HOM Coupler Development for SPL U. van Rienen - H.-W. Glock Universität Rostock - Institut für Allgemeine Elektrotechnik 4th SPL Collaboration Meeting jointly with ESS 30.6.-2.7.2010 Lund 1.7.2010 1.7.2010 © 2010 UNIVERSITÄT ROSTOCK | FAKULTÄT INFORMATIK UND ELEKTROTECHNIK

... coaxial couplers without fundamental mode filter HOM coupler for SPL - β=1 cavity needed, better than ... ... coaxial couplers without fundamental mode filter 1.7.2010 © 2010 UNIVERSITÄT ROSTOCK | FAKULTÄT INFORMATIK UND ELEKTROTECHNIK U. van Rienen – H.-W. Glock 2

Given coupler design limitations Orientation and longitudinal position fixed (cavity construction efforts, space needed for tuner, ...) (Inner) diameter (max.) 36 mm Same design on both sides of the cavity (De)mountable, not welded 23/02/2010 3 1.7.2010 © 2010 UNIVERSITÄT ROSTOCK | FAKULTÄT INFORMATIK UND ELEKTROTECHNIK U. van Rienen – H.-W. Glock 3

"Classical" LEP hook design as starting point coaxial 50-Ohm-port (connector not modeled) adjustable capacitive coupling combined E-/H-field coupling, capacity couples to outer conductor support carries liquid helium 1.7.2010 © 2010 UNIVERSITÄT ROSTOCK | FAKULTÄT INFORMATIK UND ELEKTROTECHNIK U. van Rienen – H.-W. Glock 4

Free design parameters original picture taken from (courtesy W. Weingarten): E. Haebel, “Couplers for cavities,” CERN Accelerator School: Superconductivity in Particle Accelerators, Hamburg, Germany, May 1995, p. 231 ff 1.7.2010 © 2010 UNIVERSITÄT ROSTOCK | FAKULTÄT INFORMATIK UND ELEKTROTECHNIK U. van Rienen – H.-W. Glock 5

Free design parameters – electrodynamical CAE ~ 20 adjustable parameters CSTStudio© ver 2009/2010 1.7.2010 © 2010 UNIVERSITÄT ROSTOCK | FAKULTÄT INFORMATIK UND ELEKTROTECHNIK U. van Rienen – H.-W. Glock 6

Free design parameters – examples 1.7.2010 © 2010 UNIVERSITÄT ROSTOCK | FAKULTÄT INFORMATIK UND ELEKTROTECHNIK U. van Rienen – H.-W. Glock 7

Waveguide-Coax-Transmission used to assess coupling connection to external dump coax waveguide connection to cavity: TE11 – horizontal TE11 – vertical TM01 (esp. facc !) TE21 – pol. 1 TE21 – pol. 2 ... 1.7.2010 © 2010 UNIVERSITÄT ROSTOCK | FAKULTÄT INFORMATIK UND ELEKTROTECHNIK U. van Rienen – H.-W. Glock 8

Waveguide-Coax-Transmission used to assess coupling –. e. g Waveguide-Coax-Transmission used to assess coupling – e.g. example geometry - dependence on hook rotation 60° good compromise for both polarizations coax - TE11: E par. coupler coax - TE11: E ortho. coupler 1.7.2010 © 2010 UNIVERSITÄT ROSTOCK | FAKULTÄT INFORMATIK UND ELEKTROTECHNIK U. van Rienen – H.-W. Glock 9

coax - TM01 (couples to fund. mode) Fundamental mode rejection – e.g. example geometry - dependence on hook rotation coax - TM01 (couples to fund. mode) minimum of transmission occurs, but not at 704 MHz – to be tuned ! 1.7.2010 © 2010 UNIVERSITÄT ROSTOCK | FAKULTÄT INFORMATIK UND ELEKTROTECHNIK U. van Rienen – H.-W. Glock 10

Field distributions give hints for design –. e. g Field distributions give hints for design – e.g. example geometry – E-field geometry @ 704 MHz strong capacitive coupling between "hook" and outer conductor => depends directly on "hook" length 1.7.2010 © 2010 UNIVERSITÄT ROSTOCK | FAKULTÄT INFORMATIK UND ELEKTROTECHNIK U. van Rienen – H.-W. Glock 11

Status and plan Description of fully parameterized coupler geometry available Many (~20) degrees of freedom to be taken into consideration Primary design criterion: notch filter to be tuned for fundamental mode frequency Combination with cavity (as done for coaxial couplers), Q-determination with pole fitting algorithm Further optimization according polarization sensitivity (mainly TE11, TM11) ... ... Current density / loss density ... ... and further constructive aspects (cooling, manufacturing) 1.7.2010 © 2010 UNIVERSITÄT ROSTOCK | FAKULTÄT INFORMATIK UND ELEKTROTECHNIK U. van Rienen – H.-W. Glock 12

