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Re: [ILC-Asia WG3] minutes of 12th meeting



12th ILC WG3 was held in KEK 3th building 7th floor meeting room on
February 2nd. 

1. Positron target test at KEKB Update (KURIKI Masao)

   A proposal of Positron Target Test at KEKB was presented again.
   Operation mode with the nominal KEKB operation is named as "KEKB
   mode".  Addition to that, "ILC mode" which makes 7 or 14 bunches
   with 1.4us bunch spacing on a same spot, is proposed. "ILC mode" is
   made by turning off one of the abort kickers which sweep the beam
   in vertical direction, and by filling only proper bunches.

   In KEKB mode, an effective duration for the energy deposit is much
   shorter than that in ILC. In ILC mode, the duration is still
   shorter, but it becomes longer than that in KEKB mode. The
   experiment in ILC mode would be a better demonstration.

   The possible damage on the vacuum window with the ILC mode is
   estimated to be smaller than that in the KEKB mode. 

   C. By considering the pulse duration and target rotation in ILC,
      the energy deposited is not so far away from the damage
      threshold established in SLAC.

   Q. Is the target safe in ILC if the target is survived in the KEKB
      experiment?  
   A. Yes, because the pulse duration of KEKB experiment
      is shorter than that in ILC.

   Q. What is the threshold?
   A. According to the SLAC experiment, the target is not damaged as long
      as the energy density is lower than the threshold.

   C. If W and Ti alloys are hard to obtain, pure W could be the test
      material as a reference.
     
   Q. How can we determine the damage on the target?  
   A. As an on-line way, we have to qualify by our eyes anyway. 
      After the experiment, there are several ways like super-sonic
      investigation, tension strength analysis, etc.

   Q. In ILC mode, do all bunches hit the same spot?
   A. Yes, at least within the spot size. 

   Q. Is the damage process well identified?
   A. No, it is not. Thermionic damage and acoustic damage are considered. 
      It is also unclear that the damage is an one-try effect or a fatigue.

   Q. Can we start just with a simple mount of a bulk W block?
   A. No. We need a remote mount anyway to clear the radiation safety
      regulation.

   C. We should start the experiment by using the usual abort beam,
      i.e.  without dedicated beam time. Since the condition in KEKB is
      harder than that in ILC, it is going to be a enough demonstration 
      if the target is survived with the KEKB beam. 
   
   C. If we turn off the vertical sweep kicker, we need 8 hours at least
      to install a dummy load. 

2. DR beam dynamics study WBS and AHP (KURIKI Masao)

   WBS(Work Breakdown Structure) for DR design and Beam dynamics study
   are presented. According to the WBSs, WP are defined and the BD
   studies are fit as the WP element. Since the fast Ion study does
   not exist, Dr Kim from PAL, Korea will cover this topic at least
   during his stay in KEK.

   As a possible extension of the DR study toward the DR layout
   decision, AHP (Analytical Hierarchy Process) is presented. In the
   frame work of AHP, different properties are summarized as an index.
   By calculating the index for all DR designs, decision can be made.
   Because AHP is based on the one by one comparison between
   properties, we have to make a consensus at least which one is more
   important and how important on all combinations.

   C. We should summarize the DR studies in the frame work of WBS and WP
      including US and Europa.  

   C. The convener should collect the deck files of various DR designs for our
      convenience. 

   C. According to our experience, it is hard to make a consensus with
      an engineering process like AHP. Sometimes, it is considered to
      be a sophistry.

   Q. It is nonsense to compare totally different properties like cost
      and beam performance.  
   A. Generally, to make any decision, totally different properties
      have to be compared. Usually, our intuition makes it with a help
      of discussion. AHP is not perfect, but might be helpful.

Next meeting will be held on February 16th. 


Reported by OMORI Tsunehiko and KURIKI Masao

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