bluuebunny/crossref_metadata_2025 huggingface dataset:
Research on AHP-fuzzy comprehensive evaluation method and application
Authors: Yuan Kaiyou , Li Heng , Jiang Ming
Published: September 2020

Considering the limitation of AHP-fuzzy comprehensive evaluation method on the isomorphism and mutual exclusion of comment sets, it is difficult to use this method to evaluate actual cases with different dimension comment sets or check comment grades. This paper propounded an improved AHP-fuzzy comprehensive evaluation method with heterogeneous and check comment set, and the proposed method was further applied to the comprehensive evaluation of the evaluation state of collegiate teaching quality. Results illustrated that the improved method excelled not only in analysing and comparing the membership degree of each evaluation grade of the ultimate evaluation factors, but also in examining and evaluating the expected compliancedegree of each evaluation factor. The evaluation results were demonstrated to be more objective, accurate and applicable in a much wider scope.
A right preconditioner for the LSMR method
Authors: Hasanpour Afsaneh , Mojarrab Maryam
Published: September 2020

The LSMR (Least Squares Minimal Residual) method is an absorbing solver that can solve linear systemAx=band least squares problemmin||Ax=b|| where A is a sparse and large matrix. This method is based on the Golub-Kahan bidiagonalization process and sometimes it may converge slowly like other methods. I n order to prevent this event, a right preconditioner for LSMR method is presented to solve large and sparse linear system which used for LSQR (Least Squares with QR factorization) method before. Numerical examples and comparing the preconditioned LSMR method to unpreconditioned LSMR method would show the effectiveness of the preconditioner. I t is obtained from this paper that PLSMR (Preconditioned LSMR) method has a better performance in reducing the number of iterations and relative residual norm in comparing with the original LSMR method.
Time fractional CGMY model for the numerical pricing of European call options
Authors: Wang Xiaoxia , Xing Jianhong
Published: September 2020

Evolutionary equations containing fractional derivatives have been widely used in financial models and can describe anomalous diffusion and transmission dynamics in some complex systems. We assumes that option pricing obeys the infinite jump CGMY process and treats stock price fluctuations as a fractal transmission system, A time fractional CGMY option pricing (TFCGMY) model is obtained. The L1 approximation of the Caputo fractional derivative and the modified GL approximation are used to discretize the time and space fractional order operators; the first order space derivative is discretized using the central difference quotient. The TFCGMY model and the above numerical techniques are used for the pricing analysis of European call options. By comparing and analyzing the option pricing model with the Black-Scholes model and the CGMY model shows that the introduction of time fractional differentiation can better capture the jump characteristics of stock prices of options.
Compact implicit integration factor method for two-dimensional space-fractional advection-diffusion-reaction equations
Authors: Jian Huanyan , Huang Tingzhu , Gu Xianming , Zhao Yongliang
Published: September 2020

In this paper, we intend to develop an effective numerical method to solve a class of two-dimensional space-fractional advection-diffusion-reaction equations. After spatially discretizing this equation using the fractional centered difference formula, it leads to a system of nonlinear ordinary differential equations. The compact implicit integration factor method is applied to solve the resulting system to achieve good stability and robustness. Linear stability analysis and numerical experiments are given to verify that the compact implicit integration factor method has excellent efficiency and stability properties.
Existence and uniqueness of positive fuzzy solution for a three-order fuzzy difference equation
Authors: Jia Lili , Wang Changyou , Yang Qiang
Published: September 2020

Our aim in this paper is to study a three-order fuzzy difference equation. Firstly, the fuzzy set theory is used to transform the fuzzy difference equation into the corresponding ordinary difference equations with parameters α, α ∊ (0,1]. And then, the existence and uniqueness for the solution to the ordinary difference equations are obtained by the iteration method, the inequality technique and the mathematical induction. Finally, the existence and uniqueness for the solution of the fuzzy difference equation is proved.
Solving fuzzy linear matrix equation
Authors: Shang Dequan , Guo Xiaobin
Published: September 2020

In this paper a class of fuzzy linear matrix equation AXB=C in which A and B are crisp matrices and C is a fuzzy numbers matrix, is investigated by using the embedding approach. A new matrix method for calculating the solution is designed in detail and a sufficient condition for the existence of strong fuzzy solution is derived. An example is given to illustrate our proposed method. Our result enriches the fuzzy linear systems theory.
Oscillation of second-order mixed nonlinear neutral delay differential equation
Authors: Cui Ping , Liu Jun
Published: September 2020

In this paper, we study oscillatory behavior of a class of second-order mixed nonlinear neutral delay differential equation. By using of extended Riccati transformation, integral averaging and inequality technique, a new oscillation criteria of the equation were established, which had extended the results in the recent literatures.
A Bayesian level set method for inverse source scattering problems with multi-frequencies
Authors: Huang Jiangfeng
Published: September 2020

