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 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 K For T>30 K

LHC Commissioning WG, 22/05/2007 Instrumentation and signals Cryo Cell Standard Cell LT TT PT TT LT TT PT TT PT 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=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 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 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 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 2/6/2004 F. 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 report L. 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 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 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 ): The circuit of the LHC cryogenic system LHC-Q-ES-0003 (EDMS ): 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