最新刊期
卷 0 ， 期 0 ， 2020
- 摘要：Background:The shaking of micro-focus spot in the vertical direction is found during the energy scan experiments,such as XAFS scan.The beam position of vertical direction changes obviously with the energy.Purpose: In order to make the beam position shaking amplitude less than 1/10 of the beam size.Methods:The beam position stability of SSRF BL15U beamline is improved by using beam intensity feedback.The feedback system include beam intensity monitor of the beamline and fine adjust mechanism of pitch2（the pitch angle of the second crystal of the double crystal monochromator）.The feedback control of the beam position is realized by adjusting the pitch2 to fix beam intensity at its maximum value.Results:The test results show that the vertical beam vibration below 10 Hz frequency is significantly reduced and also the beam position stability during photon energy scan is improved by more than 5 times.Conclusions:By adopting the new feedback systems,the stability of the beam spot on the specimen stage was dramatically improved which achieved the anticipated target.关键词：Synchrotron radiation;Beam position stability;DCM;Beam intensity feedback
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发布时间：2021-03-05 - 摘要：Background:Aiming at precise beam position measurement of next generation FEL facility,Shanghai institute of applied physics developed 5712 MHz high Q CBPM prototype.Purpose:ADC bits and data length of data acquisition system are key parameters influencing spatial resolution of CBPM.In order to find the optimized configuration parameters,dedicated beam experiments and corresponding Monte Carlo simulations were used to solve the problems.Methods:The position calibration factors of CBPM prototype have been obtained through beam based calibration experiment at the Shanghai deep ultraviolet FEL facility.The dependence between system spatial resolution and ADC bits and the data length have been simulated with the measured position calibration factors by using Monte Carlo method.Results:Equipped with 14bits or better ADCs IF sampling technique is capable to achieve submicron position resolution,which is the optimal choice for CBPM on-line data acquisition system. Applying FFT signal processing algorithm,optimal data lengths in RF and IF sampling techniques were respectively 8192 and 256 points.Conclusions:RF sampling technique is hard to accomplish precise measurement of submicron level due to limited bits of present ultra- high-speed ADC,but suitable for plug & play prototype parameter test and evaluation.关键词：CBPM;Beam experiment;FFT;Parameter simulation
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发布时间：2021-03-05 - 摘要：Background:Free electron laser(FEL) has developed several high gain work modes,including high gain harmonic generation(HGHG),echo-enabled harmonic generation(EEHG),cascade HGHG,etc.Such modes have special advantages but all need external seed laser to modulate the electron beam.Purpose:To carry out such experiments at Shanghai Deep-Ultraviolet Free Electron Laser test facility(SDUV-FEL),a new seed laser system has been established.Methods:The system is consisting of Ti:sapphire laser,optic parameter amplifier(OPA),laser transport line and synchronize measurement system.Results:By such system,wide variation rang of seed laser wavelength(1140-2600 nm) and sub-picosecond level synchronization between seed laser and electron beam have been achieved.Conclusions:We have succeeded carry out HGHG and EEHG experiments at SDUV-FEL and the results show that the seed laser could effectively modulate electron beam.关键词：Free electron laser;Seed laser;Transmission;Injection;Modulate
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发布时间：2021-03-05 - 摘要：Background:It is challenging to realize very small beta function and dispersion free colliding region in a limited space.Purpose:Tiny electron beam sizes are required to achieve high flux in ultra-short and intense laser-electron campton scattering facilities.Methods:Beam characteristics for different matching conditions are studied with the presence of various alignment and field errors.Results:Beta function of laser-electron beam spot can be up to 0.01 meter and the dispersion function is zero at the same time.The optimization calculations of some main factors including magnetic field error and mechanical installation error are also performed.Conclusions:A mini-beta scheme with the achromatic treatment can be found to meet the experimental requirements.关键词：Beam optics matching;Mini-beta scheme;Compton scattering
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发布时间：2021-03-05 - 摘要：Background:The optical system controlling of Shanghai Deep Ultraviolet Free-Electron Laser (SDUV-FEL) is based on EPICS system framework.It contains hardware and software to realize the functions like optical path control,beam quality measurement and so on.Purpose:Some improvements are needed so as to facilitate the operation and the safety of the maintenance and repair.All parts of this system should be integrated to the EPICS framework.Methods:We have made following improvements:integration of Basler CCD to EPICS,new OPI,controlling system of stepper motor through serial network.Results:All basic functions of the CCD and motor control are realized,meanwhile,all the optical systems are under the control of EPICS,which meet the need for FEL experiments.Conclusions:This work will make further enhance simplicity and integration of the optical system, which will become more reliable,easily operated and maintained.关键词：Optical system control;SDUV-FEL;EPICS
