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3 System Description
LB 470RID Level
20
56925-1BA2 Rev.02, 05/2021
3.3.2
Interference Radiation and Pulse Height Analysis
Ionizing radiation registered by the detector which does not come from the meas-
uring source is called interference radiation. In the testing of welds and other
material testing, radioactive sources of very high activity (up to 100 Ci) are used.
These applications almost always use low energy radiation sources for example, Ir-
192 or Se-75. In contrast, the Nuclides used in the level measurements, in particular
Co-60, are high energetic radiation sources, with much lower activity.
An analysis of the voltage pulses (pulse amplitude or "height") registered by the
detector permits a differentiation between interference radiation and measuring
radiation since the pulse height is dependent on the energy of the isotope. The
pulse height spectrum in illustration 3 shows the distribution of the pulse heights
generated by gamma radiation from Co-60 or Ir-192 sources in a rod detector with
plastic scintillator. On account of the high radiation energy, the spectrum of Co-60
includes big pulse heights, as opposed to pulse heights for an Ir-192 source. In the
pulse height spectrum from illustration 3, practically no Ir-192 pulses lie above a
height of 700 mV. The energy of Se-75 is below Ir-192 and generates even lower
pulse heights.
Fig. 2
Pulse Height Spectrum
All pulses above the measuring threshold contribute to the count rate in the meas-
uring channel. When Ir-192 interference radiation influence is present, all Ir-192
pulses are also counted. This causes the level measurement in the vessel to read too
low.
Содержание DUO XPERT LB 470RID
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Страница 12: ...1 About this Operating Manual LB 470RID Level 12 56925 1BA2 Rev 02 05 2021...
Страница 16: ...2 Safety LB 470RID Level 16 56925 1BA2 Rev 02 05 2021...
Страница 34: ...3 System Description LB 470RID Level 34 56925 1BA2 Rev 02 05 2021...
Страница 42: ...4 Installation LB 470RID Level 42 56925 1BA2 Rev 02 05 2021...
Страница 199: ...Unit d valuation D tecteurs LB 47x LB 4700 Informations sur la s curit 56925BA59 Rev No 04 09 2019...
Страница 207: ...Level F llstand Technical Information Technische Information 56925TI1L Rev No 04 05 2021...
Страница 235: ...LB 470RID Level LB 470RID F llstand Technical Information Technische Information 56925TI1L Rev 04 05 2021 28...
Страница 236: ...Technical Information Technische Information LB 470RID Level LB 470RID F llstand 29 56925TI1L Rev 04 05 2021...
Страница 238: ...Technical Information Technische Information LB 470RID Level LB 470RID F llstand 31 56925TI1L Rev 04 05 2021...