FACULTY OF PHYSICS & ENGINEERING PHYSICS

DEPARTMENT OF NUCLEAR PHYSICS - NUCLEAR ENGINEERING - MEDICAL PHYSICS

Huynh Nguyen Phong Thu, Nguyen Van Thang, Le Cong Hao

Journal of Environmental Radioactivity 216 (2020) 106189

Abstract:

The effects of moisture content, grain size, temperature, major elemental composition, and the pH of soils on the radon emanation and diffusion coefficients were evaluated in this study. The emanation and diffusion coefficients are strongly influenced by moisture content and grain size. The radon emanation coefficient increased and the diffusion coefficient decreased with decreasing particle size. However, for soils with large particle sizes, the radon emanation and diffusion coefficient remain almost unchanged with variation in grain size. Comparing five different sized soil particles, the emanation coefficient increased and the diffusion coefficient decreased with moisture content. The radon emanation coefficient reached a constant value with different moisture contents depending on the range of grain sizes. The saturation emanation coefficient for less than 0.1, 0.1–0.2, 0.2–0.3, 0.3–0.5, and more than 0.5 mm sized soil grain ranges are 0.47, 0.42, 0.35, 0.26 and 0.23, respectively, with saturation moisture contents of 16%, 14%, 10%, 6% and 4%, respectively. A drastic increase in radon emanation is found at smaller grain sizes with increasing moisture content. Based on the content of major elements and pH of the soils, the multiple regression indicates that the radon emanation coefficient appears to be significantly dependent on iron content and pH. Effective diffusion coefficient values calculated in our study agree with the results calculated by a previous model. Experimental values show that the temperature dependence of the radon diffusion coefficient follows Arrhenius behavior.

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Suppression of the nuclear rainbow in the inelasticnucleus–nucleus scattering

Nguyen Hoang Phuc, Dao T. Khoa, Nguyen Tri Toan Phuc, Do Cong Cuong

Eur. Phys. J. A (2021) 57:75

Abstract:

The nuclear rainbow observed in the elasticα-nucleus and light heavy-ion scattering is proven to be due tothe refraction of the scattering wave by a deep, attractive realoptical potential. The nuclear rainbow pattern, established asa broad oscillation of the Airy minima in the elastic cross sec-tion, originates from an interference of the refracted far-sidescattering amplitudes. It is natural to expect a similar rainbowpattern also in the inelastic scattering of a nucleus–nucleussystem that exhibits a pronounced rainbow pattern in theelastic channel. Although some feature of the nuclear rain-bow in the inelastic nucleus–nucleus scattering was observedin experiment, the measured inelastic cross sections exhibitmuch weaker rainbow pattern, where the Airy oscillationis suppressed and smeared out. To investigate this effect, anovel method of the near-far decomposition of the inelasticscattering amplitude is proposed to explicitly reveal the cou-pled partial-wave contributions to the inelastic cross section.Using the new decomposition method, our coupled channelanalysis of the elastic and inelastic12C+12C and16O+12C scattering at the refractive energies shows unambigu-ously that the suppression of the nuclear rainbow pattern inthe inelastic scattering cross section is caused by a destruc-tive interference of the partial waves of different multipoles.However, the inelastic scattering remains strongly refractivein these cases, where the far-side scattering is dominant atmedium and large angles like that observed in the elasticscattering.

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Nguyễn Duy Thông

Tạp chí Khoa học Trường Đại học Cần Thơ, Tập 56, Số chuyên đề: Khoa học tự nhiên (2020)(1):134-140

Tóm tắt:

Tán xạ nhiều lần được xem là nguyên nhân chính dẫn đến các sai số trong việc xác định vị trí của các hạt tới trong thực nghiệm. Hàm phân bố mật độ xác suất của góc tán xạ nhiều lần đóng vai trò quan trọng trong quá trình làm khớp các số liệu thực nghiệm. Hiện nay, nhiều công trình vẫn đang sử dụng hàm phân bố mật độ xác suất của góc tán xạ nhiều lần tuân theo phân bố Gauss. Điều này dẫn đến các sai số trong quá trình làm khớp. Để xác định hàm phân bố mật độ xác suất của góc tán xạ nhiều lần, trong bài báo này, mô phỏng tương tác của hạt tới để đạt được phân bố của góc tán xạ bằng chương trình g4beamline đã được tiến hành và dựa vào các tính toán  chi2 và hệ số Kullback-Leibler để xác định số hàm Gauss có thể được áp dụng để miêu tả hàm mật độ xác suất.

