1. The Principle of Operation of the LB 124 Scint LB 124 Scint
2
1.2 The Principle of Operation of Scintillation Counters
With conventional scintillation counters the radiation to be
measured hits one or several scintillator layers. The flashes of
light which are created in this process are propagated – either
directly, or bundled by a suitable reflector – to a photomultiplier
and measured.
Former state of the art
To be able to measure alpha as well as beta and gamma radia-
tion, so-called sandwich detectors have been used which com-
prise two layers: ZnS for the alpha radiation and plastic scintilla-
tors for the beta and gamma radiation, with the ZnS layer facing
the sample.
The drawbacks of this method are the low sensitivity to the low-
energetic beta radiation, which has to pass through the ZnS
layer, and inadequate discrimination of the radiation types
(strong spillover effects in the beta channel) as well high pro-
duction costs.
New measuring method by B
ERTHOLD TECHNOLOGIES
The Contamination Monitor LB 124 Scint is using a single scin-
tillator made of zinc sulphide (ZnS) to measure radioactivity.
The radiation to be measured hits the scintillator. The flashes of
light created in this process are passed to a photomultiplier via
a suitable reflector with suitable preamplifier and discriminator
stage and measured. The individual types of radiation, i.e. al-
pha and beta, gamma, X-ray radiation, can be distinguished
by means of special evaluation and correlation circuits, and
thus separated and measured at the same time. The spillover of
alpha particles into the beta channel is corrected by the soft-
ware, so that only the beta-gamma parts of the alpha sources,
i.e. Am-241, will be indicated in the beta channel.
The benefits of this method are:
¾ high measurement accuracy
¾ exact distinction of the types of radiation and the individual
nuclides (very low spillover)
¾ high sensitivity even at low energies
¾ the negligible spillover of Alphas into the Beta channel
¾ low costs for the scintillator and
¾ ease of maintenance.
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