56
P. Lecoq
of the detector design and of the software corrections, and temperature gradients
between the front and back face of the crystals introduce non-uniformity affecting
the resolution.
Finally, for large scintillator volumes cost considerations are of importance.
The abundance of the raw materials, the facility to purify them against the most
detrimental impurities to achieve good radiation hardness, a low temperature
melting point to save on the energy cost, a high growing and mechanical processing
yield are all parameters, which deserve particular attention.
3.1.3.2 Astrophysics and Space
Increasingly crystal-based calorimeters are embarked on satellites to study galactic
and extra-galactic X- and γ-ray sources. This requires excellent energy resolution
over a wide energy spectrum, typically from a few KeV to several TeV (see for
instance Fig. 2.16 of ref. [11] for a list of different space missions with their
respective energy range). One major aim of these measurements is the determination
of the direction of the γ-ray source. Two classes of position sensitive devices have
been developed in the last decades. These designs are using continuous scintillation
crystal or pixilated detector geometries [12]. The required angular resolution is
achieved with multilayer calorimeters or readout schemes to provide depth of
interaction (DOI) information or using coded aperture masks.
The low orbit satellites are shielded by the earth magnetic field, relaxing therefore
the requirement for radiation hardness of the scintillation material. Most of the
scintillation materials can be used depending on the energy range of the detected
γ-radiation. However, the payload is limiting the size of such detectors and not too
dense materials are sometimes selected to reduce the weight.
In the interplanetary space the sun wind from charged particles strongly influences the detecting requirements of the scintillation materials. For these missions,
high radiation hardness to ionizing radiation and low level of induced radioactivity
are required. The same applies to detectors for planetary missions.
The general trend is to select high light yield, fast and not necessarily ultradense scintillators such as CsI or YAP. The very bright LaBr 3 is likely to find
some applications in this domain because of its excellent low energy resolution
(comparable to solid state detectors). BGO is very often used in veto counters for
the rejection of Compton events.
3.1.3.3 Spectrometry of Low Energy γ-Quanta
This is probably the most important application domain for inorganic scintillators.
The key requirement concerns energy resolution on the photopeak. It is therefore
essential to maximize the photofraction and high Z materials are clearly preferred
(see Sect. 3.1.1).
P. Lecoq
of the detector design and of the software corrections, and temperature gradients
between the front and back face of the crystals introduce non-uniformity affecting
the resolution.
Finally, for large scintillator volumes cost considerations are of importance.
The abundance of the raw materials, the facility to purify them against the most
detrimental impurities to achieve good radiation hardness, a low temperature
melting point to save on the energy cost, a high growing and mechanical processing
yield are all parameters, which deserve particular attention.
3.1.3.2 Astrophysics and Space
Increasingly crystal-based calorimeters are embarked on satellites to study galactic
and extra-galactic X- and γ-ray sources. This requires excellent energy resolution
over a wide energy spectrum, typically from a few KeV to several TeV (see for
instance Fig. 2.16 of ref. [11] for a list of different space missions with their
respective energy range). One major aim of these measurements is the determination
of the direction of the γ-ray source. Two classes of position sensitive devices have
been developed in the last decades. These designs are using continuous scintillation
crystal or pixilated detector geometries [12]. The required angular resolution is
achieved with multilayer calorimeters or readout schemes to provide depth of
interaction (DOI) information or using coded aperture masks.
The low orbit satellites are shielded by the earth magnetic field, relaxing therefore
the requirement for radiation hardness of the scintillation material. Most of the
scintillation materials can be used depending on the energy range of the detected
γ-radiation. However, the payload is limiting the size of such detectors and not too
dense materials are sometimes selected to reduce the weight.
In the interplanetary space the sun wind from charged particles strongly influences the detecting requirements of the scintillation materials. For these missions,
high radiation hardness to ionizing radiation and low level of induced radioactivity
are required. The same applies to detectors for planetary missions.
The general trend is to select high light yield, fast and not necessarily ultradense scintillators such as CsI or YAP. The very bright LaBr 3 is likely to find
some applications in this domain because of its excellent low energy resolution
(comparable to solid state detectors). BGO is very often used in veto counters for
the rejection of Compton events.
3.1.3.3 Spectrometry of Low Energy γ-Quanta
This is probably the most important application domain for inorganic scintillators.
The key requirement concerns energy resolution on the photopeak. It is therefore
essential to maximize the photofraction and high Z materials are clearly preferred
(see Sect. 3.1.1).