89th ATF2 weekly meeting

International phone/webex meeting

The Carbon wire scanner at IP and BPM status/reqirement for operation, Doug McCormick (SLAC)

The IP scanner is ready to be shipped by Friday August 29th. There are hardware support needed at ATF, which are cables and written in the above presentation file.

QBPM electronics status and requirement for operation were presented. Especially, the board that had 2 dead channels was found to have four bad voltage regulators, which seems to be damaged by radiation during the beam test. Remaining boards and hardware, which include repaired, spare ones, will be shipped as soon as they are tested.

3 FF Sextupole magnets, Cherrill Spencer (SLAC)

Three old sextupole magnets of the same type have been refurbished for SD4, SF5 and SF6 in the final focus system. Aluminum supports were produced, whose design has been reviewed by Terunuma and Honda.

Magnetic field measurement of one sextupole has been done at three currents ( 28.5, 1.4 and 16A for SD4, SF5 and SF6, respectively) and the results are satisfied with tolerances. Second sexupole will be measured in this week, then the third one will follow. So, they will be ready for shipment in 8th September.

We discussed residual radio-activities in the two sexupoles, which must be imported by Japan Radioisotope Association. However, SLAC found in this Friday that their radioactivity was below the IATA threshold for a regulated shipment.

BPM supports were prepared by Honda at KEK.

S-band BPMs installation issues

S-band BPM production, Hyoung Suk Kim (KNU)

Decay time of S-band BPMs was changed from 31ns to 83ns for better matching in the digital electronics system. One BPM will be sent to KEK on 10th September, and the other three ones will be sent on 18th September. H.S.Kim will come to KEK when the BPMs arrive. In order to prepare the commissioning, H.S. Kim and A.Heo will come to KEK in October.

electronics preparation, Stewart Boogert (RHUL)

There are 10 sets of mixer electronics, which consist of 8(dipole), 1(reference) and 1 (spare). The 6 new ones will be tested within a week. The 4 old ones were just returned from SLAC, which will have minor modifications in two weeks. Then, they will be shipped to KEK in October. Stewart will visit KEK 4th till 25th September.

Location of processing electronics was discussed. Especially, a full size rack of down-mixed modules are necessary at ATF2, i.e. inside of the concrete shield. Honda will check the area, while there seems to be enough space around the Shintake monitor. One possible issue is temperature rise due to the electronics, since there is no air-conditioner at ATF2. If necessary, we can install a cooler. In any case, the electronics temperature will be monitored.

plan of the FD system installation, Nobuhiro Terunuma (KEK)

Therefore, it was suggested that H.S.Kim will come to KEK for 22nd till 26th September for the BPM installation.

KEK site meeting

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

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

*** Report on Fringe Phase Monitor ***
by using this monitor we estimate the phase jitter at the IP goal of phase stability is less than 200 mrad (RMS in 1 minute)

measurement result:
* unstabilized
400 mrad

* 1 channel stabilized
170 mrad (stabilized channel)
310 mrad (unstabilized channel)

* average 2 channel stabilized
210 mrad (both channel)

If we can assume the fringe phase at the IP is correlated with these phase monitors, the phase stability at the IP is also 200 mrad level.

** question, comment and suggestion **

Q: Do room temperature, cooling water temperature, floor vibration affect the phase stability?

A: It is possible. In the measurements at the Tokyo university, where a CW laser was used instead of the pulsed laser, the better phase stability was observed, i.e. 30 mrad in the stabilized channel, 70 mrad in the unstabilized channel. Therefore the worse phase stability may be due to the angular jitter of the pulsed laser.

C (suggestion): It usually takes several hours to stabilize the pulsed laser, you need to wait before start the measurement.

Q: The phase stability difference between the stabilized channel and unstabilized one is too different. Aren't there any defects in measurement methods?

A: If I swapped stabilizing channels, the phase stability was also swapped. It seems to be no problem in measurement methods. This difference may be due to a bad correlation of two channls.

C (suggestion): Why don't you see the correlation between the phase and the laser position by PSD-monitor? If the phase jitter is came from the angluar jitter, you can see some correlation.

C : In general, the phase control/feedback system requires a good correlation between phases as a function of time. The correlation can be calculated from measured phases at 10Hz, which can be Fast-Fourie-Transferred to A1(f) and A2(f), respectively. The correlation is real part of C12(f)= A1(f)A2*(f)/|A1(f)|/|A2(f)|, where A2*(f) is the complex conjugate of A2(f). We might see that the correlation will be about 1 in frequency range of less than f0. So, we can integrate phases for t< 1/f0. Then, the integrated phase will be used for the feedback. First thing is to calculate the correlation with present results.