Vol.31,

As one of the most critical types of cancer, hepatocellular carcinoma (HCC) affects many people worldwide. This study demonstrated the prospective use of atorvastatin, a drug that inhibits the mevalonate pathway, causing hypolipidemia, as a carrier to deliver the iodine-131 (¹³¹I) isotope to liver tissues for HCC radiotherapy. The atorvastatin radioiodination method was optimized for utilizing the ¹³¹I isotope. The radiochemical quality and the in vitro stability of the generated [¹³¹I]atorvastatin were investigated. In addition, the biodistribution experiments of [¹³¹I]atorvastatin were evaluated in both normal and HCC-induced rat models. [¹³¹I]atorvastatin was produced at a maximum radiochemical yield of 86.7 ± 0.49%. The [¹³¹I]atorvastatin solution purified via high-performance liquid chromatography showed good in vitro stability for 12 h after tagging. Biodistribution analyses revealed remarkable liver targeting capacity of [¹³¹I]atorvastatin and good localization of ¹³¹I in liver tissues. Overall, the encouraging biochemical profile and histopathological findings have been reported, and preliminary investigations on the possible use of [¹³¹I]atorvastatin as a radiotracer and its impact on HCC radiotherapy in rats show promise.

481

The health effects of ambient PM2.5 and its potential mechanisms have generated considerable interest. In vitro cell studies and ex vivo animal experiments may not accurately determine the characteristics of PM2.5 particles. To better understand their detailed mechanisms, we performed an in vivo study using single photon emission tomography (SPECT) imaging. To mimic the PM 2.5 particles, SiO₂ nanoparticles modified by ethylene carbonate or polyvinyl pyrrolidone were labeled with ¹³¹I. After administration via inhalation, in vivo SPECT imaging of the radiolabeled particles in Sprague Dawley rats was performed. It was found that radioactivity accumulated in the lungs and trachea 6 and 24 h after administration. In addition, significant radioactivity was observed in the abdomen, including the liver and kidneys. The results were also confirmed by ex vivo autoradiography. This study revealed that in vivo SPECT imaging could be an effective method for investigating the properties of PM 2.5 particles.

364

This study presents the RF design of a linear accelerator (linac) operated in single-bunch mode. The accelerator is powered by a compressed RF pulse produced from a SLED-I type RF pulse compressor. The compressed RF pulse has an unflattened shape with a gradient distribution which varies over the structure cells. An analytical study to optimize the accelerating structure together with the RF pulse compressor is performed. The optimization aims to maximize the efficiency by minimizing the required RF power from the generator for a given average accelerating gradient. The study shows that, owing to the compressed RF pulse shape, the constant-impedance structure has a similar efficiency to the optimal structure using varying iris apertures. The constant-impedance structure is easily fabricated and is favorable for the design of a linac with a pulse compressor. We utilize these findings to optimize the RF design of a X-band linac using the constant-impedance accelerating structure for the Tsinghua Thomson X-ray source facility.

390

A high-gradient radiofrequency (RF) gun operated in continuous-wave (CW) mode is required in various accelerating applications. Due to the high RF power loss, a traditional normal-conducting (NC) RF electron gun has difficulty meeting the requirement of generating a high-repetition-rate electron beam. The development of a scheme for a CW NC-RF gun is urgently required. Demonstrated as a photoinjector of a high-repetition-rate free-electron laser (FEL), an electron gun operated in CW mode and the VHF band is designed. An analysis of the reentrant gun cavity is presented in this paper to increase the gradient and decrease the power density and power dissipation. Referring to the analysis results, the design of a 162.5 MHz gun cavity is optimized by a multi-objective evolutionary algorithm to achieve better performance in CW mode. Multipacting and thermal analyses are also deliberated in the design to coordinate with RF and mechanical design. The optimized 162.5 MHz gun cavity can be operated in CW mode to generate a high-repetition-rate beam with voltage up to 1 MV and gradient up to 32.75 MV/m at the cathode.

561

Abstract— One of the most important devices for the High Energy Photon Source Test Facility project, the 2.6 T 32-pole 3W1 superconducting wiggler, was designed by the Institute of High Energy Physics (IHEP); its magnetic gap is 68 mm, and its storage energy is 286 kJ. It will be installed at the storage ring of the Beijing Electron Positron Collider Upgrade Project at the IHEP to replace the old permanent wiggler. The primary purpose of the cryostat is to create a safe and reliable system and realize long-term operation with zero liquid helium consumption. To maintain liquid helium temperature, four identical two-stage cryocoolers are placed symmetrically at the wiggler ends. The cryostat has only one 60 K thermal shield, which is used to reduce the heat load to the liquid helium vessel. The cryostat has several novel features, including a suspension system with little heat leakage that is self-centered during cooling of the cryostat, a special copper liner and high-efficiency condensers, three pairs of binary current leads, and three-level safety design. The cryogenic system has been cooled three times, and the residual cooling capacity is approximately 0.41 W at 4.2 K without current.

