Summary on WG 2 LINAC Technology

Discussion on Technical issues Definition of work package leaders Work package leaders will be contacted by L. Lilje next week Lutz Lilje DESY 19.11.2018

Program Danilo Barni Module, Tuner (20 min) AFTERNOON session (Coffe Break 16.00) Add. information available on request by: Leaks in tests - Detlef Reschke Cleanroom Quality control - Axel Matheisen Flange designs - Kirsten Zapfe Coupler Design and Processing - Terry Garvey / W.-D. Moeller HOM and Pickup - Wolf-Dietrich Moeller Experience Module Assembly Rolf Lange Active tuning - Lutz Lilje/Stefan Simrock Priority and effort estimation, definition of Work packages Presentation of itemized priority list - L.Lilje / D.Reschke (20 min) Discussion on estimation of the effort needed to address technical issues and priority ranking Definition of Work packages Discussion : Distribution of Work packages Preparation of the Summary MORNING session R&D Session 9.00-10.00 H. Padamsee DESY EP single cell cavity sent to Cornell - various treatments and results – (20min) H. Padamsee 550 RRR russian Nb single cell cavity high gradients results with thermometry– (20min) L. Lilje High gradients in TESLA nine-cell cavities – (20min) General Talk 10.00-11.20. (coffee break) Paolo Pierini - Design consideration for accelerator reliability (30 min) Cristian Magne Cold BPM - (30 min) Overview technical issues related to superconducting accelerating modules 11.20-12.00 Lutz Lilje String, Cavities, Coupler, HOM , Clean room assembly - (40 min) Lutz Lilje DESY 19.11.2018

L. Lilje High power test Piezo compensation Lutz Lilje DESY 19.11.2018

High Power Test of an EP nine-cell cavity Calib. Measurement HERA plant High Power Test of an EP nine-cell cavity 5 Hz, 500 us fill, 800us flat-top Feed-forward only No piezo compensation at the moment 33-35 MV/m with no interruption related to cavity-coupler-klystron since more than 130 hours 2 cryo problems at 95 and 130 hours resulting from connection to the HERA plant Cryo shutdown right now due to problem of impurities in He circuit (from HERA plant) (scheduled calibration measurement at 65 hours shown in the plot) Very low activity in the high power coupler, temperature levels o.k. for 5 Hz No field emission observable Lutz Lilje DESY 19.11.2018

Frequency stabilization at 35 MV/m Blue: With piezo Red: Without piezo Frequency detuning of ~1000 Hz compensated with resonant excitation of a mechanical cavity resonance at 230 Hz. NOTE: This is rather an demonstration of the capability of active tuning. Application in a real machine is probably difficult/impossible. Lutz Lilje DESY 19.11.2018

Hassan Padamsee RF Critical field of niobium ‘In-situ’ Bakeout Lutz Lilje DESY 19.11.2018

Lutz Lilje DESY 19.11.2018

Cornell Results Lutz Lilje DESY 19.11.2018

P. Pierini Reliability Bottom-up approach is more reasonable than Top-down (complexity generates wrong results) Lutz Lilje DESY 19.11.2018

Warning/2 Formal mathematical and statistical methods can be applied to measure and assess reliability characteristics of components, but the associated uncertainties are high, leading to reliability estimates with limited credibility “(...) the role of mathematical and statistical methods in reliability engineering is limited, and appreciation of the uncertainty is important in order to minimize the chances of performing inappropriate analysis and of generating misleading results. (…) practical engineering must take precedence in determining the causes of problems and their solutions” [PDT O’Connor] 11/19/2018 Lutz Lilje DESY

However… There exist design principles to achieve a reliable system: Derating: Operate components below max rating Redundancy: Provide more components with a given function Fault Tolerance: Component failure do not imply system failure Mathematical and statistical methods for reliability assessment teach us that the reliability of a complex system depends not only by the component specifications (MTBF/MTTR), but also, even more importantly, by the logical and functional connections (role of redundancies and spares) In other words, proper planning of redundancies allows building reliable systems out of moderately reliable components 11/19/2018 Lutz Lilje DESY

C. Magne Cold BPM design Dark current monitor Resolution needed for cavity dark current 100 nA? Lutz Lilje DESY 19.11.2018

Cold BPM for TTF2 Tesla prototype - low beam impedance cooling to 2K without strain - Low beam coupling impedance: reduces the beam break-up forces and minimizes the cryogenic heat-load due to resonances. - The (axial) geometry is favorable to cooling to 2K without strain. - The dimensions are small. - The design is adapted to UHV dust-free conditions. - The mechanics is relatively simple to machine (latheprecision of axial sym.) Ability to measure sum signal and dark current Lutz Lilje DESY 19.11.2018

Dark Current Monitor – laboratory test Fmono= 1.3 GHz Fdip = 2.6 GHz   An aluminium prototype has been fabricated to study the optimum antenna design. - Network analyser - testbench Alu prototype Electronics (analog): - One unit (refurbished) is avalaible - Need to build 1 (or 2?) more Lutz Lilje DESY 19.11.2018

Discussion on technical issues Leaks in tests - Detlef Reschke Flange designs - Kirsten Zapfe Cleanroom Quality control - Axel Matheisen Coupler Design and Processing - Terry Garvey / W.-D. Moeller HOM and Pickup - Wolf-Dietrich Moeller Experience Module Assembly Rolf Lange Active tuning - Lutz Lilje/Stefan Simrock TESLA MEETING 26-28 May 2003 Frascati LINAC TECHNOLOGY WORKING GROUP

Work package list Lutz Lilje DESY 19.11.2018

Work group leader tasks Initiate decision-making process Make a detailed list/ programme as soon as possible Estimation of time required and effort to do this (money, manpower) List of open questions Prepare status report for end of August Report will be made available preferrable through EDMS (Instructions will be send by Axel Matheisen asap) Discussion during next TESLA Meeting Lutz Lilje DESY 19.11.2018

Thanks to all contributors for the very useful discussion and the will to take over the work !!!! Lutz Lilje DESY 19.11.2018