55th ATF2 meeting

1. Re-location of IPBPM test setup,Yosuke Honda (KEK)

Honda suggested re-location of IPBPM-, nBPM- triplets and use of (IP-phase) QBPM replacing with the nBPM triplet in the v3.7 optics, since the pulse-to-pulse feedback does not require the BPM triplet and a set of mover and girder is needed in the suggested location.

A high sensitive electronics must be prepared for the IP-pahse BPM since the pulse-to-pulse feedback needs the BPM resolution of less than 100nm. The IP-pahse BPM is available from 5 QBPM spares.

The two triplets were suggested to be installed between QF21X and QM16FF, where the nBPM triplet meed a new girder for available space ( 1.1m length ). Especially, the re-location of IPBPM-triplet would be favored for the LW signals as discussed at next talk.

This suggestion is fine. The optics/device-list will be updated.

There are movers which can be used for the IP-phase BPM at SLAC.

Q : Does this suggestion require two new girders in addition to mover, for confirmation ?

A : Yes.

2. Effect of relocation of IPBPM on laser wire signal, Lawrence Deacon (Royal Holloway)

Simulations were done using BDSIM to determine the effect of the IPBPM location on the laser wire signal. In the "old" setup 61% of the signal was lost . In the "new" setup 43% of the signal is lost, which is the same one with no IPBPM. In conclusion, the re-location recovers the LW signal loss at the v3.7 IPBPM ( "old" setup).

Geometries in BDSIM are described as follows; Full aperture of IPBPM is 12mm (x) x 6mm (y) and the QBPM has 20mm diameter aperture, 120mm length and the outer diameter of 110mm. The BPMs are made of copper. The laserwire signals were generated at LW1, about 7m upstream of the IPBPM. The signals are separated from the beam at B5. They were counted with 20mm aperture trough QD6FF which locates just after B5. The simulation shows the signal cut by IPBPM in "old" setup. while no significant cut is observed except for 20mm aperture in "new" setup.

3. Realignment of DR Septa (Geometry/Optics Rematch), Mark Woodley (SLAC)

SAD deck has been successfully converted to MAD one, where the both coordinates agreed within 1 μm. First results of re-matching the optics were presented. The re-match was done by MAD with a condition of no geometrical change in downstream of the second kicker (KEX2). Major procedure is listed below;

• adjust AQM6R and AQM7R (bend angles at offset in Qs) to match SAD dX ("Gy") at BS1X entrance and BS3X exit
• adjust BH1/BH2 bend angle to make X=-6.0 m @ exit of KEX2
• adjust length of drift L101 (KEX2 to QF9X) to bring Z-positions back to v3.7 values
• rematch optics varying EXT quadrupole strengths

Remaining tasks for v3.8 are listed below;

• move nBPM and IPBPM test setups to drift between QF21X and QM16FF (Honda-san's suggestion)
• use spare QBPM and new mover for feedback IP-phase between QM14FF and QM13FF (Q : who has mover?)

  A : SLAC (Doug) has the mover.

• check Sugahara-sanfs problem devices
• use Okugi-sanfs stripline BPM assignments
• use standard glong-pipeh QBPM at QD6FF
• check length of SLAC OTR (Doug)

  A : It has 33cm total length, i.e. length between flanges, which has been checked in last December.

• add 1 m to drift between BDMP and dump
• add a quadrupole just u/s of BDMP (Okugi-san ref)
• KEK people will find 2 new IDX-like skew quadrupoles plus power supplies (?)
• others?

Q : What is chi1 in SAD deck?

A : It is a geometrical rotation angle of orbit around y with respect to the origin (entrance).

Q : What means in wide range of QF7X position shift ?

A : The shift depends on the bend angle at offset in QM6R and QM7R. The ambiguity comes from ignorance of beam positions there. We could not properly read BPM signals due to the kicker noises.

C : SLAC is updating the DR-BPM readout system. We may study this "noise" problem in parallel to the update again in this December, since there has been improvements in the DR-BPM electronics in last winter by Naito-san.

Q : Did you (Doug) reply a question of carbon wire scanner geometry from Shintake monitor group ? The 3D drawing is interested for detailed configuration.

A : The total length of scanner is 18cm as Okugi-san's file. We are preparing the 3D drawing for them.

Reference: Realignment of septums for extraction, Shigeru KURODA (KEK)

file , SAD deck file, Twiss file and geometry file with re-alignment of septum.

5. KEK site meeting ( in Japanese )

Terunuma commented that there is delay for new concrete shields while number of "used" shields have been gotten. Due to international bidding process, the concrete shields will arrive in middle of December. A new beam dump will arrive in October as planned. He will update the schedule of dump, concrete shields and floor painting on the home page. The paint should be epoxy for no crack for the long term.

The next ATF2 meeting will be held on 29th August 2007, 9:00am -, 3-gokan, 425, KEK, TV-ID#=31110 with the KEK Gatekeeper and ILC Webex.