ATF2 Meeting Minutes , October 7, 2009

115th ATF2 weekly meeting

October 7 14:30- 18:00, ATF LC meeting room, KEK.

International phone/webex meeting

Alignment results for SLAC magnets in the ATF2 beam line, Ryuhei Sugahara (KEK)

file : ( pdf , 15 pages, 1.2MB)

R.Sugahara briefly reported alignment of SLAC magnets which has been performed in 14-16 September, 2009.

The SLAC magnets are SF6FF, SF5FF, SD4FF, SF1FF, QF1FF, SD0FF and QD0FF which are re-used ones from SLAC with different alignment references from the KEK standard. Their positions have been surveyed and found to have rather big alignment errors, i.e. mm order, with the laser tracker for 22-24 July, 2009, as appended in the slides. We re-aligned them utilizing the SLAC alignment reference system and the laser tracker, where the error was aimed to be about 0.1mm .

The three dimensional results were shown along the beam line dividing three regions for alignment around FD system, SF5/SD4 and SF6. We achieved their alignment as good as the standard ones with following notes;

Shintake monitor has been found to be displaced by 2.849mm downstream in the July survey. Consulting with S.Kuroda and T.Okugi, the FD system were also displaced with the same amount for keeping the relative distance as designed one.
QF1FF : To adjust the left and right height difference of 0.35mm, it was rolled with tilt angle of +1.4mrad by mover.
QD0FF : To adjust the left and right height difference of 0.2mm, it was rolled with tilt angle of +0.7mrad and longitudinal displacement of +100um by mover.

, where the roll angle errors are limited by the magnet width with 0.1mm position error, e.g. the rolling errors are estimated to 0.76 and 0.33mrad at SF1/SD0 and QF1/QD0, respectively.

Q : What is the definition of coordinates, i.e. X, Y and H ?
A : It has been explained as Y is longitudinal one along the beam line from upstream to downstream, i.e. east to west, X is transverse and right to Y, i.e. right-handed coordinate and south to north, and H is vertical one upwards. The origin is the center of the DR as shown in this figure (pdf) .
Q : Are the detailed alignment data available ? They should be stored in a common data base.
A : I (RS) will send them for the data base. It is an excel file, i.e. here .

Brief discussion on the commissioning

file : priority tasks and responsibilities for Autumn commissioning ( pdf ) shown by P.Bambade at the ALCPG09/GED meeting.

P.Bambade initiated a discussion by referring the above slide. First we would like call for colleagues to request shifts (machine time) for specific studies in order to organize the tasks efficiently. Off-course the hardware commissioning is the first priority, which are cavity-BPM, stripline BPM, BSM and post IP carbon (C) wire scanner. Especially, I suggested B.Bolzon for a leader of the post IP-C-wire since he will be full time at ATF/KEK in 2009.

Q : Do we need to sign separately for bottom 4 tasks in the list ?
A : The last one is different from other beam tuning since it is specific to background study.
Q : How are the dispersion and coupling corrections ?
A : These can be done by a group of same people. In the task lists, we would like to promote young people who can focus on a specific one.
C : We may need to use Shintake monitor detector for the C-wire. Also, the orbit reconstruction uses the stripline and cavity BPMs. Therefore the tasks are dependent each other and need close collaboration.

First analysis results of EXT MW0-4 X,Y,-10,-10 wire-size measurements to reconstruct the 4D betatron phase-space, Cecile Rimbault (LAL)

file : ( ppt, pdf , 31 pages, 2.4MB)
file : Wire configuration of wire scanners at EXT by M.Woodley : pdf;
file : Coupling calculation <xy> for WS measurement by S.Kuroda : ppt;

C.Rimbault reported the first analysis results with 4 wire scanners at the extraction line for aiming a reconstruction of the 4D betatron phase space.

The data have been used for coupling corrections to find minima of vertical beam size by scanning quadrupole and skew quadrupole magnet's strength. Each wire scanner has x, y, -10^o and +10^o wires with tilted angles of &theta=-90^o, 0^o, -10^o and 10^o, respectively, while the scan direction angles are &phi= &theta + 90^o = 0^o, 90^o, 80^o and 100^o, respectively, i.e.
&sigma_u²=&sigma_x² cos²&phi + &sigma_y² sin²&phi + 2&sigma_xy² cos²φsin²&phi
, where &sigma_x=&sigma₁₁, &sigma_y=&sigma₃₃ and &sigma_xy=&sigma₁₃ =<xy> . So, &theta is the angle between x and tilted wires . The ±10^o tilted angles have been optimized for the flat beam ( P. Emma, M. Woodley, ATF-99-04 ).

Measurements have been performed on 28th May 2009 by G.White, Y.Renier, M.Woodley and F.Zhou. Beam sizes (projected ones) have been measured as a function of the QK1X current ( -20, -10, 0, 10 and 20A) by the 5 wire scanners in 4 directions except for MW0X without x-direction. The fork moving direction is 45^o . ( The correction factor for the fork motion is sin (45^o - &theta) . ) The data were listed in tables and also graphically shown as a function of the QK1X current.

Simple deductions of the coupling measurements are listed below;

If the major axis of beam lies along the horizontal axis, the coupling <xy> = &sigma₁₃=0
If <xy> is not zero, <xy> is constant with respect to &phi .
If &sigma_80^o=&sigma_100^o, <xy>=0

The couplings ( <xy> ) were calculated and shown as a function of the QK1X current. With respect to the above deductions, number of questions appears to her on the method, definitions of tilted angles and some problem in the data acquisition etc. , since results seem to be paradoxical .

In discussion, there were number of questions to this analysis, e.g. definition of &phi, estimation of <xy> error , definition of &sigma_u which should be projected one etc. .

KEK site meeting

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

file :ppt, pdf ( pdf, 31 pages, 1MB)
Presentation/file : "Gamma Detector of Plastic Scintillator by Yohei Yamaguchi", file : pptx, pdf ( 15 pages, 596KB)

* New Laser Installation
Q: Is the unseeded pulse stronger than the seeded pulse? Then can the unseeded pulse be used for the collision with the beam to raise S/N ratio?
A: The unseeded pulse is strong but the unseeded pulse isn't coherence. So it can't be used for interference mode.
* Check of Cooling Power of Laser Chiller
Q: How much is the temperature of the external cooling water?
A: The preset temperature is 15 deg C.
Q: The result of the temperature measurement shows the internal cooling water termperature is higer than 27 deg C even after the laser is off. Is the measurement correct?
A: It seems the optimum temperature of the laser is about 26 deg C. The laser system itself controll the flow rate of the external water and adjust the temperature of the internal cooling water.
* Gamma-ray Shutter
Q: Does the shutter mover use rail or something to slide? If not, it will get stuck in long-term operation.
A: No. The lead block move just on the flat metal plate.
Q: Is it possible to put the shutter behind of the background monitor? Because, the gamma-ray shutter is for the CsI(Tl) detector and the background monitor should be independent of the shutter.
A: There is limitation in the available space, so it may be difficult. Anyway we will try.
* Detector Interlock
C: It is desired to keep HV to the detector. Then the interlock should be prepared to the gamma-ray shutter rather than HV module.