Integrating the large and complex LHC machine into the existing LEP tunnel is a major challenge. Space was not really a problem to fit the LEP machine into its tunnel, but LHC cryostats are much larger than the LEP quadrupoles and the external cryogenic line fills even more the tunnel. Space problems lead to small clearances. Possible conflicts, or at least the most penalising ones, between installed equipment or with transport, must be solved beforehand in order to avoid unacceptable delays and extra costs during the installation. Experience gained with LEP has already shown the help that Computer-Aided Engineering tools could provide for the integration. A virtual model of the LHC is presently prepared. The actual LEP tunnel, known with a quite good accuracy (centimetre level), has been modelled and all the elements of the machine constructed as 3D objects with the CAD system are positioned accurately on the basis of data generated from the theoretical definition. These layouts are used to generate the reference sections and to check the clearances. Examples of this powerful approach applied to engineering for accelerators are given

Chemli, S

Hauviller, Claude

Messerli, R

Muttoni, Y

Prin, H

Van Uytvinck, E

CERN Document Server

EUROPEAN ORGANIZATION FOR NUCLEAR RESEARCHEuropean Laboratory for Particle PhysicsA VIRTUAL CAD MODEL OF THE LHCS. Chemli1, C. Hauviller1, R. Messerli1, Y. Muttoni1, H. Prin2 and E. Van Uytvinck1Integrating the large and complex LHC machine into the existing LEP tunnel is a major challenge.Space was not really a problem to fit the LEP machine into its tunnel, but LHC cryostats are much largerthan the LEP quadrupoles and the external cryogenic line fills even more the tunnel. Space problemslead to small clearances. Possible conflicts, or at least the most penalising ones, between installedequipment or with transport, must be solved beforehand in order to avoid unacceptable delays and extracosts during the installation. Experience gained with LEP has already shown the help thatComputer-Aided Engineering tools could provide for the integration.A virtual model of the LHC is presently prepared. The actual LEP tunnel, known with a quite goodaccuracy (centimetre level), has been modelled and all the elements of the machine constructed as 3Dobjects with the CAD system are positioned accurately on the basis of data generated from thetheoretical definition. These layouts are used to generate the reference sections and to check theclearances.Examples of this powerful approach applied to engineering for accelerators are given.1 CERN, LHC Division, Geneva, Switzerland2 Kraftanlagen Nukleartechnik GmbH, Heidelberg, GermanyPresented at the Seventh European Particle Accelerator Conference  (EPAC 2000)26-30 June 2000, Vienna, AustriaGeneva, Large Hadron Collider ProjectAdministrative SecretariatLHC DivisionCERNCH - 1211 Geneva 23SwitzerlandLHC Project Report 414Abstract23 September 2000A VIRTUAL CAD MODEL OF THE LHCS. Chemli, C. Hauviller, R. Messerli, Y. Muttoni, H. Prin*, E. Van UytvinckCERN, Geneva, Switzerland*Kraftanlagen Nukleartechnik GmbH, Heidelberg, GermanyAbstractIntegrating the large and complex LHC machine intothe existing LEP tunnel is a major challenge. Space wasnot really a problem to fit the LEP machine into itstunnel, but LHC cryostats are much larger than the LEPquadrupoles and the external cryogenic line fills evenmore the tunnel. Space problems lead to small clearances.Possible conflicts, or at least the most penalising ones,between installed equipment or with transport, must besolved beforehand in order to avoid unacceptable delaysand extra costs during the installation. Experience gainedwith LEP has already shown the help that Computer-Aided Engineering tools could provide for theintegration.A virtual model of the LHC is presently prepared. Theactual LEP tunnel, known with a quite good accuracy(centimetre level), has been modelled and all the elementsof the machine constructed as 3D objects with the CADsystem are positioned accurately on the basis of datagenerated from the theoretical definition. These layoutsare used to generate the reference sections and to checkthe clearances.Examples of this powerful approach applied toengineering for accelerators are given.1  INTRODUCTIONBuilding the LHC and all its high-technology elementsis a challenge, but integrating the LHC machine in theexisting LEP tunnel will also be a challenge. Thedifficulties are due to dimensional problems of two types:x the machine is very long (27 km) and the preciselongitudinal positioning of the numerous elementsis a must;x the transverse dimensions of the machine and itsservices must fit into the tunnel.The