106th ATF2 weekly meeting

International phone/webex meeting

Effect of the wire size on IP beam size measurements, Sha BAI (IHEP)

Sha evaluated a formula of beam size measurement ( wire scanners) by simulation. The formula has been used to calculate a beam size corrected with wire diameter and it is equal to &sigma²_true=&sigma²_measured-(d/4)², where d is the wire diameter.

The simulation is based on a convolution of Gaussian beam and a wire with circular cross section. Simulated distributions were fitted with Gaussian, whose sigma is called as "simulated beam size" to be compared to one of the formula ( "corrected beam size" ).

In conclusion, the formula can be well applicable for beam sizes of greater than 4 and 2 um in cases of 10 and 5um diameter wires, respectively, where there is agreement with the simulation within 1 % .

Q : How did you actually simulated ?

Q : What are the simulated distributions ?

Q : Are the simulated distributions Gaussian ?

A : They seems to be Gaussian.

Others

Q : Will you plan the septum alignment in this summer shutdown?

A : We could align them with accuracy of 0.2-0.3mrad in roll and pitch angles. However, we do not know actual magnetic field lines.

C : From studies so far, there are two options, i.e. (1)to rotate the septum with evaluated value and (2) the vertical dispersion to be corrected by the orbit bump as Kubo's analysis. We should discuss how to proceed.

C : We still do not know the origin while the septum is suspected. M.Woodley is investigating possible origins and further correction schemes. We should wait for his result.

KEK site meeting

Yamanaka reported progress of a linear insertion stage for screen, knife edges at IP and also a collimator layout as well as installation of Cherenkov counter. He showed phase stability of laser interference by the phase monitor for 8 hours. Finally, he presented a beam time shift plan.

Following his plan, we discussed on this issue in details. It is not concluded.