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Accelerating particles to high energies with high efficiency and beam quality is crucial in developing accelerator technologies. The plasma acceleration technique, providing unprecedented high gradients, is considered as a promising future technology. While important progress has been made in plasma-based electron acceleration in recent years, identifying a reliable acceleration technique for the positron counterpart would pave the way to a linear e⁺e⁻ collider for high-energy physics applications. In this work, we show further studies of positron beam quality in moderately non-linear (MNL)* plasma wakefields. With a positron bunch of initial energy 1 GeV, emittance preservation can be achieved in optimised scenarios at 2.38 mm’mrad. In parallel, asymmetric beam collisions at the interaction point (IP) are studied to evaluate the current luminosity reach and provide insight to improvements required for positron acceleration in plasma. It is necessary to scale down the emittance of the positron bunch. In the MNL regime, a positron beam with 238 ’m’mrad level emittance implies compromise in charge or necessity for ultra-short bunches., Proceedings of the 5th North American Particle Accelerator Conference, NAPAC2022, Albuquerque, NM, USA

Journal of Instrumentation 17(05), P05042 (2022). doi:10.1088/1748-0221/17/05/P05042 special issue: "ICFA Beam Dynamics Newsletter 83", The Beam Delivery System (BDS) is a critical component of a high-energy linear collider. It transports the beam from the accelerator and brings it to a focus at the Interaction Point. The BDS system includes diagnostic sections for measuring the beam energy, emittance, and polarization, as well as collimators for machine protection. The length of the BDS increases with collision energy. Higher collision energies also require higher luminosities, and this is a significant constraint on the design for energy-frontier machines. Here, we review BDS designs based on traditional quadrupole magnets and examine the challenges involved in extending these to the Multi-TeV regime consistent with requirements for advanced accelerator concepts., Published by Inst. of Physics, London

FACET-II is a National User Facility at SLAC National Accelerator Laboratory providing 10 GeV electron beams with um-rad normalised emittance and peak currents exceeding 100 kA . FACET-II operates as a National User Facility while engaging a broad User community to develop and execute experimental proposals that advance the development of plasma wakefield accelerators. FACET-II is currently commissioned and has started with first experiments. The special features of FACET-II will be shown and first results from the experiments., Proceedings of the 31st International Linear Accelerator Conference, LINAC2022, Liverpool, UK

The morphological instability of solid/liquid (S/L) interface during solidification will result in different patterns of microstructure. In this study, two dimension (2D) and three dimension (3D) in-situ observation of solid/liquid interfacial morphology transition in Al-Zn alloy during directional solidification were performed via X-ray imaging. Under a condition of increasing temperature gradient (G), the interface transition from dendritic pattern to cellular pattern, and then to planar growth with perturbation was captured. The effect of solidification parameter (the ratio of temperature gradient and growth velocity (v), G/v) on morphological instabilities was investigated and the experimental results were compared to classical “constitutional supercooling” theory. The results indicate that 2D and 3D evolution process of S/L interface morphology under the same thermal condition are different. It seems that the S/L interface in 2D observation is easier to achieve planar growth than that in 3D, implying higher S/L interface stability in 2D thin plate samples. This can be explained as the restricted liquid flow under 2D solidification which is beneficial to S/L interface stability. The in-situ observation in present study can provide coherent dataset for microstructural formation investigation and related model validation during solidification.

Fairness with a α parameter is an important consideration to provide uniform and high quality service for each user when designing a wireless communication system. In general, α-fairness problem includes the proportional fairness and the max-min fairness. In this paper, we consider the problem of α-fairness-based joint power allocation and power splitting for massive multiple-input and multiple-output (MIMO) systems with simultaneous wireless information and power transfer (SWIPT). Different from the existing works, we utilize a low-complexity parametric optimization method to solve the non-convex proportional fairness problem. Furthermore, we develop a joint iterative algorithm to solve the general α-fairness problem and obtain the suboptimal solutions on power allocation and power splitting. Simulation results illustrate the performance of the proposed algorithm.

With the rapid development of urban intelligent transportation system, the prediction short-term of traffic flow attracts more and more attention. As the lack of the characteristics of traffic flow and appropriate models, the accurate predction of the traffic flow are facing a big challenge. A short-term traffic flow prediction model based on extreme gradient rise is proposed in this paper. The experiment results reveal the superiority of the modle by comparing with the traditional prediction model.

The traditional synchronous condenser fault diagnosis algorithm is too dependent on experience, and it cannot accurately reflect the relationship between features and failure type, resulting in the low diagnostic accuracy. Aiming at this problem, the radial basis function (RBF) neural network algorithm is used to diagnose the synchronous condenser fault. The operating parameters of synchronous condenser are used for learning and training, and the corresponding fault type output is obtained. The simulation results show that the diagnosis algorithm has a high accuracy and a small calculation error, proving that the diagnosis method can be widely used for on-line monitoring of the synchronous condenser.

Based on the detailed analysis and study of the advantages and disadvantages of the existing system, this paper develops a set of relatively perfect fault early warning, fault diagnosis and intelligent decision-making platform for the condenser based on the ubiquitous internet of things. The platform can realize the following functions. First is remote centralized monitoring of the operation state of the condenser. Second is intelligent early warning of the condenser. Third is remote fault diagnosis of the phase modulator. Forth is three-dimensional display and maintenance training of the condenser. The core technologies include data acquisition based on ubiquitous power internet of things, coordination governance among different databases and establishment of large data analysis platform, information mining technology based on large data analysis, cross-area data transmission and network security control technology, the remote on-line monitoring technology of the phase modulator. The system design mainly applies sensor technology, Internet technology, cloud computing technology, visualized intelligent diagnosis technology and reliability management technology to realize remote monitoring of the power network converter station’s phase modulator, including the monitoring of phase modulator operation parameters, reactive power remote control, remote monitoring of equipment operation status, coordinated operation status of the network and the machine. The results show that the platform of fault early warning, fault diagnosis and intelligent decision-making can apply sensor technology, Internet technology, cloud computing technology, visualized intelligent diagnosis technology and reliability management technology to realize remote monitoring of the phase modulator in power grid converter station, including the monitoring of the operation parameters of the phase modulator and the remote monitoring of reactive power, control and remote monitoring of equipment operation status, coordinated monitoring of machine network operation status, reliability management of electrical equipment, lubrication system and cooling system.