Article

The ECR volume effect and its consequences

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Abstract

Summary form only given. During the past decade and a half, remarkable progress has been made in the technology of the ECR ion source, due, in large-part, to an improved understanding of the atomic processes that limit ion production. A number of design improvements and technical developments can be cited that individually or in combination have significantly improved the high-charge-state capabilities of these sources. For example, for a given design, the intensities of the high-charge-state beams extracted from these sources have increased by improvement in plasma confinement; by operating at high frequencies, as predicted by theory; by improvement in vacuum quality; by supplementing their plasma-discharges with cold electrons; by discovery of the gas mixing effect; and by increasing the number or physical size of their ECR zones. This article is devoted to the volume ECR effect and its consequences. Since the probability for adsorption of RF power depends on sizes of embedded ECR zones, sources with larger ECR zones have the ability to adsorb more ECR power and consequently, to accelerate larger populations of electrons to higher energies and consequently, to produce higher charge-states. Enlarged ECR zones have been achieved by engineering the central magnetic field region of these sources so they are flat and in resonance with single-frequency RF power. Alternatively, in conventional minimum-5 geometry sources, the number of ECR surfaces can be increased by heating their plasmas with multiple, discrete frequency microwave radiation. Broadband RF power offers a simpler, lower cost and more effective means for increasing the physical sizes of the ECR zones within the latter type of source. Recently, broadband RF power has been utilized to enhance the high-charge-state performances of conventional-B geometry ECR ion sources. This presentation provides the elementary theory of why enlarged ECR zones are desirable and provides experimental evidence that sources with- - enlarged ECR zones convincingly outperform their single-frequency, conventional-B geometry counterparts

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... Electron cyclotron resonance (ECR) ion source is an essential component of heavy-ion accelerator. For a given design, the intensities of the highly charged ion beams extracted from the source can be increased by enlarging the physical volume of ECR zone [1]. Several models for ECR ion source were and will be constructed depending on their operating conditions [2][3][4]. ...
Article
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Electron cyclotron resonance (ECR) ion source is an essential component of heavy-ion accelerator. For a given design, the intensities of the highly charged ion beams extracted from the source can be increased by enlarging the physical volume of ECR zone [1]. Several models for ECR ion source were and will be constructed depending on their operating conditions [2-4]. In this paper three simulation models with 3, 4 and 6 solenoid system were built, but it’s not considered anything else except the number of coils. Two groups of optimization analysis are presented, and the evolution strategy (ES) is adopted as an optimization tool which is a technique based on the ideas of mutation, adaptation and annealing [5]. In this research, the volume of ECR zone was calculated approximately, and optimized designs for ECR solenoid magnet system were presented. Firstly it is better to make the volume of ECR zone large to increase the intensity of ion beam under the specific confinement field conditions. At the same time the total volume of superconducting solenoids must be decreased to save material. By considering the volume of ECR zone and the total length of solenoids in each model with different number of coils, the 6 solenoid system represented the highest coil performance. By the way, a certain case, ECR zone volume itself can be essential than the cost. So the maximum ECR zone volume for each solenoid magnet system was calculated respectively with the same size of the plasma chamber and the total magnet space. By comparing the volume of ECR zone, the 6 solenoid system can be also made with the maximum ECR zone volume. © 2015, Korea Institute of Applied Superconductivity and Cryogenics. All rights reserved.
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