Chamonix 2006, B.Dehning 1 Commissioning of Beam Loss Monitors B. Dehning CERN AB/BDI

Chamonix 2006, B.Dehning 2 Damage Protection and Quench Prevention Protection of LHC between 0.4 and 10 ms only given by BLM system Prevention of quench only by BLM system QPS system contributes to damage protection HERA Tevatron, LHC Dump system Interlock system Dump requests

Chamonix 2006, B.Dehning 3 Damage and Quench Levels Relative loss levels for fast / slow losses 450 GeV 7 TeV Damage level Quench level Dump threshold Pilot bunch at: 450 GeV just above quench limit (distribution of loss) 7 TeV just at the damage limit Ratio damage to quench: fast: large => abort of beam at quench level ensures safety for damage slow: small => two system detect losses (new estimates needed) Change of energy needed to gain 2 to 3 orders in quench level at 450 GeV Pilot 450 GeV damage

Chamonix 2006, B.Dehning 4 Commissioning Procedures - Steps 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 action b: use loss measurements and models for improvements Environmental test: temperature dose & single event Steps: Elec. tunnel, 20 year of operation & “no” single event effects Elec. tunnel, 15 – 50 degree Calibration Functional test Environmental test Beam energy detectorLBDSBICsurface elec.tunnel elec. magnet Particle shower

Chamonix 2006, B.Dehning 5 Calibration and Verification of Models Shower code (prediction error large for tails) Magnet quench (2 dim, energy, duration, large variety of magnet types) Threshold table Detector (particle - energy spectrum dependence) Detector model (Geant) = (CERN /H6) Magnet model (Geant) = HERA beam dump (tails of shower measurements) Magnet model (SQPL) (heat flow, temp. margin, …) = fast loss: sector test slow loss: SM18 Calibration needed for:verification:

Chamonix 2006, B.Dehning 6 Uncertainties after Model Corrections relative accuracies Correction means Electronics< 10 %Electronic calibration Detector< 10 – 20 %source/sim./measurements Radiation - SEEabout 1 % Particle shower prediction< % sim. / measurements with beam (sector test) Quench levels (sim.)< 200 % measurements with beam (sector test) / scaling Topology of losses (sim.)< largesim. / measurements Largest uncertainties in quench model and topology of losses

Chamonix 2006, B.Dehning 7 Topology of Loss (MQ27.R7) Increase of losses approaching a MQ Peak in bin just before MQ End of loss at the centre of the MQ Basic assumption: transient losses will have same signature More simulation are needed to get better evidence (higher populated tertiary halo) Only beam 1 simulated yet Team R. Assmann Beam I Peak causes loss enhanced energy deposition in ends of coil

Chamonix 2006, B.Dehning 8 Particle Shower in the Cryostat Impact position varied along the MQ Black impact position corresponds to peak proton impact location Position of detectors optimized to catch losses: Transition between MB – MQ Middle of MQ Transition between MQ – MB to minimize uncertainty of ratio of energy deposition in coil and detector Beam I – II discrimination Beam L. Ponce Good probability that losses are seen by two BLM detectors

Chamonix 2006, B.Dehning 9 Detector Response for Various Beams Variation of factor 2 Intensity variation of 5 orders Momentum variation 2.5 orders Bunch length variation 8 orders BOOSTER T2 H6 Confidence in detector response over wide operational range Too large variation to reach a total accuracy of a factor of 2 in terms of the quench level => Absolute precision (calibration) < factor 2 initially: < factor 5 Relative precision for quench prevention < 25%

Chamonix 2006, B.Dehning 10 Beam Dump at HERA LHC measurement setup 6 chambers in top of internal dump 1 before and 1 after the dump Aim of setup Verification of Geant 4 simulation (far tail calibration, thesis M. Stockner) Observation of beam loss dynamic BLM system test

Chamonix 2006, B.Dehning 11 Dose Measurements at the HERA Beam Dump Protons: E = 920 GeV Peak corresponds to 1.5 Gy Radiation 3.5 orders lower after 1 s Verification of longitudinal profile with Geant simulation

Chamonix 2006, B.Dehning 12 Energy Deposition in Coil and Detector Sector test: Loss duration max few  s (SPS batch) => fast loss => no heat flow in magnet => simplest quench case Loss completely contained in the homogenous region of a MB magnet => optimal measurement conditions L. Ponce detector coil See talks A. Koschik, B. Goddard, L. Jensen,

Chamonix 2006, B.Dehning 13 Quench Level Tables Variations: about 10 important magnet types Variation of geometry Variation of quench levels due to different loss topologies Identification of groups of threshold levels to allow systematic treatment of calibrations: ARC beam1 first det. ARC beam1 second det. … MCS is needed for this task D. Bocian, M. Calvi, A. Siemko

Chamonix 2006, B.Dehning 14 Commissioning Steps Before start-up Continuation of proton loss studies to identify uncovered loss location, team R. Assmann Establishing of models for damage thresholds Collimators - Absorbers: Team A. Ferrari, B. Goddard Cold equipment: not defined jet, action needed Warm equipment: damage test SPS (V. Kain, R. Schmidt) Establishing of models for quench thresholds Enthalpy, heat flow and steady state limit: Team A. Siemko Energy deposition in coil and detector: Team B. Dehning Ion thresholds: Initial simulation are done: Team J. Jowett, action plan for creation of threshold not established yet To be prepared for excessive number of beam aborts or quenches Preparation of analysis tools for data treatment (logging and post mortem data bases are required as well as MCS) After start-up Analysis of beam losses causing beam aborts or quenches to identify/verify model uncertainties (parasitic to operation) Beam quench tests to optimise threshold tables (sector test will establish procedure)

Chamonix 2006, B.Dehning 15 Summary BLM system is the only system for fast loss damages BLM system is the only system for quench prevention Beam abort at quench level ensures safety for damage (fast losses) Slow losses are detected by BLM and quench protection system Threshold values are based on measurements and models models are needed to set the damage and quench levels for the various magnet types, loss locations, … (if not established, beam time will be used for optimisation) Commissioning steps before start-up Establishing as accurate as possible calibrations (threshold tables) Prepare tools for analysis of beam aborts and quenches (MCR, logging, post mortem) Commissioning steps after start-up Parasitic optimisation of threshold tables Beam induced quench tests Safe beam energy measurement and distribution (SIL3) is needed to gain 2 to 3 orders of magnitude in quench levels at 450 GeV compared to 7 TeV