400
A. Ariga et al.
lack of accurate measurements of the D s differential production cross section,
DONUT expressed its ν τ cross-section measurement as a function of the parameter
n, responsible for the differential production cross section of D s , as σ const
ν τ
=
2.51n 1.52 ×10 −40 cm 2 GeV −1 . The cross section was estimated to be σ const
ντ
=
(0.39±0.13(stat.)±0.13(syst.))×10 −38 cm 2 GeV −1 , when assuming the value of the
parameter n as derived from PYTHIA 6.1 simulations.
9.5 Present Emulsion Detectors
9.5.1 Fast Scanning Systems and Large-Scale Film Production
As stated above, the advances in the scanning systems aimed at higher efficiency
and speed have led in recent times to the rebirth of the emulsion detectors. A further
generation of the Track Selector, called S-UTS (Super-Ultra Track Selector), was
developed in Nagoya [88]. It is based on highly customized components. The main
feature of this approach is the removal of the stop-and-go process of the stage in
the image data taking, which is the mechanical bottleneck of traditional systems.
To avoid the stop, the objective lens moves at the same constant speed of the stage
while moving also along the vertical axis and grabbing images with a very fast CCD
camera running at 3000 Hz. The optical system is driven by a piezoelectric device.
The camera has a sensor with 512×512 pixels that imposes a smaller field of view
(∼120×120 μm 2 ) to ensure a comparable position resolution (about 0.3 μm/pixel).
The high-speed camera provides a data rate of 1.3 GB/s. This is handled by a
front end image processor that makes the zero-suppression and the pixel packing,
reducing the rate to 150–300 MB/s. A dedicated processing board performs track
recognition, builds micro-tracks and stores them in a temporary device with a rate
of 2–10 MB/s. A computer algorithm links the micro-tracks of different emulsion
layers and writes the resulting tracks in a database that is used as input for physics
analysis. The routine scanning speed is 20 cm 2 /h/layer while one of the S-UTS
systems has reached the speed of 72 cm 2 /h/layer by using a larger field of view,
without deteriorating the intrinsic micrometric accuracy of the emulsion films.
In the framework of the OPERA experiment (see next section), a joint effort of
several European laboratories allowed the development of an automated scanning
system (ESS) that employs commercial subsystems in a software-based framework.
The ESS, derived from a system developed in Salerno [67], is extensively described
elsewhere [89–91]. The microscope is a Cartesian robot, holding the emulsion film
on a horizontal stage movable in X − Y coordinates, with a CMOS camera mounted
on the optical axis (Z), along which it can be moved to change the focal plane with
a step roughly equal to the focal depth of about 3 μm. The control workstation hosts
a motion control unit that directs the stage to span the area to be scanned and drives
the camera along the Z axis to produce optical tomographic image sequences (with
the X − Y stage holding steady). Areas larger than a single field of view (∼300
A. Ariga et al.
lack of accurate measurements of the D s differential production cross section,
DONUT expressed its ν τ cross-section measurement as a function of the parameter
n, responsible for the differential production cross section of D s , as σ const
ν τ
=
2.51n 1.52 ×10 −40 cm 2 GeV −1 . The cross section was estimated to be σ const
ντ
=
(0.39±0.13(stat.)±0.13(syst.))×10 −38 cm 2 GeV −1 , when assuming the value of the
parameter n as derived from PYTHIA 6.1 simulations.
9.5 Present Emulsion Detectors
9.5.1 Fast Scanning Systems and Large-Scale Film Production
As stated above, the advances in the scanning systems aimed at higher efficiency
and speed have led in recent times to the rebirth of the emulsion detectors. A further
generation of the Track Selector, called S-UTS (Super-Ultra Track Selector), was
developed in Nagoya [88]. It is based on highly customized components. The main
feature of this approach is the removal of the stop-and-go process of the stage in
the image data taking, which is the mechanical bottleneck of traditional systems.
To avoid the stop, the objective lens moves at the same constant speed of the stage
while moving also along the vertical axis and grabbing images with a very fast CCD
camera running at 3000 Hz. The optical system is driven by a piezoelectric device.
The camera has a sensor with 512×512 pixels that imposes a smaller field of view
(∼120×120 μm 2 ) to ensure a comparable position resolution (about 0.3 μm/pixel).
The high-speed camera provides a data rate of 1.3 GB/s. This is handled by a
front end image processor that makes the zero-suppression and the pixel packing,
reducing the rate to 150–300 MB/s. A dedicated processing board performs track
recognition, builds micro-tracks and stores them in a temporary device with a rate
of 2–10 MB/s. A computer algorithm links the micro-tracks of different emulsion
layers and writes the resulting tracks in a database that is used as input for physics
analysis. The routine scanning speed is 20 cm 2 /h/layer while one of the S-UTS
systems has reached the speed of 72 cm 2 /h/layer by using a larger field of view,
without deteriorating the intrinsic micrometric accuracy of the emulsion films.
In the framework of the OPERA experiment (see next section), a joint effort of
several European laboratories allowed the development of an automated scanning
system (ESS) that employs commercial subsystems in a software-based framework.
The ESS, derived from a system developed in Salerno [67], is extensively described
elsewhere [89–91]. The microscope is a Cartesian robot, holding the emulsion film
on a horizontal stage movable in X − Y coordinates, with a CMOS camera mounted
on the optical axis (Z), along which it can be moved to change the focal plane with
a step roughly equal to the focal depth of about 3 μm. The control workstation hosts
a motion control unit that directs the stage to span the area to be scanned and drives
the camera along the Z axis to produce optical tomographic image sequences (with
the X − Y stage holding steady). Areas larger than a single field of view (∼300