Transcript LHC Commissioning Phases: Phase 1-

LHC Systems
Cryogenics….as seen by “Beam
Handlers”
G. Arduini, S. Redaelli
Many thanks to:
A. Butterworth, S. Fartoukh, M. Giovannozzi, A. Rijllart, L.
Serio, F. Zimmermann
LHC Commissioning WG, 22/05/2007
Outline
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LHC Cryogenic system overview
Instrumentation and Signals
Cryo-Organization during Beam Commissioning
Application SW
Cryogenics & powering
Cryogenics & commissioning with beam
What could go wrong during beam commissioning?
Tools needed
Summary
LHC Commissioning WG, 22/05/2007
LHC cryogenic system layout
Even point
Odd point
MP Storage
MP Storage
MP Storage
1.8 K
Refrigeration
Unit
New
4.5 K
Refrigerator
1.8 K
Refrigeration
Unit
Warm
Compressor
Station
Warm
Compressor
Station
Warm
Compressor
Station
Cold Box
Upper
Cold Box
Distribution Line
Magnet Cryostats, DFB, ACS
LHC Sector (3.3 km)
Interconnection Box
Cold
Compressor
box
Distribution Line
Magnet Cryostats, DFB, ACS
LHC Sector (3.3 km)
L. Serio
LHC Commissioning WG, 22/05/2007
Tunnel
Cold
Compressor
box
Lower
Cold Box
Cavern
Shaft
Warm
Compressor
Station
Existing
4.5 K
Refrigerator
Surface
Odd point
LHC Cryogenic System layout
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No redundancy for sector 2-3 in case of problems with the cryogenic unit in point 2 and
no fast cool-down possible
Naming:
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–
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Q= Cryogenic System
S, U = Surface, Undergorund
C, R, I = Warm compressor, Refrigerator, Interconnection Box
LHC Commissioning WG, 22/05/2007
LHC Cryogenic Components in Tunnel
10000
SOLID
Thermal Shields
1000
CRITICAL PT
P [kPa]
HeI I
100
Arc
Magnets
Special
Magnet
s
RF
Cavities
HeI
Beam Screens
HTS Part
of Current Leads
Resistive Part of Current Leads
GAS
10
Heat
Exchanger
Tubes
1
1
10
LHC Commissioning WG, 22/05/2007
T [K]
100
300
1000
L. Serio
Instrumentation and signals
• Available instrumentation and signals in the tunnel:
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Pressure gauges (PT)
Temperature gauges (TT)
Level gauges (LT)
Valve opening (CV)
Virtual flow meters at the valves (based on pressure drop and
temperature measurements, tables on He characteristics, valve
opening, etc..) (FT)
For T<30 K
For T>30 K
LHC Commissioning WG, 22/05/2007
Instrumentation and signals
Mid Sector
TT
PT
TT
PT
TT
PT
TT
TT
Positive Slope
PT
LT
TT
TT
TT
TT
LT
TT
TT
TT
TT
Standard Cell
TT
TT
TT
TT
TT
TT
TT
Standard Cell
Cryo Cell
LHC Commissioning WG, 22/05/2007
TT
L. Serio
Instrumentation and signals
LHC Commissioning WG, 22/05/2007
Cryo-Organization during Beam Commissioning
• On-line:
– Planned: 1 × 8 h shift + on-call operators and experts
– Possible: 2 × 8 h shift + on-call experts (as for HW commissioning)
– Ideal: 3 × 8 h shift + on-call experts
• In the case of process faults (e.g. spurious faults, partial HW faults) the
presence of a cryo-operator could limit the recovery time and even avoid
beam-dumps and could be essential in case of teething problems
• Off-line:
– Cryogenic Performance Panel (CPP – Chair: L. Serio):
• Analyze off-line, manage all aspects of cryogenic performance,
• Study, propose improvements of functional procedure and consolidations,
• Record and track cryogenic sub-system performance in relation to their
manufacturing and test data.
