Vol.29,

Heavy ion induced single event upsets (SEUs) of static random access memory (SRAM), integrated with three-dimensional integrated circuit (3DIC) technology, are evaluated using a Monte Carlo simulation method based on the Geant4 simulation toolkit. The SEU cross-sections and multiple cell upset (MCU) susceptibility of 3D SRAM are explored using different types and energies of heavy ions. In the simulations, the sensitivities of different dies of 3D SRAM show noticeable discrepancies for low linear energy transfers (LETs). The average percentage of MCUs of 3D SRAM increase from 17.2 to 32.95%, followed by the energy of ²⁰⁹Bi decreasing from 71.77 to 38.28 MeV/u. For a specific LET, the percentage of MCUs presents a notable difference between the face-to-face and back-to-face structures. In the back-to-face structure, the percentage of MCUs increases with a deeper die, compared with the face-to-face structure. The simulation method and process are verified by comparing the SEU cross-sections of planar SRAM with experimental data. The upset cross-sections of the planar process and 3D integrated SRAM are analyzed. The results demonstrate that the 3D SRAM sensitivity is not greater than that of the planar SRAM. The 3D process technology has the potential to be applied to the aerospace and military fields.

764

Since the room-temperature detector CdZnTe (CZT) has advantages in terms of detection efficiency, energy resolution, and size, it has been extensively used to detect X-rays and gamma-rays. So far, nuclear radiation detectors such as cerium chloride doped with lanthanum bromide (LaBr₃ (Ce)), thallium doped with cesium iodide (CsI (Tl)), thallium doped with sodium iodide (NaI (Tl)), and high-purity germanium (HPGe) primarily use the spectroscopy - dose rate function (G (E)) to achieve the accurate measurement of air kerma rate (K˙a) and ambient dose equivalent rate (H˙*(10)). However, the spectroscopy-dose rate function has been rarely measured for a CZT detector. In this study, we performed spectrum measurement using a hemispherical CZT detector in a radiation protection standards laboratory. The spectroscopy - dose rate function G(E) of the CZT detector was calculated using the least-squares method combined with the standard dose rate at the measurement position. The results showed that the hemispherical CZT detector could complete the measurement of air kerma rate (K˙a) and ambient dose equivalent rate (H˙*(10)) by using the G (E) function at energies between 48 keV and 1.25 MeV, and the relative intrinsic errors were, respectively, controlled within ± 2. 3% and ± 2. 1%.

665

Inspired by total variation (TV), this paper represents a new iterative algorithm based on diagonal total variation (DTV) to address the computed tomography (CT) image reconstruction problem. To improve the quality of a reconstructed image, we used DTV to sparsely represent images when iterative convergence of the reconstructed algorithm with TV-constraint had no effect during the reconstruction process. To investigate our proposed algorithm, the numerical and experimental studies were performed, and root mean square error (RMSE) and structure similarity (SSIM) were used to evaluate the reconstructed image quality. The results demonstrated that the proposed method could effectively reduce noise, suppress artifacts, and reconstruct high-quality image from incomplete projection data.

785

Large accelerator facilities require clocks and triggers with high accuracy to synchronize equipment and devices. A new femtosecond timing system was designed to meet the demands of new facilities. In this system, the radio-frequency signal is modulated in a continuous-wave laser carrier with frequency stabilization, and timing events are distributed in the same fiber. The phase drift is detected precisely, based on the principle of the Michelson interferometer. The phase drift is compensated with coarse and fine correctors afterward. We aim to realize the stable transmission of the RF signal and timing events for a long distance and duration, with the phase drift and additive jitter in femtoseconds. After the extension, the system will become a complete solution for the clock-and-trigger distribution of synchrotron radiation facilities, free electron lasers, and other accelerators. The physics design, simulation analysis, and preliminary results are included in the paper.

756

Safety systems, built on state of the art technology, are essential for achieving acceptable levels of plant safety to minimize hazards to the reactor and the general public. The Second Shutdown System (SSS) as an engineered safety feature and a part of the Reactor Protection System (RPS) is a means for rapidly shutting down a nuclear reactor, keeping it in a subcritical state and serving as a backup to the First Shutdown System (FSS). In this research, one SSS with two types of optimum chamber designs are proposed, that take into account the main current characteristic features of the Tehran research reactor with improvements over earlier designs. They are based on a liquid neutron absorber injection that is preferably different, diverse, and independent from the FSS based on the rod drop mechanism. The major design characteristics of this SSS with two different chambers were investigated using MCNPX 2.6.0 code. The performed calculations showed that the designed SSS is a reliable shutdown system, assuring an appropriate shutdown margin and injection time, with no significant effects on the effective delayed neutron fraction while causing minimal variations to the core structure. Further, the reasonable financial cost and the prolongation of the operation cycle are additional advantages of this design.

