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Test of Lamp with centering filament and mirror

Test of Lamp with centering filament and mirror. G. Sirri for the Bologna group. An UPGRADE for the illumination with back mirror-lens and fine centering and focusing filament knobs has been realized by Nikon Italia and tested in Bologna

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Test of Lamp with centering filament and mirror

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  1. Test of Lamp with centering filament and mirror G. Sirri for the Bologna group • An UPGRADE for the illumination with back mirror-lens and fine centering and focusing filament knobs has been realized by Nikon Italia and tested in Bologna • The CURRENT illumination by Nikon Italia is not a perfect Koehler system: • the filament image is pre-centered and can be neither fine centered nor focused; • the filament image doesn’t cover completely the aperture diaphragm. • a back mirror-lens is not present Consequences:  possible horizontal motion of grains images (shadows) during vertical displacement  possible limitation in the optical axial and lateral resolutions  loss of the light emitted by the filament G. Sirri – INFN BO

  2. Looking the exit pupil of the objective Remove an eyepiece and look at the exit pupil of the objective where is the image of the aperture diaphragm and of the filament (better with an auxiliary telescope) CURRENT:pre-centered* UPGRADE: Centering filament and back mirror Filament focused(magnified) image Mirrored image Objective exit pupil. NA=0.9 with frosted glass and green filter Apert. DiaphragmNA=0.8 *Filament plugs forced in the center position but not focused G. Sirri – INFN BO

  3. Light distributions in the aperture diaphragms plane CURRENT: The aperture diaphragm is not homogeneously illuminated. The borders are quite dark and eccentric lighter zones can behave as intense out-of-axis sources (and contribute to the “shadow”). UPGRADE The light distribution in the aperture plane is: Higher  more light Flatter  light gathered at high angles (better optical resolution)  isotropic flux in the field of view CURRENT Light intensity (grey level) CURRENT* Light Intensity in the field of view: Voltage (a.u.) mean intensity (g.l.) CURRENT : 32767(max) 150 +/-10 CURRENT* : 32000 208 +/-12 UPGRADE : 29000 210 +/-10 Note: 0.5 ms exposure, green filter, frosted glass UPGRADE * Filament manually centered and focused by forcing the filament plugs… -0.9 0 0.9 position G. Sirri – INFN BO

  4. Grains Analysis with the UPGRADED Lamp z cluster eZ z0 grains g CURRENT* UPGRADE Cluster area (pixels) Cluster area (pixels) cluster-to-grain_center vertical distance (µm) cluster-to-grain_center vertical distance (µm) 50X oil objective in the altered conjugates set-up green filter Level-to-level distance ~ 0.5 µm Vertical clusters chains obtained using the libEGA of FEDRA * Filament manually centered and focused by forcing the plugs We have little changes in the grains shape: even if better illuminated the length of the grain image (the vertical resolution of the system) is strongly affected by the spherical aberration… G. Sirri – INFN BO

  5. Check of the repeatability, efficiencies, … … therefore not much changes are obtained in the base-track measurements for what concerns repeatability, efficiency, purity, resolutions… One example: 2x2 cm² on the pl36 of the reference brick 5 (TB June 2004) Selected 8 peaks, 3-times measured, repeatability 3 over 2 (+/- 2%)eChi2P<2.5 * Filament manually centered and focused by forcing the plugs UPGRADE CURRENT* N2 N3 mean sigma repr. 1: (e)375 (e)345 (m)0.2771 (s)0.0039 92% 2: (e)433 (e)389 (m)0.1869 (s)0.0032 90% 3: (e)405 (e)380 (m)0.2067 (s)0.0032 94% 4: (e)433 (e)396 (m)0.3347 (s)0.0042 91% 5: (e)384 (e)344 (m)0.2016 (s)0.0024 90% 6: (e)509 (e)460 (m)0.0086 (s)0.0024 90% 7: (e)443 (e)412 (m)0.0938 (s)0.0018 93% 8: (e)457 (e)400 (m)0.2850 (s)0.0040 88% N2 N3 mean sigma repr. 1: (e)347 (e)321 (m)0.2779 (s)0.0040 93% 2: (e)409 (e)379 (m)0.1875 (s)0.0034 93% 3: (e)394 (e)356 (m)0.2066 (s)0.0033 90% 4: (e)439 (e)389 (m)0.3345 (s)0.0044 89% 5: (e)373 (e)334 (m)0.2018 (s)0.0025 90% 6: (e)505 (e)463 (m)0.0087 (s)0.0023 92% 7: (e)439 (e)413 (m)0.0936 (s)0.0019 94% 8: (e)436 (e)390 (m)0.2844 (s)0.0040 89% Efficiencies, Purity, Resolutions are the same obtained in Bologna and already presented in the past meetings OVERALL ALIGNMENTS obtained with the UPGRADED illuminatorsome tracks have been measured and compared with the same tracks after a 180 degree rotation. The half mean value of the distribution of the tracks slopes differences before and after the rotation is (0.3 +/- 0.1) mrad G. Sirri – INFN BO

  6. Conclusions • The upgraded version of the lamp has been tested • it is possible to align the filament without roughly forcing the filament plugs and fix the problem of the horizontal motion of the grains images during the vertical displacement (moving “shadows” effect). [Note that a similar effect is also due to the misalignments of the motorized axis] • the light intensity is higher so that the green filter and the frosted glass can be used. • the distribution of light rays gathered by the objective is more isotropic and the final numerical aperture of the system increases (however these improvements are limited by the spherical aberration in the current set-up). G. Sirri – INFN BO

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