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Results from Prototypes of Some Environmental and Health Related Alarm Devices Based on Gaseous Detectors Operating in Air in Counting Mode
G. Charpak, P. Benaben, P. Breuil, P. Martinengo, E. Nappi, V. Peskov
The main requirements for some environmental and public health alarm and monitoring devices, especially those meant to be massively applied (for example monitoring of Rn concentration in air or early detection of the appearance in air of dangerous gases) are high sensitivity, simplicity and low cost. In the attempt to meet these requirements, our group developed prototypes of several devices based on micropattern or wire-type detectors operating in air in pulse counting mode. It must to be noticed that several commercial detectors operating in air in ionization chamber mode (gas gain =1) already exist, i.e. smoke detectors, various medical dosimeters, etc. The novelty which we have introduced is to exploit such devices in pulse counting mode enabling considerably, in some cases orders of magnitude, to increase of their sensitivity, at the same time preserving the simplicity and low production cost. Based on our studies we have found conditions at which micropattern and wire-type detectors can operate stably in air at high gas gains despite of natural changes in the atmospheric pressure and humidity level. Several prototypes were built and successfully tested; descriptions of some of our earlier prototypes and results obtained are reported in literature [1-3].
In this report we will present our latest yet unpublished results obtained in this direction.
. The main focus was on the development of cheap and robust Rn detectors designed for early predicting earthquakes and detecting dangerous gases in the environment.
It is generally accepted that Rn accumulated in buildings, especially in the basements, may cause a significant risk to the human health. Nowadays, most of the massively used Rn detectors are accumulative types which are acquired after some time interval (up to 90 days). In our work, however, we focus not only on developing fast online Rn monitors for the healthy safety, but mainly on another subject also related to Rn and which requires massive use of fast detectors operating in online mode. In the last decade or so, some researches have looked at elevated soil gas Rn concentration or rapid changes in soil or groundwater Rn concentration as a predictor of earthquakes To verify these early observations of the correlation between the earthquake and the Rn appearance on a more solid statistical ground one has to create a wide networks of cheap, compact, fast and high sensitivity Rn monitors. The existing commercial Rn detectors do not fulfil these requirements. The new design developed by us recently has sensitivity a few times higher than the best commercial detectors, but at the same time much simpler and cheaper in production. Note that it is very different from the earlier version described in [1, 3] and not only more sensitive, but also is capable to operate in 100% humid air.
The detector of dangerous gases combines the basic principle of a standard PID [4] (gas photoionization) enforced with several new features: for example with simultaneous gas absorption measurements and with the utilization of UV radiation with a wavelength shorter than the cut off of the air transmission. In combination with the counting mode (our earlier version [2] operated with some gas gain, but in current mode) of the operation this allows an increase of the sensitivity up to 1000 times (and even more for some particular gases).
Obtained results let us believe that due to the exceptionally high sensitivity, simplicity, robustness and low cost, such new devices will find massive applications. We will report our current affords on establishing contacts with industry in attempt to commercialize these detectors.
References:
[1] G Charpak et al., JINST 3 P02006, 2008
[2]G. Charpak et al., IEEE Trans. on Nucl. Sci, 55, 2008, 1657
[3] G Charpak et al ., arXiv:0909.2480, 2009
[4] http://www.shsu.edu/~chemistry/PID/PID.html
