1. General remarks: I am impressed with the quantity and quality of the work presented here and the functioning of the organization. I thank ILC and FNAL for their hospitality. The ART is off to a good start with a strong R&D program. Summary – Ilan Ben-Zvi, BNL

2. SRF Cavity and cavity test facility issues: Major R&D issue: Cavity gradient to achieve 35 MV/m and its reproducibility. This effort should be strongly supported. This requires both processing facility and testing facilities (vertical and horizontal). These facilities should be pursued on the fastest possible time scale. Multiple R&D facilities, distributed around the country, increase necessary throughput and tap best expertise in various laboratories. In the longer run, a pre-production facility should be built at one place for high-volume processing and testing. DESY TTF is becoming unavailable for ILC cavity development since they do not need to push the gradient. ILCTA is needed to do ILC baseline cavity development while supporting alternate designs and materials.

3. SRF Cavity and cavity test facility issues (Cont.): Designs for cryomodules are coordinated internationally. It is important to coordinate internationally also the compatibility of cavity design, tuner and coupler. Superstructures R&D is an important potential cost saver and work should continue. Adjustability of power to individual cavities can increase the average gradient. The right range of adjustability is not clear at this time due to current large variation. What is the effect of trapped modes? Specification was developed for Q*R/Q. However, it is not clear if this spec is met by the cavity. The “Tight Loop” scheme is excellent, however - One needs to collect very detailed information from just about every system and every phase of the work. Vertical test system: Consider higher power, pulsed RF source.

4. Source issues: Electrons: The laser is a critical element in photocathode sources. ILC poses large increase:SLC: 360 pps, ILC: 15000 pps of ~same pulse energy ILC laser is different than existing lasers, e.g. TTF laser or commercial designs. Laser development is time consuming. Reliability of the laser is a huge issue for ILC even with redundancy. but each needs to be more reliable than commercial products. Conclusion: It is important to get going vigorously on laser R&D. Corollary: Need to continue cathode research – improve QE, polarization. Current R&D is a low level effort but unique. Superlattices, new materials (GaN). Higher voltage DC gun design would help provide operational headroom. NC RF gun – desirable on account of savings in various places: HV, bunching, damping ring. I am pessimistic about vacuum level achievable in NC gun (leading to chemical poisoning, ion bombardment).

5. Positrons: This is a challenging task. Must do Adiabatic Matching Device to focus positrons off the target (7 Tesla… but 40% collection improvement) Undulator needs R&D since the combination of pitch, field and bore is difficult. It is a very long device too. Target looks doable but system needs lot of engineering and prototyping. Compton scattering source (another promising yet challenging approach) is under development in KEK – good division of tasks between regions.

6. Test facilities (ILCTA covered above): Test facilities are obviously extremely valuable: TTF, ATF, ATF2, ILCTA and CESR. TTF and ATF are resource limited. TTF has 20% availability which is not used. There is need for a support and coordination effort to make best use of resources. This is an interregional issue but it is important to ART. I propose the establishment of a team of ILC people to carry out this work. Target of opportunity: Use the SNS linac to get operational experience with SRF linac of some comparable properties. Instrumentation development is a great way to do R&D, in particular by university people, who would also train students and do good science at the same time. For bid-to-host, ILCTA and damping ring R&D needed in the USA.

7. Damping ring: The design of the DR is solid. However, there are challenging issues of small emittance and appropriate instrumentation. The ATF serves the ILC well with international participation. It would be valuable to add the Cornell SR to the list. Electron cloud simulations should be benchmarked in a test facility. RF test facility: RFTF is a valuable objective due to large value share of RF systems. Development of Marx modulators, which is under way, is critical. 10 MW, high-efficiency Klystron development must be pursued vigorously. RF distribution has potential improvements and is also a subject to industrialization.