thousands of magnetic elements are housed inlarge cryostats, which look like 15 m long tubes, 1 m indiameter, assembled together. The external cryogenicline, a 0.6 m diameter tube with a lot of protuberances,also occupies a fair amount of space. What is left in thetunnel section is occupied by a lot of services: water andhelium tubes, cable trays, pumps, racks, transport system,and a possible future electron machine to be installedabove the LHC.Even if it was a challenge to integrate the LEP machinein its tunnel, the quadrupoles being the widest elementswith a transverse section of about 0.7 m2, the LHCcryostats and its cryogenic line occupy four times moretransverse space.If space inside the tunnel is a problem, clearancesbecome a major concern, especially since the tunnelaccuracy is not at the same level as the mechanical parts:it is a very large civil engineering work with centimetreand even decimetre offsets.Experience gained with LEP [1] has already shown thehelp that Computer-Aided Engineering (CAE) tools couldprovide for the integration. LHC integration is morecomplex and use of CAE tools is then heavily required.This paper presents the tools, which have beendeveloped in the two dimensional domain, mainly for thelongitudinal positioning of elements, and in three-dimensional domain, the Digital Mock-Up (DMU) of theLHC. Results achieved so far are outlined together withthe work underway in the framework of Computer AidedDesign (CAD) and Engineering Data ManagementSystem (EDMS).2  2D SCHEMATIC LAYOUT The basic approach in the two dimensional domain arethe 2D schematic layouts. These layouts show thelongitudinal arrangement of the magnets and otherequipment in the LHC tunnel. Three types of schematiclayouts have been developed: general, conceptual andmechanical, depending on the level of detail. The general schematic layout shows only the magneticlengths of the main magnets (dipoles and quadrupoles)and their operating temperatures. The various correctorfamilies and the beam instrumentation are added in theconceptual layout that reflects the machine optics asgenerated from the accelerator design package MAD1.These two types of layout present the LHC from an opticspoint of view, and allow rapid finding of all opticelements in any given area of the machine. The operating parameters of the magnets (magneticlengths and position of their centres) and the mechanicalparameters of cryogenic assemblies are shown to scale inthe mechanical layout. The mechanical references for thecryo-assemblies are the virtual interconnection planes(VIP, drawn in 2D by a line perpendicular to the beamaxis) and the fixed support post of the cold mass. Thedescription of cryogenic assemblies is given in an                                                          1 Computer package developed at CERNAutoCAD library and is stored in an Oracle database(Fig. 1).Figure 1: An element and its parameters The “s” co-ordinate (cumulative magnetic length) of itsVIP gives the position of each assembly in the machinefrom the machine origin (Interaction Point 1). Thesequence of VIPs thus defined is stored in the database,and a cryogenic assembly from the library associated toevery entry. This set of data links the description of thecryogenic assemblies to the magnet parameters, whichmakes possible an automatic generation of the MADinput. A navigation interface (Fig. 2) is available on the Webfor viewing the layout. For easier viewing, the machine issplit into three main areas: arcs, dispersion suppressorsand long straight sections, and in half-cells. To ensure thevalidity of the information given in the navigator, thedrawings archived in the CERN Drawing Directory1(CDD) are transformed in a format suitable for the Web.Figure 2: 2D Web Navigation Interface 3  CONTEXTUAL 3D DESIGN ANDRELATED PROBLEMS The contextual design of a collider such as the LHCconsists in the integration, in a given environment, of 3Dmock-ups. Those virtual objects (surface buildings,underground tunnels, caves, LHC accelerator equipmentsand large detectors) are modelled as close to the reality aspossible using the EUCLID package. Such a DigitalMock-Up is essential in order to minimise the cost impactof the modifications in the construction, installation andexploitation phases of the LHC project. As most of the 3D elements exist in the design officesdatabases, building a DMU of the LHC machine using the2D schematic layout could be considered as a Lego game.This is not the case. Several factors are required toachieve a good DMU. The clearance between the elements is a lot tighter forLHC than it was for LEP. Therefore, majorsimplifications introduced in LEP 3D toolbox areunacceptable for LHC. Quite