Application possibilities of plasmas generated by high power laser ablation

High-power pulsed lasers emitting IR and visible radiation with intensities ranging between 10^8 and 10^16 W/cm2, pulse duration from 0.4 to 9 ns and energy from 100 mJ up to 600 J, operating in single mode or in repetition rate, can be employed to produce non-equilibrium plasma in vacuum by irradiating solid targets. Such a laser-produced plasma generates highly charged and high-energy ions of various elements, as well as soft and hard X-ray radiations. Heavy ions with charge state up to 58+ and kinetic energy up to 10 MeV are detected. The plasma emits ion current densities of the order of tens of mA/cm^2. Interesting application possibilities of the generated plasmas concerning the ion implantation technique, the laser ion sources, the high intensity and resolution X-ray sources, the laser propulsion technique and the nuclear reaction of light elements are presented and discussed

Ion acceleration from intense laser-generated plasma: methods, diagnostics and possible applications

Abstract Many parameters of non-equilibrium plasma generated by high intensity and fast lasers depend on the pulse intensity and the laser wavelength. In conditions favourable for the target normal sheath acceleration (TNSA) regime the ion acceleration from the rear side of the target can be enhanced by increasing the thin foil absorbance through the use of nanoparticles and nanostructures promoting the surface plasmon resonance effect. In conditions favourable for the backward plasma acceleration (BPA) regime, when thick targets are used, a special role is played by the laser focal position with respect to the target surface, a proper choice of which may result in induced self-focusing effects and non-linear acceleration enhancement. SiC detectors employed in the time-of-flight (TOF) configuration and a Thomson parabola spectrometer permit on-line diagnostics of the ion streams emitted at high kinetic energies. The target composition and geometry, apart from the laser parameters and to the irradiation conditions, allow further control of the plasma characteristics and can be varied by using advanced targets to reach the maximum ion acceleration. Measurements using advanced targets with enhanced the laser absorption effect in thin films are presented. Applications of accelerated ions in the field of ion source, hadrontherapy and nuclear physics are discussed

Monitoring of the plasma generated by a gas-puff target source

A 10-Hz repetition rate, Nd:YAG pulsed laser (\ensuremath{\lambda}=1064\text{ }\text{ }\mathrm{nm}, pulse energy of 0.69 J, pulse duration of 3 ns) irradiated a Xe double-stream gas-puff target source. The interaction gives rise to the formation of plasma and emission of soft x-ray and extreme ultraviolet radiation. The produced plasma was investigated and characterized by a silicon carbide (SiC) and a commercial silicon (Si) detector, applying different spectral filters. Some parameters such as the plasma stability and its evolution (time trace profile and pulse time duration) are presented and discussed, evidencing pros and cons of the employment of SiC detectors with respect to the traditional Si for laser-generated plasma diagnostic

Protons and ion acceleration from thick targets at 1010 W/cm2 laser pulse intensity

AbstractProton ion acceleration via laser-generated plasma is investigated at relatively low laser pulse intensity, on the order of 1010 W/cm2. Time-of-flight technique is employed to measure the ion energy and the relative yield. An ion collector and an ion energy analyzer are used with this aim and to distinguish the number of charge states of the produced ions. The kinetic energy and the emission yield are measured through a consolidated theory, which assumes that the ion emission follows the Coulomb-Boltzmann-Shifted function. The proton stream is generated by thin and thick hydrogenated targets and it is dependent on the free electron states, which increase the laser absorption coefficient and the ion acceleration. The maximum proton energy, of about 200 eV, and the maximum proton amount can be obtained with thick metallic hydrogenated materials, such as the titanium hydrate TiH2

Diffusion of nitrogen gas through polyethylene based films

n/

Simple magnetic spectrometer for ions emitted from laser-generated plasma at 1010 W/cm2 intensity

AbstractPlasmas were generated by 3 ns pulsed lasers at 1064 nm wavelength using intensities of about 1010 W/cm2 irradiating solid targets with a different composition. The ion emission was investigated with time-of-flight measurements giving information of the ion velocity, charge state generation, and ion energy distribution. Measurements use a coil to generate a magnetic field suitable to deflect ions toward a Faraday cup and/or a secondary electron multiplier.Ion acceleration of the order of hundred eV per charge state, plasma temperature of the order of tens eV, charge states up to about 4+, and Boltzmann energy distributions were obtained in carbon, aluminum, and copper targets.The presented results represent useful plasma characterization methods for many applications such as the new generation of laser ion sources, pulsed laser deposition techniques, and post ion acceleration systems