This paper concerns the reconstruction of the support of source function based on the Bayesian level set approach. The unknown source to be reconstructed is assumed to be piecewise constant with a known value. In this setting, the support of the source function can be characterized by the level set functions. In the Bayesian level set inversion, the solution of the inverse problem is posterior distribution. The Markov Chain Monte Carlo (MCMC) algorithm is applied to generate the samples of the posterior distribution. The numerical results show the effectiveness of the proposed method and the dependence of the posterior samples on the flexible and proper smoothness priors with the Whittle-Matérn Gaussian random fields.
On the distance spectrum of windmill graphs
Authors: Wang Zhiping , Xu Jiaxue , Xu Xiaojing
Published: September 2020

The distance Laplacian matrix and the distance signless Laplacian matrix of a connected graph G are defined by LD(G) = TrG−D(G) and QD(G) = TrG + D(G). By a harmonious labelings of vertex set, the distance matrix of windmill graphs

K

n

(
m
)

is described as a block matrix. In this paper, we obtain the eigenvalues and the corresponding eigenvectors of the distance matrix, the distance Laplacian matrix and the distance signless Laplacian matrix of windmill graphs

K

n

(
m
)

.
Based on multiple linear regression analysis of ability of medical postgraduate students to express SPSS experiment results with three-line table
Authors: Hu Ziquan
Published: September 2020

Medical postgraduate students (MPS) can select the appropriate statistical methods to do the SPSS experiments and view the experimental results after they have taken SPSS course. It is vital for MPS to exactly convert SPSS experiment results into three-line table in their academic papers. This paper investigated the Ability of MPS in Expressing SPSS experiment Results with Three-Line Table (AERTLT). The enrolled MPS in Southwest Medical University filled in the questionnaire about AERTLT on Jan, 2019. Questionnaire data are analysed using Multiple Linear Regression (MLR). Complex decision factor R
2=0.834254 and adjoint probability p<0.001 in MLR suggest the linear correlation between AERTLT and 16 factors passes test. Then backward deletion variable method is employed to repeatedly delete the factor whose coefficient is the minimum value in partial f-test. AERTLT can be expressed by four significant factors i.e. “Analytical results in comparison of mean and population mean”, “Analytical results in regression analysis”, “Comment description in three-line table”, and “P-Error in insufficient sample size or unsatisfactory univariate analysis”. These four factors are the key point for SPSS course to cultivate MPS in the medical universities and colleges.
Leaf image recognition and classification based on GBDT-probabilistic neural network
Authors: Tang Zhixuan
Published: September 2020

In this paper, the binary images of 100 kinds of leaves are used for leaf recognition. Firstly, we screen 35 important features and use the grey clustering analysis to establish the quantitative feature system of leaves. Then we use the gradient descent tree algorithm (GBDT) to select core features and use probabilistic neural network (PNN) to recognize and classify leaves, constructing a hybrid GBDT-PNN model. In the end, we obtain the classification results of leaves to evaluate model performance and the influence of core features on the model. The results show that the accuracy rate of GBDT-PNN model using 12 core features is 92.75%. And the accuracy rate with all 35 features is 93.5%. It illustrates that the model has great performance and core features have high influence on the model. By comparing with other commonly used deep learning algorithms and models, it is verified that the GBDT-PNN image recognition and classification model is effective and has high accuracy.
The application of Euclid approach degree comprehensive evaluation method in credit evaluation of commercial circulation enterprises
Authors: Zhou Li , Wang Lizhi , Zhao Yan , Li Xianghua
Published: September 2020

Based on the thorough analysis of the factors affecting the credit level of commercial circulation enterprises, a scientific and systematic evaluation index system was established. By adopting the fuzzy matter-element analytical method, which especially suits the multi-index and incompatibility issue, the evaluation model was built. The comprehensive integrated weighting method was applied for the determination of the index weight. Meanwhile, the subjective and objective information were considered comprehensively to elaborate the inherent law of the commercial circulation enterprise credit risk evaluation, which provide a practical and effective method for judging the credit level of commercial circulation enterprises and analyzing the key influencing factors of credit evaluation, and also provide a direction and reference for improving the credit level of commercial circulation enterprises.
A dynamical-scanning inner product based on Euclidean inner product
Authors: Chen Ray-Ming
Published: September 2020

Euclidean dot product plays an important role in data analysis and relation comparison for its intuitive properties. However, for some complicated structures, for example, time series, it would be insufficient to construct a complete theory via this product. In order to resolve and accommodate these issues, we devise a dynamical-scanning inner product which would take the interaction, in particular in the sense of time shift, between two vectors into consideration and yield a relation that contains much more information. Though this device is based on Euclidean dot product, it is more much suitable and flexible for handling some complicated mathematical objects. In addition, we also construct a dynamical-scanning inner product for function spaces. In the end, we show how to apply our devices on both matrix representations and time series. These exploration might delve into some intrinsic properties of some mathematical concepts or models.
Convergence of an alternating direction and projection method for sparse dictionary learning
Authors: Zhou Yijia , Xu Lijun
Published: September 2020

