The Lobster Eye Imager for Astronomy Onboard the SATech-01 Satellite

The Lobster Eye Imager for Astronomy(LEIA),a pathfinder of the Wide-field X-ray Telescope of the Einstein Probe mission,was successfully launched onboard the SATech-01 satellite of the Chinese Academy of Sciences on2022 July 27.In this paper,we introduce the design and on-ground test results of the LEIA instrument.Using stateof-the-art Micro-Pore Optics(MPO),a wide field of view of 346 square degrees(18.6°×18.6°)of the X-ray imager is realized.An optical assembly composed of 36 MPO chips is used to focus incident X-ray photons,and four large-format complementary metal-oxide semiconductor(CMOS)sensors,each of size 6 cm×6 cm,are used as the focal plane detectors.The instrument has an angular resolution of 4’-8’(in terms of FWHM)for the central focal spot of the point-spread function,and an effective area of 2-3 cm^(2) at 1 keV in essentially all the directions within the field of view.The detection passband is 0.5-4 keV in soft X-rays and the sensitivity is2-3×10^(-11) erg s^(-1) cm^(-2)(about 1 milliCrab)with a 1000 s observation.The total weight of LEIA is 56 kg and the power is 85 W.The satellite,with a design lifetime of 2 yr,operates in a Sun-synchronous orbit of 500 km with an orbital period of 95 minutes.LEIA is paving the way for future missions by verifying in flight the technologies of both novel focusing imaging optics and CMOS sensors for X-ray observation,and by optimizing the working setups of the instrumental parameters.In addition,LEIA is able to carry out scientific observations to find new transients and to monitor known sources in the soft X-ray band,albeit with limited useful observing time available.

Corrigendum to “High-temperature fatigue strength of grain boundaries with different misorientations in nickel-based superalloy bicrystals” [Journal of Materials Science & Technology, 154 (2023) 94–106]

The authors regret to inform that the whole“Acknowledgements”section is missing due to the composing process of the editing.The“Acknowledgements”information that should be added is as follows.

A practical model for efficient anti-fatigue design and selection of metallic materials:Ⅰ.Model building and fatigue strength prediction

The high cost and low efficiency of fatigue tests are bottleneck problem for the anti-fatigue design of metallic materials.For this problem,a theoretical fatigue model is proposed in this study,the possible applications have also been discussed.Specific results would be introduced in two serial papers,in which the first paper focuses on the model building and the applications on fatigue strength prediction;the second paper put emphasis on the influencing factors of the model parameters and the applications on fatigue strength improvement.In this first paper,a theoretical model is proposed considering both the strength and plastic restrictions of fatigue strength.As the model builds up a brief relationship among yield strength(Y),tensile strength(T)and fatigue strength(F),it is named as the Y-T-F model.Through the verification with fatigue strength data covering various kinds of metallic materials and loading conditions,this Y-T-F model exhibits both generality and accuracy.With the Y-T-F model,the efficient fatigue strength prediction could be conducted by brief linear fitting and calculation,just through yield strength,tensile strength and several known fatigue strength data.Moreover,through its deduced Y-F model,the analytical formula of fatigue strength continuously changing with materials strengthening can be obtained,as well as the maximum value of fatigue strength and corresponding critical yield strength.In summary,the Y-T-F model would be useful for reducing the fatigue tests,thus providing new possibilities on the efficient anti-fatigue design and selection of metallic materials.

Recent progresses on designing and manufacturing of bulk refractory alloys with high performances based on controlling interfaces

Refractory alloys such as tungsten and molybdenum based alloys with high strength,thermal/electrical conductivity,low coefficient of thermal expansion and excellent creep resistances are highly desirable for applications in nuclear facilities,critical components in aerospace and defense components.However,the serious embrittlement limits the engineering usability of some refractory alloys.A lot of research results indicate that the performances of refractory alloys are closely related to the physical/chemical status,such as the interface dimension,interface type,interface composition of their grain boundaries(GBs),phase boundaries(PBs)and other interface features.This paper reviewed the recent progress of simulations and experiments on interface design strategies that achieve high performance refractory alloys.These strategies include GB interface purifying/strengthening,PB interface strengthening and PB/GB synergistic strengthening.Great details are provided on the design/fabrication strategy such as GB interface controlling,PB interface controlling and synergistic control of multi-scaled interfaces.The corresponding performances such as the mechanical property,thermal conductivity,thermal load resistance,thermal stability,irradiation resistance,and oxidation resistance are reviewed in the aspect to the effect of interfaces.In addition,the relationships between these interfaces and material properties are discussed.Finally,future developments and potential new research directions for refractory alloys are proposed.

