Equilibrium electron beam parameters of the High Energy Photon Source

Purpose The physics design of the High Energy Photon Source(HEPS)was finished after many times of iteration.Hereby,the typical equilibrium electron beam parameters corresponding to the proposed two baseline operation modes in the baseline design of HEPS are presented.Methods To compute the equilibrium parameters of the electron beam,the lattice parameters,RF parameters,and the parameters of the insertion devices(IDs)were determined first.Furthermore,it is more precise to use the full-current electron beam parameters in the estimations of the performance of the synchrotron light.Therefore,not only the single-particle dynamics but also the current-dependent collective effects need to be considered in the computations of the full-current,equilibrium parameters of the electron beam.Both analytic computations and multi-particle tracking simulations were carried out.Results The full-current,equilibrium parameters of the electron beams in the HEPS storage ring are presented in this paper.Moreover,the main beam parameters in the injector(the booster and the LINAC),corresponding to the two baseline operation modes of the storage ring,are also presented.Conclusion The typical electron beam parameters corresponding to the two baseline operation modes are given in detail in this paper.

Edge Bundling in Information Visualization

The edge, which can encode relational data in graphs and multidimensional data in parallel coordinates plots, is an important visual primitive for encoding data in information visualization research. However, when data become very large, visualizations often suffer from visual clutter as thousands of edges can easily overwhelm the display and obscure underlying patterns. Many edge-bundling techniques have been proposed to reduce visual clutter in visualizations. In this survey, we briefly introduce the visual-clutter problem in visualizations. Thereafter, we review the cost-based, geometry-based, and image-based edge-bundling methods for graphs, parallel coordinates, and flow maps. We then describe the various visualization applications that use edge-bundling techniques and discuss the evaluation studies concerning the effectiveness of edge-bundling methods. An edge-bundling taxonomy is proposed at the end of this survey.

Modification and optimization of the storage ring lattice of the High Energy Photon Source

Purpose For the High Energy Photon Source(HEPS),a green-field fourth-generation storage ring light source,the prelimi-nary design report(PDR)was completed in 2018,when the accelerator physics design had been basically finished.During the subsequent hardware and engineering design of the HEPS storage ring based on the PDR design,a few problems and challenges emerged,calling for modifications of the lattice.Method In this paper,we will introduce the background and reasons for the modifications and present the linear optics and simulation results for the nonlinear performance of the modified lattice of the HEPS storage ring.Result and conclusion The modified lattice satisfies the requirements from hardware and engineering design.

Exploring the design space of immersive urban analytics

Recent years have witnessed the rapid development and wide adoption of immersive head-mounted devices,such as HTC VIVE,Oculus Rift,and Microsoft HoloLens.These immersive devices have the potential to significantly extend the methodology of urban visual analytics by providing critical 3D context information and creating a sense of presence.In this paper,we propose a theoretical model to characterize the visualizations in immersive urban analytics.Furthermore,based on our comprehensive and concise model,we contribute a typology of combination methods of 2D and 3D visualizations that distinguishes between linked views,embedded views,and mixed views.We also propose a supporting guideline to assist users in selecting a proper view under certain circumstances by considering visual geometry and spatial distribution of the 2D and 3D visualizations.Finally,based on existing work,possible future research opportunities are explored and discussed.

MViewer： mobile phone spatiotemporal data viewer

Nowadays movement patterns and people＇s be- havioral models are needed for traffic engineers and city plan- ners. These observations could be used to reason about mobil- ity and its sustainability and to support decision makers with reliable information. The very same knowledge about human diaspora and behavior extracted from these data is also valu- able to the urban planner, so as to localize new services, orga- nize logistics systems and to detect changes as they occur in the movement behavior. Moreover, it is interesting to inves- tigate movement in places like a shopping area or a working district either for commercial purposes or for improving the service quality. These kinds of tracking data are made avail- able by wireless and mobile communication technologies. It is now possible to record and collect a large amount of mobile phone calls in a city. Technologies for object tracking have recently become affordable and reliable and hence we were able to collect mobile phone data from a city in China from January 1, 2008 to December 31, 2008. The large amount of phone call records from mobile operators can be considered as life mates and sensors of persons to inform how many peo- ple are present in any given area and how many are entering or leaving. Each phone call record usually contains the caller and callee IDs, date and time, and the base station where the phone calls are made. As mobile phones are widely used in our daily life, many human behaviors can be revealed by an- alyzing mobile phone data. Through mobile phones, we can learn the information about locations, communications be- tween mobile phone users during their daily lives.In this work, we propose a comprehensive visual analysissystem named as MViewer, Mobile phone spatiotemporal data Viewer, which is the first system to visualize and analyze the population＇s mobility patterns from millions of phone call records. Our system consists of three major components： 1） visual analysis of user groups in a base station; 2） visual anal- ysis of the mobility patterns on different user groups mak- ing phone calls in certain base stations; 3） visual analysis of handoff phone call records. Some well-established visu- alization techniques such as parallel coordinates and pixel- based representations have been integrated into our system. We also develop a novel visualization schemes, Voronoi- diagram-based visual encoding to reveal the unique features of mobile phone data. We have applied our system to real mobile phone datasets that are kindly provided by our project partners and obtained some interesting findings regarding people＇s mobility patterns.

