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Design Study of a 200 KeV Scanning Proton Microprobe Using a Field Ionization Source

A preliminary design study has been conducted for constructing a 200 KeV scanning proton microprobe which utilizes the phenomenon of field ionization in hydrogen gas to create a proton source of extremely small dimensions and high "brightness." Calculations for the focusing action of a non-uniformly graded accelerating column, in conjunction with a superconducting magnetic solenoid indicate a final beam-spot size better than 50 Å. The ultimate aim is to construct a high energy proton or heavy-ion microprobe which will rival or even excel the field emission scanning electron microscopes presently in use. Justification for using high energy protons (or heavy-ions) as probe particles instead of electrons has been presented in this paper, along with details of the beam transport and focusing system.