Abstract
Intense ion beam production is of high importance for various versatile applications from accelerator injectors to secondary ion mass spectrometry (SIMS). For these purposes, different types of ion beams are needed and, accordingly, the optimum plasma to produce the desired ion beams. RF-type plasma features a simple structure, high plasma density and low plasma temperature, which is essential for negative ion beam production. A very compact RF-type ion source using a planar coil antenna has been developed at IMP for negative molecular oxygen ion beam production. In terms of high-intensity positive ion beam production, 2.45 GHz microwave power-excited plasma has been widely used. At IMP, we developed a 2.45 GHz plasma source with both ridged waveguide and coaxial antenna coupling schemes, tested successfully with intense beam production. Thanks to the plasma built with an external planar coil antenna, high O2− production efficiency has been achieved, i.e., up to 43%. With 2.45 GHz microwave plasma, the ridged waveguide can support a higher power coupling of high efficiency that leads to the production of intense hydrogen beams up to 90 emA, whereas the coaxial antenna is less efficient in power coupling to plasma but can lead to attractive ion source compactness, with a reasonable beam extraction of several emA.
Highlights
A new 13.56 MHz radio frequency (RF)-driven planar antenna ion source was tested at IMP
A more than 40 μA negative oxygen ion beam was detected at the beam line terminal when the than 40 μA negative oxygen ion beam was detected at the beam line terminal when the plasma electrode (PE) aperture was 2 mm, RF power was about 300 W and the ion energy was 10 keV
O− and O2− production is of high importance for secondary ion mass spectrometry (SIMS) application, whereas the existing technologies, including the duoplasmatron source and the filament-driven arc discharge ion source, are not a promising solution with regard to ion beam intensity, lifespan and brightness
Summary
Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affiliations. The spot size is primarily limited by chromatic aberrations introduced as a result of the 5–15 eV energy spread of the ions This results in a lower beam brightness and lower spatial resolution, and the typical brightness values for oxygen beams from a duoplasmatron source are of the order of 100 A m−2 sr−1 V−1. In order to produce a high-brightness, high spatial resolution primary ion beam for SIMS, the RF-driven ion source study was started at IMP in 2018 For those accelerators and ion beam application devices that require high-current mono-charge state ion beams, the 2.45 GHz microwave ion source has a wide range of applications, due to its advantages of a long lifespan, a high beam current and good beam quality. In order to produce an intense ion beam, a three-section ridged waveguide coupler is applied to the ion sources using high 2.45 GHz microwave power heating, while the coaxial antenna microwave coupling structure is used for those ion sources that are of a very compact size
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