Emittance of a Low-Power RF Ion Source with a Micrometer-Scale Extraction Aperture
Abstract
The concept of a compact nuclear microprobe is based on specialized ion sources with beam currents not exceeding a few nanoamperes and a small energy spread. At the Institute of Applied Physics, NAS of Ukraine, a low-power RF ion source has been developed for application in a compact nuclear microprobe. The source operates at low RF power (< 10 W) and is designed to generate a 1H⁺ ion beam required for standard techniques such as PIXE, RBS, and proton beam writing. To reduce the beam emittance and improve the spatial resolution of the microprobe, the source extraction aperture diameter was reduced to 50 μm. This paper reports measurements of the total beam current and emittance extracted from the low-power RF ion source with a micrometer-scale extraction aperture. Data on the beam profile, its diameter, and divergence angle are also presented. The main parameters of the RF source are as follows: quartz chamber diameter – 34 mm, length – 70 mm, working gas – hydrogen, extraction aperture diameter – 50 μm, RF power ≤ 10 W, frequency – 45 MHz, ion current up to 100 nA. The extraction voltage varies from 10 to 300 V, while the beam energy ranges from 1 to 6.5 keV. Beam emittance was measured using an electrostatic Allison-type scanner. The minimum emittance containing 90% of the total beam current was found to be ε90 = 1.36 π∙mm∙mrad, while the rms-emittance is εrms = 0.32 mm∙mrad. The normalized emittance is εN = 0.003 π∙mm∙mrad, and the energy-normalized emittance equals 0.1 π∙mm∙mrad∙(MeV)1/2. It is shown that reducing the diameter of the extraction aperture of the ion source to 50 μm results in a significant improvement in the ion-optical characteristics of the extracted beam.
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Copyright (c) 2025 Vitalii I. Voznyi, Aleksandr G. Ponomarev, Dmytro V. Mahilin, Dmytro P. Shulha, Volodymyr A. Rebrov
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