The technology decision took place The ITRP made clear

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2 The technology decision took place The ITRP made clear It s not a design choice TESLA design to be revisited International Collaboration needed NOW! SRF technology is considered more robust, but: 1 TeV is desirable R&D effort should be made to realize this Lutz Lilje DESY -MPY-

3 Review recent developments in the area of superconducting RF cavities Developments in the North America and Asia Information sources Workshops Pushing the Limits of RF Superconductivity, Argonne, September 2004 SMTF (Superconducting Cryo-Module Test Facility) Workshop, JLab, September 2004 ILC-Americas Workshop, SLAC, October 2004» project.slac.stanford.edu/ilc/meetings/workshops/us- ILCWorkshop/workshop.html WWW page of Asian WG 5» And talk by N. Toge at SMTF Workshop Lutz Lilje DESY -MPY-

4 Summary of the Pushing the Limits of RF Superconductivity Workshop (Argonne 2004) Lutz DESY ANL 2004 New Results Personal views ~50 people mainly the usual suspects Notable exception: University of Wisconsin

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6 M. Liepe made a good intro to the hot topics K. Saito: Fundamental critical field is reached at 45 MV/m Discussion: Considered not to be the final answer Proposed scheme for ILC New cavity shape similar to new Low-loss JLab-design (as proposed by J. Sekutowicz et al.) As cell-to-cell coupling is smaller use 2x8 superstructures Lutz Lilje DESY -MPY-

7 Basic message: For high gradient applications there is only some faint hope (longterm!) Nb/Cu thin films have their well-known applications: Low gradient Low frequency Nb 3 Sn Low/medium gradient at 4K No new development since years Other (includes MgB 2 ) Still rather material science Still difficult to imagine real cavities Lutz Lilje DESY -MPY-

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9 Low-loss (JLab, Jacek) reduce Hpeak/Eacc by 10 % Smaller iris High-gradient (JLab, Jacek) Reduce Epeak/Eacc by 5% Re-entrant (Cornell) reduce Hpeak/Eacc by 10 % How to clean a multi-cell? Stiffness and tuning? Successful single-cell tests Lutz Lilje DESY -MPY-

10 Example: CEBAF upgrade high-gradient operation (HG): lower E surf reduce field emission low-loss (LL) maximize shunt impedance and geometric factor with a given cryo power maximise achievable gradient J. Sekutowicz, P. Kneisel, et.al. This conference. Lutz Lilje DESY -MPY- Ø equator Parameter OC HG LL Ø equator [mm] Ø iris [mm] * k cc [%] E peak /E acc [-] B peak /E acc [mt/(mv/m) R/Q [O] G [O] R/Q G [O O] Ø iris

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12 Excerpt from Contributed Talks to the Argonne Workshop New SRF Cavity Geometry for High-Current Applications -- Ilan Ben-Zvi, BNL Measuring Critical RF Fields of Superconductors Using High Power Short Pulses in X Band -- Isidoro Campisi, ORNL/SNS Pushing the Limits of the SRF Technology for Low- and Medium-Velocity Applications -- Jean Delayen, JLab Reentrant Cavity and First Test Result -- Rong-Li Geng, Cornell U. A Theoretical Overview of Multiscale Mechanisms of RF Superconductivity Breakdown -- Alex Gurevich, U. of Wisconsin-Madison Fabrication and Performance of Improved Cavity Shapes for 12 GeV CEBAF - - Charles Reece, JLab Niobium Copper Clad Cavities -- Waldemar Singer, DESY LANL Activity on New Materials -- Tsuyoshi Tajima, LANL Thin Film Coatings for RF Superconductivity -- Genfa Wu, JLab Lutz Lilje DESY -MPY-

13 Alex Gurevich, U. of Wisconsin-Madison Lutz Lilje DESY -MPY-

14 Q-slopes, Q-drops, Surface Studies Field emission is an important limitation There was no real discussion on this Effort is insufficient! Q-drop without X-rays is an limitation Recipe exists, we are still lacking some understanding Bakeout does help, but why?» Impurity diffusion of oxygen? EP and bake gives the best and most reproducible results Susceptibility measurements on samples» Bc3 shows strong changes dependent on surface preperation Discussion on models, theories and experiments Surface studies concentrate on oxygen impurities Can the surface topology play a role? Lutz Lilje DESY -MPY-

15 Surface treatment does not change the bulk properties e.g. B c and B c2 EP vs. BCP Baking Lutz Lilje DESY -MPY-

16 Example: Temperature dependence of B c3 for an etched sample Susceptibility Measurements: B c3 Surface critical field B c3 depends on surface preparation Lutz Lilje DESY -MPY-

