The Role of a radial ion-track distribution in semiconductors studied by numerical simulations

Onoda, Shinobu; Hirao, Toshio; Oshima, Takeshi; Ito, Hisayoshi

Radiation Physics and Chemistry, 78(12), p.1116 - 1119, 2009/12

https://doi.org/10.1016/j.radphyschem.2009.06.025

The effects of radial ion track distribution on the unexpected noise (transient current) in semiconductors by a high energy heavy ion strike have been studied. The measured transient currents were compared with the numerically observed one, which was calculated with the wide variety of ion track radii. In the case of low energy (several MeVs) ion, the calculated transient currents were independent of the radial track distribution. However, in the case of high energy (several hundreds of MeVs) ion, the transient currents strongly depend on the radial track distribution. This difference is interpreted in terms of the carrier concentration at the core of track, resulting in the extremely different carrier mobility. When the radius of ion track used in numerical simulator was shorter than, or equivalent to, the penumbra radius, the reasonable agreement was found between experimental and calculated transient currents.

Pulse radiolysis study of ion-species effects on the solvated electron in alkylammonium ionic liquids

Kondo, Takafumi*; Asano, Akira*; Yang, J.*; Norizawa, Kimihiro*; Takahashi, Kenji*; Taguchi, Mitsumasa; Nagaishi, Ryuji; Kato, Ryuji*; Yoshida, Yoichi*

Radiation Physics and Chemistry, 78(12), p.1157 - 1160, 2009/12

https://doi.org/10.1016/j.radphyschem.2009.07.004

Spectrum and kinetic behavior of solvated electrons (e) in alkyl ammonium ionic liquids (ILs), DEMMA-TFSI, DEMMA-BF4, TMPA-TFSI, PP13-TFSI, P13-TFSI and P14-TFSI were investigated by pulse radiolysis method. The e in the ILs have same absorption peak at 1100 nm with a molar absorption coefficient of 1.5-2.310 dmmolcm. The reaction rate constant of e with Pyrene (Py) was 1.5-3.510 dmmols. These values were about one order of magnitude higher than that of diffusion controlled limit, which was calculated from measured viscosity. The dry electron (e) reacts with Py, and its rate constant in DEMMA-TFSI was 7.910 dmmols, three orders of magnitude higher than that of the e reactions.

Radiolysis study of actinide complexing agent by irradiation with helium ion beam

Sugo, Yumi; Taguchi, Mitsumasa; Sasaki, Yuji; Hirota, Koichi; Kimura, Takaumi

Radiation Physics and Chemistry, 78(12), p.1140 - 1144, 2009/12

https://doi.org/10.1016/j.radphyschem.2009.06.031

In the actual partitioning process of HLW, the organic complexing agent will be exposed to -particles emitted by -decay of the actinides. In this study, -radiolysis of TODGA in -dodecane was investigated by the irradiation with helium ion beam accelerated by the AVF cyclotron or the tandem accelerator in the TIARA facility at JAEA Takasaki. It was found that the radiation chemical yield for the degradation of TODGA by helium ion beam irradiation was less than that by -rays irradiation. It was also observed the radiation chemical yield gradually increased with the incident energy of helium ions. These results indicate that the radiolytic degradation of TODGA is reduced by high LET radiations such as -particles. Because the radical cations of -dodecane, which contribute to the charge transfer reaction described above, decrease by recombination in track.

Synchrotron radiation photoelectron studies for primary radiation effects using a liquid water jet in vacuum; Total and partial photoelectron yields for liquid water mear the oxygen -edge

Ukai, Masatoshi*; Yokoya, Akinari; Nonaka, Yusuke*; Fujii, Kentaro; Saito, Yuji

Radiation Physics and Chemistry, 78(12), p.1202 - 1206, 2009/12

https://doi.org/10.1016/j.radphyschem.2009.07.011

To substantiate the hydrated structure of DNA from the view point of the electronic properties, we developed a new spectroscopic technique of photoelectrons ejected from solutions dissolving biological molecules using soft X-ray synchrotron radiation in combination with liquid jet in vacuum. The experiments are carried out at the BL23SU in SPring-8, Japan. The liquid sample is maintained in the form of continuous micro-beam ( = 20 m) in vacuum and is intersected by a well focused nearly micro-beam of synchrotron-radiation of less than 50 m. In this paper, we present (1) the partial yields of photoelectrons for liquid water molecules and oxygen Auger electron spectra in the energy range around the oxygen K-edge, and (2) the total photoelectron yields for DNA nucleotides (AMP, CMP, and GMP) in water solutions near nitrogen K-edge, which correspond to the X-ray absorption spectra (XANES).

