107th ATF2 weekly meeting

International phone/webex meeting

EXT Vertical Trajectory - Why are ZV1X and ZV2X so strong?, Mark Woodley (SLAC)

Mark looked at the history file in order to see the setting currents of ZV1X and ZV2X in previous runs for January through June 2009 as well as those at the "old" extraction line for October,2007 through May,2008. There are linear correlation between them for both periods with large average currents as listed in following table. Possible kick locations which could have zero crossings were looked for with setting the average currents. The locations and vertical slopes there are listed in the table too.

Period	ZV1X	ZV2X	Δy' at Δy=0	s at Δy=0
Jan.13,09 - June 23,09 (ATF2)	-7.0A	+1A	-1.404mrad	~ 6.2m
Oct.22,07 - May 30,08 ("old")	-1.5A	+0.3A	-0.405mrad	~ 6.4m

, where -0.3332 mrad per amp at E=1.2857 GeV. The location is close to BS3X for both periods.

Defining a chi-square of the two currents deviating from the averages, various sources of rolls of septa, BH1X and vertical displacement (dy) at QF1X are estimated with the minimization. Results are listed in following table.

locaton	BS1X	BS2X	BS3X	BS1,2,3X	dy at QF1X	BH1X
source	18.9mr	9.3mr	4.66mr	2.67mr	+3.12mm	4.15mr
chi square	0.8640	0.7063	0.3102	0.5016	2.3906	6.8527

The best fit shows that roll of BS3X is the most probable.

With the best chi-square conditions, vertical dispersions (&eta_y) were calculated with and without the sum knob of QS1X and QS2X at locations of MDISP ( exit of KEX2 ), five wire scanners (MW0-4X), i.e.

Sum knob	MDISP	MW0X	MW1X	MW2X	MW3X	MW4X
without	-3.083mm(1.734mr)	-6.685mm	-4.479mm	-6.251mm	-0.704mm	2.716mm
with	0.0mm(-0.055mr)	-0.320mm	-0.257mm	-0.482mm	-0.177mm	-0.093mm

,where values are &eta_y ( &eta'_y ) .

In conclusions, assuming that anomalous ZV1X and ZV2X strengths are correcting for a single vertical kick:

1. the kick seems to have been present prior to ATF2
2. the source of the kick seems to be either very close to ZV1X or much farther upstream (in the DR?)
3. the "best" kick source is a roll of BS3X of ~4.66 mrad
4. assuming a BS3X roll, the vertical dispersion generated is small (~few mm)
5. if the kick is near ZV1X, then it is "in phase" with the QS1X/QS2X "sum knob", and the vertical dispersion generated by the kick plus the compensating ZV1X and ZV2X strengths is easily corrected using the "sum knob"
6. the inferred roll of BS3X seems unreasonably large ... other kick sources near ZV1X (i.e. stray fields) should be investigated

Q : Is it OK although ZV1X has large current of 7A ? I wonder if the strong setting of ZV1X would interfere in any vertical dispersion correction schemes.

A : ZV1X (and ZV2X) are not used in any explicit scheme to correct vertical dispersion ... they are only used to steer the beam through the centers of the inflector quadrupoles (as Okugi-san pointed out). So if we do nothing about finding the kick source we should be OK as long as we don't run out of strength in ZV1X (I checked that the vertical dispersion created by the assumed kick source plus ZV1X/ZV2X was small and correctible using the "sum knob"). If we run the extraction kicker at relatively high voltage (39 KV), ZV1X gets weaker, and so this shouldn't be a problem.

Q : Will large vertical dispersions be generated in a case that BS3X is re-aligned with rolling of "4.66mr" ?

A : If we find and fix the kick source, and then set ZV1X and ZV2X back to zero, the vertical dispersion will be smaller than it is now.

C : As explained at the last project meeting, we observed a correlation of ZV1X current and the kicker current as the higher kicker currents makes smaller ZV1X current, i.e. smaller vertical kick at the septa. So, multipole field may contribute at the septa.

C : I(Mark) remembered that we had such an effect in the SLC damping ring: a horizontal corrector in the ring was used to scan the beam across the septum aperture, and the beam in the extraction line was observed to move in a circle (X and Y motion)!

Interferometer Installation Report, Mike Hildreth, Kurt Jung, Mickey McDonald (University of Notre Dame)

Mike briefly reported the installation status and inital measurement of interferometer with his two students. This interferometer system will monitor relative (later, absolute) vertical positions of the two IP steering feedback BPMs. They are MFB2 and MQD10B at IP and Final Doublet phases, respectively, in a pulse-to-pulse feedback as shown in above reference file. At present, a half system was installed to monitor the vertical position of MQD10B. It is consisted of a laser, interferometer, retroreflector and two CCD cameras, which are set around QD10BFF.

