Mechanics: Status and Plans Bill Cooper (Fermilab) (Layer 1) VXD

Bill Cooper Track-trigger Meeting – 15 September Considerations and Status Overall layout –Developed last spring –Existence proof for a reasonable track-trigger geometry –Provides guidance on module dimensions, module mechanical infrastructure, arrangement of stacks, cooling, and rod lengths Module mechanical design –We are waiting for guidance from prototype submissions and input on interposer design parameters. Module and rod assembly –Aimed at allowing parallel fabrication at multiple locations. –Allows decoupling of R&D on single-stacks, double-stacks, services, rods, and rod support. Support disks for rod arrays –Concept specific, so R&D on this has been deferred. Cooling –Evaporative CO2 cooling is assumed. Analysis and prototyping –Given CMS and Fermilab approval, we can start on finite element analysis and prototyping in a few weeks. Guidance we received and have followed –Concentrate R&D on aspects which relate to a local track-trigger, that is, on sensor modules and services. –Defer R&D on overall geometry and support, which tend to assume a particular scheme for implementing a track-trigger. –Defer R&D on cooling systems, which will be developed by others.

Bill Cooper3 Overall Layout The overall R-Z layout from last January is shown below. Maximum rod length is about 2.77 m for sensors of cut length 98 mm. The suggestion has been to limit rod prototypes to about 1 m. –I would prefer not to leave prototyping of full-length rods too late –Measurements of prototypes would confirm that deflections related to ply angles of the carbon fiber laminate agree with predictions and ply angles are appropriate for the finite element thermal analyses. R-Z view Track-trigger Meeting – 15 September 2009

Bill Cooper4 R -  Layout Existence proof for one concept of a track-trigger All five layers of the left side are shown below. Central radii of silicon range from 278 to 1126 mm for the left side. –Radii for the right side are 6 to 9 mm smaller. The number of  locations is an even multiple of 8 for each layer (both sides identical). Track-trigger Meeting – 15 September 2009

Bill Cooper5 Z = 0 Overlap One possibility for overlaps in layers 1, 2, and 5 is shown. In this case, carbon fiber support structures of rods of the two sides are aligned transversely and notched back to allow overlap of sensors and interposers. Longitudinal clearance ~ 2 mm. Transverse clearance ~ 3 mm, but the clearance needed will be determined by rod deflections as they are installed and rod installation tooling. Track-trigger Meeting – 15 September 2009

Bill Cooper Track-trigger Meeting – 15 September Finite Element Analysis (FEA) Requisites –Effective thermal conductivities and dimensions of interposer materials –Power dissipation and locations at which power is dissipated –Working assumptions of rod dimensions –Locations and dimensions of material layers which thermally insulate –Selection of carbon fiber pre-preg for support structures and determination of the laminate thickness and fiber direction within each laminate layer Given that information and the assumption that the temperature of a cooling tube surface is uniform, FEA should be straight-forward. –Heat flux from the surrounding air would be ignored during the first pass and early iterations. At least one FEA expert at Fermilab could begin work roughly a week after the effort is approved by CMS and Fermilab. Cooling tube sizing –The surface area of a cooling tube determines its effectiveness as a heat sink, thereby indirectly constraining the minimum tube size. –The heat flux, wall thickness, and coolant properties determine the validity of the assumption of a uniform wall temperature. –Coolant flow rate, heat input over the cooling tube length, and allowed coolant pressure drop impose additional constraints on the cooling tube size. We should anticipate that the FEA will be iterative in order to take into account improved knowledge of heat sources, material thicknesses, laminate ply directions, cooling system requirements, and rod geometry. –Perhaps 0.5 FTE x 6 weeks for the first pass, 0.5 FTE x 4 weeks for subsequent iterations, depending on the extent of changes

Bill Cooper Track-trigger Meeting – 15 September Proposed Plan for Thermal FEA Proposed initial assumptions: –Assumptions are based upon dimensions developed in spring –A continuous interposer (no openings to reduce mass) with silicon thermal-mechanical properties Openings can be added to the FEA when their locations and shapes are known. Thermal FEA may set limits on the numbers and sizes of openings, and features needed to augment heat conduction with openings. –Interposer dimensions = mm x 96.5 mm x 1 mm –Sensor dimensions = 98 mm x 98 mm x 0.3 mm –Uniform power dissipation of 4.5x10 -4 W/mm 2 over the full extent of each sensor Details of power sources and their locations can be added when they are known. –Rod box structure outer transverse dimensions of approximately 41.5 mm wide x 40.4 mm tall –K13C2U carbon fiber pre-preg for support structures –Ply directions as suggested last spring: quasi-isotropic in modules, favoring the longitudinal direction in rods –Stainless steel cooling tubes with OD = 2 mm, ID = 1.3 mm –Carbon fiber laminate sheathes to position and hold cooling tubes –Locations and dimensions of material layers which thermally insulate need to be known early.

