検索対象:     
報告書番号:
※ 半角英数字
 年 ~ 
 年
検索結果: 112 件中 1件目~20件目を表示

発表形式

Initialising ...

選択項目を絞り込む

掲載資料名

Initialising ...

発表会議名

Initialising ...

筆頭著者名

Initialising ...

キーワード

Initialising ...

使用言語

Initialising ...

発行年

Initialising ...

開催年

Initialising ...

選択した検索結果をダウンロード

論文

Effect of recombination between a molecular ion and an electron on radial dose in the irradiation of a heavy ion

森林 健悟

Applied Physics Research, 8(1), p.138 - 148, 2016/01

This paper discusses the effect of recombination between a molecular ion and a free electron on radial dose in the irradiation of a heavy ion through simulations. The exposure of a heavy ion produces molecular ions and free electrons due to the heavy ion impact ionization. The composition electric field, which is formed from these molecular ions, traps some of free electrons and these trapped free electrons increase radial dose near the heavy ion path. These trapped electrons also cause the recombination and that the recombination enhances radial dose.

論文

Simulation study of radial dose due to the irradiation of a swift heavy ion aiming to advance the treatment planning system for heavy particle cancer therapy; The Effect of emission angles of secondary electrons

森林 健悟

Nuclear Instruments and Methods in Physics Research B, 365(Part B), p.592 - 595, 2015/12

Aiming to advance the treatment planning system for heavy particle cancer therapy and to study cluster DNA damage, we have been developing a simulation model for radial dose due to the irradiation of a heavy ion. Now, two types of radial dose distributions have been available in the treatment planning system for heavy particle cancer therapy. However, these distributions had been developed without the detailed examinations of physical phenomena that occur near the trajectory of an incident ion, though this region is important to estimate the cell survival. The progress of computers allows us to execute such detailed examinations through simulations and to obtain radial dose closer to reality. We compare radial dose distribution obtained from our simulations with the conventional distributions and we suggest which conventional ones should be selected according to incident ion energies. Our simulation model, which has become possible in this century, is the only way to examine physical phenomena that occurs near the trajectory of an incident ion now as far as we know.

論文

Development of the radial dose distribution function relevant to the treatment planning system for heavy particle cancer therapy

森林 健悟

Physica Scripta, 90(5), p.054013_1 - 054013_5, 2015/05

 被引用回数:5 パーセンタイル:50.33(Physics, Multidisciplinary)

Radial dose has been employed in the treatment planning system for heavy particle cancer therapy in order to estimate the cell survival after the exposure to a heavy particle. The two models for radial dose distributions have been available. However, both of these models have very roughly treated the region near the trajectory of an incident heavy particle, although this region is very important to estimate RBE. The rapid progress of computers allow us to simulate the physical phenomena in detail and to obtain radial dose distributions closer to reality near the trajectory of an incident ion. We may succeed to the point that our model sufficiently reproduces the trend allowing us to select the better one between the two conventional models according to ion energies automatically. In future, we expect that further rapid progress of computers lead us to analyze them in more detail.

論文

Intensity of diffracted X-rays from biomolecules with radiation damage caused by strong X-ray pulses

甲斐 健師; 徳久 淳師*; 森林 健悟; 福田 祐仁; 河野 秀俊; 郷 信広*

Journal of the Physical Society of Japan, 83(9), p.094301_1 - 094301_5, 2014/09

 被引用回数:1 パーセンタイル:85.59(Physics, Multidisciplinary)