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Study of nonlocality effects in direct capture reactions with Lagrange-mesh R-matrix method

Nguyen Hoang Phuc, Nguyen Tri Toan Phuc, Do Cong Cuong

International Journal of Modern Physics EVol. 30, No. 09, 2150079 (2021)

Abstract:

We apply the Lagrange-mesh 𝑅-matrix method to calculate the 𝑆-factor for the 13C(𝑝,𝛾)14N and 16O(𝑝,𝛾)17F direct radiative capture reactions. By comparing the astrophysical 𝑆-factors calculated with nonlocal and local potentials, we investigate the nonlocality effects coming from the nuclear potentials in the direct capture reactions. Our calculations are in good agreement with the experimental data and indicate a nonnegligible difference in the results of local and nonlocal potentials. The use of small diffuseness narrow potentials also provides a remarkably good fit in the case with multiple broad resonances. Our findings suggest that the nonlocal potential improves the calculated results although the difference between the local and nonlocal potentials is smaller than uncertainties from other sources. We propose the nonlocality potential should be used in the potential model calculation of future astrophysics rates evaluation.

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Tran ThienThanh, Le Hoang Minh, Nguyen Quoc Bao Cuong, Huynh Dinh Chuong, Nguyen Duy Thong, Vo Hoang Nguyen, Phan Long Ho, Chau Thanh Tai,  Chau Van Tao

NIM A Available online 23 April 2020, 163995

Abstract:

Experimental data of Rayleigh to Compton scattering ratios depending on the effective atomic number of the fifteen powder samples in the range 10 < Z < 30 obtained at an energy of 59.54 keV using six well-known methods are presented in this article. In this study, a Si(Li) detector is placed at a scattering angle of 150 degrees to detect emitting signals from the interaction of incident gamma rays and powder samples. A new fitting procedure with the least squares method was used to fit the Compton peak using a Voigt function and the Rayleigh peak using a Gaussian function by Root software. The ten calibrating samples provided results that were in good agreement with the fitting procedure for all methods using linear functions. The estimated values of the Rayleigh to Compton scattering ratio using the effective atomic numbers were compared to the theoretical calculation. Furthermore, the best solution for the interpolated effective atomic number of the six methods was found and confirmed with the maximum relative deviation lower than 4% for five analysed samples.

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Phan Long Ho, Le Dinh Hung, Vu Tuan Minh, Dang Van Chinh, Tran Thien Thanh & Chau Van Tao

 Scientific Reports Volume 10, Article number: 4299 (2020)

Abstract:

This paper presents information on the gross alpha and gross beta activity concentrations of two hundred twenty-six groundwater samples collected by gas ow proportional counters in southern Vietnam. The gross alpha results in the water samples ranged from 0.024 to 0.748 Bq L1 with a mean of 0.183 ± 0.034 Bq L1, and the gross beta results in the water samples ranged from 0.027–0.632 Bq L1 with a mean of 0.152 ± 0.015 Bq L1. The values obtained in this work were compared with those previously published for various regions or countries. Next, untreated and treated groundwater samples were analyzed to assess their in uences on the treatment process. The results showed that there
were di erences in the minimum detection concentrations and the mean activity values between the untreated and treated groundwater samples (The p-value of the mean comparison tests is signi cant with p < 0.05). In both sample groups, there was a strong positive correlation of the gross alpha versus the gross beta results (r > 0.6). This means that among the radionuclides, the major sources of beta radiation are uranium and thorium decay series radionuclides. Finally, the annual e ective dose for adults (>17 years) was calculated based on the assumption that major radionuclides have the highest e ective dose conversion factors. In general, the results for Pb-210, Ra-226, and Ra-228 were observed to be lower than the recommended reference values established by the World Health organization and the International Atomic Energy Agency, except for the value of Po-210.

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