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Session 4: Chairman: S. Russenschuck, Scientific
Secretary: R. Jones
Other Issues affecting Beam Commissioning (I)
 Electrical Quality Assurance (Davide Bozzini)
 Report from the Magnet Polarity Coordinator (Stephan Russenschuck)
 Quench Protection System (Reiner Denz)
 Consequences of RF System Failures during LHC Beam Commissioning
Stephan Russenschuck, CERN-AT-MEL
(Trevor Linnecar)
 Initial Commissioning of Critical Beam Instrumentation Systems
(Eva Barbara Holzer)
 The Estimation of Individual and Collective Intervention Doses for the LHC
Beam Cleaning Insertions (Markus Brugger)
 The LHC Access System: Why do we put Doors (Luigi Scibile)
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ELQA (1) Accessibility
 PS machine “warm”. Electrical
circuits are easily accessible and
visible
Stephan Russenschuck, CERN-AT-MEL
 For diagnostics almost all senses
can be used: hearing , visual, smell,
touch
 LHC machine “cold” electrical circuits will not be
directly accessible
 This picture shows the String 2 phase 1, i.e. 54
meters without access to the circuits. Diagnostic
has been a nice exercise. LHC machine will be
2700 m!
 Diagnostic may require the local access to the
circuit (opening of interconnections).
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ELQA (2) Classification of the electrical faults
Stephan Russenschuck, CERN-AT-MEL
The notorious one’s
Fault
Consequence
Detection
Diagnostic method
Inverted polarity of a
magnet within a series
(ex: MCS)
Beam quality
- BPM’s
- Beam observations
- Polarity check
Open circuit of a main
circuit
Beam abort
- QPS
- Power converter
- Continuity check
- Transfer function
Short to ground of a
main circuit
Beam abort
- Power converter
- High voltage test
- Transfer function
Loss of
instrumentation used
for magnet protection
Beam abort
- QPS
- Continuity check
- TDR
……………..
……………….
……………………
…………………
The malicious one’s
Fault
Consequence
Detection
Diagnostic method
Quench of bus bar
segments or splices
Beam abort
- QPS
?
Transitory shorts to
ground or between
circuits
Beam abort
- Power converters
?
High ohmic resistance
of bus bar interconnect
?
- QPS
- Cryo system
…………………
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ELQA (3) Staff experience and resources
 Fundamental experience will be acquired during machine assembly and hardware
commissioning
 Beam commissioning starts in 2007 most of the knowledge will be gone
 Success of ELQA activities during beam commissioning need experienced and
well trained personnel
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Beam commissioning
and operation
HNINP collaboration
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Nr. of person
Stephan Russenschuck, CERN-AT-MEL
 Interventions during
beam commissioning
and operation will have
to deal with radiation
 Staff shall be familiar
not only with the ELQA
procedures but also with
safety rules and tunnel
environment
Hardware
commissioning
Assembly
FSU
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Tech. Students
12
Staff
10
8
6
 Sector test would be
helpful for ELQA
optimization
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2
0
Q1
2005
Q2
2005
Q3
2005
Q4
2005
Q1
2006
Q2
2006
Q3
2006
Time
Q4
2006
Q1
2007
Q2
2007
Q3
2007
Q4
2007
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Progress Report of the Magnet Polarity Coordinator
Share with me
 The confusion about the Magnet Polarity Conventions.
 The doubts about the Polarity of the Main Quadrupole.
Stephan Russenschuck, CERN-AT-MEL
 The worries about the continuity of the Spool-piece Busbars.
 The passion for the following
question: 9:00 or 3:00?
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Stephan Russenschuck, CERN-AT-MEL
LHC Magnet Polarities EDMS: 90042
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Polarity (3) Conversion Table: Dipoles (and B3, B5, ..)
MAD
H Kicker
V Kicker
B1
B1
A1
A1
(B0n)
(B0n) tilt
(B0s)
(B0s) tilt
Clockwise
Deflecting
Clockwise
out
up
in
down
up
in
EDMS
Negative
Negative
Positive
Positive
Negative Positive
90042
dipole
skew
dipole
skew
skew
dipole
dipole
A1
-A1
Stephan Russenschuck, CERN-AT-MEL
Beam 1
(Polarity)
Meas.
dipole
- B1
-A1
B1
dipole
B1
Mag.
Frame
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Stephan Russenschuck, CERN-AT-MEL
Polarity (4) Concern: Spool-piece Busbar Routing
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Stephan Russenschuck, CERN-AT-MEL
Polarity (5) Spool-piece Busbar Routing in the SSS
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Stephan Russenschuck, CERN-AT-MEL
Polarity (6) Continuity Checker
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Protection of LHC superconducting elements
 Protection of LHC superconducting
elements, commonly referred as Quench
Protection System (QPS)
– Concerns all superconducting circuits
with I ≥ 600 A
• Main dipoles and quads
• Main busbars
Stephan Russenschuck, CERN-AT-MEL
• HTS current leads
• Insertion region magnets and
busbars
• Corrector magnets and busbars
– Quench detection systems, quench
heater power supplies, energy
extraction systems & data acquisition
systems
– 170 tons of electronic, 3820 quench
detection systems
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QPS (2) Conclusions
 QPS system will be fully commissioned and available prior to beam
commissioning
 QPS equipment is designed for high reliability and availability
– QPS test mode, high resolution mode for leads and 13 kA busbars
 Triggers of the protection system normally stop LHC
 In a significant number of cases failures of the QPS system will cause a
Stephan Russenschuck, CERN-AT-MEL
stop of the LHC (a faulty trigger a day keeps the Higgs away)
 Interventions are time consuming but cannot be avoided
 The QPS data acquisition systems provide valuable information on the
status of the LHC cold mass and possible failures inside
 Magnets close to the interaction point are well protected but should not be
necessarily regarded as “beam loss monitors”
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Consequences of RF system failures during LHC beam
commissioning.