X線自由電子レーザー(XFEL)を利用した新たな単分子立体構造解析法が注目されており、この手法を実現するための最適条件の解明が期待されている。しかし、この手法では高強度のレーザーを使用するために、生じる分子の損傷が問題となる。本研究では単分子の損傷を考慮した上で、XFEL照射により得られる単分子の回折イメージング強度を様々な照射条件下において計算し、単分子立体構造解析を実現するために必要な照射条件について検討した。照射条件としてXFELの強度,エネルギー,パルス幅及び標的サイズをパラメータとし、標的を球状クラスターとした計算コードの開発を行った。本研究の成果により、XFEL照射による単分子の回折イメージング強度は入射X線のエネルギーが増加するとわずかに増加し、単分子の半径が400オングストローム以上になると照射強度に概ね比例することが分かった。XFEL照射条件を強度3$$times$$10$$^{19}$$photons/mm$$^{2}$$、パルス幅1fs、エネルギー15.5keV、及び標的半径500オングストローム以上であると、単分子立体構造解析を行うための十分な回折イメージング強度が得られ、最適条件の存在が示された。

論文

重粒子線の動径線量

森林 健悟

しょうとつ, 11(3), p.73 - 91, 2014/05

動径線量はイオンと物質との相互作用を理解する上で重要な物理量であり、生命医科学の分野に広く応用されている。普及されている動径線量には、その動径に沿って付与する線量が大きく異なる二通りのモデルがある。これは、イオンと物質との相互作用の理論モデルが二通りあり、それらがそれぞれ異なった線量分布を導き出したためである。我々は、二通りの理論モデルが共存できるシミュレーションモデルを開発し、入射イオンのエネルギーにより自動的に動径線量がどちらかの理論モデルの特徴をもつように振り分けることに成功した。この結果は、正確な動径線量の推定に役立つと共に、イオンと物質の相互作用の物理現象の深い解明に繋がると期待させるものである。

論文

Relaxation of plasmas created from irradiation of a heavy ion

森林 健悟

JPS Conference Proceedings (Internet), 1, p.013089_1 - 013089_4, 2014/03

This paper shows how plasmas are produced due to ion irradiation and discusses relaxation of these plasmas through simulation studies. The effect of these plasmas on the track structures is also discussed. In some theoretical studies, these plasmas were predicted and this effect was shown more than 35 years ago. However, no simulation studies report this effect before our studies. It is found that these plasmas play a role of bringing high local doses near the track of an incident ion. Such high local doses are expected to contribute significantly to the production of clustered DNA damage.

論文

Radial dose calculation due to the irradiation of a heavy ion; Role of composite electric field formed from the polarization of molecules and molecular ions

森林 健悟

Radiation Physics and Chemistry, 96, p.211 - 216, 2014/03

 被引用回数:11 パーセンタイル:23.31(Chemistry, Physical)

This paper discusses the role of composite electric field on radial doses through simulations due to the irradiation of a heavy ion. This composition electric field is formed from molecular ions, the polarization of molecules, and free electrons. Free electrons as well as these molecular ions are produced from the impact ionization of an incident ion or the other free electrons. This simulation model employs an isolated atom model that additionally may be able to treat the advantage of the free electron gas model. Some free electrons are trapped near the track of this incident ion and form plasma. The results obtained here show that this plasma plays a role of bringing about higher radial doses with increasing impact ionization cross sections of incident ions.

論文

Demonstrations for the effect of composite electric fields of molecular ions on the motion of secondary electrons due to ion irradiation

森林 健悟

Nuclear Instruments and Methods in Physics Research B, 314, p.30 - 33, 2013/11

 被引用回数:4 パーセンタイル:59.76(Instruments & Instrumentation)

Cancer therapy using carbon ions has a powerful therapeutic effect. This is based on the fact that relative biological effectiveness (RBE) of carbon ions is higher than that of protons and X-rays. A hypothesis has been proposed that clustered DNA damage is highly relevant to RBE values. However, it remains largely unknown how clustered DNA damage is generated after irradiation. We proposed and quantified that the electric field traps the emitted electrons near a radiation track, which, in turn, may lead to a clustering of DNA lesions. We have found that plasma with low electronic temperature and high density appears near the track of the incident ion in the irradiation of a carbon ion. The electrons in this plasma may more often interact with DNA which is located near the track and may produced the larger number of clustered DNA damages than the case where electric field is not considered and plasma is not formed.

