The BCD Executive Committee met Nov 17-18 and reviewed all the inputs from the working groups, the reviews of those reports and a set of special white papers on critical issues. As a result, we have established a "Strawman" Baseline to serve as the basis of discussions at the Frascati GDE meeting, where we will determine the Baseline in the Baseline Configuration Document (BCD).
The Strawman BCD can be found at -
http://www.linearcollider.org/wiki/doku.php?id=bcd:bcd_home
This document will continue to evolve, in order to fix inconsistencies, add details, etc between now and the Frascati GDE meeting, but the main features of the baseline will not change. We now encourage all in the GDE and ILC community to study the BCD prior to the Frascati meeting. We will go over it, discuss proposed changes and finalize it at that meeting. The BCD will then be put under "configuration control" and will be the basis of the reference design effort next year.
I highlight below a few key features of the Strawman BCD that emerged from last weeks BCD Executive Committee meeting -
- The BCD Executive Committee has agreed to accept the recommendations outlined in the recent GDE task force White Paper on the location of the undulator-positron source. The undulator source will be placed at the 150 GeV point in main electron linac. This will allow constant charge operation across the foreseen centre-of-mass energy operating range.
- The Damping Ring working group met at CERN last week and came to consensus on a recommendation for one 6km ring for the electrons and 2x6km stacked rings for the positrons, with a strong recommendation for more R&D on electron cloud effects. The dogbone configuration was recommended as alternative.
- On the issue of laser-straight versus continuously curved or kinked configurations, the conclusion is to adopt a continuously curved linac (BDS laser-straight) unless a site constraint dictates otherwise on cost grounds.
- The baseline is for 2 IRs, but a full costed study of 1 IR is recommended for next year.
- The baseline is for two tunnels.
- The baseline (500 GeV centre-of-mass) will use a tunnel long enough to support a gradient of 31.5 MV/m operational gradient (~2x10km assumning a 0.75 fill factor). A future upgrade to 1 TeV will then require extending the tunnel (away from the IR) an additional ~2x9.3km assuming cavities capable of 36 MV/m operational gradient. The baseline Beam Delivery System and main dump systems will be configured for the 1 TeV option and prospective sites must be chosen with capability to upgrade to ~ 1TeV