Giovanni De Lellis University of Naples (Italy) An overview of the European Scanning System (ESS) Nucl.Instrum.Meth. A568 (2006) Nucl.Instrum.Meth. A554 (2005) Nucl.Instrum.Meth. A551 (2005)

Working principles High speed computer-controlled precision mechanics for both horizontal and vertical stages, able to move from one field of view to the next in less than 0.1 s Standard optical system customized to analyze 300 µm thick emulsion films Mega pixel camera interfaced with a high speed frame grabber and a vision processor grabbing and analyzing images at 350 fps An European R&D project started in 2000 ended with the first prototype in Summer 2004, achieving 20cm2/hour Bari, Bern, Bologna, Lyon, Naples, Neuchatel, Rome, Salerno

Mechanical movements Field of view Time evolution of the stage position during the field of view change Measurement of the time needed for the field of view change dumping the vibration within 0.2µm

Movement cycle Goal of 20 cm2/hour One field of view of 390 x 310 µm 2  1cm 2 ~ 827 views  4.6 views/s 1 view to be scanned within 217 ms 10% contingency (overlapping of neighboring views)  f.o.v change < 190 ms X and Z movements during 2 data cycles. A cycle of 170 ms achieved

Optical system Objective: 50x Nikon immersion oil with N.A. 0.9 and W.D. 400 µm Illumination system below the table developed jointly with the Nikon-Italy: tungsten halogen lamp with computer controlled power supply image of the lamp filament focused on the aperture diaphragm of a condenser which concentrates the light into a cone illuminating the emulsion sheets Mikrotron CMOS camera: 1280 x 1024 pixel images at up to 500 fps 377 fps and 8-bit gray level images lead to 471 MB/s

Software Improvements in terms of speed obtained by an asynchronous data- taking scheme: parallel execution of several tasks Execution proceeds along 4 independent steps, synchronized at the end of each cycle A) move the optical system along the vertical axis during the grabbing; at the end of the image taking, it resets the Z position and move X and Y to the next field of view (stop and go) B) acquire images through the frame grabber C) image processing D) loads the processed image of the previous field of view and performs cluster and track recognition

Measurements Base-track to micro-track slope difference for perpendicular (left) and 400 mrad inclined tracks (right) Base-track angular and position accuracy as a function of the angle (10 GeV  - beam at CERN)

Emulsion and base thickness Cluster profile after a smoothing procedure Derivative of the cluster profile flat distribution except at the edges (maximum and minimum) mean values computed over a 3  region around maximum and minimum  emulsion edges relative accuracy of ~ 0.2% Correction especially effective on large angle tracks µm

Position and angular accuracy X projectionY projection 0.05 µm Straight tracks (up to 50 mrad) Median ~ 0.4 mrad 200 mrad inclined tracks 0.6 mrad 300 mrad inclined tracks 0.9 mrad Residual of base tracks w.r.t. fitted tracks Nucl. Instrum. Meth. A554 (2005) 247

Conclusions The ESS working since 2004 when the first prototype was developed The system is capable of scanning 20cm2/hour with a routine accuracy of 2 mrad in angle About 15 systems operative in Europe A similar system devoted to precision measurements is also available Currently scanning OPERA and PEANUT films