【摘要】 裂变瞬发中子谱(Prompt Fission Neutron Spectrum,PFNS)是重要的核反应数据,为了测量低于源中子能量的裂变瞬发中子谱,通常是用中子探测器与平行板雪崩计数器(Parallel Plate Avalanche Counters,PPAC)进行符合测量以扣除非裂变事例的影响。针对裂变瞬发中子谱测量的需求,研制了一个由10个单元组成的PPAC。用Maxwell软件模拟了相同尺寸及工作条件下丝状电极电离室和平板电极电离室的电场分布。对该PPAC的结构及其性能测试进行了详细介绍。该PPAC工作于低气压流气模式,每个单元可以独立工作。该PPAC测试的结果为相邻两个PPAC单元之间的时间符合谱半高宽(Full Width at Half Maximum,FWHM)为620 ps,PPAC与液体闪烁体探测器的时间符合谱γ峰的半高宽为880 ps。测试结果表明:该PPAC的时间响应快,达到预期指标,适合用于高事例率情况下的时间符合测量。更多还原

【Abstract】 Background]The prompt fission neutron spectrum （PFNS） is an important nuclear reaction data.Coincident measurement between neutron detectors and parallel plate avalanche counters （PPAC） is widely used to measure the PFNS below the energy of the neutron source,hence most of the non-fission neutrons can be exclude.[Purpose]This study aims to develop a PPAC to satisfy the PFNS measurement and performance test.[Methods]First of all,a ten-cell PPAC was designed with low-pressure flow working gas and individual cell functionality.Then the software named"Garfield"was used to simulate the distributions of electric field of two kind of fission chambers,i.e.,wire-electrode chamber and plate-electrode chamber,under the same geometric dimensions and working conditions.Finally,the structure and the performance of the PPAC were introduced in detail,and relevant performance of this PPAC was tested by experiment.[Results]The full width at half maximum （FWHM） of the timecorrelated spectrum between two neighbor cells using a²⁴¹Amαsource is 620 ps.The FWHM of the time-correlated spectrum between a PPAC cell and a liquid scintillator detector is 880 ps using a²⁵²Cf fission source.[Conclusions]The experiment confirms that the time resolution of the designed PPAC is good enough for high event rate measurements.更多还原