Beamline Intelligent Commission System Based On Differential Evolution Algorithm

In the synchrotron radiation light source,the stable performance of the beam line is the basic premise for improving the operating efficiency of the beamline and ensuring the correct and effective experimental data.However,light source point changes caused by restarting the facility after maintenance every winter and summer vacation,insert adjustment during machine operation,ambient temperature fluctuations,ground vibration,etc.,as well as thermal deformation of optical components,even switching of different experimental methods,etc.,all require readjusting the beam line state in order to obtain the experimental spot with stable position,high flux and good shape that meets the user's requirements.Due to the huge beamline structure and many types of equipment,the traditional manual beamline adjustment mode requires experienced engineers to adjust their positions for each motor within its range in turn until the experimental spot meets the requirements,and the beam adjustment time is usually several hours or even longer.So beamline adjustment is a tedious task that is performed frequently and takes time and effort.The structure of the beamline is complex,and the reasons that affect the stability of the performance are irregular.It is difficult to establish a beamline model using mathematical formulas.In this paper,based on the differential evolution algorithm,the global space search method is adopted,and after the competition mechanisms such as crossover,mutation,and selection,and the principle of "survival of the fittest",the intelligent beam optimization system for beamline optimization has the advantages such as fast convergence,good reliability,high efficiency,etc.According to the characteristics of the synchrotron radiation beamline,the positions of all the motors to be optimized at the same time are combined into an individual.The predetermined motor motion range is used as the search space.And the luminous flux measured by the ionization chamber is used as the fitness(feedback result)to establish a beam optimization model.Based on the universal EPICS control platform of SSRF,the LabVIEW program is used to realize the intelligent optimized beamline adjustment system,including the design of human-computer interaction interface,acquisition of ionization chamber signals,execution of differential evolution algorithm,and sending of control commands.The system can freely select the motor to be optimized according to the characteristics of the beamline station,set the corresponding search space,set the algorithm parameters such as individual size,cross probability between individuals,mutation factor,etc.,and track the evolution progress and evolution effect in real time during the optimization process.It has the characteristics of good expansibility,rich and flexible functions,and easy operation.This system was tested online at the SSRF X-ray Diffraction Beamline.The dualcrystal monochromator DCM and the rear focusing mirror M2,which play a decisive role in stabilizing the beamline performance,are selected as the optimized objects.The test results show that the system can automatically search within the set search range,accurately find and converge to the optimal solution.The system convergence time is directly related to the repeatability of the motor.If he motor repeatability is good,the system convergence is fast,and the time it takes is short.If the motor repeatability is slightly worse,the system convergence speed becomes slower,and the time it takes increases.Some good individuals will fail when passed on to the next generation.The system convergence time does not increase proportionally with the increase of the number of motors because the system controls the motors and all the motor motion search processes are synchronized.The more the number of motors,the more effectively it shows.When a total of 7 motors for DCM and M2 is selected for optimization,the system convergence time takes about 30 minutes.Compared with the manual beam adjustment process,this system greatly improves the beamline adjustment efficiency.