Kuroda introduced the differences of BDS between "COLD" and "WARM" machines by referring Yokoya's talk at the SC-LC study meeting (Japanese), KEK, 6th September 2004. The major differences are (1) optics of collimator and final focus system where "WARM" is better-conceived (Yokoya), (2) machine protection system (MPS) due to the beam properties, (3) crossing angle which has been reviewed at the previous meeting, and (4) IP feedback which is indispensable for stable collisions however with slower time response than FEATHER/FONT .
Also the beam/optics parameters are different at IP for longer bunch length of &sigmaz=300μm and higher beam intensity of 2.0 x 1010/bunch. They are; &betax (y)=15 (0.4)mm, &sigmax (y)=554 (5.0) nm, and &epsilonx (y)=10 (0.3) x 10-6m rad. In particular, larger &epsilonx may increase geometric aberration at sextupole magnets in the final doublets. This value is limited at the 5GeV damping ring of TESLA-TDR.
(2) MDI issues (T. Tauchi)
(transparencies, 14 pages, pdf, 730KB)
Tauchi briefly reviewed the MDI issues, which has been presented at Huge Detector Concept Study Meeting, TV, 15 September.
MDI is Machine Detector Interface, where the relevant machine is beam delivery system (BDS) from LINAC-end to beam dump and the detector is located at interaction region (IR). The BDS consists of collimation, energy/polarization (E/P) measurements, final focus, extraction and beam dump. Sometimes, the extraction is separately studied in the BDS. Design of IR must be optimized in terms of luminosity, background and minimum veto-angle from the viewpoint of experiments on physics of Higgs, top, W/X, SUSY, extra-D etc. . Major task of MDI is to compile requirements from the experimental side in order to communicate the accelerator physicists for designing the BDS.
Relevant major issues for the requirements in each system can be listed in a following table;
|BDS||crossing angle||backgrounds; muons,synchrotron &gamma|
|2 IPs for 2 "identical experiments"|
|precise E/P mesurements|
|IR||L*: distance of QC1 from IP||min. veto angle: very forward calorimeter|
|precise luminosity (L) measurement|
|backgrounds; pairs,mini-jets, back-scattered γ, n|
|intrumentations; pair/Shintake monitors,feedback etc.|
|Extraction||crossing angle||backgrounds; disrupted beam,back-scattered γ, n|
|choice of final Q (L*)|
|precise E/P mesurements|
Our current/past activities on the MDI-related issues are listed in a home page of http://acfahep.kek.jp/subg/ir/minutes/future.effort.html . Particularly, three R&Ds of FEATHER, nano-BPM and Laserwire will be internationalized beyond Asian region, which are executing at the ATF extraction beam line.
There is a plan of MDI mini-workshop which was first discussed at the LCWS2004. At the mini-workshop, we would like to discuss on future direction of MDI R&D after the "COLD" decision. The possible date is January 2005 which is still under discussion among the MDI conveners of three regions and the LC-WWS co-chairs. Since the first ILC (International Linear Collider) workshop will be held on 13-15 November 2004, at KEK, we can meet there for discussion/communication. Also, a phone meeting is scheduled on 6 October, 2pm (Japanese time) for preparation of the mini-workshop. We would like to discuss these issues at the 7th ACFA-LC workshop, 9-12 November, Taipei .