Design and test of support for HEP Smagnets

Purpose High Energy Photon Source(HEPS)has the characteristics of high energy and low emittance,which requires that the 1st natural frequency of the magnet support assembly should be better than 54 Hz and the moving resolution of girder should be less than 5μm.The prototypes have been designed and fabricated to meet the requirements.Methods In the design process of the support system model,double-wedge adjusting mechanism and concrete plinth construction are adopted to meet the requirements of adjusting resolution and stability.The FEA and the dynamic stiffness testing technique are used to verify the rationality of the design model.The stability and motion performance tests are performed to verify that the prototype meets the design requirements.Results Experimental results showthat,in all cases,the lowest first-order natural frequency of the support system is 55Hz,the amplification between magnet and ground is less than 1.05 in the directions perpendicular to the beam,the moving resolution can reach 1μm,and the girder can be locked in place with an error of less than 5μm.Conclusion The prototype of HEPS support system meets the requirements of stability and motion performance.The girder body and wedge mechanism made with iron or steel have little influence on the stability of the support system.The accuracy of dynamic stiffness test and finite element simulation results is verified.Further test will be performed in the HEPS site to verify the performance.

Mechanical design of the horizontal collimator for HEPS storage ring

Background Horizontal collimators in the storage ring of high energy photon source(HEPS)are used to localize the majority of the particle loss,making it possible to set local shields.Moreover,movable jaws of the collimators are also designed as beam dumps for the machine protection,to absorb and scatter the mis-steered beam.Because of the compact lattice,each collimator should be installed between the limited space of 240 mm in the beam direction.It is necessary for the collimators to have good thermal dissipation ability to endure the synchrotron radiation and HOM load,as well as good resistance to thermal-shock from sudden beam loss simultaneously,which brings great challenges to the design.Purpose The purpose of this paper is to introduce the designing scheme of the collimators in HEPS,including the structure design and the analyses of the key components.Method Thermal and mechanical calculation has been done,based on which the jaw structure has been optimized.Besides,the modal analysis of the whole magnet-collimator-support assembly has been studied to optimize the shields structure.Result Graphite will be used as the tip for movable jaws in the collimators,which is attached to copper by vacuum brazing.The maximum temperature of the jaw during normal operation is 131°C,while maximum stress of the graphite–copper weld joint is 15.6 MPa.Graphite tip can resist thermal shock caused by whole mis-steered beam.Eigen frequency of the standard assembly is acceptable for HEPS.Conclusion The results of calculations indicate that the present structure can work well for considered operating modes.

VISTopic:A visual analytics system for making sense of large document collections using hierarchical topic modeling

Effective analysis of large text collections remains a challenging problem given the growing volume of available text data.Recently,text mining techniques have been rapidly developed for automatically extracting key information from massive text data.Topic modeling,as one of the novel techniques that extracts a thematic structure from documents,is widely used to generate text summarization and foster an overall understanding of the corpus content.Although powerful,this technique may not be directly applicable for general analytics scenarios since the topics and topic-document relationship are often presented probabilistically in models.Moreover,information that plays an important role in knowledge discovery,for example,times and authors,is hardly reflected in topic modeling for comprehensive analysis.In this paper,we address this issue by presenting a visual analytics system,VISTopic,to help users make sense of large document collections based on topic modeling.VISTopic first extracts a set of hierarchical topics using a novel hierarchical latent tree model(HLTM)(Liu et al.,2014).In specific,a topic view accounting for the model features is designed for overall understanding and interactive exploration of the topic organization.To leverage multi-perspective information for visual analytics,VISTopic further provides an evolution view to reveal the trend of topics and a document view to show details of topical documents.Three case studies based on the dataset of IEEE VIS conference demonstrate the effectiveness of our system in gaining insights from large document collections.

