Production Of Intense Ion Beams Research Articles

Production of Intense Ion Beams of Nickel, Chromium, Silicon, and Cobalt at the DC-60 Cyclotron

This article describes experiments for producing highly intense metal ion beams at the ECR source of the DC-60 cyclotron using the evaporation of organometallic compounds by the MIVOC method. As a result of the works, beams of nickel, cobalt, chromium, and silicon ions are obtained. The optimization of modes of acceleration for the ion beams to an energy of 1.75 MeV/n is carried out.

Production of Intense Ion Beams of Boron and Iron Using the MIVOC Method from ECR Ion Source on the DC-60 Cyclotron

This article describes experiments carried out in 2017–2018 at the DC-60 accelerator complex (Astana branch of the Institute of Nuclear Physics, Almaty, Kazakhstan) to develop methods for producing intense beams of multicharged iron and boron ions with the use of volatile organometallic compounds (Metal Ions from Volatile Compounds (MIVOC)). Beams of iron and boron ions were obtained for the first time on the DC-60 cyclotron, and the acceleration modes of 56Fe10+ and 11B2+ ions were optimized to energies of 1.75 and 1.5 MeV/n, respectively.

Overdense plasma generation in a compact ion source

Electron cyclotron resonance ion sources (ECRIS) are widely used plasma based machines for the production of intense ion beams in science and industry. The performance of modern devices is limited by the presence of the density cut-off, above which electromagnetic (EM) waves sustaining the plasma are reflected. We hereby discuss the systematic data analysis of electrostatic wave generation in an ECR prototype operating at 3.75 GHz–0.1 THz. In particular, electron Bernstein waves (EBW) have been excited. EBW have already been generated in large-scale plasma devices for thermonuclear fusion purposes. In ion sources where Lc ∼ λRF (Lc being the plasma chamber size and λRF the pumping wave wavelength) the EM field assumes a modal behaviour; thus both plasma and EM field self-organize so that no optical-like wave launching is possible (i.e. the cavity effect dominates on the optical path). The collected data, however, supported by 3D full-wave simulations, actually demonstrate that a Budden-type X-B conversion scenario can be established above some critical RF power thresholds, operating in an off-ECR regime. The generation and absorption of the EBW has been demonstrated by the presence of three peculiar signatures: along with the establishment of an overdense plasma, generation of supra-thermal electrons and modification (non-linear broadening) of the EM spectrum measured within the plasma have been observed. At the threshold establishing such a heating regime, the collected data provide evidence for a fast rotation of the electron fluid.

Enhanced efficiency of plasma acceleration in the laser-induced cavity pressure acceleration scheme

Among various methods for the acceleration of dense plasmas the mechanism called laser-induced cavity pressure acceleration (LICPA) is capable of achieving the highest energetic efficiency. In the LICPA scheme, a projectile placed in a cavity is accelerated along a guiding channel by the laser-induced thermal plasma pressure or by the radiation pressure of an intense laser radiation trapped in the cavity. This arrangement leads to a significant enhancement of the hydrodynamic or electromagnetic forces driving the projectile, relative to standard laser acceleration schemes. The aim of this paper is to review recent experimental and numerical works on LICPA with the emphasis on the acceleration of heavy plasma macroparticles and dense ion beams. The main experimental part concerns the research carried out at the kilojoule sub-nanosecond PALS laser facility in Prague. Our measurements performed at this facility, supported by advanced two-dimensional hydrodynamic simulations, have demonstrated that the LICPA accelerator working in the long-pulse hydrodynamic regime can be a highly efficient tool for the acceleration of heavy plasma macroparticles to hyper-velocities and the generation of ultra-high-pressure (>100 Mbar) shocks through the collision of the macroparticle with a solid target. The energetic efficiency of the macroparticle acceleration and the shock generation has been found to be significantly higher than that for other laser-based methods used so far. Using particle-in-cell simulations it is shown that the LICPA scheme is highly efficient also in the short-pulse high-intensity regime and, in particular, may be used for production of intense ion beams of multi-MeV to GeV ion energies with the energetic efficiency of tens of per cent, much higher than for conventional laser acceleration schemes.

Plasma Ion Source with an Internal Evaporator

A new construction of a hollow cathode ion source equipped with an internal evaporator heated by a spiral cathode filament and arc discharge is presented. The source is especially suitable for production of ions from solids. The proximity of arc discharge region and extraction opening enables production of intense ion beams even for very low discharge current (Ia = 1:2 A). The currents of 50 „A (Al + ) and 70 „A (Bi + ) were obtained using the extraction voltage of 25 kV. The source is able to work for several tens of hours without maintenance breaks, giving possibility of high dose implantations. The paper presents the detailed description of the ion source as well as its experimental characteristics like dependences of extracted currents and anode voltage on anode and cathode currents.

Versatile plasma ion source with an internal evaporator

A novel construction of an ion source with an evaporator placed inside a plasma chamber is presented. The crucible is heated to high temperatures directly by arc discharge, which makes the ion source suitable for substances with high melting points. The compact ion source enables production of intense ion beams for wide spectrum of solid elements with typical separated beam currents of ∼100–150 μA for Al +, Mn +, As + (which corresponds to emission current densities of 15–25 mA/cm 2) for the extraction voltage of 25 kV. The ion source works for approximately 50–70 h at 100% duty cycle, which enables high ion dose implantation. The typical power consumption of the ion source is 350–400 W. The paper presents detailed experimental data (e.g. dependences of ion currents and anode voltages on discharge and filament currents and magnetic flux densities) for Cr, Fe, Al, As, Mn and In. The discussion is supported by results of Monte Carlo method based numerical simulation of ionisation in the ion source.

