CALIBRATION AND MEASUREMENT OF THE X-RAY PERSONAL DOSE EQUIVALENT WITH A H-p(10) IONIZATION CHAMBER

The value of the per sonal dose equiv a lent at a 10 mm depth is to char ac ter ize the en ergy de po si tion of strong pen e trat ing ra di a tion in the hu man body and is de rived by mea sure ment of air kerma and ap pli ca tion of con ver sion co ef fi cients from the ISO re port. How ever, the con ver sion co ef fi cients de pend strongly on the pho ton en ergy and an gles of in ci dence for low-en ergy pho tons. In or der to over come the prob lem that the con ver sion co ef fi cient of low en ergy rays changes greatly due to the small change of en ergy, a sec ond ary stan dard ion iza tion cham ber was used to mea sure the per sonal dose equiv a lent di rectly. A matched ref er ence field was es tab lished with 20-250 kV X-rays and cor rec tion fac tors with the Hp(10) cham ber were cal cu lated under these radiation qualities with different angles of incidence. The results showed that the dif fer ences were al most 22.7 % of cor rec tion fac tors for the low en ergy pho tons at an gles of in ci dence 0 degrees. With the con ver sion co ef fi cient rec om mended in ISO 4037-3-2019, the per for mance of the cham ber re sponse with re spect to Hp(10) in the en ergy range from 33 keV to 208 keV was within about +/- 10 %, and in the en ergy range from 12 keV to 208 keV and for an gles of in ci dence be tween 0 degrees and 75 degrees was within about +/- 19 %.