Cornell University Unit Name

"Vertex Detector Mechanical Support"

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INTRODUCTION

The silicon-based vertex detector is expected to be assembled at room temperature. Depending upon the sensor technology chosen, its operating temperature is expected to fall within one of two ranges: 0degC to room temperature or -80degC to 0degC. For either range, structures which support and position silicon sensors should ensure that sensor geometry, both within a sensor and among the full array of sensors, is reproducible to a precision of better than 5 µm from one cool-down to the next. When the vertex detector is at operating temperature, variations in sensor geometry should be negligible during any period of less than a month.

GOALS

Vertex detector sensors are expected to be arrayed in ladders within barrel sub-assemblies and wedges within disk sub-assemblies. For any ladder or wedge, the number of radiation lengths represented by material other than silicon and its readout should be less than 0.015% at normal incidence to the silicon surface. Over the range of possible incidence angles, additional support material to combine ladders into a barrel or wedges into a disk should add not more than 0.2% of a radiation length. Structures to support the combined assembly of one five-layer barrel and seven single-layer disks (per barrel end) should total not more than 0.1% of a radiation length at normal incidence and not more than 0.15% of a radiation length at the worst angle of incidence.

The material required for cables, cooling, and thermal insulation are expected to be dependent upon the sensor and readout technologies chosen and will be evaluated as part of the R&D.

During the first year of R&D, designs, materials, and procedures for fabricating ladders and wedges will be evaluated and tested, as will be those for fabricating, assembling, and supporting a barrel and a disk. Deliverables at the end of the first year will consist of the following:

• at least one prototype ladder
• at least one prototype wedge
• a design for the support structure of a barrel
• a design for the support structure of at least one disk
• analysis of deflections under gravity of an assembled barrel
• analysis of deflections under gravity of an assembled disk
• analysis of expected thermal distortions between room temperature and operating temperature for a ladder, a wedge, a barrel, and a disk
• proposed paths for cables and services for the vertex detector
• an analysis of weights and numbers of radiation lengths represented by those objects.

During the second year of R&D, designs will be iterated and measurements of design performance will be made. Deliverables at the end of the second year will consist of the following:

• measurements of ladder deformations between room temperature and operating temperature
• measurements of wedge deformations between room temperature and operating temperature
• a prototype support structure for a barrel
• a prototype support structure for a disk
• measurements of deformations between room temperature and operating temperature of the prototype barrel and disk.
• a design for the structure to support a barrel and all disks.

During the third year of R&D, designs will be completed and prototypes will be built of the remaining disks, thermal and cooling analyses will be completed for the two ranges of operating temperature, and a full prototype of the mechanical support structure for the vertex detector will be built. Deliverables for the third year will consist of:

• prototypes of all disks
• thermal and cooling analyses for each range of operating temperature
• at least one full mechanical prototype of the vertex detector
• an analysis of the weight and number of radiation lengths represented by the completed structure.

SUPPORT

The current level of support is inadequate for carrying out the proposed research. The level of shortfall is listed on the prioritization form.

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Please address the following questions in your statement.

• What are the goals of this R&D project. How does this R&D project address the needs of one or more of the detector concepts?

• If there are multiple institutions participating in this project, please describe the distribution of responsibilities.

• Are there significant recent results?

• What are the plans for the near future(about 1 year)? What are the plans on a time scale of 2 to 3 years?

• Are there critical items that must be addressed before significant results can be obtained from this project?

• Is the support for this project sufficient? Are there significant improvements that could be made with additional support?