Some news regarding ESS and University of Rostock: 1.7.2010 © 2010 UNIVERSITÄT ROSTOCK | FAKULTÄT INFORMATIK UND ELEKTROTECHNIK U. van Rienen – H.-W. Glock 13

CERN-SPL*-Study, EUCARD**, DoHRo*** @ Rostock HOM damping design for CERN-SPL-Study EUCARD** – WP 10.5.3: HOM distribution and geometrical dependencies (FLASH-1.3, FLASH-3.9, XFEL(?)) needed for HOM coupler signal based beam analysis DoHRo*** – HOM: WP 1: HOM damping design for BERLINPRO WP 2: HOM damping design for ESS – high energy part of p-linac WP 3: Simplified electronics for HOM coupler signal based beam analysis *CERN-SPL: "Design of HOM-Damping for CERN-SPL“; funded by German Federal Ministry of Research+Education, Project: 05H09HR5 **EUCARD: EU FP7 Research Infrastructure Grant No. 227579 ***DoHRo: Dortmund-HZB-Rostock – "Innovative Technologien und Komponenten zukünftiger Teilchenbeschleuniger in Strahlungsquellen, funding approved by German Federal Ministry of Research+Education, Project: 05K10HRC 1.7.2010 © 2010 UNIVERSITÄT ROSTOCK | FAKULTÄT INFORMATIK UND ELEKTROTECHNIK U. van Rienen – H.-W. Glock 14

CERN-SPL*-Study, EUCARD**, DoHRo*** @ Rostock Staff (% of FTE): Funding: Prof. Dr. Ursula van Rienen ( ~ 5%) Dr. Dirk Hecht (administrative; now ~ 5%) Dipl.-Ing. Thomas Flisgen (80% EUCARD**, 20% teaching) Rostock University Dr. Hans-Walter Glock 50% CERN-SPL* 25% EUCARD** 25% DoHRo*** Dipl.-Ing. Mirjana Ivanovska (50%, on pregnancy leave till Oct`10) Dipl.-Phys. Tomasz Galek (100%, Oct.`09 - Jan.`10, 50% July`10 – Dez`10) N.N.-PhD: (50%) CERN-SPL* Dr. Carsten Potratz (100%, from July`10) DoHRo*** *CERN-SPL: "Design of HOM-Damping for CERN-SPL“; funded by German Federal Ministry of Research+Education, Project: 05H09HR5 **EUCARD: EU FP7 Research Infrastructure Grant No. 227579 ***DoHRo: Dortmund-HZB-Rostock – "Innovative Technologien und Komponenten zukünftiger Teilchenbeschleuniger in Strahlungsquellen, funding approved by German Federal Ministry of Research+Education, Project: 05K10HRC 1.7.2010 © 2010 UNIVERSITÄT ROSTOCK | FAKULTÄT INFORMATIK UND ELEKTROTECHNIK U. van Rienen – H.-W. Glock 15

Thank you for your attention. 1.7.2010 © 2010 UNIVERSITÄT ROSTOCK | FAKULTÄT INFORMATIK UND ELEKTROTECHNIK U. van Rienen – H.-W. Glock 16

Additional stuff: - solver overview - CSC principle - pole identification - Q-determination for coaxial couplers 1.7.2010 © 2010 UNIVERSITÄT ROSTOCK | FAKULTÄT INFORMATIK UND ELEKTROTECHNIK H.-W. Glock - Thomas Flisgen 17

Used Methods for S-Parameter-Calculation (updated) Transient Solver Hexahedral Grid Frequency Solver Hexahedral Grid Frequency Solver Tetrahedral Grid Fast Resonant Solver Hexahedral Grid Broadband computation of S- Parameters via FFT. Weak coupling between orthogonal modes in rotational symmetric structures. Many time steps are needed to reach steady state due to large time constants. S-Parameters do not show the notch effect of HOM coupler in a reasonable manner. Appropriate for structures with high quality factors. Weak coupling between orthogonal modes in rotational symmetric structures. Long computational time, because each S-Matrix has to be computed for every frequency sample. Very dense mesh is needed for HOM coupler. Appropriate for structures with high quality factors. Less number of unknowns is needed to describe HOM coupler Fast solver available for tetrahedral grids. Appropriate both for structures with high quality factors and coupler-like set-ups. Weak coupling between orthogonal modes in rotational symmetric structures. Really fast Pro Strong artificial coupling between orthogonal modes in rotational symmetric structures (e.g. cavity), due to non symmetric grid. corrected both with a posteriori transformation and software update Contra Significant violation of unitarity of S- matrices below cut-off 04/08/2010 © 2010 UNIVERSITÄT ROSTOCK | FAKULTÄT INFORMATIK UND ELEKTROTECHNIK H.-W. Glock - Thomas Flisgen 18 18

