I. V. Litovko

Role of aberrations in high-current plasma lenses

The influence of spherical and momentum aberrations on the focusing characteristics of intense ion beams in the electrostatic plasma lens (PL) is analyzed. The dependence of the ion beam focus on the uncompensated beam space charge and the finite azimuthal velocity at the PL exit is examined. Minimum focused beam radii are calculated for different system parameters and are shown to depend on the ion charge-to-mass ratio. The radial profiles of focused, multicharged, inhomogeneous ion beams were measured experimentally and compared with the theoretical predictions. We show that the PL, in principle, can be used for ion charge state analysis.

Further development of low noise vacuum arc ion source

Based on the idea of a space-charge-limited mode of operation, the influence of a pair of electrostatic meshes on the beam parameters of the Lawrence Berkeley National Laboratory MEVVA-5 ion source was investigated. The meshes were placed in the expansion zone of the vacuum arc plasma. Apart from reducing the level of beam current fluctuations, this mode of operation provides significant control over the ion charge state distribution of the extracted beam. These effects can be understood taking not only space charge but also the high-directed ion drift velocities, which are the same for different ion charge states of a material, into account. The results of simulations of the processes involved are in good agreement with the experimental results.

Moderate energy metal ion beam focusing by a high-current plasma lens

Some features of the electrostatic plasma lens as applied to the focusing of moderate-energy, high-current, wide-aperture metal ion beams have been investigated and are described here. Static characteristics within the plasma lens volume have been explored. It is shown that when the potentials applied to the lens electrodes are held constant, the electric field increase with increasing ion beam current is limited by the increase of the potential in the paraxial region of the beam. Some estimates are made of the limiting static electric fields that can be obtained in the plasma lens, based on a quasi-neutral, two-component plasma model with anomalous electron mobility, where it is assumed that the anomalous mobility is caused by the absence of electron correlations when vortex-like structures appear in the hydrodynamically unstable plasma. The results of a theoretical analysis are compared with experimental data. Some results of experiments on the focusing of high-current, large area, heavy metal ion beams are also presented.

Recent advances in plasma devices based on plasma lens configuration for manipulating high-current heavy ion beams.

We describe new results of development of novel generation cylindrical plasma devices based on the electrostatic plasma lens configuration and concept of electrons magnetic insulation. The crossed electric and magnetic fields plasma lens configuration provides us with the attractive and suitable method for establishing a stable plasma discharge at low pressure. Using plasma lens configuration in this way some cost-effective plasma devices were developed for ion treatment and deposition of exotic coatings and the effective lens was first proposed for manipulating high-current beams of negatively charged particles. Here we describe operation and features of these plasma devices, and results of theoretical consideration of mechanisms determining their optimal operation conditions.

Electrostatic Plasma Lens Focusing of an Intense Electron Beam in an Electron Source With a Vacuum Arc Plasma Cathode

In this paper, we present the research results on focusing and transport of an intense (up to 100 A) nonrelativistic (up to 20 kV) pulsed electron beam using an axially symmetric device with a high-current plasma lens configuration. The electron source is based on electron extraction from the plasma of a hollow-anode vacuum arc discharge. The arc is initiated by a dielectric surface flashover. The emission hole is covered with a fine mesh grid. The beam is extracted and accelerated in a diode-type electro-optical system formed between the grid surface and an open anode plasma boundary. The anode plasma is produced in an electron beam transport channel through residual gas ionization by beam electrons and a plasma lens discharge. The plasma lens configuration of crossed electric and magnetic fields provides an attractive means to obtain a stable low-pressure plasma discharge. This geometry allows the compression of the electron beam in diameter from 6 to 1 cm with more than 100-

Electrostatic plasma lens for focusing negatively charged particle beams.

{\rm A}/{\rm cm}^{2}

High‐current plasma lens: New results and applications

beam current density at the collector.

Positive-Space-Charge Lens for Focusing and Manipulating High-Current Beams of Negatively Charged Particles

We describe the current status of ongoing research and development of the electrostatic plasma lens for focusing and manipulating intense negatively charged particle beams, electrons, and negative ions. The physical principle of this kind of plasma lens is based on magnetic isolation electrons providing creation of a dynamical positive space charge cloud in shortly restricted volume propagating beam. Here, the new results of experimental investigations and computer simulations of wide-aperture, intense electron beam focusing by plasma lens with positive space charge cloud produced due to the cylindrical anode layer accelerator creating a positive ion stream towards an axis system is presented.

The positive space charge lens for focusing and manipulating high-current beams of negatively charged particles (review)

Influence of spherical and momentum aberrations of the electrostatic plasma lens (PL) on the intense ion beam focusing and maximal compression is investigated experimentally and theoretically. It is shown that when spherical aberrations are absent unavoidable momentum aberrations affect the radial profile of multicharged ion beams. This profile appeared to be steplike. PL electric potential radial profile providing transformation of unhomogeneous (Gauss) profile of a beam at the PL entrance to homogeneous one on the target on the given distance from PL is obtained analytically. High‐current PL efficiency for compensated ion beam setting on the quasi‐Brillouin orbit is demonstrated to be experimentally and theoretically substantiated.

Focusing properties of a permanent magnet plasma lens

We describe a new approach for the creation of effective axially symmetric plasma tools for focusing and manipulating high-current negatively charged particle beams, negative ions, and electrons. This approach is based on the fundamental plasma-optical concept of magnetic and electrostatic insulation of electrons and nonmagnetized positive ions providing controlled uncompensated positive-space-charge cloud formation. The recent advances in the creation of negative ion sources have led to the problem of elaboration and creation of focusing tools capable of manipulating high-current negative ion beams. We describe novel experimental, theoretical, and computer simulation results of the application of the magnetic electron insulation concept for the creation of the positive-space-charge electrostatic plasma lens. The described results open up an attractive possibility to use this lens for focusing high-current negative ion beams.