Development Of Data Acquisition System For TOF-SIMS

Time of Flight Secondary Ion Mass Spectroscopy(TOF-SIMS)combines the advantages of SIMS and time of flight mass analyser(TOF).It is an important surface analyzing method which can be used in analyzing solid sample directly with almost no loss of sample,quick analysis,wide mass range and high resolution.Now,TOF-SIMS has been widely used in many fields such as bioscience,materialogy,geology and even space science.Data acquisition and processing system is an important part of TOF-SIMS instrument which is used for collecting the signal from MCP and provides a mass spectrum for the mass spectrometry of the sample.To meet the requirement from “The TOF-SIMS instrument applied to isotopic geochronology”,with the analysis of the feature of signal from MCP,this paper has finished the overall design of data acquisition system and listed the main design indices including the range of time measurement(>340 ?s),the time resolution(<60 ns),the speed of tranfering data to PC(>200MB/s)and etc.This paper use a date acquisition technique based on time-to-digital conversions in the development of TOF-SIMS data acquisition and processing system.The hardware of system includes the timing discriminator&level translator module,the time-to-digital conversion module,the PCIE BUS module.Their control sequence is provided by the CU based on FPGA.TOF-SIMS data acquisition and processing system is connected to PC by PCIE BUS.TOF-SIMS data acquisition and processing system gains the time imfromation of signal from MCP by timing discriminator.It acquire the time of ion flying in TOF by TDC.The data is transferred to PC by PCIE conector.The drivers of data acquisition and processing system is developed based on WDM,and the data processing will be done by Matlab.Finally,it draws a image of the count of ion(y-axis)along the time of ion flying in TOF(x-axis)as TOF-SIMS mass spectrum which is showed in Matlab GUI interface.TOF-SIMS data acquisition and processing system can be proved that it has met the the requirement from TOF-SIMS instrument by the test of main design indices.Finally,it has been used in the TOF-SIMS instrument applied to isotopic geochronology for analyzing Zirconium Silicate.