論文

Movement of secondary electrons due to the irradiation of heavy ions; Role of the composite electric field formed from the polarization of molecules and molecular ions

森林 健悟

Radiation Physics and Chemistry, 85, p.36 - 41, 2013/04

 被引用回数:11 パーセンタイル:25.6(Chemistry, Physical)

This paper presents the development of a new simulation model for the movement of secondary electrons due to the irradiation of an ion into water which is the largest component in a cell. This movement is important for the study of track structures of ionizing radiation. Using this model, the effect of the electric field on this movement is discussed. The polarization of water molecules is added to molecular ions to form the electric field. Protons with the energies of 200 keV/u - 1 MeV/u and C$$^{6+}$$ ions with 3 MeV/u - 100 MeV/u are treated as incident ions. The results in this paper suggest that impact ionization cross sections of incident ions play an important role in the track structures.

論文

重粒子線によるDNA損傷; 重粒子線照射で生成するプラズマ振動の寄与を探る

森林 健悟

第6回光・プラズマプロセスのバイオ応用ワークショップ論文集, p.13 - 16, 2013/03

重粒子線によるがん治療は高い治療効果を持つことが知られている。その理由の一つはクラスターDNA損傷を作るからと考えられている。しかしながら、クラスターDNA損傷の生成機構はわかっていない。この機構がわかれば、より高い治療効果をもつがん治療の実現につながる可能性がある。そこで、この生成機構の解明を目指し、二次電子の運動のシミュレーションモデルを開発している。このモデルを用いて炭素線照射に二次電子の運動を計算したところ入射イオン衝突の電離過程でできる水分子イオンの合成電場が強く、さらに、その電場で多くの二次電子が入射イオンの軌道付近にトラップされることがわかった。これらのトラップされた二次電子はプラズマ振動を起こすと考えられる。プラズマ振動はDNAへの相互作用の回数を増やすことが期待でき、さらに、クラスターDNA損傷生成につながることが期待できる。重粒子線照射でどのようにプラズマ振動が発生し、緩和するか及びプラズマ振動が重粒子線によるDNA損傷に与える影響を説明する。

論文

談話室「異分野間の壁; 用語の定義の相違」

森林 健悟

しょうとつ, 10(2), p.43 - 45, 2013/03

異なった研究分野の研究者との交流(異分野交流)は異なった観点から研究を見つめ直したり、新しい展開や応用を見つけたりするなど研究の新たな開拓などに有用である。しかしながら、異分野間での歴史、研究対象などの違いが用語の定義などの相違を生み出し、それが議論の障害になることがしばしば起こる。それゆえに、異分野間で用語の定義などが相違することを紹介することは読者に有用な情報を得る機会になると考えられる。本論文ではレーザーやプラズマと放射線の研究分野の間での異分野交流中に気がついた「二次電子」や「自由電子」などの用語の定義の相違を述べ、それが生じる理由をそれらの研究分野の歴史や研究対象から推測した。

論文

Incorporation of the effect of the composite electric fields of molecular ions as a simulation tool for biological damage due to heavy ion irradiation, 2

森林 健悟

AIP Conference Proceedings 1465, p.241 - 245, 2012/07

 被引用回数:4 パーセンタイル:14.49

Swift heavy ions are a good research tool in the fields of biological physics, surface science, and medical science. For example, in biological physics, although there are several hypotheses, the important phenomenon of relative biological effectiveness (RBE) is not yet fully understood and one might ask why do heavier ions produce more cluster DNA damage and lead to high RBE values. The understanding of RBE is directly connected to the understanding of the reason why cancer therapy using C$$^{6+}$$ ions has higher efficiency than that using protons. In this paper, we propose and quantify a novel explanation for RBE that hinges on the effect of the composite electric fields of molecular ions (mainly H$$_2$$O$$^+$$) in a cell that are produced by heavy ion impact ionization processes by comparing the irradiation of a C$$^{6+}$$ ion with that of a proton onto the cell.

