Pulses of x-rays 300 femtoseconds in duration at a wavelength 0.4 angstroms (30,000 electron volts) have been generated by 90° Thomson scattering between infrared terawatt laser pulses and highly relativistic electrons from an accelerator. In the right-angle geometry, x-ray burst is determined transit time pulse across ∼90-micrometer waist focused beam. The are directed (∼0.6° divergence) can be tuned energy. This source femtosecond will make it possible to combine techniques with ultrafast...

Laser ablation of dielectrics by ultrashort laser pulses is reviewed. The basic interaction between light and the dielectric material described, different approaches to modeling femtosecond dynamics are Material excitation induced a combination strong-field (multi-photon tunnel excitation), collisional (potentially leading an avalanche process), absorption in plasma consisting electrons excited conduction band. It discussed how these processes can be described various rate-equation models...

Structural transformations in a shallow surface region of bulk Ag (001) target irradiated by femtosecond laser pulse are investigated large-scale atomistic simulations and experiments. The reveal complex interplay fast melting, rapid resolidification, dynamic relaxation laser-induced stresses that leads to the formation subsurface porous covered nanocrystalline layer. generation is consistent with experimental observation ``swelling'' occurring at fluences below spallation/ablation threshold...

Ultrafast structural dynamics in laser-perturbed InSb are studied using time-resolved x-ray diffraction with a novel femtosecond source. We report the first observation of delay onset lattice expansion, which we attribute to energy relaxation processes and strain propagation. In addition, observe direct indications ultrafast disordering on subpicosecond time scale.

X rays produced by 90\ifmmode^\circ\else\textdegree\fi{} Thomson scattering of a femtosecond, near infrared, terawatt laser pulse 50 MeV electron beam are shown to be an effective diagnostic measure transverse and longitudinal density distributions ( $e$ beam) with subpicosecond time resolution. The was focused onto the $e$-beam waist, generating 30 keV x in forward direction. structures have been obtained measuring intensity x-ray beam, while scanning across space time. divergence has...

An approach to modeling ablation thresholds and depths in dielectric materials is proposed. The model based on the multiple-rate-equation description suggested by Rethfeld [Phys. Rev. Lett. 92, 187401 (2004)]. This has been extended include a of propagation light into sample. generic only few experimental quantities that characterize native material. A Drude describing evolution constant owing an excitation electrons material applied. compared data for different from literature.

Excitation of a quantum ladder system by frequency-swept (-chirped) laser pulses has been investigated studying an atomic model system, the 5s-5p-5d rubidium. The population transfer is significantly enhanced when frequency swept such that it follows spacing ladder. At intermediate intensities we observe oscillations in to upper level (5d), which can be attributed interference between two routes excitation: sequential and direct two-photon excitation via virtual state. We determine...

The ablation from a single-crystal Al(111) surface with single ultrashort near-infrared laser pulses has been investigated under ultrahigh vacuum conditions. Scanning-electron and atomic-force microscopy of the irradiated reveal surprising development material response at increasing fluence: low fluence, swelling exceeding one hundred nanometers dominates. At higher fluences, hole is gradually formed in swollen material, which eventually reaches below original level. observations indicate...

Simultaneous time-and-space resolved reflectivity and interferometric measurements over a temporal span of 300 ps have been performed in fused silica sapphire samples excited with 800 nm, 120 fs laser pulses at energies slightly well above the ablation threshold. The experimental results simulated frame multiple-rate equation model including light propagation. comparison evolution 400 nm clearly shows that two techniques interrogate different material volumes during course process. While...

The binding energies of the ${4s}^{2}4p^{2}P$ ground state in ${\mathrm{Ca}}^{\ensuremath{-}}$ have been determined by means state-selective photoionization Ca atoms produced s-wave photodetachment to be $24.55\ifmmode\pm\else\textpm\fi{}0.10$ meV for $J\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}1/2$ and $19.73\ifmmode\pm\else\textpm\fi{}0.10$ $J\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}3/2$ component. sensitivity detection technique applied has also made it possible...

