title: Measurement of the stochastic radial dose distribution for a 30-MeV proton beam using a wall-less tissue-equivalent proportional counter.
abstract: The frequency distribution of the lineal energy, y, of a 30-MeV proton beam was measured as a function of the radial distance from the beam path, and the dosed mean of y, y¯(D), was obtained to investigate the radial dependence of y¯(D). A wall-less tissue-equivalent proportional counter, in a cylindrical volume with simulated diameters of 0.36, 0.72 and 1.44 µm was used for the measurement of y distributions, yf(y). The measured values of yf(y) summed in the radial direction agreed fairly well with the corresponding data taken from the microdosimetric calculations using the PHITS code. The y¯(D) value of the 30-MeV proton beam presented its smallest value at r = 0.0 and gradually increased with radial distance, and the y¯(D) values of heavy ions such as iron showed rapid decrease with radial distance. This experimental result demonstrated that the stochastic deposited energy distribution of high-energy protons in the microscopic region is rather constant in the core as well as in the penumbra region of the track structure.
authors.affiliation: Research Group for Radiation Protection, Japan Atomic Energy Agency, 2-4, Shirakata-shirane, Tokai-mura, Naka-gun, Ibaraki 319-1195, Japan tsuda.shuichi@jaea.go.jp.
authors.forename: S
authors.initials: S
authors.lastname: Tsuda
authors.affiliation: Research Group for Radiation Protection, Japan Atomic Energy Agency, 2-4, Shirakata-shirane, Tokai-mura, Naka-gun, Ibaraki 319-1195, Japan.
authors.forename: T
authors.initials: T
authors.lastname: Sato
authors.affiliation: Research Group for Radiation Protection, Japan Atomic Energy Agency, 2-4, Shirakata-shirane, Tokai-mura, Naka-gun, Ibaraki 319-1195, Japan.
authors.forename: T
authors.initials: T
authors.lastname: Ogawa
mesh_terms: D003198:Computer Simulation; D020450:Heavy Ions; D006801:Humans; D018499:Linear Energy Transfer; D019047:Phantoms, Imaging; D011522:Protons; D011829:Radiation Dosage; D011834:Radiation Monitoring / Q000295:instrumentation* / Q000379:methods*
chemical_list: D011522:Protons