Spectral change of X-ray absorption near edge structure of DNA thin films irradiated with monochromatic soft X-rays

Fujii, Kentaro; Yokoya, Akinari

no journal, , 

In this study, we have investigated the spectral of the X-ray absorption near edge structure (XANES) of DNA caused by exposure to monochromatic soft X-rays. We used a calf thymus DNA thin film as a sample and observed nitrogen K-shell and oxygen K-shell XANES spectral changes. The typical monochromatic soft X-ray energies used for the irradiation (395, 408, 528, and 538 eV) were obtained from SPring-8, BL23SU. These energies correspond to just below nitrogen K-shell, just above nitrogen K-shell, just below oxygen K-shell, and just above oxygen K-shell, respectively. The obtained results indicate that carbonyl groups may be produced in the sample. In particular, the production of a propenal group (O=C-C=C) by oxygen ionization is expected. We will discuss the site selective damage induction in DNA using highly monochromatized synchrotron soft X-rays.

Lethality and mutagenesis of E. coli cells irradiated with soft X-rays

Suzaka, Takeshi; Shikazono, Naoya; Fujii, Kentaro; Yokoya, Akinari; Tauchi, Hiroshi*

no journal, , 

Soft X-rays have been widely used for the diagnostic of breast cancer (mammography). It has been generally thought that the relative biological effectiveness (RBE) of soft X-ray irradiation to living cells is similar to those of higher energy X-ray or -ray irradiation. On the other hand, Hill indicates that the risk of the soft X-ray exposure to organs may be higher than that of the -ray exposure because the interaction of soft X-ray photons with matter generates low energy secondary electrons. These electrons deposit their energy within a small volume of the scale of micrometers, thus induce dense ionization or excitation in genome DNA, whereas much less is known about the detail of the biological effect of soft X-rays. Recently we have shown that the yields of DNA strand breaks and oxidative base lesions induced in plasmid DNA by the direct effects of soft X-rays (150 kVp) is significantly higher than those by -ray irradiation. Present study investigates the effect of soft X-ray (150 kVp, W-target) irradiation to E. coli cells to highlight cellular responses. For this purpose, we have developed a novel experimental method to examine cell lethality and mutation frequency. A thin layer (100m) of cell-sample was prepared on a membrane so that all cells are uniformly irradiated with soft X-ray photons which have a short range in biological materials. We chose two genes, namely rpsL and mutant lac gene, as indexes of mutagenesis. Since experimental conditions strongly affected the survival of the cells, we have established optimal conditions for the experiment, such as temperature of solutions and cell density during culture. Using this method, we obtained the dose responses of survival fraction and mutation frequency of E. coli cells irradiated with soft X-rays. The correlation between DNA damage and the cellular effect of soft X-rays will be discussed.

Degradation of hydroxymaleimide in N-saturated 2-propanol by irradiation of energetic ions

Nakagawa, Seiko*; Taguchi, Mitsumasa; Ota, Nobuaki*; Hirota, Koichi

no journal, , 

no abstracts in English

Functionalized lignophenol as a high-selectivity sorbent for precious metals

Parajuli, D.; Hirota, Koichi

no journal, , 

Diffusion length of positrons and electrons

Zgardzinska, B.*; Hirade, Tetsuya; Goworek, T.*

no journal, , 

While you measuring positron annihilation lifetime by use of radioisotope, Na-22, electrons formed by ionization are accumulated gradually as trapped electrons. Positron can capture one of these trapped electrons easily to form positronium. The positronium formation can give information of trapped electrons. The diffusion length of positrons is larger at higher temperature and positronium formation probability are large. However, slow decrement of positronium formation was observed afterward. It is indicating that the diffusion length of electrons is also large at higher temperature and then saturated density of trapped electrons is small.

Improvement of chemical stability of grafted electrolyte membranes by ion-beam-induced crosslinking; Comparison with -ray irradiation

Koshikawa, Hiroshi; Yamaki, Tetsuya; Asano, Masaharu; Yoshida, Masaru; Maekawa, Yasunari

no journal, , 

We previously prepared ETFE-based membranes by -ray irradiation after the radiation grafting of styrene-derivatives for improving the chemical stability. The present study concerns the use of ion beams as a crosslinking tool instead of -rays. The membranes were prepared by the following procedures: pre--irradiation grafting of styrene into ETFE films, post-crosslinking by -irradiation of 1,000 kGy or O-ion irradiation of 6.3 MeV/n (26 kGy as an absorbed dose), and sulfonation. The membranes were measured the change in membrane weight during the course of oxidative degradation in a 3% hydrogen peroxide aqueous solution at 60C. The degradation onset time was longer for the O ions irradiated membrane than the -irradiated membrane. This means the LET effect on the crosslinking should form multiply crosslinked networks along its latent track, thereby improving the chemical stability of the membranes noticeably.