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Radon/Thoron discrimination mode (only DF2000)
The measuring and evaluation procedure - for continuously differentiating radon
from thoron in the ambient air -
makes use of the significant difference in
the half-
lives of these nuclides (radon: 3,8 days, thoron: 55 sec.). This measuring mode
requires splitting the applied quasi-continuous 10min measuring cycle into three
subsequent phases. For speedy filling the measuring chamber during the first
phase the internal pump of AlphaGUARD is used.
The main challenge of the setup with this mode is to get as much thoron as possible
into the chamber during the pump operation period (first 3 minutes of each 10 min
measuring cycle). It is important to avoid that appreciable fraction of this noble
gas decays on its way into the measuring chamber due to the short half-life of
thoron (55 seconds).
This is obtained by flushing the air into the chamber on the most direct way and
by using the highest available pump rate (2 l/min).
Following preparatory configuration measures are necessary:
x Check if flow through adapter is mounted. If not, unscrew the diffusion
adapter by hand and screw the flow through adapter by using the
hexagon key (see Figure 50).
x Start the AlphaGUARD by pushing the ON/OFF button
x Check if set operation mode is OK (10 min, flow, Radon/Thoron). If
change the required operation mode via menu (see 7.2.3) or
by means of a PC connected to the AlphaGUARD using DataVEIW or
DataEXPERT software (see DataVIEW or DataEXPERT manual).
x If mains operatio
n is required (when battery is discharged and/or for long
term operation) simply connect the mains adapter.
The status of the pump operation is indicated by a pump symbol in the upper right
of the screen. Following states are possible:
Flow mode activated, pump flow within operational limits
Flow mode activated, flow of the pump disturbed (e.g. by sharp
bended tubes) or hardware problem with pump module
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