Secondary Electrons from Water Vapor with the Impact of 6.0 MeV/u He2+ Ions: Atomic Data and their Application to Biomedical Investigations

Journal Article · Fri May 27 00:00:00 EDT 2005 · AIP Conference Proceedings

DOI:https://doi.org/10.1063/1.1944700· OSTI ID:20718963

Sato, Y; Soga, F ^[1]; Ohsawa, D ^[2]; Higashi, A ^[3]; Kawauchi, H; Hirabayashi, M; Okada, Y ^[4]; Uehara, S ^[5]; Nikjoo, H ^[6]

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1. National Institute of Radiological Sciences, 4-9-1 Anagawa, 263-8555 Chiba-Inageku (Japan)
2. Kyoto University, Yoshida-konoe, 606-8501 Kyoto-Sakyoku (Japan)
3. Hyogo Ion Beam Medical Center, Shingu, Hyogo (Japan)
4. Science University of Tokyo, Yamazaki, 2641 Chiba-Noda (Japan)
5. Kyushu University, 3-1-1 Maidashi, 812-8582 Fukuoka-Higashiku (Japan)
6. NASA, Johnson Space Center, Houston TX 77058 (United States)

We measured the energy and angular distributions (7 eV-10 keV and 20 degree sign -160 degree sign ) of secondary electrons produced in collisions of 6.0 MeV/u He2+ ions with water vapor. Binary-encounter collision peaks were clearly observed at the calculated energies at angles of <90 degree sign , as well as the K-LL Auger peak of oxygen at about 500 eV for all angles. From these measurements, the doubly differential cross sections (DDCS) of electron emissions were deduced with an estimated uncertainty of {+-}13%. The energy distribution (SDCS) was also obtained by integrating the DDCS values with respect to the ejected angles, and compared with an empirical model of Rudd. The energy spectrum (SDCS) showed good agreement with the model of Rudd in the energy range of secondary electrons of <100 eV. However, in the 100-1000 eV energy range, the experimental spectrum shows significant discrepancies, smaller by 30%, and is nearly twice greater in the region >3keV. To assess the new cross sections, these values were incorporated in the kurbuc Monte-Carlo track structure code system for a simulation of secondary electrons. Radial dose distributions for 6.0 MeV/u He2+ ions were obtained by analyzing the tracks generated by the code kurbuc using the new DDCS values. In the core with a radius (r) of less than 1 nm, the dose is very high due mainly to excitation events, induced by low-energy electrons. The penumbra shows a well-known r-2 dependence.

• OSTI ID: 20718963
• Journal Information: AIP Conference Proceedings, Vol. 771, Issue 1; Conference: ITC14: 14. international Toki conference on plasma physics and controlled Nuclear Fusion; ICAMDATA2004: 4. international conference on atomic and molecular data and their applications, Toki (Japan), 5-8 Oct 2004; Other Information: DOI: 10.1063/1.1944700; (c) 2005 American Institute of Physics; Country of input: International Atomic Energy Agency (IAEA); ISSN 0094-243X
• Country of Publication: United States
• Language: English

Related Subjects

74 ATOMIC AND MOLECULAR PHYSICS
ANGULAR DISTRIBUTION
ELECTRON EMISSION
ELECTRON-MOLECULE COLLISIONS
ELECTRONS
ENERGY SPECTRA
EV RANGE
EXCITATION
HELIUM IONS
ION BEAMS
ION-MOLECULE COLLISIONS
KEV RANGE 01-10
MEV RANGE 01-10
MONTE CARLO METHOD
PARTICLE TRACKS
RADIATION DOSE DISTRIBUTIONS
SIMULATION
WATER VAPOR