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瀬戸 慧大
Optics Express (Internet), 32(10), p.16999 - 17011, 2024/05
被引用回数：0 パーセンタイル：0.00(Optics)We propose stochastic ray tracing for laser beam propagation in Fresnel diffraction to find the duality between wave and ray representations. We transform from the Maxwell equations to the Schr
dinger equation for a monochromatic laser beam in the slowly varying envelope approximation. The stochastic ray tracing method interprets this Schrdinger equation as a stochastic process, of an analogy of Nelson's stochastic mechanics. It can illustrate the stochastic paths and the wavefront of an optical beam. This ray tracing method includes Fresnel diffraction effects naturally. We show its general theoretical construction and numerical tests for a Gaussian laser beam with diffraction, that stochasticity realizes the beam waist around the Rayleigh range.
瀬戸 慧大*; Zhang, S.*; Koga, J. K.; 長友 英夫*; 中井 光男*; 三間 圀興*
Progress of Theoretical and Experimental Physics (Internet), 2014(4), p.043A01_1 - 043A01_10, 2014/04
被引用回数：9 パーセンタイル：52.67(Physics, Multidisciplinary)From the development of the electron theory by H. A. Lorentz in 1906, many authors have tried to reformulate this model. P. A. M. Dirac derived the relativistic-classical electron model in 1938, which is now called the Lorentz-Abraham-Dirac model. But this model has the big difficulty of the run-away solution. Recently, this equation has become important for ultra-intense laser-electron (plasma) interactions. For simulations in this research field, it is desirable to stabilize this model of the radiation reaction. In this paper, we will discuss this ability for radiation reaction with the inclusion of vacuum polarization.
瀬戸 慧大*; Koga, J. K.; Zhang, S.*
レーザー研究, 42(2), p.174 - 178, 2014/02
Radiation reaction is one of the remaining big problems in theoretical physics. When an electron has high energy, radiation from this electron might become significant. Since this regime involves laser intensities over 
W/cm
, we need to consider it under next generation laser-electron interactions. Moreover, this radiation reaction is studied as an electron model in classical physics. Therefore, the research of ultrahigh intense laser-high energy electron interactions has the potential to take us to the center and essence of physics. However, the Lorentz-Abraham-Dirac theory which is the standard model of radiation reaction, has a difficulty of the run-away solution. In this paper, the history of the researches of radiation reaction, our recent studies and the experimental design of this process will be presented.
瀬戸 慧大*; 長友 英夫*; Koga, J. K.; 田口 俊弘*; 三間 圀興*
EPJ Web of Conferences, 59, p.17020_1 - 17020_4, 2013/11
被引用回数：0 パーセンタイル：0.00(Nuclear Science & Technology)When the laser intensity becomes higher than 10
W/cm, the motion of the electron becomes relativistic with the large radiation. This radiation energy loss transferred to the kinetic energy loss of the electron, is treated as an external force, the "radiation reaction force". We show the new equation of motion with radiation reaction and the simulation method and result of single electron system or dual electrons system with Li
nard-Wiechert field interaction.
瀬戸 慧大*; 長友 英夫*; Koga, J. K.; 三間 圀興*
Progress of Theoretical and Experimental Physics (Internet), 2013(5), p.053A01_1 - 053A01_10, 2013/05
被引用回数：2 パーセンタイル：18.73(Physics, Multidisciplinary)The intensity of ultra-short pulse lasers has reached W/cm owing to the advancements in laser technology. The large radiation from the electron behaves something like resistance in this ultrarelativistic laser-electron interaction. This effect is called the "radiation reaction". The equation of motion with the radiation reaction is known as the Lorentz-Abraham-Dirac equation; however, this equation does not incorporate the spin property. In laser plasmas, classical physics descriptions are preferred for simulations. This paper discusses how to describe the radiation reaction of a spinning relativistic electron in classical dynamics.
瀬戸 慧大*; 長友 英夫*; Koga, J. K.; 三間 圀興*
Plasma and Fusion Research (Internet), 7(Sp.1), p.2404010_1 - 2404010_4, 2012/02
In the near future, the intensity of the ultra-short pulse laser will reach to W/cm. When an electron is irradiated by this laser, the electron's behavior is relativistic with a significant bremsstrahlung. This radiation from the electron is regarded as the energy loss of electron. Therefore, the electron's motion is changed because of the kinetic energy changing. This radiation effect on the charged particle is the self-interaction, called the "radiation reaction" or the "radiation damping". For that reason, the radiation reaction appears in laser electron interactions with an ultra-short pulse laser whose intensity becomes larger than W/cm. In the classical theory, it is described by the Lorentz-Abraham-Dirac (LAD) equation. We propose the new equation of motion in the quantum theory with a radiation reaction in this paper.
