The
LXT Group
Real
Time Radiation Measurements
The LXT Group has established a
continuous surveillance station for radiation in North San Diego
County. An Aware Electronics
Geiger Counter has been interfaced with a system that acts as a data
acquisition front end. An application reads the data and formats
web pages for display on a periodic basis. The Geiger Counter
is measuring radiation in the ambient air. The mean value of
radiation
measured is approximately 12 microRoentgens per hour.
Aware Electronics is found at www.aw-el.com
in September of 2003 anomalous
readings were received so the Geiger counter sensor was replaced.
Normal operations continued.
In March of 2005 a fire truck
in North San Diego County detected radiation coming from a car.
The vehicle was stopped in Escondido
and surrounded by Escondido Police and San Diego County Sheriffs behind
a Home Depot store on Valley Parkway (Zip code 92027). The passenger in
the car had just received medical care using
radioactive isotopes. In order to assess this "false positive" problem
an experiment was done with a volunteer who had just received an
injected dose of Technetium 99, a Gamma emitter of 140.5 Kev photons.
Tc99 has a half life of about 6 hours. At intervals of a few
hours the
patient stood within 30 cm of the Geiger counter. Radiation was
observed at over 5000 microRoentgens per hour.
- Click here to see the data. The
exponential decay of the Tc99 is readily observed.
- A PDF reference on the Tc99
source can be found here.
In early July of 2005 there was an increase
in the background radiation from about 11.5 to 13.5 microR/hr. The
cause of the increase was a tear in the protective plastic the
surrounds the RM-70 sensor. This allowed dust to get in and it allowed
alpha and low energy beta radiation to enter the detector. The
plastic was replaced July 7th, 2005. The RM-70 was also cleaned with
compressed air. The background radiaton returned to normal levels.
In November of 2005 there were
a couple of false peaks, caused by battery failure. The battery was
replaced on November 16, 2005.
Please send us your questions and comments to lxtgroup(at)cox.net
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