In this paper, we focus on sparse dictionary learning that is widely used as a data processing technique in many real-world applications. Based on the frame of alternating direction method of multiplier (ADMM), we extend to an alternating direction and projection method for sparse dictionary learning. By introducing proximal mapping and the equivalence to the corresponding projection, a partial convergence result of this multi-block and nonconvex ADMM algorithm is given that the algorithm converges to a Karush-Kuhn-Tucker point whenever it converges.
An algorithm for generating uniform points on a cylindrical surface
Authors: Zhu Jiayi , Li Hongjun
Published: September 2020

The existing Poisson-disk sampling methods work well in traditional space, whatever two dimensional or three dimensional space. However, there are few methods on generating random points in non-Euclid space. For generating uniform points on the cylinder surface, we propose an algorithm which combines Poisson-Disk sampling algorithm with cylindrical distance constraints in this paper. Experiment results show that the quality of the point set generated by the proposed algorithm is better than that generated by the pseudo-random number method in both uniformity and stability.
A numerical method for solving the time fractional reaction-diffusion equation with variable coefficients on the whole line
Authors: Liu Zeting , Shen Yanfei
Published: September 2020

This paper focuses on numerically solving the time fractional reaction-diffusion equation on the whole line. A numerical scheme is constructed based on Hermite pseudospectral method, we use finite difference scheme in time direction while Hermite-Gauss points in space. Several numerical results for the Hermite pseudospectral scheme are provided to confirm that a second-order time accuracy and spectral accuracy in space can be obtained.
Influence factors analysis on traffic jam for a new lattice hydrodynamic model on gyroidal road
Authors: Meng Xiangpei , Yan Liying
Published: September 2020

In the paper, an extended one-dimensional lattice hydrodynamic model is proposed to investigate the related factors on a gyroidal road (i.e. a curved road with a slope). We investigate the related influences on uniform traffic jam analytically and numerically. Based on control theory, condition for no traffic jam is obtained analytically. Finally, simulations are carried out to verify the new lattice hydrodynamic model and numerical simulations are consistent with the theoretical results.Results show that the related factors including the friction coefficient, radius of curvature and slope of a gyroidal road have major effect on the stability of traffic flow respectively.
Short-term traffic flow prediction on campus based on modified PSOBP neural network
Authors: Zeng Cheng , Hua Chenye , Lei Tingyu , Xiao Xinping
Published: September 2020

In order to ensure the efficiency of daily passage on campus and prevent the occurrence of safety accidents, an improved prediction method of optimized BP neural network based on modified particle swarm optimization algorithm (PSO) was proposed. In this modified PSO algorithm, we propose a mutation operator to avoid particles plunging into local optimization, using the modified PSO algorithm to optimize the solution of weight and threshold in BP neural network. The prediction method is applied to the time series of the observed campus traffic flow for effective verification, and the result shows that the method has better nonlinear fitting ability and higher prediction accuracy for the short-term traffic flow on campus.
Exact controllability of a first-order hyperbolic equation with an intermediate point memory
Authors: Chen Jingwen , Zhou Zhongcheng
Published: September 2020

In this paper, we discuss the exact controllability of a first-order hyperbolic equation with an intermediate point memory by boundary control. We choose a Volterra and Fredholm transformation transferring the original control system into a target control system with controllability property. Then, we prove the exact controllability of the original control system in terms of the invertibility of the transformation and the controllability of the target control system.
Comparing the economics welfare on leading rice exports countries based on copula SEM: the case of India, Thailand, and Vietnam
Authors: Nunti Chonrada , Yamaka Woraphon , Boonyakunakorn Petchaluck
Published: September 2020

This paper aims to investigate economics welfare gain from main rice export countries, namely India, Thailand, and Vietnam, by measuring the demand and supply of exporters and importers estimated by the copula-based Simultaneous ECM Approach. This model exploits a benefit of copula functions which allow the error’s distribution of both demand and supply equations to have more realistic distributions. The highlighted empirical results show the adjustment of importing countries to the equilibrium. Thai rice export market can adjust better than the other two countries. This means that the export market is very strong. In the supply side, India is the fastest country in adjusting to its equilibrium. For the economic welfare aspect, the most welfare benefits in Thai rice trade belong to importing countries. Whereas, the most welfare benefits in India rice trade belong to exporting countries.
Joint mean-correlation model and its application to NorStOP binary data
Authors: Peng Cheng , Yang Yihe , Zhou Jie , Pan Jianxin
Published: September 2020

In this paper we propose a generalized estimating equations method to joint model the mean and correlation structures for longitudinal binary data based on Gaussian copula, and apply it to a large cohort study for the UK’s North Staffordshire Osteoarthritis Project (NorStOP), where the responses can be pre-processed to binary variables. The resulting estimators for the mean and correlation parameters are proven to be consistent and asymptotically normally distributed. Since the theory and simulation results were studied in our previous manuscript [1], we give a brief introduction of our approach but mainly focus on its application to the NorStOP data.
Hawgent dynamic mathematic software as mathematics learning media for teaching quadratic functions
Authors: Tanu Wijaya Tommy , Ying Zhou , Chotimah Siti , Bernard Martin , Zulfah  , Astuti
Published: September 2020