complex aspects have also to be considered:x the tunnel does not respect the accuracy initiallyexpected;x the machine is curved and tilted;x the vertical direction changes along the tunnelbecause of the accelerator plane slope and becauseof earth curvature.As a matter of fact, integration will put together themodels coming from all involved corporations. Designershave their own methodology of creating the equipmentsor the elements that will be assembled in the machine.This methodology is adapted to the element they areconsidering during the design process. They do notalways keep the same referential from one designed partto another, for a better comfort (the LHC is tilted but allthe elements are drawn with a vertical Z co-ordinate) anda higher accuracy (integration of small elements far fromthe CAD origin may generate strange algorithmic andtopological results). To achieve the integration, it is thennecessary to compute the position of the element in aunique co-ordinate system covering the whole CERNarea.It is clear that our virtual prototyping project has tocope with the following complex fields:x LHC accelerator systems database of equipmentpositions;x very large modelling (many equipments andbuildings);x geodetic calculations;x high precision calculation of components positionsin more than hundred co-ordinates systems;x measurements of the as built LEP tunnels. 4  MODELS COLLECTION ANDINTEGRATIONThe LHC DMU is made of two parts. The periodic partconsisting of the "standard" tunnel sections and therepetitive cells of the machine, automatically generated.The non-periodic one, typically the surface buildings andthe various experimental and ring caves, manuallyintegrated.4.1  Automatic integrationThe LHC DMU will dynamically be generated as muchas possible from a set of models provided by the designoffices (3D standards under change control), the Surveydatabases, the EDMS and the 2D layout.The main tunnel has been measured and a dedicatedapplication has been developed to build automatically anyarea of the tunnel from the measurements.Other tunnels can be a few kilometres long and quitedifficult to model because of their changing orientationcombined with the variation of the vertical direction.Specific developments are needed.The machine elements are generated and locatedlongitudinally with the 2D schematic layouts andpositioned in the 3D space using the Survey co-ordinatesdatabase. Periodic or semi-periodic systems, which can belocated in a digital manner, will be generated alsoautomatically.4.2  Manual integrationAll activity sectors are concerned by this DMU: civilengineering, handling, transport, piping, cable trays, etc.Each field of work acts first sequentially to find the besttrajectory of a pipe line or a cable tray and then iterativelyin order to solve the interferences detected betweencryogenic equipments, electrical boxes, etc. This processproceeds from the largest equipment to the smallest ones.The LHC domain is covered by a unique co-ordinatesystem. This domain is split in geographical zones withtheir local referential in such a way that co-ordinatesinside a zone does not exceed one kilometre.The models are stored in this local referential.Nevertheless, each area has also a set of secondary co-ordinate systems aimed to ease the modelling phase. Eachdesigner has to clearly identify the system that he uses.This information gathered at the time the models arereleased, allows the CAD system to store data in the localreferential of the zone. This process is kept under thecontrol of an approval tool (CDD).4.3  Some examplesFigure 3 shows an example of the LHC DMU with allthe elements integrated inside the actual standard tunnel.This DMU is used by the engineers, but also with the helpof ROBCAD/DYNAMO package, to detect theinterferences between elements or to study installationand transport sequences.Figure 3: The LHC machine integrated into its tunnel - Partial view of a standard zone 5  CONCLUSIONCAE tools are extensively used to understand and easethe integration work of the LHC machine and the relatedservices. The 2D layouts are accessed on a daily basis bymost of the collaborators. The 3D Digital Mock-Up isunder development but already used to solve trickyengineering problems.ACKNOWLEDGMENTSThe authors would like to thank J-P. Quesnel and hisSurvey team for providing measurements and alignmentdatabases and F. Soriano for the artistic contributions.REFERENCES[1] G. Bachy, C. Hauviller, R. Messerli, M. Mottier,"Computer-Aided Engineering in High EnergyPhysics", 1988 European Particle AcceleratorConference, Rome, June 1988.

A Virtual CAD Model of the LHC

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