A practical model for efficient anti-fatigue design and selection of metallic materials:Ⅱ.Parameter analysis and fatigue strength improvement

In the first paper,a Y-T-F model was proposed based on the restrictions of both strength and plasticity;the corresponding applications on the fatigue strength prediction have also been discussed.In this second paper,the emphasis will be put on the issues of fatigue strength improvement.Based on the primary form of the Y-T-F model,the parameters are further analyzed and quantified,to clarify the influences of various factors on fatigue strength.Firstly,the damage capacity C is proved to be sensitive to the elastic modulus E,which could change with the alloying components and nano-scaled grain boundaries;the increase of E would lead to the increasing C,thus increase the fatigue strength.Secondly,the microstructure characteristic coefficient a,as well as the yield strengthσ_(y) and tensile strengthσ_(b) in the crack initiation region could be influenced by the processing mode,grain size and microstructure uniformity of materials;the change of microstructure characteristics would affect the changing tendency of tensile strength--fatigue strength relation via varying the values of a,σ_(y) andσ_(b).Thirdly,the damage weight coefficientωis found to be a reflection of the fatigue strength declination induced by defects;the defect dimension D,the defect shape correlated stress concentration coefficient Kt,as well as the strengthening level of matrix materialsσ_(b) are all corresponding factors.Quantified correlations between the above parameters and corresponding factors are comprehensively built up,hence obtaining the influences of either a single factor or multiple factors on fatigue strength.This further developed Y-T-F model would be helpful to clarify the direction of fatigue strength improvement,and contribute to the anti-fatigue design optimization of metallic materials.

Predicting the variation of stacking fault energy for binary Cu alloys by first-principles calculations

The variation of stacking fault energy(SFE)in a number of binary Cu alloys is predicted through considering the Suzuki segregation by the full potential linearly augmented plane wave(FPLAPW)method.The calculated results show that some solute atoms(Mg,Al,Si,Zn,Ga,Ge,Cd,Sn,and Pb),which prefer to form the Suzuki segregation,may decrease the value of SFE;while the others(Ti,Mn,Fe,Ni,Zr,Ag,and Au),which do not cause the Suzuki segregation may not decrease the SFE.Furthermore,it is interesting to find that the former alloying elements are located on the right of Cu group while the latter on the left of Cu group in the periodic table of elements.The intrinsic reasons for the new findings can be traced down to the valences electronic structure of solute and Cu atoms,i.e.,the similarity of valence electronic structure between solute and Cu atoms increases the value of SFE,while the difference decreases the value of SFE.

High-temperature fatigue strength of grain boundaries with different misorientations in nickel-based superalloy bicrystals

Nickel-based single-crystal superalloys are widely used in the manufacture of aeroengine turbine vanes for their excellent high-temperature performance. Low-angle grain boundaries (LAGBs) will be generated inevitably during their manufacture, which are often characterized by grain boundary misorientation (GBM) and will weaken the mechanical properties of superalloys. However, the relationship between GBM and the fatigue properties of superalloys at elevated temperatures has seldom been investigated due to the difficulty in the sample preparation and experiment process. Based on six kinds of bicrystals with different tilt LAGBs made by a second-generation single-crystal superalloy, the effects of misorientation on the grain boundary microstructure and fatigue properties (980 °C) of superalloys were studied systematically in this work. It is found that, with the increase of GBM, the GB precipitates combined with the cast micropores increase monotonically, accordingly both the fatigue life and fatigue strength decrease successively. Fatigue fracture observations show that the cracks of all the bicrystals initiated from the cast micropores at GBs, and then propagated along the GBs. Therefore, the coupling effect of cast micropores and GBM on the fatigue damage mechanisms of the bicrystals are evaluated according to their hindering degrees on the piled-up dislocations. Combining with a hysteresis energy model, a quantitative fatigue strength prediction model of superalloys is established and is well verified by abundant experimental data. This study could provide guidance for fatigue performance prediction and structural design of superalloys.

MTCA.4-based LLRF control system for the C-ADS proton Linac injector I

Objective:The Chinese ADS proton Linac injector I composed of an electron cyclotron resonance ion source,a lowenergy beam transport line,a radio frequency quadrupole(RFQ)accelerator,a medium-energy beam transport(MEBT)line,a superconducting section and beam dump with design goal to achieve CW proton beam with beam current 10 mA and energy gain around 10 MeV.In order to maintain the stability of the RF system,to compensate for the beam load effect and to provide the GUI required for the operation of the RF power system,we have established a LLRF control system.Methods:This LLRF system for ADS proton Linac injector I in IHEP consists of RF reference system and LLRF controllers for oneRFQcavity,twoMEBTbunching cavities and 14 superconductive spoke cavities.We have adopted a new development mTCA.4-based hardware platform,and it has some characteristics such as faster bandwidth,standardized design,easy operation and maintenance and good expansibility.Results:The LLRF system has been improved and optimized and has now been put into operation.It takes into account the pulse and CW beam flow mode,feedforward and feedback control functions.Conclusion:With the help of this system,we achieved stable operationwith narrowpulses,long pulses,andCWmodes under different beam loads.This article describes the implementation of this system and presents some initial the CW beam acceleration results with the help of this system at the end of 2016.