According to the observation of schools in Indonesia, the quadratic function graph is a lesson for junior high school students. For it is an abstract concept, students have difficulties to understand and picture out the graph functions. The main purpose of this research is to design a learning media to improve students’ learning achievement by using hawgent dynamic mathematic software. The method of this research is research and development method. The target audience of this research were 32 students in experimental class and 32 students in controlled class. The result of this research is the material expert, research and media experts obtaining “valid” criteria. This means that the software is better than traditional teaching methods as students are able to easily visualise and generalise the graphical form of the quadratic equation. This automatically increases student’s learning achievement and makes them find math interesting.
Research on the results of the advanced mathematics teaching of college students of science: the effect of STC teaching mode based on “Internet +”
Authors: Zheng Zhibo , Zhao Wenyan , Liu Guoqi , Du Yanan , Sun Jiangjie
Published: September 2020

We uses markov evaluation model to evaluate the effectiveness of STC teaching (STC teaching mode is a method of combining online services and offline services mode of “Self-directed learning-Traditional teaching-Collaborative learning”). In the 2018-2019 academic year, Control class group (traditional teaching mode) and experimental class group (STC teaching mode) will be taught for the Advanced Mathematics Teaching of college students of science. We use the score data of the two classes as the evaluation basis. The results show that the STC teaching effect is significant.
Some classes of permutation polynomials with the form (xk
+ x)
s
+ x
2
n
−2
Authors: Yi Shaojun , Zhu Xishun , Wu Jianhua
Published: September 2020

For a prime 2, let n be a positive integer, and F
2
n

be the finite field with 2
n
elements. In this paper, we propose several classes of permutation polynomials with the form (xk
+ x)
s
+ x
2
n
−2 over finite fields F
2
n

which have the highest degree of algebra.
New Farkas-type inequalities of mixed interval systems for AE solvability
Authors: Xia Mengxue , Li Haohao
Published: September 2020

Interval Farkas type inequality is an important tool to prove the optimality condition of interval optimization model. This research gives a Farkas-type inequality for AE solvability of a specific mixed interval linear system including both equality and inequality by using logical quantifiers. Some Farkas-type inequalities for different solvability established in previous literatures are special cases of the main result of this paper.
Research on credit line of supply chain enterprises based on data sharing
Authors: Liu Yue , Hu Jiajing
Published: September 2020

Based on the deficiencies of the existing research on the credit line of supply chain enterprises, this paper taking data sharing as research perspective, established the credit model of supply chain enterprises using data sharing. Through the case study of L Corporation Group, it is found that: 1) the supply chain can integrate information advantages, increase credit line and reduce financing costs; 2) the credit line of supply chain enterprises raises with the increase of data sharing degree; 3) the existing credit models of the banks are conservative, the actual credit line of enterprises is insufficient. The credit model constructed in the paper fully considers the effects of data sharing of related transactions between enterprises on the credit line in the context of supply chain, which can provide ideas for realizing the win-win situation of maximizing the financing scale of supply chain enterprises and minimizing the risk of banks.
A potentially stable and potentially nilpotent tree sign pattern that is not spectrally arbitrary
Authors: Yu Berlin
Published: September 2020

It has been shown that a 4 x 4 tree sign pattern is spectrally arbitrary if and only if it is potentially stable and potentially nilpotent in [M. Arav, F. Hall, Z. Li, K. Kaphle, N. Manzagol, spectrally arbitrary tree sign patterns of order 4, Electron. J. Linear Algebra, 20 (2010), 180-197], where the authors asked whether the above important theorem can be extended to the 5 x 5 case. In this paper, we negatively answer this question by constructing a 5x5 potentially stable and potentially nilpotent tree sign pattern which is shown to be not spectrally arbitrary.
Rumor spreading model considering the influence of public opinion environment
Authors: Pan Qiuhui , Liu Yiling , Lu Siying , He Mingfeng
Published: September 2020

Rumor spreading has a profound influence on daily lives. There are several factors influencing rumor spreading. In this paper, we assume that there are two kinds of individuals in the crowd: those who do not know the rumors and those who learn about the rumors. And in the latter category, there are two attitudes toward rumors: those who are convinced of rumors and those who hold an objective attitude. Those convinced and objective individuals form a public opinion environmental factor conducive to the spread of rumors. Based on the public opinion environmental influence whose intensity decays with time, a model with two attitudes toward rumors is established. With numerical simulations, we illustrated the conversion state of three categories because of public opinion environmental factors, analyzing the sensitivity of the model. The results showed that it is beneficial to control the rumor propagation when controlling the influence of those who are convinced of rumors and those who hold an objective attitude rather than constraining one of them individually. And it was commonsensical that increasing the attenuation intensity of the two attitude rumors was also an effective way conducive to the control.
Inverse Sturm-Liouville problem on three-star graph with a discontinuity
Authors: Lv Kang
Published: September 2020

