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The focused field and its intensity distribution achieved by the 4pi-spherical focusing scheme are investigated within the framework of diffraction optics. Generalized mathematical formulas describing the spatial distributions of the focused electric and magnetic fields are derived for the transverse magnetic and transverse electric mode electromagnetic waves with and without the orbital angular momentum attribute. The mathematical formula obtained shows no singularity in the field in the focal region and satisfies the finite field strength and electromagnetic energy conditions. The 4pi-spherical focusing of the transverse magnetic mode electromagnetic wave provides the highest field strength at the focus and the peak intensity reaches 10^26^ W/cm^2^ for the laser power of 100 PW at 800 nm wavelength. As an example of using the mathematical formula, the electron-positron pair production via the Schwinger mechanism is analyzed and compared with previous results.

Ultrahigh intensity lasers inducing Micro-bubble implosions (MBI) have the potential to produce ultrahigh densities and consequently ultrahigh electrostatic fields. The field can be sufficiently strong so that gamma-rays passing near the imploded MBI core can be bent by the modification of the vacuum making transient gamma-ray lenses possible. At sufficiently high laser intensities the electrostatic fields could approach the Schwinger field. The substantial reduction of the pair creation threshold field from the vacuum in the finite volume of multiple focusing lasers has been shown previously. Here, we apply the same formalism to the Coulomb fields in the finite volume of the MBI to determine the probability of electron-pair creation verses initial density and cavity size., 2019 US-Japan Workshop on Theory and Simulations of High Energy Density Physics with Extreme Fields

We show that electron-positron pair production from the vacuum is possible via the strong Coulomb fields generated by micro-bubble implosions induced by ultra-high intensity lasers. Even in the case where the Coulomb fields are lower than the pair creation threshold, externally injected high energy electrons or photons could be used to generate pairs.

We show investigations into using high intensity lasers to stop high energy electron beams., The 2018 International Workshop on Future Linear Colliders (LCWS18) 出席

Relativistic flying mirrors generated by ultra-high intensity laser pulses propagating in plasma have been used to upshift and focus counter-propagating laser pulses via the double Doppler effect. We have shown that a source pulse of high intensity generates boosted harmonics. We will simulate two colliding laser pulses of high intensity colliding and present our considerations for using relativistic flying mirrors for achieving high flux γ-ray sources., 45thConference on Plasma Physics

The large discrepancy between measurements and theoretical predictions of photon-photon is mainly due to the very small cross section and need for high photon fluxes. We previously theoretically investigated the possibility of measuring it using relativistic mirrors. We further investigate this using particle-in-cell simulations and estimate the laser parameters necessary to observe photon-photon scattering and pair creation., 国際学会HEDLA2018参加

For several decades the capillary discharges have been under intensive investigations due to various promising applications, e.g. for the laser electron accelerators as well as for the X-ray lasers [1,2]. A major portion of the experiments were done with circular cross-section capillaries. An appropriate theoretical and numerical study of circular capillaries can be greatly simplified to a 1D model [3] assuming rotational and axial symmetries of the plasma flow in a long thin channel. On the other hand, studying capillaries with non-circular cross-section [4], which have been attracting substantially less attention, requires more complicated 2D models. Such capillaries, for example, square one, possess several advantages related to their fabrication as well as for plasma diagnostics The aim of our work is to compare the plasma density and temperature distributions formed at the quasistationary stage of the discharge. We present the results of MHD simulations of hydrogen-filled capillary discharges with circular and rectangular cross-sections under almost the same conditions characterizing the initial configurations and the external electric circuit. The simulation parameters are choosen to correspond to the capillary discharge based waveguide for the laser wakefield accelerator [5]. Bibliography [1] Leemans W. P. et al 2014 Phys. Rev. Lett. 113 245002 [2] Benware B. R. et al 1998 Phys. Rev. Lett. 81 5804 [3] Bobrova N. A. et al 2001 Phys. Rev. E 65 016407 [4] Gonsalves A. J. et al 2007 Phys. Rev. Lett. 98 025002 [5] Esarey E. et al 2009 Rev. Mod. Phys. 81 1229

We have previously shown that laser light can be upshifted to higher frequencies by its reflection off relativistically moving mirrors in plasma. These mirrors were generated with ultra-high intensity laser pulses. However, the laser light which was reflected off the mirrors had relatively low intensity. We show via simulations that even high intensity light can be reflected off the mirrors and that this can generate relativistically upshifted harmonics.