The lifetime of the metastable autodetaching 1s2s2p $^{4}$${\mathit{P}}_{5/2}$ level $^{4}\mathrm{He}^{\mathrm{\ensuremath{-}}}$ ion has been measured by a time-of-flight technique to be 350\ifmmode\pm\else\textpm\fi{}15 \ensuremath{\mu}s using heavy-ion storage ring. Blackbody-induced photodetachment this weakly bound is shown influence decay rate nearly 20%, an effect not discussed previously. magnetic-field-induced mixing effects provide additional information about close-lying...

Radiotherapy is a well-established and important treatment for cancer tumors, advanced technologies can deliver doses in complex three-dimensional geometries tailored to each patient's specific anatomy. A 3D dosimeter, based on optically stimulated luminescence (OSL), could provide high accuracy reusable tool verifying such dose delivery. Nanoparticles of an OSL material embedded transparent matrix have previously been proposed as inexpensive which be read out using laser-based methods....

A new technique based on the combination of laser photodetachment and resonance ionization spectroscopy has been used to characterize state composition a fast, negative-ion beam barium determine binding energies its long-lived components, metastable $5d6s6p^{4}F_{9/2}$ ${6s}^{2}6p^{2}P_{3/2,1/2}$ ground state, with an accuracy previously inaccessible for weakly bound, negative alkaline-earth ions. Additional information about ${\mathrm{Ba}}^{\ensuremath{-}}$ states was obtained from lifetime...

The measurement of long (\ensuremath{\sim}10 \ensuremath{\mu}s--100 ms) ionic autodetachment lifetimes utilizing a heavy-ion storage ring is demonstrated with 10--125 keV beams ${\mathrm{Be}}^{\mathrm{\ensuremath{-}}}$. lifetime the metastable ${\mathrm{Be}}^{\mathrm{\ensuremath{-}}}$(2s2${\mathit{p}}^{2}$ $^{4}$${\mathit{P}}_{3/2}$) state was found to be 45\ifmmode\pm\else\textpm\fi{}5 \ensuremath{\mu}s, which represents an order-of-magnitude improvement in experimental accuracy over...

We present the characteristics of a new silicone-based radiochromic dosimeter containing leuco-malachite green (LMG) dye. The dose response as well dose-rate and photon-energy dependence were characterized. To optimise response, different concentrations chemical components investigated. was found to decrease exponentially function time after irradiation. A cylindrical produced irradiated with volumetric modulated arc therapy plan; standard deviation between measured calculated 5% total dose.

Abstract Purpose In agricultural soils, accumulation and bioavailability patterns of potentially toxic elements (PTEs) are key ecological health risk issues, especially in metal-based crop protection systems such as those applied vineyards. However, PTE levels the topsoils historical wine-growing regions Hungary have been scarcely studied so far. The specific goals this research were to assess tendencies PTEs complemented with human assessment two sloping vineyards pH-contrasted soils...

The interaction of relativistic electrons with terawatt femtosecond laser pulses is reviewed emphasis on how the scattering process can be used as a source ultrashort X-ray and time-resolved diagnostic for measuring transverse longitudinal phase space distributions an electron beam microns spatial subpicosecond temporal resolution. Recent experimental results are presented in which 90/spl deg/ Thomson was utilized to generate 300 fs duration X-rays peak energy 30 keV. It shown that, through...

Comprehensive dose verification, such as 3D dosimetry, may be required for safe introduction and use of advanced treatment modalities in radiotherapy. A radiochromic silicone-based dosimetry system has recently been suggested, though its clinical so far limited by a considerable dose-rate dependency the response. In this study we have investigated with respect to chemical composition dosimeter. We found that was reduced increasing dye concentration, response observed identical dosimeters...