A time-of-flight (TOP) atom- probe field-ion microscope (FIM) designed for the study of defects is described. This atom probe features: 1. (1) a variable magnification internal-image-intensification system; 2. (2) a liquid-helium goniometer stage; 3. (3) a low-energy (≤3 keV) gas-ion gun for in-situ irradiations; 4. (4) an ultra-high vacuum (≈3 × 10-10 torr) chamber; 5. (5) a high vacuum (≈10-6 Torr) specimen-exchange device; 6. (6) a Chevron ion detector; an 7. (7) an eight-channel digital timer with a ±10 ns resolution for measuring the TOFs. The entire process of applying the evaporation pulse to the specimen, measuring the voltages, and analyzing the TOF data is controlled by a computer. With this system we can record and analyze 600 TOF/min. Results on unirradiated specimens of molybdenum, tungsten, W-25 at% Re, Mo-1.0 at% Ti, Mo-1.0 at% Ti-0.08 at% Zr and a special low swelling stainless steel alloy (LS1A) demonstrate the instrument's ability to determine quantitatively concentrations at the 5 × 10-4 at fr level and to determine their spatial distribution with a resolution of a few angstroms.
ASJC Scopus subject areas
- Nuclear and High Energy Physics
- Materials Science(all)
- Nuclear Energy and Engineering