This paper deals with the inverse Sturm-Liouville problem with one discontinuous point on the three-star graph, suppose the potential is known on all edges except one, the one which has discontinuous point, we deduce the distribution of the eigenvalues, and prove that one spectrum uniquely determines a part of jump information. And by the reasonable assumption, we prove that if all the eigenvalues are simple, then one spectrum uniquely determines the unknown potential, too.
A new solution of thin elastic rod by dynamic analogy
Authors: Zhang Shuai , Zhang Yitong , Wang Peng
Published: September 2020

Inspired by Kirchhoff dynamic analogy, we write the Kirchhoff equation of thin elastic rod in form of curvature expression. Compared it with nonlinear Schrödinger equation, we extend a Jacobi elliptic function analogy solution to elastic rod equation and give a new alternative way to solve the Kirchhoff equation.
Improved Menter’s one-equation turbulence model
Authors: Rahman Md Mizanur , Zhang Yang , Zhu Zefei
Published: September 2020

Compatible modifications to original Menter model (OMM) are incorporated using an elliptic relaxation approach to accurately accounting non-local characteristics accompanied by near-wall turbulence. Coefficients/functions of improved Menter model (IMM) are parameterized with the elliptic relaxation function to imitate the combined effects of near-wall turbulence and non-equilibrium. The characteristic length scale involved in the elliptic relaxation scheme is constructed in terms of viscous and turbulent length scales in conjunction with a non-singular strain-rate invariant. Non-local effects are consequently reinforced by the mean flow and turbulent variables. A non-linear eddy-viscosity damping function is invoked to relax the viscous length-scale coefficient pertaining to the elliptic relaxation model. Comparisons indicate that the IMM substantially improves the accuracy of flow simulations compared to the OMM and widely used Spalart-Allmaras (SA) model. A good consensus is obtained between IMM and DNS (direct numerical simulation)/measured data.
Magnetoencephalogram analysis of depression based on multivariable sign transfer entropy
Authors: Zhang Yu , Zhang Yiling , Chen Junwei , Yan Wei , Chen Zihan , Wang Jun
Published: September 2020

In this paper, multivariable sign transfer entropy algorithm is used to calculate the multivariable sign transfer entropy values of the same brain region and different brain regions stimulated by different emotional images in patients with depression and healthy control group. The connectivity of the magnetic channels in the brain region and between brain regions is studied. And the conclusions of negative cognitive bias in depressed patients [1] and functional asymmetry of emotion of cerebral hemispheres are verified [2]. The results showed that: For different brain regions, the left occipital region →frontal region under positive emotional picture stimulation and neutral emotional picture stimulation can significantly distinguish the depressed patients’ group from the healthy control group, the corresponding connection strength of depressed patients was significantly weaker than that of healthy control group.
Retailer’s optimal procurement plan considering random demand, delayed payment and cash discount
Authors: Huang Ruiqi , Huang Yongbiao , Lu Yueli
Published: September 2020

Many inventory models have been established based on determined demand but ignore the fact that demand can be affected by random factors. A procurement model considering random demand, different trade credit and cash discount is established in this paper. Due to the randomness of demand, possibilities of salvage or stock out at the end of the cycle are considered, and these cases can be dealt as classic news vendor problem. The optimal procurement strategy for the expected profit is derived by some theoretical results in this paper, which are also illustrated by a series of numerical examples and the corresponding sensitivity analyses are also presented.
Influence of order enhancement of the Runge-Kutta method on low-order turbulence statistics of incompressible wall turbulence under a second-order central difference scheme
Authors: Jomura Shotaro , Suzuki Hiroki , Hasegawa Yutaka , Matsuo Shinnosuke , Mochizuki Shinsuke
Published: September 2020

In this study, we attempt to understand the effects of the accuracy order of higher-order Runge-Kutta methods on the turbulence statistics of incompressible wall turbulence. A second-order central difference scheme is used to spatially discretize the governing equations, considering the widely used lower-order spatial discretization. The effects of the difference in the order of the Runge-Kutta scheme are investigated using a turbulent channel flow. The turbulence statistics obtained are compared with those reported in three previous studies. Based on our results, we infer that the rms values of the mean velocity, mean pressure, Reynolds stress, and velocity fluctuation of the turbulent channel flow are not affected by the difference in the accuracy order of the higher-order Runge-Kutta method. The fluctuation of the rms values of static pressure obtained by using the fourth-order Runge-Kutta method were consistent with those obtained in previous studies.
Introduction
Authors: Assmann Ralph , Ferrario Massimo
Published: September 2020

4th European Advanced Accelerators Concepts.

More than 250 scientists from all over the world gathered from Sep 15 – 21 at the 4th European Advanced Accelerator Concept Workshop (EAAC) on the Island of Elba in Italy. Specialists from accelerator physics, RF technology, plasma physics, instrumentation and the laser field discussed ideas and directions towards a new generation of ultra compact and cost effective accelerators with ground-breaking applications in science, medicine and industry.

