"Linear Collider Tracker Alignment System R&D"

• Our ultimate goal is to design and build a real-time alignment system for a silicon tracker (barrel for an silicon detector concept and forward disks for any of the detector concepts). A system based on frequency scanned interferometry, developed by the Oxford group for ATLAS, promises to give the required resolution. Our immediate goal is to verify in the laboratory that we can obtain better than 1 micron absoluate accuracy on distances as large as 1 meter, under unfavorable environmental conditions (e.g., temperature fluctuations, air flow). We have achieved much better accuracy (< 100 nm) under controlled conditions. Once the required accuracy is demonstrated, our next goal will be miniaturization of the components for a prototype.

• We have verified with both air- and fiber-transport single-laser interferometers that we can obtain much better than required spatial resolution on absolute distance measurements under controlled laboratory conditions. But as expected, systematic errors interfere with single-laser measurement under realistic detector conditions. These recent results have been presented at linear collider workshops. Somewhat older results are published in Applied Optics.

• We are now investigating a dual-laser system with different frequency scan ranges that allows extraction of systematic biases of distance measurements. Preliminary results indicate degradation of precision from single-laser measurements under controlled conditions, but that the requireme of 1 micron resolution is likely achievable. Analysis methods to cope with occasional laser mode hopping and with optically chopped data are being optimized.

• The critical item for this year is verifying we can meet requirements on the bench with a dual-laser syatem. Following that in the coming years will be the R&D needed to miniaturize the system for detector prototyping. More funding will be necessary before prototyping can begin.

• Present funding is at a level that supports essential manpower and modest travel to give reports at workshops. A higher level of funding will be needed to go beyond the present benchtop testing with commercial components.

• 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?