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发布时间：2021-03-05 - 摘要：Background:For a long time,many scholars both at home and abroad have been engaged in radon monitoring for seismic forecast.Purpose:This paper deals with the relationship between uniaxial stress and rock radon exhalation,and wants to provide the basis of earthquake prediction by using the change of radon concentration. Methods:The uniaxial force applied on the granite sample is carried out using rock triaxial creep testing machine. The total accumulative measurement for sample radon emanation under different uniaxial pressure is performed using CR-39 solid track detector.Results:When the sample in the initial consolidation and elastic deformation stage,the radon emanation quantity with decreased the increase of the pressure.Granite samples’ biggest axial displacement positively correlated to the uniaxial tension applied on them.With the development of time,the "native" fissure of sample is compressed tighter by degrees,lead to the smaller amounts of radon exhalation in fracture.Conclusions: This article provides some experimental reference for the negative anomalies circumstances of radon before earthquake.关键词：Uniaxial pressure;Granite;Radon consistence;Solid track detector
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发布时间：2021-03-05 - 摘要：Background:The direct current power supply is one of the most important subsystems of heavy ion research facility in Lanzhou(HIRFL),and the accuracy of control parameters has significant influence on power supply status judgment and beam tuning effect.Purpose:To optimize the control parameters which can secure the power supply’s read value is consistent with set value,the fundamental process of power supply’s consistency calibration is introduced in this paper.Methods:The principle of linear transformation is used to derive control parameters’ formulas,and a calibration program which based on LabVIEW is designed.Results:The program gets power supply’s operation data through dynamic data exchange technique;then it calculates optimized control parameters.Conclusions:Both real calibration and simulation result indicate that the used method is correct,and the optimized control parameters can fulfill the accuracy requirement of power supply’s consistency calibration.关键词：Heavy ion research facility in Lanzhou;Direct current power supply;Consistency calibration;LabVIEW;Dynamic data exchange
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发布时间：2021-03-05 - 摘要：Background:Target temperature has an important effect on the target life for the sealed neutron generator without cooling system.Purpose:To carry out the thermal-mechanical coupling analysis of the film-substrate target bombarded by the pulsed ion beam.Methods:The indirect coupling Finite Element Method(FEM) with a 2-dimensional time-space Gaussian axisymmetric power density as heat source was used to simulate the target temperature and thermal stress fields.Results:The effects of the target temperature and thermal stress fields under difference pulse widths and beam sizes were analyzed in terms of the FEM results.Conclusions:Combining with the temperature requirement and the thermal stress inducing film thermal mechanical destruction effect of the sealed neutron generator film-substrate targets,an optimized pulsed ion beam work status was proposed.关键词：Neutron generator;Pulsed ion beam;Finite element method;Temperature and thermal stress coupled fields
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发布时间：2021-03-05 - 摘要：Background:After crossing the transition energy,the momentum dispersion of the beam increases,and its quality is degraded.Purpose:Considering the 2-order nonlinearity of the phase slip factor,the RF noise and the synchrotron radiation damping,the synchrotron motion equation of the particle in the synchrotron is reduced to the 3-order nonlinear differential equation with a damping term and a forced term in the classical mechanics frame and small amplitude approximation.Methods:Analysed the phase plane properties and the amplitude response of the system by the numerical method;discussed the stability and the motion behavior of the particle in the vicinity of the 1/3 resonance by the perturbed method.Results:Derived the jumping phenomena and the critical condition for the system.Conclusions:The greater zero-order phase shift factor and the smaller the third-order nonlienearity,the more stable the system becomes.关键词：Synchrotron motion;Phase slip factor;Transition energy;Multi-scale method;Stability
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发布时间：2021-03-05 - 摘要：Background:Hastelloy N alloys are selected as the structural materials of molten salt reactor(MSR). Few results have been reported about their microstructures after irradiation.Purpose:To investigate the microstructural evolution of Hastelloy N induced by irradiation.Methods:Samples were irradiated at 500℃with 30 keV He ions to different doses.Then the microstructures were characterized by scanning electron microscope(SEM) and transmission electron microscopy(TEM).Results:Surface blisters were observed in all bulk samples.Black dot defects emerged in TEM sample irradiated at low dose(0.124 dpa).As the dose increased,dislocation loops and He bubbles were observed and the density of black dots decreased.When the dose got to 1.24 dpa,both the sizes and density of dislocation loops and He bubbles increased remarkably.Conclusions:Black dot defects,dislocation loops and He bubbles are induced by He~+ irradiation at high temperature,the densities and sizes of which are related to the irradiation doses.Accumulation of He bubbles will result in blisters of alloys.关键词：Hastelloy N;Surface blisters;He bubbles;TEM;Black dots;Dislocation loops
