Energetic α-particle sources produced through proton-boron reactions by high-energy high-intensity laser beams.

In an experiment performed with a high-intensity and high-energy laser system, α-particle production in proton-boron reaction by using a laser-driven proton beam was measured. α particles were observed from the front and also from the rear side, even after a 2-mm-thick boron target. The data obtained in this experiment have been analyzed using a sequence of numerical simulations.

Dynamic mitigation of the tearing mode instability in a collisionless current sheet.

Dynamic mitigation for the tearing mode instability in the current sheet in collisionless plasmas is demonstrated by applying a wobbling electron current beam. The initial small amplitude modulations imposed on the current sheet induce the electric current filamentation and the reconnection of the magnetic field lines. When the wobbling or oscillatory motion is added from the electron beam having a form of a thin layer moving along the current sheet, the perturbation phase is mixed and consequently the instability growth is saturated remarkably, like in the case of the feed-forward control.

Liquid Structure of Tantalum under Internal Negative Pressure.

In situ femtosecond x-ray diffraction measurements and ab initio molecular dynamics simulations were performed to study the liquid structure of tantalum shock released from several hundred gigapascals (GPa) on the nanosecond timescale. The results show that the internal negative pressure applied to the liquid tantalum reached -5.6 (0.

Absolute response of a Fuji BAS-TR imaging plate to low-energy protons (<0.2 MeV) and carbon ions (<1 MeV).

This paper reports on the absolute response of a Fuji BAS-TR image plate to relatively low-energy protons (<0.2 MeV) and carbon ions (<1 MeV) accelerated by a 10-TW-class compact high-intensity laser system. A Thomson parabola spectrometer was used to discriminate between different ion species while dispersing the ions according to their kinetic energy.

Proton beam quality enhancement by spectral phase control of a PW-class laser system.

We report on experimental investigations of proton acceleration from solid foils irradiated with PW-class laser-pulses, where highest proton cut-off energies were achieved for temporal pulse parameters that varied significantly from those of an ideally Fourier transform limited (FTL) pulse. Controlled spectral phase modulation of the driver laser by means of an acousto-optic programmable dispersive filter enabled us to manipulate the temporal shape of the last picoseconds around the main pulse and to study the effect on proton acceleration from thin foil targets. The results show that applying positive third order dispersion values to short pulses is favourable for proton acceleration and can lead to maximum energies of 70 MeV in target normal direction at 18 J laser energy for thin plastic foils, significantly enhancing the maximum energy compared to ideally compressed FTL pulses.

Laser resonance frequency analysis of pedicle screw stability: A cadaveric model bone study.

There is no evaluation method currently available to assess intraoperative pedicle screw fixation (PSF) strength. In this study, we established a laser-based resonance frequency analysis (RFA) system with high-speed, noncontact, quantitative measurements of PSF. Clinical investigations in the future can assess surgical failure risk of implants.

Polarity reversal of wakefields driven by ultrashort pulse laser.

Using an analytical model and computer simulation, we show that the wakefield driven by an ultrashort laser pulse in high-density plasma periodically reverses its polarity due to the carrier-envelope phase shift of the driver. The wakefield polarity reversal occurs on spatial scales shorter than the typical length considered for electron acceleration with the laser-wakefield mechanism. Consequently, the energies of accelerated electrons are significantly affected.

Relativistic flying forcibly oscillating reflective diffraction grating.

Relativistic flying forcibly oscillating reflective diffraction gratings are formed by an intense laser pulse (driver) in plasma. The mirror surface is an electron density singularity near the joining area of the wake wave cavity and the bow wave; it moves together with the driver laser pulse and undergoes forced oscillations induced by the field. A counterpropagating weak laser pulse (source) is incident at grazing angles, being efficiently reflected and enriched by harmonics.

Capturing roaming molecular fragments in real time.