The EAAC was founded by the European Network for Novel Accelerators (EuroNNAc) in 2013 and has grown in its fourth edition into a meeting with world-wide visibility, rapidly catching up with the long tradition of the Advanced Accelerator Concepts workshop (AAC) in the US. At the EAAC senior scientists from various specialties mix with junior experts and a large community of young students, attracted by the promise and success of compact particle accelerators. In 2019 about 50 PhD students presented their work at the EAAC. Besides the reports on scientific achievements the large diversity in gender, age distribution and nationalities made the EAAC 2019 a special event and a great success for the accelerator field.

Group photo of the EAAC 2019 attendants is present in this pdf.

Committees

List of Workshop Organizing Committee, Programme Committee, International Advisory Committee, Local Organizing Committee and Proceedings Editors are available in this pdf.
Summary of European Advanced Accelerator Workshop (EAAC) Working Group 1: Electron Beams from Plasma
Authors: Corde Sebastien , Irman Arie , Turner Marlene
Published: September 2020

We summarize oral contributions presented in Working Group (WG) 1 of the European Advanced Accelerator Workshop (EAAC). Working Group 1 is titled ’Electron Beams from Plasma’ and included presentations and discussions on the following subjects: laser- and beam-driven plasma wakefield acceleration, recent experimental results and planned experiments, single and multi drive laser pulses (or particle bunches), external and self-injection techniques, staging as well as advanced beam control and manipulation.
Towards experimental investigation of hosing instability mitigation at the PITZ facility
Authors: Loisch G , Gross M , Koschitzki C , Lishilin O , Ossa A Martinez de la , Osterhoff J , Stephan F
Published: September 2020

Beam-driven plasma wakefield acceleration (PWFA) allows for high gradient acceleration of electron beams and hence is a promising candidate for compact and cost-efficient drivers of applications demanding high brightness beams. One of the main challenges in these accelerators is to control beam-plasma instabilities with rapid growth rates which are induced by the strong transverse components of the wakefields. The hosing instability, a growing transverse oscillation of the beam centroid caused by coherent coupling between bunch slice centroids and transverse wakefields, was predicted to set severe limits on the possible acceleration distance in PWFAs. Several methods have been proposed to damp or even suppress the hosing of the beam, prevent beam-breakup and thus allow stable operation. Here, we present preparations and simulation studies aiming at the experimental investigation of hosing suppression mechanisms at the PITZ facility.
Determination of the Charge per Micro-Bunch of a Self-Modulated Proton Bunch using a Streak Camera
Authors: Bachmann A.-M. , Muggli P.
Published: September 2020

The Advanced Wakefield Experiment (AWAKE) develops the first plasma wakefield accelerator with a high-energy proton bunch as driver. The 400 GeV bunch from CERN Super Proton Synchrotron (SPS) propagates through a 10 m long rubidium plasma, ionized by a 4TW laser pulse co-propagating with the proton bunch. The relativistic ionization front seeds a self-modulation process. The seeded self-modulation transforms the bunch into a train of micro-bunches resonantly driving wakefields. We measure the density modulation of the bunch, in time, with a streak camera with picosecond resolution. The observed effect corresponds to alternating focusing and defocusing fields. We present a procedure recovering the charge of the bunch from the experimental streak camera images containing the charge density. These studies are important to determine the charge per micro-bunch along the modulated proton bunch and to understand the wakefields driven by the modulated bunch.
New Tunable High Gradient Permanent Magnet Quadrupole for Plasma Wake Field Acceleration at SPARC _LAB
Authors: Vannozzi A , Alesini D , Sanelli C , Vaccarezza C
Published: September 2020

Applications such as colliders and plasma wake field acceleration require high gradient quadrupoles, in the range of 400-500 T/m and with a bore of few millimeters in diameter.

The design of a tunable high gradient permanent magnet quadrupole (PMQ), based on the QUAPEVA design [1] developed for the SOLEIL synchrotron, is presented. The quadrupole has a fixed part made of a Halbach quadrupole array [3, 4] surrounded by four permanent magnet cylinders with a radial orientation of the magnetic momentum. The gradient is regulated by rotating the cylinders, reaching a tunability greater than the 25%.

The quadrupole has been designed for the COMB plasma wake field beam driven experiment for the SPARC_LAB test-facility at INFN-LNF [2], one of the candidates to host the EuPRAXIA project [7, 8]. The present layout foresees two triplets where the focusing strength tuning is performed by moving two quadrupoles of each triplet along the beam axis. The new quadrupoles have bigger gradient and less multipolar content than actual ones, moreover it has a tuning system that does not need any shift of the magnet.
Design considerations for permanent magnetic quadrupole triplet for matching into laser driven wake field acceleration experiment at SINBAD
Authors: Yamin S , Assmann R W , Dorda U , Lemery F , Marchetti B , Panofski E , Walker P A
Published: September 2020

