Vol.30,

The Sallen–Key filter (S–K) is widely used in nuclear pulse signal processing because of its simple working principle and good performance. Related research has only reviewed the recursive numerical model of digital S–K using idealized parameters. The use of digital S–K thus has limitations under these circumstances. This paper comprehensively deduces a recursive numerical model of digital S–K and discusses the effects of resistance and capacitance on the filter quality factor, cutoff frequency and amplitude-frequency response. The numerical recursive function, transfer function and amplitude-frequency response are analyzed using different parameters. From a comparative analysis of the shaper in a simulation and an actual nuclear signal, an optimal parameter selection principle is obtained. Using different forming parameters, the energy resolution and pulse counting rate of the ⁵⁵Fe energy spectrum are compared and analyzed based on a Si-PIN detector. Capacitance has a stronger influence on the Gaussian shape, whereas the influence of resistance is stronger on the shaping amplitude.

449

In cases of high radiation emergencies, we propose a surface contamination monitor (SCM) that can quickly measure and pinpoint the contamination distribution in the affected population. Thick gaseous electron multiplier (THGEM) has several advantages, including fast response time and good spatial resolution. Based on new THGEMs, a two-dimensional imaging detector was developed for alpha detection, with a position resolution greater than 3 mm. The detector design and test results are described in this paper. Fast radiation imaging SCMs, with a 40×40 mm sensitive area, are currently under development.

569

A foil–microchannel plate (MCP) detector, which uses electrostatic lenses and possesses both good position and timing resolutions, has been designed and simulated for beam diagnostics and mass measurements at the next-generation heavy-ion-beam facility HIAF in China. Characterized by low energy loss and good performances of timing and position measurements, it would be located at focal planes in fragment separator HFRS for position monitoring, beam turning, Bρ measurement, and trajectory reconstruction. Moreover, it will benefit the building-up of a magnetic-rigidity–energy-loss–time-of-flight (Bρ–ΔE–TOF) method at HFRS for high-precision in-flight particle identification (PID) of radioactive isotope (RI) beams on an event-by-event basis. Most importantly, the detector can be utilized for in-ring TOF and position measurements, beam-line TOF measurements at two achromatic foci, and position measurements at a dispersive focus of HFRS, thus making it possible to use two complementary mass measurement methods (isochronous mass spectrometry (IMS) at the storage ring SRing and magnetic-rigidity–time-of-flight (Bρ-TOF) at the beam-line HFRS) in one single experimental run.

474

Low-level radio frequency (LLRF) systems stabilize the electromagnetic field in the RF cavities used for beam acceleration in particle accelerators. Reliable, accurate, and precise detection of RF amplitude and phase is particularly important to achieve high field stability for pulsed accelerators of free-electron lasers (FEL). The digital LLRF systems employ analog-to-digital converters to sample the frequency down-converted RF signal, and use digital demodulation algorithms to calculate the RF amplitude and phase. Different sampling strategies and demodulation algorithms have been developed for these purposes and are introduced in this paper. This article focuses on advanced topics concerning RF detection, including accurate RF transient measurement, wideband RF detection, and RF detection with an asynchronous trigger, local oscillator, or clock. The analysis is based on the SwissFEL measurements, but the algorithms introduced are general for RF signal detection in particle accelerators.

494

The speciation and atomic structures of corrosion products in Ni-based alloys could provide basic information for understanding the Te corrosion mechanism. In this paper, two-dimensional synchrotron-radiation-induced grazing-incidence X-ray diffraction (2D SRGI-XRD) was used to characterize the corrosion products of a Ni-18%Cr binary alloy at temperatures from 600 °C to 1000 °C. The results showed that a film of CrTe is preferentially formed when Te reacts with the Ni-based alloy at low temperatures (below 900 °C), while CrTe and Ni₃Te₂ are formed at 900 °C. Moreover, at a temperature of 1000 °C, a solid solution is formed without any changes in the Ni-Cr substrate lattice parameters. Furthermore, X-ray absorption fine structure (XAFS) and wavelet transform (WT) analyses were used to investigate the atomic local structure of Te. The investigation indicated that Te atoms diffuse into the Ni-Cr substrate to form a substitutional Ni-Cr-Te solid solution at 1000 °C. Notably, based on a discussion of the thermodynamics of the chemical reaction process, CrTe is considered to be the most stable and prevalent corrosion product due to its comparatively lower Gibbs free energy of formation. These results demonstrate that the Ni-18%Cr alloy is capable of resisting the diffusion of Te atoms.