Since the discovery of roaming as an alternative molecular dissociation pathway in formaldehyde (HCO), it has been indirectly observed in numerous molecules. The phenomenon describes a frustrated dissociation with fragments roaming at relatively large interatomic distances rather than following conventional transition-state dissociation; incipient radicals from the parent molecule self-react to form molecular products. Roaming has been identified spectroscopically through static product channel-resolved measurements, but not in real-time observations of the roaming fragment itself.

Plane photoacoustic wave generation in liquid water using irradiation of terahertz pulses.

We demonstrate photoacoustic wave propagation with a plane wavefront in liquid water using a terahertz (THz) laser pulse. The THz light can effectively generate the photoacoustic wave in water because of strong absorption via a stretching vibration mode of the hydrogen bonding network. The excitation of a large-area water surface irradiated by loosely focused THz light produces a plane photoacoustic wave.

Generation of megatesla magnetic fields by intense-laser-driven microtube implosions.

A microtube implosion driven by ultraintense laser pulses is used to produce ultrahigh magnetic fields. Due to the laser-produced hot electrons with energies of mega-electron volts, cold ions in the inner wall surface implode towards the central axis. By pre-seeding uniform magnetic fields on the kilotesla order, the Lorenz force induces the Larmor gyromotion of the imploding ions and electrons.

Ion species discrimination method by linear energy transfer measurement in Fujifilm BAS-SR imaging plate.

We have developed a novel discrimination methodology to identify ions in multispecies beams with similar charge-to-mass ratios, but different atomic numbers. After an initial separation by charge-to-mass ratios using co-linear electric and magnetic fields, individual ions can be discriminated by considering the linear energy transfer of ions irradiating a stimulable phosphor plate (Fujifilm imaging plate) by comparison with the Monte Carlo calculation. We apply the method to energetic multispecies laser-driven ion beams and use it to identify silver ions produced by the interaction between a high contrast, high intensity laser pulse; and a sub-micrometer silver foil target.

Charge-separated spectra of suprathermal highly charged bismuth ions in a dual laser-produced plasma soft x-ray source.

We investigated the charge-separated spectra of highly charged suprathermal bismuth (Bi) ions from a dual laser-produced plasma soft x-ray source developed for soft x-ray microscopy. The charge distribution of these suprathermal ions emitted from a solid planar Bi target was measured by an electrostatic energy analyzer. The maximum ionic charge state was observed to be Z = 17 and to possess a maximum energy of about 200 keV.

Characterization of gamma irradiation-induced mutations in Arabidopsis mutants deficient in non-homologous end joining.

To investigate the involvement of the non-homologous end joining (NHEJ) pathway in plant mutagenesis by ionizing radiation, we conducted a genome-wide characterization of the mutations induced by gamma rays in NHEJ-deficient Arabidopsis mutants (AtKu70-/- and AtLig4-/-). Although both mutants were more sensitive to gamma rays than the wild-type control, the AtKu70-/- mutant was slightly more sensitive than the AtLig4-/- mutant. Single-base substitutions (SBSs) were the predominant mutations in the wild-type control, whereas deletions (≥2 bp) and complex-type mutations [i.

Photon Energy-Dependent Ultrafast Photoinduced Terahertz Response in a Microcrystalline Film of CHNHPbBr.

Time-resolved terahertz (THz) spectroscopy is applied for a microcrystalline film of methylammonium lead bromide perovskite, CHNHPbBr, to observe the carrier dynamics around the band edge. The ultrafast response of the transmitted THz electric field amplitude after carrier generation is modeled with a biexponential curve with ∼5 and 180 ps time constants, which are ascribed to Auger and electron-hole recombination processes, respectively. From the pump photon energy dependence of the time evolution of the THz electric field amplitude, it is shown that the bound exciton states and free interband excited carrier states show a clearly different temporal response.

Participation of TDP1 in the repair of formaldehyde-induced DNA-protein cross-links in chicken DT40 cells.

