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[Ext-GDE-101] CCB Response to PES Change Request - Nov.17, 2006 (CCR#22)
- Subject: [Ext-GDE-101] CCB Response to PES Change Request - Nov.17, 2006 (CCR#22)
- From: N.Toge <toge@xxxxxxxxxxxx>
- Date: Fri, 01 Dec 2006 23:50:54 +0900 (JST)
I am announcing that the CCB response, with regards to the ILC Config
Change Request for the Polarized Electron Source (PES) section of
Nov. 16, 2006 (CCR#22, http://lcdev.kek.jp/ML/PubCCB/msg00110.html)
is now posted as
The change request was submitted by A.Brachmann on Nov.16, 2006.
Request was treated as Class-1. N.Toge and M. Kuriki were assigned as
the CCB reviewers.
The CCR#22a proposed the following four revisions:
CCR#22a: Eliminate second (backup/redundant) normal conducting beam
CCR#22b: Eliminate cavern for laser system; locate laser system in
above ground building and addition of a small diameter shaft
(d = 1.5 m) for laser beam transport.
CCR#22c: Modification of "dogleg" section of beamline - Replace
with vertical chicane.
CCR#22d: Replace 2 L-band bunchers and NC pre-accelerator with combined
TW tapered L-band bunching and pre-acceleration section.
The main motivation for this CCR to the electron source baseline design
is to reduce the overall cost of this area. CCR#22a and #22b will
significantly reduce the cost of the injector, mainly through reduction of
the lengths of beam and service tunnels and through elimination of a large
cavernous space that would have been used to house the laser system.
A second set of cost savings results from elimination of beam line
components. The new beam line layout allows the modification of the "dogleg"
section of the beam line into a vertically oriented chicane, which is
advantageous from an operational point of view. In addition, recent
(but still preliminary) simulations of the L-band bunching section show
significant improvements of injector efficiency if a tapered (beta-match)
TW bunching section is used, instead of two L-band buncher sections of
the baseline design.
The last two subjects (#22c and #22d) are not expected to have a significant
impact on the cost of the injector.
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
2. CCB finds that the revisions to the baseline configuration of the PES
system reasonable and acceptable and accepts this change request as is.
For record's sake here is an excerpt from overall CCB assessment:
CCB notes that a careful consideration is critically required for
the pointing jitter issues of the laser spot on the cathode.
Some ways (optical fibers within a temperature-controlled conduit
with possibly some active feedback elements, etc) to control
the disturbance along the laser beam transport should be provided
and be made part of the BC description of PES in a near future.
Additional communication and reference materials are available for
viewing, under CCR #22, at
The BCD files for PES section at the BCD/CCB wiki
has been updated as follows -
All-in-one BCD files will be updated shortly (within a day or two).
With best regards,
- Nobu Toge (KEK, Accelerator Lab)