Applied To The X-ray Photon Counting Of Pulsars Navigation Detector And Its Key Technology Research

Currently, X-ray pulsar-based autonomous navigation (XNAV) becomes aresearch focus in navigation field. One of the core components of XNAV system isX-ray photon counting detector. The sensitivity and time resolution are two keytechnical specifications of X-ray photon counting detector for XNAV, because the fluxof pulsar radiation is very faint and the positioning precision depends on the precisionof measurement on pulse TOA (time of arrival).A MCP-based X-ray photon counting detector and X-ray imager are proposedbased on analysis of theory of XNAV and comparison of different X-ray detector’sworking principle and performance, and a prototype is developed. The photoncounting detector is composed of input window, photocathode (CsI), serpentinemicro-strip line anode and electronic readout system. As for X-ray imager, thedifference is the anode substituted with wedge and strip anode which is a positionsensitive anode.X-ray pulsar-based navigation simulation system is set up, which is composed ofX-ray pulse resource, X-ray photon counting detector, electronic readout and dataprocessing unit. The X-ray resource can produce single photon radiation, and theX-ray resource’s period can be tuned between1.5ms and300ms. The TOA ofindividual photon be recorded by the X-ray counting detector, and considerable dataof photon TOA can be recorded through the detector works long enough. At last,X-ray pulse profile can be reconstructed according to pulsar pulse profile foldingmethod. Once the pulse profile is reconstructed, we can calculate the pulse TOA andverify the pulsar navigation algorithm.High sensitive CsI photocathode detector and high time-resolution serpentinemicro-strip line anode are developed. The sensitivity of the detector is tested, andthe result show integral sensitivity of reflective photocathode which thickness is800nm is highest, and can reach260A/W/cm~2, and the spectral sensitivity at0.25nm is460A/W/cm~2. The NEP (noise equivalent power) of the MCP-based X-ray photoncounting detector is also tested and compared with AXUV100G Si PN detector. Theresults indicate that the NEP of MCP-based detector is5.4×10-16W/cm~2, andcorresponding photon number density is0.68ph/s/cm~2, but for AXUV100G, the NEPis3.2×10-13W/cm~2and corresponding photon number density is403ph/s/cm~2, so thecapability of detection of weak light of MCP-based detector is far better thanAXUV100G.. The time performance of the MCP-based detector is also analyzed, thehigher voltage applied on photocathode and anode, the better time resolution is get.The best time resolution of detector is1.1ns in our experiment. Additional, we test thedead time of whole detection system, and the dead time is100ns which originprincipally from the dead time of TDC circuit. So the time resolution of wholedetection system is100ns.The pulse profile acquiring experiment is carried out on the X-ray pulsar-basednavigation simulation system, and the result show that the better waveform,the highertime resolution, the higher gain voltage and the higher sensitivity of the detector, thehigher SNR of pulse profile can be get. The X-ray pulse profile can be reconstructedusing MCP-based detector when the photon number density of X-ray is0.067ph/s/cm~2which is greatly less than the NEP of the detector, this result show that the pulseprofile can be get when the photon number density is about10-5ph/s/cm~2if theintegratal time is long enough.The X-ray photon counting imaging experiment is also carried out, and theresult show the spatial resolution of the X-ray imager is better than150μm.In order to improve the SNR of integral pulse profile, a cubic spline smoothingalgorithm and HARR wavelet de-noise algorithm are proposed. Experiment resultsshow those algorithm can improve the SNR of the pulse profile. In the wavelet field,we modify the pulse TOA algorithm which is proposed by Taylor, and the precision ofthe measurement of TOA is improved.