Clash detection

As DUNE progresses from working groups into consortia responsible for the design and construction of actual detector elements — consortia that are distributed around the globe — how does the project verify that the detector elements will fit together in the cryostats and that the detector modules will work within the design and constraints of the conventional facilities that support the experiment?

The answer is a set of integrated 3D models. A workshop at Fermilab in late February brought together the systems engineering team and scientists and engineers working on designs to discuss how to achieve this goal.

Integrated model of the EHN1 facility for the ProtoDUNE detectors at CERN. 3D modeling and integration done in Catia by CERN team.

Already groups in the U.S. and Europe are constructing ProtoDUNE elements, based on engineering models that each group has developed, and that are integrated at CERN as part of its host role for the Neutrino Platform. LBNF and DUNE teams are sharing their models, and CAD specialists on both continents are using them to create 3D models of integrated pieces that are used to coordinate the designs, plan construction and installation sequences, and check for clashes. Building upon that experience, the workshop brought up many issues to consider as the project develops a LBNF/DUNE-wide process to integrate the separate CAD models. It will be important to provide updated versions at regular intervals in a common format and in a shared repository such that all DUNE and LBNF scientists and engineers can access them. This should allow detection of any clashes and resolution of issues before designs are final.

Integration is a complicated business. Different teams use different software packages, and create files of proprietary types. For example, PSL in Wisconsin integrates the single-phase TPC designs in SolidWorks, and Argonne has designed the CPAs using Inventor. CERN, which has been designing the facility for the ProtoDUNEs, the EHN1 infrastructure and the cryostats and cryogenics systems, uses the Catia design package. Fortunately, the files can be converted to STP files, a format that all the packages can read in.

(Top) Integrated NX Assembly of Far-Site Campus, consisting of models from Revit, AutoCAD, CATIA, and other sources – managed in Teamcenter. (Bottom) Detailed View of Chamber One, showing Cryostat from CERN. Images Courtesy of Fermilab.

To keep file sizes manageable, much detail is stripped off during the integration process such that components appear with their exterior size and shape (their “envelope”), and interface points, but without internals.

The LBNF/DUNE-wide CAD integration process will allow each group to use its preferred software for their contribution. It will set out procedures for the flow of output from one step of the integration to the next, what file types must be made available, what level of detail they contain, where the final integration takes place, how often a full integration will be performed, and where the integrated model files get stored. A free viewer called Navisworks Freedom will allow people to view the files.

“It is really important that people use the most recent information,” said Elaine McCluskey, LBNF project manager. “We also need to make sure that we provide the right level of detail for people and a way for them to easily view the models. We know what the issues are now, so we can address them.”