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

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

11-13 January 13th ATF2 Project meeting

Alignment and DR: Optics in DR

- 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.

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-

Alignment and DR: DR emittance

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

Instrumentation : BPM System

Instrumentation : BPM system: Calibration stability

Instrumentation : BPM system: Multibunch studies

Instrumentation: IPBPM preliminary study at the upstream

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.

Instrumentation: IPBSM beam size measurement

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

● 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

- 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

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.

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

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 mismatch @ 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.

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?

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 = 60-100 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 ...

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.

- 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 ?)

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.

- 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.

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

First Goal: ATF2 Final Focus Background

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

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

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

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

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.

Second Goal: IPBPM electronics

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.

Second Goal: IP Chamber Design

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

- 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 +- 50 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)