77th ATF2 meeting

1. Present status of DR emittance studies and suggestions of future plans, Kiyoshi Kubo (KEK

We have constantly measure the 5pm emittance, i.e. the 5pm data of 4/16 2003 was shown. Also, we have simulation with 30um offset, 0.3mr rotation error of magnets, BPMs with error 300um and 0.02r rotation error. After COD correction, the V-emittance is 23pm, and it becomes to 16pm with dispersion correction, then it becomes to 5.8pm with coupling correction. The simulation shows dependences on BPM offset error and the magnet strength error. The strength error must be less than 0.5% . Also, it shows that the 2pm is possible with improvements of BPM offset error and optics error with BPM electronics upgrade .

However, recent emittance varies for 20 - 30pm. Vertical dispersion and x-y coupling become worse, i.e. 3mm to 5mm and 0.029 to 0.119 .

Sources of the larger emittance would be optics errors for it has been recently difficult to fit data, alignment of magnets and BPM calibration etc. . Before this April run, some of magnets have been re-aligned. But, the emittance is not improved yet.

Q : What definition is the emittance ?

A : The measured emittance is projected one, which is larger than the nominal one by 50%.

Q : How did you measure the 5pm emittance ?

A : We have used the laser wire, since the XSR measurement has larger error.

Q : What definition is the error bars in simulation results ?

A : They are RMS of results with 100 random seeds.

Q : why is the emittance so sensitive to Q-strength error ?

A : It effect all the dispersion, coupling corrections, i.e. correction procedure with 1% error does not make sense.

Q : BPM, rotation, errors can be deduced from measured results ?

A : in principle, Yes

Q : Using Rokko program, we can analyse the same data. Comparison with different analysis might be useful to understand recent results.

A : Yes

Q : Do you analyze the sensitivity of particular harmonics ?

A : No, it may be interested.

Q : In the simulation, is there limitation of magnet strength?

A : There is no limit.

2. Optical corrections in ATF2 and its long-term behavior, Yves Renier (LAL)

Q : Correctors are dipole magnets?

A : Yes, they are in v 3.8 optics.

Q : where are they ?

A : just before the FF section

C : correctors are far away from IP ?

A : For such corrections, we move the sextupoles

Q : why did not choose the horizontal movement ?

A : We changed the sextupole strength and v-moverment only.

Q : We can use H-mover of sextupole for tuning xx' , yy', worrying hysteresis in magnet strengths.

A : It is much easier to change the magnet-current than movers. We are worry about reproducibility of mechanical accuracy. So, we try to use the electrical corrections as much as possible rather than the mechanical ones.

C : the electrical ones ( Q-strength) are not sensitive for smaller beam size .

C : Changing the current from 130A to 128A, then increase it , there may be a problem for hysteresis.

C : The 5% error would be OK for matrix errors .

C/Q : In non conversion results, is there any effect from higher order ?

A : non-linear knobs may help. So we have to try .

C : if no effect is seen with a correction, do you just contine or choose other algorithm for another correction ?

A : We used cyclic corrections.

C : non conversion must come from large abberation. It must be difficult to correct.

Q: what is the beam size after 11.5 days before correction ?

A : It is 3.5 times larger as shown in histograms .

C : You may use Honda monitor to minimize the beam size at offset position.

3. S-band BPM support, Hyoung Suk Kim (KNU (Kyungpook Natinal University)) , Andrea Jeremie (LAPP) , Cherrill Spencer (SLAC)

C : The adapter has been originally proposed to fix at the pole to avoid the coil. Now, it is not good idea for the BPM is too heavy.

Q : What is purpose of adapter?

A : BPM must be connected to the magnet, where the Z position must be fixed.

C : Each BPM with beam pipe will be isolated with bellows .

C ; We need a ring or donut support inside the magnet at the other side of BPM beam pipe for 1mm gap with 100um accuracy.

C : SLAC has suggested a mover with manual adjustment ( newport ). We prefer the SLAC design for holding all around the BPM rather than the KNU one.

C : We could use a mover with step motor ,i.e. remote control.

Q : what are accuracy in each component of the support ?

C/A : We need a monitor the position of BPM relative to the magnet.

Q : When the magnets will be sent from SLAC to LAPP?

A : We (SLAC) are waiting for magnetic measurement, where the LCLS project is the first priority.

Q : What is measured at LAPP?

A : We plan to have vibration measurement of magnets with water cooling on the table .

A : July, August is difficult for vacation in France.

C : The transportation delay of magnets will significantly change a quantity of work at LAPP. LAPP has been asked for Qs on the table, S-band BPMs supports for Qs and sextupoles and de-mount/mount of BPM for test and shipment .

C : We should decide the deadline of shipment of magnets from SLAC in order to make realistic work plan at LAPP.

A : After the meeting, we received an email from Andrei as "We are aiming to finish all work with FDs at SLAC by April 25, and shipment from SLAC by April 28-29. "

KEK site meeting

4. Installation/commissioning of the Shintake monitor