Laser-plasma Ion Research Articles

Non-selective photoionization for isotope ratio measurements by time of flight mass spectrometry with laser ablation

Isotope ratio measurements of metallic uranium samples were carried out by linear TOF mass spectrometry in combination with laser ablation. To eliminate the problems resulting from laser plasma ion energy and spatial dispersions, the uranium atoms were post-ionized by the third harmonic of a Nd-YAG laser. Experimental and theoretical results of the LA-TOF performance and non-selective photoionization of uranium atoms produced by laser ablation are presented.

A Laser-Plasma Ion Source with Normal Light Incidence on the Target Surface

A laser ion source with the beam focused along the normal to the target surface was designed and produced. Tests of this system performed in comparison with the conventional for laser sources laser-beam injection and focusing at an angle of 45° have shown that the fraction of multiply charged high-energy ions significantly increases in such a design of the source.

Line profile and spectral gain calculations for high-z ions in X-ray laser plasmas

Line profiles and spectral distributions of small signal gain for the n = 4–6 to n′ = 3–4 transitions in He-like Ne, Li-like Al, and Na-like Cu are considered for plasma conditions typical for theoretical and experimental studies of recombination and resonantly photopumped X-ray laser schemes. The calculations were done using the extended version of helm code and involved quasi-static ion broadening, impact electron broadening, natural, and Doppler broadening along with the population kinetics for initial and final states in the presence of the plasma ion microfield.

Thomson parabola ion spectrograph with the microchannel plate image converter in investigations of high-Z laser plasma ion sources

The results of experimental investigations on ion production from tantalum targets, made with the application of the Thomson parabola ion spectrograph (TP) to an image converter equipped with a microchannel plate of the size of 70×90 mm2, are presented. In the experiments, the iodine photodissociation laser system PERUN (λ=1.315 μm, EL≤50 J, τ∼350–650 ps. I≤1015 W/cm2) was used for ion generation. The TP can give useful information about physical processes, ion species, their energies, and charge states from a single laser shot. The results obtained are compared with the results of measurements made with an electrostatic ion energy analyzer and charge collectors and they are used to estimate the Ta ion yield with an average charge state of 40+. The obtained values are N∼2.6×1011 sr−1.

Estimation of optimum electron temperature for maximum x-ray laser gain from 3p–3s transitions of neonlike ions in laser plasmas

The fraction of neonlike ions and the average ionic charge state in laser plasmas formed at the surface of the solid targets of germanium, selenium, and krypton have been obtained at several electron temperatures using the steady-state collisional radiative ionization model. Dielectronic recombination has been considered. The effect of consideration of dielectronic recombination of ions of one or more charge states on these parameters has been studied. It is observed that the values of electron temperature corresponding to the maximum abundance of neonlike ions in different cases of dielectronic recombination are significantly different from those obtained without consideration of dielectronic recombination. The optimum electron temperature of the plasma is estimated from the maximization of the x-ray laser gain through temperature-dependent variables of the gain coefficient and is observed to be the electron temperature at which the abundance of neonlike ions is maximum.

Spectra of ions in a four-element laser plasma

The spectra of multiply charged ions were studied by mass spectrometry of one-element (Y, Cu, O) and four-element (YBa2Cu3O7) laser plasmas formed by radiation of power density 108—1010 W cm-2. The transition from the one-element to the four-element plasma revealed an increase in the rate of the recombination processes and a reduction in the maximum charge and energy of the plasma ions.

Use of higher-order reflection from mica crystals in x-ray spectroscopic investigations at 0.1–0.3 nm

Crystallographic and dispersion characteristics of mica at high (V—XI) reflection orders were investigated for the first time. Even the order-XI integral reflection was sufficiently strong to be used in experiments. High-precision bending of a mica crystal along a spherical surface with a small radius R = 100 mm and the use of such crystal analysers in focusing spectrographs with one-dimensional and two-dimensional spatial resolution made it possible to record low-intensity spectra of multiply charged ions in laser and Z-pinch plasmas. The method provides exceptional spectral resolution λ/Δλ ≈ 6000–10 000 in a wide spectral range (0.15–1.8 nm).