論文

生体高分子立体構造解明における原子分子物理の役割

森林 健悟

しょうとつ, 9(4), p.8 - 13, 2012/07

生体高分子の立体構造の解析は最近、X線自由電子レーザー光の応用として非常に注目されている。その構造の分解能を原子レベル近くにするには非常に大きなX線フラックスが要求され、そのとき生体分子は損傷する。その損傷は立体構造構築の際、ノイズとして現れるので損傷を正確に評価する必要がある。そこで、本論文では今まで行われてきた損傷の研究をレビューし、さらに、波長,パルス幅,X線フラックスなどのパラメータと損傷との関係の計算結果を報告する。

論文

The Interaction of high brightness X-rays with clusters or bio-molecules

森林 健悟

X-ray Spectroscopy (Internet), p.163 - 184, 2012/02

The analysis of three-dimensional structures of single bio-molecules has lately attracted considerable attention as an application of an X-ray free electron laser (XFEL) light. As the X-ray flux becomes larger, the better diffraction pattern is produced, however, the bio-molecules become more damaged. The damage, which appears as noise for this analysis, depend on the experimental parameters. We have shown the calculation results of the damage using various parameters such as wavelengths, pulses, X-ray fluxes. Since XFEL lights are focused to a spot size which is comparable with that of a bio-molecule in order to get high X-ray fluxes, it is not easy to irradiate the bio-molecule with the same X-ray flux for each shot. We also show our proposal for the measurement methods of the X-ray fluxes using the X-ray emission from hollow atoms and photo-electron spectra.

論文

Monte Carlo code for the damage of bio-molecules irradiated by X-ray free electron lasers; Incorporation of election impact ionization processes

森林 健悟

Progress in Nuclear Science and Technology (Internet), 2, p.893 - 897, 2011/10

This paper develops a Monte Carlo (MC) code for the calculation of the damage and the movement of free and quasi-free electrons, which are produced from the irradiation of X-ray free electron laser (XFEL) light pulses. Ionization processes such as X-ray absorption, Compton scattering, and Auger are treated by MC. On the other hand, the movements of free and quasi- free electrons are controlled by the Newton equations. Electron impact ionization processes occur when quasi-free electrons pass through the cross sections, which is assigned to atoms and ions. In order to confirm the accuracy of the calculations using our MC code, we compare the frequency of photo-electron impact ionization processes calculated by our MC code with that by the rate equations for spherical targets. Then, we have found agreement of 80 % to 90 % for the values of the frequency.

論文

Incorporation of the effect of the composite electric fields of molecular ions as a simulation tool for biological damage due to heavy-ion irradiation

森林 健悟

Physical Review A, 84(1), p.012702_1 - 012702_7, 2011/07

AA2010-0780.pdf:0.38MB

 被引用回数:17 パーセンタイル:30.85(Optics)

We theoretically study the DNA damage due to the effect of the composite electric field of H$$_2$$O$$^+$$ ions produced from the irradiation of a C$$^{6+}$$ ion with the energies of a few MeV/u and a proton with the energy of a few 100 keV/u to 1 MeV/u. We develop a new model for heavy particle irradiation in order to treat this composite electric field. We have found that the number of electrons trapped in the composite electric field depends on the cross sections of heavy particle impact ionization. We have also found that a larger number of electrons is produced due to the existence of the composite electric fields in the case of the irradiation of a C$$^{6+}$$ ion with the energies of a few MeV/u. This may promote the DNA damage, in particular, cluster DNA damage. The models given in this paper are also important in atomic and molecular elementary processes in electric fields and in the production of plasmas due to heavy particle irradiation.

