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Your search keyword '"Hwang, M.‐J."' showing total 3 results
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3 results on '"Hwang, M.‐J."'

1. Production of low radioactivity CsI(Tl) crystals for WIMP searches.

Author

Kim, Y. D., Hahn, I. S., Hwang, M. J., Jin, Li, Kang, W. G., Kim, H. J., Kim, S. C., Kim, S. K., Kim, S. Y., Kim, T. Y., Kwak, J. W., Kwon, Y. J., Lee, E. K., Lee, H. S., Lee, J. I., Lee, J. Y., Lee, M. J., Myung, S. S., Park, H., and Schiedt, Alexander

Subjects
CRYSTALS, SOLIDS, RADIOACTIVITY, NUCLEAR reactions, PARTICLES (Nuclear physics), NUCLEAR physics, PHYSICS
Abstract

We have extensively studied the mechanism of the 137Cs and 134Cs contamination in CsI compounds. The nuclei 137Cs and 134Cs in various samples have been studied using a HPGe detector at deep underground. The main source of the 137Cs contamination in CsI powder was desolved 137Cs in the water used in the chemical process of cesium extraction at company side. We also found that 134Cs was produced mainly from 133Cs by neutron capture. We have successfully produced CsI powder containing no more than 2 mBq/kg of 137Cs by using only ultra-pure water for whole extraction process from raw ore(pollucite). © 2005 American Institute of Physics [ABSTRACT FROM AUTHOR]

Published
2005
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2. Development of Low Background CsI(Tl) Crystals and Search for WIMP.

Author

Kim, H. J., Lee, H. S., Bhang, H. C., Choi, J. H., Dao, H., Hahn, I. S., Hwang, M. J., Jung, S. W., Kang, W. G., Kim, D. W., Kim, S. C., Kim, S. K., Kim, T. Y., Kim, Y. D., Kwak, J. W., Kwon, Y. J., Lee, J., Lee, J. H., Lee, J. I., and Lee, M. J.

Subjects
CRYSTALS, IODIDES, CESIUM, POWDERS, PARTICLES (Nuclear physics), POWER resources
Abstract

The response of CsI(Tl) crystals to nuclear recoils and γs down to 3 keV has been studied, and it has been demonstrated that the pulse shape discrimination capability for CsI(Tl) is better than that for NaI(Tl). Extensive study of internal background of CsI powder was performed and a lot of efforts have been made to reduce the internal background sources such as 137Cs and 87Rb. The 137Cs concentration of 2 mBq/kg was achieved successfully in the CsI powder using ultra-pure water for whole extraction process. The Rb concentration was successfully reduced to be less than 1 ppb by the recrystallization method. The CsI(Tl) crystal used for the experiment was grown with the ultra-low background CsI powder and a dimension of the CsI(Tl) crystal is 8 × 8 × 30 cm³ which corresponds to weight of 8.7 kg. The number of photoelectrons is measured to be about 4-6/keV with a RbCs photocathode PMT. The background of CsI(Tl) crystals were measured in the shielding of 30 cm thick mineral oil, 15 cm thick lead, 5 cm thick polyethylene and 10 cm copper at the 700 m minimum depth of underground laboratory at YangYang Pumped Storage Power Plant in Korea. The WIMP search with low background CsI(Tl) crystals has been carried out by the Korean Invisible Mass Search (KIMS) Collaboration and the lower limit on WIMP-nucleon cross section are reported. [ABSTRACT FROM AUTHOR]

Published
2008
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3. Results from KIMS.

Author

Myung, S. S., Bhang, H. C., Choi, J. H., Kim, D. W., Kim, S. C., Kim, S. K., Kwak, J. W., Lee, J., Lee, J. H., Lee, M. J., Lee, S. J., Ryu, S., Kang, W. G., Kim, Y. D., Lee, J. I., Jung, S. W., Kim, H. J., So, J. H., Hahn, I. S., and Hwang, M. J.

Subjects
PHYSICS experiments, PARTICLES (Nuclear physics), NUCLEAR physics, CRYSTALS, PROTONS
Abstract

KIMS is a dark matter search experiment using low background CsI(TB) crystals at Yangyang Underground Laboratory in Korea. With a total exposure of 3409 kg·d data, we set a new limit on WIMP-nucleon cross section. We achieved the most stringent limit on the spin-dependent interaction for a pure proton case. We were able to exclude the DAMA signal region for both spin-dependent and spin-independent interaction for the WIMP mass greater than 20 GeV/c2. KIMS experiment is upgraded with 12 CsI(TB) crystals corresponding to a total mass of 104 kg and accumulating data since Jan. 2008. [ABSTRACT FROM AUTHOR]

Published
2008
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