1048

Fuel reload pattern optimization is essential for attaining maximum fuel burnup for minimization of generation cost while minimizing power peaking factor (PPF). The aim of this work is to carryout detailed assessment of Particle Swarm Optimization (PSO) in the context of fuel reload pattern search. With astronomically large number of possible loading patterns, the main constraints are limiting local power peaking factor, fixed number of assemblies, fixed fuel enrichment, and burnable poison rods. In this work, initial loading pattern of fixed batches of fuel assemblies is optimized by using Particle Swarm Optimization technique employing novel feature of varying inertial weights with the objective function to obtain both flat power profile and cycle keff >1. For neutronics calculation, PSU-LEOPARD generated assembly depletion dependent group constants based ADD-files are used. The assembly data description file generated by PSU-LEOPARD is used as input cross-section library to MCRAC code, which computes normalized power profile of all fuel assemblies of PWR nuclear reactor core. The standard PSO with varying inertial weights is then employed to avoid trapping in local minima. A series of experiments have been conducted to obtain near optimal converged fuel loading pattern of 300MWe PWR Chashma reactor. The optimized loading pattern is found in good agreement with results found in literature. Hybrid scheme of PSO with Simulated Annealing has also been implemented and resulted in faster convergence.

1015

A variety of formulations was investigated for the fabrication of an appropriate shielding rubber to be used in neutron–gamma mixed fields. Having considered the required mechanical properties together with tungsten as the gamma-ray absorbing element, calculations with MCNPX 2.6 code confirmed that the incorporation of 5 weight percentage (wt.%) of boron carbide exhibited the best performance as a thermal neutron absorber. A series of both experimental and simulation results are provided for comparison.

675

Diffusion length calculations of neutrons are performed using the Chebyshev polynomials of the second kind. The neutrons are assumed to move with constant energy in a uniform homogeneous slab. An alternative scattering kernel called an Anlı-Güngör (AG) phase function and a traditional Henyey-Greenstein (HG) phase function are used for the scattering function in the stationary neutron transport equation. First, analytic expressions and then numerical results are obtained for the diffusion length for various values of the scattering and cross-section parameters. Numerical results obtained from both scattering kernels for the diffusion length of the neutrons are given in tables side by side for comparison. The applicability of the method is easily demonstrated by these results.

904

Systematic total Routhian surface calculations for even-even N=104 midshell isotones with 66 ≤ Z ≤ 82 have been carried out based on a more realistic diffuse-surface deformed Woods-Saxon nuclear potential in (β₂, γ, β₄) deformation space, focusing on the rotation-induced shape-coexisting phenomena. As an example and basic test, the oblate property at the ground state in ¹⁸⁴Hg is well reproduced and the microscopic origin is analyzed from the single-particle structure. The present calculated results are compared with available experimental information, showing a good agreement. It is systematically found that in this isotonic chain several bands with different shapes (e.g., prolate, oblate, and superdeformed prolate bands, even non-collective band) may show a strong competition and coexisting phenomenon at a certain domain of the rotational frequency.

707

Erbium nuclei have been bombarded with neutrons which were received by a using clinical electron linear accelerator to perform photonuclear reactions. In this experiment, the possibility of the neutron capture process has been observed because of emitted neutrons appearing in the experimental area. In particular, neutron capture of ¹⁷⁰Er nucleus has been observed. After the neutron capture of ¹⁷⁰Er nucleus, the unstable ¹⁷¹Er has been formed and decayed into the ¹⁷¹Tm. By using this reaction path, some transition energies of ¹⁷¹Tm obtained from the residual activity measurements and the half-life of ¹⁷¹Er have been determined, and they are in agreement with adopted values in literature.

