87th ATF2 weekly and commissioning meeting

Commissioning Team

Report from each task leaders with "Very High" priority

There are two schemes based on (1) multi-wire scan and (2) 2-Qs and 2 skews scan. Major questions are ; 2 skews are enough ? and 3rd skew is needed? - if so, where is the optimal position and strength. We will work with FS.

C : After the radiation inspection in this December, we must focus on simulation works.

C : Commissioning should be planned in logical process then ask people to come.

Q : There are coupling correction programs by Okugi and Mark. Is it easier to move them to ATF2 ?

C : In general, we need 4 skews, but 2 skews can do major job.

EXT dispersion corrections can be done by (1) varying RF freq. or (2) modulation of the EXT line optics, which will be integrated in FS .

Q : Is there dispersion residual from DR ?

Q : Which dispersion is larger from DR or EXT ?

There are two schemes of (1) 1 to 1 correction and (2) dispersion free. A major issues would be finite resolution of setting power supply for correctors with 11 bits in dynamic range of 11.5mr. So, the minimum step is 6.75urad, which must be too large.

Q : What is the effect of the minimum step on the orbit ?

A : We do not need 11.5mr ( in simulation ) , but may need 5.6mr.

A : The study has been shown by Glen. The fluctuation of 1 or 2 bit cause big fluctuation at IP. So, we need smaller dynamic range.

A : KEK replied, there has been no fluctuation of last bits.

Q : How did you determine the 11.5mr ? Is there large injection error ?

Q : It should be 0.5mr at present.

A : Where is the strength data available ?

A : Okugi will check the strengths.

A : Glen took this value according to Mark's table .

The correction would take 5 -10 minutes, which is based on movers. It should be simulation-free.

Q : how to correct motion at upstream of FF

Commissioning strategy and plan,Toshiyuki Okugi (KEK)

The commissioning schedule was presented with trip plans of colleagues, as listed in the above excel file.

We will have RF gun commissioning in early October. Also we expect fast kicker installation for R&D in Jan, 09 , whose schedule will be decided at the special project meeting, 1 October.

As discussed, we would like to exchange emails by using the mailing list of atf2-commissioning@ilcphys.kek.jp in order to discuss an optimal strategy of commissioning, i.e. earliest plan to achieve 37nm beam size.

At next meeting, 20th August, we continue to have presentations from the leaders with High priority and we will discuss the optimal commissioning strategy.

KEK site meeting

1. Magnet polarity

Polarity of steering magnets should be same as those in the DR straight section. Polarity of skew magnets should be focus type Q rotating in right direction by 45 degree, i.e. top and bottom tips have N-pole while left and right ones have S-pole.

Polarity of QM-magnets follows the basic design values.

polarities of all magnets will be checked before the commissioning.

2. Calibration of DR-BPMs

Honda pointed out that we can use test pulses for the calibration.

3. Alignment works

Alignment of EXT will be complete in this September. We do not know if alignment is necessary in the BT.

4. Progress of Shintake monitor (ATF2 IP-BSM) work by T.Yamanaka

We measured the interference fringe in the actual setup, i.e. actual paths and actual optics. In this setup the position jitter at the IP was in the acceptable range (less than 1 um). By calculation taking into the power imbalance of two laser paths, the visibility of the interference fringe cofirmed to be almost 100%.

Laser position measument using PSD was started. It is thought to be possible to calculate the position jitter at the IP by this measurement.

C : You need three PSDs to check the result of position jitter calculation. (Okugi)

Q: Is the 1 um position jitter at the IP also acceptable at the measurement of the 35 nm smallest beam size? (Kuroda)

A: Even if the laser beam position changed at the IP, the interference fringe position doesn't change because the fringe position depens only the phase between two laser path. Therefore the position jitter affects only the laser beam power and also this jitter will be corrected by PSD measurement.