1. Introduction

The electrostatic plasma lens (PL) is a well-investigated tool for focusing and manipulating large area, high-current, moderate energy ion beams, where the concern of beam space charged compensation is critical. The fundamental concept of the PL was first described by Morozov [1]. It is based on application of the plasma-optical principles of magnetic insulation of electrons and equipotentialization of magnetic field lines for the control of electric fields introduced into the plasma medium [2].

© 2016 The Author(s). Licensee InTech. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and eproduction in any medium, provided the original work is properly cited. © 2018 The Author(s). Licensee IntechOpen. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

These kinds of devices are part of a larger sort of plasma devices (plasma accelerators, ion magnetrons, thrusters, plasma lenses, etc.) that use a discharge in crossed electric and magnetic fields with closed electron drift for the generation, formation, and manipulation of intense ion beams and ion plasma flows. In accordance with the basic idea of plasma optics [1], spatial over thermal E-fields can be introduced in the plasma medium of an intense ion beam, which makes possible high-current ion beams manipulation and focusing including beams of heavy ions. An idea to use the space charge for that purpose appeared to be very fruitful and successful [2, 3]. A number of effective plasma lenses for positive ion beams focusing were made and tested. The robust construction, low-energy consumption, and high-cost-effectiveness make these tools attractive for practical applications.

2. Plasma lens with a positive space charge cloud for focusing intense

Modeling of Novel Plasma-Optical Systems http://dx.doi.org/10.5772/intechopen.77512 269

The plasma lens is a cylindrical plasma accelerator with an anode layer and used as a device with magnetic insulation of electrons for creation of the dynamic cloud of positive space charge. The scheme of the plasma lens with magnetic insulation used for creation of the

The lens has a system of permanent magnets that produce an axially symmetric magnetic field between the poles of a magnetic circuit serving as cathode. The magnetic field is controlled by varying the number of magnets. The magnetic field configuration is typical for the single magnetic lens configuration, because of the lens could focus the transported electron beams. When a positive potential is applied to the anode, a discharge in the axial magnetic, and radial electric crossed fields is ignited between the anode and the cathode. The electrons are magnetized in anode layer and drift along closed trajectories in the azimuthal direction, repeatedly ionize atoms of the working gas, and gradually diffuse to the anode. The ions thus formed are accelerated in the strong electric field created by the electron space charge and leave the ion source through a hole in the acceleration channel. The fast ions reach the system axis and accumulate in the region around it, as it schematically shown in Figure 1b. In this way, the axially converging ion beam creates a positive space charge. In the experiments, the energy of the argon ions converging beam could reach 2.5 kV. Maximum potential will be in the center on cylindrical axis. Ions are stored in the cylinder volume until their own space charge creates a critical electric field. This field forces ions to leave the volume, and the system comes to dynamic equilibrium after some relaxation time.

Electrons are magnetized in the anode layer, so their influence on ion dynamics can be neglected. The ion flow coming through the cylindrical surface will be equal to ions streaming down from the axis and leaving the cylindrical volume under action of the Coulomb force of their own space charge. Therefore, the set of equations describing this process in the cylindrical

Figure 1. (a) Scheme of the plasma lens with magnetic electron insulation: 1 – cathode; 2 – anode; 3 – magnetic system

based on permanent magnets; (b) Scheme the positive space charge cloud creation.

negative charged particle beams

dynamic cloud of positive space charge is shown in Figure 1a.

2.1. Model description

Some new ideas for using these plasma-optical principles for creation axial symmetric highcurrent mass separation devices were described firstly in [4]. Note also that this approach is appropriate for the creation of linear or curved magneto-electrostatic plasma guiding ducts for use in vacuum-arc plasma filtering system. Following these plasma-optical principles, changing the magnetic field line configuration and the distribution of electric potential enables the formation and control of high-current ion beams while maintaining their quasi-neutrality. This makes the application of such devices attractive for the manipulation of high-current beams of heavy ions.

The plasma lens configuration of crossed electric and magnetic fields provides a suitable and attractive method for establishing a stable discharge at the low-pressure. Using plasma lens configuration in this way were elaborated, explored and developed some cost efficiency, low-maintenance plasma devices for ion treatment, and deposition of exotic coatings with given functional properties. These devices make using of permanent magnets and possess considerable flexibility with respect to spatial configuration. They can be operated as a stand-alone tool for ion treatment of substrates, or as part of integrated processing system together with cylindrical magnetron sputtering system, for coating deposition. The cylindrical plasma-optical magnetron sputtering device with virtual anodes and cylindrical plasma production device for the ion treatment of substrates with complicated cylindrical was proposed and created [5–7]. These devices can be applied both for fine ion cleaning and activation of substrates before deposition and for sputtering.

One particularly attractive result of this background work was observation of the essential positive potential at the floating substrate treated by cylindrical ion cleaning device. This suggested to us the possibility of an electrostatic plasma lens for focusing and manipulating high-current beams of negatively charged particles (electrons and negative ions) that is based on the use of the cloud of positive space charge in conditions of magnetic insulation electrons. The idea of the plasma lens based on electrostatic electron isolation for creation positive space charge was first proposed in [8]. Later, it was proposed to use magnetic electron insulation for creation of a stable positive space charge cloud [9].

Here we describe computer modeling for some of these novel plasma-optical systems.
