The Establishment And Study Of Reference Radiation Field In The Range Of (20-300)kV X-rays

Establishing an reference radiation field of the X-rays,which isaccurate and reliable, is the basis to achieve national air kerma datum traceabled and transfered. Achieving X-ray radiationwork be implemented safely, X-rays equipment must be QC, which requires various types of X-ray dose meter calibrated to ensure its value of dose' unity and used in accuracy.Based on The establishment and study of reference radiation field in the range of(20-300)k V X-rays,.firstly,to establish a reference radiation device, including X-ray units, monitor ionization chamber, aperture, shutter, radiation quality filtration system, four-dimensional space motion platform, three-dimensional laser positioning device and 4m rail and so on.Using the two-dimensional matrix detector sweep field to achieve the three-axis collimation by radiation beam, laser and rail; using finger-type ionization chamber sweep field point by point, measured at 1m distance focus, uniformity better than 99% of the radiation field diameter greater than 9cm, meeting dose meter calibration condition.Using non-intrusive Ray Safe X2 detector measures the tube voltage of industrial X-ray units, expanded uncertainty of less than 0.78%(k = 2), the ripple is less than 10%. According to the requirements of establishment of reference radiation quality, by the half-value layer fitting, established four series of reference radiation qualities,diagnosis(RQR and RQA) treatment(CCRI recommended low-energy and medium energy radiation qualities), protection(narrowspectral and wide spectral) and the environment(narrow spectral), a total of 41. Wherein, relative deviation of the first half-value layer between measurementsvalues and recommended values were less than 5%, the second half-value layer, in addition to N-40 and N-100 is slightly larger, the remaining meeting the requirements.The effective energy were calculated by the segment fitting method.To simulated the filter X-ray spectrum, modeling the industrial X-ray unitsby Monte Carlo software EGSnrc, to calculate the simulation spectrum distribution corresponding to the radiation quality.Calculated the average energy and spectral resolution, wherein the average energy with a narrow spectrum of ISO recommended values differ by less than 5%(in addition to N-20), spectral resolution less than 10%. Four pulse amplitude spectrum of the radiation qualities N-15, N-20, N-25 and N-30 were measuredby Si-Li detector.After normalization, fourmeasurement spectrums is corresponding tothe simulation spectrums.Established a set of the standard ionization chamber group whose energy response is less than 3% to implement the air kerma datum valuetransfering to the radiation field, the expanded uncertainty of 0.512%.The long-term stability and repeatability of medium energy radiation qualities were better than 0.5%, meeting the requirements of the ionization chamber radiotherapy. Preliminary air kerma,absorbed dose to water and dose equivalent conversion factors were studied.the absorbed dose to water calibration factor of ionization chamber radiotherapy NE2561 were calculated.The air kerma to dose equivalent(H *(10), H '(0.07, 0 °), Hp(10,0 °), Hp(0.07,0 °)) conversion factor of the narrow spectrum and wide spectrum radiationqualities were calculated by fitting method.