A Bonner sphere spectrometer(BSS) was developed for neutron diagnostic on HL_2A Tokamak.It contains eight polyethylene spheres embedded with SP9~3 He proportional counter.Before setting up on the Tokamak experimental hall,a verification experiment was arranged on a^(241)Am–Be neutron source to test its spectrometry capability.The neutron response functions were calculated by Monte Carlo code Geant4 to simulate the real measurement environments.By least square method,the neutron spectrum was finally unfolded on log domain from0.1 e V to 11 Me V.It has a remarkable consistency to the ISO 8529-1 standard^(241)Am–Be neutron spectrum.This shows that the BSS is effective and reliable for neutron spectrum determination.
针对滤波器非理想特性等因素带来的信道化失真对信号侦察的影响,为实现信号参数高精度估计以及波形的准确恢复,提出了基于基追踪算法的宽带LFM信号信道化侦察方法。该方法以l1范数稀疏正则最小二乘模型为目标函数,推导了问题的二阶锥规划(Second order cone programming,SOCP)形式,将各子带输出信号在过完备Gabor原子字典上展开,完成对原信号准确的参数估计与分解重构。仿真实验证明,该方法实现了对信号准确的时频分析与参数估计,通过稀疏原子(较小数据量)准确重构了原宽带信号,并在一定程度上减小信道化失真的影响。
To meet the needs of signal alignment between the transmitter and receiver in a quantum key distribution(QKD) system, we put forward a TDC-GPX-based synchronization scheme, which is based on high-precision time measurement. We send a low-frequency repeat optical pulse synchronized with associated quantum signals on the receiver's side by using a time-to-digital converter(TDC)module, the time intervals between quantum signals, and synchronization signals measured and converted to corresponding temporal orders to complete the synchronization.We state the principle of the synchronization scheme in detail and then verify it in an actual QKD test bed. The test results show that our TDC-GPX-based synchronization can obtain a time resolution better than 100 ps, and the proposed scheme shows full feasibility for an actual QKD system.
