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Gas system controls for LHC experiments. Outline. Introduction to the common gas system approach of the four experiments. Gas Control Project [soft+hardware] Prototypes of gas hardware and gas control systems Conclusions. Introduction.

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Gas system controls for LHC experiments

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Gas systemcontrols for LHC experiments

S. Haider / GWG


Introduction to the common gas system approach of the four experiments.

Gas Control Project [soft+hardware]

Prototypes of gas hardware and gas control systems


S. Haider / GWG


  • The Gas Working Group (GWG) was founded 1995 with the mandate of providing the four LHC experiments with scalable standard designs as far as possible and to bring forward proven and costed solutions.

  • In the CERN hierarchy, the GWG is based in EP - TA1 - Gas section (F.Hahn).

  • Each experiment is represented via a contact person. For ALICE Ray Gregory.

    • He brings all user requirements to the GWG

    • he organizes meetings between GWG and sub-detector experts

    • he organizes the collection of all relevant data for the TDR

S. Haider / GWG

  • Working philosophy of GWG

    • meet the sub-detector experts and capture as many requirements as possible

    • propose a gas system layout with an initial cost estimate

    • re-iterate (several times if necessary) with experts and write the Technical Design Report

    • repeat the exercise after some time with much more depth and proceed to Engineering Design Report.

S. Haider / GWG


TDR: Technical Design Report

EDR: Engineering Design Report

S. Haider / GWG

  • Advantages of a common approach for ALICE

    • With the large similarities of the gas hardware and software design, one saves enormously resources:

      • by lack of duplication,

      • by standardized construction and implementation procedures,

      • and most importantly bylong-term maintainability of ALL gas systems at LHC.

    • Due to the larger amount of equipment that has to be ordered, manufacturers often agree to substantial price reductions which, overall, brings the total costs of all gas system down.

S. Haider / GWG

Gas Controls

  • Gas control will be handled by the GWG since detector security crucially depends on smooth interaction between gas hardware and control software.

  • The GWG fully complies to the Joint COntrol Project (JCOP) of the four LHC experiment, in particular to the:

    • basic idea of ONE common SCADA product,

    • the working philosophy of User Requirement Document (URD) before writing code

    • and the so-called “Framework”, which provides similar control philosophies throughout the LHC experiments.

S. Haider / GWG

  • The GWG has finished the first URD analysis in collaboration with IT/CO. Version 1.0 available. The final version will include also the Human Machine Interface (panels etc..)

  • this URD follows the industrial software production standard PSS05 (ESA)

    • split the gas systems in functional modules: mixer, purifier, pump, distribution etc..

    • Capture as many functional requirements as possible: States, commands, interlocks, events, alarms, messages etc..

S. Haider / GWG

Software development

User Requirement Document

Engineering Phase

Implementation phase

Testing phase

Commissioning Phase

S. Haider / GWG

Software development (cont.)

  • Reuse a Software Library from the LHC Cryogenics Group, the UNICOSlibrary:

    • cryogenics has VERY similar requirements towards equipment:

      • ie. Analog and On/Off valves

      • PID loop controllers

      • flow meters and pressure transmitters

      • etc...

    • We can use this library free of charge (costs the cryo group some 2-3 Man-years of software development)

    • First used for NA60 Gas system (later more).

S. Haider / GWG

Control Hardware Architecture

ALICE gas systems







TRD TOP gas control







Rack 1

Rack 2


Rack 10




Gas equipment


S. Haider / GWG

Parameters for rack #10 (i.e.)

Input pressure: HIHI=+10mbar

HI = +9 mbar

LO = +4 mbar

LOLO = +3 mbar

Output pressure: HIHI = +5mbar

HI = +4 mbar

LO = +0.5 mbar

LOLO = -0.5 mbar

Leakrate measurement: HIHI = 20%

output - input flow HI = 18%

Pressure regulation : setpoint = +3.5 mbar

PID parameter : P = 300

I = 0.12

D = 0.0



Buttons on screen:

RUN state:

Upload Recipe

Make Recipe def.

Change Recipe

Save Recipe

Load Recipe

Download Recipe

The parameter list in a

module is

called “Recipe” !!

S. Haider / GWG


  • Distribution prototype for closed loop systems with several distribution racks

  • ALICE CPC mixer with digital mass flow controllers (FlowBUS from Bronkhorst)

  • LHCb 2 mixer stations with digital MFCs on ProfiBUS


  • CMS MSGC, CSC...

S. Haider / GWG

NA60 Gas system

  • Final control hardware and software:

    • Schneider PLC used

    • PLC program utilizes the UNICOS library

    • Mixer URD used to produce PLC program.

    • 3 gasses and 1 liquid are mixed. Mixture is flammable

    • distribution rack features:

      • final gas distribution manifold with integrated needle valve, flow-meter and quick-connector for each channel

      • input and output flows are measured.

      • Flow-meters are read by micro-PLC from Wago

S. Haider / GWG


  • The analysis of the gas systems for LHC experiments has shown that a common approach is possible

  • The first step of the software development cycle, the User Requirement Document, is finished. First version is available.

  • With NA60 we have gone through the entire development cycle and produced a full gas control system for a mixer and a distribution system. The final control hardware and the PSS05 software production standard were tested and gave adequate results in view of the production of the LHC gas systems.

S. Haider / GWG

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