Ion Beam Analysis

• Principle
• Ion Beam Analysis Methods
• Experimental Set-up
• Links to others IBA servers

Principle

Ion Beam Analysis (IBA) is based on the interaction, at both the atomic and the nuclear level, between accelerated charged particles and the bombarded material. When a charged particle moving at high speed strikes a material, it interacts with the electrons and nuclei of the material atoms, slows down and possibly deviates from its initial trajectory. This can lead to the emission of particles or radiation whose energy is characteristic of the elements which constitute the sample material.

The spectrometric analysis of this secondary emission may lead to:

• the detection of specific elements in diverse samples as well as the determination of the concentration of these elements.
• the determination of the nature, thickness, position or concentration gradient of several layers of elements or compounds.

The IPNE has access to 3 accelerators from which particles of sufficient energy may be obtained:

• two Van de Graaff type electrostatic accelerators of 2 and 3 MV.
• a variable energy cyclotron whose beam line is equipped with a magnetic analyser.

The nature of the secondary emission detected determines the type of analysis which would produce the optimal results. The various methods are to a certain degree complementary.

The methods discussed present a certain number of common characteristics:

• they are generally not destructive and are thus suitable for use with delicate materials.
• they are to a certain extent multielementary.
• they require little or no preparation of the sample with the result that a specimen (like a arttifact or an atmospheric filter) could be directly analyzed.
• only very small quantities (mg) of sample are needed.
• they permit the analysis of a very small portion of the sample by reducing the diameter of the ion beam to less than 0.5 mm.

The sensitivity and reproducibility of these techniques are dependent on the nature of the target, its texture, its dielectric constant, and its thermic resistance in vacuum. It would therefore be futile to give specific numbers. Each type of analysis must be considered as a special case and treated as such.

These accelerated particle beams allow the setting of the four methods based on the specific processes that are described below.

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Ion Beam Analysis Methods

• PIXEA (Particle Induced X-ray Emission Analysis) is based on atomic fluorescence (Y(a,a'X)Y) and the analysis is performed with characteristic X-rays. PIXEA is well adapted to the dosage of medium to heavy elements in light biomedical matrices (bone, matrice, gel,...).
• PIGEA (Particle Induced Gamma-ray Emission Analysis) is based on nuclear reaction (Y(a,bgamma)Z) and the analysis is performed with characteristic Gamma-ray. PIGEA is particularly useful for dosing light elements such as F or Na which are inaccessible by PIXEA.
• NRA (Nuclear Reaction Analysis) is based on nuclear reaction (Y(a,b)Z) and the analysis is performed with charged particles. NRA has demonstrated its usefulness in the study of the oxydation and deposition of hydrocarbon residue on metallic surfaces.
• RBSA (Rutherford BackScattering Analysis) is based on nuclear scattering (Y(a,a)Y) and the analysis is performed by charged particles. RBSA has proved its efficacity in identifying and localizing thin layers.

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Experimental Set-up

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