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The amount of radioactive impurities contaminated in the detector gases is required to be kept at a very low level for rare event particle physics such as dark matter and neutrino observation experiments. Zeolite is a well-known class of materials and is one of the possible candidates for removing impurities from these gases. At the same time, the amount of radioactive impurities released from the adsorbent material needs to be sufficiently small. In this paper, a development of a new ultralow radioactive zeolite as a product of the selection of ultralow radioactive materials is reported. Results on the radon emanation and impurity adsorption from argon gas measurements are also described., Comment: 11 pages, 9 figures

A device for measuring radioactive impurities in gas is developed, consisting of an electrostatic collection type radon detector and an extremely low radioactivity proportional counter. This device measures the radioactive impurities released by materials into the gas and a filtering test for radon removal from gas. The performance of the newly developed proportional counter was evaluated by measuring radon rate. The calibration factor of $^{222}$Rn as 27.4$\pm$0.2~count/day/mBq and the background rate of $^{222}$Rn as 0.84$\pm$0.13~mBq were estimated., Comment: 7 pages, 5 figures