The initial data show stabilities (RMS) of 35nm, 41nm and 45nm for a second, overnight and one hour at 1kHz, 0.2Hz and 1Hz, respectively. Laser pointing positions were also measured by two CCD cameras. So far, the stabilities are very good compared to ones at ESA/SLAC.

In summary, interferometer & Camera systems were aligned and ready to record data. DAQ is now in final configuration for data-taking. One Remaining Issue is to define and test PV (Page View) read/write/log with EPICS IOC.

Q : Do you measure the BPM position ?

A : At present, the BPM position is monitored with respect to support of QD10B.

Q : What is source of "40nm" vibration ?

A : We need FFT analysis to analyze the frequencies. It is small and may be caused by operation in air.

Q : Did you check your system for vibration?

A : Yes, we did vibrate it intentionally.

Q : What is future plan ?

A : We will come again to complete the system for two BPMs After Honda-san install MFB2 in end of August or September. Also, we will send an optical table for the support.

MONALISA at ATF2; First installation report, David Urner (University of Oxford)

David reported the check out of Monalisa for 1 through 15 July 2009 following the proposed schedule. It is consisted of double bellows system (DBS, bellows and outer/inner chambers), two end boxes for Shintake monitor and QD0, upper and lower angled tubes, and no optics system in this time. In addition, pressurized air (2 bar regulated) was supplied to outer bellows chamber.

First, the system was tested with wooden frame on the concrete roof ( 1 to 8 July). At the first test, vacuum leak was found to be 1 Pa/sec. Although the leak limits the vacuum pressure at 25Pa, it is sufficient for planned tests. Forces were measured on the frame during pumping with re-calibrated strain gauge and pressure differences. The two results were consistent. The forces jumped to ±200N at beginning the pumping since over-pressure regulator does not behave as expected. The regulator will be replaced.

The system was installed at IP with alignment. The forces were measured during pumping down, which were less than ±20N in steady state with regulator cycle of about 225sec. QD0 positions were tracked during normal operation of Monalisa by FARO laser tracker (KEK survey group), where the longitudinal (i.e. beamline) and transverse directions were also measured with respect to SD0 and QD0 table, respectively, by KEYENCE laser-distance meter. The displacement was generated by changing the pressure in the outer bellows system, while the inner bellows was at vacuum. A positive force indicates a net force pulling QD0 towards the Shintake monitor, a negative force would push it away from the Shintake monitor. So for the page 29 measurement we have changed the pressure in the outer bellows system to generate first small and then gradually larger forces in both directions. The main goal was to see if the QD0 would return to the original position or not. The QD0 displacement was indeed recovered when the forces were zero. Also left-right QD0 mover was tested by comparing the magnet mover position and measurement of FARO.

In summary, assuming that static tolerances of QD0 are 100um in x,y,z, our measurements show that even with the current pressure control system we meet this tolerance. The low spring constant of the DBS allows the QD0 mover to move the magnet unhindered. The next step is to do optics tests with the vacuum system in place to gain calibration constants. Our goal is to get first position measurements to the Shintake group late next spring.

Vibration measurements with and without Monalisa, Benoit BOLZON (LAPP) , David Urner, Paul Coe (Oxford univ.)

Vibrations of Monalisa system were measured on the wood frame and at IP. First, the pressure regulation effect was measured, where no additional vibrations and coherence-phase change were observed. At IP, effects due to Monalisa system were found to be small with respect to tolerances. QD0 resonance frequencies of 65.3Hz, 18.0Hz and 20.4Hz were shifted to 60.3Hz, 16.6Hz and 19.2Hz in vertical, longitudinal and transverse directions, respectively, since Monalisa was mounted between QD0 and Shintake monitor. Vibration transmission between QD0 and QF1 was also measured, where QD0 and QF1 resonances slightly appear in all 3 directions since QD0 resonant frequency is slightly lower (due to Monalisa weight).

In conclusions, relative motions of Shintake monitor and QD0 are summarized in a following table.

Direction	Tolerance	w/o Monalisa	w Monalisa
Vertical	7nm	5.0nm	5.7nm(5.8nm)
Perpendicular to beam(longitudinal)	~500nm	16.7nm	16.7nm
Parallel to beam(transverse)	~10um	17.2nm	17.2nm

,where value in ( ) is Monalisa with no pressure.
Relative motion of QF1 and QD0 is listed below; <<

Direction	w/o Monalisa	w Monalisa
Vertical	5.0nm	7.0nm
Perpendicular to beam(longitudinal)	8.9nm	34.2nm
Parallel to beam(transverse)	10.9nm	26.2nm

A possible solution is to put a mass on QF1 to reduce the resonances.

