1 / 23

30 GHz test results from 2008

30 GHz test results from 2008. Mathias Gerbaux RF structure development meeting 21/01/2009. Structures tested in 2008. Only two … HDS4_thick : re-test , bad results ( see Steffen’s talk 28/05/2008). Didn’t reach much higher than 60 MV.m -1 .

sawyer
Download Presentation

30 GHz test results from 2008

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. 30 GHz test results from 2008 Mathias Gerbaux RF structure developmentmeeting 21/01/2009

  2. Structures tested in 2008 Onlytwo… • HDS4_thick: re-test, badresults (seeSteffen’s talk 28/05/2008). Didn’t reach 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 (seeSteffen’s talk 20/08/2008) and by output.

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

  4. 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

  5. HDS4_thick re-test : typical running

  6. 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 (seeJan’s talk)

  7. 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 (seeJan’s talk)

  8. 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.

  9. Breakdown rate calculation OK

  10. C30-sb-reversed • 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. 7 6 • Redcircles are upperlimits (no breakdown recorded). • Fit doesn’ttakeintoaccountthese 2 points. 2 1 4 3 5 • Slightimprovementwith time

  11. C30-sb-reversed Different points ↔differentanalysis (file by file for Steffen’sanalysis, single file combining the wholehistory for mine). Slopedifference : 0.2 %

  12. 3.5 mm structures comparison • No effect of the speed bump on the breakdown rate • Need post-mortem examination to see if it has one on the surface damage

  13. DIY electronspectrometer CCD L magnet B Speed bump structure • Very 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

  14. DIY electronspectrometer – ``statistical´´analysis Increasing B field SeeJan’spresentation on February, 18th

  15. DIY electronspectrometer – Field inversion Positive magneticfield Negativemagneticfield • There is an effect compatible with an electronsignal (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 !

  16. Manythanks to Jan, Alexandra, Riccardo and Steffen

  17. C30-sb In blue : myanalysis In green : Steffen’s one

  18. HDS4_thick re-test : ``results´´ Upperlimit

  19. HDS4_thick beginning of the test

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

  21. 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

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

  23. 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

More Related