Design and test of the motion system for HEPS storage ring horizontal collimator

Background Collimators in the storage ring of high-energy photon source(HEPS)are used to localize the beam loss,making it possible to set local radiation shields.The motion system of the collimator is used to adjust the position of the movable jaws for controlling the beam loss precisely.Moreover,dump mode of the collimator increases the risk of jaw damage from beam heat deposition.According to the requirements of motion accuracy and the severe working condition of the collimators,a new design of a two-axis motion system for the movable jaws is proposed,realizing high-precision control and extending the lifetime.Purpose The purpose of this paper is to introduce the designing scheme of the motion system for HEPS storage ring horizontal collimators,including the analyses of the key components,the structure design of the motion system and test results of the prototype.Method Temperature excursions of the movable jaw are calculated theoretically and analyzed by ANSYS,respectively.The motion accuracy of the system is measured by coordinate measuring machine.Result The temperature excursion is simulated as 1883 K while using graphite as the absorbing material at dump mode.The motion system consists of a mobile slide for aperture adjustment and a manual wedge jack for vertical adjustment.The average coupled deviation in horizontal direction of the wedge jack is 0.031 mm,while the maximum positioning deviation of the slide is 0.014 mm,both having good repeatability and being compensable.Conclusion Test results of the prototype indicate that the new design of the motion system is applicable to the horizontal collimator in HEPS storage ring.The problem of the jaw rotation in the horizontal movement is found,and the solution is given.

Mechanical design of an ultra-light vertex detector prototype for CEPC

Background The Circular Electron Positron Collider(CEPC)is a large international scientific facility proposed to study the Higgs boson in great detail.It requires state-of-the-art detectors,including extremely precise vertexing and tracking devices,such as a silicon vertex detector.Purpose Silicon vertex detector with the precision required by the CEPC has never been built before and needs extensive research and development.This paper describes the mechanical design of a vertex detector prototype being built to explore the required technologies and the major challenges.Methods The exceptional high spatial resolution of the CEPC vertex detector is achievable only with a detector of extremely low mass to limit particle scattering.This paper proposes a mechanical design for the vertex detector prototype,highlighting the choice of low-mass materials,the analysis of support structures,the solution of detector cooling issues,and the drafts of procedures for detector assembly.Results The ultra-light support of the ladder(a structural unit of the CEPC vertex detector prototype),which is mainly made of carbon fiber reinforced polymer composite,has been designed.The fabrication process has also been verified.Global supporting and cooling method of the vertex detector prototype has been designed and chosen with results from finite element analysis and computational fluid dynamics simulations.Complete assembly and installation schemes for the prototype have been developed,and the respective tooling has also been designed.The performance of the vertex detector prototype,using this low-mass mechanical structure,was demonstrated with fast simulation to closely meet the CEPC physics requirement.

Study of themovable collimator for CEPC

Background Movable collimators for the circular electron positron collider(CEPC)are required to cut off spent electrons/positrons just near the beam orbit and reduce the background of the detector.Due to the extremely high energy and luminosity of CEPC,a lot of challenges are brought to the collimators,including the huge synchrotron radiation power,the high-energy beam impact,and low impedance requirement.Purpose The purpose of this paper is to design a movable collimator suitable for CEPC and calculate its performance.Method Based on geant4 simulations and finite element method(FEM)analyses,a lot of studies were done:synchrotron radiation power,thermal and mechanical calculation,beam impact,and impedance,respectively.Result The maximum temperature of the design during normal operation is 143℃,and the loss factor is only 0.021 V/pC ignoring the shielding of clearance.Conclusions The conceptual design of collimator was completed,and the calculations show the design can work well under normal operating condition.

Tax-Scheduler:An interactive visualization system for staff shifting and scheduling at tax authorities

Given a large number of applications and complex processing procedures,how to efficiently shift and schedule tax officers to provide good services to taxpayers is now receiving more attention from tax authorities.The availability of historical application data makes it possible for tax managers to shift and schedule staff with data support,but it is unclear how to properly leverage the historical data.To investigate the problem,this study adopts a user-centered design approach.We first collect user requirements by conducting interviews with tax managers and characterize their requirements of shifting and scheduling into time series prediction and resource scheduling problems.Then,we propose Tax-Scheduler,an interactive visualization system with a time-series prediction algorithm and genetic algorithm to support staff shifting and scheduling in the tax scenarios.To evaluate the effectiveness of the system and understand how non-technical tax managers react to the system with advanced algorithms and visualizations,we conduct user interviews with tax managers and distill several implications for future system design.

Spatio-temporal flow maps for visualizing movement and contact patterns

The advanced telecom technologies and massive volumes of intelligent mobile phone users have yielded a huge amount of real-time data of people’s all-in-one telecommunication records,which we call telco big data.With telco data and the domain knowledge of an urban city,we are now able to analyze the movement and contact patterns of humans in an unprecedented scale.Flow map is widely used to display the movements of humans from one single source to multiple destinations by representing locations as nodes and movements as edges.However,it fails the task of visualizing both movement and contact data.In addition,analysts often need to compare and examine the patterns side by side,and do various quantitative analysis.In this work,we propose a novel spatio-temporal flow map layout to visualize when and where people from different locations move into the same places and make contact.We also propose integrating the spatiotemporal flow maps into existing spatiotemporal visualization techniques to form a suite of techniques for visualizing the movement and contact patterns.We report a potential application the proposed techniques can be applied to.The results show that our design and techniques properly unveil hidden information,while analysis can be achieved efficiently.