Characteristics of a selectively shielded p-Si detector in 60Co and 8 and 16 MV roentgen radiation.

A p-silicon semiconductor detector with a filter of wolfram powder mixed with epoxy, that entirely covered the back of the detector, was investigated and compared with ionization chambers and an unshielded semiconductor detector. Relative depth and profile distributions obtained as signals from the semiconductors were compared with corresponding dose distributions measured with the ionization chambers in 60Co, 8 and 16 MV roentgen radiation of different field sizes. It was found that relative signal distributions from the shielded semiconductor detector agreed, within 1 per cent of the maximum signal, to the depth dose curves and that the relative signal in profile distributions also agreed, within 1 mm or 1 per cent of the signal at the central axis, as compared with dose measurements with a cylindrical, thimble ionization chamber. The relative signal in the building-up region was compared with a plane parallel ionization chamber with a deviation corresponding to a position of less than 1 mm.