Fast neutron tomography has been established as an inspection and detection tool at the NECTAR facility at the FRM-II reactor.Scattered neutrons from the object become a major disturbance and bring in artifacts and deviations in reconstruction results,especially for hydrogenous material object.In this article,an iterative scattering correction method for fast neutron tomography was proposed.In each loop of iteration the scattering component of the projections will be simulated by Monte-Carlo program MCNPX based on the previous reconstruction result and then it will be subtracted from original projections.The differences between scattering components at different perspectives were quantitatively evaluated and an average scattering component image was used for all projections finally.Smooth and uniform slices with more clear edges were obtained and the new reconstructed attenuation coefficients are quite close to the real one compared to the results without scattering correction,in which case the relative error of the reconstructed attenuation coefficients is about 10%–30%.
LIU ShuQuanBCHERL ThomasZOU YuBinWANG ShengLU YuanRongGUO ZhiYu
A mini-vane four-rod radio frequency quadruple (RFQ) accelerator has been built for neutron imaging. The RFQ will operate at 201.5 MHz, and its length is 2.7 m. The original electric field distribution along the electrodes is not flat. The resonant frequency needs to be tuned to the operating value. And the frequency needs to be compensated for temperature change during high power RF test and beam test. As tuning such a RFQ is difficult, plate tuners and stick tuners are designed. This paper will present the tuners design, the tuning procedure, and the RF properties of the RFQ.
QuanFeng Zhou (1) Kun Zhu (1) ZhiYu Guo (1) MingLei Kang (1) ShuLi Gao (1) YuanRong Lu (1) JiaEr Chen (1)
本文采用涂布法制备了一系列H310BO3/ZnS(Ag)闪烁体转换屏样品,对其成分配比进行了优化。结果表明,最佳的H310BO3/ZnS(Ag)质量比在1∶6～1∶7之间,最佳的黏合剂用量为总质量的25%。利用中子照相设备对转换屏的发光均匀性进行了成像分析,结果显示光输出非常均匀;对楔形镉条进行中子成像,并采用调制传递函数(modulation transfer function,MTF)方法计算了系统分辨率,结果显示,在MTF值为0.1时,对于厚度分别为270(11)、350(14)、404(9)及505(15)μm的转换屏,其相应的系统空间分辨率分别为255.6、315.9、371.0和471.3μm。
