High-density Beam Research Articles

Modelización de la energía absorbida en la fusión de un metal por un haz láser

The interaction between a high-density laser beam and a metallic surface produces a deep and narrow melted area that has a characteristic keyhole geometric pattern. The amount of energy absorbed by the metal will depend on the parameters of the laser beam being applied, and the nature and geometry of the piece. In this paper, a formulation is presented which makes it possible to quantitatively determine the amount of energy absorbed by the metal as a function of a series of experimental parameters. The formulation that has been developed is especially applicable in beadon-plate tests commonly used to analyze laser-metal interactions in laser technology research. The formulation applies specifically to two types of aluminium alloys, Al-Mg-Si and Al-Zn-Mg.

Diamond nucleation on nonscratched Si substrate pretreated by pulsed high-temperature and high-density CH4-plasma beam

While great interest has been focused on low-temperature plasma chemical vapor deposition, the pulsed high-temperature and high-density plasma beam was utilized to enhance diamond nucleation on Si substrate without damaging the smoothness of Si surface, and a nucleation density up to 109 cm−2 was obtained. Scanning electron microscopy, atomic force microscopy, x-ray photoelectron spectroscopy, and transmission electron microscopy results indicated that after pretreated by this high power CH4 plasma, an amorphous modified layer rich in sp3-hybridized carbon was formed on the Si surface. This layer was believed to provide large amounts of nucleation sites for diamond.

Intensity effects on inverse-bremsstrahlung electron acceleration

The effects of beam intensity on the laser field on inverse-bremsstrahlung electron acceleration are investigated. A self-consistent Hamiltonian formalism that takes into account both particles and wave dynamics is developed. It is shown that efficient acceleration is achieved for high-density beams. However, for such high densities, beam plasma effects impose a limitation on energy gain. A method is proposed in order to remove the limiting effects. {copyright} {ital 1998} {ital The American Physical Society}

Diamond nucleation using a pulsed high-temperature and high-density CH4-plasma beam

Diamond nucleation using a pulsed high-temperature and high-density CH4-plasma beam

Virtual Anode in Ion Beam Emissions in Space: Numerical Simulations

The plasma interactions associated with the emission of an unneutralized ion beam in space are discussed. Three-dimensional particle simulations, which follow the beam ions as well as the ambient electrons and ions in the self-consistent electric e eld, are performed for various emission conditions. Classical theories and laboratory experiments for one-dimensional beam e ow in diodes have shown that a potential hump will form when the beam current density exceeds a critical value. When the potential hump becomes so high that the beam kinetic energy is near zero there, it becomes a virtual electrode. We show that similar characteristics are also exhibited in high-density ion beams emitted from spacecraft to space plasma, although three-dimensional effects and the ambient plasma make the interaction more complex. Once a virtual anode has formed, it will partly block the beam transmission and discharge the spacecraft potential.

Ion implantation modification of special steels in Thailand

Various ion implantation methods, including using focused high-density and scanning beams, mixing B-ions to implanted N-ion layers and assisting normal N-ion implantation with both preparative and closing implantations, have been recently developed for modification of special steels in the ion beam center at Chiang Mai University in Thailand. Tool, machinery and structural steel samples in a hardened or unhardened state have been ion-beam-treated. Experimental evidence shows increases in microhardness and improvements in wear resistance for the implanted steels and some particularly impressive modifications. Comparisons are made for ion implantation effects on the tribological property modification of the hardened and unhardened steels between wear conditions of hard ball with heavy load and soft ball with light load. The results indicate that scanning high-density beam N-ion implantation has a potential in strengthening hardened steels, but with a dependence on the Cr as well as C contents, and additional B-ion implantation and multiple N- and B-ion implantation can also effectively strengthen the hardened steels.

The investigation of nuclear structure with storage rings — present and future

Heavy-ion cooler and storage rings offer a rich field of new and unique possibilities to study nuclear structure. Cooling creates beams of high phase space density for high-resolution experiments. In first experiments atomic masses of more than hundred new nuclides were measured with high precision. Future experiments with cooled energetic beams of exotic nuclei allow high precision nuclear structure studies in direct reactions such as (d, p), (p, p′), or Coulomb breakup. The extension of these investigations to electron scattering in a heavy-ion-electron collider will be discussed.