17 17 Q-Slope Fit Slope before baking ( EP BCP ) Slope Improvement after baking No change after 2 m. air exposure Slope after baking ( EP < BCP ) Exceptional Results ( BCP ) Quench ( EP > BCP ) BCP Quench unchanged after baking 1E+11 1E+11 Q 0 C1-05 ( BCP cavity ) Q 0 1E+10 1E+10 1E+09 C1-03 / S-3 ( EP cavity ) KEK 9 & 10 no baking 110 C / 30h RF power limitation quench E acc ( MV/m ) 1E+09 1E+08 no baking 90 C - 48h 110 C - 48h quench E acc ( MV/m ) 1E+12 Q 0 Q-slopes before baking ( BCP and EP cavities ) 1E+11 D1-22 ( EP cavity ) 1E+11 Q 0 1E+12 1E+10 Q 0 1E+10 1E+09 C1-03 / S-3 ( EP - KEK 9 ) D1-22 ( EP - Saclay A1 ) C1-15 ( BCP - Saclay I1 ) C1-16 ( BCP - Saclay P1 ) C1-10 ( BCP - Saclay N1 ) RF Power Limit E acc (MV/m) 1E+09 1E+08 A1 - no baking A2 - baking in situ 100 C /48h A7 - air exposure 1day + HPR A10 - air exposure 2month + HPR quench E acc ( MV/m ) 1E+11 1E+10 1E+09 C1-03 / S-3 ( EP - KEK 10 ) C1-15 ( BCP - Saclay I2 ) C1-16 ( BCP - Saclay P2 ) Quench E acc (MV/m) SRF 2003 ( 11 th Workshop ) Q-Slope at High Gradients Bernard Visentin

18 Similarities EP / BCP Q-Slope Fit Slope before baking ( EP BCP ) Slope Improvement after baking Slope after baking ( EP < BCP ) No change after 2 m. air exposure Exceptional Results ( BCP ) Quench ( EP > BCP ) BCP Quench unchanged after baking Validity Magnetic Field Y N Enhancement ( β m et H C ) Interface Tunnel Exchange Thermal Feedback Magnetic Field Dependence of D Y ( E 8 ) N ( β ) Y ( H C ) Y ( Nb 2 O 5-y ) Y ( β m < ; H C - N > ) ( high β m ) Y ( low β ) N ( Nb 2 O 5-y ) Y ( β m < ; H C > ) N ( H C ) Y N ( high β ) - - Y Y Y Y ( parab. ) ( R BCS R res N - N - - N ) ( coeff. C ) Y ( expon. ) N ( H C ) Segregation of Impurities - N ( segreg. ) Y ( H C ) Y ( H C - N - - N > ) ( thin film ) N - - Y - - Y ( only O ) ( cleaning ) Bernard Visentin

19 Excerpt from Contributed Talks to Argonne Workshop Measurements of the High Field Q-Drop in TE011/TM010 Mode in a Single Cell Cavity -- Gianluigi Ciovati, Jlab Processing Techniques and Recent Results for SC Drift- Tube Cavities -- Michael Kelly, ANL An Investigation of the Properties of Grain Boundaries in BCP Nb for SRF Cavities -- Peter Lee, U. of Wisconsin- Madison and Pierre Bauer, FNAL Q-Slope and Related Surface Analysis Results from Cornell -- Hasan Padamsee, Cornell U. Low, Medium, High Field Q-Slopes Change with Surface Treatments -- Bernard Visentin, CEA-Saclay Lutz Lilje DESY -MPY-

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26 Difficult to correlate surface studies with real cavity preparations Lack of measurements of the superconducting parameters e.g. penetration depth, susceptibility Sample studies insuffcient Emphasis on project-related work results in lack of R&D on SRF basics, field emission, Q- slope, etc. Lutz Lilje DESY -MPY-

27 A lot of presentations Lack of discussion esp. on field emission No real planning for experiments or distribution of work ILC issues not directly discussed What would be the best manufacturing process, preparation etc.? Lutz Lilje DESY -MPY-

28 Much more focused on Linac technology issues Set up a scoring chart for all items Already very detailed discussion Definitely to be discussed in Japan, e.g. top ratings for: Vibrations on quad etc. Vacuum seals as top rating (5 = alternative ideas needed/ 4= significant concern) Tuner as a reliability issue» Very difficult to be accessed in the current design Niobium scanning (4 = really needs work) Relatively low ratings for High pressure rinsing only 3 = optimization needed Superstructure and traveling wave structure as options Detailed discussion later Lutz Lilje DESY -MPY-

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32 Two perspectives: Nobu Toge There is strong push by K. Saito towards the 45 MV/m Open issues: Need to settle the 35 MV/m first Must not forget the quality control esp. for field emission Should the R&D change every preparation step from scratch? Lutz Lilje DESY -MPY-

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39 K. Saito, ILC-ASIA, All-hands meeting, Lutz Lilje DESY -MPY-

40 K. Saito, ILC-ASIA, All-hands meeting, Lutz Lilje DESY -MPY-

41 Lutz Lilje DESY -MPY- K. Saito, ILC-ASIA, All-hands meeting,

42 A lot of ideas but what is relevant? To judge the R&D issues it is important to look at the ILC timeline Stolen fom Nick Walker Lutz Lilje DESY -MPY-

43 ILC Projected Time Line International Funding CDR GDI process TDR construction commissioning physics site selection EUROTeV Very aggressive!

44 We should be prepared to rate R&D issues the more detailed categories from ILC-Americas are useful Detailed discussion of the rankings given now Need to establish a baseline for necessary R&D from a european perspective Even with the push towards higher gradient (45 MV/m) we need to finish the work for 35 MV/m modules Synergy with the European XFEL» Industrialization» Quality control Different for XFEL E.g.» Short nine-cells» Tuner» Time for basic R&D (includes material science) Lutz Lilje DESY -MPY-

45 Need to re-adjust the deliverables ILC schedule is tight Some options will not be available until CDR and TDR (e.g. thin films) Support for the ILC Exchange of information to help the GDI (Global Design Initiative) to start the design process Help with CDR and TDR Focus on system reliability (Review of the status) Accelerating modules Production reliability Nb quality Quality control procedures Lutz Lilje DESY -MPY-