Mathias Gerbaux CTF3 Collaboration Technical meeting 27/01/2009

1. 30 GHz results from 2008 Mathias Gerbaux CTF3 Collaboration Technical meeting 27/01/2009

2. F D F F D D F F D D F F F F D D F F F F F F D D F D D D D D F F D D D D F F D D F F D D F F D D D F F D D D D F D D F D F To set the stage… Thermionic gun Linac DL CR 2006/7 F F D D D D F F F F D D F F D D F F F F D D F F F F F F D D F F D D D D D D F F D D D D F F D D F F D D D D F F F F D D D D D D F F F F D D D D D D D D F F D D D D F F D D F F CLEX CTF2 30 GHz production (PETS line) and test stand CTF3 Collaboration meeting Jan 2009 G.Geschonke

3. Structures tested in 2008 Onlytwo… • HDS4_thick : re-test, badresults. Didn’t reach an accelerating gradient much higher than 60 MV.m-1. • C30 speed bump: samegeometry as the older 3.5 mm structure except for a « speed bump » lowering the group velocityat the input. Twomeasurements : fed by the input and by output. Mathias Gerbaux - CTF3 Collaboration Technical meeting - 27/01/2009

4. R=14.398 mm R_iris= 2.428 mm Iris_thickness= 1mm Speed bump (TM03) Courtesy of Riccardo Zennaro Test structure in disks: 30 cell and identical mode launcher of the “conventional” 2π/3 Ø 3.5 mm

5. HDS4_thick re-test: wholehistory In total : 1,244,800 pulses, mainlyat 1 Hz corresponding to 5.76 SLAC hoursat 60 Hz but crappy data Mathias Gerbaux - CTF3 Collaboration Technical meeting - 27/01/2009

6. HDS4_thick re-test : typical running Mathias Gerbaux - CTF3 Collaboration Technical meeting - 27/01/2009

7. C30-sb • In total : • 4,101,250 pulses, mainlyat 1 Hz corresponding to 18.99 SLAC hoursat 60 Hz • 2186 breakdowns Weirdthings due to calibration problems (nowsolved) Mathias Gerbaux - CTF3 Collaboration Technical meeting - 27/01/2009

8. C30-sb-reversed • In total : • 1,704,650 pulses, mainlyat 1 Hz corresponding to 7.89 SLAC hoursat 60 Hz • 501 breakdowns Weirdthings due to calibration problems (nowsolved) Mathias Gerbaux - CTF3 Collaboration Technical meeting - 27/01/2009

9. Wefigured out at the end of Fall 2008 that calibration wasaffected by variousfactors(driftingbaselines, temperature…). If we assume the measurement of the incident power is not toowrong… Or at least itisonly the absolute calibration thatiswrong and itdon’t change tooquickly. Then, wecancalculate the breakdown rate as a function of the accelerating gradient . Mathias Gerbaux - CTF3 Collaboration Technical meeting - 27/01/2009

10. Breakdown rate calculation OK Mathias Gerbaux - CTF3 Collaboration Technical meeting - 27/01/2009

11. Breakdown rate vs gradient – speed bump structure 3.5 mm structures comparison • Vertical error bars calculatedassuming an error of 1 on the breakdown number and 500 on the number of pulses. • Horizontal error bars : standard deviation of the measured gradient. • Redcircles are upperlimits (no breakdown recorded). • Fit doesn’ttakeintoaccountthese points. --Old 3.5mm structure • No effect of the speed bump on the breakdown rate • Need post-mortem examination to see if it has one on the surface damage Mathias Gerbaux - CTF3 Collaboration Technical meeting - 27/01/2009

12. DIY electronspectrometer CCD filter L magnet B Speed bump structure • Rough calculations : • with B=0.15 mT (0.1 A), E(e-) > 200 eV • with B=0.75 mT (0.5 A), E(e-) > 10 keV • with B=3.0 mT (2.0 A), E(e-) > 200 keV • with B=7.5 mT (5.0 A), E(e-) > 500 keV d l X 45° α Alumina screen R α Some spots… Most of the time : 0 A 0 A 1 A 3 A Mathias Gerbaux - CTF3 Collaboration Technical meeting - 27/01/2009

13. DIY electronspectrometer – just a fewpictures Positive magneticfield Negativemagneticfield increasing • There is an effect compatible with an electron signal (up to 500 keV) • Wehaven’t a real « zero » position • Hugespread of the spot, non-reproducibility • No calibration number of electrons – light intensity Needs a collimator ! Mathias Gerbaux - CTF3 Collaboration Technical meeting - 27/01/2009

