lhc commissioning wg, 22/05/2007 lhc systems cryogenics….as seen by “beam handlers” g....

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


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 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 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 Cryogenic Components in Tunnel

300 L. Serio


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



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


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


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


Sector 7-8 – Navigation bar


Sector 7-8 (arc)

Green=OKYellow=WarningRed=Not OkBlue=Invalid DataPurple=Not Avail.


Sector 7-8 – Navigation bar


Sector 7-8 – Inner Triplet L8 + DFBX


Temperature overview for each sector


Signal overviews for the Sectors

Pressures

He levels

Cold Mass temperatures

Line C temperatures


Sector 7-8 (arc)


Trends

• Predefined sets or operator defined• Possibility to select the trend of one parameter from overview or

synoptic plot


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?


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


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


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


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


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)



L. Tavian – LTC 2/6/2004F. Zimmermann – LTC 6/4/2005

per aperture

~600

~1300

~900

~2200



• 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


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


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.



• 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



• 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



• 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…


Tools needed

• Certainly we will need a summary of the Cryo Maintain/Start conditions for the different Sub-Sectors

• Available soonL. Serio


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


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.


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 lhc systems cryogenics….as seen by “beam handlers” g....

Documents

lhc commissioning wg

beam commissioning slide

lhc cryogenic components

lhc cryogenic system

lhc systems

signals slide

serio slide

hw commissioning ideal