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发布时间：2021-03-05 - 摘要：Background:Accelerate grid for producing several tens of MW ion beams is a critical component of the megawatt level high current ion source for the high power neutral beam injection.Purpose:To measure and analyze the position of accelerate grid.Methods:Taking the exit grid module of EAST-NBI high current ion source as the measurement object,the observation point coordinates of accelerate grid rail’s actual axis are obtained by using 3 quadrantel points sampling method and the point coordinates are analyzed by using MATLAB optimal function. Results:The position error that tallies with minimum zone and the distribution regularities of accelerate grid rails are obtained.Conclusions:This method has simple and stable course of evaluating,can realize automatic measurement and provide the basis for improving and finalizing the grid module’s processing technic.关键词：High current ion source;Accelerate grids;Position;Minimum zone;MATLAB
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发布时间：2021-03-05 - 摘要：Background:Dose calculation plays a key role in treatment planning for radiotherapy,its performance and accuracy are crucial to the quality of treatment plans.Differential convolution/superposition algorithm is considered as an accurate algorithm for photon dose calculation;however,improvement on its computational efficiency is still desirable for such purpose as real time treatment planning.Purpose:The goal of this work is to boost the performance of differential convolution/superposition algorithm by devising a graphics processing unit (GPU) implementation so as to make the method practical for daily usage.Methods:In this work,we implemented a GPU-based version of the differential convolution/superposition algorithm,by which the most time-consuming parts are implemented on GPU.In order to fully utilize the GPU computing power,the algorithm is modified to match the GPU hardware architecture.Results:Compared with the algorithm completely running on CPU,the GPU-based algorithm can speed up 30-60 times on a Tesla C1060 with higher values corresponding to larger field size.Finally, we use y index to analyze the accuracy of calculation results,no matter one field or multi-field,homogeneous phantom or inhomogeneous phantom,the GPU implementation has the same accuracy as the CPU implementation. Conclusions:GPU is a useful solution for satisfying the increasing demands on computation speed and accuracy of dose calculation.The GPU-based differential convolution/superposition can be feasible and cost-efficient for satisfying the increasing demands for either computation speed or accuracy by advanced radiation therapy technologies.关键词：CUDA;Differential convolution/superposition algorithm;GPU;Dose calculation
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发布时间：2021-03-05 - 摘要：Background:In recent years,adsorption of radioactive xenon by activated carbon has been increasingly applied to the treatment of off-gas in nuclear power project.Though pore structure of activated carbon has a great impact on its dynamic adsorption coefficients for xenon,the concerned research is rare.Purpose:It is very necessary to figure out the relationship between the pore structure and the dynamic adsorption coefficients for the purpose of the selection and development of activated carbon.Methods:In this study,the dynamic adsorption coefficients of xenon on four kinds of activated carbons were measured on a dynamic adsorption platform under the condition of 25℃, OMPa（gauge pressure）.And these four kinds of activated carbons were characterized by nitrogen adsorption and SEM.Results:The results show that the activated carbon of JH12-16 with the specific surface area of 991.9 m2·g-1 has the largest xenon dynamic adsorption coefficient among these activated carbons.Conclusions:The dynamic adsorption coefficient of xenon on activated carbon doesn’t increase with the specific surface area or the pore volume. The mesopore and macropore only play the role of passageway for xenon adsorption.The most suitable pore for xenon adsorption is the pore with the pore size ranged from 0.55 to 0.6 nm.关键词：Activated carbon;Xenon;Pore structure;Microtopography
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发布时间：2021-03-05 - 摘要：Background:The accuracy and real-time performance of pulse amplitude extraction in digital nuclear spectrometer system directly influence the system energy resolution and the maximum count rates.Purpose:This paper attempts to study the amplitude extraction method of digital nuclear signal,which comes from the high speed ADC.Methods:In this paper,according to the principle of operation,the extraction method is categorized into three types:direct comparison method,curve fitting method and filter shaper method,also the operating principle of the three methods are analysed and discussed.Results:The above three methods are employed to process actual sampled digital nuclear signal at the sampling frequency of 40 MHz,the curve fitting method and filter shaper method are respectively used to extract the pulse amplitude and get their energy spectrum.Conclusions:Taking into account the resolution and pulse counting rate,after theoretical analysis,experimental comparison and test,the optimal pulse amplitude extraction method is filter shaper method.关键词：Digital nuclear spectrometer;Pulse amplitude extraction;Direct comparison method;Curve fitting method;Filter shaper method
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发布时间：2021-03-05 - 摘要：Background:Core shroud is an important assembly,which forms the lateral periphery of the core inside the core barrel.Purpose:To carry out a dynamic property test on a core shroud mockup(1:1) at the damping,natural frequency and the corresponding vibration mode of AP1000 reactor internal core shroud assembly in air.Methods: The multi-input multi-output(MIMO) test method was used in this modal test.Results:By such test,the first six mode natural frequencies,damping and vibration modes of the core shroud assembly were obtained.Conclusions: The test results would be used to offer natural parameters of the core shroud assembly for AP 1000 reactor equipment system model and flow-induce vibration analysis of the core shroud assembly.关键词：Core shroud assembly;Modal test;Dynamic property
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