857

Recent progress of the quantum molecular dynamics model for describing the dynamics of heavy-ion collisions is viewed, in particular the nuclear fragmentation, isospin physics, particle production and in-medium effect, hadron-induced nuclear reactions, hypernucleus etc. The neck fragmentation in Fermi-energy heavy-ion collisions is investigated for extracting the symmetry energy at subsaturation densities. The isospin effects, in-medium properties, and the behavior of high-density symmetry energy in medium and high energy heavy-ion collisions are thoroughly discussed. The hypernuclide dynamics formed in heavy-ion collisions and in hadron induced reactions is analyzed and addressed in the future experiments at the High-Intensity heavy-ion Accelerator Facility (HIAF).

599

A prototype thick-GEM-based CEE (Cooling Storage Ring External-target Experiment) time projection chamber (TPC) is constructed and tested with the pulsed ultraviolet laser beams. The results indicate that the prototype TPC has a good performance in three-dimensional track resolution. In X direction the position resolution is about 0.2 mm, and in Y direction the position resolution is about 0.5 mm. The results also determine that the energy resolution is about 5.4%, which achieve the requirements of the CEE experiment and can be used to study the nuclear state equation and the Quantum Chromo Dynamics.

640

A 53.667 MHz CW (continuous-wave) heavy ion IH-DTL has been designed for the SSC-LINAC injector of HIRFL-CSR (Heavy Ions Research Facility at Lanzhou-Cooling Storage Ring). It accelerates ions with maximum mass to charge ratio of 7.0 from 143 keV/u to 295 keV/u. Low power RF measurement of the IH-DTL1 has been carried out to investigate the RF performance and the quality of the electric field distribution on the beam axis. The measured Q₀ value and the shunt impedance are 10400 and 198 MΩ/m, respectively. The electric field distributions on and around the beam axis were evaluated and compared with the design value. By a new approach, the dipole field component is also estimated. The beam dynamics simulation using measured field distribution was presented in this paper. Based on the dynamics analysis both in transverse and longitudinal phase space, the field distribution can meet the design requirement. Finally, the RF conditioning and very first beam commissioning on the IH-DTL1 were finished. The beam test results agree well with the simulation results, what’s more, the property of the variable output beam energy about the separated functions DTL was verified.

1016

Conventional X-ray tube based cone-beam computed tomography (CX-CBCT) systems have great potential in industrial applications. Such systems can rapidly obtain a three-dimensional (3D) image of an object. Conventional X-ray tubes fulfill the requirements for industrial applications, because of their high tube voltage and power. Continuous improvements have been made to CX-CBCT systems, such as imaging time shortening, acquisition strategy optimization, and imaging software development, etc. In this study, a CX-CBCT system is developed. Additionally, some improvements to the CX-CBCT system are proposed based on the hardware conditions of the X-ray tube and detector. A near detector (ND) geometry condition is employed to obtain a sharper image and larger detection area. An improved acquisition strategy is proposed to simplify operations and reduce total imaging time. In the ND geometry condition, a simplified method called FBP slice stacking (SS-FBP) is proposed, which can be applied to 3D image reconstruction. SS-FBP is time-saving relative to traditional methods. Furthermore, imaging software for the CX-CBCT system is developed in the MATLAB environment. Several imaging experiments were performed. The results suggest that the CX-CBCT system works properly, and that the above improvements are feasible and practical.

1006

The boron content of uranium fuel samples with boron concentrations in the range of 0.05-10 µg/g was determined using inductively coupled plasma optical emission spectrometry (ICP-OES) after the uranium was separated by cation-exchange. The samples were dissolved in 3 M HNO₃ on a hot plate at 150 ℃ and evaporated to near dryness. The residues were redissolved in 0.2 M HNO₃, and passed through a column loaded with Dowex 50WX8-400 resin. Uranium was adsorbed on the resin, while boron was easily eluted with 0.2 M HNO₃. The boron content of the effluent was determined using ICP-OES. Several strategies were employed to improve the reliability of the experimentally determined boron content. The addition of mannitol and proper control of the evaporation process were shown to be effective in preventing boron loss during sample dissolution and evaporation. The memory effect was eliminated by flushing the system with 1.5% ammonia for 30 s between successive sample runs, and the matrix match method was used to eliminate the matrix effect arising from mannitol during the ICP-OES analysis. The accuracy of the results of the analysis was determined by addition recovery tests and by comparison with the results of three Chinese certiﬁed reference materials (GBW04242, GBW04243, GBW04232). Using the method we developed, the limit of detection for boron was as low as 0.05 µg/g in uranium fuel samples, and the relative standard deviations for 0.1-0.5 g uranium samples with 0.05-2 µg/g of boron were within 9%.

858