Development of high demagnification lens system by forming a virtual object

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Enhancement of the demagnification at an acceleration lens system was studied to generate several tens keV gaseous ion nanobeam using the nano-beam formation apparatus in JAEA. The concept of the enhancement of the demagnification was as follows ; (1) Several hundred eV gaseous ion beam (low energy gaseous beam) with a small imaginary object was generated by a dedicated plasma-type ion source. (2) Its low energy gaseous ion beam was injected into the two-stage acceleration lens system. A direct beam extraction electrode system was installed in the ion source to generate ion beams with the small divergence angle. A minimum hydrogen beam size of 120 nm in diameter with 36 pA at 47 keV was successfully formed by the experiment as the beam trajectory simulation. The focusing lens system with the demagnification over 1700 was composed of combining the plasma-type ion source with the direct extraction electrode and the two-stage acceleration lens system.