Vol.30,

Radiation for targeting liver tumors can be challenging because of the damage that it can cause to sensitive organs such as heart and kidney. To calculate the dose received by non-involved organs, a modelling of the patient’s entire body is necessary. Therefore, in this study, a human Oak Ridge National Laboratory-Medical Internal Radiation Dose (ORNL-MIRD) phantom was used for liver proton therapy simulation. The results show that the optimum proton energy interval covering the whole tumor was in the range of 90 MeV–120 MeV. A spread-out Bragg peak was built by adding Bragg peaks to cover the liver tumor volume and beam parameters recommended by the International Commission on Radiation Units and Measurements (ICRU) were evaluated. The flux of secondary particles was calculated on the surface of the tumor and two-dimensional dose distributions for protons, neutrons, and photons were shown. Finally, the total doses of protons, photons, and neutrons in tumor and 14 non-involved organs were calculated. The results indicated that the ratio of received dose to the normal tissue of the liver concerning the spherical tumor of 2 cm in radius was approximately 0.01. This ratio for organs such as gall bladder, heart, and kidney were approximately 8.4 ×10 ^-5, 5.1 ×10 ^-5, and 2.34 ×10 ^-5. Secondary particles such as neutrons and photons deposit their energies to organs located far from the treatment volume; thus, increasing the risk of secondary cancers. The research results indicated that the secondary particles dose was quite small in liver proton therapy. All the calculations were performed using Monte Carlo N-Particle Transport Code (MCNP).

337

Radio frequency (RF) transmission systems with high precision phase stability are required by the next generation of particle colliders and light sources. An RF transmission system was designed to meet this requirement. In this system, RF signal generated at the sending end is modulated onto a continuous wave (CW) optical carrier, transmitted through an optical fiber and demodulated at the receiving end. The phase drift is detected by a digital phase monitor with femtosecond-level accuracy and compensated by a Motorized Optical Fiber Delay Line (ODL). The measurement results show that the long term phase drifts can be stabilized to within 100 fs (pk-pk), 500 fs (pk-pk), and 1.8 ps (pk-pk) in a 400-meter long optical fiber over 1 hour, 24 hours, and 10 days respectively.

360

A helium cryogenic system is designed by the Institute of Modern Physics, Chinese Academy of Sciences, to supply different cooling powers to the cryomodules of ion-Linac (iLinac) accelerator, which serves as the injector of the High Intensity Heavy Ion Accelerator Facility project. The iLinac is a superconducting heavy ion accelerator approximately 100 m long and contains 13 cryomodules cooled by superfluid helium. This article describes the cryogenic system design of the iLinac accelerator. The requirements of the cryogenic system, such as cooling mode, refrigeration temperature, operating pressure, and pressure stability, are introduced and described in detail. In addition, heat loads from different sources are analyzed and calculated quantitatively. An equivalent cooling capacity of 10 kW at 4.5 K was determined for the cryogenic system according to the total heat load. Furthermore, a system process design was conducted and analyzed in detail. Further, the system layout and the main equipment are presented.

459

The transverse emittance of the extracted beam from the Heavy Ion Medical Machine cyclotron is measured and then optimized for injection into the synchrotron. For the purposes of cross validation, three methods, i.e., slit-grid, Q-scan, and 3-grid, are used to measure the emittance. In the slit-grid technique, an automatic selection of the region of interest is adopted to isolate the major noise from the beam phase space, which is an improvement over the traditional technique. After iterating over the contour level, an unbiased measurement of the emittance can be obtained. An improvement of the thin lens technique is implemented in the Q-scan method. The results of these measurements are presented.

469

Scheduled maintenance and condition-based online monitoring are among the focal points of recent research to enhance nuclear plant safety. One of the most effective ways to monitor plant conditions is by implementing a full-scope, plant-wide fault diagnostic system. However, most of the proposed diagnostic techniques are perceived as unreliable by operators because they lack an explanation module, their implementation is complex, and their decision/inference path is unclear. Graphical formalism has been considered for fault diagnosis because of its clear decision and inference modules, and its ability to display the complex causal relationships between plant variables and reveal the propagation path used for fault localization in complex systems. However, in a graph-based approach, decision-making is slow because of rule explosion. In this paper, we present an enhanced signed directed graph that utilizes qualitative trend evaluation and a granular computing algorithm to improve the decision speed and increase the resolution of the graphical method. We integrate the attribute reduction capability of granular computing with the causal/fault propagation reasoning capability of the signed directed graph and comprehensive rules in a decision table to diagnose faults in a nuclear power plant. Qualitative trend analysis is used to solve the problems of fault diagnostic threshold selection and signed directed graph node state determination. The similarity reasoning and detection ability of the granular computing algorithm ensure a compact decision table and improve the decision result. The performance of the proposed enhanced system was evaluated on selected faults of the Chinese Fuqing 2 nuclear reactor. The proposed method offers improved diagnostic speed and efficient data processing. In addition, the result shows a considerable reduction in false positives, indicating that the method provides a reliable diagnostic system to support further intervention by operators.