• Design and set-up of the tools for the additional on-line monitoring of the
cryogenics during beam commissioning
•  provide crucial feedback for the “steering” of the beam commissioning
LHC Commissioning WG, 22/05/2007
Application SW
• High level of detail in the
application available in CCC.
• Possible to navigate through the
Cryogenic system.
• Four access levels (the first three with password):
– Administrator: omnipotent
– Expert login: for experts only, direct control on each piece of equipment of the
cryo system. Possibility to change interlock level.
– Operator: can operate the system, accessing the equipment but cannot
change interlock levels.
– Monitor: Read access only  this is the mode in which we should use the
application
• Under deployment: nominative access with role-based rights
LHC Commissioning WG, 22/05/2007
Sector 7-8 – Navigation bar
LHC Commissioning WG, 22/05/2007
Sector 7-8 (arc)
Green=OK
Yellow=Warning
Red=Not Ok
Blue=Invalid Data
Purple=Not Avail.
LHC Commissioning WG, 22/05/2007
Sector 7-8 – Navigation bar
LHC Commissioning WG, 22/05/2007
Sector 7-8 – Inner Triplet L8 + DFBX
LHC Commissioning WG, 22/05/2007
Temperature overview for each sector
LHC Commissioning WG, 22/05/2007
Signal overviews for the Sectors
Cold Mass
temperatures
Line C temperatures
LHC Commissioning WG, 22/05/2007
Pressures
He levels
Sector 7-8 (arc)
LHC Commissioning WG, 22/05/2007
Trends
• Predefined sets or operator defined
• Possibility to select the trend of one parameter from overview or
synoptic plot
LHC Commissioning WG, 22/05/2007
Cryogenics Post-Mortem - General information
• PM analysis based on check functions defined by experts
– LabView Logic specified by the Cryogenics Performance Panel in Excel
tables, interpreted by a LabView program, this is part of the Magnet PM
analysis software provided by CO/MA.
• Four PM event triggers: CRYO_START, CRYO_MAINTAIN, QUENCH,
ALARM. They can be triggered on request  PM can be used also as
analysis tool!
• For the moment, only expert logic is implemented
• The tools seem flexible: it should be possible to add a “beam-oriented”
logic for the PM analysis.
• PM application retrieves data from the logging data-base
– Delay of a few minutes before data are available for analysis
– Inconsistency between the logging and measurement DB have been
observed
– Filtering and smoothing of the data before transfer to the logging DB can
false the trends
–  why not accessing the measurement data-base?
LHC Commissioning WG, 22/05/2007
Cryogenics Post-Mortem application - snapshots
Display of
selected
signals
Main table with
results of PM
analysis (analysis
Buttons that simulated 4 PM events
(CRYO_START,CRYO_MAINTAIN,QUENCH,ALARM)
Signals for
the plot
type and results
given)
Faulty signals
(did not pass the test)
LHC Commissioning WG, 22/05/2007
Signals with
no data (last
acquisition
reported)
Some additional features
Sorting results
(signal name,
analysis type)
Possibility to save
and retrieve the
results of the
analysis are
available and
required in
particular if access
to the
measurement DB is
implemented
LHC Commissioning WG, 22/05/2007
Signals to
graph
Cryogenics conditions for powering
There will be three logic states for each powering sub-sector:
1. Conditions to authorize magnet powering (CRYO_START=TRUE and
CRYO_MAINTAIN=TRUE)
2. Conditions that do not authorize magnet powering but if there is already
current in the magnets there is no request for discharge (the conditions
of magnet powering were met at the time of the start of powering but
have disappeared meanwhile) (CRYO_START=FALSE and
CRYO_MAINTAIN=TRUE)
3. Conditions that do not authorise magnet powering and request a slow
current discharge (CRYO_START=FALSE and CRYO_MAINTAIN=FALSE)
• 32 Powering sub-sectors:
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3 types per sector:
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IT+D1 (in IR2 and 8)+DFBX (8 in total)
Matching Section: standalone magnets @ 4.5 K+DFBM,DFBL,DSL (12 in total)
ARC + DFBA (8 in total)
4 RF modules
LHC Commissioning WG, 22/05/2007
CRYO_START / MAINTAIN
• No direct connection of Cryo with BIC but only with PIC
• Only insulation vacuum is directly interlocked to cryogenics (<10-3 mbar,
expect a steady state of 10-6 mbar if no leaks).
