Dear Colleagues,

We expect the close-out session of the CR002 change request (to adopt a single L* configuration for both detectors) at the ALCW2015 workshop in KEK next week. As part of the close-out we need a short report from the BDS group justifying an optics configuration for the L* setting (both written and oral). Based upon the multiple studies from Okugi-san and Edu over the past months, I have collected some results (mainly from the BDS WG meeting yesterday) and made some conclusions which I hope reflect the opinions of all concerned. Please see the preliminary report for the optics session attached. I have made the request for QD0 L*=4.1m and QF1 L*=9.5m. In the end, I chose to specifically request 9.5m for the QF1 L* based on the negligible impact of lowering this to 9.1m for the luminosity estimate based on preferred TDR tolerances shown by Okugi-san last night and the better collimation performance around 9.5m and taking into consideration the concerns of the detector groups for moving QF1 closer to the IP. I did however make a point to indicate that a shorted QF1 is highly desirable.
Please have a look at the text and let me know if you disagree with any of the conclusions or wish to include any further comments etc. The aim is to close out this topic next week.

Best regards,

- Glen.


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