We present the study of optical and spectral properties of radiation-induced stable point defects, known as color centers (CCs), in lithium fluoride (LiF) for the detection of 10 keV XFEL beam at Spring-8 Angstrom Compact free electron LAser (SACLA) in Japan. A thick LiF crystal was irradiated in four spots with 10 keV XFEL beam (pulse duration = 10 fs) with different number of accumulated shots. After irradiation the colored-LiF spots were characterized with an optical microscope in fluorescence mode and their photoluminescence intensity and spectra were analyzed.
Compact sources of high energy protons (50-500MeV) are expected to be key technology in a wide range of scientific
applications <sup>1-8</sup>. Particularly promising is the target normal sheah acceleration (TNSA) scheme <sup>9,10</sup>, holding record level
of 67MeV protons generated by a peta-Watt laser <sup>11</sup>. In general, laser intensity exceeding 10<sup>18</sup> W/cm<sup>2</sup> is required to
produce MeV level protons. Enhancing the energy of generated protons using compact laser sources is very attractive
task nowadays. Recently, nano-scale targets were used to accelerate ions <sup>12,13</sup>. Here we report on the first generation of
5.5-7.5MeV protons by modest laser intensities (4.5 × 10<sup>17</sup> W/cm<sup>2</sup>) interacting with H<sub>2</sub>O nano-wires (snow) deposited
on a Sapphire substrate. In this setup, the plasma near the tip of the nano-wire is subject to locally enhanced laser
intensity with high spatial gradients, and confined charge separation is obtained. Electrostatic fields of extremely high
intensities are produced, and protons are accelerated to MeV-level energies. Nano-wire engineered targets will relax the
demand of peak energy from laser based sources.