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Fluctuation in ionization, scintillation and gas proportional scintillation (GPS) yields have been measured in gaseous xenon as a function of the reduced electric field strength E / N in Td (townsend), where E is the electric field strength in volts/cm and N the atomic number density of xenon. 1 Td is defined as 1×10 −17 V cm 2 . The measurements are made under the pressures of 0.1 and 0.2 MPa by a plane parallel ionization chamber (PPIC) equipped with a photo-multiplier tube (PMT) sensitive to VUV photons. It is found that the fluctuation in ionization is largely improved in PPIC if alpha-particles were almost vertically emitted to the plane of the electrode and their track lengths were nearly equal to the distance between the electrodes. The fluctuation in the scintillation is 33.5% (full-width at half-maximum (FWHM)) at the pressure of 0.1 MPa and 35.6% (FWHM) at the 0.2 MPa, respectively, including the fluctuation of 10% (FWHM) in the alpha-particle energy. The season may be attributed to the fluctuations in several parameters on PMT. In GPS, it is turned out that the proportional gain of about 17 photons/electron at 3.8 Td–45 photons/electron at 4.6 Td is easily achieved and its fluctuation is about a few percent. It is equal to twice of that value at the same reduced field in the case of 0.2 MPa. The fluctuation in the photon yields in GPS shows just equal to one of the ionization yields.

In order to identify a daughter ion of Ba+ with laser-induced fluorescence just after a candidate event of double beta decay of 136Xe is found in a liquid xenon ionization drift chamber, the size of the laser beam directed to the vertex position is determined to be 1.6 mm in diameter by simulating the signal amplitudes of scintillation and ionization due to two beta rays with the EGS4 simulation code. The detection efficiencies of the apparatus and the trigger threshold of scintillation signals, which are obtained with the simulation, are also discussed in detail.

Temporal and spatial distribution of 222 Rn and 220 Rn and their progeny concentrations in the open atmosphere, 222 Rn and 220 Rn exhalation rates, radioactivities in soil and underground water, including some meteorological factors, were measured at a spot of high 222 Rn and 220 Rn concentrations to investigate the source and occurrence mechanism. Hourly mean concentrations of 222 Rn and 220 Rn during August 1993 were about 230 Bq m −3 and 130 Bq m −3 at 1 m above ground surface. Diurnal variations were high at daytime and low at nighttime, which gives an inverse variation compared with the typical variation in the normal environment. 222 Rn concentrations varied quickly in a few minutes and reached a maximum of about 14 kBq m −3 . The maximum daily mean 222 Rn concentration at 5 cm above ground surface was 11 kBq m −3 . Concentrations of 218 Po, 214 Pb, 214 Bi, and 220 Rn progeny were 8∼61 Bqm −3 , 1∼7 Bqm −3 , 0.5∼5 Bq m −3 , and 0.02∼0.14 Bq m −3 , respectively. The equilibrium factor for 222 Rn was estimated to be 0.01∼0.2. The main source of the mysterious spot of high 222 Rn and 220 Rn concentrations was a small but deep channel between the basement of the building and the surrounding soil, and the extremely localized weather condition.

A relation of radon (Rn) daughters concentration in the air to meteorological parameters is investigated. The atmospheric radon daughter concentration and the related meteorological parameters are treated as a simple time series data. The power sprctrum of radon daughter concentration and temperature after fourier transfer are fit to 1/f closely. This fact confirms that the common dynamics exist between the variations of the parameters.