Transport Of High-current Electron Beams Research Articles

High-Current Electron-Beam Transport in the LIA-5 Linear Induction Accelerator

The issue of high-current electron-beam transport in the LIA-5 accelerator is discussed. The results of numerical simulation of beam transport in the 15-m-long LIA-5 accelerator channel are presented. The ASTRA macroparticle (PIC) code and two codes developed at the Budker Institute of Nuclear Physics (a code based on the solution of the Kapchinsky–Vladimirsky system of equations (K–V envelope code) and the UltraSAM code implementing the method of boundary integral equations) are used in this simulation. The experimental data agree closely with the simulation results. The electron-beam envelope is reconstructed based on the experimental luminophore data using the K–V envelope code with a genetic algorithm.

Peculiarities of the Azimuthal Transport of High-Current Electron Beams in a Curvilinear Cavity with a Transverse Magnetic Field

Peculiarities of the azimuthal transport of high-current electron beams in a curvilinear cavity with a transverse magnetic field have been studied by means of PIC simulations. It is established that the electron beam current exceeding a certain threshold level favors the appearance of electrons with negative azimuthal momentum.

Generation of Low-Energy High-Current Electron Beams in Plasma-Anode Electron Guns

This paper is a review of studies on the generation of low-energy high-current electron beams in electron guns with a plasma anode and an explosive-emission cathode. The problems related to the initiation of explosive electron emission under plasma and the formation and transport of high-current electron beams in plasma-filled systems are discussed consecutively. Considerable attention is given to the nonstationary effects that occur in the space charge layers of plasma. Emphasis is also placed on the problem of providing a uniform energy density distribution over the beam cross section, which is of critical importance in using electron beams of this type for surface treatment of materials. Examples of facilities based on low-energy high-current electron beam sources are presented and their applications in materials science and practice are discussed.

Two-Dimensional Hybrid Model for High-Current Electron Beam Transport in a Dense Plasma

A two-dimensional hybrid code is developed to model the transport of a high-current electron beam in a dense plasma target. The beam electrons are treated as particles and described by particle-in-cell simulation including collisions with the target plasma particles. The background target plasma is assumed to be a stationary fluid with temperature variations. The return current and the self-generated electric and magnetic fields are obtained by combining Ampère's law without the displacement current, the resistive Ohm's law and Faraday's law. The equations are solved in two-dimensional cylindrical geometry with rotational symmetry on a regular grid, with centered spatial differencing and first-order implicit time differencing. The algorithms implemented in the code are described, and a numerical experiment is performed for an electron beam with Maxwellian distribution ejected into a uniform deuterium-tritium plasma target.

Transportation of high-current electron beams in plasma and plasma-filled diodes

The results of a numerical simulation of the nonstationary processes in different charge-neutralization schemes of high-current electron beams and the results of a measurement of the beam parameters are presented. Most attention is paid to beams with a current higher than the limiting Alfven current.

Measurements of high-current electron beams from X pinches and wire array Z pinches

Some issues concerning high-current electron beam transport from the X pinch cross point to the diagnostic system and measurements of the beam current by Faraday cups are discussed. Results of computer simulation of electron beam propagation from the pinch to the Faraday cup give limits for the measured current for beams having different energy spreads. The beam is partially neutralized as it propagates from the X pinch to a diagnostic system, but within a Faraday cup diagnostic, space charge effects can be very important. Experimental results show evidence of such effects.

GENERATION OF HIGH-CURRENT LOW-ENERGY ELECTRON BEAMS IN SYSTEMS WITH PLASMA EMITTERS

Generation and transport of high-current electron beams are investigated in gas-filled diodes with plasma emitters based on arc and glow discharges. A space-charge neutralized beam with a current up to 1 kA was produced in a diode with a plasma emitter based on an arc discharge for an accelerating voltage of 15 kV. The beam is constricted from 8 cm down to 1 cm in diameter by a self-magnetic field and is transported through a distance of over 20 cm with an efficiency of 70%. A beam with a current of 80 A and a current density up to 100 A/cm2 was produced in a glow-discharge diode. The beam was transported through a distance of 30 cm in a weak axial magnetic field with induction B = 0.015 T.

Pumping of the GARPUN wide-aperture excimer laser by counterpropagating electron beams

The transport of high-current electron beams from vacuum diodes to the laser chamber of the GARPUN wide-aperture excimer laser was investigated experimentally and theoretically. The processes involving the transport of fast electrons in argon and krypton in a longitudinal magnetic field were also studied. Pumping by counter-propagating electron beams resulted in the deposition of up to 2.1 kJ of energy into the active medium of the laser, which corresponded to a specific excitation power of ~0.8 MW cm-3 with an inhomogeneity of less than 20% over a 12 cm × 18 cm aperture. The efficiency of the energy deposition by electron beams was ~60% and the overall efficiency of the laser pumping system was ~16%.

7540. Transport of high-current electron beams in a racetrack betatron: S Humphries, Jr, et al,J Appl Phys,68, 1990, 411–421.

7540. Transport of high-current electron beams in a racetrack betatron: S Humphries, Jr, et al,J Appl Phys,68, 1990, 411–421.

Transport of high-current electron beams in a racetrack betatron

This paper reports theoretical and experimental work on the transport of space-charge-dominated relativistic electron beams in a racetrack betatron with cusp focusing. High-efficiency propagation of 550-keV, 280-A beams through a complex optical system consisting of two 180° arcs with 36 focusing cells and a straight section was observed. More than 90% of the injected beam was captured and transported through the 7-m system. The experiments resolved several recent problems of beam injection and trapping in the machine and showed that electron beam transport at the space-charge limit is possible in a curved cusp array despite strong axial variations of focusing forces. We encountered no problems with the transitions between curved and straight focusing sections. The experiments demonstrated good beam containment in a cusp array with mixed focusing cell geometries as long as the axially averaged focusing force was the same for all cells. The ability to use long cells is a critical feasibility issue for other planned injection experiments into a closed racetrack geometry.

Observations of high-current electron beam transport in a curved system with periodic solenoid lenses

Experiments were performed on high-vacuum transport of a relativistic electron beam (130 A, 300 keV) through a 180° section of a curved transport system. The system was constructed for high-current betatron experiments. The electron beam was directed by a sector-type bending field and focused by an array of 18 solenoidal lenses. The lenses could be operated with the same field polarity (modulated toroidal field) or with alternating polarity (cusp array). The reversing field of the cusp array canceled beam drift motions. Consequently, the beam was quite stable and could tolerate vertical field errors of ±100%. In contrast, beam motion in the toroidal field was dominated by drifts. After propagation through the 3.2-m-long transport tube, significant beam loss was observed with only an 8% vertical field error. Measured displacements of the beam centroid at the end of the transport system were well described by theory in both field geometries.