Post on 24-Dec-2015
LHC Commissioning WG, 22/05/2007
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
• 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
UpperCold Box
Cold Box
WarmCompressor
Station
LowerCold Box
Magnet Cryostats, DFB, ACS Magnet Cryostats, DFB, ACS
ColdCompressor
box
Sh
aft
Su
rfa
ceC
ave
rnT
un
ne
l
LHC Sector (3.3 km) LHC Sector (3.3 km)
1.8 KRefrigeration
Unit
New4.5 K
Refrigerator
Existing4.5 K
Refrigerator
1.8 KRefrigeration
Unit
WarmCompressor
Station
WarmCompressor
Station
WarmCompressor
Station
ColdCompressor
box
Even pointOdd point Odd point
MP StorageMP Storage MP Storage
UpperCold Box
Interconnection Box
Cold Box
WarmCompressor
Station
LowerCold Box
Distribution Line Distribution Line
Magnet Cryostats, DFB, ACS Magnet Cryostats, DFB, ACS
ColdCompressor
box
L. Serio
LHC Commissioning WG, 22/05/2007
LHC Cryogenic System layout
• No redundancy for sector 2-3 in case of problems with the cryogenic unit in point 2 and no fast cool-down possible
• Naming: – 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
300 L. Serio
LHC Commissioning WG, 22/05/2007
Instrumentation and signals
• Available instrumentation and signals in the tunnel:– 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 KFor T>30 K
LHC Commissioning WG, 22/05/2007
Instrumentation and signals
Cryo CellCryo CellStandard CellStandard CellStandard CellStandard Cell
LTTT TT TT TT TT TT TT TT TT TT TT TT
PT
TT TT
LT
TT PT
TT PT
TT
TTTT TT TT
Positive Slope
PT
Mid Sector
L. Serio
LHC Commissioning WG, 22/05/2007
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=OKYellow=WarningRed=Not OkBlue=Invalid DataPurple=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
Pressures
He levels
Cold Mass temperatures
Line C temperatures
LHC Commissioning WG, 22/05/2007
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 type and results
given)
Buttons that simulated 4 PM events(CRYO_START,CRYO_MAINTAIN,QUENCH,ALARM)
Faulty signals(did not pass the test) Signals with
no data (last acquisition reported)
Signals for the plot
LHC Commissioning WG, 22/05/2007
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
Signals to graph
LHC Commissioning WG, 22/05/2007
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:– 3 types per sector:
• 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
L. Tavian – LTC 2/6/2004F. Zimmermann – LTC 6/4/2005
per aperture
~600
~1300
~900
~2200
LHC Commissioning WG, 22/05/2007
Cryogenics & commissioning with beam
• 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 Design reportL. Tavian – LTC 2/6/2004
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 shut-down 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”……
• 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).
L. Serio – Training Day for the Commissioning of the LHC Powering System – 29/3/2007
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
V. Baglin – Chamonix XIII
LHC Commissioning WG, 22/05/2007
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 soonL. 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
• 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