Vol.32,

The center of the stability island of super-heavy nuclei (SHN) is the subject of intense experimental and theoretical investigations and has potential technological applications. 114298Fl lies in the Z=114 isotopic chain as a persuasive candidate of the spherical double-magic nucleus in SHN, and in this study, the calculations of nuclear binding energies, one-nucleon and two-nucleon separation energies, α-decay energies, and the corresponding half-lives provide strong evidence for this point. These calculations within an improved Weizsäcker-Skyrme nuclear mass model (WS*) were performed and compared with the calculations of the finite-range droplet model (FRDM2012) and experimental data for Z=114 isotopes and N=184 isotones. Concurrently, the corresponding single-particle levels in a Woods-Saxon potential well with a spin-orbit term are calculated, which can be used as a powerful indicator to identify the shell effects existing in 114298Fl. Both the study of the properties of the isotopic chain and microphysical quantities provide a vital signal that 114298Fl is a spherical double-magic nucleus and also the center of the SHN.

372

With the development of laser technologies, nuclear reactions can happen in high-temperature plasma environments induced by lasers and have attracted a lot of attention from different physical disciplines. However, studies on nuclear reactions in plasma are still limited by detecting technologies. This is mainly due to the fact that extremely high electromagnetic pulses (EMPs) can also be induced when high-intensity lasers hit targets to induce plasma, and then cause dysfunction of many types of traditional detectors. Therefore, new particle detecting technologies are highly needed. In this paper, we report a recently developed gated fiber detector which can be used in harsh EMP environments. In this prototype detector, scintillating photons are coupled by fiber and then transferred to a gated photomultiplier tube which is located far away from the EMP source and shielded well. With those measures, the EMPs can be avoided which may result that the device has the capability to identify a single event of nuclear reaction products generated in laser-induced plasma from noise EMP backgrounds. This new type of detector can be widely used as a time-of-flight (TOF) detector in high-intensity laser nuclear physics experiments for detecting neutrons, photons, and other charged particles.

349

The isomer ^229mTh is the most promising candidate for clocks based on the nuclear transition because it has the lowest excitation energy of only 8.10±0.17 eV. Various experiments and theories have focused on methods of triggering the transition between the ground state and isomeric state, among which the electronic bridge (EB) is one of the most efficient. In this paper, we propose a new electronic bridge mechanism via two-photon excitation based on quantum optics for a two-level nuclear quantum system. The long-lived 7s_1/2 electronic shell state of ^229mTh³⁺, with a lifetime of approximately 0.6 s, is chosen as the initial state and the atomic shells (7s–10s) could be achieved as virtual states in a two-photon process. When the virtual states return to the initial state 7s_1/2, there is a chance of triggering the nucleus ²²⁹Th³⁺ to its isomeric state ^229mTh³⁺ via EB. Two lasers at moderate intensity ((10¹⁰ – 10¹⁴) W/m²), with photon energies near the optical range, are expected to populate the isomer at a saturated rate of approximately 10⁹s^-1, which is much higher than that due to other mechanisms. We believe that this two-photon EB scheme can help in the development of nuclear clocks and deserves verification via a series of experiments with ordinary lasers in laboratories.

330

We studied experimental background reconstruction methods for the measurement of the D−D¯ correlation using PYTHIA simulation. The like-sign (LS) and side-band (SB) background methods, which are widely used in the experimental measurements of single D-meson production yields, were deployed for correlation study. It was found that the LS method, which describes the combinatorial background of single D⁰ meson yields, fails to reproduce the correlated background in the D0−D0¯ correlation measurement, while the SB background method yields a good description of the background for both single D⁰ yields and the correlated background of the D0−D0¯ correlation measurement. We further examined the validity of the correlation methods under different signal-to-background ratios, providing direct references for experimental measurements.

332

In this study, we reconstruct the γ-photon energy spectrum, which is in good agreement with the experimental data of ⁸⁶Kr + ¹²C at E/A = 44 MeV within the framework of the modified EQMD model. The directed and elliptic flows of free protons and direct photons were investigated by considering the α-clustering structure of ¹²C. Compared with free protons, direct photon flows provide clearer information about the early stage of a nuclear reaction. The difference in the collective flows between different configurations of ¹²C is observed in this study. This indicates that the collective flows of direct photons are sensitive to the initial configuration. Therefore, the γ bremsstrahlung process might be taken as an alternative probe to investigate the α-clustering structure in a light nucleus from heavy ion collisions within the Fermi-energy region.

410

The development of iterative learning control combined with disturbance-observer-based (DOB) control for the digital low-level radio frequency (LLRF) system of the International Linear Collider project is presented. The objective of this study is to compensate for both repetitive (or predictable) and unpredictable disturbances in a radio-frequency system (e.g., beam loading, Lorentz force detuning, and microphonics). The DOB control approach was verified using the LLRF system at the Superconducting Test Facility (STF) at KEK in the absence of a beam. The method comprising DOB control combined with an iterative learning control algorithm was then demonstrated in a cavity-simulator-based test bench, where a simulated beam was available. The results showed that the performance of the LLRF system was improved, as expected by this combined control approach. We plan to further generalize this approach to LLRF systems at the STF and the future International Linear Collider project.

