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Commissioning of BLM system

Commissioning of BLM system. L. Ponce With the contribution of C. Zamantzas, B. Dehning , E.B. Holzer, M. Sapiensky. Outlines. Overview of the system signal available in the CCC Strategies for the thresholds settings hardware commissioning commissioning with beam conclusions.

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Commissioning of BLM system

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  1. Commissioning of BLM system L. Ponce With the contribution of C. Zamantzas, B. Dehning, E.B. Holzer, M. Sapiensky

  2. Outlines • Overview of the system • signal available in the CCC • Strategies for the thresholds settings • hardware commissioning • commissioning with beam • conclusions

  3. BLM for machine protection • The only system to protect LHC from fast losses (between 0.4 and 10 ms) • The only system to prevent quench Arc Dipole Magnet BLM system damage protection, no redundancy Quench protection system (damage protection)

  4. Detector • about 3800 ionisation chambers + 320 Secondary emission detectors • measure the secondary shower outside the cryostats created by the losses

  5. Superconducting magnet Channel 1 Optical TX Multi-plexing and doubling Detector Digitalization TUNNEL Optical TX Secondary particle shower generated by a lost Channel 8 VME Backplane SURFACE Optical RX Demulti-plexing Signal selec-tion Thres-holds comp-arison Channel selection and beam permits gener-ation. Unmaskable beam permits FEE 1 Optical RX Demulti-plexing Maskable beam permits FEE 2 Beam Energy Status monitor BLMS Signal Chain Front End Electronics (FEE) Back End Electronics (BEE)

  6. Thresholds and interlocks • 12 running sums for 32 energy levels for each channel, 16 channels per card, 345 surface cards. → table of 2 millions values! • Any of this signal over the thresholds generate a beam dump request via the BIC

  7. 1. Principle of the simulation • Loss pattern given by R. Assmann team (C. Bracco, S. Redaelli, G. Robert-Demolaize) • GEANT 3 simulation of the secondaries shower created by a lost proton impacting the beam pipe • simulation of the detector response to the spectra registered in the left and right detector (M. Stockner with G4) • 500 protons same z position and same energy • impacting angle is 0.25 mrad • longitudinal scan performed to optimize the BLM location

  8. Definition of the thresholds • Loss pattern given by R. Assmann team (C. Bracco, S. Redaelli, G. Robert-Demolaize) • GEANT 3 simulation of the secondaries shower created by a lost proton impacting the beam pipe • simulation of the detector response to the spectra registered in the left and right detector (M. Stockner with G4) • 500 protons same z position and same energy • impacting angle is 0.25 mrad • longitudinal scan performed to optimize the BLM location

  9. Geometry description 3 transverse positions of impact outermost, innermost and top

  10. Typical result • Maximum of the shower ~ 1m after impacting point in material • increase of the signal in magnet free locations • factor 2 between MQ and MB z (cm)

  11. Particle Shower in the Cryostat Position of the detectors optimized to: • catch the losses: • MB-MQ transition • Middle of MQ • MQ-MB transition • minimize uncertainty of ratio of deposited energy in the coil and in the detector • B1-B2 descrimination

  12. 2. Position in the ARCS • Example of topology of Loss (MQ27.R7) • Peak before MQ at the shrinking vacuum pipe location (aperture limit effect) • End of loss at the centre of the MQ (beam size effect) More simulation are needed to get better evidence (higher populated tertiary halo)

  13. Particle shower in the detector • Addition of all the weighted signals from the previous locations • Positions chosen for the arcs also optimum for the DS.

  14. BLMs for the arcs beam 1 • Mainly BLMQI at the Quads (3 monitors per beam) + cold dipoles in LSS • Beam dump threshold set to 30 % of the quench level (to be discussed with the uncertainty on quench level knowledge) • Thresholds derived from loss maps (coll. team), secondaries shower simulations (BLM team), quench level simulations and measurements (D. Bocian) beam 2

  15. BLMs for warm elements beam 2 top view beam 1 • BLM in LSS :at collimators, warm magnets, MSI, MSD, MKD,MKB, all the masks… • Beam dump threshold set to 10 % of equipment damage level (need equipments experts to set the correct values

  16. Mobile BLM • use the spare chambers • use the spare channels per card : 2 in the arcs at each quad, a bit more complicated in the LSS. • electronics is commissioned as for connected channel • a separate Fixed display for non-active channels is planned : to be discussed • detection thresholds: ???

  17. Generation of threshold table • Quench and damage level threshold tables will be created for each family of BLM locations. • They will be assembled together into MASTER table. • For every location a threshold for 7 TeV will be calculated. • Table will be filled using parametrized dependence on Energy and Integration time. • MASTER table, MAPPING table (BLM location vs electronic channel) will be stored in safe database.

