Background:The fission ionization chamber is constituted by235U and238U materials as monitor in China Spallation Neutron Source (CSNS) reverse angle.Purpose: This paper mainly introduces the whole system time precision influence on the energy resolution and the actual measurement corrections.Method: The flux energy spectrum is measured accurately using n-TOF method. Results: The time resolution which is caused by energy resolution is proportional to 3/2 power energy, and the correction is induced less than 0.1% due to differences of the standard cross section energy.Conclusion:The experimental results show that the design of the ionization chamber can meet the requirements of CSNS neutron flux measurements.%将235U与238U两种材料组成的裂变电离室作为散裂中子源反角方向束流监视系统应用的探测器，采用飞行时间方法可以高精度地测量束流的能谱。本文主要介绍整个系统的时间分辨精度对能量分辨的影响以及实际测量中的修正因素，时间分辨引起的能量分辨与能量的3/2幂成正比，能量分辨引起与标准截面的能量差异的修正小于0.1%，实验结果表明该项裂变电离室的设计能满足散裂反角中子能谱测量的要求。
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