論文

Photoelectron spectra produced from the irradiation of X-ray free-electron laser light pulses onto non-spherically symmetric targets

森林 健悟

Physica Scripta, T144, p.014049_1 - 014049_3, 2011/06

 被引用回数:2 パーセンタイル:77.51(Physics, Multidisciplinary)

X線自由電子レーザーなど最近、短パルス短波長高輝度X線源の開発が盛んに行われており、このX線源を用いた生体分子観測等の応用研究が検討されている。この開発や応用には、パルス幅やX線フラックスなどX線源の装置パラメータを知ることが不可欠である。ここでは中空原子(内殻電子が全くない状態)の発生及び光電子スペクトルを用いた観測手法の提案を行う。高輝度X線照射で生成された中空原子からの蛍光X線発生量と内殻励起状態(内殻電子が1つだけ電離した状態)からの蛍光X線の発生量の比は生体分子に照射されるX線フラックスに比例することがわかった。この比の観測が標的に照射されたX線フラックスの見積りになる可能性があることを明らかにした。高輝度X線照射で発生する光電子は、標的内に生じる電荷によってエネルギーを損失する。このエネルギーの損失によりX線フラックスを見積もれることを提案し、さらに、簡単な近似式を導きだし、それが、この観測に有効であることを示した。

論文

Spherically symmetric models for X-ray damage and the movement of electrons produced in non-spherically symmetric targets such as bio-molecules

森林 健悟

Journal of Physics B; Atomic, Molecular and Optical Physics, 43(16), p.165602_1 - 165602_7, 2010/08

We have developed a spherical symmetry model and an accurate model applied to the calculation of the damage of bio-molecules irradiated by X-ray free electron lasers (XFELs) for targets with shapes of a sphere and various ellipsoids. We discuss photo-electron impact ionization processes, energy losses of photoelectrons and the space distribution of free and quasi-free electrons. The electron distribution calculated by our spherical symmetry model agrees well with that calculated by our accurate model except for the place near the center in the spherical targets. The same tendency is shown at the ellipsoid targets with $$r$$ = 2 and 3 where $$r$$ is the ratio of the lengths of major axis with that of a minor one in the ellipsoid. Our spherical symmetry model can be applied to the target of one bio-molecule, that is, a lysozium.

論文

X線自由電子レーザー(XFEL)の生体分子照射によるX線フラックスの測定

森林 健悟

JAEA-Conf 2010-002, p.120 - 123, 2010/06

レーザー励起X線源やX線自由電子レーザーなど最近、短パルス短波長高輝度X線源の開発が盛んに行われており、このX線源を用いた生体分子等の応用研究が検討されている。この開発や応用には、パルス幅やフラックスなどX線源の装置パラメータを知ることが不可欠である。ここでは中空原子(内殻電子が全くない状態)の発生及び光電子スペクトルを用いた観測手法の提案を行う。高輝度X線照射で生成された中空原子からの蛍光X線発生量と内殻励起状態(内殻電子が1つだけ電離した状態)からの蛍光X線の発生量の比は生体分子に照射されるX線フラックスに比例することがわかった。この比の観測が標的に照射されたX線フラックスの見積りになる可能性があることを明らかにした。高輝度X線照射では光電子が発生するが、これは、標的内に生じる電荷によってエネルギーを損失する。このエネルギーの損失によりX線フラックスを見積もれることを提案し、さらに、簡単な近似式を導きだし、それが、この観測に有効であることを示した。

論文

Simulation and experiments of the laser induced breakdown of air for femtosecond to nanosecond order pulses

Koga, J. K.; 森林 健悟; 福田 祐仁; Bulanov, S. V.; 匂坂 明人; 小倉 浩一; 大道 博行; 山極 満; 木村 豊秋*; 藤川 武敏*; et al.

Journal of Physics D; Applied Physics, 43(2), p.025204_1 - 025204_15, 2010/01

 被引用回数:11 パーセンタイル:55.15(Physics, Applied)

Three dimensional simulations and experimental results for the laser induced breakdown of air are presented. The simulations include the laser propagation, multi-photon and impact ionization, and heating of the electrons using accurate atomic and molecular data. For laser pulses of duration from 100 femto-seconds to 1 nano-second mechanisms for the breakdown of air based on the pulse duration and intensity ranging from optical field ionization to electron impact ionization are found. The laser energies at which the breakdown occurs are found to be in good agreement with experimental results.

112 件中 1件目~20件目を表示