379

The introduction of solvent additives is one of the most common approaches for enhancing the power conversion efficiency of organic solar cells (OSCs). However, the use of solvent additives has some negative effects, and an understanding of how solvent additives affect OSCs is currently limited. In this study, we developed an in situ grazing incidence wide-angle X-ray scattering (GIWAXS) technique in the SAXS beamline (BL16B1) at the Shanghai Synchrotron Radiation Facility, and the additive effects of 1,8-diiodoctane (DIO) on the performance and morphology evolution of the PTB7-Th/PC₇₁BM device was investigated in depth. The results revealed that the crystal size increased with the volume ratio of DIO, and a drastic evolution of lattice space and crystal coherence length was observed during thermal annealing for the first time, to our knowledge. The discrete PC₇₁BM molecules dissolved by DIO have an effect similar to that of the nucleating agent for PTB7-Th, boosting the crystallization of PTB7-Th, reducing phase separation, and inducing more drastic morphological evolution during thermal annealing. Our results provide a deep perspective for the mechanism of solvent additives, while also showing the significance and feasibility of the in situ GIWAXS technique we developed at BL16B1.

440

This paper reports on the design, fabrication, RF measurement, and high-power test of a prototype accelerator — such as 11.424 GHz with 12-cells — and a traveling wave of two halves. It was found that the unloaded gradient reached 103 MV/m during the high-power test and the measured breakdown rate, after 3.17×10⁷ pulses, was 1.62×10^-4 /pulse/m at 94 MV/m and a 90 ns pulse length. We thus concluded that the high-gradient two-half linear accelerator is cost-effective, especially in high-frequency RF linear acceleration. Finally, we suggest that silver-based alloy brazing can further reduce costs.

353

The spatial resolution of a commercial two-dimensional (2D) ionization chamber (IC) array is limited by the size of the individual detector and the center-to-center distance between sensors. For dose distributions with areas of steep dose gradients, inter-detector dose values are derived by the interpolation of nearby detector readings in the conventional mathematical interpolation of 2D IC array measurements. This may introduce significant errors, particularly in proton spot scanning radiotherapy. In this study, by combining logfile-based reconstructed dose values and detector measurements with the Laplacian pyramid image blending method, a novel method is proposed to obtain a reformatted dose distribution that provides an improved estimation of the delivered dose distribution with high spatial resolution. Meanwhile, the similarity between the measured original data and the downsampled logfile-based reconstructed dose is regarded as the confidence of the reformatted dose distribution. Furthermore, we quantify the performance benefits of this new approach by directly comparing the reformatted dose distributions with 2D IC array detector mathematically interpolated measurements and original low-resolution measurements. The result shows that this new method is better than the mathematical interpolation and achieves gamma pass rates similar to those of the original low-resolution measurements. The reformatted dose distributions generally yields a confidence exceeding 95%.

347

The development of a high-gradient accelerating structure is underway to construct a compact proton linear accelerator for cancer treatment. Extensive experiments and numerous studies are being conducted to develop compact linear accelerators for proton therapy. Optimization of the electromagnetic and mechanical design has been performed to simplify the manufacturing process and reduce costs. A novel high-gradient structure with a low relativistic proton velocity (β), v/c = 0.38, was designed, fabricated, and tested at high power. The first full-scale prototype was also successfully tested with high radio frequency (RF) power, a repetition rate of 50 Hz, and pulse length of 3 µs to reach a high gradient of 46 MV/m using a 50 MW S-band klystron power supply obtained from the Shanghai Soft X-ray Free Electron Laser Facility. This is the first high-power test in China, which is in line with the expected experimental goal. This study presents preliminary high-power testing of S-band standing wave accelerating structures with 11 cells. This work aims to verify the feasibility of using a high-gradient RF accelerating structure in compact proton therapy facilities. The cold test of the prototype cavity was completed in advance. Details of the high-power RF test setup, the process of RF conditioning, and the high-power results are described.

495

Space scientific exploration is rapidly becoming the primary battlefield for humankind to explore the universe. Countries worldwide have launched numerous space exploration satellites. Accurate calibration of the detectors on the ground is a crucial element for space science satellites to obtain observational results. For the purpose of providing calibration for various satellite-borne detectors, multiple monochromatic X-rays facilities have been built at the National Institute of Metrology, P.R. China (NIM). These facilities mainly pertain to grating diffraction and Bragg diffraction, and the energy range of the produced monochromatic X-rays is 0.218–301 keV. These facilities have a high performance in terms of energy stability, monochromaticity, and flux stability. The monochromaticity was greater than 3.0%. The energy stability of the facility is 0.02% at 25 keV over 8 h, and the flux stability was within 1.0% at 25 keV over 8 h. Calibration experiments on the properties of satellite-borne detectors, such as energy linearity, energy resolution, detection efficiency, and temperature response, can be conducted at the facilities. Thus far, the calibration of two satellites has been completed by the authors, and the work on three other satellites is in progress. This study will contribute to the advancement of X-ray astronomy the development of Chinese space science.

529

On-the-fly Doppler broadening of cross-sections is important in Monte Carlo simulations, particularly in Monte Carlo neutronics-thermal hydraulics coupling simulations. Methods such as Target Motion Sampling (TMS) and windowed multipole as well as a method based on regression models have been developed to solve this problem. However, these methods have limitations such as the need for a cross-section in an ACE format at a given temperature or a limited application energy range. In this study, a new on-the-fly Doppler broadening method based on a Back Propagation (BP) neural network, called hybrid windowed networks (HWN), is proposed to resolve the resonance energy range. In the HWN method, the resolved resonance energy range is divided into windows to guarantee an even distribution of resonance peaks. BP networks with specially designed structures and training parameters are trained to evaluate the cross-section at a base temperature and the broadening coefficient. The HWN method is implemented in the Reactor Monte Carlo (RMC) code, and the microscopic cross-sections and macroscopic results are compared. The results show that the HWN method can reduce the memory requirement for cross-section data by approximately 65%; moreover, it can generate k_eff, power distribution, and energy spectrum results with acceptable accuracy and a limited increase in the calculation time. The feasibility and effectiveness of the proposed HWN method are thus demonstrated.

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