Concatenation procedure based on scattering properties: Coupled S-Parameter Computation = CSC Split structure in sections Compute scattering (S-) parameters of all sections individually with appropriate solvers Compute overall S-parameters as function of f with special algorithm*, applicable to any structure topology and mode number Derive loaded Q-values from S-parameter spectra *: e.g.: H.-W. Glock, K. Rothemund, U. van Rienen: "CSC - A System for Coupled S-Parameter Calculations", TESLA-Report 2001-25 or K. Rothemund, H.-W. Glock, U. van Rienen: "Eigenmode Calculation of Complex RF-Structures using S- Parameters", IEEE Transactions on Magnetics, Vol. 36, (2000): 1501-1503 and references therein 04/08/2010 © 2010 UNIVERSITÄT ROSTOCK | FAKULTÄT INFORMATIK UND ELEKTROTECHNIK H.-W. Glock - Thomas Flisgen 19 19

following Nov'09 SPL Meeting proposal: 30 mm diameter coaxial couplers SPL-β=1-cavity: HOM-Qload from full setup computation of coax-coax-transmission 80 mm diameter shortened beam pipes following Nov'09 SPL Meeting proposal: 30 mm diameter coaxial couplers Do they provide sufficient HOM damping without fundamental mode filter? 04/08/2010 © 2010 UNIVERSITÄT ROSTOCK | FAKULTÄT INFORMATIK UND ELEKTROTECHNIK H.-W. Glock - Thomas Flisgen 20

Coax with antenna tip depth = 0: to avoid extreme Q-values scaling in a second step using coupler section's S-parameters in order to reach design fundamental mode Q 04/08/2010 © 2010 UNIVERSITÄT ROSTOCK | FAKULTÄT INFORMATIK UND ELEKTROTECHNIK H.-W. Glock - Thomas Flisgen 21

Entire transmission spectrum 0. 65 – 2 Entire transmission spectrum 0.65 – 2.80 GHz: - more than 400 resonances with wide Q-range 04/08/2010 © 2010 UNIVERSITÄT ROSTOCK | FAKULTÄT INFORMATIK UND ELEKTROTECHNIK H.-W. Glock - Thomas Flisgen 22

Using Pole-fitting algorithm* to determine loaded Q's f/GHz S21/dB fundamental mode passband - dots: cstStudio© computation - line: fit result *: Hecht, Rothemund, Glock, van Rienen: "Computation of RF properties of long and complex structures", Proc. EPAC 2002 04/08/2010 © 2010 UNIVERSITÄT ROSTOCK | FAKULTÄT INFORMATIK UND ELEKTROTECHNIK H.-W. Glock - Thomas Flisgen 23

Pole-fitting algorithm: "Old" version S21/dB "Old" algorithm (see reference) 04/08/2010 © 2010 UNIVERSITÄT ROSTOCK | FAKULTÄT INFORMATIK UND ELEKTROTECHNIK H.-W. Glock - Thomas Flisgen 24

Improved pole-fitting algorithm S21/dB Improved algorithm - corrects for higher order contributions, but still not working in any case see: IPAC10, WEPEC008: Glock, Galek, Pöplau, van Rienen: HOM Spectrum and Q-factor Estimations of the High-beta CERN-SPL-cavities 04/08/2010 © 2010 UNIVERSITÄT ROSTOCK | FAKULTÄT INFORMATIK UND ELEKTROTECHNIK H.-W. Glock - Thomas Flisgen 25

Q-value of lowest modes for 0 mm antenna depth: fundamental mode: Q = 1.04 108 fits well to field matching based estimation (4.3 108 for single coupler, slightly different geometry) f/Hz 04/08/2010 © 2010 UNIVERSITÄT ROSTOCK | FAKULTÄT INFORMATIK UND ELEKTROTECHNIK H.-W. Glock - Thomas Flisgen 26

Q-value spectrum for 0 mm antenna depth: f/Hz Several HOM modes with Q values as high or above fundamental mode (holds also for reduced coupling) – Couplers without filters are not an acceptable solution! 04/08/2010 © 2010 UNIVERSITÄT ROSTOCK | FAKULTÄT INFORMATIK UND ELEKTROTECHNIK H.-W. Glock - Thomas Flisgen 27