Bill Cooper8 A Reminder of the Rod Mechanical Fabrication Sequence Each piece needs to be prototyped and tested. The assembly needs to be prototyped and tested at each stage. Track-trigger Meeting – 15 September 2009

Bill Cooper Track-trigger Meeting – 15 September Prototyping Goals –Structures which allow: Realistic geometries to be developed for interposers, modules, and rods Measurements of heat flow, shielding and grounding, rod precision, and rod stiffness Requisites for rod and module prototyping –Selection of carbon fiber –Mandrels –Engineering and drafting support –Technicians and an autoclave or equivalent to fabricate CF parts –Tooling, technicians, and access to a CMM for assembly and testing –Cooling tube sizing Carbon fiber –We have enough K13C2U fiber for a few module prototypes, but will need to purchase fiber for larger structures. –K13C2U fiber cost has varied with time. –Typically $1500 per pound with a minimum, cost-effective order of about 15 pounds –Past deliveries have taken 4 to 6 weeks, but delivery times as long as 12 to 16 weeks cannot be excluded. Mandrels –We have often used aluminum for first pass mandrels and then switched to carbon steel for later prototyping and production. –Mandrel and tooling design and fabrication efforts could be shared with universities that have engineering resources and good access to machine shops.

Bill Cooper Track-trigger Meeting – 15 September A Few Prototyping Details Mechanical support structures have been intentionally kept simple. It may be possible to fabricate initial prototype modules with minimal fixturing. –Basic requirements: Module surfaces should be flat and parallel. Material thicknesses should be adequately controlled. Voids in adhesive layers should be minimized. Transverse alignment should be well-controlled. –Flat sheets of carbon fiber laminate should be straight-forward. –Depending on the required features, at least two methods are available to make module pieces from sheets: Shearing Cutting on a CNC machine such as one of the Thermwoods in Lab 8 –Interconnections and cables may complicate fabrication. –Long term, automation should be considered and module fixturing consistent with the required precision and through-put should be developed. Tooling for rod components –We have typically utilized internal mandrels for shapes of comparable transverse dimensions. That should be fine for early prototypes. –However, external mandrels should produce smoother and flatter surfaces on which modules would be mounted. Developing external mandrels and procedures for carbon fiber laminates will take R&D. –We will need to understand mandrel stiffness and support. –We will need to understand cable and access openings and how to cut openings in the rod “boxes”.

Bill Cooper Track-trigger Meeting – 15 September A Few Prototyping Details The equivalent of an autoclave can be fabricated from tubing or pipe plus end- closure heads. –Heat tape with a controller can provide an adequate temperature versus time profile. –Through-put from a given mandrel set is limited by the temperature cycle of the laminate cure, which takes up to five hours. Production fabrication would benefit if it were distributed over multiple locations. –Prototyping provides an opportunity to develop expertise at multiple locations. –We have not discussed it, but I suggest that the University of Rochester, other interested institutions, and Fermilab work together to develop mandrels, autoclave equivalents, and other fabrication and assembly tooling. Until the transition to experiment-specific designs, we may want to defer work on support disks and their prototyping. Temperature distribution studies would be aided by an evaporative, CO2 cooling system. –Development of a closed-loop system at Fermilab had been planned, but has been delayed. –We may need to use an open-loop system for testing of prototypes, though a closed- loop system should provide better temperature stability.

Bill Cooper Track-trigger Meeting – 15 September In Summary We are prepared to assist with interposer and module mechanics. We would begin finite element analyses and prototyping as soon as the effort is approved. Distributing the effort among CMS institutions would allow expertise to be developed in specific fabrication techniques and help ensure that good facilities will be available for production.