A large area PPAC for using in tumor therapy with heavy ions

The principle of the heavy-ion therapy is introduced in this article. In order to precisely determine the irradiation profiles and positions of scanned heavy-ion beams, authors developed a large area parallel plate avalanche counter (PPAC). The detector consists of one anode, two cathodes and two windows with 250 mm x 250 mm active area. It was measured at an anode voltage of 700 V and with flowing C3F8 gas at the pressure of 700 Pa. A position resolution of 0.54 mm by correction was obtained with an α-source. As compared with the similar devices, authors consider the position resolution of the PPAC can satisfy the requirement of the facility of heavy-ion therapy. (author)