15th ATF2 Project Meeting

Large meeting room, 2F, Shokuin-Kaikan (KEK, Japan)

Large meeting room, 2F, Shokuin-Kaikan

KEK, Japan

Toward the first goal, i.e. achievement of 37nm vertical beam size, we would like to focus on two major issues of the wakefield and vertical emittance growth keeping in mind that there are other issues such as multipole fields in the qudrupole magnets, electron/laser beam jitters etc. . The primary goals are identification of sources for the wakefieds and emittance growth and establishment of the mitigations. The meeting place is a large meeting room at the 2nd floor of Shokuin-Kaikan, KEK, which is next to the cafeteria.
Homepage of 15th ATF2 Project Meeting
    • 09:30 10:00
      Convener: Dr Toshiaki Tauchi (KEK)
      • 09:30
        Greeting by the ATF spokesman 10m
        Speaker: Nobuhiro Terunuma (KEK)
      • 09:40
        Brief summary of ATF2 status and the meeting goal 20m
        Speaker: Dr Toshiaki Tauchi (KEK)
        Brief status summary
        meeting goal
    • 10:00 11:00
      Alignment, LINAC and DR
      Convener: Nobuhiro Terunuma (KEK)
      • 10:00
        Status and future plan of LINAC 20m
        Speaker: Mr Takashi Naito (KEK)
      • 10:20
        Status and future plan of DR 20m
        Speaker: Dr Shigeru KURODA (KEK)
      • 10:40
        2012.12.7 earthquake and alignment 20m
        Speaker: Mr Sakae ARAKI (KEK)
    • 11:00 12:30
      Convener: Dr Stewart Boogert (Royal Holloway, University of London)
      • 11:00
        IPBSM 40m
        - upgrades and the performances - beam size measurement, operation at from 2degree to 174 degree
        Speaker: Ms Jacqueline Yan (University of Tokyo)
      • 11:40
        QBPM system 30m
        Speakers: Dr Stewart Boogert (Royal Holloway, University of London), Ms YOUNGIM KIM (Kyungpook National University)
      • 12:10
        M-OTR 20m
        Speaker: Eduardo MARIN LACOMA (SLAC)
    • 12:30 14:00
      Lunch 1h 30m
    • 14:00 14:20
      Recent results of the cavity Compton 20m
      Speaker: Mr Ryuta Tanaka (Hiroshima university)
    • 14:20 16:30
      Major issues and the mitigations (1)

      First Issue is the wakefield.

      Convener: Dr Kiyoshi Kubo (KEK)
      • 14:20
        Cavity BPM Wakefield effect in FF line, comparison with ILC 20m
        Speaker: Dr Kiyoshi Kubo (KEK)
      • 14:40
        Wakefield calculations, experiment results and beam dynamics simulations 40m
        Speaker: Jochem Snuverink (CERN)
      • 15:20
        Effect of wakefield 20m
        Speaker: Dr Glen White (SLAC)
      • 15:40
        Discussion on wakefield 20m
        Summary of wakefield session (Jan. 23 afternoon)

        A, Comparison of Calculation and Experimental Observation

        1, Observed response of downstream orbit change to reference cavity (on mover) position was consistent with calculation.
        Snuverink’s slide 24 said 0.3-0.4V/pC/mm from experiment and 0.21 V/pC/mm from calculation. However, the calculation assumed bunch length 10 mm. Assuming reasonable bunch length, about 7 mm, the calculation would give about 0.32 V/pC/mm.
        See Kubo’s slide 5 too.
        The experiment suggested significant higher order wake (quadrupole field). (See Snuverink’s report)
        Dependence on intensity and bunch length looks reasonable. (See Snuverink’s report)

        2, Observed response of IP beam size to reference cavity (on mover) position was inconsistent with calculation.
        E.g., compare Snuverink’s slide 17 and Kubo’s slide 6: Experiment showed much larger beam size change than calculation.
        It was pointed out that the reference cavity position affected background of IPBSM, which could affect apparent beam size if background subtraction was not properly done. This should be checked carefully.

        3, Wake of cavity BPM cannot explain observed beam size, strong intensity dependence.
        E.g. see White’s slide 6. The expected beam size increase due to cavity BPM wake, based on BPM reading log data is small even for bunch population 1E10 and assuming twice strong wake than calculation.
        Also, the effect of the cavity BPM wake should have been compensated by adjusting the reference cavity position (See Kubo’s slide 6). However we could not observed small beam size with high intensity by scanning the reference cavity position.

        4, Emittance growth in EXT
        Emittance in EXT (measured by OTR system) also depended on intensity but not as strong as IP beam size.
        No dependence on DR RF voltage observed (White's slide 7). Betafunction is relatively small in the upstream part of EXT line. So, wakefield in this part is probably not important.

