Air kerma conventional true value measuring method

An air kerma conventional true value measuring method, comprising the following steps:

• step 1, establishing a small-scale reference radiation field, the small-scale reference radiation field comprises a shielding box comprising a side length not more than 1.5 meters, the shielding box being positioned horizontally and an incident hole being provided on a side thereof for incidence of incident rays, a check point being arranged in a direction of the incident rays in the shielding box, the shielding box being further provided with a test hole on an upper surface through which a probe of an instrument to be detected can be put into the shielding box, a reference point on the probe being superposed with the check point, a dose feature point being also arranged in the shielding box, the shielding box being segmented into two parts by one plane perpendicular to a connecting line of the incident hole and the check point and containing the check point, the dose feature point being located at a part close to the incident hole in the shielding box and at a position not directly irradiated by the incident rays, a gamma spectrometer being arranged in the shielding box, a reference point on a probe thereof being superposed with the dose feature point and the probe being fixed in the shielding box;
• step 2, selecting a proper radiation source and source strength to provide incident rays for the shielding box;
• step 3, selecting a plurality of gamma ray dose measurement instruments as experimental samples for constructing a prediction model to obtain the prediction model of the air kerma conventional true value at the check point;
• and
• step 4, putting the probe of the instrument to be detected at the check point, recording scattering gamma spectra measured by the gamma spectrometer, and introducing the scattering gamma spectra to the prediction model to obtain an air kerma conventional true value.