G. Sirri – INFN BO 1

Test of Lamp with centering filament and mirror

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:1. the filament image is pre-centered and can be neither fine centered nor

focused;2. the filament image doesn’t cover completely the aperture diaphragm.3. 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 for the Bologna group

Neuchatel - 27 Sep 2006

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)

with frosted glassand green filter

CURRENT:pre-centered*

UPGRADE: Centering filament and back mirror

Objective exit pupil. NA=0.9

Apert. DiaphragmNA=0.8

*Filament plugs forced in the center position but not focused

Filament focused(magnified) image

Mirrored image

Neuchatel - 27 Sep 2006

G. Sirri – INFN BO 3

Light distributions in the aperture diaphragms plane

Light

inte

nsi

ty (

gre

y level)

position-0.9 0.90

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 lightFlatter light gathered at high angles (better optical resolution) isotropic flux in the field of view

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

* Filament manually centered and focused by forcing the filament plugs…

CURRENT

CURRENT*

UPGRADE

Neuchatel - 27 Sep 2006

G. Sirri – INFN BO 4

Grains Analysis with the UPGRADED Lamp

Level-to-level distance ~ 0.5 µm

Vertical clusters chains obtained using the libEGA of FEDRA

UPGRADE

Clu

ster

are

a (

pix

els

)

cluster-to-grain_center vertical distance (µm)

CURRENT*

Clu

ster

are

a (

pix

els

)

cluster-to-grain_center vertical distance (µm)

z0

eZz

ggrains

cluster

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…

50X oil objective in the altered conjugates set-upgreen filter

* Filament manually centered and focused by forcing the plugs

Neuchatel - 27 Sep 2006

G. Sirri – INFN BO 5

Check of the repeatability, efficiencies, …

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%

UPGRADE CURRENT*

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%

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

… therefore not much changes are obtained in the base-track measurements for what concerns repeatability, efficiency, purity, resolutions…

* Filament manually centered and focused by forcing the plugs

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

Efficiencies, Purity, Resolutions are the same obtained in Bologna and already presented in the past meetings

Neuchatel - 27 Sep 2006

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).

Neuchatel - 27 Sep 2006