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.