23.01.2006Chamonix 2006, B.Dehning 1 Commissioning of Beam Loss Monitors B. Dehning CERN AB/BDI.
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Transcript of 23.01.2006Chamonix 2006, B.Dehning 1 Commissioning of Beam Loss Monitors B. Dehning CERN AB/BDI.
23.01.2006 Chamonix 2006, B.Dehning 1
Commissioning of Beam Loss Monitors
B. DehningCERN AB/BDI
23.01.2006 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
Dumpsystem
Interlocksystem
Dumprequests
23.01.2006 Chamonix 2006, B.Dehning 3
Damage and Quench LevelsRelative loss levels for
fast / slow losses450 GeV
7 TeV
Damage level
3205
100025
Quench level
11
11
Dump threshold
0.30.3
0.30.4
1.E+06
1.E+07
1.E+08
1.E+09
1.E+10
1.E+11
1.E+12
1.E+13
1.E+14
1.E+15
1.E+16
1.E-02 1.E-01 1.E+00 1.E+01 1.E+02 1.E+03 1.E+04 1.E+05 1.E+06
duration of loss [ms]
quen
ch le
vels
[pro
ton/
m/s
]
total quench levels at 450 GeVtotal quench levels at 7 TeV
He heat flow
He heat reserve
heat flow between cable and He
heat reserve of
cable
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
Pilot450 GeVdamage
23.01.2006 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 actionb: 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 testEnvironmental test
Beam energy
detector LBDSBICsurface elec.tunnel elec.magnetParticle shower
23.01.2006 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:
23.01.2006 Chamonix 2006, B.Dehning 6
Uncertainties after Model Corrections
relative accuracies Correction means
Electronics < 10 % Electronic calibration
Detector < 10 – 20 %
source/sim./measurements
Radiation - SEE about 1 % Particle shower prediction
< 10 - 30 %
sim. / measurements with beam (sector test)
Quench levels (sim.) < 200 % measurements with beam (sector test) / scaling
Topology of losses (sim.) < large sim. / measurements
Largest uncertainties in quench model and topology of losses
23.01.2006 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
23.01.2006 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
23.01.2006 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 BOOSTER
BOOSTER
T2T2
T2
H6 H6
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%
23.01.2006 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
23.01.2006 Chamonix 2006, B.Dehning 11
Dose Measurements at the HERA Beam Dump
Protons: 1 1013
E = 920 GeV Peak
corresponds to 1.5 Gy
Radiation 3.5 orders lower after 1 s
Verification of longitudinal profile with Geant simulation
23.01.2006 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,
23.01.2006 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
23.01.2006 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)
23.01.2006 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