瀬戸 慧大*; 長友 英夫*; Koga, J. K.; 三間 圀興*
Physics of Plasmas, 18(12), p.123101_1 - 123101_8, 2011/12
被引用回数：11 パーセンタイル：41.01(Physics, Fluids & Plasmas)The intensity of the ultra-short pulse lasers has reached 10 W/cm owing to the advancements of laser technology. When the motion of an electron becomes relativistic, bremsstrahlung accompanies it. The energy from this bremsstrahlung corresponds to the energy loss of the electron; therefore, the motion of the electron deviates from the case without radiation. The radiation behaves something like resistance. This effect called "radiation reaction" or "radiation damping" and the force converted from the radiation is named the "radiation reaction force" or the "damping force". The equation of motion with the reaction force is known as the Lorentz-Abraham-Dirac equation, but the solution of this equation isn't physical due to the fact that it has a "run-away" solution. As one solution of this problem, we have derived a new equation which takes the place of the Lorentz-Abraham-Dirac equation. We'll show the validity of this equation with a simple theoretical analysis.
瀬戸 慧大
no journal, ,
We will discuss the theoretical construction of kinetic models of charged particles in the nonlinear QED/scalar QED regime for multiple scattering effects. The notable point of this research was the challenge to derive the transport equations of charged particles from nonlinear QED. We expand the method given by de Groot et. al: we added a coherent EM field of a laser pulse in the relativistic quantum kinetic theory.
瀬戸 慧大; 小菅 淳; 長友 英夫*
no journal, ,
高強度電磁場下にある電子・陽電子・光子からなる系の集団現象は、プラズマ物理学と非線形QEDを融合して、はじめて議論できる。これまでの非線形QEDプラズマ模型は古典論的輸送方程式の衝突項に非線形QEDの散乱断面積を代入したに過ぎず、その理論的正当性は不明であった。そこで非線形QED Lagrangian密度から衝突断面積と輸送方程式を一度に矛盾なく導出したい。本研究ではその最初のステップとして非線形スカラーQED粒子の分布関数の構成法を検討する。
瀬戸 慧大
no journal, ,
Polarization-dependent nonlinear Compton scattering is discussed of an unpolarized electron in a high-intensity laser pulse of a linearly polarized plane wave. We developed the Monte Carlo calculation scheme employing the angular distribution formula of the photon emission in the locally constant field approximation that resolved photon energy, propagation direction, and polarization. The polarization feature shows how two polarization modes are different in the numerical result.
瀬戸 慧大
no journal, ,
欧州を中心として高強度レーザーパルスを用いた量子論的効果が精力的に研究されるようになってきた。特に非線形量子電磁力学(QED)で説明される散乱が予想されており、高強度レーザー施設ではこの散乱過程の実測を目指して研究開発が進められている。本発表では高強度レーザーが生み出す物理過程で、特に電子の電磁輻射過程を古典領域から非線形QEDまでの視点でレビューする。
瀬戸 慧大
no journal, ,
非線形量子電磁力学(quantum electrodynamics: QED)の基礎衝突過程である非線形Compton散乱(nonlinear Compton scattering: NCS)は高強度レーザーが提供する高強度電磁場中での物理現象として注目されている。NCSで生じる高エネルギー光子は別の非線形QED効果の"種"として寄与でき、背景にある高強度レーザー電磁場と相互作用して電子・陽電子対生成や真空複屈折などを発現させる。いくつかの実験グループはすでにNSCの測定に挑んでおり、さらに精密な計測を目指す計画もある。高強度レーザーパルスによる電子のNCSの理論的な研究や、レーザープラズマにNCSを含んだ数値計算も活発に行われている。モンテカルロ(Monte Carlo: MC)法は量子論的散乱に代表されるようなランダムさの表現に使用され、NCSにも応用されている。これまでのNSCのMC計算は光子の偏光和・散乱角度の積分を取った公式を採用しており、光子の偏光と角度分布を正確に解像できるMC計算法はまだ提案されていない。NCSを高エネルギー光子源とする実験を立案する際には、このようなMC計算が要求される。そのため、光子の偏光依存性・角度分布を考慮したNCSのMC法の提案と、その計算例を本講演で議論する。日本物理学会 第79回年会で企画されたシンポジウム「高強度レーザーが切り拓く物理学」における講演である。
瀬戸 慧大
no journal, ,
高強度レーザーの登場により、非線形量子電磁力学(QED)衝突過程の研究が欧州を中心として活発化してきた。QEDは電子・陽電子・光子の量子場模型であり、非線形QEDとはコヒーレントなレーザー電磁場が関与するQEDのことである。この衝突過程では非線形光学のように、電子・陽電子は背景レーザー電磁場の光子を多光子吸収する。現状は単一衝突過程の研究が主であるが、そのプラズマ集団現象への移行も近年注目されつつある。そこで、登壇者が実施中の非線形QEDから量子場の技法を用いてプラズマ輸送方程式を構築する研究の一端を議論する。
瀬戸 慧大*; 長友 英夫*; Koga, J. K.; 三間 圀興*
no journal, ,
If the laser intensity is higher than W/cm, strong bremsstrahlung might occur with a relativistic motion. Accompanying this, the "radiation reaction force" works on the charged particle. Therefore, it is necessary to study the radiation reaction effects in the ultra relativistic laser-electron interaction regime. We've considered the Lorentz-Abraham-Dirac (LAD) equation which can describe this phenomena, but it has mathematical difficulties. For solving this, there are many methods (the approximation of the radiation reaction force, new assumptions of the model). The LAD equation has been recently derived by the effective Lagrangian method in QED. This comes from the diagram of self-photon interaction. We will discuss about the meaning of the LAD equation and some other equations.