380

This work presents the results of computer simulation of neutronic processes in a high-temperature gas-cooled thorium reactor for 30 different options of core loading. To guarantee stable and long-term reactor operation (7–10 years), the quantity of fuel compact dispersion phase and starting fuel composition was selected. It is demonstrated that it is possible in principle to substitute the near-axial recirculation zone of the reactor core by a long magnetic trap with a high-temperature plasma column for generating thermonuclear neutrons. The distribution of neutron yield along the length of the plasma source is also presented. Such a thorium reactor, with a near-axial source of extra neutrons, can be applied for researching thermophysical and neutronic characteristics of dispersion thorium fuel to improve its properties. The results of the work are of great interest from the perspective of future advancement of the thermonuclear power industry, by means of creation of a hybrid installation based on a thorium reactor with a long plasma column as a source of additional neutrons.

363

Bubble formation is an integral part of the two-phase flow science. Through numerical simulation and experiments using different air flowrates and orifice diameters, the present study aims at investigating the behavior of bubble formation and evolution from vertical wall orifice in quiescent pure water. For the experiments, the images of the bubble formation process under different working conditions were recorded using a high-speed camera, and analyzed the entire process. The bubble formation process can be divided into three stages, namely nucleation, stable growth, and necking. According to the obtained results, bubble forms only when the air phase pressure exceeds the threshold pressure at wall orifice. Due to the influence of the threshold pressure and buoyancy, the bubble volume decreases with an increase in the wall orifice diameter for the same flow rate. Moreover, the volume of fluid method is applied to simulate bubble formation in a three-dimensional model and the "buffer volume" is considered in the simulation model. The simulation results matched well with the experimental data, which proves the existence of threshold pressure and the periodic pressure fluctuation at the wall orifice.

377

A real-time double-ring neutron time-of-flight (TOFII) spectrometer system has been proposed to achieve plasma diagnosis on HL-2M Tokamak with a relatively high-count rate and sufficient energy resolution. The TOFII system is in its development stage, and this work describes its characteristics in terms of design principle, system structure, electronic system design, preliminary tests, and neutron transport simulation. The preliminary test results illustrate that the TOFII system can demonstrate the real-time dynamic spectrum every 10 ms. The results also show that based on the support vector machine (SVM) method, the n-γ discrimination algorithm achieves the discrimination accuracy of 99.1% with a figure of merit (FOM) of 1.30, and the intrinsic timing resolution of the system is within 0.3%. The simulated flight time spectrums from 1 to 5 MeV are obtained through the Monte Carlo tool Geant4, which also provide the reasonable results. The TOFII system will then be calibrated on mono-energetic neutron sources for further verification.

526

Using photons in therapeutic and diagnostic medicine requires accurate computation of their attenuation coefficients in human tissues. The buildup factor, a multiplicative coefficient quantifying the ratio of scattered to primary photons, measures the degree of violation of the Beer–Lambert law. In this study, the gamma-ray isotropic point source buildup factors, specifically, the energy absorption buildup factor (EABF) and exposure buildup factor, are estimated. The computational methods used include the geometric progression fitting method and simulation using the Geant4 (version 10.4) Monte Carlo simulation toolkit. The buildup factors of 30 human tissues were evaluated in an energy range of 0.015–15 MeV for penetration depths up to 100 mean free paths (mfp). At all penetration depths, it was observed that the EABF seems to be independent of the mfp at a photon energy of 1.5 MeV and also independent of the equivalent atomic number (Z_eq) in the photon energy range of 1.5–15 MeV. However, the buildup factors were inversely proportional to Z_eq for energies below 1.5 MeV. Moreover, the Geant4 simulations of the EABF of water were in agreement with the available standard data (the deviations were less than 5%). The buildup factors evaluated in the present study could be useful for controlling human exposure to radiation.

