1. 13th ATF2 Project Meeting Summary
January 2012, KEK
Summary
11-13 January
13th ATF2 Project meeting 1

2. Critical review of beam instrumentation and beam tuning status
Introduction and Goals
Critical review of beam instrumentation and beam tuning status
2. Make a strategy to achieve the first goal and a preparation for the second goal until next project meeting, summer 2012
3. Encourage contributions from young researchers, especially PhD students as much as possible
11-13 January
13th ATF2 Project meeting

3. 11-13 January
13th ATF2 Project meeting

4. Alignment and DR:
Optics in DR

5. - January ~ Alignment for end of BT line Beam operation
Alignment and DR:
Alignment status
Actions in 2011:
- January ~ Alignment for end of BT line
Beam operation
East Japan great earthquake (11 Mar.)
Test beam operation
Recover, Survey and Alignment ....
-Now, the survey of DR is continued.
- Next, BT is due to be aligned.

6. all BPMs in arc section and around injection/extraction region.
Alignment and DR:
BBA at DR
- We measured the BPM offsets swith respect to magnet centers near by the BPMs for
all BPMs in arc section and around injection/extraction region.
- The COD orbit was improved by applying the DR BBA data.
- The beam orbit around extraction region was improved by applying the BBA data-

7. Alignment and DR:
DR emittance

8. Instrumentation : Multi-OTR System
The Multi-OTR has been working successfully during Fall 2011 run
New demagnifier system has been implemented speeding the beam finding.
Used for beam size and emittance measurement. Due to presence of background and dead pixels in the CCD camera one has to define a window to cut the image and to fit the ellipse, the measured size has high sensibility to this window. An agreement needs to be found in order to have reliable emittance values.
Also for fast coupling correction system by using a matrix linear response formalism (only s13 corrected). But residual coupling is found at the IP in some cases where the initial coupling is large. Others methods are under investigation as: correcting all the coupling terms, beam matrix response and non-linear model optimizer.
Work to be done:
- Find an agreement for a reliable beam size measurement.
- Implement 4D emittance algorithm.
- Coupling at IP: coupling sources out of EXT line, new coupling correction algorithm research

9. Instrumentation :
BPM System

10. Instrumentation :
BPM system: Calibration stability

11. Instrumentation :
BPM system: Multibunch studies

12. Instrumentation:
IPBPM preliminary study at the upstream

13. IPBPM: Goals, Status and a Proposal of One Way to Proceed with R&D
Instrumentation :
Required performance for IPBPM system:
For goal 1 need <10nm RMS vertical jitter at IP for IPBSM max resolution
For goal 2 need <2nm resolution
Appropriate location: Where to measure?
R&D requirements
Continued work improving resolution to <2nm
Prove and understand long term stability of high-resolution study and maintainability for non-expert system
Develop “real-time” processing system for use in IP feedback
Many R&D items still required that can be addressed with existing system if can find manpower
IPBPM system very important for Goal 1 and Goal 2 of ATF2. Need more effort in this area.

14. Instrumentation:
IPBSM beam size measurement

15. Instrumentation : IPBSM components status and plans
- Components still needing R&D:
-Laser System
-Transport line
- Detector
- Laser path alignment & control
- Phase monitor
- Profile monitor
- 30 degree fringe
- 174 deg mode laserwire & fringe
- Conclusion:
- Switching to 30 deg mode is considered possible
- Still some components needs commisioning for 174 degree mode & 37 nm

16. ● December data were indispensable to disantangle the
Instrumentation :
Background study
Conclusion
● December data were indispensable to disantangle the
various sources of experimental effets which enter into the background neutron detection
● The analysis in still in progress but :
● CsI or Plastic shielding (front modules) is well understood
● 4.4 m data from dump is unfortunately missing :
– Less spacial effects at 4.4m than 1m
– Also access fast neutrons to understand production
● Modules are now placed to measure FF background

17. - We have recovered from March earthquake
Instrumentation :
FONT status
- We have recovered from March earthquake
- From a ‘cold start’ it takes about 1 hour to get FB running:
basic signal checkout
BPM calibrations
LO phase-shift checks
kicker calibrations
We have an enormous amount of data from December 2011 shifts – analysis just started
- Made significant hardware improvements
- Routinely obtain sub- 0.5 mm BPM resolution
- Re-established FB with better performance
- Instrumented downstream BPMs
- Starting to study/understand jitter propagation

