The Research On Bipolar Transistor Detector's Technology For 1MeV Equivalent Neutron Fluence

When the bipolar transistor irradiated by neutron,it's DC gain will decline,the reciprocal of DC gain has a linear relation with the neutron flux.The performance of bipolar transistor with radiation damaged after neutron irradiation could be recovered by high temperature annealing.In view of the above characteristics,making the bipolar transistor as a detector,combined with real-time data measurement system,then,it can preliminarily realize monitoring neutron flux online.In the field of application of anti-nuclear reinforcement,assessment of neutron radiation damage in semiconductor materials requires a uniform standard of measurement,the equivalent neutron fluence of 1MeV?Si?has been used to characterize it both at home and abroad.Existing detectors on the market can measure neutron fluence,but it will be influenced by neutron spectrum and reaction cross section.When the bipolar transistor detector is irradiated by neutron,the DC gain will decrease.In the radiation source with different energy spectrum distribution,the same DC gain degradation can be used as the equivalent.The CFBR-? reactor of the China Academy of Engineering Physics is a simulated radiation field of nuclear explosion with a high N/?ratio and a neutron energy of 1.03MeV.It is an ideal platform for checking the performance of anti-nuclear reinforcement and is also an ideal calibration platform for bipolar transistor detectors.The calibrated bipolar transistor detector is used in different radiation fields on this platform,and the neutron flux measured is 1MeV equivalent neutron flux.The detector is small in size and can be used for simultaneous on-line measurement of multiple detectors at different radiation positions in different radiation fields,which is of universal and practical value.Zou Dehui and Lu Yi of the Chinese Academy of Engineering Physics have carried out preliminary studies on the radiation resistance,calibration technology and annealing of bipolar transistor 3DG121C detectors.On this basis,this paper expands the research scope of this kind of detectors.By irradiating the 3DK2222A and 3CK3B detectors in the CFBR-? reactor with up to 8.3×10¹²neutron flux,the selection of the neutron radiation resistance of the detectors is realized,and the optimum range of application of the detectors is determined.The suitable type of detector can be selected for the measurement of different neutron fields.3DK2222A and 3DG121C detector is studied in ⁶⁰Co source.When?dose reaches 1000Gy,the characteristics of two kinds of detectors are analyzed,and the application of this characteristic is determined.For the effect of different neutron flux rates on this kind of detectors,the3CK3B type detectors were selected under the conditions of 2×10⁷cm^-2·s^-1N 6×10⁷cm^-22 s^-1N 2×10⁸cm^-22 s^-1N 6×10⁸cm^-22 s^-1N 2×10⁹cm^-22 s^-1,respectively.The effect of different flux rates on the detectors and the different beams were analyzed.Annealing characteristics of the detector at the rate of measurement.Based on the characteristics of reusing and annealing of detectors,the shortcomings of the original annealing techniques are analyzed,and the structure of the detectors is improved.The improved structure design takes into account the accuracy of the detector calibration and the convenience of annealing.As the?-ray in neutron field will cause ionizing radiation damage to bipolar transistor detector,like neutron,it will lead to the degradation of DC gain of detector.The DC gain degradation caused by?-rays will be superimposed on the DC gain degradation caused by neutrons,so that the neutron flux measured by the detector is higher than the actual neutron flux.For3DG121C and 3DThe radiation law of K7E detector in?-ray is analyzed,and the empirical formula of the detector during?-ray irradiation is deduced.Combined with the principle of neutron flux measurement,the correction formula of neutron flux measurement can be determined when using this kind of detector in neutron field with n/?ratio.Through the research of the bipolar transistor neutron flux detector in this paper,the 1MeV equivalent neutron flux detection technology is more perfect,which provides theoretical support for the spread and practical application of the detector.It also has the guidance and the reference significance to the later development research of the detector.