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Nuclear reactions between protons and boron-11 nuclei (p–B fusion) that were used to yield energetic α-particles were initiated in a plasma that was generated by the interaction between a PW-class laser operating at relativistic intensities (~3 × 1019 W/cm2) and a 0.2-mm thick boron nitride (BN) target. A high p–B fusion reaction rate and hence, a large α-particle flux was generated and measured, thanks to a proton stream accelerated at the target's front surface. This was the first proof of principle experiment to demonstrate the efficient generation of α-particles (~1010/sr) through p–B fusion reactions using a PW-class laser in the "in-target" geometry. [ABSTRACT FROM AUTHOR]

An experimental platform using X‐ray free‐electron laser (XFEL) pulses with high‐intensity optical laser pulses is open for early users' experiments at the SACLA XFEL facility after completion of the commissioning. The combination of the hard XFEL and the high‐intensity laser provides capabilities to open new frontiers of laser‐based high‐energy‐density science. During the commissioning phase, characterization of the XFEL and the laser at the platform has been carried out for the combinative utilization as well as the development of instruments and basic diagnostics for user experiments. An overview of the commissioning and the current capabilities of the experimental platform is presented. An experimental platform using X‐ray free‐electron laser (XFEL) pulses with high‐intensity optical laser pulses has been developed at the SACLA XFEL facility. An overview of the commissioning and the capabilities of the experimental platform is presented. [ABSTRACT FROM AUTHOR]

Direct measurement of extremely high energy density electrons created in ultraintense laser-plasma interactions is crucial issue for fast ignition. Recently Cherenkov radiation has been studied to obtain the energy distribution of electrons because the emission angle depends on the electron energy. However in the previous studies [F. Brandl et al., Europhys. Lett. 61, 632 (2003); M. Manclossi et al., Phys. Rev. Lett. 96, 125002 (2006)], the experimental configurations using a planar target raised issues of spatial overlapping among the light from the different energy electrons as well as from the other emissions, such as transition radiation. A novel prism shaped target is developed in which Cherenkov lights emitted from different energy electrons are spatially separated, realizing an absolute measurement of the energy spectrum by counting the light intensities in each observed position. The observed image clearly shows the horseshoe pattern as expected in fully three-dimensional ray-trace calculations, and the image is successfully converted into the electron spectrum inside the target. In addition, it is found from the blur of the outer edge of the Cherenkov pattern that the electrons have a small beam divergence. The calibrated energy spectrum well agrees with particle simulations. [ABSTRACT FROM AUTHOR]

Since an imaging plate (IP) is sensitive to electron, ion, and x rays, it can be used as a detector for laser plasma experiment using ultraintense laser. Moreover, an IP has the advantageous features such as high sensitivity, wide dynamic range, and high spatial resolution. Even though IP itself has a considerable wide dynamic range up to 105, the IP data have appeared often saturated at an IP reading device. We propose a reading technique by inserting optical density filters so that an apparently saturated IP data can be saved. [ABSTRACT FROM AUTHOR]