Optimization Of The Detection System Based On Neutron Sensitive Microchannel Plate

The microchannel plate detector has good spatial resolution and time resolution,which is suitable for high precision imaging.Neutron can penetrate high density material,but for some light elements,the absorption rate is high,which can make up for the insufficient that X-rays can image light material.The neutron sensitive microchannel plate detector combines the advantages of the microchannel plate detector and neutron imaging,and enables high-resolution imaging of light materials.The signal readout electrodes of the microchannel plate are WSA electrode,delay line electrode and Medipix electrode.Because the delay line electrode has better spatial resolution,time resolution and lower cost,then the delay line is used as the readout electrode of the ⁿMCP detector,with the large area microchannel which the diameter is 106 mm and doped with 3mol%^natGd₂O₃ has been studied.Microchannel plate detector is a detector in high vacuum environment.The microchannel plate and readout electrode are placed in the vacuum chamber.And it needs to connect the ion pump to maintain the vacuum.Therefore,the overall quality of the detector is heavy and the installation and debugging is inconvenient.The mechanism of the neutron sensitive microchannel plate is to multiply the electrons generated by the incident neutron under the strong field produced by high DC voltage.The multiplier coefficient is affected by the working voltage.In general,two microchannel plates are assembled in the V stack,the high voltage is added to the series microchannel plates,and the single microchannel plate is unevenly allocated.Uneven voltage distribution makes the overall multiplication factor of the stack lower.In most cases,the beam lines emitted by the ray source are not absolutely parallel.If the distance between the measured object and microchannel plate is far,the imaging will be blurred,the detector has a distance of more than 5cm between the measured object and the incident surface of the microchannel plate,because of the limitation of the working condition of the vacuum.So the geometric imprecision of the imaging is worse.At the view of the above problems,this paper puts forward corresponding improvement plan.The quality of the vacuum chamber of the detector is reduced by the simplified structure design.The ceramic clamping ring and the voltage of the microchannel plate are redesigned.The working voltage of each microchannel plate can be controlled independently.The installation of the microchannel plate and the vacuum chamber is more compact,the distance between the object and ⁿMCP is reduced to less than 2cm,and the quadrilateral delay line electrode is successfully wound.The results are evaluated by X-ray imaging,reactor cold neutron beam imaging and photoneutron beam experiment.The USAF 1951 resolution mask with gadolinium is used as an imaging object,and the spatial resolution of the detector is evaluated.The results show that the improved neutron sensitive microchannel plate detector has good resolution.The spatial resolution of 250?m can be achieved by using the hybrid neutron beam of wavelength 2?and 4?.