18. Instrumentation : Laser-Wire at the EXT line
•No laserwire signal observed in two shifts (NB nearly half a shift lost for lens replacement access and beam restoration).
•Similar problem as last year – alignment to detector?
•Window 13mm radius, 13mrad angle at LWIP.
•Opening angle of scattered photons ~ 400mrad.
•Estimate of maximum angular offset (from BPMs) additional 500mrad.
•Unclear exactly what the problem is.
•Future plans – check clear line from LWIP to detector with window removed out of running period.
•Detailed numerical work to check if very different beam aspect ratio significantly affects photon flux.
•Improve referencing of laser focus position – OTR screen 300mm thick, comparable to Rayleigh range of laser. Check in more detail where screen obscures laser.
•Full commissioning of OTR to enable beam size tuning and position measurement.
•More detailed work on beam orbit to reduce background to 2010 levels.

19. Highlights Beam Tunning: Summary of Fall 2011 October
h/w & s/w checkouut
OTR upgrades
Magnet mover upgrades
HAPS polarity reverser installation
November
Resumption of ATF2 tuning operations
Joint ATF2/IPBSM ops
ATF2 BBA
OTR commissioning
December
Extracted emittance studies
New coupling correction procedures
ATF2 tuning with IPBSM
Optics &background studies
New s/w
Grid scan

20. Beam Tunning: Issues for Goal 1 Extracted emittance
Fully corrected EXT emittance (charge dependent) ~55pm but ~12pm by DR XSR monitor
Extracted coupling
Very large, often too large to fully correct in EXT
Coupling correction
Are we properly correcting incoming coupling when it is large?
IPBSM backgrounds
Too large when IP vertical beta function <0.5mm
Matching to IP
Good for BX10BY10
Possible bad IP with BX2.5BY5 & BX2.5BY1
Demonstration of IPBSM operation in 30 and 174 degree modes
Robust and fast operation of IPBSM in all modes
Verification of beam jitter at IP
Operation of IPBPM with <10nm resolution
Research and development of IPBSM system
Full documentation of tuning procedure with instructions for use of tuning software and required hardware subsystems.

21. Beam Tunning: EXT tunning
more time is needed for analysis of existing data and simulations (MDW)
EXT setup and maintenance is well understood, relatively fast, and stable
mostly automated procedures … “recipe” for the rest
we have good BBA offset values for most quadrupoles and sextupoles
BPM system (striplines, C-band cavities, S-band cavities, IPBPMs) is working well
multi-OTR system is working well
we’re still plagued with vertical emittance growth between DR and EXT diagnostics section
up to a factor of 10!
appears to be strong x-y coupling ... maybe (at least partly) nonlinear
we have seen emittance measurements (May 2010) from the WS that show virtually no vertical emittance growth from DR to EXT diagnostics section (and no coupling correction required)
no empirical fudge factors required
need to figure out:
how to optimally correct the vertical emittance that we have (QK scan or “quick” methods)
what is causing the observed emittance growth and where does it happen?
are there other coupling sources between EXT diagnostics section and IP?

22. Beam Tunning: EXT tunning Work in progress
coupling measurement / 4D beam reconstruction
revisit emittance measurement and 4D reconstruction simulations
generate coupled beams at all phases (adjust coupling magnitude for εy = pm)
simulate QK scans … can we deduce ε2?
OTR and MSPIP tilt angles vs coupling phase … what should we expect to see?
simulate coupling correction schemes … what works? under what conditions?
and ...

23. Beam Tunning: IP tunning
- In 2010 operation, the minimum beam size was around 300nm
with both 10x10 nominal optics and 1x2.5 Edu’s optics.
- In 2010 December, we checked <xy> and sextupole strengths.
- In 2011 December, the extraction emittance was increased
and the minimum beam size at IP also increased to be around 1um.
We must understand
‐ reason why the present IP beam size was limited to be 1um.
( difference from 2010 operation)
‐ reason why the 2010 IP beam size was limited to be 300nm.

24. - Grid scans has been made at ATF2
Beam Tunning:
Grid scan as lattice diagnostic
Conclusion
- Grid scans has been made at ATF2
- Might be used to determine BPM scale errors
- No evidence of any mismatch
Some BPMs identified with bad scales
Prospects
- Improve scale factor fit method (any suggestions ?)