• No direct connection (no interlocking) between Beam Vacuum and
Cryogenics: Bad beam vacuum  Higher heat load  CRYO_START and
CRYO_MAINTAIN might disappear
LHC Commissioning WG, 22/05/2007
Cryogenics & commissioning with beam
• Assumptions:
– The Cryogenics system should be fully commissioned during the HW
commissioning period  in that case its behaviour as a function of
the powering levels (energy dependence) should be understood
• The main remaining unknown is the interplay of the beam
with the cryogenics system:
– Heat load on the beam screen due to:
• resistive dissipation of image currents
• synchrotron radiation
• electron cloud
– Heat load on the cold masses due to:
• Nuclear inelastic beam-gas scattering (depending on the vacuum level)
• Other type of beam losses (e.g. beam halo losses and energy deposition
from the induced showers)
LHC Commissioning WG, 22/05/2007
Cryogenics & commissioning with beam
per aperture
~600
~900
~1300
~2200
L. Tavian – LTC 2/6/2004
F. Zimmermann – LTC 6/4/2005
LHC Commissioning WG, 22/05/2007
Cryogenics & commissioning with beam
LHC Design report
L. Tavian – LTC 2/6/2004
• A priori no need for dedicated time for cryogenics studies with beam
but “parasitic follow-up” of the behaviour of the cryogenics in the
presence of beam as a function of its parameters  monitoring by
Cryogenics Performance Panel. Its feedback will be crucial in
“steering” the commissioning (in particular the increase in intensity)
LHC Commissioning WG, 22/05/2007
Critical elements
• Are there elements which are more critical than others?
– Magnets:
• Q6 in IR1 and 5 (standalone magnet at 4.5 K) as evidenced by quench behaviour
• MQTLs
• In general SC magnets close to collimation areas and triplets in the interaction
points
• Q4 close to the beam dump area
– Interaction with and feedback from MPP is vital to define critical elements
– RF:
• Coupling with the rest of the sector might be an issue
• Little margin for the pressure levels  Beam dump at 1.5 bar
• Cryo limit could be reached if we try to run with less cavities but higher field
• Sector 2-3: no redundancy
• Sector 3-4 and 4-5 are the most critical:
– From the point of view of the heat load (due to the additional load from the
RF in IR4)
– 4-5 is also critical from the point of view of the temperature due to the
hydrostatic heads because of the slope on the LHC ring
LHC Commissioning WG, 22/05/2007
What could go wrong during beam commissioning?
L. Serio – AB/OP shutdown courses –
7/3/2007
Cryo commissioning
presently ongoing is the
first chance to test all
the systems together
and their interactions.
More might have to be
learned when we will
start to inject beam.
LHC Commissioning WG, 22/05/2007
What could go wrong during beam commissioning?
• Quenches will be the “routine”……
L. Serio – Training
Day for the
Commissioning of the
LHC Powering
System – 29/3/2007
• More than 14 cells or full sector  recovery up to 48 hours
• In case of fast discharge (even w/o quench)  2 h recovery
(heating due to eddy currents).
LHC Commissioning WG, 22/05/2007
What could go wrong during beam commissioning?
• Strong correlation cryogenics
vacuum:
– Vacuum transients might result
from:
• excessive condensation of
gases on the beam screen in the
cells adjacent to a quenched one
 warming-up of the Beam
Screen (to ~40 K) might be
required (few hours required)
before injecting
• Operation of the beam screen at
temperatures close to 24 K
(instead of 20 K) e.g. as a result
of localized losses can result in
emission of CO from the Beam
Screen and reduced lifetime
LHC Commissioning WG, 22/05/2007
V. Baglin – Chamonix XIII
What could go wrong during beam commissioning?