624

Beam lifetime is dominated by Touschek scattering at the Shanghai Synchrotron Radiation Facility (SSRF). Touschek loss rate is affected by probability for scattering beyond the RF acceptance and the volume charge density of the bench. In the phase II upgrade of the SSRF, a third harmonic superconducting cavity will be used to enhance the Touschek lifetime by lengthening the bunches. The Touschek lifetime improvement factor is affected by the voltage of a harmonic cavity. To stabilize the cavity voltage, a tuning control system was designed to control it. The design of the tuning control system was based on the SSRF third generation low-level RF control system. Some hardware and specialized algorithms were redesigned to fit the harmonic cavity control. The design of the tuning control system is complete, and the control system has been tested. The test result shows that the fluctuation of amplitude is < ±0.34% within 1.5 h, which satisfies the stability requirement.

503

This paper describes a real-time beam tuning method with an improved asynchronous advantage actor-critic (A3C) algorithm for accelerator systems. The operating parameters of devices are usually inconsistent with the predictions of physical designs because of errors in mechanical matching and installation. Therefore, parameter optimization methods such as pointwise scanning, evolutionary algorithms (EAs), and robust conjugate direction search (RCDS) are widely used in beam tuning to compensate for this inconsistency. However, it is difficult for them to deal with a large number of discrete local optima. The A3C algorithm, which has been applied in the automated control field, provides an approach for improving multi-dimensional optimization. The A3C algorithm is introduced and improved for the real-time beam tuning code for accelerators. Experiments in which optimization is achieved by using pointwise scanning, the genetic algorithm (one kind of EAs), and the A3C-algorithm are conducted and compared to optimize the currents of four steering magnets and two solenoids in the low-energy beam transport section (LEBT) of the Xi’an Proton Application Facility (XiPAF). Optimal currents are determined when the highest transmission of a radio frequency quadrupole (RFQ) accelerator downstream of the LEBT is achieved. The optimal work points of the tuned accelerator were obtained with currents of 0 A, 0 A, 0 A, and 0.1 A, for the four steering magnets, and 107 A and 96 A for the two solenoids. Furthermore, the highest transmission of the RFQ was 91.2%. Meanwhile, the lower time required for the optimization with the A3C algorithm was successfully verified. Optimization with the A3C algorithm consumed 42% and 78% less time than pointwise scanning with random initialization and pre-trained initialization of weights, respectively.

605

The radioactive isotope ⁶⁰Co is used in many applications, and is typically produced in heavy water reactors. As most of the commercial reactors in operation are pressurized light water reactors (PWRs), the world supply of high level radioactive cobalt would be greatly increased if ⁶⁰Co could be produced in them. Currently, ⁶⁰Co production in PWRs has not been extensively studied; for the ⁵⁹Co (n, γ) ⁶⁰Co reaction, the positioning of ⁵⁹Co rods in the reactor determines the rate of production. This article primarily uses the models of ⁶⁰Co production in Canadian CANDU power reactors and American boiling water reactors; based on relevant data from the pressurized water Daya Bay Nuclear Power Plant, a PWR core model is constructed with the Monte Carlo N-Particle (MCNP) Transport Code; this model suggests changes to existing fuel assemblies to enhance ⁶⁰Co production. In addition, the plug rods are replaced with ⁵⁹Co rods in the improved fuel assemblies in the simulation model to calculate critical parameters including the effective multiplication factor, neutron flux density, and distribution of energy deposition. By considering different numbers of ⁵⁹Co rods, the simulation indicates that different layout schemes have different impact levels, but the impact is not large. As a whole, the components with four ⁵⁹Co rods have a small impact, and the parameters of the reactor remain almost unchanged when four ⁵⁹Co rods replace the secondary neutron source. Therefore, in theory, the use of a PWR to produce ⁶⁰Co is feasible.

649

Uranium hexafluoride (UF₆) leakage accidents represent one of the most serious classes of accidents in the gasification process in nuclear fuel manufacturing facilities. Common UF₆ leakage accidents include various fault conditions, such as pipeline and valve breakages or ruptures and pipeline blockages. By establishing goal-oriented (GO) operators that can represent multi-fault states, this study estimates the probabilities of various fault states corresponding to UF₆ leakage accidents in the gasification process using the GO methodology, and analyzes the system reliability. This article expands the scope of the GO methodology, and provides technical support for reliability analysis using the GO methodology in multi-fault systems.

531

In this paper, waste clay was cured with ethyl acetate to obtain treated clay (TC), which was modified with gallic acid to obtain a low-cost sorbent that was characterized by EDX, SEM, and FTIR analysis. Uranium(VI) adsorption was achieved using the batch adsorption method on the TC and gallic acid modified treated clay (GMTC). The maximum uptakes of U(VI) on TC and GMTC were 37.2 and 193.0 mg/g, respectively. The U(VI) adsorption kinetics on the TC and GMTC sorbents were well-fitted by the pseudo-second-order mechanism, and the adsorption equilibrium followed the Langmuir model. The optimum parameters were applied to El Sela leach solution for uranium recovery.

