1. OPERA scanning session, CERN 03/05/06 DB-driven Scan-back with collar Nikon dry obj

2. OPERA scanning session, CERN 03/05/06 Scan back with a NIKON dry objective (collar correction) Nikon ELWD PlanFluor magnification: 40x (nominal) numerical aperture: 0.60 working distance: 1.8 mm correction range: 0-2 mm Similar to the Zeiss already tested but… -The magnification dependency on the correction is lower -The focal plane vertical position dependency on the correction is larger (~ 40 µm). The DC motor, drive belt and serial motor controller used for Zeidd have been mounted in a Nikon microscope. Working conditions: two collar position c.c. 0.0 for the TOP scanning c.c. 0.3 for the BOTTOM scanning

3. OPERA scanning session, CERN 03/05/06 Further improvements and new problems SOFTWARE VERTIGO SCAN 4 (collar correction version) has been further upgraded to take into account also the focal plane shift along the vertical axis due to the correction (~ 40 µm). This effect behaves as a large base shrinkage during the top-bottom linking with the DB-driven processing tools. The exact value of the shift is difficult to be evaluated directly, and has been tuned during the scan back. MECHANICS Some problems occurred during the scan back: - The objective holder (revolver) was not stable when the collar position changes (  little horizontal shift of the bottom field of view). It has been finally blocked with a clamp - Furthermore, sometimes the objective has been found unscrewed. These problems suggest to substitute the revolver with a more stable single objective holder.

4. OPERA scanning session, CERN 03/05/06 Comparison with previous scan backs: PASSING-THROUGH Scan back performed on – MIC1 : Zeiss dry microscope – MIC2 : oil microscope – MIC3 : oil microscope – MIC4 : Nikon dry microscope with the same intercalibration, tolerances and drivers Out of 325 predictions … P = passing through X = stopping Mic1Mic2Mic3Mic4 PPPP 203 XPPP 13 PXPP 10 PPXP 8 PPPX 20 XXPP 2 XPXP 5 XPPX 1 PXXP 1 PXPX 2 PPXX 3 PXXX 0 XPXX 1 XXPX 0 XXXP 2 XXXX 54 tot. 325 FAKE STOPPING (± 2 %) : MIC1 : 24 / 271 ( 9 % ) MIC2 : 17 / 271 ( 6 % ) MIC3 : 20 / 271 ( 7 % ) MIC4 : 27 / 271 (10 % ) Normalized only with respect to the passing- through sample

5. OPERA scanning session, CERN 03/05/06 325 Followed tracks 244 Passing (75%) 81 Stopping (25%) 25 Stopping before Plate 10 56 Stopping 10>Pl<53 23 Passing 10 because inefficiency 13 because BK 33 Possible Interactions 5 “strange” events 28 real interactions MIC4 scan back results: 325 Followed tracks 251 Passing (77,2%) 74 Stopping (22,8%) 23 Stopping before Plate 10 51 Stopping 10>Pl<53 13 Passing 6 because inefficiency 7 because BK 38 Possible Interactions 4 “strange” events 34 real interactions MIC3 scan back results:

6. OPERA scanning session, CERN 03/05/06 Event classification: 28 interact. 11 vertexes 1 vx 4 prong No parent 2 vx 2 prong8 vx 3 prong 1 vx with no parent 7 vx with parent 5 scattered12 stopping Event classification: 34 interact. 15 vertexes 1 vx 4 prong No parent 3 vx 2 prong 11 vx 3 prong 1 vx with no parent 10 vx with parent 5 scattered14 stopping

7. OPERA scanning session, CERN 03/05/06 Conclusions A scan back with a collar correction nikon dry objective has been performed. The preliminary results are comparable with the previous scan back obtained with oil obj. The number of “fake” stopping points is a bit larger (15% instead of 11%) mostly due to the larger background. The scan back should will be repeated soon in more stable mechanical conditions.