        5, Further works
        Continue calculation of wake potential of other structures (e.g. vacuum port)
        Check effect of IPBPM wake (including re-calculation of wakepotential)
        Check IPBSM measurement
        - Background dependence
        - Response to non-Gaussian beam, etc.
        More experiment
        - Orbit data with higher intensities
        - If possible more bunch length variation
        - Use CBPM as beam tilt monitor?
        - Normal CBPM on mover for comparison
        More study for ILC BDS and RTML

        B, Possible mitigation of wakefield effect
        Avoid beampipe steps as much as possible
        Larger aperture BPMs or remove BPMs at high beta region
        Centre BPM wrt (quadrupole) magnetic centre
        Second cavity mover at different phase advance (Effective?)
        Steer more through BPM-centresor Wakefield free steering?
        ILC only:
        Wakefield reduced cavity BPM design
        All BPM on movers
        Orbit bumps to correct wakefield upstream

        C, Comparison with ILC BDS and RTML
        Relative effect of wake in ILC BDS and RTML(return line) were compared with ATF EXT/FF. It is very rough and there are many ambiguities, then, no conclusion yet.
      • 16:00
        Study on Multi-pole Field 20m
        Speaker: Dr Toshiyuki Okugi (KEK)
    • 09:30 12:00
      Major issues and the mitigations (2)

      The second issue is the emittance growth.

      Conveners: Mark Woodley (SLAC), Dr Shigeru KURODA (KEK)
      • 09:30
        Status of new Damping Ring laserwire 30m
        Speaker: Arpit Rawankar (Graduate University for Advanced Studies (SOKENDAI))
      • 10:00
        Emittance measurements and related experimental results 30m
        Speaker: Mark Woodley (SLAC)
      • 10:30
        Coupling correction simulation and analysis 30m
        Speaker: Eduardo MARIN LACOMA (SLAC)
      • 11:00
        Turn-by-turn BPM data analysis from the ATF Damping Ring 30m
        Speaker: Yves Renier (CERN)
      • 11:30
        Emittance reconstruction from measured beam sizes 30m
        Speaker: Dr Angeles Faus-Golfe (Instituto de Fisica Corpuscular - Valencia)
    • 12:00 13:30
      Lunch 1h 30m

      Right after the session, we will take the group photograph. So, please wait for a while before the lunch.

    • 13:30 16:10
      15th TB/SGC meeting
      Conveners: Nobuhiro Terunuma (KEK), Philip Bambade (Laboratoire de l''Accelerateur Lineaire (LAL) (IN2P3) (LAL))
      • 13:30
        Cavity Compton status and plan 20m
        Speaker: Dr tsunehiko omori (KEK)
      • 13:50
        ATF2 status and plan 20m
        Speaker: Dr Kiyoshi Kubo (KEK)
      • 14:10
        ATF2 Review by GED-EC 30m
        • Introduction 2m
          Speaker: Kaoru Yokoya (KEK)
        • Motivation and charge of the review 10m
          Speaker: Dr Marc Ross (SLAC)
      • 14:40
        LW status and plan 20m
        Presented by Laurie Nevay
        Speaker: Dr Laurence Nevay (Oxford university)
      • 15:00
        FONT status and plan 20m
        Speaker: Prof. Philip Burrows (Oxford University)
    • 16:30 17:00
      4:30 meeting on the ATF operation and shifts
      Convener: Dr Shigeru KURODA (KEK)
    • 09:30 11:30
      Towards the first goal

      summary of wakefield and emittance growth sessions
      further discussion

      Conveners: Dr Glen White (SLAC), Dr Toshiyuki Okugi (KEK)
      • 09:30
        Beam jitter studies 20m
        Speaker: Juergen Pfingstner (Technische Universitaet Graz)
      • 09:50
        Orbit analysis 20m
        Speaker: Dr YOUNGIM KIM (University of Oxford)
      • 10:10
        Report from "ATF2 Operators" 20m
        Speaker: Dr Laura Corner (JAI, Oxford University)
      • 10:30
        Summary of present issues for Goal 1 and plans going forward 20m
        Speaker: Dr Glen White (SLAC)
        • List of the mitigation plan ( Draft ) 5m
          It is based on our discussion for last 2 days.
          Speaker: Dr Toshiaki Tauchi (KEK)
    • 12:00 13:30
      Lunch 1h 30m
    • 14:30 15:00
      ATF Operation meeting
    • 15:00 15:50
      Discussion on plans in 2013
      • 15:00
        Summary of the discussion 50m
        Speaker: Dr Kiyoshi Kubo (KEK)
        plans in 2013
    • 15:50 16:00
      Coffee break 10m

      ..preparing and expecting nice food with coffee, tea and drinks

    • 16:00 17:30
      Status for the 2nd goal preparation
      Convener: Philip Bambade (Laboratoire de l''Accelerateur Lineaire (LAL) (IN2P3) (LAL))
    • 18:20 20:30