Fig. 3-1 Evaluation of beam size The microbeam is scanned on a silicon relief pattern (left hand). The beam size is evaluated from the sharpness of a peak (below) in the secondary electron yield emitted from the edge of the pattern.

Fig. 3-2 Drawing with microbeam The letters of "TIARA" (name of the ion beam irradiation research facility at Takasaki Establishment) and a Chinese character "TAKUMI" (fine art) were drawn on a plastic plate (CR-39) with the microbeam which was shifted step by step using steering electric fields. The hole size was expanded by chemical etching for visualization.

JAERI succeeded in producing a 2 MeV helium ion beam of 0.4 micrometer x 0.4 micrometer in size and 77 pA (picoampere = 10-12 A) in intensity. By further R&D a 2 MeV helium beam (0.19 micrometer x 0.26 micrometer, 15 pA) and a 2 MeV proton beam (0.18 micrometer x 0.22 micrometer, 1 pA) were obtained. This was the first in the world as a micro ion beam of pA and 0.2 micrometer level, although there exist MeV beams of fA (femtoampere = 10-15 A) and 0.1 micrometer level. For an application of the intense and fine beams, JAERI is starting the development of a micro PIXE (particle induced x-ray emission) camera which can analyze distributions of metallic elements like zinc in biological cells. It has recently been recognized that these elements correlate with health conditions. The beams will also be applied for studies on local deactivation of bio cells, in which the size of the chromosome corresponds to 0.2 micrometer, and on malfunction of local parts in semiconductor devices induced by cosmic rays.

Reference T. Kamiya et al., Submicron Microbeam Apparatus using a Single-ended Accelerator with Very High Voltage Stability, Nucl. Instrum. Methods Phys. Res., Sect. B 104, 43 (1995).

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