Vol.32,

A high-intensity continuous wave (CW) radio frequency quadrupole (RFQ) accelerator is designed for boron neutron capture therapy (BNCT). The transmission efficiency of a 20-mA proton beam accelerated from 30 keV to 2.5 MeV can reach 98.7% at an operating frequency of 200 MHz. The beam dynamics have a good tolerance to errors. By comparing the high-frequency parameters of quadrilateral and octagonal RFQ cross-sections, the quadrilateral structure of the four-vane cavity is selected owing to its multiple advantages, such as a smaller cross section at the same frequency and easy processing. In addition, tuners and undercuts are designed to tune the frequency of the cavity and achieve a flat electric field distribution along the cavity. In this paper, the beam dynamics simulation and electromagnetic design are presented in detail.

436

A corrugated structure is built and tested on many FEL facilities, providing a ’dechirper’ mechanism for eliminating energy spread upstream of the undulator section of X-ray FELs. The wakefield effects are here studied for the beam dechirper at the Shanghai high repetition rate XFEL and extreme light facility (SHINE), and compared with analytical calculations. When properly optimized, the energy spread is well compensated. The transverse wakefield effects are also studied, including the dipole and quadrupole effects. By using two orthogonal dechirpers, we confirm the feasibility of restraining the emittance growth caused by the quadrupole wakefield. A more efficient method is thus proposed involving another pair of orthogonal dechirpers.

405

Photon absorption parameters such as mass attenuation coefficients (μm), molar extinction coefficients (ε), total molecular (σt,m), atomic (σt,a) and electronic (σt,el) cross-sections, half-value layers (X1/2), tenth-value layers (X1/10), mean free paths (λ), effective atomic numbers (Zeff), and effective electron densities (Nel) were estimated for defatted soy flour (DSF), soy protein concentrate (SPC), and soy protein isolate (SPI)-based Rhizophora spp. particleboard composites substituted with 10 wt% sodium hydroxide (NaOH) and 0, 5, 10, and 15 wt% itaconic acid polyamidoamine-epichlorohydrin (IA-PAE) adhesives. Elemental composition was assessed using ultra-high-resolution field emission scanning electron microscopy-energy dispersive X-ray spectrometry (UHR-FESEM-EDX). The interaction parameters were evaluated for Kα1 photons at 16.59, 17.46, 21.21, and 25.26 keV, employing a low-energy germanium (LEGe) detector system and an ²⁴¹Am γ-ray source. X-ray diffraction characterization revealed an amorphous phase in the developed particleboard composites. Samples DSF15′, SPC15′, and SPI15′ exhibited the highest values of μm, ε, σt,m, Zeff, and Nel among all of the studied particleboard samples, within the range of measured photon energies. In addition, all of the modified samples exhibited lower X1/2, X1/10, λ, σt,a, and σt,el than the unmodified samples, with DSF-, SPC-, and SPI/NaOH/Rhizophora spp./IA-PAE (15 wt%), indicating insignificant changes. The current results of the particleboard samples’ analysis can be useful for medical radiation applications and shielding research.

332

Carbon ion radiotherapy has the advantages of better therapeutic effect and fewer side effects compared with those of X-rays in many kinds of tumors, including prostate cancer, and thus is an attractive treatment approach for prostate cancer. However, the biological effects and underlying mechanisms of carbon ion irradiation in prostate cancer are not yet fully understood. Therefore, this study systematically compared the effects of carbon ion irradiation with those of X-ray irradiation on DNA damage response and found that carbon ion irradiation was more effective than X-ray irradiation. Carbon ion irradiation can induce a high level of DNA double-strand break damage, reflected by the number of γ-H2A histone family member X foci, as well as by the foci lasting time and size. Moreover, carbon ion irradiation exhibited strong and long-lasting inhibitory effect on cell survival capability, induced prolonged cell cycle arrest, and increased apoptosis in PC-3 cells. As an underlying mechanism, we speculated that carbon ion irradiation-induced DNA damage evokes cell cycle arrest and apoptosis via the pRb/E2F1/c-Myc signaling pathway to enhance the radiosensitivity of p53-deficient prostate cancer PC-3 cells. Collectively, the present study suggests that carbon ion irradiation is more efficient than X-ray irradiation and may help to understand the effects of different radiation qualities on the survival potential of p53-deficient prostate cancer cells.

