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Date: Tue, 19 Sep 2006 08:46:04 +0900 (JST)
To: ml-ccb@xxxxxxxxxxxx, ml-ext-gde@xxxxxxxxxxxx
From: "N.Toge" <toge@xxxxxxxxxxxx>
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Subject: [Ext-GDE-64] CCB Response DR (single e+ ring) Change Config
Request of Aug.4,
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I am announcing that the CCB response, with regards to the latest
Change Request for the Damping Ring section, is now posted at -
The change request was submitted by A.Wolski on Aug.4, 2006.
It relates to reconfiguration of the two-DR layout on the
positron side. The proposal is to revise the baseline of the
positron DR to consist of one ring, given the promising prospects
for resolving the electron cloud instability issues with
introduction of grooved vacuum chambers and/or clearing electrodes.
Provisions for building two positron DRs, however, are to be
The requester suggested Class 2 for this request, to which
CCB concurred after evaluation of the cost impact.
CCB gratefully acknowledges the detailed assessment reports offered
by colleagues from the the DR Area Group and the GDE Cost Engineering
The summary CCB response is as follows -
1. CCB agrees that the cost change (in this case, reduction) expected
from this change request is substantial, such that it qualifies as
Class-2. Consequently, CCB assumes that its role concerning this
change request is to assess its merits and make a recommendation to
EC, rather than to make a final configuration change decision.
2. CCB recommends EC to adopt this change request as is, for reasons
detailed below in the Discussion section in the PDF document that
is available at the URI above.
3. CCB will encourage the relevant parties, and will work with them, to
update the "Parameters and Layout" section of BCD in accordance with
the updated damping ring population.
4. CCB notes the need for conducting systematic R&D associated with
the vacuum chamber system, simulation and validation of all mitigation
techniques for electron cloud effects. CCB recognizes that the GDE R&D
board is currently in the process of evaluating, organizing and
these research programs. CCB recommends that the GDE Executive Committee
create an effective review process by which the progress of such
be evaluated so as to re-confirm the adequacy of the baseline design at
appropriate intervals. This applies equally to other design development
issues with the damping ring baseline, such as the 650MHz RF and fast
kickers, as well as to other systems such as high-gradient SRF cavities
or extraction magnets in the beam delivery sections.
Additional communication and reference materials are available for
viewing, under CCR #15, at
When GDE EC makes the final decision and approves this change request,
CCB will update the DR section under
With best regards,
- Nobu Toge (KEK, Accelerator Lab)