The Application Of PSD Position Measuring System In Undulator Magnetic Field Measurement

The significance of this subject is that we can carry on research in high precision magnetic field measurement in enclosed spaces of the undulator, especially in-vacuum undulator. PSD(Position Sensitive Detector) bases on the lateral(x and y direction) photoelectric effect. It can directly detect the position of spot energy center, which can be used to obtain the lateral coordinates of Hall probe.Firstly, we introduce the current situation of PSD applications to undulator magnetic field measurement at home and abroad, including Spring-8 in Japan, ESRF in Europe, NSRRC in Taiwan. Secondly, we carry on theoretical analysis on operating principle of two-dimensional PSD. Work out an operational formula that converts the voltage signal into coordinate. We get the conclusion that the displacement of optical spot exhibits linear relationship with voltage signal on photosensitive surface. Thirdly, we describe how PSD position measuring system works, mechanical design and debugging process in details. Use Solid Edge to design scaffolds of two stepping motors and iris, pedestals of PSD and Hall probe. NI Motion Devices PCI-7340 DAQ Card in NI MAX can be used to drive stepping motors. Voltages can be collected by four Keithley2701 digital voltmeters with equidistant firing control in 0.5mm. Compile data acquisition program with LabVIEW to obtain voltage signal and output into a spreadsheet. At last, we import the data after calculation into MATLAB and make fitting curve with sample points. Through the fitting results, we found that PSD position measuring system accurately reflect the lateral position of guide rail.In this experiment, we construct a PSD position measuring system applied to undulator magnetic field measurement to achieve on-flying measure successfully. With the measurement of guide-ways straightness, the lateral coordinates of Hall probe can be obtained fast and accurately. Several experiments indicate that the positioning accuracy of this system can be reached 5μm and meet the requirements of magnetic field measurement of the undulator.