Interaction Between High-Density Beams of Charged Particles

Interaction Between High-Density Beams of Charged Particles

A Cost-Effective Method for Ultrasound Volumetric Imaging

A synthetic receive aperture technique is explored for cost-effective ultrasound scanners with high frame rates and beam density. The technique provides ultrasound volumetric imaging where beam count is very large with 2-D transducer arrays using subaperture processing. For every beam line, transmit beam is performed with a small subaperture whereas the reflected echo signals are received from non-overlapping subapertures. For every transmit-receive subaperture combination, a small number of beams are acquired and then the number of beam lines is increased through beam space interpolation. A 2-D linear filter with a different spatial frequency band for each subaperture is employed as the interpolation filter. Performance of the technique is analyzed through simulations. The technique reduces the number of firings and therefore allows real-time imaging with very low susceptibility to motion artifacts.

Deposition of diamond-like carbon films on an iron substrate by a pulsed high-density plasma beam at room temperature

Diamond-like carbon (DLC) films were produced on the surface of a pure iron substrate at room temperature using a pulsed high-density plasma beam from a coaxial plasma gun. DLC films have a wide mixing interlayer with substrates, which can improve their adhesion to the substrates. The plasma density ranged between 1014 and 1016 cm−3, the plasma electron temperature was 10–50 eV, the mean plasma speed 30–50 km s−1, and the pulse width about 60 μs. Hardness and thickness measurements, a scratch tester, Raman spectroscopy, Auger electron spectroscopy, and X-ray diffraction were used to characterize the DLC films.

Review of high brightness ion sources for microlithography (invited)

The state of the art of high brightness ion beam production for microlithography and trends of research and development in this field of activity is reviewed. High brightness and low-energy spread are crucial to the success of ion-beam lithography. Features of field emission liquid metal, melted dielectric, and cryogenic gaseous ion sources for fine focused beam production are discussed. Growth of energy spread and the drop in brightness by intrabeam interaction of ions are estimated. Limitation of positive ion-beam characteristics in plasma sources such as duoplasmatron, multicusp, rf, and microwave discharges sources are examined. Features of negative ion formation in surface plasma sources with cesium catalysis are discussed. Possibilities for ions cooling down to 1 eV in high-density beams are estimated. High-precision beam diagnostics will be discussed.

Production of Ultrabright Slow Atomic Beams Using Laser Cooling

We propose to use a three-step transverse and longitudinal cooling scheme, to compress and collimate a strongly diverging flow of metastable rare gas atoms. Simulations show that an atom beam flux of 1010 8−1 in a small diameter (−1 ) atomic beam could be achieved. This technique can be extremely valuable in many areas of atomic physics, e.g. in (electron) spectroscopy and atomic collision physics where high beam densities are desirable.

High-resolution and high-sensitivity instrumentation for detection of visible-ultraviolet luminescence from products of core-hole decay

High-resolution and high-sensitivity instrumentation has been designed and assembled for the study of vibrationally- and rotationally-resolved luminescence from products of core-hole decay in molecules. The luminescence is produced by the interaction of a high-density molecular beam with either high-energy electrons or with monochromatic synchrotron radiation and is detected by a large-aperture 1-m spectrograph equipped with an intensified photodiode array.

Production of High-Density Plasmas in Electron-Beam-Excited Plasma Device

We tried to enlarge the diameter of high-density beam plasmas in an electron-beam-excited plasma (EBEP) device. In order to enlarge the beam plasma, we made a cusp configuration at the end of the ion source region in the EBEP device. Also, a surface confined ring with permanent magnets called “surmac” was mounted on the cusp center to make the plasma profiles flat. It was found that high electron density (7×1011 cm-3) and uniformity (ΔN e/N e<4% over 6 cmφ) could be obtained at low pressure (7×10-4 Torr).

Nonlinear properties of the Kapchinskij-Vladimirskij equilibrium and envelope equation for an intense charged-particle beam in a periodic focusing field.

The nonlinear properties of the Kapchinskij-Vladimirskij (KV) equilibrium and envelope equation are examined for an intense charged-particle beam propagating through an applied periodic solenoidal focusing magnetic field, including the effects of the self-electric and self-magnetic fields associated with the beam space charge and current. It is found that the beam emittance is proportional to the maximum canonical angular momentum achieved by the particles within the KV distribution. The Poincare mapping technique is used to determine systematically the axial dependence of the radius of the matched (equilibrium) beam and to study nonlinear behavior in the nonequilibrium beam envelope oscillations. It is shown that the nonequilibrium beam envelope oscillations exhibit nonlinear resonances and chaotic behavior for periodic focusing magnetic fields and sufficiently high beam densities. Certain correlations are found between the nonlinear resonances and well-known instabilities for the KV equilibrium. It is also shown, in agreement with previous studies, that there exists a uniquely matched beam in the parameter regime of practical interest, i.e., [sigma][sub 0][lt]90[degree], where [sigma][sub 0] is the vacuum phase advance over one axial period of the focusing field. The nonlinear resonances and chaotic behavior in the nonequilibrium beam envelope oscillations may play an important role in mismatched ormore » multiple beam transport, including emittance growth and beam halo formation and evolution.« less

