Development And Experimental Method Of The GEM-based Fission Time Projection Chamber

Nuclear fission reaction has already been widely used in military,energy and other fields,and the researches on it is till continuing.The precise detection of fission fragment tracks is still a knotty issue due to the limits of traditional measurement methods.The detection technique combining with the Gas Electron Multiplier（GEM）and the Time Projection Chamber（TPC）can provide conditions for multi-parameter correlation measurement of fission fragments.The work of this paper is the development and experimental method of the GEM-based fission time projection chamber（FTPC）.FTPC is constituted of three parts:the automatic pressure controlling system for providing stable working gas environment;the GEM-based FTPC for obtaining the nuclear information of fission fragments;and the readout and data processing system containing 1664 channels.The FTPC is designed to work in low-pressure environment,which purposes are to lengthen the fission fragment tracks and reduce the space stack of data points,to obtain more accurate information of the position and energy.However,the current research on the working properties of gas detectors in low-pressure environment is not comprehensiveness.Therefore,⁵⁵Fe source is used to test the characteristics of FTPC at different air pressure.When the pressure decreases,the voltage range of FTPC continues to drop.And it’s energy resolution becomes better first,and reaches the best point at 17%,when the working pressure is about 300 m Bar.After that the energy resolution deteriorates rapidly.When the working state remains unchanged,the reduced electric field intensity of GEM does not remain constant as expected,but increases.In order to eliminate the systematic error caused by the difference of discharging velocity between readout circuits,a time correction method is proposed:separating the exponential part,and obtaining the original Gaussian signal.The data processing in this paper is based on this method.The performance of FTPC was tested using an ²⁴¹Amαsource.2D and 3D tracks ofα articles have been rebuilt,and the spatial resolution of FTPC in the X-Y plane is 511.1μm and in Z-axis is 610.2μm.SRIM was used to simulate the energy loss ofαparticles in P10gas at 850 m Bar and 550 m Bar.The signals were used to calibrate the energy loss of FTPC.At present,the testing experiments and data processing methods of the FTPC have been completed.The detector is in a good condition and has the ability to detect the fission fragments.