  18. Calibration and Verification of Models Calibration needed for: verification: Detector model (Geant) = (CERN /H6) Detector(particle - energy spectrumdependence) Magnet model (Geant)=HERA beam dump(tails of shower measurements) Shower code(prediction error large for tails) Threshold table Magnet quench(2 dim, energy, duration, large variety of magnet types) Magnet model (SQPL)(heat flow, temp. margin, …)= fast loss: sector testslow loss: SM18

  19. Reasons to change the thresholds? How often? • to check Machine Protection functionalities of BLMs (interlocks):decrease the thresholds in order to provoke a dump with low intensity • frequency: during the commissioning, after each shut-down (?), for a set of detectors • study/check of quench levels (“quench and learn” strategy?): implies dedicated MD time, post-mortem data analysis, could be related to check the correct setting of the thresholds • Frequency : ? Probably during shut-down • For HERA, only one change since the start-up

  20. commissioning of individual systems (MSI, LBDS, collimators): to get a loss picture of a region, to give “warning” levels • adjust thresholds after studies of the systems to optimize the operational efficiency vs. the irradiation level • frequency : 1 or 2 iterations after determination of the thresholds and localized in space (injection region, IR7…) • To match quench level during commissioning (operational efficiency): • Probably few iterations • some flexibility would help operation but is not an absolute need

  21. relative accuracies Correction means Electronics < 10 % Electronic calibration Detector < 10 – 20 % Source, sim., measurements Radiation & analog elec. about 1 % fluence per proton < 10 - 30 % sim., measurements with beam (sector test, DESY PhD) Quench levels (sim.) < 200 % measurements with beam (sector test),Labmeas., sim. fellow) Topology of losses (sim.) ? Simulations Systematic Uncertainties at Quench Levels B. Dehning, LHC Radiation Day, 29/11/2005

  22. 3. Proposed implementation • Threshold GUI • Reads the “master” table • Applies a factor (<1) • Saves new table to DB • Sends new table to CPU • CPU flashes table if allowed (on-board switch) • Thresholds are loaded from the memory on the FPGA at boot. • Combiner initiated test allows CPU to read ‘current’ table. • SIS receives all tables • Compares tables • Notifies BIS (if needed) Note: possible upgrade by adding a comparison with master table on the board BUT feasibility has to be checked

  23. Consequences on the reliability of the system? • Flexibility given by changing remotely the thresholds has to be balanced with the loss of reliability of the system • The proposed implementation allows both possibilities • But the remote access will have to be validated by machine protection experts when more detailed implementation of MCS and comparator are available (by the beginning of summer?).

  24. System ready for LHC and fulfill the Specifications? • Hardware expected to be ready for LHC start-up • Threshold tables (calibration of BLM) based on simulations. • Analysis effort of BLM logging and post-mortem data (LHC beam data, “parasitic” and dedicated tests) to be started in 2006! • Calibration of threshold tables • Interpretation of BLM signal pattern • Extensive software tools for data analysis essential to fulfill the specifications! Start now to specify and implement

  25. BLMS Testing Procedures PhD thesis G. Guaglio Detector Tunnel electronics Surface electronics Combiner Functional tests Barcode check Current source test (last installation step) Radioactive source test (before start-up) HV modulation test (implemented) Beam inhibit lines tests (under discussion) Threshold table beam inhibit test (under discussion) 10 pA test (implemented) Double optical line comparison (implemented) Thresholds and channel assignment SW checks (implemented) Inspection frequency: ReceptionInstallation and yearly maintenanceBefore (each) fillParallel with beam

  26. Beam energy Calibration magnet detector tunnel elec. surface elec. BIC LBDS Particle shower Environmental test Functional test Steps: Environmental test: temperature dose & single event Elec. tunnel, 15 – 50 degree Elec. tunnel, 20 year of operation & “no” single event effects Functional test: before installation during installation during operation All equipment, LAB, current and radioactive source Connectivity, current and radioactive source Connectivity, thresholds tables Calibration: before startup after startup Establishing model (detector, shower, quench behavior) a: no beam abort , no quench, no actionb: use loss measurements and models for improvements Commissioning Procedures - Steps

  27. Hardware commissioning • complete detailed procedure documented in MTF • functionalities linked with Machine protection will be reviewed in the Machine Protection System Commissioning working Group • validation of the connectivity topology: registration in database of the link position in the tunnel-channel identification-thresholds

  28. Commissioning with beam see presentation of A. Koshick in CHAMONIX Motivation of the test: • Establish thresholds = establish the correlation between quench level and BLM signal = Calibration! • Verify or establish „real-life“ quench levels • Verify simulated BLM signal (and loss patterns) • In particular: What BLM signal refers to the quench level of a certain magnet type? => Accurately known quench levels will increase operational efficiency!

  29. How to do the quench test: Implementation • if circulating beam, possibility to check steady state losses quench limit. If sector test, fast losses quench limit • Simple idea: Steer beam into aperture and cause magnet quench Initial conditions & requirements: • Pilot beam 5x109 • Clean conditions, orbit corrected (to better +/- 3 mm?). • BPM data/logging available  Trajectory • BLM data/logging available • Additional “mobile” BLMs at the chosen locations Vary intensity5x109 – max. 1x1011+logging all relevant data (BPM, BLM,BCT,emittance …) Set optics (3-bump) Magnet quench

  30. How to do the test: What we want to learn Beam Parameters • Emittance • Intensity • Momentum spread Optics Parameters • -function • Dispersion • Trajectory/Orbit Impact Length Impact Position Proton density that caused quench in SC magnet Determination of quench level Calibration BLM signal

  31. Conclusions • Controlled, defined test to establish • Absolute quench limits • BLM threshold values • Model and understanding of correlation of loss pattern, quench level, BLM signal • This test is essential for an early calibration of the BLM system, even if beam time consuming • It has to be done before increasing intensity

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