Beam voltage and current parameter study for the autoresonant acceleration proof-of-principle experiment

Due to flashover problems, Austin Research Associates, Inc. may be forced to perform its proof-of-principle autoresonant collective ion acceleration experiment at electron beam parameters of 2.25 MeV and 15 kA rather than the intended 3.0 MeV and 30 kA. We show that the original experimental goals still can be achieved provided the beam radius is reduced by a factor of two and a thinner anode foil is employed. More generally, our parameter study suggests that operating with beams of smaller radii improves cyclotron wave behavior during beam adiabatic compression or expansion

Plasma source ion implantation research and applications at Los Alamos National Laboratory

Plasma Source Ion Implantation research at Los Alamos Laboratory includes direct investigation of the plasma and materials science involved in target surface modification, numerical simulations of the implantation process, and supporting hardware engineering. Target materials of Al, Cr, Cu-Zn, Mg, Ni, Si, Ti, W, and various Fe alloys have been processed using plasmas produced from Ar, NH{sub 3}, N{sub 2}, CH{sub 4}, and C{sub 2}H{sub 2} gases. Individual targets with surface areas as large as {approximately}4 m{sup 2}, or weighing up to 1200 kg, have been treated in the large LANL facility. In collaboration with General Motors and the University of Wisconsin, a process has been developed for application of hard, low friction, diamond-like-carbon layers on assemblies of automotive pistons. Numerical simulations have been performed using a 2{1/2}-D particle- in-cell code, which yields time-dependent implantation energy, dose, and angle of arrival for ions at the target surface for realistic geometries. Plasma source development activities include the investigation of pulsed, inductively coupled sources capable of generating highly dissociated N{sup +} with ion densities n{sub i} {approximately} 10{sup 11}/cm{sup 3}, at {approximately}100 W average input power. Cathodic arc sources have also been used to produce filtered metallic and C plasmas for implantation and deposition either in vacuum, or in conjunction with a background gas for production of highly adherent ceramic coatings

New initiatives for producing high current electron accelerators

New classes of compact electron accelerators able to deliver multi-kiloamperes of pulsed 10-50 MeV electron beams are being studied. One class is based upon rf linac technology with dielectric-filled cavities. For materials with {epsilon}/{epsilon}{sub o}>>1, the greatly increased energy storage permits high current operation. The second type is a high energy injected betatron. Circulating current limits scale as {Beta}{sup 2}{gamma}{sup 3}

Preliminary considerations concerning neutral plasma beam propagation across a magnetic field

A plan to address physical questions of interest for exoatmospheric military applications of intense neutralized plasma beams is described. After a brief review of earlier work relevant to this matter and a detailed explanation of why such work cannot answer questions of present interest, a plan employing interactive application of several numerical and analytic techniques to treat relevant phenomena occurring on the various rather disparate time and length scales involved is suggested. The first part of the study would determine the macroscopic features of beam propagation through calculations effected with a magnetohydrodynamical numerical code. Classical transport coefficients would be employed in this initial phase. Using information thus gained concerning gross charge and current distributions, particle-in-cell simulations would be initialized to study those microscopic, phase-space-dependent phenomena which can alter the phenomonological transport coefficients appearing in the fluid description. Insight thereby gained concerning anomaous, collectively induced transport effects would then be applied to yield a refined, accurate description of the macroscopic aspects of neutral plasma beam propagation. Personnel and computational resources available at the Los Alamos Scientific Laboratory are described. Results of a very preliminary particle-in-cell simulation of a neutral plasma beam propagating across a magnetic field are presented

Key issues in plasma source ion implantation

Plasma source ion implantation (PSII) is a scaleable, non-line-of-sight method for the surface modification of materials. In this paper, we consider three important issues that should be addressed before wide-scale commercialization of PSII: (1) implant conformality; (2) ion sources; and (3) secondary electron emission. To insure uniform implanted dose over complex shapes, the ion sheath thickness must be kept sufficiently small. This criterion places demands on ion sources and pulsed-power supplies. Another limitation to date is the availability of additional ion species beyond B, C, N, and 0. Possible solutions are the use of metal arc vaporization sources and plasma discharges in high-vapor-pressure organometallic precursors. Finally, secondary electron emission presents a potential efficiency and x-ray hazard issue since for many metallurgic applications, the emission coefficient can be as large as 20. Techniques to suppress secondary electron emission are discussed

