390
A. Ariga et al.
camera systems to read out the emulsion tracks and reconstruct three-dimensional
vectors by measuring X, Y , θ X , θ Y , with Z the emulsion depth. Computers were only
used to assist an operator in performing the track measurements and to provide the
micro-metric movement of the microscope stage. Relative alignment was performed
by fiducial X-ray marks combined with the precision measurement of the film edge
positions. Typical thickness of the double-sided emulsion plate was 1 mm or larger,
so allowing to follow-up tracks with a given angle w.r.t. the emulsion plane by
varying the focal plane of the objective lenses. The video-camera was used to grab
the image from the objective lens with a rather time-consuming procedure. An
operator had to manually adjust the video-image on the visually detected track,
while dark spots could be automatically detected. The TV screen also allowed to
run graphic tools for measuring track positions and angles.
The mechanical stability of the ECC sandwich was ensured by a vacuum packing
paper known as “origami”, also required to isolate the emulsion films from the
external light, humidity and polluting gases. Plate-to-plate alignment was performed
by X-ray lines and/or X-ray spots typically from a 55 F e source. The association
between the ECC and the electronic detectors was accomplished by joining particle
tracks, better if of high momentum and hence less affected by Multiple Coulomb
Scattering. In this respect, the idea of using interface emulsion plates in between
the ECC module and the electronic detectors has proven to be very effective. These
interface films were called Changeable Sheets (CS) because they were frequently
replaced during the physics run in order to limit the integration of background tracks
and to easily identify tracks found in the electronic detectors. This concept was first
applied in the E531 experiment at Fermilab [32], as we will see in the following,
and it is presently being used in several applications also for large scale ECCs.
9.3 Notable Experiments Employing Nuclear Emulsions
During the 1970s, emulsion detectors of increasing mass and complexity were
developed for applications to particle physics experiments conducted at particle
accelerators with experimental setups also including electronic detectors (hybrid
experiments). Emulsions are often employed as active targets with high spaceresolution, and the electronic detectors, namely trackers, calorimeters and spectrometers, are used to pre-select or trigger specific events in the emulsions and to
complement the kinematical information of the events.
In early experiments with accelerators, nuclear emulsions were coupled to spark
and bubble chambers in order to reduce the total scanning time. We recall here the
observation of the decay of a charmed particle produced in a high-energy neutrino
interaction in a Fermilab experiment [33]. The latter was performed in the wideband neutrino beam produced by 400 GeV protons, by using a detector made of
spark chambers placed downstream of nuclear emulsion stacks. Stacks containing
altogether 16 l of ILFORD X5 emulsion made up of pellicles of 20 cm × 8 cm
× 0.6 mm dimensions were placed in association with a double wide-gap spark
A. Ariga et al.
camera systems to read out the emulsion tracks and reconstruct three-dimensional
vectors by measuring X, Y , θ X , θ Y , with Z the emulsion depth. Computers were only
used to assist an operator in performing the track measurements and to provide the
micro-metric movement of the microscope stage. Relative alignment was performed
by fiducial X-ray marks combined with the precision measurement of the film edge
positions. Typical thickness of the double-sided emulsion plate was 1 mm or larger,
so allowing to follow-up tracks with a given angle w.r.t. the emulsion plane by
varying the focal plane of the objective lenses. The video-camera was used to grab
the image from the objective lens with a rather time-consuming procedure. An
operator had to manually adjust the video-image on the visually detected track,
while dark spots could be automatically detected. The TV screen also allowed to
run graphic tools for measuring track positions and angles.
The mechanical stability of the ECC sandwich was ensured by a vacuum packing
paper known as “origami”, also required to isolate the emulsion films from the
external light, humidity and polluting gases. Plate-to-plate alignment was performed
by X-ray lines and/or X-ray spots typically from a 55 F e source. The association
between the ECC and the electronic detectors was accomplished by joining particle
tracks, better if of high momentum and hence less affected by Multiple Coulomb
Scattering. In this respect, the idea of using interface emulsion plates in between
the ECC module and the electronic detectors has proven to be very effective. These
interface films were called Changeable Sheets (CS) because they were frequently
replaced during the physics run in order to limit the integration of background tracks
and to easily identify tracks found in the electronic detectors. This concept was first
applied in the E531 experiment at Fermilab [32], as we will see in the following,
and it is presently being used in several applications also for large scale ECCs.
9.3 Notable Experiments Employing Nuclear Emulsions
During the 1970s, emulsion detectors of increasing mass and complexity were
developed for applications to particle physics experiments conducted at particle
accelerators with experimental setups also including electronic detectors (hybrid
experiments). Emulsions are often employed as active targets with high spaceresolution, and the electronic detectors, namely trackers, calorimeters and spectrometers, are used to pre-select or trigger specific events in the emulsions and to
complement the kinematical information of the events.
In early experiments with accelerators, nuclear emulsions were coupled to spark
and bubble chambers in order to reduce the total scanning time. We recall here the
observation of the decay of a charmed particle produced in a high-energy neutrino
interaction in a Fermilab experiment [33]. The latter was performed in the wideband neutrino beam produced by 400 GeV protons, by using a detector made of
spark chambers placed downstream of nuclear emulsion stacks. Stacks containing
altogether 16 l of ILFORD X5 emulsion made up of pellicles of 20 cm × 8 cm
× 0.6 mm dimensions were placed in association with a double wide-gap spark