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BỘ MÔN VẬT LÝ HẠT NHÂN - NGÀNH KỸ THUẬT HẠT NHÂN - NGÀNH VẬT LÝ Y KHOA

Vu Ngoc Ba,  Le Thi Ha Giang, Bui Ngoc Thien, Truong Thi Hong Loan, Ngo Quang Huy

Applied Radiation and Isotopes 163 (2020) 109229

Abstract:

In this work, the physical dimensions and the actual position of germanium crystal within a detector housing, the homogeneity of the crystal surface and outer dead layer thickness for a p-type HPGe detector were con rmed by the scan method using the collimated low energy photon beams combined with Monte Carlo simulation. The length and the diameter of the crystal were found to match with the values supplied by the manufacturer in discrepancy of about 3%. Only one mounting strap (Typical) for holding the crystal inside the mounting cup instead of two which is indicated in the detector drawing supplied by manufacturer was revealed by scanning along the lateral face of detector. Scanning on the front surface and around the lateral face of detector by the collimated 59.5 keV photon beam veri ed the outer dead layer thicknesses at the front surface and lateral face of the crystal averagely increases about 6.5% and 12% respectively. Adjusting the detector parameters for MCNP simulation by these veri ed values, the simulated peak ef ciencies for different photon energies become being in accordance with the experimental peak ef ciencies.

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Nguyen Tri Toan Phuc, Kazuki Yoshida, Kazuyuki Ogatta,

Phys.Rev. C100,064604 - Published 6 December 2019

ABSTRACT:

Background: Proton-induced nucleon knockout (p,pN) reactions have been successfully used to study the single-particle nature of stable nuclei in normal kinematics with the distorted-wave impulse approximation (DWIA) framework. Recently, these reactions have been applied to rare-isotope beams at intermediate energies in inverse kinematics to study the quenching of spectroscopic factors.

Purpose: Our goal is to investigate the effects of various corrections and uncertainties within the standard DWIA formalism on the (p, pN) cross sections. The consistency of the extracted reduction factors between DWIA and other methods is also evaluated.
Method: We analyze the ( p, 2 p) and ( p, pn) reaction data measured at the R3 B-LAND setup at GSI for carbon, nitrogen, and oxygen isotopes in the incident energy range of 300–450 MeV/u. Cross sections and reduction factors are calculated by using the DWIA method. The transverse momentum distribution of the 12C(p,2p)11B reaction is also investigated.

Results: We have found that including the nonlocality corrections and the Møller factor affects the cross sections considerably. The proton-neutron asymmetry dependence of reduction factors extracted by the DWIA calculation is very weak and consistent with those given by other reaction methods and ab initio structure calculations.

Conclusions: The results found in this work provide a detailed investigation of the DWIA method for ( p, pN ) reactions at intermediate energies. They also suggest that some higher-order effects, which is essential for an accurate cross-section description at large recoil momentum, is missing in the current DWIA and other reaction models.

DOI: 10.1103/PhysRevC.100.064604

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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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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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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