Signal Crosstalk Suppression of Multi-node Micro-pocket Fission Detector

For a long time, the micro-neutron detector, which is capable of withstanding the nuclear reactor core environment, has been a research hotspot in related fields. The micro-pocket fission detector (MPFD), which was proposed Kansas State University, is fabricated with microalumina ceramic substrates which are capable of withstanding high temperature and high flux environment. The size of the substrates is only in millimeter scale. This micro-size allows multiple MPFDs to be assembled into an array of detectors to facilitate 3-D mapping of a reactor core neutron flux profile in real-time. For the multi-node MPFD constructed of parallel wire electrodes and substrates, every readout electrode is near each other due to its small size. When the detector structure design is unreasonable, certain signal crosstalk will occur between nodes, that is, the charged particle emitted in one node will often generate similar signals not only on the readout electrode of this node, but also on the corresponding electrodes of other nodes in the MPFD. The crosstalk may cause the fission counting rate of the detector exceed the fission frequency (pulse mode) or current amplitude of the detector distort (current mode and MSV mode), thus decreasing the accuracy of the neutron flux measured by MPFD. Therefore, whether the crosstalk can be reduced is an important index to evaluate the performance of this multinode MPFD detector. The amplitude of crosstalk signal is affected by the structure of the detector. Numerical simulation on the polarity and pulse amplitude of crosstalk signal can provide theoretical guidance for the design of MPFD detector. In this work, a 3-node MPFD design was proposed. Garfiled, SRIM and finite element analysis method were used to simulate and analyze crosstalk signals between different MPFD nodes. The results show that crosstalk signal is one order of magnitude lower than main signal, and the polarity is opposite. At the same time, a 3-node MPFD detector prototype was made. Crosstalk signal generated by α particle emitted from the uranium coating was tested experimentally. The experimental results are consistent with the simulation results, which shows that crosstalk signal between different nodes in this 3-node MPFD can be distinguished by signal polarity and pulse amplitude, so it will not affect the measurement of neutron flux.