Intense high charge state ion sources (invited)

A review of Penning ionization gauge (PIG), duoplasmatron (DP), laser-plasma ion source (LPIS), Electron cyclotron resonance ion source (ECRIS), and electron beam ion source (EBIS) used for the production of intense and high charge state ion beams is given. The outputs of high charge states of different elements of the Periodic Table from ion sources of these types are compared. Bare nuclei up to Ar can be obtained from EBIS and ECR and Xe+54 from EBIS. Comparisons are made of compilations of the output (high average current of 107–1017 pps) for different charge states of Xe for PIG, DP, ECRIS, EBIS ion sources and Ta, Pb for different charge states of the LPIS. The present level and perspectives of development (a pulsed gas feed, stationary electric field) of the PIG ion source are presented. The beam performance and future development of these intense and high charge state ion sources are discussed from the point of view of the perspectives of the cyclotron programs at FLNR and JINR.

Monochromatic spatial resolution in the soft X-ray wavelength range

The author suggests a new method which make use of glass capillary arrays to diagnose isoelectronic laser plasma ions. This new set up includes a fiber-like array, located close to the soft-X-ray source, to generate a quasi parallel polychromatic beam which is then diffracted by a grating. This quasi parallel beam is then diffracted by a plane grating; use of a holographic grating with a nonuniform groove distribution and focusing properties increases the spatial resolution as well as the luminosity of the set up. Rough approximation shows that diffracted images may be obtained in a single shot.

Characteristics of fast particles generated by a subnanosecond laser plasma

An investigation was made of the spectral and energy characteristics of suprathermal laser-plasma ions and electrons using the experimental data obtained by spherical irradiation of glass microspheres in the Progress six-channel laser facility. The power density of the λ = 1.06 μm radiation on the surface of the target was (1–2) × 1015 W/cm2. The main role in the formation of the suprathermal particle spectrum was played by resonant absorption of laser radiation: up to 90% of the energy absorbed by the resonant mechanism was dissipated in the acceleration of suprathermal ions.

Laser ion sources for ion implantation (invited)(abstract)

The further progress in the employment of ion beams in technology depends on the improvement of the ion beam formation and transport systems. The range of the devices constructed now includes both weak current devices focusing the beam to less than 0.01 μm for the purpose of microelectronics, and powerful high current multibeam plants to modify metals and alloys. Among the wide range of such equipment are the universal devices able to generate the ion beams of different species without constructive changes. For these devices the laser plasma ion source is particularly helpful. This report presents a review of the 20-year study of the laser plasma, the parameters of laser plasma ion components, the means of the ion beam formation from laser plasma, as well as the results concerning the employment of laser plasma ion sources in analytical and technological equipment.

The bonding of protective films of amorphic diamond to titanium

Films of amorphic diamond can be deposited from laser plasma ions without the use of catalysts such as hydrogen or fluorine. Prepared without columnar patterns of growth, the layers of this material have been reported to have ‘‘bulk’’ values of mechanical properties that have suggested their usage as protective coatings for metals. Described here is a study of the bonding and properties realized in one such example, the deposition of amorphic diamond on titanium. Measurements with Rutherford backscattering spectrometry and transmission electron microscopy showed that the diamond coatings deposited from laser plasmas were chemically bonded to Ti substrates in 100–200-Å-thick interfacial layers containing some crystalline precipitates of TiC. Resistance to wear was estimated with a modified sand blaster and in all cases the coating was worn away without any rupture or deterioration of the bonding layer. Such wear was greatly reduced and lifetimes of the coated samples were increased by a factor of better than 300 with only 2.7 μm of amorphic diamond.

Laser-plasma ion sources (invited)(abstract)

Basic principles of the operation of laser-plasma multicharged ion sources are given. Specific features of the interaction of high-intensity laser beams with solids are discussed, together with formation and main characteristics of multicharged ion beams, such as charge state distribution, angular distribution, emittance and time structure, and the influence of magnetic fields. Laser ion sources constructed for linear accelerators, synchrotrons, and cyclotrons are presented and experimental data are compared with theoretical considerations.