589

Artificial Neural Networks (ANNs) are a core component of artificial intelligence and are frequently used in machine learning. In this report, we investigate the use of ANNs to recover the saturated signals acquired in high-energy particle and nuclear physics experiments. The inherent properties of the detector and hardware imply that particles with relatively high energies probably often generate saturated signals. Usually, these saturated signals are discarded during data processing and therefore, some useful information is lost. Thus, it is worth restoring the saturated signals to their normal form. The mapping from a saturated signal waveform to a normal signal waveform constitutes a regression problem. Given that the scintillator and collection usually do not form a linear system, typical regression methods such as multi-parameter fitting are not immediately applicable. One important advantage of ANNs is their capability to process nonlinear regression problems. To recover the saturated signal, three typical ANNs were tested including Backpropagation (BP), Simple Recurrent (Elman), and Generalized Radial Basis Function (GRBF) neural networks (NNs). They represent a basic network structure, a network structure with feedback, and a network structure with a kernel function, respectively. The saturated waveforms were produced mainly by the environmental gamma in a liquid scintillation detector for the China Dark Matter Detection Experiment (CDEX). The training and test data sets consisted of 6,000 and 3,000 recordings of background radiation, respectively, in which saturation was simulated by truncating each waveform at 40% of the maximum signal. The results show that the GBRF-NN performed best as measured using a Chi-square test to compare the original and reconstructed signals in the region in which saturation was simulated. A comparison of the original and reconstructed signals in this region shows that the GBRF neural network produced the best performance. This ANN demonstrates a powerful efficacy in terms of solving the saturation-recovery problem. The proposed method outlines new ideas and possibilities for the recovery of saturated signals in high energy particle and nuclear physics experiments. This study also illustrates an innovative application of machine learning in the analysis of experimental data in particle physics.

457

The ultimate need to account for the partial amount of energy deposited in target tissue/organ resulting from internal inhalation, ingestion, and injection intakes of radionuclides, defined by the Medical Internal Radiation Dosimetry committee as the specific absorbed fraction (SAF), has become obvious. In this study, we assessed the SAF values for self- and cross-absorption, which were calculated for a uniform distribution of monoenergetic photon and electron emitters with energies ranging from 15 keV to 3 MeV. The voxelized human phantom "High-Definition Reference Korean - man’’ (HDRK-man), which was implemented using the Monte Carlo simulation code GEANT4 (version 10.1), was used for several combinations of target–source organs. The results were compared to those of the International Commission on Radiological Protection Reference (ICRP133) and Zubal phantoms. It was found that the SAF values of the three models have a similar trend. However, the SAF values for the HDRK-man phantom were higher than those of the other two models, with a relatively good agreement with those for the ICRP133 phantom (differences of 13.9 ± 2.8 and 12.1 ± 3.2 for photon and electron emitters, respectively). To analyze the differences in SAF values, we calculated the chord length distributions (CLDs) for selected target–source combinations. The parameters of organ mass (or volume) and CLDs, in addition to the adopted computational procedures mainly cause such discrepancies. For realistic radionuclide emission spectra, an overall overestimation was observed when computing the S values for three radiopharmaceuticals studied (I-131, In-111, and Lu-177) and for liver–spleen intra and inter-organ absorption when compared with published data. The new arrangement of S and SAF values is expected to add value for multidisciplinary research and clinical communities.

501

Single-event effects (SEEs) induced by medium-energy protons in a 28 nm system-on-chip (SoC) were investigated at the China Institute of Atomic Energy. An on-chip memory block was irradiated with 90 MeV and 70 MeV protons, respectively. Single-bit upset and multi-cell upset events were observed, and an uppermost number of 9 upset cells was discovered in the 90 MeV proton irradiation test. The results indicate that the SEE sensitivities of the 28 nm SoC to the 90 MeV and 70 MeV protons were similar. Cosmic Ray Effects on Micro-Electronics Monte Carlo simulations were performed and demonstrate that protons can induce effects in a 28 nm SoC if their energies are greater than 1.4 MeV and that the lowest corresponding linear energy transfer was 0.142 MeV·cm²·mg^-1. The similarities and discrepancies of the SEEs induced by the 90 MeV and 70 MeV protons were analyzed.

577

In order to meet the requirements of the Circular Electron Positron Collider (CEPC), a 650 MHz 2-cell superconducting cavity was proposed and designed. In this study, we show the progress in the cavity design for the CEPC. The radio frequency (RF) and mechanical designs are ready for the first design version, called CEPC-V1. A crymodule, which consists of two 650 MHz 2-cell cavities was scheduled last year. Therefore, prototypes of the 2-cell cavity based on this design were fabricated and tested the following year. The vertical test results show that multipacting (MP) exists from 10 MV/m to 19 MV/m. This will increase the operational risk of the CEPC collider, while the continuous wave operation for the 650 MHz cavity is 19.7MV/m. Two trapped modes were also found, which exist because of the identical half-cell design. Therefore, a few improvements regarding MP and more efficient extraction of higher order mode power are discussed. A new type of cavity design, called CEPC-V2, is also discussed in this paper.

559