14. Conclusion and future plans • 2 structures tested last year : • HDS4_thick showedpoor performances • C30-speed bump gave betterresults • But remember the cumulative duration of the tests isstill short compared to SLAC tests (lessthan 33 h in total for 2008). • C30-sbmanufacturedfollowing the sameprocedure as the T18 X-band structure currentlytestedat SLAC withbadresults. • Spectrometermeasurementperformedwith what was at hand, definitely lacks a collimator ! • Poorreproducibility, we are working to see if itcanberelated to the position of the breakdown (structure acting as a collimator). • Nevertheless gave indications of an e-“beam” emmittedduring the breakdown with an energy up to at least 500 keV. • ONE last 30 GHz structure to betested in 2009 (TM02), opticalspectrometrymeasurementwillbedone (J. Kovermann). Mathias Gerbaux - CTF3 Collaboration Technical meeting - 27/01/2009

15. Manythanks : Alexandra Andersson Jan Kovermann Steffen Döbert Riccardo Zennaro and for your attention ! to Mathias Gerbaux - CTF3 Collaboration Technical meeting - 27/01/2009

16. C30-sb In blue : myanalysis In green : Steffen’s one Mathias Gerbaux - CTF3 Collaboration Technical meeting - 27/01/2009

17. C30-sb-reversed 7 6 Slightimprovementwith time 2 1 4 3 5 Mathias Gerbaux - CTF3 Collaboration Technical meeting - 27/01/2009

18. C30-sb-reversed Different points ↔differentanalysis (file by file for Steffen’sanalysis, single file combining the wholehistory for mine). Slopedifference : 0.2 % Mathias Gerbaux - CTF3 Collaboration Technical meeting - 27/01/2009

19. HDS4_thick re-test : ``results´´ Upperlimit Mathias Gerbaux - CTF3 Collaboration Technical meeting - 27/01/2009

20. HDS4_thick beginning of the test Mathias Gerbaux - CTF3 Collaboration Technical meeting - 27/01/2009

21. Spectrometercalculations L magnet B Speed bump structure d l X 45° α Alumina screen R α

22. DIY electronspectrometer – ``statistical´´analysis Increasing B field SeeJan’spresentation on February, 18th Mathias Gerbaux - CTF3 Collaboration Technical meeting - 27/01/2009

23. TM02 structure Courtesy of Riccardo Is it possible to change some global parameter without changing local field distribution? Only by changing the propagating mode TM01 regular cell “reference” Same phase advance Same P/c Same aperture and iris shape Same field configuration in the iris region but Different group velocity: 4.7% & 2% Different R/Q: 29 kΩ/m & 12 kΩ/m TM02 regular cell Test structure in disks: 30 cell and identical mode launcher of the “conventional” 2π/3 Ø 3.5 mm

24. Vg TM01: 2π/3 Vg=4.7% d a TM02: 2π/3 Vg=2.0% Direct comparison of Vg Courtesy of Riccardo

25. Je ne sais pas si la vidéo restera longtemps à cette adresse mais pour le moment, vous pouvez écouter l’intégralité du « discours à l’occasion du lancement de la réflexion pour une Stratégie Nationale de Recherche et d’Innovation » de Sarkozy. Attention cependant, ses putains d’accents poujadistes et sa façon de nous prendre pour des cons sont susceptibles de vous mettre de très très mauvaise humeur ! http://www.elysee.fr/accueil/ Bonne journée quand même… Why speed bump? Courtesy of Riccardo From Igor’s presentation at the X band workshop: Very often we do observe, that after accelerating structure processing the most of the surface modifications take place in a few first cells. Also the number of cells involved is correlated with the group velocity, the less the Vg the fewer cells modified. What do we certainly know, the breakdown ignition is a very fast process: 0.1 -10 ns. If so, one can propose the main difference between the “first” and “second” cell is accessible bandwidth. And the lower group velocity the more the difference. The first cell, if breakdown occurs is loaded by the input coupler/waveguide and is very specific in terms of bandwidth. Other words, the first cell can accept “more” energy during breakdown initiation then consequent ones. Worse to mention that we do not know the exact transient behavior of the breakdown and the structure bandwidth could play important role. We can tray by reducing vg in the matching cell PINC PINC HDS 60 L HDS 60 S