aperture: • TCDI collimatorsfor failures upstream of injection regions • “generic” protection system with full phase coverage • Dedicated collimators for kicker failures: • MKI (LHC) failure: TDI + TCLI are 90° downstream • MKE (SPS) failure: TPSG is 90° downstream • No dedicated collimators for septum failures • Protection from MSE and MSI failures  interlocking Verena Kain, AB-CO

  9. TCDI Transfer Line Collimators • Close to LHC and MSI (last 300m matching section of TLs) • Robust, based on TCS design (1.2m C jaw) • FLUKA model of 300m of TI 8 local shield for each TCDI • 3 collimators / plane (0-60-120°) • Setting: 4.5s, tolerances: ≤1.4 s • 2 motors/ jaw (angular control) • Protection level 6.9 s (simulated with Monte-Carlo including all imperfections: b beat, mismatch from SPS, tolerances…) 0-60-120 degree collimators x’ 6s x 120o 60o amax 6.9 s LHC aperture to protect at 7.5 s Verena Kain, AB-CO

  10. TDI – TCDD - TCLI • Protects LHC (especially D1) against MKI failures • 90° downstream of the MKI. ~4m long hBN jaws • local protection of D1 with mask -> TCDD (1m, Cu) • Auxiliary collimators TCLIs to complete system • For MKI-TDI phase advance ≠90°, and for flexibility (halo load…) • At nx180°±20° from TDI (1.2m long C jaws) • 1-2 years after LHC start-up MKI Verena Kain, AB-CO

  11. Kicker MKI LEFT OF IP2 TCDD TDI MKI +90˚ RIGHT OF IP2 TCLIM TCLIA TDI +200˚ TCLIB TDI +340˚ TDI – TCDD - TCLI TCT design, half jaw, low Z two beams in one pipe TCS design, beams in separate pipes Verena Kain, AB-CO

  12. Protection level simulations Safe LHC injection  losses on aperture below 5% damage limit during injection • Extensive tracking simulations to check performance • MKI flashover scanned with TDI, TCLI setting • Full Monte Carlo of single failures at injection • All magnet and kicker families (SPS extraction, Transfer Line, LHC injection) for LSS4 - TI 8 – IR8 • Full TL + LHC injection region aperture model • All imperfections and errors included Verena Kain, AB-CO

  13. N/N0 of particles with amplitudes >7.5 sy MKI flashover simulations • TDI, TCLI setting of 6.8s, to guarantee max. 5% above 7.5s • Increasing opening increases risk of damage Verena Kain, AB-CO

  14. Single failure tracking Monte Carlo results (1000 runs per failure) • PCS = standard Power Convertor Surveillance (≥3ms) • FCDM = Fast Current Decay Monitor (~1ms), dedicated new system Verena Kain, AB-CO

  15. Discussion of results • LHC protection looks OK, provided FCDM for MSI • Detect and react to 0.3% change in 2.5ms • TL needs FCDM for MSE septum (reduce risk window), MBI and MBHC • MKE and MSE faults can still cause damage to the TL… possible solutions being studied • All other single failures are covered for TL & LHC • TCDI system gives full protection from upstream failures • Failures at end of line: slow enough for PCS and FCDM • More complicated scenarios not yet studied • Grouped powering failures: e.g. general power cut • Combined failures • Fault of machine protection system + other failure • e.g. wrong setting of passive absorber + trip of magnet family Verena Kain, AB-CO

  16. Commissioning aspects • Limited role of protection systems for early stage of LHC commissioning. (SPS extraction, SPS safe beam, TI 8 interlocks and LHC injection BIC needed !) • Injection protection must be fully operational for injected intensity above damage level ≈ 15 bunches • Many parts can be commissioned without beam: • LHC injection BIC + matrices + data exchange; collimator movements + interlocks; FCDM, PCS, logging, software, failsafe behavior, etc. etc. • Beam is essential for commissioning of: • SPS & LHC safe beam and beam presence (BCTs) • TDI/TCLI/TCDI jaw alignment • Tests of full interlock system (EMC, …) Verena Kain, AB-CO

  17. Commissioning of TCDI system • Setting up collimators: • 1) finding beam axis • 2) align jaws with beam envelope • 3) set jaws to required gap • Setting up with beam: Transmission Measurement • Angular jaw alignment • Beam size measurement • Use BCTs in SPS and downstream of TCDI (in LHC injection region - not in layout yet) • Move TCDI jaws through beam, measuring transmission… • Required beam intensity ~1010 depending on BCT resolution • Impact on LHC: ”inject – TDI dump” or “inject and dump” mode

  18. TCDI setting up with beam - tests First Results of transmission measurement for TCDI (TCS) setting up. Measured transmission vs. angular misalignment – looks promising Simulated data Methods tested in simulation with realistic parameters and tolerances Attainable accuracy can be predicted – expect able to align to ~100mrad. Simulated transmission vs. angular misalignment: Verena Kain, AB-CO

  19. Commissioning of TDI /TCLI • Setting up TDI and TCLI with beam • Beam axis measurement : circulating pilot • Transmission Measurement for jaw alignment • similar to TCDI • inject-dump required, intensity depending on BCT resolution (max. ~1010) • Beam size measurement : circulating pilot (max. ~1010) • jaw moved through beam • reconstitute transverse beam profile from surviving beam intensity vs. position Verena Kain, AB-CO

  20. Conclusions • Injection protection • has to ensure only “safe” beam is injected into LHC during commissioning • is absolutely mandatory if injected intensities exceed 2 1012 p+ • LHC protected against many failures by “beam presence” condition • Comprehensive tracking simulations extensively used to define protection systems and to determine protection levels • LHC fully protected with foreseen active and passive protection • Require Fast Current Decay Monitor to measure 0.3% DI in 2.5ms • Hardware and software interlocking is being specified → InjWG • At present the protection systems cannot fully exclude TL damage • Simulations will be extended to grouped and combined failures • Commissioning of the injection protection system is being prepared • Methods for setting up protection collimators being worked out Verena Kain, AB-CO

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