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Quality control facilities for large optical reflectors at ENEA-Casaccia for physics application

Quality control facilities for large optical reflectors at ENEA-Casaccia for physics application. Stefania Baccaro a,d , Carlo Bosio b,d , Augusto Maccari c , Marco Montecchi a,d a) ENEA FIS-ION, Casaccia, Roma, Italy b) Dipartimento di Fisica Università La Sapienza , Roma, Italy

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Quality control facilities for large optical reflectors at ENEA-Casaccia for physics application

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  1. Quality control facilities for large optical reflectors at ENEA-Casaccia for physics application Stefania Baccaro a,d, Carlo Bosio b,d, Augusto Maccari c, Marco Montecchia,d a) ENEA FIS-ION, Casaccia, Roma, Italy b) Dipartimento di Fisica Università La Sapienza, Roma, Italy c) ENEA SOLTERM, Casaccia, Roma, Italy d ) INFN – Sezione di Roma1, Roma, Italy

  2. Large optical reflectors are used in… • Astronomy: in telescope (imaging) • High Energy Physics: in RICH, to focus Cherenkov radiations on optical sensor (quasi-imaging) • …… • Solar Energy: as sun-power collectors (collecting)

  3. … for information completeness • How large? Single panel, up to some meters • Imaging use is much more demanding than collecting one • Composition and shape are designed for the specific application and ..... ... HAVE TO BE TESTED !!!

  4. Irradiation plants at ENEA – Casaccia • TAPIRO: fast neutrons • TRIGA: thermal neutrons • CALLIOPE: 1.17 and 1.33 MeV  Optical laboratory tender to Calliope: • spectrophotometers and spectrometer • Light-Yield • damped optical top with light sources, lenses, mirrors, detectors, etc..  custom set-up

  5. Optical tests at ENEA-Casaccia • spectrophotometer – specular and diffused (small flat sample) • spectrometer – specular (full scale reflector) Reflectance: Shape performances: • 2f optical testfocal length and image spot dimension • pin-hole optical testvisual inspection of the curvature • profilometer accurate measurement of the curvature

  6. LED ( = 5 mm) image screen 2 f 2f optical test:focal length and image-spot dimension in the ideal case, image and source have the same dimension

  7. surface image LED pin-hole f1 2 f p q Pin-hole optical test:a visual inspection of the curvature where the surface image is dark, the curvature is wrong

  8. LHCb RICH mock-up: carbon fiber + honeycomb  ~ 600 mm 2f = 1700  20 mm  image spot ~ 15 mm

  9. LHCb mock-up : polymethylmethacrylate (PMMA) hot bended and honeycomb  ~ 400 mm 2f = 2370  20 mm image spot ~ 25 mm

  10. LHCb RICH mock-up:PMMA poured liquid on master  ~ 350 mm 2f = 2330  20 mm

  11. LHCb mock-up: electrodeposited Ni  = 200 mm 2f = 315 5 mm

  12. Accurate test of the reflector curvature: profilometer • In the framework of the Concentrating Solar Power Project, ENEA is providing with an optical profilometer to test large linear parabolic reflectors • the measurement is automatic - PC controlled • the profilometer can be used also for reflectors differently shaped (e.g. spherical reflector) • actually the instrument performs 1D scanning • 2D upgrade is imminent

  13. rotation axis x screen  x0 xS (xC,yC) HeNe Nikon D1X, 4.024 x 1.324 px yS y ENEA optical profilometer (1D) • the surface is scanned by tilting the incident beam () with a high precision rotation stage (20 rad repeatability) • the intersection of the reflected beam with the screen (XS) is deduced by processing the digital image

  14. y = f (x,p1,..,pM) x y = tg() (x - x0)  x0 xS simulated xSexperimental yS y Data processing – 1th method: fit best fit by minimising

  15. A P2 x B central point ( = 90°): (xc,yc) directly measured set dy/dx = 0 by tilting C   x0 P1 y yS parabolic: xC = (x1+x2)/2 P2 y = x2 P2 circular: P1C =CP2 P1 C P1 xC x2 x1 Data processing - 2nd method:iterative extrapolation (I.E.) the next point P2 is: • along the incident beam, by definition • in AB, if 1;  P1C, P2C  P1P2 • univocally determined by assuming:

  16. Example: reduced scale linear parabolic reflector (aperture 0.6 m) best fit parameters: 2 = 1.23 (32/49 data) P4 = 0.32  0.04 • = 11.3  0.8 deg f = 185.5  0.5 mm high precision

  17. comparison of the two methods • I.E. method gives a realistic profile of the reflector • I.E. method allows to evaluate the locale deviations from the project specifications of both profile and slope

  18. comparator harm rotation stage reflector validation of the iterative extrapolation method direct measurement

  19. Conclusions The ENEA-Casaccia facilities allow to measure the most important features of large optical reflectors: • specular and hemispherical reflectance • focal length • surface profile 2D upgrade of the profilometer is imminent

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