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