Compact Thomson parabola spectrometer for fast diagnostics of different intensity laser-generated plasmas

A compact Thomson parabola spectrometer for diagnostics of laser-generated plasma, projected in Messina University, has been employed in different experiments concerning diagnostics of laser-generated plasmas. It allows to detect charged particles emitted from hot laser plasma and fast analyzing of their charge state, kinetic energy and mass-to-charge ratio. Moreover, it is possible to detect electrons emitted from laser-generated plasma. The spectrometer consists of a double pinhole input for alignment direction, a permanent magnet (0.004-4 kG) and an electric field ($0.05--5\text{ }\text{ }\mathrm{kV}/\mathrm{cm}$) both orthogonal to the direction of the incident particles, and different type of planar detectors (multichannel plates, phosphorous screen, gafchromic, CR39 and PM 355 track detectors). Measurements have been acquired at MIFT in Messina observing electrons up to 10 keV kinetic energy, at INFN-LNS of Catania using ions emitted from plasma submitted to a postacceleration up to 30 kV per charge state and at PALS Laboratory in Prague detecting energetic ions above 1 MeV per charge state. The particles recognition using the Thomson spectrometer has been obtained comparing the experimental parabola curves with the theoretical simulations obtained using COMSOL software. Results will be presented and discussed

Nuclear Fusion Effects Induced in Intense Laser-Generated Plasmas

Deutered polyethylene (CD2)n thin and thick targets were irradiated in high vacuum by infrared laser pulses at 1015W/cm2 intensity. The high laser energy transferred to the polymer generates plasma, expanding in vacuum at supersonic velocity, accelerating hydrogen and carbon ions. Deuterium ions at kinetic energies above 4 MeV have been measured by using ion collectors and SiC detectors in time-of-flight configuration. At these energies the deuterium–deuterium collisions may induce over threshold fusion effects, in agreement with the high D-D cross-section valuesaround 3 MeV energy. At the first instants of the plasma generation, during which high temperature, density and ionacceleration occur, the D-D fusions occur as confirmed by the detection of mono-energetic protonsand neutrons with a kinetic energy of 3.0 MeV and 2.5 MeV, respectively, produced by the nuclear reaction. The number of fusion events depends strongly on the experimental set-up, i.e. on the laser parameters (intensity, wavelength, focal spot dimension), target conditions (thickness, chemical composition, absorption coefficient, presence of secondary targets) and used geometry (incidence angle, laser spot, secondary target positions).A number of D-D fusion events of the order of 106÷7 per laser shot has been measured

POLYMERS CONTAINING Cu NANOPARTICLES IRRADIATED BY LASER TO ENHANCE THE ION ACCELERATION

Target Normal Sheath Acceleration method was employed at PALS to accelerate ions from laser-generated plasma at intensities above 1015 W/cm2. Laser parameters, irradiation conditions and target geometry and composition control the plasma properties and the electric field driving the ion acceleration. Cu nanoparticles deposited on the polymer promote resonant absorption effects increasing the plasma electron density and enhancing the proton acceleration. Protons can be accelerated in forward direction at kinetic energies up to about 3.5 MeV. The optimal target thickness, the maximum acceleration energy and the angular distribution of emitted particles have been measured using ion collectors, X-ray CCD streak camera, SiC detectors and Thomson Parabola Spectrometer

Ion energy increase in laser-generated plasma expanding through axial magnetic field trap

Laser-generated plasma is obtained in high vacuum (10−7 mbar) by irradiation of metallic targets (Al, Cu, Ta) with laser beam with intensities of the order of 1010 W/cm2. An Nd:Yag laser operating at 1064 nm wavelength, 9 ns pulse width, and 500 mJ maximum pulse energy is used. Time of flight measurements of ion emission along the direction normal to the target surface were performed with an ion collector. Measurements with and without a 0.1 Tesla magnetic field, directed along the normal to the target surface, have been taken for different target-detector distances and for increasing laser pulse intensity. Results have demonstrated that the magnetic field configuration creates an electron trap in front of the target surface along the axial direction. Electric fields inside the trap induce ion acceleration; the presence of electron bundles not only focuses the ion beam but also increases its energy, mean charge state and current. The explanation of this phenomenon can be found in the electric field modification inside the non-equilibrium plasma because of an electron bunching that increases the number of electron-ion interactions. The magnetic field, in fact, modifies the electric field due to the charge separation between the clouds of fast electrons, many of which remain trapped in the magnetic hole, and slow ions, ejected from the ablated target; moreover it increases the number of electron-ion interactions producing higher charge states