90th ATF2 weekly meeting

International phone/webex meeting

First Alignment of Downstream ATF2 magnets, Ryuhei Sugahara (KEK)

First alignment has been done at ATF2 for 12 through 27 August, 2008. Coordinates show x from south to north and y from east to west, where the beam line is approximately along y. There are 12 makers, so-called alignment monuments, on the floor.

The alignment results that RMSs of magnet positions are 0.13mm and 0.11mm in x and y, respectively. Since the goal is less than 0.1mm, the second alignment should follow, i.e. to be scheduled in late September.

Also, a table was presented to show positional and rotational offsets of all the QEA magnets which have been produced at IHEP, China. The offsets are magnetic field centers relative to the mechanical references at each magnets, and the units are mm and mrad. They must be taken into account for alignment and mover-control.

Q : How did you set the movers ? Did you use the mover-control system?

A : the movers have been set in the middle.

Q : how do you know the middle ?

A : Doug has set . Measured gaps are OK, (except for 4 movers at FD ).

C : FD system arrived at KEK. On 16 Sep. LAPP colleagues will come to KEK, and install them.

Q : y is along the beam ?

A : yes

Q : where is z?

A : Z in vertical and we adjusted the heights by scope. They can be checked relative to the beam line within 0.1mm accuracy.

Q : Concrete block will be moving?

A : we will check it. we hope they will not move.

Q : in the table, rotational unit?

A : Do we need take account of the offset in the table?

C : We can change the softwares to set x, y cordinates

Q : the rotation offset can not be adjusted by movers

A : they are already corrected by the movers.

Progress of Shintake monitor, Takashi Yamanaka (The University of Tokyo)

The phase monitor/control has been installed in the optical table, where the phase can be controlled by changing one of laser path length with piezo mover. Nominal beam size measurement takes 60 sec.

In conclusions
Performance tests regarding optics were done and dominant error soruces of beam size measuremen are evaluated.

1. Laser interference visibility is 100 %
2. Position jitters at the IP are 3.2 um in vertical and 1.9 um in beam axis. They cause the power jitter at the IP but it is small enough.
3. Phase jitter at the IP is expected to about 300 mrad even if we perform the phase stabilization, which is a little bit large for our goal of the phase stability (200 mrad).

Q: The electron beam comes at 1.5 Hz but you use the 10 Hz pulsed laser. How do you adjust the timing of them?

A: We shot laser pulses when the beam doesn't comes and also perform the phase stabilization. Only when the beam comes we adjust the laser shot timing to the beam.

Q: How do you adjust the laser timing to the beam?

A: We need to construct the laser trigger system from now, so we can't answer now.

Discussion : Plan for a special ATF2 project meeting, 1 Oct., KNU

KEK site meeting

Progress of Shintake monitor (ATF2 IP-BSM) work by M.Oroku

Participants: Tauchi, Terunuma, Kuroda, Okugi, Yamanaka, Kamiya(WebEx)

Topic: Phase Stability Measurement using Phase Monitor

• Phase measurement has done by using the CW laser to remove the effect of laser angular jitter.
• Phase monitor ch2 seems to have less phase search resolution.
• As a result, phase jitter pulse by pulse disappeard but the seconds order vibration remained althogh the phase stability in 1 min is improve to 170 mrad.
• Phase drift in long time has no correlation to the air temperature.
• If I hammer the optical table lightly, phase jump was observed. And also the vibration source was put near the optical table on purpose, the phase stability was degenerated to 260 mrad in this case.
• From the frequency analysis phases of two monitors has a clear inverse correlation below 0.01 Hz and above this frequency the correlation getting worse.

Suggestion: To make the measurement reliable, you need to do performance test of phase monitor.