7.6 Silicon- and Germanium Lithium-Drifted Detectors
129
limits the use of Ge (Li) for measuring very low energy X -ray, while for energies
above 20–30 KeV, higher efficiency of measurement makes them preferable to a Si
(Li) detector.
7.7 Nuclear Emulsion Techniques
In radiochemical work, sometimes it is necessary to separate the constituents of
the mixture before carrying out any radioactive measurements. This is normally
done using the paper chromatography technique. In such paper chromatography
technique, it is also necessary to establish the position of various components of the
radioactive mixture which has moved over the chromatography paper. Sometimes it
is also necessary to measure a cumulative radiation dose received by the personnel
working in a radiochemical laboratory. In all such cases, it becomes difficult to
measure radioactivity by the techniques discussed previously. For these types of
specific requirements, nuclear emulsion techniques and other related techniques are
normally adopted. We shall now concentrate on these techniques in some detail.
7.7.1 Silver Grains in Photographic Plate by α-Particles
When charged particles pass through a photographic emulsion, they produce latent
images along their path. Upon development of the film, a grain of silver appears
along the tracks of the particles. A lot of valuable information can be obtained from
the study of the tracks. Counting individual particles along the paths gives a measure
of the number of nuclear particles entering the plate. A study of the detailed structure
of the track leads to the determination of mass, charge, and energy of the particle.
Film sensitivities are controlled primarily with sensitizers.
The energy of α-particles causing blackening of the photographic plate can be
calculated by measuring accurately the range of each track. The energy loss by αparticle can be calculated by counting the grain present in each track, because the
rate of energy loss is proportional to the number of grains developed per unit path
length.
In addition, the sensitivity of a given type of film can be varied within wide limits
by techniques used for developing the track. The development of film, however, needs
special care so that tracks are not lost or twisted during development. The shrinkage
of the film during drying is avoided by soaking the film in glycerin, which fills up
all the voids, which are left by the removal of the unsensitized silver halides.
129
limits the use of Ge (Li) for measuring very low energy X -ray, while for energies
above 20–30 KeV, higher efficiency of measurement makes them preferable to a Si
(Li) detector.
7.7 Nuclear Emulsion Techniques
In radiochemical work, sometimes it is necessary to separate the constituents of
the mixture before carrying out any radioactive measurements. This is normally
done using the paper chromatography technique. In such paper chromatography
technique, it is also necessary to establish the position of various components of the
radioactive mixture which has moved over the chromatography paper. Sometimes it
is also necessary to measure a cumulative radiation dose received by the personnel
working in a radiochemical laboratory. In all such cases, it becomes difficult to
measure radioactivity by the techniques discussed previously. For these types of
specific requirements, nuclear emulsion techniques and other related techniques are
normally adopted. We shall now concentrate on these techniques in some detail.
7.7.1 Silver Grains in Photographic Plate by α-Particles
When charged particles pass through a photographic emulsion, they produce latent
images along their path. Upon development of the film, a grain of silver appears
along the tracks of the particles. A lot of valuable information can be obtained from
the study of the tracks. Counting individual particles along the paths gives a measure
of the number of nuclear particles entering the plate. A study of the detailed structure
of the track leads to the determination of mass, charge, and energy of the particle.
Film sensitivities are controlled primarily with sensitizers.
The energy of α-particles causing blackening of the photographic plate can be
calculated by measuring accurately the range of each track. The energy loss by αparticle can be calculated by counting the grain present in each track, because the
rate of energy loss is proportional to the number of grains developed per unit path
length.
In addition, the sensitivity of a given type of film can be varied within wide limits
by techniques used for developing the track. The development of film, however, needs
special care so that tracks are not lost or twisted during development. The shrinkage
of the film during drying is avoided by soaking the film in glycerin, which fills up
all the voids, which are left by the removal of the unsensitized silver halides.