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[Ext-GDE-95] CCB Response to ML Config Request of Oct.30, 2006 (CCR#20)
- Subject: [Ext-GDE-95] CCB Response to ML Config Request of Oct.30, 2006 (CCR#20)
- From: N.Toge <toge@xxxxxxxxxxxx>
- Date: Tue, 28 Nov 2006 09:18:53 +0900 (JST)
I am announcing that the CCB response, with regards to the ILC Config
Change Request for the ML section of Oct.30, 2006 (CCR#20),
is now posted at -
The change request was submitted by C.Adolphsen on Oct.30, 2006.
It seeks to to apply three changes in the ML design baseline:
CCR#20a: Change of the cryomodule (CM) layout driven by each of
the 10MW klystron RF unit. Previously, with two 8-cavity without
a magnet and one 8-cavity with a magnet (8-8-8).
Now, with two 9-cavity CM without a magnet and one 8-cavity with
a magnet (9-8-9). Thus, 26 cavities are driven by one 10MW klystron
rather than the previous 24. Consequently, the maximum achievable
accelerating gradient is 33.5MV/m rather than 35MV/m assuming use
of WR770 waveguides for improved RF transmission.
CCR#20b: Elimination of RF unit overhead. Previously, 3.5%.
Now, 0%. Thus, maximum beam energy 250GeV is available only if
all RF units are in operation and all CMs together with their cavities.
CCR#20c: Elimination of the uncertainty factor in the cryogenic static
heat load. Previously, 50%. Now, 0%. This allows to lower
the cryogenic capacity by 13%.
This CCR was initially classified as Class-2 and it was confirmed
as such at the CCB hearing that was held at Valencia on Nov.9, 2006,
whose minutes is available at
CCB reviewers were C.Pagani, W.Funk and S.Mishra.
The summary CCB response is as follows -
1. CCB found that the cost impact of the three changes CCR#20a,
b and c amounts to a total 5.2% reduction of the construction cost
of ML, including that of related conventional facilities.
If individually looked at, only CCR#20-b qualifies as Class-2
(CCR#20-a and CCR#20-c each belong to Class-1 category).
In the light of important implications and relative relationship
among three changes, however, CCB has decided to make recommendations
to EC for all of CCR#20-a, #20-b and #20-c, rather than to make
a final configuration change decision separately for #20a and #20c.
2. CCB recommends EC, on the basis of its review as detailed in the
"Discussion" session of the full report:
A. To not accept CCR#20a.
B. To not accept CCR#20b.
C. To not accept CCR#20c.
3. CCB finds that to proceed further on design development of ML
system, together with design development of other systems who rely
on the hardware equipment derived from ML, some clarifications in
the BCD text is urgently required in at least three areas. CCB recommends
D. To instruct relevant parties to resolve conflicting descriptions
of beam parameter specifications in the BCD.
E. To instruct relevant parties to introduce a place holder for
clear and unmistakable definition of the energy reach and luminosity
reach of ILC phase-1 in the BCD and to introduce descriptive entries
F. To instruct relevant parties to redraft a specification table as part
of BCD for the main linac RF unit, together with cavities and cryomodule,
on the basis of a firm consensus of all subgroups who are involved such
as: parameters, high-level RF, low-level RF, cavities, cryomodules,
cryogenics, commissioning, operation and availability. This specification
table has to allocate reasonable provisions for absorbing the current
technical ambiguities, has to be internally consistent, and has to be
consistent with respect to the definition of the "energy reach" above.
Full details of the evaluation of related issues, discussion and assessment
are available in the CCB report at the URI quoted above.
Additional communication and reference materials are available for
viewing, under CCR #20, at
With best regards,
- Nobu Toge (KEK, Accelerator Lab)