T.Linnecar, O. Brunner, E. Ciapala,
Stephan Russenschuck, CERN-AT-MEL
E. Shaposhnikova, J. Tuckmantel, AB-RF
Analysis:
Loss of one or more 400 MHz cavities
Issues:
Hardware protection
beam induced over-voltage 3 MV max
power induced by beam in load 300 kW max.
Effects on the beam
transient effects – emittance blow-up, beam loss
instability from cavity impedance
reduced voltage for acceleration – beam stored lifetime
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RF Failures and Consequences
 Beam present during trip
– Beam should survive with a trip of 2 cavities up to ½ nominal beam
current.
– To do this, work at ½ de-tuning and lower Qext. (possible because
power is available
– Coupler and tuner must remain under control. Beam dump interlock
should come from Vcas and Pload
 New injection
Stephan Russenschuck, CERN-AT-MEL
– Can inject and accelerate with up to 4 cavities off, up to ½ nominal
beam current (with reduced luminosity)
– Work at ½ de-tuning and lowest possible Qext.
– Frequency stability of the passive cavity must be  0.75 kHz (He
pressure  5 mbar).
 General
– Beam dump interlock from Pload and Vcav (also He pressure for
quenches), not from a trip.
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Beam Instrumentation (1) BPM
 Polarity (still some errors possible)
– Cryostat cabling (no mix-up, pre-formed cables)
– Errors in front of the electronics are impossible to verify remotely after
installation – will be seen with beam and can be visually inspected.
– Errors after electronics are easier to track down (mixed up BPMs) and
should be spotted during hardware commissioning as each station is
turned on individually.
– Same electronics and procedure had been used in TI8:
• 3 planes of 51 gave problems (5%)
Stephan Russenschuck, CERN-AT-MEL
• 5% for LHC would imply 50 incorrect or broken planes per beam.
 Database Issues
– Position of beam 1 and beam 2 (especially for turned cryo-magnet
assemblies)
– Calibration / linearization database errors
• wrong BPM type  wrong position readings
• wrong linearization / calibration constants  reduced accuracy
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Beam Instrumentation (2) Sector Test
 BPM
– Commissioning of BPMs in the sector (polarity checks, timing, database
issues) and a part of the functionality of the BPM system.
– Possibility to find problems and fix them before LHC start-up.
 BLM
Stephan Russenschuck, CERN-AT-MEL
– Commissioning of a part of the functionality of the BLM system (dump
signal, setting of thresholds and beam flags, database issues, logging,
post mortem, offline analysis).
– Quench level calibration: Controlled beam loss in cold magnet equipped
with several BLMs.
– Longitudinal loss patterns (only way for measurements before LHC
start-up).
– Possibility to find problems and fix them before LHC start-up.
– Could prove very useful considering the complexity of the system and
the time needed to implement changes or fix problems.
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Intervention Doses
Individual and Collective Doses at IR7
Issues and goals
– Strong activation of components due to high losses causing significant
residual dose rates!
– Time-consuming interventions can be expected for base-line layout.
– Installation of Phase 2 collimators in highly radioactive area.
– Optimization of the design to minimize individual and collective doses
received by personnel during interventions and machine upgrades.
Stephan Russenschuck, CERN-AT-MEL
– Estimates of individual and collective dose are legally required (INB
documents, external companies must be certified)
Methods
– Results on residual dose rates are available from detailed
FLUKA Monte Carlo simulations (for IR7).
– Intervention scenarios are needed from intervening groups (uncertainty in
the interventions, not in the dose rates).
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Stephan Russenschuck, CERN-AT-MEL
Collimator Exchange – All Steps
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Intervention Doses
Individual and Collective Doses at IR7
Results
– Significant individual and collective doses, exceeding those of so far received
during SPS interventions.
– Therefore, optimization of the design is of utmost importance for a fast
collimator exchange.
– Based on the results of the calculations first design modifications have
already been implemented:
Stephan Russenschuck, CERN-AT-MEL
• fast connections for flanges (chain clamps instead of bolts)
• optimization of the orientation of magnets
(connections away from high loss points)
– Further optimization will be necessary, e.g,:
• remote bakeout system
• remote alignment system
• use of radiation-hard components/cables where possible
• use of mock-ups for intervention planning
• implementation of procedures
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LHC Access Control System
Goals:
– Manage access right
– Identify user
– Verify authorization (training)
– Automatic or remote access control
Stephan Russenschuck, CERN-AT-MEL
Status
– Contract running
– System engineering completed
– Site acceptance of “LHC 0” June 2005 (operational prior to
machine commissioning)
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Stephan Russenschuck, CERN-AT-MEL
LHC Access Safety System
Goals:
– Protect personnel during Beam operation
– Allows Access operation when safety conditions are met
• No radiation hazards (LHC beam, RF)
– Distributed, highly reliable interlock system
– Completely tested before Cold Checkout
Status:
– Specifications review EDMS 456549 (Access Safety Working Group)
– HW and SW Architecture prototyping (Siemens Safety Matrix)
– Contract for the system integration, installation and commissioning.
– On going safety studies
Special request to AB:
– To finalize the list of equipment which needs to be interlocked with the
access (RF test when during HW commissioning).
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