# DEPARTMENT OF NUCLEAR PHYSICS - NUCLEAR ENGINEERING - MEDICAL PHYSICS

Yu Nakazawa, Tai Thanh Chau, Yuki Fuji, Masahiro Ikeno, Satoshi Mihara, Masayoshi Shoji, Tomohisa Uchida, Kazuki Ueno,  Myeong Jae Lee

Proceedings of Science, European Physical Society Conference on High Energy Physics - EPS-HEP2019 - 10-17 July, 2019

Abstract:

The COMET Phase-I experiment searches for a neutrinoless muon-to-electron conversion which has never been observed yet. The world’s highest intensity muon beam is applied, and it leads to an unacceptable trigger rate of O (106 ) Hz. For stable data collection, the trigger rate must be reduced to O(103)Hz. This requirement is met using online event classification in the detector system which holds 99% of signal events. This classification is performed by an FPGA-based trigger system, and its processing time is set to less than 5μs by a buffer size of the detector readout electronics. A prototype board for the trigger system was developed, and communica- tion systems for related electronics devices were also constructed. From test results, the total processing time is estimated to be 2.8 μ s , which meets the requirement. We have also devel- oped an online self-trigger system for cosmic-rays and confirmed the feasibility of this hardware logic. The trigger electronics were installed in a setup for cosmic-ray measurement, and the data acquisition was successfully done using the self-trigger system.

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Bui Ngoc Thien, Vu Ngoc Ba, Nguyen Thi Thao Vy, Truong Thi Hong Loan

Chemosphere Volume 259, November 2020, 127432

Abstract:

In this study, soil-to-plant transfer factor and annual organ equivalent dose due to ingestion of natural radionuclides in 13 popular food crop samples in Ho Chi Minh city, Vietnam were estimated. The obtained data show that the radioactive elements transported from soil to plants play an essential role as indicators for the nutritional needs of plant and the ability to accumulate radioisotopes and heavy metal elements for environmental decontamination. It is found that B. alba and C. gigantean is useful for decontamination of high content potassium in soil, otherwise, P. fruticosa and C. gigantean may be used for soil with high concentration of 210Pb and 226Ra. In addition, biological effects of the plant ingestion in human body were assessed. The doses due to ingestion of food crop samples varied from organ to organ, depending on the organotrophic properties of the radionuclides. For examples, equivalent dose for 40K in large intestine is higher than other organs. In contrast, equivalent dose for 238U, 226Ra, 210Pb and 232Th were mostly at bone surface. In general, the obtained dose values of lower than the average value recommended by UNSCEAR for food crop ingestion pose no threat to the public’s health. However, close investigations are needed in the near future.

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Nguyen Tri Toan Phuc, R. S. Mackintosh, Nguyen Hoang Phuc, and Dao T. Khoa

##### Phys. Rev. C 100, 054615 – Published 18 November 2019

ABSTRACT:

Background: A recent coupled-reaction-channel (CRC) study shows that the enhanced oscillation of the elastic 16O+12C section at backward angles is due mainly to the elastic α transfer or the core exchange. Such a process gives rise to a parity-dependent term in the total elastic S matrix, an indication of the parity dependence of the 16O+12C optical potential (OP).

Purpose: To explicitly determine the core exchange potential (CEP) induced by the symmetric exchange of the two 12C cores in the elastic 16O+12C scattering at Elab=132 and 300 MeV and explore its parity dependence.

Method: S matrix generated by CRC description of the elastic 16O+12C scattering is used as the input for the inversion calculation to obtain the effective local OP that contains both the Wigner and Majorana terms.

Results: The high-precision inversion results show a strong contribution by the complex Majorana term in the total OP of the 16O+12C system and thus provide for the first time a direct estimation of the parity-dependent CEP.

Conclusions: The elastic α transfer or exchange of the two 12C cores in the 16O+12C system gives rise to a complex parity dependence of the total OP. This should be a general feature of the OP for the light heavy-ion systems that contain two identical cores.

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Elastic and Inelastic Alpha Transfer in the 16O+12C Scattering

Nguyen Tri Toan Phuc, Nguyen Hoang Phuc, Dao Tien Khoa

Communication in physics, Vol.31, No 4(2021)

Abstract:

The elastic scattering cross section measured at energies E≲10 MeV/nucleon for some light heavy-ion systems having two identical cores like 16O+12C exhibits an enhanced oscillatory pattern at the backward angles. Such a pattern is known to be due to the transfer of the valence nucleon or cluster between the two identical cores. In particular, the elastic α transfer has been shown to originate directly from the core-exchange symmetry in the elastic 16O+12C scattering. Given the strong transition strength of the $2^+_1$ state of $^{12}$C and its large overlap with the $^{16}$O ground state, it is natural to expect a similar α transfer process (or inelastic α transfer) to take place in the inelastic 16O+12C scattering. The present work provides a realistic coupled channel description of the α transfer in the inelastic 16O+12C scattering at low energies. Based on the results of the 4 coupled reaction-channels calculation, we show a significant contribution of the α transfer to the inelastic 16O+12C scattering cross section at the backward angles. These results suggest that the explicit coupling to the α transfer channels is crucial in the studies of the elastic and inelastic scattering of a nucleus-nucleus system with the core-exchange symmetry.

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Vu Ngoc Ba , Bui Ngoc Thien, Truong Thi Hong Loan

Nuclear Engineering and Technology Available online 2 July 2020

Abstract:

In this work, self-absorption correction factor related to the variation of the composition and the density of soil samples were evaluated using the p-type HPGe detector. The validated MCNP5 simulation model of this detector was used to evaluate its Full Energy Peak Efficiency (FEPE) under the variation of the composition and the density of the analysed samples. The results indicates that FEPE calculation of low gamma ray is affected by the composition and the density of soil samples. The self-absorption correction factors for different gamma-ray energies which was fitted as a function of FEPEs via density and energy and fitting parameters as polynomial function for the logarithm neper of gamma ray energy help to calculate quickly the detection efficiency of detector. Factor Analysis for the influence of the element composition in analysed samples on the FEPE indicates the FEPE distribution changes from non-metal to metal groups when the gamma ray energy increases from 92 keV to 238 keV. At energies above 238 keV, the FEPE primarily depends only on the metal elements and is significantly affected by aluminium and silicon composition in soil samples.

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Effects of agricultural activities on long‐term accumulations of 226Ra and 210Po in topsoil

Van Thang Nguyen, Nguyen Phong Thu Huynh, Huynh Thi Yen Hong, Truong Huu Ngan Thy, Cong Hao Le

Journal of Radioanalytical and Nuclear Chemistry(2022)

Abstract:

In this study, long-term changes in radioactivity levels in the agricultural soil were assessed by a method in which the major processes contributing to the accumulations of radionuclides in the topsoil were taken into account. Four agricultural regions with different crops and agricultural conditions were investigated. The results indicated that long-term cultivation caused the accumulations of 226Ra and 210Po in the topsoil and the rates correlated strongly to plant types, fertilization, and irrigation features. This research is used as the pre-primary base to decide the cultivation method that is relevant to the selection of plant varieties, fertilization and irrigation methods.

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