Risto Montonen Ivan Kassamakov Edward H ӕ ggström and Kenneth Österberg This document describes an optics based technique to measure the internal shape of CLIC AS and to align the disk stack ID: 806765
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Slide1
CLIC AS internal metrology
Risto Montonen, Ivan Kassamakov, Edward Hӕggström, and Kenneth ÖsterbergThis document describes an optics based technique to measure the internal shape of CLIC AS and to align the disk stack.
20.6.2013
1
Slide2Introduction
Accelerating Structures (AS) comprising OFE Cu disks undergo permanent thermo-mechanical deformations during assembly and operation:assembly: AS disks suffer creep deformations [1] due to diffusion bonding [2],operation: pulsed RF waves [3] induce intense local pulsed thermal stresses into the RF cavity walls [4].These deformations result in micron-level misalignments in AS reducing CLIC luminosity.
Sub-micron accuracy topographic contact-scanners to measure shape of single disks exist [6]. However, these techniques are unfeasible for disk stack internal shape quantifying purposes.
Alignment method based on
intracavitary
technique has to be developed.
Shape error
Tolerance
1
µm [2,5]
5
µm [3]
140 µrad [2,5]
Slide3Aim of the study
The presentation focuses on the design of:Sub-micron accuracy and non-destructive optical device to measure the internal shape of CLIC AS disk stacks.Scanning system for “internal” measurements with on-line correlation to “external”
measurements.
Slide4General view of the device
1. Interferometer 2. Optical probe
3. Scanning system
Slide5Optical device. Interferometer
F
-1
Frequency-domain short-coherence interferometry
Broadband light:
= 2.0 µm, -3 dB system bandwidth =
= 0.1 µm
Spectral
interferogram
constructed from reference and sample
reflection
Axial pixel size
= point-to-point separation in A-scan < 1 µm
Axial resolution
20 µm [7]
10 mm
axial depth range
requires 0.1 nm spectral resolution
[7]
Slide6Optical device. Optical probe
Tungsten carbide housing
IR single mode optical fiber: NA = 0.11
GRIN collimation: pitch = 0.25, f = 0.45 mm
,
lateral
resolution = spot size < 100 µmIR mirror provides 90° side
view
Slide7Scanning system
AS disk stack rotated and optical probe
pulled out
Cylindrical coordinate system
Reference configuration defined by the first
disk
Slide8Scanning system
Internal and external measurements should be comparable.Internal and external measurements introduce their own metrological reference configurations.To obtain comparable data we should:fix the internal and external measurement devices on each other,m
easure the internal and external shape in parallel.
Internal and external measurement data in the same
global metrological reference configuration
[8]
Slide9Conclusion
Sub-micron accuracy and non-destructive AS internal shape measuring technique is needed.Frequency-domain short-coherence interferometry with fiber coupled optical probe provides AS internal topographic scanning with 20 µm axial resolution, < 100 µm lateral resolution, and 10 mm depth
range.To obtain comparable
data the internal
and
external measurements should be done in parallel (devices fixed to each other).Work for the first practical setup is currently ongoing
Slide10References
[1]
D.M. Owen, T.G. Langdon, Materials Science and Engineering A
216
(1996) 20-29
.
[2] A Multi-
TeV
linear collider based on CLIC technology: CLIC Conceptual Design Report, edited by M. Aicheler, P. Burrows, M. Draper, T. Garvey, P. Lebrun, K. Peach, N.
Phinney, H. Schmickler
, D. Schulte, and N. Toge.[3] H. Braun et al.,
CERN-OPEN-2008-021; CLIC-Note-764.[4] M. Aicheler, S. Sgobba, G.
Arnau-Izquierdo, M. Taborelli, S. Calatroni, H.
Neupert, W. Wuensch, International Journal of Fatigue 33 (2011) 396-402.
[5] R. Zennaro, EUROTeV-Report-2008-081.[6]
S. Atieh, M. Aicheler, G. Arnau-Izquierdo, A. Cherif, L. Deparis
, D. Glaude, L. Remandet, G. Riddone
, M. Scheubel, D. Gudkov, A.
Samoshkin
, A.
Solodko, IPAC’11
, San
Sebastián
,
Spain.
[7] R.A.
Leitgeb
, W. Drexler, A.
Unterhuber
, B. Hermann, T.
Bajraszewski
, T. Le, A. Stingl, and A.F. Fercher, Optics Express 12 (2004) 2156-2165.[8] http://www.solveit.hu/termekek/mycrona/Mycrona%20Altera%20Nano.pdf
Slide11Thank you for your interest