ATF2 SC-Q Meeting

October 15 7:00- 8:00, Webex

Participants : Brett Parker, Andrew Marone, Michael Anerella (BNL), Akira Yamamoto, Nobuhiro Kimura, Takayuki Tomaru, Toshiaki Tauchi(KEK)

Recent studies at KEK, Nobuhiro KIMURA (Cryogenics Science Center / KEK)

file : ( pdf , xx pages, xxxx)
supplement : Layout around IP ( pdf , 6 pages, 1.8MB), Vibration measurement on the Shintake monitor etc. (Japanese) ( pdf , 13 pages, 968KB)

N. Kimura briefly reported a progress since previous meeting, 30 Sep.2009. He started a design of connection box with HTC current leads for 2 x300A and hybrid-copper leads for10x100A. He already contacted to the company. There will be two cryo-coolers which are 0.4W/4.2K one for the current leads and 1W/4.2K for coils . KEK responsibility was suggested and shown in a figure.

As an example, he introduced the SKS magnet with iron yokes and sector type coils at JPARC showing three cryo-coolers for condensation, one cryo-cooler for current leads of hybrid type with 0.1W/lead and a connection tube to distribution box.

C : The control dewar/box on top in the figure may change the position to side. So, the figure is just schematic view of a concept.
Q : What is the hybrid lead ?
A : It is Cu connected with alloy with low content of Cu (Cu-plating with variable thickness). There is a CERN document which will be sent to you.
C : Average current of correction coils is critically important since the total current of 10x100A=1,000A is unrealistic for the cryo-cooler system. The cost scales as 100K dollars /1W cryo-cooler .
A : Yes, we need to study to minimize the total current.
A : The correction coils are used for alignment of magnetic field centers and ones in the sexupole are especially used for IP beam size tuning by changing the magnetic center position.
C : Since there are quadrapole and sextupole magnets in a cryostat, one of positions is aligned with mechanical mover. So, the currents must be reduced.
C : Anyway, we need information of dynamic range for the movement of sextupole from the optics group.
C : Recently we heard experiences at TRISTAN on bubbles in a cavity with cryo-cooler system in too-limited space. Therefore, we must have a good design to handle gas from bubbling in the cryostat.
A : BNL has a good design in such way for bubbles to never touch coils.
Q : What length is a He pipe from the box to cold mass ?
A : It is 15 inch, i.e. about 40cm.
Q : For smaller vibration, cryo-coolers should be rigidly supported on the floor. Also, flexible pipes are needed. Is it right ?
A : Yes (by T.Tomaru).
Q : We need information of environment in the ATF2 tunnel.
A : The layout and vibration measurement are supplemented in the agenda.

A.Yamamoto summarized above discussion to two questions; i.e.

  1. What is gas evaporation route and height of connection point in the conceptual design of cryostat ?
  2. How much is average current values for correction coils, which must be less than 250A ?
    Who are responsible to tell the current value?
N.Kimura will continue the study and T.Tomoru will study a mechanical separation of cryo-coolers from the cryostat. Both address the first question. Also, BNL is expected to study this question. T.Tauchi will ask the optics group ( S.Kuroda, T.Okugi at KEK, and G.White at SLAC) for the second question.

A face-to-face meeting was suggested to be held well before the 9th TB/SGC meeting, 17th December,2009, where the updated proposal will be presented and reviewed.
We would like to suggest a full day meeting on 24th November at BNL. N.Kimura and T.Tomaru will participate in person. Anybody to visit to BNL must tell B.Parker as soon as possible .
We need one optics expert in person at the meeting.

Next webex meeting will be held at 7am, 29 October (KEK), or 6pm, 28 October (BNL).
URL : http://ilcagenda.linearcollider.org/conferenceDisplay.py?confId=4238