FlowStar2 LB 514
2. HPLC Monitor
21
2.2 Radioactivity Detector
Nuclear radiation is detected using a scintillation counter, plus a coinci-
dence circuit.
The eluate passes through the measuring cell located between the cath-
odes of two photomultipliers. The radiation in the eluate excites lumines-
cent substances (e.g. scintillator grit, liquid scintillator) and triggers flashes
of light whose photon number is proportional to the radiation intensity.
These emitted photons release photoelectrons on the photosensitive layer
of the photomultiplier. These electrons are accelerated by the high voltage
applied and move toward the anode; their impact on a dynode system gen-
erates further electrons. The resulting current pulses are then amplified
and selected in the discriminator. The main task of signal evaluation is to
detect counts caused by radioactive decays and to distinguish them from
counts caused by
Luminescence
Photomultiplier noise
This distinction is achieved by means of the coincidence circuit of two pho-
tomultipliers and through compensation of the pulses caused by random
coincidence.
If the photomultipliers does not work properly, please contact the Berthold
Technologies service (Service hotline: 07081-177-111).
The detector must not be modified by the user!