381

Heavy water moderated molten salt reactors (HWMSRs) are novel molten salt reactors (MSRs) that adopt heavy water rather than graphite as the moderator while employing liquid fuel. Owing to the high moderating ratio of the heavy water moderator and the utilization of liquid fuel, HWMSRs can achieve a high neutron economy. In this study, a large-scale small modular HWMSR (SM-HWMSR) with a thermal power of 500 MWth was proposed and studied. The criticality of the core was evaluated using an in-house Critical Search Calculation Code (CSCC), which was developed based on SCALE6.1 (Standardized Computer Analyses for Licensing Evaluation, version 6.1). The preliminary fuel cycle performances (initial conversion ratio (CR), initial fissile fuel loading mass, and temperature coefficient) were investigated by varying the lattice pitch (P) and the molten salt volume fraction (VF). The results demonstrate that the temperature coefficient can be negative over the range of investigated Ps and VFs for both ²³³U-Th and LEU-Th fuels. A core with a P of 20 cm and a VF of 20% is recommended for ²³³U-Th and LEU-Th fuels to achieve a high performance of initial CR and fuel loading. Regarding TRU-Th fuel, a core with a smaller P (~ 5 cm) and larger VF (~ 24%) is recommended to obtain a negative temperature coefficient.

387

Gamma heating, which is deposited in irradiated targets or samples, is an important issue in research reactors because it affects the safety of samples and the reactor operation. Gamma heating in the Reaktor Serba Guna G.A. Siwabessy (RSG GAS) can be measured or calculated using computer code. In this paper, we present the results obtained by using gamma calorimeters to measure the gamma heating in the central irradiation position in RSG GAS. The measurement results were verified and then compared with the calculation results obtained using the Gamset code. However, the accuracy of the calculation results obtained using Gamset was inadequate, with more than 20% error. Moreover, Gamset was initially created to calculate gamma heating in 35 MWth reactors and the RSG GAS reactor has an operating power level of 30 MWth. To address these issues, we developed a new program called NewGamset, built with an informative graphical user interface based display. NewGamset can employ new analytical approaches as it utilizes a calculation base that comprises 18 energy groups and can provide updated physical parameters of RSG GAS. The results of gamma heating measurements obtained using gamma calorimeters made of graphite, aluminum, iron, and zirconium were 2.20 ± 0.03 W/g, 2.25 ± 0.02 W/g, 2.58 ± 0.03 W/g, and 2.91 ± 0.10 W/g, respectively. In general, the calculation results were larger than the measurement results, and the average ratio of calculation to measurement result was 1.37 for Gamset and 1.02 for NewGamset. Hence, it can be concluded that NewGamset provides more accurate results than Gamset. We also report the gamma heating estimation for common elements irradiated in the RSG GAS silicide core, with an operating power level of 15 MWth and 30 MWth. We highly recommend that NewGamset be used for validating the gamma heating data of various target materials in RSG GAS.

430

The transverse momentum spectra of different types of particles produced in central and peripheral gold-gold (Au-Au) and inelastic proton-proton (pp) collisions at the Relativistic Heavy Ion Collider (RHIC), as well as in central and peripheral lead-lead (Pb-Pb) and pp collisions at the Large Hadron Collider (LHC) are analyzed by the multi-component standard (Boltzmann-Gibbs, Fermi-Dirac, and Bose-Einstein) distributions. The obtained results from the standard distribution give an approximate agreement with the measured experimental data by the STAR, PHENIX, and ALICE Collaborations. The behavior of the effective (kinetic freeze-out) temperature, transverse flow velocity, and kinetic freeze-out volume for particles with different masses is obtained, which observes the early kinetic freeze-out of heavier particles as compared to the lighter particles. The parameters of emissions of different particles are observed to be different, which reveals a direct signature of the mass-dependent differential kinetic freeze-out. It is also observed that the peripheral nucleus-nucleus (AA) and pp collisions at the same center-of-mass energy per nucleon pair are in good agreement in terms of the extracted parameters.

409

The purpose of this study is to investigate and quantify the influence of nanoparticle composition, size, and concentration on the difference between dose enhancement values derived from Monte Carlo simulations with homogeneous and structured geometrical representations of the target region in metal nanoparticle-enhanced photon brachytherapy. Values of the dose enhancement factor (DEF) were calculated for Pd-103, I-125, and Cs-131 brachytherapy sources with gold, silver, or platinum nanoparticles acting as targeting agents. Simulations were performed using the Geant4 toolkit with condensed history models of electron transport. Stringent limits were imposed on adjustable parameters that define secondary electron histories, so that simulations came closest to true event-by-event electron tracking, thereby allowing part of the nanoparticle-laden volume used for calculating the dose to be represented as a structured region with uniformly distributed discrete nanoparticles. Fine-tuned physical models of secondary radiation emission and propagation, along with the discrete geometrical representation of nanoparticles, result in a more realistic assessment of dose enhancement. The DEF correction coefficient is introduced as a metric that quantifies the absorption of secondary radiation inside the nanoparticles themselves, a phenomenon disregarded when the target region is treated as a homogeneous metal-tissue mixture, but accounted for by discrete nanoparticle representation. The approach applied to correcting DEF values both draws from and expands upon several related investigations published previously. Comparison of the obtained results to those found in relevant references shows both agreement and deviation, depending on nanoparticle properties and photon energy.

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