Q : Can you measure vibrations with a mass on QF1?

A : Yes.
After the meeting, this measurement was done as follows;
"I measured transfer function between QF1 and the ground and transfer function between QF1 and QD0 with masses equivalent to the mass of Monalisa. The resonance frequency of QF1 became the same than the one of QD0, and QD0 and QF1 moved then in phase. So, it works well! But be aware than relative motion of QF1 to Shintake is then slightly increased as it is the case for relative motion of QD0 to Shintake with Monalisa on it (because the resonance frequency decreased).
Also, I did some additional measurements to show if the resonances of QD0 and QF1 can be pushed at higher frequencies by cutting their feet (between T-plate and the honeycomb table) which are high, so that relative motion of QD0/QF1 to Shintake will decrease (measurements done simultaneously on the floor, on the honeycomb table, on the T-plate and on QD0/QF1). The results show that the vertical resonance of QD0 and QF1 (at 70Hz) is only due to the resonance of the magnets themselves (or rather to the resonance of the T-plate which has a high weight on it). For the horizontal directions, the resonance (at around 20Hz) is due to both the high feet of QD0/QF1 and the resonance of the T-plate. To conclude, the vertical resonance of QD0/QF1 will not be pushed at higher frequencies by cutting the feet, but the horizontal resonances will be."

Q : How much is tolerance between QD0 and QF1?

A : It is several 100nm, which is ATF2 values.

Phase measurement at the Shintake monitor for MONALISA, Takashi Yamanaka (The University of Tokyo)

During the beam size measurement, phase variation between 2 laser beams will be monitored and used for feedback by the phase monitor at the second interference point. Monalisa effects on the phase stability were measured by the phase monitor. Following three measurements are compared, i.e. without Monalisa, Monalisa with DBS and Monaisa opened to atmosphere.

The phase stability is defined as RMS in one minute at the measurement frequency of 1.5625Hz, i.e. slow drift is ignored. All the three measurements were done in every minute for 8 to 9.5 hours in midnight.

Results of "one minute phase stability" are listed below; <<

Condition	Mean (mrad)	RMS (mrad)
w/o Monaisa	135	52
Monalisa w activated DBS	163	49
Monalisa w atmospheric pressure	153	39

, where 135 mrad and 163 mrad phase stability corresponds to 5.7 nm and 6.9 nm fringe position stability in 174 degree crossing angle mode.

In conclusions, MONALISA system does not influence the fringe phase stability so much.

C : There is some confusion, i.e. the stability is defined as RMS for one minute and the mean and RMS for overnight.

C : On the phase measurement : By crossing the two laser beams, the interference fringe is constructed. Measure this fringe pattern by a liner image sensor and perform Fourier transform. Then the Fourier spectrum and corresponding phase are obtained like attached file. The peak of the Fourier power spectrum corresponds to the fringe pitch and the phase at this peak frequency corresponds to the phase of the fringe as shown in this figure(pdf). This phase can be said to be the position of the fringe. We are not interested in the absolute value of the phase but the relative change of the phase because we want to know the phase stability only by this measurement. The phase has no reference or the absolute value of the phase has no meaning. The phase is defined only in ±&pi range. So if the calculated phase jumps 2&pi, I just add or subtract 2&pi from the calculated phase so that its time variation become continuous.

KEK site meeting

• Screen Monitor and Knife Edge
  - add tungsten wire scanner for vertical beam size measurement at the IP
  - better to attach several wires
  - Wires should be attached to the end so that easily incerted
  
• Background Photon Reproduction with Computer Simulation
  - It seems not to be a important issue.
  - Rather, it may be useful to study SAD calculation
  
• MONALISA installation
  - Regaring the phase stability, the MONALISA system doesn't affect so much to the Shintake monitor. - However, it is the urgent task to measure beam size with the interference mode.
  So it is desired to install the MONALISA after the confirmation of this measurement.
  
• Chamber Replacement at the Final Bending Magnet
  - Originally, the chamber in stock is planed to be altered to have larger aperture.
  - Because of the residual radiation of that chamber, the new chamber becomes necessary
• Phase Stability
  - 1 minute phase stability is within tolerance (smaller than table vibration)
  - It is desired to find out the reason why the phase drifts in long term.