Photodiode detectors
The
advantages and limitations of photodiode detectors were discussed in section 4.2 . In general, photodiode
scintillation detectors consist of a small PIN photodiode, integrally coupled to a
scintillation crystal, often CsI(Tl). As a standard rule, a charge sensitive preamplifier
is incorporated in the assembly.
FEATURES
The intrinsic noise of the photodiode/preamplifier combination prohibits the use of
large scintillation crystals for detection of low energy (< 1 MeV) gamma-rays. This
noise determines the lowest energy that can be detected with the device. CsI(Tl) crystals
of 1 cm3 coupled to 10x10 mm2 PIN photodiodes can be used down to 40
keV; for larger crystals (e.g. for 2x2x2.5 cm3 coupled to 18x18 mm2
diodes), this energy is about 70 keV.
APPLICATION
Photodiode scintillation detectors
can be used e.g. in applications where:
- No high voltage is available or desired (medical applications)
- Stable gain is essential (long term environmental monitoring)
- High magnetic fields are present (physics research)
- A rugged detector is required.
CsI(Tl)
crystals do not crack or cleave and photodiodes are shock resistant. Many configurations
are possible. The noise level and energy resolution of the detector depend very much on
the crystal/diode configuration. Contact SCIONIX for your specific requirement. The noise
of photodiode scintillation detectors increases with temperature. Above 50 o C
these instruments are not advised.
An important application
of photodiode detectors is in physics research for the detection of charged particles. A
thin silicon detector is placed in front of a CsI(Tl) crystal read out with a photodiode
to perform an E / D E measurement. |