ATF2 IP Tuning Task Group Meeting

Monday 22 Sept 2008, 17:00 → 18:00 Asia/Tokyo

Glen White (SLAC)

Co-ordination and reporting of efforts to develop and test tuning algorithms for obtaining and maintaining the goal 35nm IP spot size.

17:00 → 17:10 RMS vs. Gaussian core IP size determination

differences in tuning behaviour when looking at a numerical RMS description of the beam size and fitting a gaussian to the core and using the calculated width

Speaker: Dr Glen White (SLAC)

Slides ATF2_iptuningmeeting_220908.pdf

* Agreed for now, RMS measurement of IP beamsize probably most representative of the measurement made by the Shintake Monitor and should be used as the input for tuning simulations. * Around the target region of ~35nm, there appears to be a good correlation of RMS versus gaussian fitted core beam sizes, this correlation gets worse for larger beamsizes, presumably where larger non-linear terms dominate and generate a larger tail to the beam profile. * Kuroda-san suggested comparing a measurement of the RMS with a truncated distribution to the gaussian fit. * Results of simulations tuning with RMS compare well with those tuning with gaussian core- RMS case is slightly better in fact. Did not show any results of tuning time with the 2 cases- need to do for next time. * Problem Rogelio showed where beam size does not reduce below ~35nm for pushed beta case still not resolved- we would perhaps need some direct measurement of the core here, which is probably impossible?

17:10 → 17:25 Tuning Simulation updates

Simulation details and results with improved sextupole multiknobs

Speaker: Dr Glen White (SLAC)

Slides ATF2_iptuningmeeting_220908_simupdate.pdf

* showed improved simulation results from Glen White. * Improvements come mainly from changing method of applying sextupole multiknobs to use sextupole BPMs as a readback that the sextupole moves went to the correct location for each tuning step. Still need to understand if any additional averaging of BPM readings this would require makes this too difficult... * Still need to check power supplies and movers stay within allowed values during tuning procedure * Need to add more realistic treatment of sextupole mover system using hardware data from Janice (move size vs. time vs. accuracy) * Add during-tuning dynamic effects (suspect not important). * Showed effect of adding measured multipole components to FFS magnets- Sextupoles and dipoles ok- final double multipoles cause significantly worse performance, mainly due to sextupole and decupole QF1 and QD0 components. Need to re-tune design optics to take into account expected sextupole components which should hopefully restore the beamsize.

17:25 → 17:35 Goals and schedule for task group

Planning to achieve a presentation of agreed tuning algorthims and cross-checked simulations thereof by Dec ATF2 meeting

Speaker: Dr Glen White (SLAC)

Slides ATF2_iptuningmeeting_goals_220908.pdf

* next meeting to be October 16th, not as shown in slides in order to avoid Japanese holiday and CLIC meeting- time and details will be annouced on atf2-commissioning email list.