Laser plasma ion source for intense heavy ion beams (abstract)

In a series of experiments a laser plasma ion source for TA ions has been investigated. The main components were a 3-J CO2 laser, the laser ion source, a 3.2-m beamline, a 90° analyzing magnet, and an ion detector. The FWHM of the CO2 laser pulse was approximately 100 ns, the full duration was about 1 μs. The spot diameter was about 0.2 mm. The charge state distribution has been measured up to 10+. The plasma temperature has been calculated; recombination has been observed. The results will be shown and discussed in detail.

Macroparticle acceleration by a laser-plasma stream

A physical model is proposed for macroparticle acceleration in an expanding laser plasma. Two acceleration mechanisms are considered, based on absolutely inelastic interaction of the laser-plasma ions with the macroparticle surface: acceleration due to the ion momentum and reactive acceleration due to evaporation of the surface layer. The processes are mathematically described with the aid of the gasdynamics equations with thermal conductivity. Approximate analytic expressions are obtained and permit an estimate of the laser-plasma energy as well as of the quasiparticle momentum as functions of the parameters of the laser pulse, of the target, and of the macroparticle. The analytic solutions are compared with numerical computations using the RAPID program; the comparison confirms that the results agree qualitatively and quantitatively.

Pulsed ion beams for modification of metal surface properties

A versatile technique using pulsed laser-plasma ion source (PLPIS) was developed for various ion beam treatments of materials (ion implantation, ion beam mixing, and ion beam assisted deposition).

Study of the ion-optical properties of the mass spectrometer Lidia

The ion-optical characteristics of the ultrasensitive mass spectrometer LIDIA designed to search for superheavy elements ( A > 250) with a sensitivity of up to 10 −14 at./at. using a laser plasma ion source and a multistage separation system have been calculated. The main ones (acceptance, momentum dispersion, resolution and line shape) have been measured by means of 249Cf and 226Ra α-particle beams. A good agreement of the obtained results with the calculated ones is shown. The mass spectrometer is made operational with a laser plasma ion source. This will enable one to carry out the mass-spectrometric analyses of natural samples with fairly high utilization of the specimen material (10 −6–10 −3) and wish a resolution sufficient to resolve the mass lines of the superheavy elements searched.

Spectral and mass-spectroscopic investigations of expansion of a laser plasma into a rarefied gas

Spectral and mass-spectroscopic diagnostics were used to investigate expansion and interaction with a rarefied background gas (Xe at a pressure of 10 − 5–10 − 1 Torr) of a laser plasma formed by the interaction of Nd laser pulses (1011 W/cm2) with a plane target made of aluminum. Spectral diagnostics was performed using the line radiation emitted by the laser plasma and by the background (Al III, Al II, Xe II). An investigation was made of the spatial distribution of the laser plasma and background ions and of the influence of charge transfer on this distribution. The spatial distribution of the intensity of the Al II radiation had two maxima corresponding to the front of the Al III ions and the slower Al II component. This behavior of the Al II ions was due to Al2+ + Xe→Al+ + Xe+ charge exchange in the laser plasma front, which was one of the stages of a cascade of charge-transfer transitions involving highly charged Alz+ ions interacting with Xe. Mass-spectroscopic results confirmed fully this scheme of kinetic processes near the laser plasma front.

Trace element analysis by laser plasma mass spectrometry

A double focusing mass spectrometer was equipped with a laser plasma ion source. This instrument has been used for multi-element analysis of solid materials. Laser plasma mass spectrometry (LMS) permits direct analysis of both conducting and non-conducting samples. The abundances of about 30 trace elements can be determined simultaneously in rock samples. A great advantage of LMS is that most elements are ionized with about the same efficiency, this means that only small corrections are necessary for quantitative analysis. Solutions which have been dried on a quartz disk can also be analyzed. This technique yields mass spectra which are free of interferences of molecules or cluster-ions.

Investigation of the formation and flight of silver ions in a multicomponent laser plasma

An investigation was made of the flight of multiply charged silver ions formed from a multicomponent target as a result of exposure to laser radiation of power density q = 109–1012 W/cm2. It was found that the charge number, the intensity of the ion fluxes, and the energy range of their distribution depend not only on q but also on the type of element under study and its concentration in the target.