40
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 Weigh System is poly vinyl
toluene (PVT) plastic. The crystal produces light pulses
which are proportional to the incident radiation events
striking it.
Typically mounted in a 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.
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
Two to four boards (depending on the scintillator type,
housed in a stainless steel shell, comprise the electronics
and their functions.
•
High Voltage Power Supply
•
Preamplifier
•
Discriminator
•
Pulse Output