On the use of intense ion beams for generating magnetized target fusion plasma

Magnetized Target Fusion (MTF) is a concept for creating a burning D-T plasma in a potentially inexpensive system. In essence, the concept involves ion heating on time scales short compared to ion transport times plus strong inhibition of thermal electron transport with a transverse magnetic field. The magnetic field is not intended to confine the ionic component. MTF is an intrinsically pulsed concept. A straightforward analysis of MTF indicates that D-T burning conditions can be achieved in compact plasma volumes with modest initial temperatures, through the use of pulsed power technology. In terms of size, density, temperature, and time scales, MTF occupies a position in phase space that is intermediate between steady MFE schemes and ICF. In terms of cost, it is one to two orders of magnitude less expensive than these. In this paper, the authors consider a possible method for creating the initial conditions adequate for the MTF concept through the use intense ion beam injection

Experimental investigations of interaction of supercritical electron beams with plasma

The first section of the collective ions acceleration based on simultaneous temporal and spatial modulation of relativistic electron beam (REB) was studied experimentally. The virtual cathode was originated in the electrodynamic structure consisting of two tubes with different diameters (jump of electrodynamics) by REB, produced in magnetically insulated diode. At plasma assistance the low-frequency oscillations of REB current and the low-frequency microwave radiation were obtained due to the virtual cathode periodical relaxation in the processes of charge compensation by ionized residual gas

Low-frequency REB modulation and acceleration of ions in a supercritical mode during plasma injection

Low-frequency modulation of a high-current relativistic electron beam (REB) and acceleration of ions in the first section of a collective ion accelerator was studied experimentally. Low frequency modulation of supercritical high-REB was obtained due to periodic compensation of a virtual cathode charge by plasma ions. An ion flow was produced by an electric field of virtual cathode when plasma assists. Plasma was formed by the four Bostick plasma guns placed at equal distances along the periphery of the drift chamber. The low-frequency modulation with depth 10 % at frequency 46 MHz was obtained. The ion energy was measured using the magnetic analyzer. The ion energy that probably was obtained in the potential well of the virtual cathode exceeded the REB energy.Експериментально досліджена низькочастотна модуляція сильнострумового релятивістського електронного пучка (РЕП) та прискорення іонів в першій секції двохсекційного колективного прискорювача іонів. Низькочастотна модуляція надкритичного сильнострумового РЕП здійснена періодичною компенсацією віртуального катода іонами плазми. Іонний потік сформований електричним полем віртуального катода. Плазма створена чотирма плазмовими пушками бостіковського типу, розміщеними рівномірно по периферії камери дрейфу в області віртуального катода. Модуляція РЕП з глибиною 10% реалізована на частоті 46 МГц. Енергія іонів виміряна за допомогою магнітного аналізатора. Енергія іонів, яка ймовірно отримана в потенційній ямі віртуального катоду, перевищила енергію РЕП.Экспериментально исследована низкочастотная модуляция сильноточного релятивистского электронного пучка (РЭП) и ускорение ионов в первой секции двухсекционного коллективного ускорителя ионов. Низкочастотная модуляция сверхкритического сильноточного РЭП осуществлена периодической компенсацией виртуального катода ионами плазмы. Ионный поток сформирован электрическим полем виртуального катода. Плазма образована четырьмя плазменными пушками бостиковского типа, расположенными равномерно по периферии камеры дрейфа в области виртуального катода. Модуляция РЭП с глубиной 10% осуществлена на частоте 46 МГц. Энергия ионов измерена с помощью магнитного анализатора. Энергия ионов, которая возможно получена в потенциальной яме виртуального катода, превысила энергию РЭП

Role of surface roughness in hard x-ray emission from femtosecond laser produced copper plasmas

The hard x-ray emission in the energy range of 30-300 keV from copper plasmas produced by 100 fs, 806 nm laser pulses at intensities in the range of 10$^{15}-10^{16}$ W cm$^{-2}$ is investigated. We demonstrate that surface roughness of the targets overrides the role of polarization state in the coupling of light to the plasma. We further show that surface roughness has a significant role in enhancing the x-ray emission in the above mentioned energy range.Comment: 5 pages, 4 figures, to appear in Phys. Rev.

Preliminary simulation studies of accelerator cavity loading

Two-dimensional simulations of loading effects in a 350 MHz accelerator cavity have been performed. Electron currents of 1-10 kA have been accelerated in 5 MV/m fields. Higher order cavity modes induced by the beam may lead to emittance growth. Operation in an autoaccelerator mode has been studied