1 / 11

R. Bonomi A. Degiovanni M. Garlaschè Image studies for RF breakdowns

R. Bonomi A. Degiovanni M. Garlaschè Image studies for RF breakdowns. CLIC meeting TERA Foundation 16th June 2010. Background. A future test is foreseen for the S-band one-cell-test cavity  n o cut of the cavity!

shana
Download Presentation

R. Bonomi A. Degiovanni M. Garlaschè Image studies for RF breakdowns

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. R. Bonomi A. Degiovanni M. GarlaschèImage studies for RF breakdowns CLIC meeting TERA Foundation 16th June 2010

  2. Background • A future test is foreseen for the S-band one-cell-test cavity  no cut of the cavity! • Need to have spatial references on the inner surface for determining the area where breakdowns mainly occurred: area close to • max E field • max B field • max Poynting Vector ?? • Aim: drawing nose region line and max fields lines on the pics taken (with MatLab programs) ONR INR Image study for RF breakdowns

  3. Surface inspection set-up* *Thanks to J. Kovermann, A. Olyunin Digital camera Optical stereo microscope Software for image acquisition S-band cavity Tilt plane: every pic is taken with the same angle! Image study for breakdowns

  4. Some pics.. A-side 90x 32x B-side Example of 2 very big craters! (Distance btw machining lines ~20 µm) 32x Image study for RF breakdowns

  5. Theory behind - 1 • Bore hole circumference  ellipse if the plane where it lives is tilted • Angles α and β: indication of the tilt plane in the 3D space α β Image study for RF breakdowns

  6. Theory behind - 2 7x • Image centre is taken as a reference to “move” from one pic to the other one • Within the same pic, ellipse centre is always “corrected” to when referred to another plane by means of α and β TIP ONR INR C F 63x Image study for RF breakdowns

  7. 1) Ellipse “enclosed” in a rectangle 7x • Image modification (grayscale, bw, ...) • Find Top, Bottom, Right and Left points of enclosing rectangle • Find Centre of ellipse (with Top and Bottom) • Find N, S, E and W points (with Centre) • Calculation of α, β (comparison of semi axes* with bore radius) BW limit N T W R C L B • * We used segments CW and CN, since these segments differ from the semi axes just for an angle of 0.1 degrees. Image study for RF breakdowns

  8. 1) Ellipse “enclosed”: Results • Too blurry ellipse profile: not enough precision in the research of points • High sensitivity to BW limit: too much variation in α,β!! • NO reliable results Nose tip 7x INR 63x “LIMIT” = 0.36 Image study for RF breakdowns

  9. 2) Ellipse from 5 points 7x • Image modification (grayscale, bw, ...) • Error minimization: 5 points • Implicit eq. • Canonic eq. Ax2 + Bxy + Cy2 + Dx + Ey + F = 0 [x y 1] [mat3] [x;y;1] = 0 λ1x2 + λ2y2 + λ3 = 0 Ellipse center, semi axes, rotation λ1, λ2 = eig(mat2) λ3 = det(mat3) / det(mat2) Image study for RF breakdowns

  10. 2) Ellipse from 5 points: Results α = 10º β = 0º • NO reliable results α = 21º β = 6º α = 21º β = 6º Outer nose radius α = 30º β = 0º α = 20º β = 0º Nose tip Inner nose radius Image study for RF breakdowns

  11. Problems.. • Profile of the bore hole too blurry  low precision for the ellipse • No pics of the inner nose radius (too dark)  no hints on BD presence there • We would have needed: • Precise instrumentation to tilt the cavity • Microscope characterization for visualization angle • ..only solution: cut the cavity (BUT after the next test!!) Thank you very much for your attention! Image study for RF breakdowns

More Related