Development of high sensitivity radon detector by using of the membrane degasifier module and research for the pre-seismic phenomena.

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The hollow membrane or the stainless steel ball was used in order to improve the degasifier efficiency of the dissolved radon gas in the underwater radon detector. And the capacity of the electrostatic collection vessel from 1 liter was enlarged in 70 liters. The supplied voltage from -120V was increased in -1500V. The sensitivity of the underwater radon detector was increased 100 times or more. The new underwater radon detector was installed in the radon Observation facility of below-mentioned 4 places, 1) "Heisei-Hotspa" in Fukui, 2) "Kamioka mine" in Gifu, 3) "Kawaue" in Gifu, 4) "Wari-ishi Hotspa" in Gifu Prefecture. The underground water is stably supplied to the radon detector in these observation facilitie.The hot spring has flowed with the water flow rate of the 150 liters per minute at the "Heisei hot spa", and the count rate of the ^<214>Po increased in approximately 130 times after the exchanging to the super high sensitivity underwater radon detector. The dissolved gas capa … More city in the hot spring increased suddenly from around November of 2001 at the "Heisei hot spa". The being 3 stages, calm, mid and bumping period was ascertained in the dissolved gas capacity from the flow fluctuation analysis of the electromagnetic flow meter. Bumping period was July 19th from July 4th of 2002, and November 9th from October 12th of 2002. After the bumping period, the period of August 5th from July 18th of 2002 and November 10th from November 19th, water radon concentration increased suddenly. From the observation point below-mentioned two earthquakes occurred the within approximately 50 km. (1) North of Fukui Prefecture, Magnitude 4.5 at August 18th of 2002, (2) South of Ishikawa Prefecture, Magnitude 4.5 at November 17th of 2002. Bumping the dissolved gas capacity and, after that sudden increase of radon density was observed before about 1 month of earthquake occurrence. This observation result is thought it is the new earthquake pre-seismic phenomenon which was observed making use of the high sensitivity underwater radon detector. As for radon observation result below-mentioned URL, It is open with the http://111.physics.gifu-u.ac.jp/. Less