Proteins are covalently trapped on DNA to form DNA-protein cross-links (DPCs) when cells are exposed to DNA-damaging agents. Aldehyde compounds produce common types of DPCs that contain proteins in an undisrupted DNA strand. Tyrosyl-DNA phosphodiesterase 1 (TDP1) repairs topoisomerase 1 (TOPO1) that is trapped at the 3'-end of DNA.

Modifying angular and polarization selection rules of high-order harmonics by controlling electron trajectories in k-space.

Recent advances in generation of strong laser pulses have enabled the acceleration of electrons in solids into regions far away from the band edge. Because nonlinear currents can be generated by laser-driven carriers in the non-parabolic region, tailored laser fields may allow control of optical properties of high-order harmonics (HHs). So far, investigations on laser-induced nonlinear optical phenomena have focused on the simple electron motion induced by linearly or elliptically polarized fields.

Propagation of THz irradiation energy through aqueous layers: Demolition of actin filaments in living cells.

The effect of terahertz (THz) radiation on deep tissues of human body has been considered negligible due to strong absorption by water molecules. However, we observed that the energy of THz pulses transmits a millimeter thick in the aqueous solution, possibly as a shockwave, and demolishes actin filaments. Collapse of actin filament induced by THz irradiation was also observed in the living cells under an aqueous medium.

Compact Thomson parabola spectrometer with variability of energy range and measurability of angular distribution for low-energy laser-driven accelerated ions.

This article reports the development of a compact Thomson parabola spectrometer for laser-accelerated ions that can measure angular distribution with a high energy resolution and has a variable measurable energy range. The angular-resolved energy spectra for different ion species can be measured in a single shot, and the sampling angle can be selected from outside the vacuum region. The electric and magnetic fields are applied to the ion dispersion by using a permanent magnetic circuit and annulus sector-shaped electrodes with a wedge configuration.

Clinical trial of photodynamic therapy for peripheral-type lung cancers using a new laser device in a pilot study.

Introduction/aim: Photodynamic therapy (PDT) involves the use of a tumor-specific photosensitizer and laser irradiation, and is one of the treatment options recommended for early centrally located lung cancers, but not yet for peripheral-type lung cancers. We developed a new laser probe, the composite-type optical fiberscope (COF), which allows accurate laser irradiation of a cancer lesion with simultaneous visualization of the lesion. In this study, we attempted a new endobronchial PDT technique using the new laser probe, and evaluated the effectiveness and feasibility of this novel PDT technique for peripheral lung cancers.

Effect of Small Focus on Electron Heating and Proton Acceleration in Ultrarelativistic Laser-Solid Interactions.

Acceleration of particles from the interaction of ultraintense laser pulses up to 5×10^{21}  W cm^{-2} with thin foils is investigated experimentally. The electron beam parameters varied with decreasing spot size, not just laser intensity, resulting in reduced temperatures and divergence. In particular, the temperature saturated due to insufficient acceleration length in the tightly focused spot.

Light source based on a 100 mm-long monolithic undulator magnet with a very short 4 mm-period length.

A novel method to fabricate undulator magnets of a-few-millimetre-period length is being explored. Plate-type magnets, 100 mm-long with 4 mm-period length, have been successfully fabricated. They produce an undulator field of approximately 3 kG at a gap of 1.

Laser Resonance Frequency Analysis: A Novel Measurement Approach to Evaluate Acetabular Cup Stability During Surgery.

Artificial joint acetabular cup stability is essential for successful total hip arthroplasty. However, a quantitative evaluation approach for clinical use is lacking. We developed a resonance frequency analysis (RFA) system involving a laser system that is fully contactless.

Destruction of tumor mass by gadolinium-loaded nanoparticles irradiated with monochromatic X-rays: Implications for the Auger therapy.

Synchrotron generated monochromatic X-rays can be precisely tuned to the K-shell energy of high Z materials resulting in the release of the Auger electrons. In this work, we have employed this mechanism to destruct tumor spheroids. We first loaded gadolinium onto the surface of mesoporous silica nanoparticles (MSNs) producing gadolinium-loaded MSN (Gd-MSN).