Microprobe

Most IBA techniques measure the average concentration over the area of the analysing beam spot. This area is typically between 1 and 50mm². Some samples have features sizes that are smaller then this, and therefore, it is an advantage to have a micro sized beam that is capable of resolving these small surface features.

The High Energy Heavy Ion Microprobe (HINM) is designed to do just that. It is currently capable of focusing ion beams to spot sizes of approximately 2 μm. In contrary to most ion microprobes existing around the world, the ANSTO High Energy Heavy Ion Microprobe can focus ions from hydrogen up to iodine. Thus this analytical facility is not limited to μPIXE and μRBS analysis, but most IBA techniques (eg. IBIC and μERDA) can be used.

Basic Principles

1. In Nuclear Microscopy, a focused beam of high energy ions is used to "illuminate" the sample.
2. Obtained image is not an optical image but rather elemental image as atoms, when irradiated with energetic ions emit x-rays, which are characteristic for each element.
3. By scanning the ion beam over the sample characteristic x-rays are emitted and elemental maps created - see Figure below.

Applications of Heavy Ion Nuclear Microprobe

1. μPIXE - Imaging of elemental distribution on micro-scale (elemental maps of minute samples as for e.g. minerals, biological cells, aerosol particles, etc.),
2. Micro-characterisation (determining elemental concentrations in micro-particles, composition and thicknesses of thin metallic films, etc. )
3. IBIC - Micro-charge deposition (Ion Beam Induced Current -IBIC, single event upset),
4. Micro-irradiation (e.g. single cell irradiation),
5. Micro-damage (testing reliability of electronic devices),
6. Micro-machining (producing miniature devices), etc.

An example of elemental maps taken with the microprobe are shown below:

Quantitative elemental maps showing distribution of Ni, Ca and K in air-dried seed longitudinal sections of Hybanthus floribundus subsp. adpressus (a–c), H. floribundus subsp. floribundus (d–f) and Pimelea leptospermoides (g–i). Concentrations are in dry weight %. The area transect out- lined in green on Ni images relate to profiles. (T=testa; C=cotyledon and E=embryonic axis). The maps clearly show that the Ni is accumulating in the cotyledon of the seeds, which is the part of the seed, that upon germination becomes the first embryonic leaves of the seedling.