496

In this study, we investigated the motion, shape, and delayed radiation intensity of a radioactive cloud by establishing a volume-source model of delayed radiation after high-altitude nuclear explosions. Then, the spatial distribution of electron number density at different moments on the north side of the explosion point generated by delayed γ rays and delayed β rays from the radioactive cloud under the influence of the geomagnetic field were calculated by solving chemical reaction kinetics equations. The impact of radio communication in the different frequency bands on the process of atmospheric ionization was also studied. The numerical results of the high-altitude nuclear explosion (120-km high and with a 1 megaton equivalent at 40°N latitude) indicated that the peak of electron number density ionized delayed γ rays is located at a height of approximately 100 km and that of electron number density ionized delayed β rays is about 90-km high. After 1 min of explosion, the radio communication in the medium frequency (MF) and high-frequency (HF) bands was completely interrupted, and the energy attenuation of the radio wave in the very high-frequency (VHF) band was extremely high. Five minutes later, the VHF radio communication was basically restored, but the energy attenuation in the HF band was still high. After 30 min, the VHF radio communication returned to normal, but its influence on the HF and MF radio communication continued.

355

The neutron yield in the ¹²C(d,n)¹³N reaction and the proton yield in the ¹²C(d,p)¹³C reaction have been measured using deuteron beams of energies 0.6–-3 MeV. The deuteron beam is delivered from a 4 MeV electrostatic accelerator and bombarded on a thick carbon target. The neutrons are detected at 0°, 24°, and 48° and the protons at 135° in the lab frame. Further, the ratio of the neutron yield to the proton yield was calculated. This can be used to effectively recognize the resonances. The resonances are found at 1.4 MeV, 1.7 MeV, and 2.5 MeV in the ¹²C(d,p)¹³C reaction, and at 1.6 MeV and 2.7 MeV in the ¹²C(d,n)¹³N reaction. The proposed method provides a way to reduce systematic uncertainty and helps confirm more resonances in compound nuclei.

420

The dynamic evolution of the charm hadron in hot quark matter was studied in the framework of a multiphase transport (AMPT) model. We first reproduced the open charm hadron D₀ p_T spectrum in Au + Au collisions at sNN = 200 GeV by triggering the cc¯ production in AMPT, and then the elliptic flow of charm hadrons was described with different parton cascade cross sections. Charm hadron azimuthal angular correlations were proposed, and they are affected by the different parton cross section parameter applied in the model, which can facilitate our understanding of the loss of collision energy of charm quarks in hot quark medium and can stimulate further experimental studies.

405

The emission angle distribution of projectile fragments (PFs) and the temperature of PF emission sources for fragmentation of ⁵⁶Fe on polyethylene, carbon, and aluminum targets at the highest energy of 497 A MeV are investigated on the basis of corrected data, using a CR-39 plastic nuclear track detector. It is found that the average emission angle of PFs increases with the decrease of PF charge for the same target, and no obvious dependence of angular distribution on the mass of the target nucleus is found for the same PF. The cumulative squared transverse momentum distribution of PFs can be well represented by a single Rayleigh distribution. The temperature of PF emission sources is extracted from the distribution, it is about 1.0∼8.0 MeV and does not depend on the mass of the target for PFs with charges of 9≤Z≤25.

336

There are two infrared beamlines at the Shanghai Synchrotron Radiation Facility (SSRF)—BL01B and BL06B. BL01B was the first infrared beamline of the National Facility for Protein Science in Shanghai (NFPS) at SSRF, which is dedicated to synchrotron infrared microspectroscopy. It utilizes bending magnet radiation (BMR) and edge radiation (ER) as light sources. Diffraction-limited spatial resolution is reached in the infrared microspectroscopy experiment. BL01B has been in operation for approximately five years since it opened in January 2015. In the past few years, many meaningful results have been published by user groups from various disciplines, such as biomacromolecule materials and pharmaceutical, environmental, and biomedical sciences. In addition, a new infrared beamline station BL06B is under construction, which is optimized for the mid-infrared and far-infrared band. BL06B is equipped with a vacuum-type Fourier transform infrared spectrometer, infrared microscope, custom long-working-distance infrared microscope, infrared scanning near-field optical microscope, and mid-infrared Mueller ellipsometer. The purpose is to serve experiments with high vacuum requirements and spatial resolution experiments, as well as those that are in situ and time-sensitive, such as high-pressure and atomic force microscopy infrared experiments. The station can be used for research in biomaterials, pharmacy, geophysics, nanotechnology, and semiconductor materials.

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