409

The time-interleaved analog-to-digital conversion (TIADC) technique is an effective method for increasing the sampling rate in a waveform digitization system. In this study, a 20-Gsps TIADC system was designed. A wide-bandwidth performance was achieved by optimizing the analog circuits, and a sufficient effective number of bits (ENOB) performance guaranteed using the perfect reconstruction algorithm for mismatch error correction. The proposed system was verified by tests, and the results indicated that a -3dB bandwidth of 6 GHz and the ENOB performance of 8.7 bits at 1 GHz and 7.6 bits at 6 GHz were successfully achieved.

382

A self-adaptive differential evolution neutron spectrum unfolding algorithm (SDENUA) is established in this study to unfold the neutron spectra obtained from a water-pumping-injection multilayered concentric sphere neutron spectrometer (WMNS). Specifically, the neutron fluence bounds are estimated to accelerate the algorithm convergence, and the minimum error between the optimal solution and input neutron counts with relative uncertainties is limited to 10^-6 to avoid unnecessary calculations. Furthermore, the crossover probability and scaling factor are self-adaptively controlled. FLUKA Monte Carlo is used to simulate the readings of the WMNS under (1) a spectrum of Cf-252 and (2) its spectrum after being moderated, (3) a spectrum used for boron neutron capture therapy, and (4) a reactor spectrum. Subsequently, the measured neutron counts is unfolded using the SDENUA. The uncertainties of the measured neutron count and the response matrix are considered in the SDENUA, which does not require complex parameter tuning or an a priori default spectrum. The results indicate that the solutions of the SDENUA agree better with the IAEA spectra than those of MAXED and GRAVEL in UMG 3.1, and the errors of the final results calculated using the SDENUA are less than 12%. The established SDENUA can be used to unfold spectra from the WMNS.

475

Neutrons have been extensively used in many fields, such as nuclear physics, biology, geology, medical science, and national defense, owing to their unique penetration characteristics. Gamma rays are usually accompanied by the detection of neutrons. The capability to discriminate neutrons from gamma rays is important for evaluating plastic scintillator neutron detectors because similar pulse shapes are generated from both forms of radiation in the detection system. The pulse signals measured by plastic scintillators contain noise, which decreases the accuracy of n–γ discrimination. To improve the performance of n–γ discrimination, the noise of the pulse signals should be filtered before the n–γ discrimination process. In this study, the influences of the Fourier transform, wavelet transform, moving-average filter, and Kalman algorithm on the charge comparison method, fractal spectrum method, and back-propagation neural network methods were studied. It was found that the Fourier transform filtering algorithm exhibits better adaptability to the charge comparison method than others, with an increasing accuracy of 6.87% compared to that without the filtering process. Meanwhile, the Kalman filter offers an improvement of 3.04% over the fractal spectrum method, and the adaptability of the moving-average filter in back-propagation neural network discrimination is better than that in other methods, with an increase of 8.48%. The Kalman filtering algorithm has a significant impact on the peak value of the pulse, reaching 4.49%, and has an insignificant impact on the energy resolution of the spectrum measurement after discrimination.

392

In loosely coupled or large-scale problems with high dominance ratios, slow fission source convergence can take extremely long time, reducing Monte Carlo (MC) criticality calculation efficiency. Although various acceleration methods have been developed, some methods cannot reduce convergence times, whereas others have been limited to specific problem geometries. In this study, a new fission source convergence acceleration (FSCA) method, the forced propagation (FP) method, has been proposed, which forces the fission source to propagate and accelerate fission source convergence. Additionally, some stabilization techniques have been designed to render the method more practical. The resulting stabilized method was then successfully implemented in the MC transport code, and its feasibility and effectiveness were tested using the modified OECD / NEA, one-dimensional slab benchmark, and the Hoogenboom full-core problem. The comparison results showed that the FP method was able to achieve efficient FSCA.

