Ronan X96S DENSITY GAGE - Manual (Page 55)

Density Gage Manual 012407 51
Detector
Scintillator Detector
Description The Ronan scintillation detector consists of three main
components: The plastic scintillation crystal, the
photomultiplier tube (PMT), and the associated
electronics.
Scintillation Crystal The crystal used for the Continuous Level Monitor
System is polyvinyl toluene (PVT) plastic. The crystal
produces light pulses which are proportional to the
incident radiation events striking it.
Typically mounted in s stainless steel shell the entire
crystal assembly is sealed against moisture and dirt and
is non-repairable. An integral flange serves to mount
the crystal to the PMT. A special silicone membrane
serves as an optical coupling medium between the
crystal and the PMT.
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Photomultiplier Tube The PMT is a light sensitive vacuum tube with a
photosensitive layer that converts the light pulses to an
electrical current. Light pulses from the crystal strike
the photosensitive layer and release electrons. A high
voltage power supply connected to the photosensitive
layer accelerates the electrons through stages of current
amplification.
The PMT and its associated components are housed in a
special magnetic shield. The tube is shock-mounted
internally, with an interface plate at the top, which also
mounts the electronics and the outer shell.
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Electronics Four boards, housed in a stainless steel shell, comprise
the electronics and their functions.
’ High Voltage Power Supply
’ Preamplifier
’ Discriminator
’ Pulse Output