Development of external electron-beam enhancement of the Penning ionization gauge ion source

To study the injection of additional electrons from an external electron gun into the plasma of a Penning ionization gauge (PIG) ion source, a test bench for the external electron-beam enhancement of the PIG (E-PIG) ion source was set up. A source magnet assembly was built to satisfy the request for magnetic field configuration of the E-PIG ion source. Numerical calculations have been done to optimize the magnetic field configuration so as to fit the primary electrons to be fed into the PIG discharge chamber along the spreading magnetic field lines. Many possible methods for improving the performance and stability of the PIG ion source have been used in the E-PIG ion source, including the use of multicrystal LaB6 cathode and optimized axial magnetic field. This article presents a detailed design of the E-PIG ion source. Substantial enhancement of ion charge state is expected to be observed which demonstrates that the E-PIG is a viable alternative to other much more costly and difficult to operate devices for the production of intense ion beams of higher charge state.

Flashback and perspectives for the production of intense ion beams with ECR ion sources

There is a clear evidence that the combination of ability to produce intense beams of highly charged heavy ions and of reliability, stability and low emittance can be guaranteed only by an adequate design of electron cyclotron resonance ion sources (ECRIS). Following the roadmap defined by Geller's scaling laws (1987) and the high B-mode concept (1990), the evolution of ECRIS has been steady and it amounted to about one order of magnitude per decade, as for high charge state currents. A further increase is possible according to the standard model of ECR sources unless technological problems may limit it in the future. Some sources are in the commissioning or construction phase to get the milliampere level for highly charged heavy ions, and some limitations have been already found but the possibility to get a further step forward remains unchanged. This paper presents the flashbacks of previous relevant experiences, along with the perspectives for higher current production in the years after 2010.

Production of intense beams of fission fragments at MAFF

At the new Munich high flux reactor FRM-II, the Munich Accelerator for Fission Fragments (MAFF) is under development. The main objective will be the production and study of new very heavy elements (Z>100). To obtain this goal, intense beams of neutron rich isotopes (70<A<160) are required. Thermal neutron induced fission is considered the most suitable method to produce these isotopes due to the large fission cross section and high thermal neutron flux (>1014 n/s*cm2) available at the new reactor. The target ion source design is based on the ANUBIS source at OSIRIS in Studvik, optimized for very high neutron fluxes. Using 1 g of U235 diluted in a graphite target, intensities of several 1011 ions/s for Kr91, Sn132, or Cs144, e.g., are expected after mass separation. These singly charged ions will be charge bred in an electron cyclotron resonance ion source and then injected into the MAFF-LINAC to reach the energies at the Coulomb barrier. The production of intense ion beams of neutron rich isotopes by thermal neutron induced fission, the development of the target ion source, and the development of the fission target will be presented.

The use of intense ion beams for heating long ϑ-pinch plasmas to thermonuclear temperatures

Motivated by recent advances in the production of intense ion beams, we consider the possible utility of such beams for heating a long thin ϑ-pinch plasma to thermonuclear temperatures. It is found that ion beams offer an alternative to previously proposed schemes utilizing CO2 laser beams and intense relativistic electron beams.

Theory of intense ion beam acceleration

The application of high voltage pulse power techniques to the production of intense ion beams is of great interest for plasma confinement, plasma heating, and pellet implosion. The main problem is that application of a high voltage to a simple anode–cathode gap will draw both an electron current from the cathode and an ion current from the anode, and the electrons will receive most of the input energy due to their smaller mass. Two methods of efficient intense ion beam production are considered: (1) the magnetically insulated diode and (2) the ’’reflex-triode’’. The relativistic equilibria, the ion current dependence on accelerating voltage, its dependence on applied magnetic field (in the first method), and its variation due to a velocity distribution of the electrons (in the second method) are determined. For both methods the ion current can be substantially enhanced with respect to the Langmuir–Child current due to the presence of the negative electron space charge. In the case of magnetic insulation this enhancement increases as the magnetic field is lowered and diverges as it approaches the critical value past which electrons can traverse the gap. For the reflex triode the enhancement is increased by relativistic electron effects and by a population of electrons with energies less than the full voltage across the gap.

The theory of the production of intense ion beams in the relativistic diode

Ions are considered to be generated within the diode either by laser ablation of the anode surface or through electron-neutral collisions taking place in front of the anode. Calculations are carried out for anode potentials up to 10 MV, and it is shown that the allowed ion currents can be several multiples of the Child-Langmuir limit. For both techniques of ion generation the optimum electron current required for space-charge neutralization can be readily produced by field emission, since the cathode electric field can exceed the space-charge-free value.

Production of intense ion beams by high-frequency electric fields

We present an experimental investigation of electron cyclotron resonance plasma accelerators as a source of high-intensity, low-energy (keV) ions in which ion current and electron and ion energies are related to r.f. power and gas pressure.

The Production of Intense Ion Beams in a Mass Spectrometer

A simple 60° mass spectrometer has been built for the production of intense ion beams. Ions are produced by allowing an electron beam collimated by a transverse magnetic field to bombard the vapor issuing from a furnace. By adjusting conditions properly an arc may be struck and total ion currents of 1 to 2 ma could be obtained from the source when the accelerating voltage applied was 15 kev. The collected isotopes were completely resolved, and a total current of 0.3 ma for the several isotopes at the final collector was observed. Because of gas focusing at the operating pressure, space charge effects did not seriously affect the resolution and a resolving power of 1/100 could be obtained. In a 14-hr. run 6.5 mg of separated zinc isotopes were collected. Preliminary results with magnesium, as well as other solids, indicated that many other substances could be separated without modifying the apparatus. Improvements which would permit higher yields are suggested.