Space-charge and axial-field effects in a free-electron laser with an axial-guide magnetic field

Space-charge and axial-field effects are discussed for a free-electron laser with an axial-guide magnetic field. It is found that the maximum gain increases with the beam density and gain saturation occurs for high beam density. The laser frequency is upshifted and downshifted in the low and high density cases respectively. The regimes which permit the amplifying effect of the guide field and the stabilities of both the electron trajectories and the electrostatic mode are found. The maximum amplifying coefficient of the guide field is also obtained by using the stability conditions.

Nonlinear theory of scattering of linearly polarized electromagnetic waves by unmagnetized electron beam

The nonlinear dynamics of scattering of linearly polarized electromagnetic waves by an unmagnetized beam of nonrelativistic electrons is studied. General nonlinear equations are derived and linear scattering regimes are analyzed. For the case of high-density beams, the general nonlinear equations are reduced to a system containing only cubic nonlinearities. Analytic expressions are provided for the amplitudes of interacting waves and for typical process-development times.

Multi-Turn Electron-Ion Injection Study for Neutralized High-Density Beam Sustaining in a Closed Configuration

The problem of creating a high-density, high-current neutralized beam in a closed configuration via a continuous particle injection and accumulation has been considered in relation to the research ...

Size selection and focusing of neutral carbon clusters

A new method is proposed for producing a high-density beam of size-selected neutral clusters of metal or semiconductor materials. This method is based on photodetachment of negative cluster ions, size-selected and then tightly focused by two sets of einzel lens systems. This method was shown to focus the size-selected neutral cluster of C 10 beyond the limit of the “space charge” effect observed in the beam profile of C − 10.

Chaotic particle dynamics in free-electron lasers

The motion of a relativistic test electron in a free-electron laser can be altered significantly by the equilibrium self-field effects produced by the beam space charge and current and by the transverse spatial inhomogeneities in a realizable magnetic wiggler field. In a field configuration consisting of an ideal (constant-amplitude) helical-wiggler field and a uniform axial-guide field, it is shown in a model that the inclusion of self-field effects destroys the integrability of the particle equations of motion. Consequently, the group-I orbits and the group-II orbits become chaotic at sufficiently high beam density. An analytical estimate of the threshold value of the self-field parameter ${\mathrm{\ensuremath{\epsilon}}}_{\mathit{s}}$=${\mathrm{\ensuremath{\omega}}}_{\mathit{p}\mathit{b}}^{2}$/${\mathit{c}}^{2}$${\mathit{k}}_{\mathit{w}}^{2}$ for the onset of chaos is obtained and found to be in good agreement with computer simulations. In addition, the effects of transverse spatial gradients in a realizable helical-wiggler field with three-dimensional spatial variations are investigated in the absence of an axial-guide field, but including self-field effects. For a thin electron beam (${\mathit{k}}_{\mathit{w}}^{2}$${\mathit{r}}_{\mathit{b}}^{2}$\ensuremath{\ll}1) and small wiggler field amplitude (${\mathit{a}}_{\mathit{w}}^{2}$\ensuremath{\ll}${\ensuremath{\gamma}}_{\mathit{b}}^{2}$), it is shown that the motion is regular and confined radially provided ${\mathrm{\ensuremath{\epsilon}}}_{\mathit{a}}$${\ensuremath{\gamma}}_{\mathit{b}}$${\mathit{a}}_{\mathit{w}}^{2}$/(1+${\mathit{a}}_{\mathit{w}}^{2}$). However, because of the intrinsic nonintegrability of the motion, the regular region in phase space diminishes in size as the wiggler amplitude is increased. The threshold value of the wiggler amplitude for the onset of chaos is estimated analytically and confirmed by computer simulations for the special case where self-field effects are negligibly small. Moreover, it is shown that the particle motion becomes chaotic on a time scale comparable with the beam transit time through a few wiggler periods.