The ARES (Accelerator Research experiment at SINBAD) Linac at SINBAD (Short and INnovative Bunches and Accelerators at DESY) facility at DESY aims to produce high brightness ultrashort electron bunches (sub fs to few fs) at around 100 MeV, suitable for injection into novel accelerators e.g. dielectric Laser acceleration (DLA) and Laser Driven Wakefield acceleration (LWFA). The external injection experiment planned at ARES aims for stable LWFA by combining the reproducible conventional RF-based accelerator technology, with high-power plasma wakefield dynamics. The LWFA experiment demands Twiss parameter β to be of the order of few mm, in order to avoid emittance growth because of high accelerating gradient in the plasma. The ARES Linac is capable of producing ultra-short bunches at around 100-150 MeV, so the effect of space charge is significantly high. To match such a space charge dominated beam, strong transverse focusing is required. A Permanent Magnetic Quadrupole (PMQ) triplet is one promising focusing strategy. In this paper, we report the technical design constraints and findings for stable settings for PMQ triplet to match the requirements of the electron beam properties and study of phase spaces for final focus into LWFA experiment.
Stability of elliptical self-modulating long proton bunches in plasma wakefields
Authors: Perera A , Muggli P , Welsch C P
Published: September 2020

The AWAKE experiment at CERN recently demonstrated the world’s first acceleration of electrons in a proton-driven plasma wakefield accelerator. Such accelerators show great promise for a new generation of linear e-p colliders using 1-10 GV/m accelerating fields. Efficiently driving a wakefield requires 100-fold self-modulation of the 12cm Super Proton Synchrotron (SPS) proton bunch using a plasma-driven process which must be carefully controlled to saturation. Previous works have modelled this process assuming azimuthal symmetry of the transverse spatial and momentum profiles. In this work, 3D particle-in-cell (PIC) simulations with the code QuickPIC are used to model the self-modulation of non-round bunches. We find that asymmetry in the initial seed wakefield leads to the formation of highly asymmetric microbunches which evolve incoherently along the symmetry axes of the initial bunch profile. However, the resonantly-driven accelerating wakefield is highly stable to both focused and astigmatic non-round bunches.
Simulation of Polarized Beams from Laser-Plasma Accelerators
Authors: Hützen Anna , Thomas Johannes , Lehrach Andreas , Rakitzis T.Peter , Pukhov Alexander , Ji Liangliang , Wu Yitong , Engels Ralf , Büscher Markus
Published: September 2020

The generation of polarized particle beams still relies on conventional particle accelerators, which are typically very large in scale and budget. Concepts based on laser-driven wakefield acceleration have strongly been promoted during the last decades. Despite many advances in the understanding of fundamental physical phenomena, one largely unexplored issue is how the particle spins are influenced by the huge magnetic fields of plasma and, thus, how highly polarized beams can be produced. The realization of laser-plasma based accelerators for polarized beams is now being pursued as a joint effort of groups from Forschungszentrum Jülich (Germany), University of Crete (Greece), and SIOM Shanghai (China) within the ATHENA consortium. As a first step, we have theoretically investigated and identified the mechanisms that influence the beam polarization in laser-plasma accelerators. We then carried out a set of Particle-in-cell simulations on the acceleration of electrons and proton beams from gaseous and foil targets. We could show that intense polarized beams may be produced if pre-polarized gas targets of high density are employed. In these proceedings we further present that the polarization of protons in HT and HCl gas targets is largely conserved during laser wake-field acceleration, even if the proton energies enter the multi-GeV regime. Such polarized sources for electrons, protons, deuterons and 3He ions are now being built in Jülich. Proof-of-principle measurements at the (multi-)petawatt laser facilities PHELIX (GSI Darmstadt) and SULF (Shanghai) are in preparation.
WG3 Summary: Electron beams from electromagnetic structures, including dielectric and photonics structures
Authors: Alesini David , Brinkmann Reinhard
Published: September 2020

This summary provides a brief overview of the presentations and discussions during the sessions of working group 3 at the EAAC2019 workshop.
Analytical energy spectra and wake effects for relativistic dielectric laser accelerators
Authors: Egenolf Thilo , Niedermayer Uwe
Published: September 2020

Dielectric laser acceleration (DLA) is one of the advanced concepts for more compact accelerators. DLA gratings have apertures and period lengths within the range of optical wavelengths. Phase stability and wakefield effects are thus crucial for upcoming experiments with highly relativistic electrons. For this, we present a method to analytically calculate energy spectra for comparison with measurements in order to reconstruct the phase of injection into the DLA grating structure. Knowing the injection phase is important for both alignment and interpretation of measured data. Furthermore, we estimate the effects of wakefields on bunches which are coherently accelerated in a DLA. We are calculating the energy spectrum affected by the longitudinal wake by evaluating the analytical description numerically and give estimates for the transverse kicks of an off-centered injected electron bunch.
Parameter studies on dielectric gratings as electron accelerators
Authors: Kuropka W , Aßmann R , Dorda U , Mayet F
Published: September 2020

