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Dark matter is an unknown type of matter present in the universe that could be of particle origin. One of the most complete theoretical frameworks that includes a dark matter candidate is supersymmetry. Many supersymmetric models predict the existence of a new stable, invisible particle called the lightest supersymmetric particle (LSP), which has the right properties to be a dark matter particle. 

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Dù đóng vai trò quan trọng trong giải quyết những vấn đề toàn cầu như cung cấp năng lượng sạch, giảm phát thải, hướng tới phát triển xanh và bền vững nhưng trong thực tế, năng lượng nguyên tử lại phải hứng chịu nhiều hiểu nhầm với thông tin bị thổi phồng hoặc bóp méo. Đây chính là thông điệp mà nhà vận động môi trường Mỹ Michael Shellenberger chia sẻ trong phần diễn thuyết kết thúc Diễn đàn ATOMEXPO tại Sochi, Nga, từ ngày 15-16/04/2019.

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The Higgs boson was discovered in 2012 by the ATLAS and CMS Experiments at CERN, but its coupling to other particles remains a puzzle.

Fortunately, the LHC provides many windows into measuring Higgs boson couplings. There are four main ways to produce the Higgs boson: through the fusion of two gluon particles (gluon-fusion, or ggF), through the fusion of weak vector bosons (VBF), or in association with a W or Z boson (VH), or one or more top quarks (ttH+tH). There are also five main channels in which Higgs bosons can decay: into pairs of photons, W or Z bosons, tau leptons or b quarks. Each of these processes brings unique insights into the Higgs boson properties.

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 Validation of gamma scanning method for optimizing NaI(Tl) detector model in Monte Carlo simulation

Huynh Dinh Chuong, Nguyen Quoc Hung, Nguyen Thi My Le,  Vo Hoang Nguyen, Tran Thien Thanh

Abtract:

The aim of this study is the validation of gamma scanning method for optimizing NaI(Tl) detector model in Monte Carlo simulation. The experimental procedure involved: scanning on front and lateral surfaces of the detector with collimated low-energy photon beam; calibrating the efficiency with energies between 31-1408 keV for point sources at distances of 0 cm and 30 cm from source to the detector. The Monte Carlo code used for the simulations was MCNP6. The diameter and the length of crystal were determined according to the measured results of gamma scanning with a collimated 241Am radioactive source. The distance from window to crystal was estimated using transmission measurement recorded on a second detector. The density of reflector was adjusted to obtain the match between measured and simulated values of efficiency ratio of 81 and 31 keV from a 133Ba radioactive source. The optimized model was applied in Monte Carlo simulations to determine the efficiency and energy spectrum response function of NaI(Tl) detector for point source measurements in two configurations. Good agreement was obtained between measured and simulated results.

 

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Bằng chứng thực nghiệm trực tiếp chứng minh tính hai-lần số “Magic” của 78Ni đã được công bố trên tạp chí Nature ngày 2/5/2019...

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 Natural radioactivity and radon emanation coefficient in the soil of Ninh Son region, Vietnam

Huynh Nguyen Phong Thu,  Nguyen VanThang, Truong Thi Hong Loan, Nguyen Van Dong,  Le Cong Hao

Abstract

The natural radioactivity (238U, 226Ra, 232Th and 40K) and radon emanation coefficient for 57 soil samples belonging to alluvial, red, forest surface, slip-debris, metamorphic and sandy soil of the Ninh Son region in Ninh Thuan province have been determined. The soil gas radon was measured by in-situ with RAD7 radon monitor coupled with a soil gas probe while activity concentrations of 238U, 226Ra, 232Th, and 40K were measured by an HPGe gamma-ray spectrometry system. The 226Ra/238U disequilibrium occurred in the soil samples and a great majority of the 226Ra/238U values lie above 1. Average activity concentrations of 226Ra, 232Th, and 40K are significantly higher than the worldwide average concentrations in soils published by UNSCEAR, 2008. The gamma dose rate ranged from 55 ± 2 to 248 ± 7 nGy h−1 with an average of 130 ± 4 nGy h−1 which is greater than the world value. Strong positive correlations were recorded between 238U and 226Ra, 232Th and 226Ra, 232Th and 238U, and 226Ra and 222Rn. The results of weathering and alteration processes were proposed to be dominated reasons for the 226Ra/238U disequilibrium occurred in the soil samples. Most of the radon in soil gas samples are considered “normal risk” or low radon index. The mean values of the emanation coefficient for alluvial, red, forest surface, slip-debris, metamorphic and sandy soil were found to be 0.51 ± 0.03, 0.40 ± 0.02, 0.36 ± 0.02, 0.30 ± 0.02, 0.26 ± 0.02 and 0.15 ± 0.01, respectively. Radon emanation was found to be an inverse function of grain size for grain sizes larger than 0.1 mm in diameter and independent on the radium content of the soil sample.

 

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