Ronan X96S MOLD LEVEL GAGE - Manual (Page 46)

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Detector
Scintillator Detector
Description The Ronan scintillation detector consists of three main components: The
plastic scintillation or NaI (sodium iodine) crystal, the photomultiplier tube
(PMT), and the associated electronics.
Scintillation Crystal
The crystal used for the Continuous Mold Level Monitor System is either
NaI (sodium iodine) or 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 Four boards, housed in a stainless steel shell, comprise the electronics and
their functions.
• High Voltage Power Supply
• Preamplifier
• Discriminator
• Pulse Output