Minutes of 83rd FFIR/BDSIM and 6th ILC-Asia WG4 meeting on 11/2/2004

The 6th meeting was held on Nov.2 10:00 am at rm.425 bldg no.3.

Discussion on slides prepared for 1st ILC WS.

(1) gamma-gamma options (Takahashi)
       *  Need to study whether e+e- and gamma-gamma are fully compatible.
       *  Most important issues : crossing angle, beam dump, laser & optics.
       * disrupted beam needs large crossing angle ~30mrad.
       *  Angular spread of photon beam is as small as few tens of micro radian.
          We need a beam dump for such an well collimated photon beam.
       *  gamma could be scattered by 3-5 atm. Ar gas
       *  back scatter neutron from beam dump could be a serious problem.
       *  We may need special beam dump for gamma-gamma, which can not be used for e+e- .
       *  Need R&D to evaluate the cost of laser system. It is not clear cavity system is cheeper.
       *  Optical cavity will increase laser power and enable recycling for multi-bunch collision.
       *  Need to establish mirror controlling method and cavity system.
       *  Radiation pressure might destroy laser phase coherence.
       *  Many R&D issues.
       *  We'd like to demonstrate laser-e collision to produce gamma beam at ATF2.
       *  Add R&D items and place.

(2) Final Doublet (Mihara)
       *  Possible technology for Final Doublet: Normal/Super/Permanent.
       *  Normal E-M Q is established. Large power consumption.
       *  Super E-M Q produces high focusing power.
          -> short final doublet, large bore. Opposite beam will pass inside the bore.
          BNNL reports liquid He flow might produce small vibration of ~micron (Sugahara).
       *  Permanent mag. Q is compact and consumes less power.
          No clear data on radiation and temperature damage.
       *  Some data on radiation damage taken at KEK-PS is becoming public from Kawakubo-san.
          (Also from SPring-8 --EPAC)
       *  It is unclear we can get enough data before KEK-PS shutdown.
       *  For a detailed evaluation of radiation tolerance,
          radiation species at IP should be known.
       *  "Catalogue spec" is useful to estimate temperature tolerance.
          Long--period drift was observed which is not related to temperature.
       *  We need designs with Normal/Super/Permanent technologies to propose  L* & Xing angle.
 Discussion
       *  Field adjust system makes permanent magnet system not so compact.
       *  Permanent magnet can be utilized even in 7mrad crossing with a slit.
          Hybrid type (Permanent + Normal) will be realistic.

 In ILC-WS
       *  List of merits and demerits in Normal/Super/Permanent.
       *  List of R&D issues.

(3) Critical Beam Test (Kuroda)
       *  ATF2 Goal
          (1) Demonstration of compact FF system
          (2) Demonstration of controlling beam jitter at nano m level at IP
              with active mover and feedback (not demonstrated FFTB/SLAC)
       *  ATF2 will have a similar local correction to that of GLC/NLC
       *  Need to recalculate vibration tolerance.
       *  Alignment tolerance is loose.
       *  Need to evaluate an effect of small rotation (<<0.1mrad).
       *  Tolerance at ATF2 is similar to that of ILC, except for vibration tolerance of Final Doublet.
          The vibration of Final Doublet will be checked by nano-BPM at IP .
       *  FFTB has a serious problem of beam orbit vibration.
          We will install nona-BPM to measure beam position at IP and active mover for final Q.
       *  Laser Facility is a important option
       *  TESLA-like beam will be available with an improved Kicker.

(4) IR Layout: Crossing Angle, L* and Vertex R
       *  Head-on, vertical 0.3mrad, horizonntal 2mrad/7mrad/20mrad の紹介。
       *  crossing angle and L* will be decided by taking into account the following:
          - Final Q
          - hot spot
          - Vertex R
          - Extraction Line
          - detector
          - SR background
       * Table of crossing angle. We have many items to discuss.

The next meeting will be on 2 November, 2004,10:00 - at 3 gokan, 425 .