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Fw: [CCB-92] Change request for BCD



Dear GDE Colleagues,

As per the CCB change procedure (v.0.3, Jan.5, 2006) I am forwarding
a change request for the RTML part of BCD we received from Peter Tenenbaum
today (Jan. 27, 2006, JST).

Unfortunately the complete mechanics (electronic bulletin board etc) of
change control procedures are not yet in place. However, I believe that 
CCB must act as quickly as possible to help the colleagues make progress
towards the Bangalore meeting and RDR. Therefore, I would like to
compress the action schedule drastically, and would like to proceed
as follows -

1. Based on the preliminary screening that I have done, I agree that
   this request belongs to Class 1, so this will be treated
   as a Class-1.

2. I would like to request comments from the ML area system leaders
   (C.Adolphsen, H.Hayano, L.Lilje, N.Solyak) and DR area system
   leaders (J.Gao, S.Guiducci, A.Wolski), as to -

   - Whether you agree with PT's change request, particularly
     in relation to redefinition of the area boundaries, and
   - Whether you have any additional comments or remarks.

   The deadline I would like to set for this is the end of Monday, Jan.30,
   2006 PST (because California is the last time zone). Comments
   from any other members within GDE should also meet this deadline.

3. I would like to ask two CCB members 

         Daniel Schulte and Kiyoshi Kubo

   to review PT's change request report, and comments from the ML and
   DR area system leaders and share your assessment, as to -

   - Whether you agree with PT's change request,
   - Whether you have any additional comments or remarks.

   The deadline I would like to set for this is the end of 
   Wednesday, Feb. 1, 2006 PST.

The goal is to make a final decision and approval of this request by
the end of Feb.3, exactly one week from now.

If you have any problems with this plan, please let ml-ccb@xxxxxxxxxxxx
know a.s.a.p.

------------------

Now, while this change request #1 is on its way, I have a comment.

At the document repository for the Area Leaders Meeting of Jan.19-20
at KEK (http://lcdev.kek.jp/GDE/ASL2006KEK/) there is a document
drafted by EC which outlines the BCD beamline descriptions.

   http://lcdev.kek.jp/GDE/ASL2006KEK/FollowupTor.21JAN2006.pdf

PT's change request for RTML comes along the lines of this document,
with his additional statements.

If the whole Area System Leaders could submit a set of change requests
to update their beamline descriptions in one shot, it would greatly
improve the efficiency of the related change process collectively.

While exactly how the Area Leaders and EC coordinate this work should 
be left up to the responsible parties, if a coordination of this
sort takes place on the part of change requesters, I would like to 
coordinate the CCB responses accordingly.

------------------

OK, this is all for now.

Sincerely,

- Nobu Toge (KEK, Accelerator Lab)
  email: toge@xxxxxxxxxxxx
  voice: +81-29-864-5224
  fax:   +81-29-864-3182
--- Begin Message --- I am writing today to formally request approval of the changes to the RTML section of the BCD which were presented and discussed at the recent ILC ASL meeting in KEK. Specifically:

1.  The damping ring extraction section is moved to the damping ring area.
2. The RTML-ML boundary lies between the diagnostic region at the end of the RTML and the upstream face of the first cryomodule in the ML. The diagnostic region at the beginning of the ML is redundant with the one at the end of the RTML and should be deleted. 3. The multi-wire emittance station immediately downstream of DR extraction is deleted and replaced with a single profile measurement device, technology to be determined. The combined result of items (1) and (3) is that the RTML now begins with a Skew Correction Section, not a Damping Ring Extraction section or an Emittance Measurement section. 4. A DR stretch region of approximately 610 m length is inserted to adjust the location of the DRs within the site footprint. 5. The skew correction section is removed from the emittance station which follows the spin rotator. 6. The linac launch and diagnostic section at the end of the RTML is extended from 30 m to 60 m.

Considered as a whole, my judgement is that this is a Category 1 change to the BCD, with a total cost impact of under $100 million.

I look forward to hearing from you on this matter.

-PT

--- End Message ---
--- Begin Message ---
Text changes:

Overview:

eliminate "Completing the achromatic extraction of the beam from the damping ring" and "Moving the beam from the axis of the damping ring to the axis of the main linac (geometry match)".

Description:

Eliminate section on "Extraction Geometry and Betatron Match"

Section on "Emittance and Trajectory Measurement", replace existing text with:

This beamline uses a set of four orthonormal skew quadrupole magnets to couple all four xy coupling terms in the beam matrix; this allows coupling introduced by the process of beam extraction from the damping ring to be corrected globally. The coupling correction section is followed by a single transverse profile measuring device (exact technology yet to be decided), which permits emittance measurements to be made via quad scans. At the end of this beamline there is an insertable stopper which can be used to stop the beam from passing into the collimation section <http://www.linearcollider.org/wiki/doku.php?id=bcd:ring_to_main_linac:ring_to_main_linac_home#transverse_collimation> and other downstream areas. This stopper can probably only handle a fraction of the nominal beam power, and so can only be used for very short trains, very low repetition rates, or some combination of the two.

In-between sections on "Transverse Collimation" and "Turnaround", insert the following section:

Damping Ring Stretch

This beamline is a simple coasting beamline of 610 m approximate length. Its purpose is to allow the arc of the damping ring to fall entirely within the ILC site boundary (currently set by the arcs of the Turnaround, see next section). Without this section, the arc of the damping ring would extend some 610 meters past the arc of the turnaround, creating an undesirable extension of the total site length required for 500 GeV CM. The Damping Ring Stretch also contains several BPMs which are used to measure the bunch-by-bunch position of each bunch within a train, which can be corrected (in a feed-forward sense) by correctors in the trajectory correction section.

Trajectory Correction section: replace "emittance measurement" with "Damping Ring stretch".

Emittance Measurement and Coupling Correction section: rename "Emittance Measurement" and replace text with the following:

This beamline uses a set of 6 laser wire profile monitors to make sure that the emittance correction is properly performed. The current baseline calls for a system which can measure full beam matrix and extract the normal mode emittances and the coupling terms. The emittance measurement station must be capable of measuring emittances during multibunch operation, using many bunches to measure the emittance within 1 train, and must also be capable of measuring emittances during single-bunch operation, using many pulses (at 5 Hz) to complete one measurement.

Magnet Counts table: replace with table on Slide 6 of my recent KEK talk.

Instrument Counts table: replace with table on Slide 7 of my KEK talk.

System Lengths table: replace with table on Slide 5 of my KEK talk.

Justifications:

Remove first sentence (which ends with "...is self-evident.").

Second paragraph, first sentence: replace "emittance measurement station" with "profile monitor"

Sixth paragraph: replace "lattice" with "lattices".

-PT

N.Toge wrote:

Hi, PT,

I don't have exact replacement text, I can generate this shortly.

OK, we will stay tuned, and get ourselves prepared by then.

- Nobu

--- End Message ---