Initialising ...
Initialising ...
Initialising ...
Initialising ...
Initialising ...
Initialising ...
Initialising ...
ck scattering of 
-rays off nucleiKoga, J. K.; 早川 岳人
no journal, ,
Four processes are known to contribute to the scattering of -rays off nuclei. Since Delbrck scattering occurs from the polarization of the vacuum generated by virtual electron-positron pairs in the Coulomb field of the nucleus, its measurement can give us information about the properties of the vacuum. Although active research on Delbrck scattering stopped in the early 1990's, there is a renewed interest in its measurement. We will present our calculations of the Delbrck scattering, compare them with tabulated values, and show regimes where its contribution can be sufficiently isolated from the other processes and precisely measured. Deviations from the theoretical calculations would indicate the need for new physics beyond the Standard Model.
W/cm
Faenov, A.*; Hansen, S. B.*; Colgan, J.*; Abdallah, J.*; Pikuz, T.; Pikuz, S. A.*; Skobelev, I. Y.*; 西内 満美子; 榊 泰直; 前田 祥太; et al.
no journal, ,
We present new set of measurements of high spectrally resolved K-shell spectra of Al and Fe plasma obtained by thin foils irradiation using 40 fs laser pulses of J-KAREN laser facility with intensities up to 10 W/cm. Dependences of X-ray spectra from laser energy and thicknesses of foils were investigated. Measured power-law dependence of X-ray intensity vs laser beam intensity confirmed that at laser intensities higher than 10
W/cm Radiation Dominated regime could be reached. Two independent models are used to provide a detail theoretical study of the various configurations and processes roles in the formation of the observed spectra. Modeling demonstrated strong influence of X-ray photo pumping from laser-produced plasma for intensity and structure of observed X-ray spectra.
石野 雅彦; 長谷川 登; 錦野 将元; Pikuz, T.; Faenov, A.*; 山極 満; 河内 哲哉
no journal, ,
軟X線レーザーパルスをフッ化リチウム,銅、そしてアルミニウムの各表面に集光照射し、レーザー照射によって発生するプラズマの可視発光計測を試みた。軟X線レーザーの集光強度は1パルス当り10-30mJ/cmであった。軟X線レーザーの照射によって全てのターゲット表面にはアブレーション痕が生成されたが、プラズマからの可視発光を捉えることはできなかった。モデル計算によるアブレーション過程のシミュレーションでは、軟X線レーザーによってターゲット物質に誘起されるプラズマの電子温度は0.1-1eV程度と、大変低いことが予想されている。実験によって可視発光ができなかった結果は、シミュレーションから予想される計算結果を支持すると考えられる。
小瀧 秀行; 林 由紀雄; 森 道昭; 神門 正城; Koga, J. K.; Bulanov, S. V.
no journal, ,
In laser-plasma interaction, there are physical phenomena, such as quantum beam generation, relativistic self-focusing of laser pulses, frequency up-shift of laser pulses, etc. The generated electron beam has an ultrashort pulse width of the order of femtoseconds or less. In applications of these electron beams, stable and controllable electron beams are necessary. Stable and monoenergetic electron beams have been generated in the self-injection scheme of laser acceleration. The electron beam has 4 fs (FWHM). For the stable electron beam generation, long plasma channel formation via self-focusing is an important mechanism. We measured forward scattered radiation and an accelerated electron beam. In the spectrum, we observed a big frequency up-shift due to the change of the relativistic index and photon acceleration. The frequency up-shift changes the critical power of the self-focusing. The plasma channel is limited by the change of the power.
西内 満美子; 榊 泰直; 西尾 勝久; Orlandi, R.; 佐甲 博之; Pikuz, T.; Faenov, A. Ya.*; Esirkepov, T. Z.; Pirozhkov, A. S.; 松川 兼也*; et al.
no journal, ,
レーザー駆動イオン加速型のイオン加速はいろいろな応用面があることで着目され地得るが、その中でも核物理研究のための小型の加速器へのインジェクターの応用が考えられる。これを念頭に置き、JAEA KPSIにある比較的小型で高コントラスト短パルスレーザーJ-KARENを用いることで、イオン加速実験を行った。オンターゲット10Wcm
, 200TW, 
10J以下のエネルギーのパラメータを用いてプラズマミラーなしで43MeVの陽子線加速に成功している。またAlの加速を行ったところ、12MeV/uまでの加速に成功し、さらに加速されているイオンはほぼフルストリップに近い状態であることが分かった。これはレーザー駆動イオン線が重イオン加速器のコンパクトなインジェクターとして非常に有望であることを示す結果である。
神門 正城; Bulanov, S. V.; Esirkepov, T. Z.; Faenov, A.*; 福田 祐仁; 林 由紀雄; 桐山 博光; Koga, J. K.; 今 亮; 近藤 公伯; et al.
no journal, ,
High-field sciences treat phenomena that are revealed or initiated by irradiating high electromagnetic fields on matter. In the relativistic interaction of an intense electromagnetic wave (laser) and plasma, specific density distributions such as electron density cusps or spikes can be generated. Such cusps are moving at nearly speed of light and can reflect an incoming laser pulse into short-wavelength, pulse-compressed radiation as if they work as relativistic mirrors. In the recent relativistic flying mirror experiment conducted at JAEA, we have observed quasi-monochromatic extreme ultraviolet (XUV) radiation. Finally, an on-going upgrade of the experimental system at KPSI, JAEA is presented.
Pirozhkov, A. S.; 神門 正城; Esirkepov, T. Z.; Pikuz, T.; Faenov, A. Ya.*; 小倉 浩一; 林 由紀雄; 小瀧 秀行; Ragozin, E. N.*; Neely, D.*; et al.
no journal, ,
Plasma produced with relativistic-irradiance (I
10
W/cm) lasers is known as a source of XUV and X-ray radiation generated via various mechanisms. Recently discovered by us high-order harmonic emission from gas jet targets produces short-pulse coherent radiation desirable for many applications. According to our model, the harmonics are emitted by relativistic electron spikes, which are the density singularities resulting from catastrophes of a multi-stream relativistic plasma flow. Here we present high-resolution measurements of a XUV emission source which show that the radiation is indeed emitted by tiny sources, in accordance with the model prediction. In the experiment performed with the J-KAREN laser the XUV emission (60-100 eV) has been imaged on a LiF crystal detector, which reveals the detailed structure of the XUV sources, for example the double source consisting of two sub-micrometer radiating points, as predicted by the model.