343

The Monte Carlo (MC) simulation is regarded as the gold standard for dose calculation in brachytherapy, but it consumes a large amount of computing resources. The development of heterogeneous computing makes it possible to substantially accelerate calculations with hardware accelerators. Accordingly, this study develops a fast MC tool, called THUBrachy, which can be accelerated by several types of hardware accelerators. THUBrachy can simulate photons with energy less than 3 MeV and considers all photon interactions in the energy range. It was benchmarked against the American Association of Physicists in Medicine Task Group No. 43 Report using a water phantom and validated with Geant4 using a clinical case. A performance test was conducted using the clinical case, showing that a multicore central processing unit, Intel Xeon Phi, and graphics processing unit (GPU) can efficiently accelerate the simulation. GPU-accelerated THUBrachy is the fastest version, which is 200 times faster than the serial version and approximately 500 times faster than Geant4. The proposed tool shows great potential for fast and accurate dose calculations in clinical applications.

347

The production of radionuclides ⁹⁰Sr and ¹³¹I in molten salt reactors is an attractive option to address the global shortage of radionuclides. This study evaluated the production characteristics of ⁹⁰Sr and ¹³¹I in a modular molten salt reactor, such as equilibrium time, yield, and cooling time of isotopic impurities. The fuel burn-up of a small modular molten salt reactor was analyzed by the Triton module of the scale program, and the variation in the fission yields of the two nuclides and their precursors with burn-up time. The yield of ¹³¹I and ¹³¹Te has been increasing during the lifetime. ¹³¹I has an equilibrium time of about 40 days, a saturation activity of about 40300 TBq, and while¹³¹Te takes 250 min to reach equilibrium, the equilibrium activity was about 38000 TBq. The yields of ⁹⁰Sr and ⁹⁰Kr decreased gradually, the equilibrium time of ⁹⁰Kr was short, and ⁹⁰Sr could not reach equilibrium. Based on the experimental data of molten salt reactor experiment (MSRE), the amount of nuclide migration to the tail gas and the corresponding cooling time of the isotope impurities under different extraction methods were estimated. Using the HF-H₂ bubbling method, 3.49×10⁵ TBq of¹³¹I can be extracted from molten salt every year, and after 13 days of cooling, the impurity content meets the medical requirements. Using the electric field method, 1296 TBq of ¹³¹I can be extracted from the off-gas system (its cooling time is 11 days) and 109 TBq of ⁹⁰Sr. The yields per unit power for ¹³¹I and ⁹⁰Sr is approximately 1350 TBq/MW and 530 TBq/MW, respectively, which shows that molten salt reactors have a high economic value.

528

Angle-resolved photoemission spectroscopy (ARPES) is one of the most powerful experimental techniques in condensed matter physics. Synchrotron ARPES, which uses photons with high flux and continuously tunable energy, has become particularly important. However, an excellent synchrotron ARPES system must have features such as a small beam spot, super-high energy resolution, and a user-friendly operation interface. A synchrotron beamline and an endstation (BL03U) were designed and constructed at the Shanghai Synchrotron Radiation Facility. The beam spot size at the sample position is 7.5 (V) μm × 67 (H) μm, and the fundamental photon range is 7–165 eV; the ARPES system enables photoemission with an energy resolution of 2.67 meV@21.2 eV. In addition, the ARPES system of this endstation is equipped with a six-axis cryogenic sample manipulator (the lowest temperature is 7 K) and is integrated with an oxide molecular beam epitaxy system and a scanning tunneling microscope, which can provide an advanced platform for in-situ characterization of the fine electronic structure of condensed matter.

372