109th ATF2 weekly meeting

International phone/webex meeting

Reconstruction of electronic noise and beam fluctuations using strip-line and cavity BPMs, Yves Renier (LAL)

Y.Renier reported results of analysis for BPM readings by reconstructing initial parameters of x, x', y, y' and ΔE/E at IEX ( injection point of extraction ) assuming the linear optics model. The reconstruction was performed with the least square minimization of difference between the predicted trajectory and the measured one at all the BPMs except for sextupole BPMs, MQF4X, MQF9X, MQM15FF and MQF17X which have been bad. In this analysis, the transfer matrix (R) is determined by the lattice, i.e. a model.

The data consisting of 500 orbit measurements were taken after BBA on 14th May,2009. Dispersion and coupling corrections have been made. The lattice parameters have been saved by the Flight Simulator.

First, distributions of reconstructed 5 parameters were shown. They all have Gaussian peaks with flat tails. The RMS's are 34.5um, 13.3urad, 9.34um, 9.72urad and 0.0905% of x, x', y, y' and ΔE/E, respectively.

Second, scale factors of BPM readings were calculated from linear correlations between the reconstructed readings and measured ones. The scale factors in x seem to be good, while ones in y are bad due to small values with respect to resolutions.

Finally, all the BPM readings (RMS) are plotted along the beam line under three conditions of (1) no correction, (2) compared with reconstructed trajectories and (3) correction with scale factors in addition to (2) .

In conclusions, the reconstruction seems to be a bit less efficient in dispersive regions. Hypothesis of scale factors seems to be accurate. This is a way to determine these factors parasitically, almost realtime . 10-30um resolution in x is not fabulous, but much better than 500um for some of them before the reconstruction.

In prospects, to use this new tool to monitor the scale factors in autumn runs and to try to correlate the trajectory with other measurements, for example intensity.

C : QBPMs should have resolutions of sub-micron meter. Model independent analysis should improve results. I (G.White) can send such analysis routine to you.

A : This analysis shows orbit errors rather than BPM resolutions. So, I agree with you and welcome to the routine.

Q : There are angular jitters of about 10-20urad due to kickers between the two kickers. At downstream of the second kicker, the jitters would be disappear. Can you look at it?

A : Yes, I will see it.

Q : We see negative scales. Are they real ?

A : Negative scales are only in y because of large orbit jitter than the resolutions. In x, they are all positive.

Q : Do you see correlation between the 5 reconstructed parameters ?

A : Not yet. I will see the correlations.

Q : Did you check the calibration status of QBPMs which may be unstable?

C : The calibration constants are available by the QBPM group.

Progress report on multi-OTR fabrication and schedule (IFIC-SLAC), Angeles Faus-Golfe (IFIC)

A. Faus-Golfe reported the progress of multi-OTR system which has been proposed at the 8th Joint Meeting of the ATF Technical Board and System/Group Coordinators, 11 June,2009.

The design is being finalized with shortening beam tubes in total length of 300mm. The hardware components of movers, control devices and optics are being purchased. Fabrication process was well defined. The possible locations ( 4 OTRs) are being studied with realistic optics including all possible machine imperfections. We are contacting with Terunuma-san for the locations. Modeling the OTR measurements, performances will be compared with the multi-wire scanner measurements. Also, softwares of controlling the hardwares and analysis are being prepared .

In conclusions, it will take about 4, 2 and 4 months to design and fabricate the hardwares, to simulate the performances with realistic optics and to prepare softwares of control and analysis, respectively. A realistic schedule will be ready in mid-September,2009 .

Q : When will you install the OTR systems ?

A : The installation will be after this December.

Q : What kind of hardwares do you expect from KEK ?

A : Yes, there are supports at least. We can tell you the details by end of this September.

Q : Is there any alignment laser to be used ?

A : We could use it. Is it right, Doug?

A : OTR movers give us many flexibility in x and y, up and down directions. The movers can be remotely controlled in dynamic ranges of +/- 13mm in x and +/- 2-3mm in y. The laser alignment is fine, but it is not essential.

C : Alignment laser of LW was already installed at downstream of QF9X. You can use it if necessary.

A : Yes, it would be nice.

C : OTRs also disturb beams, but have fast measurements. So, the OTR system is complementary to the multi-wire scanner system.

A : Yes, it is. It can measure jitters there for example. ( The wire scanner measurements include jitters.)

KEK site meeting

• Enlargement of the Laser Hut
  Q: where will you put the power supply unit of the laser which will be put in the extended laser hut?
  A: In the laser hut. In principle a power supply unit should be put outside of the laser hut to avoid vibration and heat source. However the present(old) laser will be put in the extended laser hut and it will be used only if an emergency arises.
• IP target holder
  - It will be possible to limit the stroke of insertion stage to 100 mm by shorteing the holder length.
• Correlation between laser position (angle) and phase
  - It seems that the feedback of the laser position is needed to stabilize the phase.
  Q: Is it possible to do the position feedback with the devices in hand?
  A: Yes. We have laser position detectors and motorized mirrors.
  Q: How can you explain this correlation?
  A: I think this is due to the change of the laser path length by the change of the laser angle.
  Q: If that so, the change of the phase should be the quadratic of the laser angle (Measured data shows it is linear.)
  A: It seems. I can't answer now.