25. Such an experiment can be proposed.
Beam Tunning:
Waist correction with IPBSM fringe rotation
With a residual tilt in the IP Shintake monitor fringes, the horizontal and vertical sextupole multiknob orthogonality is not significantly broken.
In any case, for any of the optics, having a residual tilt in the fringes still remains a severe problem.
An idea to find out the fringe tilt is to use the αx waist knob and the simulation results show that the vertical beam size depends on it in the presence of fringe tilt.
Such an experiment can be proposed.

26. - Study the long term stability and reproducibility.
Beam Tunning:
Orbit measurement: First attempt
- The agreement between the linear model and the measured R12 and R34 is quite good.
- Some disagreement appears well inside the Final Focus due to the bad calibration of the Final Focus BPMs.
-We have reconstructed the initial jitter and we can see how it acts to the IP beam size.
Future plan
- Study the long term stability and reproducibility.

27. First Goal:
IPBSM: plans and strategy for operational and reliability

28. First Goal:
ATF2 Final Focus Background

29. First Goal: Emittance growth from DR to EXT line
- Quad scan technique should work, but requires multiple iterations to correct fully which has not been done in practice.
- New emittance correction technique to try (model optimiser method)
-Seems to be an improvement over model method
- Also seems in simulation to correct only based on sigma_13 measurement terms
-In contradiction to expectation based on optics layout from MDW talk
-Need to understand why
-Need to generate initial coupled beam macro-particles in more accurate way perhaps
-In any case, simple to try out on beam, just build in switch between different coupling methods in FS interface
- Also different approach from J. Alabau to try
- Installation of s-band TCAVs improves emittance in situations with both coupling and pitched beam

30. First Goal:
Beam tunning strategy
Prioritised Work Plan for next 2 weeks
Try iterative application of sequential quad scan technique
Try new “Model optimiser” single-shot correction method
FFS quad BBA + steering (see if it helps with backgrounds based on PLIC signal + LW detector). Also look for any large BPM-Quad offsets.
With corrected EXT emittance, look again at matching through to IP with BX2.5BY1-9 and see if estimate of IP betax/betay error changes with different lattice configs using MSPIP and PIP WS
Try IP quad-scans and look at emittance that way for comparison with above
Look for strong multipoles using closed bumps across magnets and looking for non-linear response in downstream BPMs

31. First Goal:
Baseline FF optics
FF Glen Optics
2.5 x 1

32. First Goal: Discussion
We agree that in order to get Goal 1 it is necessary to have a dedicated period of time focused only on that activity.
The agreed planning for 2012 is.
- January – March: R&D and checking
- April - June: Training and R&D
- October - December: Goal 1
Notes:
Modification of linac modulators have to be made during summer shutdown, these means that some commissioning has to be made after summer. In order not to interfere with the Goal 1 period the re-starting of the Fall could be made 1or 2 weeks before ( mid Juin – mid September electric power reduction)
After checks in the Ext line some hardware work could be necessary and maybe also some comissioning has to be accorded

33. First Goal: Discussion We agree in the following actions:
Identify the “teachers” for giving the training (G. White, M. Woodley, KEK team…)
List of contents of the training course
Coordinator for teaching and organization of the focus Goal 1 period
Planning group integrated by the responsible of the R&D groups, webex meeting for identify the phd students/postdocs participating in the effort with a face to face meeting before the training period.

34. Second Goal:
IPBPM electronics

35. 11cm Low-Q IP-BPM design study was done, well.
Second Goal:
IPBPM design, production and beam test
Summary
11cm Low-Q IP-BPM design study was done, well.
In the January, New electronics performance test
will be finished after then, the fabrication of two
set of electronics will start.
- 11cm Low-Q IP-BPM performance test will
perform at the end of linac during march.
- 2nm resolution test will start from May to June at
the extraction beam line with IP-Chamber.

36. Second Goal:
IP Chamber Design

37. IP FB loop e- Second Goal: FONT system for IP feedback BPM-kicker
IPBPMs e-
FONT
amplifier
IPBPM
electronics
FONT feedback

38. - Dynamic correction range: Beam y jitter ~ beam size (?)
Second Goal:
FONT system for IP feedback
- Dynamic correction range:
Beam y jitter ~ beam size (?)
3 sigma correction range:
37nm beam  100nm range  200nrad kick
100nm  300nm  600nrad kick
FONT amplifier/kicker provides mrad
Amplifier not matched to new BPM-kicker, but will be more than adequate!
In a 2-bunch train scheme
Latency (120 + X) ns with x< 180ns (bunch spacing 300ns)