• Heat loads above specifications
– In that case heat load measurements and comparison with expectations are
essential before any increase in intensity
– The resolution in heat load on the beam screen is ~0.5 W/cell to be
compared with 280 W/cell as expected beam induced heat load at nominal
intensity at 7 TeV. The expected margin in nominal conditions is ~40 W/cell.
Possible mean to see pressure bumps?
– Local heating on cold masses can be measured with the resolution of a cell
and localization within a cell might be possible by measurements of the
temperature difference between magnets
• EM-interference induced by the beam on the sensors
– Past experience (SPS) has shown that sensors (e.g. temperature sensors)
can be affected by the beam presence in particular for high intensity
– Main difference: sensors are not in direct view of the beam
– Countermeasures: redundancy and “filtering”
– This should manifest itself as a non-deterministic behaviour of some of the
control loops.
– Could be a nightmare…
LHC Commissioning WG, 22/05/2007
Tools needed
• Certainly we will need a summary of the Cryo Maintain/Start conditions
for the different Sub-Sectors
• Available soon
L. Serio
LHC Commissioning WG, 22/05/2007
Tools needed
• If the Cryogenics parameters start to drift on time scales of minutes
probably there is not much that we (or the Cryogenics Expert) can do to
re-establish stable conditions and “save” the beam
• Follow-up of the trends when the mode of operation is changed (intensity
or energy variation) is vital for planning the commissioning steps and
minimizing down-time
• We could specify analysis types relevant for LHC operation in the PM
and trigger it via alarms (on trends) or external triggers.
– Define virtual heat loads on beam screens and cold masses from
temperature, flow, pressure measurements and heater setting (started by
CPP)
– Monitor heat load and temperatures on beam screen and cold mass,
correlate with vacuum, beam intensity, beam losses and compare with
expectations
– Add temperature/flow trends to identify “critical” behaviour based on signal
evolution
• Later fixed-displays could take over…once the measurements and
measurement devices are fully mastered and the needs and problems
clarified
LHC Commissioning WG, 22/05/2007
Summary
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The behaviour of the cryogenics as a function of the powering levels (energy
dependence) should be understood before beam commissioning  a priori no
dedicated time required during beam commissioning but the “beam presence”
might introduce additional unexpected effects….
•
The presence of cryo-operators on 3 x 8 h shift during beam commissioning
could help to sort-out potential teething problems of the cryo-system and to
reduce beam down-time during the commissioning.
•
Interaction with CPP and MPP should be strengthened in order to focus on the
critical elements and refine the analysis tools for beam commissioning.
•
Detailed SW tools exist to assist the expert in the control of the cryogenic system
•
For beam operation heat loads are probably the most meaningful parameters:
understanding of their trends could be very useful to identify and anticipate
problems. The resolution (also spatial) should be sufficient.
•
Non-expert tools need to be “enhanced”  The post-mortem analysis “fishing” in
the measurement DB could be a powerful tool for the Beam Commissioning
period although later fixed displays could be developed.
LHC Commissioning WG, 22/05/2007
References
• LHC Design Report – Chapter 11 - Cryogenics
• LHC-Q-ES-0004 (EDMS 710799): The circuit of the LHC cryogenic system
• LHC-Q-ES-0003 (EDMS 710797): Functional analysis of the LHC cryogenic
system process
• L. Serio, Cryogenics and powering - Training Day for the Commissioning of
the LHC Powering System – 29/3/2007
• L. Serio, LHC Cryogenics – AB/OP shut-down Courses – 7/3/2007
• L. Tavian, LTC 02/06/2004
• F. Zimmermann, LTC 06/04/2005
• V. Baglin, Vacuum Transients during LHC Operation, Chamonix XIII
LHC Commissioning WG, 22/05/2007