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Schematic drawing IRGprobe

The IRGprobe system consists of the radon gas probe and a case with power supply, sampling pump, printer, keyboard and optional battery.  The microcomputer of the intelligent probe controls the measurement, evaluates the data and prints directly the results.

Radon in soil

For measurements in the soil a hand operated drilling tool and an set of stainless steel tubes can be ordered. A hole is drilled into the ground, a stainless steel tube is inserted, and the probe is shifted into the tube. The top of the tube is closed, and the space between tube and the wall of the bore-hole must be sealed with filling material. If the soil is too wet the probe can be pulled up, to protect the detector from water.


Drawing of sample probe

The probe of the IRGprobe system is a self contained instrument with all elements of an intelligent data collection system and an alpha-spetrometer including:

  • Inlet filter
  • Decay chamber
  • Silicon surface barrier det
  • Detector voltage generator
  • Charge sensitive amplifier
  • Multichannel analyser
  • Integrated flow meter
  • Real time clock
  • Microcomputer
  • Communication interface

The figure shows a cross section of the cylindrical probe. The radon gas enters the decay chamber via the inlet filter. In the passive mode the radon enters by diffusion. In the active mode the gas is sucked in by the pump of the supply case which is also controlled by the micro computer.

The radon in the chamber decays into its daughters which deposit at the walls of the chamber and at the detector surface. The integrated multichannel analyser collects continuously the alpha-spectrum of the deposited activity. The micro-computer analyses the spectrum and calculates the gas activity from the collected Po-218, Po-214 and Po-212 activities. It prints directly the concentrations of Rn-222 and Rn-220 (thoron).

In the active mode the micro computer increases the air flow rate in predefined steps and prints or plots the activity concentration as a function of the flow rate. This function is one information which is needed to predict the radon concentration in a hypothetical house at the given location.

Measuring method

The IRGprobe uses the double filter method with an inlet filter, a decay chamber, and a second filter which collects the progeny, growing in the chamber. The inlet filter is a mechanical filter. The deposition of the progeny by diffusion acts as the second filter. The air sampling is done by diffusion or by a variable air flow.