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Simulation of electron bunch generation by an ultrashort-pulse high-intensity laser-driven wakefield
M. Yamagiwa S. V. Bulanov T. Zh. Esirkepov J. Koga M. Kando Y. Ueshima K. Saito D. Wakabayashi 《Laser Physics》2006,16(2):252-258
Electron acceleration due to a wakefield excited by a ultrashort-pulse intense laser propagating through a finite-length underdense plasma layer is studied by two-dimensional particle-in-cell simulation. The electron energy distribution is analyzed for moderate to high intensity. For the electron density, where the pulse length is almost half of the plasma wavelength, dramatic changes of the density structure occur with cavity and bunch formation with an increase in the laser intensity, also leading to the appearance of a fast electron component well confined in phase space. The analytical form of the fast electron energy spectrum is also presented. 相似文献
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Dr. Kenta Arai Takahiko Matsunaga Haruhito Ueno Nozomi Akahoshi Yuumi Sato Dr. Gaurango Chakrabarty Prof. Dr. Govindasamy Mugesh Prof. Dr. Michio Iwaoka 《Chemistry (Weinheim an der Bergstrasse, Germany)》2019,25(55):12751-12760
At the redox-active center of thioredoxin reductase (TrxR), a selenenyl sulfide (Se−S) bond is formed between Cys497 and Sec498, which is activated into the thiolselenolate state ([SH,Se−]) by reacting with a nearby dithiol motif ([SHCys59,SHCys64]) present in the other subunit. This process is achieved through two reversible steps: an attack of a cysteinyl thiol of Cys59 at the Se atom of the Se−S bond and a subsequent attack of a remaining thiol at the S atom of the generated mixed Se−S intermediate. However, it is not clear how the kinetically unfavorable second step progresses smoothly in the catalytic cycle. A model study that used synthetic selenenyl sulfides, which mimic the active site structure of human TrxR comprising Cys497, Sec498, and His472, suggested that His472 can play a key role by forming a hydrogen bond with the Se atom of the mixed Se−S intermediate to facilitate the second step. In addition, the selenenyl sulfides exhibited a defensive ability against H2O2-induced oxidative stress in cultured cells, which suggests the possibility for medicinal applications to control the redox balance in cells. 相似文献
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Hosokai T Kando M Dewa H Kotaki H Kondo S Hasegawa N Nakajima K Horioka K 《Optics letters》2000,25(1):10-12
A new method of optical guidance by the implosion phase of a fast Z-pinch discharge in a gas-filled capillary is proposed. An imploding plasma column has a concave electron-density profile in the radial direction, just before a stagnation phase driven by a converging current sheet and a shock wave. The feasibility of optical guidance of a high-intensity (>1 x 10(17) W/cm(2)) Ti:sapphire laser pulse by use of this method over a distance of 2 cm, corresponding to 12.5 times the Rayleigh length, has been experimentally demonstrated. The guiding-channel formation process was directly probed with a He-Ne laser beam. The electron density in the fully ionized channel was estimated to be 2.0 x 10(17) cm(-3) on the axis and 7.0 x 10(17) cm(-3) on the peaks of the channel edge, with a diameter of 70 mum, as indicated by the experimental results, which were corroborated by a magnetohydrodynamics simulation. 相似文献
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Kando M Fukuda Y Pirozhkov AS Ma J Daito I Chen LM Esirkepov TZh Ogura K Homma T Hayashi Y Kotaki H Sagisaka A Mori M Koga JK Daido H Bulanov SV Kimura T Kato Y Tajima T 《Physical review letters》2007,99(13):135001
In a plasma wake wave generated by a high power laser, modulations of the electron density take the shape of paraboloidal dense shells, moving almost at the speed of light. A counterpropagating laser pulse is partially reflected from the shells, acting as relativistic flying mirrors, producing a time-compressed frequency-multiplied pulse due to the double Doppler effect. The counterpropagating laser pulse reflection from the plasma wake wave accompanied by its frequency multiplication (with a factor from 50 to 114) was detected in our experiment. 相似文献
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Mathieu Lobet Masaki Kando James K. Koga Timur Zh. Esirkepov Tatsufumi Nakamura Alexander S. Pirozhkov Sergei V. Bulanov 《Physics letters. A》2013
A method for the controlled generation of intense high frequency electromagnetic fields by a breaking Langmuir wave (relativistic flying mirrors) in a gradually inhomogeneous plasma is proposed. The wave breaking threshold depends on the local plasma density gradient. Compression, chirping and frequency multiplication of an electromagnetic wave reflected from relativistic mirrors is demonstrated using Particle-In-Cell simulations. Adjusting the shape of the density profile enables control of the reflected light properties. 相似文献
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Self-Injection and Acceleration of Monoenergetic Electron Beams from Laser Wakefield Accelerators in a Highly Relativistic Regime
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H.Yoshitama ;T.Kameshima ;谷渝秋 ;郭仪 ;焦春晔 ;刘红杰 ;彭翰生 ;唐传铭 ;王小东 ;温贤伦 ;温天舒 ;吴玉迟 ;张保汉 ;朱启华 ;黄晓军 ;安维民 ;黄文会 ;唐传祥 ;林郁正 ;王小东 ;陈黎明 ;H.Kotaki ;M.Kando ;K.Nakajima 《中国物理快报》2008,25(8):2938-2941
Self-injection and acceleration of monoenergetic electron beams from laser wakefield accelerators are first investigated in the highly relativistic regime, using 100 TW class, 27 fs laser pulses. Quasi-monoenergetic multi- bunched beams with energies as high as multi-hundredMeV are observed with simultaneous measurements of side-scattering emissions that indicate the formation of self-channelfing and self-injection of electrons into a plasma wake, referred to as a 'bubble'. The three-dimensional particle-in-cell simulations confirmed multiple self-injection of electron bunches into the bubble and their beam acceleration with gradient of 1.5 GeV/cm. 相似文献
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Kuroda M Yokosuka A Kobayashi R Jitsuno M Kando H Nosaka K Ishii H Yamori T Mimaki Y 《Chemical & pharmaceutical bulletin》2007,55(8):1240-1244
Cytotoxicity-guided fractionation of the 80% EtOH extract of Tithonia diversifolia has resulted in the isolation of twelve sesquiterpenoids (1-12), including three new ones (4, 10, 12), and three known flavonoids (13-15). The structures of the new compounds were determined by analysis of their spectroscopic data. The isolated compounds showed cytotoxic activity against HL-60 leukemia cells with IC(50) values ranging from 0.13 to 13.0 microM, when etoposide used as a positive control gave an IC(50) value of 0.43 microM. The cancer growth inhibitory property of 9, the main cytotoxic compound in T. diversifolia, was examined using a disease-oriented panel composed of 39 human cancer cell lines in the Japanese Foundation for Cancer Research. 相似文献
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