Commissioning And Performance Testing For Long Trace Profiler System

With the continuous improvement of synchrotron radiation source performance,the requirements for the synchrotron radiation beamline have also increased in recent years.The main function of the beam line is to transmit beam,split the synchrotron radiation light into monochromatic light,focus.The large synchrotron radiation mirror is the key element to realize the focus of the synchrotron radiation,and the surface shape of the mirror directly affects the focused spot size of the beam line.The grating is the core splitting element of the vacuum ultraviolet-soft X-ray monochromator,and the density deviation of the grating will affect the performance of the monochromator,thereby affecting the performance of the beam line.Therefore,the development of high-precision surface shape and grating line density detection technology is crucial in the pre-research of Hefei Advanced Light Source,and the long trace profiler(LTP)is the main equipment for detecting the surface of synchrotron radiation optical components.Based on the pre-research of Hefei Advanced Light Source,this paper builds an LTP system and tests its performance.The main works are shown as follows:1.According to the principle of LTP measurement of reflector surface shape and the principle of measuring grating density,an LTP system is built,which has the ability to detect the surface shape of optical mirrors and the density of grating.Analyze the random error,drift error and system error of LTP,and give the corresponding suppression or correction methods.2.The autocollimator is used to calibrate the optical head of the LTP measuring mirror module and the measuring grating module.The results showed that within±13μrad,the deviation between the two and the autocollimator was 29nrad(RMS)and 30nrad(RMS).The performance of the LTP measurement mirror module is tested.The test results show that the system has a measurement repeatability of 37.5nrad(RMS)within a range of 1.14m,a plane measurement accuracy of 49.7nrad(RMS)within±13μrad,and a curved surface measurement accuracy(self-test)of 89nrad(RMS)within ±1.6mrad,which basically meets the system design indicators.3.The 2400L/mm and 760L/mm synchrotron radiation uniform line spacing gratings independently developed in the pre-research of Hefei Advanced Light Source are tested for linear density uniformity by using LTP,the measurement repeatability is △N/N=1.81×10-7(RMS)and △N/N=5.76×10-7(RMS).An interferometer is used to detect the wavefront of the first diffraction and the zeroth diffraction of the 760L/mm grating,and the results are compared with those measured by LTP,the results showed that the deviation of the height profile between the LTP and the interferometer was 0.79 nm(RMS)in the zeroth diffraction and 1.50nm(RMS)in the first diffraction,it shows that the built LTP system has a higher precision ability to detect the density of grating.The limitation of the LTP measurement grating module is analyzed,and the linear density change in a single scan cannot exceed 50L/mm.The test results show that the built LTP system has both the high-precision detection capabilities of tthe linear density of gratings and the surface of mirrors,which provides a technical reserve for the detection of optical components of the beam line of Hefei Advanced Light Source in the future.