Dielectric laser driven particle acceleration (DLA) is one of the candidates for novel high-gradient technologies to reduce the footprint of large scale particle acceleration facilities. On the other hand these devices can be used to interact with the particle beams of state-of-the-art photon science machines, especially with FELs, to manipulate the longitudinal phase space in a compact and cost effective way. The near-field surface modes of dielectric gratings can be used to interact with particle beams close to the surface. To achieve transversely homogeneous accelerating fields two gratings are opposed. The laser can be coupled from the side into the structure. In this work we present a study on the influence of the geometry parameters of the grating on the acceleration gradient and its transverse uniformity. Based on this study a design for production was chosen, which will be used for experiments at the ARES linac within the SINBAD facility at DESY. This work was carried out within the ACHIP project funded by the Gordon and Betty Moore Foundation (GBMF 4744).
Characterization of the Electron Beam in the ACHIP Chamber in SwissFEL
Authors: Ischebeck Rasmus , Bettoni Simona , Borrelli Simona , Calvi Marco , Dijkstal Philipp , Ferrari Eugenio , Guzenko Vitaliy , Hauenstein Dominique , Hermann Benedikt , Hürzeler Orell , Kittel Christoph , Lombosi Csaba , Orlandi Gian Luca , Prat Eduard , Reiche Sven , Rivkin Leonid , Voulot Didier , Zehnder Dominique
Published: September 2020

We have installed an interaction chamber in the electron beam line of SwissFEL. Electrons with a particle energy of 3 GeV are focused to a few-micrometer beam size. Samples placed in this beam can be aligned to the electron beam with a hexapod. The goal of this installation is to demonstrate laser-driven acceleration inside dielectric structures. We present here the layout of this interaction chamber as well as first measurements with the electron beam.
Initial Design of a High-Power Ka-Band Klystron
Authors: Behtouei M. , Faillace L. , Ferrario M. , Spataro B. , Variola A.
Published: September 2020

Accelerating structures operating in Ka-Band are foreseen to achieve gradients around 150 MV/m. Among possible applications of a Ka-Band accelerating structure we refer to the beam phase-space manipulation for the Compact Light XLS project as well and medical and industrial applications. In this paper, a Ka-Band Klystron amplifier is being investigated in order to feed Ka-Band accelerating structures. The initial design is presented including the high-power DC gun and the beam focusing channel.
Simulations of the millimeter wavelength accelerating structure excitation
Authors: Arsentyeva M V , Levichev A E
Published: September 2020

We present the work on development of the millimeter wavelength accelerating structure (also called the W-band structure). It consists of cylindrical cavities with the operating frequency of 96 GHz. The structure will be excited by the picosecond electron beam from the photocathode RF gun. In order to define exactly both the structure and the exciting beam parameters, analytical estimations and simulations of the structure excitation were performed. For the successful propagation of the exciting beam through it, focusing system is needed. It is proposed to use the permanent magnets producing solenoidal field, their preliminary design being discussed. Prototype of the millimeter wavelength structure has been manufactured, its first measurements are presented.
Laser-driven electron storage rings
Authors: Khan S
Published: September 2020

Advanced accelerator concepts usually address linear acceleration schemes. Storage rings, however, are often superior to linear machines regarding repetition rate, stability and efficiency. The radiative energy loss per turn in an electron storage ring is compensated by radiofrequency resonators with a wavelength of the order of 1 meter, which corresponds to the spacing between consecutive potential wells, so-called buckets, and results in a bunch length around 1 centimeter or several 10 picoseconds. As an alternative, longitudinal focusing could be performed by a laser wave co-propagating with the electrons in an undulator. Considering a continuous-wave carbon dioxide laser beam as an example, the bucket spacing would be 10.6 micrometer with a bunch length in the femtosecond range. The paper discusses chances and limitations of such a laser-driven storage ring concept with steady-state femtosecond bunches.
On the resonant properties of the THz metal-dielectric waveguide impedance
Authors: Ivanyan M , Aslyan L , Floettmann K , Lemery F , Tsakanov V
Published: September 2020

Various asymptotic representations for the longitudinal monopole impedance of a two-layer metal-dielectric cylindrical waveguide with finite-conducting external walls and a lossy internal dielectric layer are derived. Areas of their applicability are determined and their properties are investigated. New features for the resonance properties of the structure under consideration are revealed and described.
Injector Design for the MariX-FEL Project
Authors: Faillace L. , Bacci A. , Bosotti A. , Cialdi S. , Drebot I. , Michelato P. , Monaco L. , Petrillo V. , Conti M.Rossetti , Paparella R. , Rossi A.R. , Sertore D. , Serafini L.
Published: September 2020

The MariX project (Multi-disciplinary Advanced Infra-structure for Research with X-rays) is a free electron laser (FEL) light source proposed by the INFN-Milan. It will produce highly coherent X-rays, in the range 0.2-8 keV, with ultra-short pulses (10-50 fs) and a repetition rate up to 1MHz. At the same time, MariX will host a compact monochromatic X-ray source, called BriXS (Bright and compact X-ray Source), by using an inverse-Compton scattering scheme, with energies up to 180 keV and a repetition rate of 100 MHz (continuous-wave CW operation) that will generate fluxes up to 1013 photons per second. In this paper, the Radio-Frequency (RF) and beam dynamics designs of the electron injector for the MariX-FEL project are presented. The choice of the main devices, such as the electron gun and the accelerating linear accelerators, as well as the main parameters for CW operation are discussed in detail.