LNGS 4 Jul 2006 INFN BO1 Grain analysis with High-Resolution microscope  An High Resolution microscope was developed in parallel with the ESS and is working in BOLOGNA (MIC1 – PROTO).  The microscope is used for manual checks, fog measurements and (recently) scanning with sysal. Bologna group (G.Sirri)  The microscope is equipped with : ZEISS 100x objective | n.a. 1.3 ZEISS tube lens hosted in a custom tube Stage with higher load capacity [MICOS HPS-170] Legs with air suspension mechanisms to reduce vibrations. Custom CMOS camera (same sensor as mikrotron mc1310)  Illumination, horizontal stage, motor controller, frame grabber, workstation are the same as ESS

LNGS 4 Jul 2006 INFN BO2 Measurements of the optical resolution: star test Star test: diagnostic tool which consists in the observation of the image of a point source of light (also known as Point Spread Function (PSF) of the objective) from the specimen projected by the microscope objective onto the camera sensor plane. In a perfect aberration-free optical system the image will be a very close approximation to the diffraction pattern rings Aberrations enlarge the Airy disk and produce a spot with variable form and photometric profile (circle of least confusion). This enlargement reduces the resolving power both in the lateral and in the axial directions.

LNGS 25 May 2005 G. Sirri – INFN BO ZEISS 100x Z (micron) Nikon 50x [custom setup: camera 50 mm below the specific coniugate] Circle of least confusion Z ≈ 1 micron Circle of least confusion Z ≈ 5 micron X, Y ≈ 0.2 micron X, Y ≈ 1 micron NEGATIVE IMAGES

LNGS 4 Jul 2006 INFN BO4 Image formation If our “object” size (grain Ø ≈ micron) is smaller than the “circle of least confusion” :  the geometrical image of the grain is smaller than the “circle of least confusion” and consequeltely its size is not proportional to the object (impossible to observe little differences in size)  as smaller the object, as brighter the image Since the horizontal dimension of the circle of least confusion is 0.2 microns, this microscope is able to measure the grain size. The grain image is the space convolution between the grain surface and the P.S.F..

LNGS 4 Jul 2006 INFN BO5 Acquisition, analysis … and credits  We used libACQ, a test library developed by I. Kreslo (Bern) and installed with the help of V. Tioukov (Naples). Each image grabbing is triggered by stage controller Output in libEdb format (FEDRA) Mean grey level of the clusters is also stored 100 levels per emulsion layer Image size: 0.5 Megapixel Magnification: micron/pixel Several views in the whole emulsion sheet  Analysis with an improved version of the Fedra Grain Analysis library (by V. Tioukov). limit for the clusters area >= 5 Vertical length of a grain >= 3 layers  Two samples: Nov (vertex location CERN test beam) June 2006 (cosmic rays exposure at LNGS) Grain Size = cluster area at center grain eZ0 eZ z g grains cluster

LNGS 4 Jul 2006 INFN BO6 Stability of the algorythm (Vertex Loc. nov04,br7,pl8) Red = top Blue = bottom sublayer near the surface sublayer near the base

LNGS 4 Jul 2006 INFN BO7 Mean grain area profile 100X ESS (expansion filter) ESS  Nov 2004  June 2006

LNGS 4 Jul 2006 INFN BO8 Cluster area profile (cut: area>2) (Vertex Loc. nov04, br7, pl8) (cosmic rays, jun06, pl33) Red = top Blue = bottom

LNGS 4 Jul 2006 INFN BO9 Grey level horizontal profile (cosmic rays, jun06, pl33) X (1 pixel = micron) Grey level FWHM ≈ 5 pixel ≈ 0.6 micron

LNGS 4 Jul 2006 INFN BO10 (Vertex Loc. nov04, br7, pl8) Grey level vertical profile (negative image) (cosmic rays, jun06, pl33) Red = top sublayer near the surface Blue = bottom  sublayer near the base

LNGS 4 Jul 2006 INFN BO11 Grain Size vertical profile (Vertex Loc. nov04, br7, pl8) (cosmic rays, jun06, pl33) Red = top Blue = bottom Ø 0.72 micron Ø 0.62 micron Ø 0.59micron Ø 0.69 micron

LNGS 4 Jul 2006 INFN BO12 Conclusions  The grains of two sample were measured with a high resolution microscope equipped with 100x Zeiss objective. Nov (vertex location test beam exposure at CERN) June 2006 (cosmic rays exposure at LNGS)  Grain size: maybe -5% smaller, but we shuold better estimate the uncertainty related to threshold set-up and illumination uniformity )  At present the only evidence is for different thickness of the emulsion layers (35-40 micron for nov and for june 2006). Further investigation are needed.

LNGS 4 Jul 2006 INFN BO13 Further test with sysal MIC3 (sysal): Thr GS (2004) GS (2006) GS (2004) (expansion filter) GS (2006) 4.9 (27’ development)