Research On Beam-profile Measurement System Based On Synchrotron Radiation

Relativistic charged particles will move along a curved trajectory under the action of an external magnetic field,thus producing synchrotron radiation(SR).Due to its excellent properties such as high brightness,synchrotron radiation is one of the powerful tools to study material properties in many different fields such as molecular and atomic physics,cell biology,medical applications,nanotechnology and catalysis.An important performance index to measure the electron storage ring light source is the transverse beam size,and accurate measurement of the beam size can directly reflect the light source brightness.Therefore,each light source must have a matching transverse beam diagnostic system to monitor the transverse beam size in real time.As the storage ring SR source gradually approaches the fourth generation diffraction limit storage ring source,its beam size will reach the order of microns,and its emittance will also reach the level of pm·rad,which undoubtedly poses a challenge to the accurate measurement of the transverse beam size.On the HLS-Ⅱ light source,due to the large beam size and the intensity of radiation spectrum is strong enough in the visible band,the visible band is used as a cost-effective means of detection light at present.Therefore,we carried out a study on beam size diagnositic based on the visible imaging measurement system and the visible twodimensional interferometer measurement system on the HLS-Ⅱ light source.Considering the defects of the optical path adjustment,high cost and zoom structure in the visible light two-slit interferometer measurement system,a two-dimensional SR interferometer measurement system is developed for the HLS-Ⅱ light source,which can simultaneously measure the horizontal and vertical beam size with only one optical path.Using the two-dimensional SR interferometer system,the horizontal and vertical beam size of B7 source points are(291.94±1.56)μm and(241.30±0.69)μm,respectively,and the corresponding visibility are 0.638±0.003 and 0.579±0.002,which meet the design indexes of the SR interferometer.After that,we further analyzed the error of the twodimensional SR interferometer measurement system,and the experimental measurement error was less than 3%,which well met the current requirements for the measurement of the beam size of the HLS-Ⅱ.Based on the developed two-dimensional SR interferometer,we have carried out a series of beam experiments.Firstly,the visibility of interference fringes is effectively regulated by changing the spacing of holes.In the experiment,three groups of different spacing are selected to build interferometers with different parameters.The measurement results verify the feasibility and practicability of the proposed twodimensional SR interferometer to measure the transverse beam size.Secondly,the current intensity dependence experiment,short-term stability experiment and low current intensity experiment are carried out by using the established interferometer.In a short time,the measurement results of this system are not only stable,but also can accurately measure the change of beam size with the current intensity.Especially,the beam oscillation and instability are observed under the condition of low current intensity.These experiments further demonstrate the reliability of the developed twodimensional SR interferometer,which can meet the needs of diagnostic beamline.Finally,the horizontal emittance and energy dispersion are measured by the system combined with the B8 imaging measurement system,which provides a powerful monitoring tool for the study of the physical mechanism related to the beam current in the storage ring.For HALF light source,the transverse beam size is in the order of micron.For such a small beam size,it is difficult to use the traditional visible light imaging system and visible light interferometer to achieve accurate measurement.The former is the diffraction effect of light wave reduces the system resolution,and the latter it is difficult to design an interferometer with proper visibility due to the small light source size.Therefore,we calculated the radiation intensity distribution and spectral distribution of HALF of the source points to be measured by SRW software,and determined to choose the X-ray imaging system scheme to measure the beam size.Therefore,we calculated the radiation intensity distribution and spectral distribution of HALF of the source points to be measured by SRW software,and determined to choose the X-ray imaging system scheme to measure the beam size.According to the X-ray optical characteristics and the spatial layout of HALF the diagnostic beamlines,two sets of beam size measurement systems are designed in this paper.One is a amplification imaging system using two compound refractive lens groups,and the other is a amplification imaging system using two Fresnel Zone plates.The numerical simulation results show that both designs can meet the measurement requirements and provide some reference value for the development of HALF beam size measurement system.