Spettro X

"Development of an innovative ED-XRF spectrometer, both from a hardware and software point of view, for the analysis of metal alloys and the determination of the thickness of galvanic coatings"

The aim of the SpettroX project is to that of developing a spectrometer with innovative characteristics which allows to improve the precision of the measurements performed with the X-ray fluorescence technique and consequently broaden the possibilities; of employment.

In particular, the project aims to implement innovative calculation solutions in order to:

1. perform analyzes as accurate and reliable as those of the instruments currently on the market, but using solid-state detectors which allow the analysis process to be largely released from the use of certified standard samples;
2. correctly treat the presence of light elements in the analyzed samples even without carrying out measurements in a helium atmosphere, in such a way that the precision of the thickness measurement is not altered (in the case of coatings on plastic or aluminium) and it is possible to give an estimate of their percentage (in the case of bulk samples);
3. in any case, develop analysis calibration algorithms that allow, if certified samples are available, to increase the precision of the analysis using a modified version of the method of the fundamental parameters, which takes into account the results obtained on standard samples.

Stato dell’arte

X-ray fluorescence is a non-destructive technique that allows to determine the chemical composition of a sample through the analysis of the fluorescence spectrum emitted by the sample itself when it is irradiated with sufficiently energetic X-rays.
For when an atom is irradiated with electromagnetic radiation, typically of energy of the order of KeV, it is capable of absorbing an incident photon and ejecting an electron from the closest shells; internal (photoelectron). The rearrangement of the remaining electrons between the various levels of the atom involves the emission of a photon X whose energy, lower than the energy of the exciter radiation, is characteristic of the emitting atom.

Quantitative determinations are generally carried out using the so-called method of fundamental parameters, which consists in using the equations governing the physical phenomenon of fluorescence to reproduce the intensity of the fluorescence. of the peaks relating to the various elements.

The most popular application diffuse X-ray fluorescence is the industrial one, for example in companies that deal with metal recovery, in engineering companies and in those that deal with surface treatment of metals. Being a non-destructive method, in recent years it is also finding profitable use in the cultural heritage sector.

In the ED-XRF instruments, to which this project refers, the X-rays are collected by a detector, which can be scanned. be gas (proportional counter) or solid state (Si pin or Silicon drift Detector, SDD), which transforms photons into electrical impulses, which are then sent to a multi-channel analyzer capable of discriminating them based on their energy (Fig.2 ).

In both cases, a spectrum is obtained in which each peak corresponds to a characteristic energy of the emitter atom. From the identification of the peaks, the presence of certain elements in the sample is deduced.

Obiettivi del progetto

The present project aims to achieve a significant innovation in the field of X-ray fluorescence spectrometry, with the aim of making the technique increasingly more advanced. reliable through the introduction of advanced technological solutions, while maintaining a competitive cost for the end user.

Quantitatively, these are the results they want to achieve:

1. Realization of an X-ray fluorescence spectrometer that uses a solid-state detector (preferably a SDD detector, Silicon Drift Detector) for the acquisition of fluorescence signals. In fact, solid-state detectors guarantee excellent energy resolution, even lower than 150 eV in the case of SDDs, and are becoming increasingly popular. competitive in terms of price; as a result, it is today it is conceivable to be able to equip instruments intended for widely used applications with this type of detector, as the quality/price ratio is becoming more and more competitive. favorable compared to that of proportional meters, which are cheap but with poor energy resolution. These are the general characteristics of the prototype to be created:
   
   
   1. X-ray tube:
      1. High voltage: at least 40 kV;
      2. Power: up to a maximum of 50 W;
      3. 1.0-1.2 mm diameter collimator.
   
   
   2. Detector: Yes PIN or SDD, in any case with resolution lower than 200 eV at the energy of the Kα line of Fe (6.40 KeV);


2. Implementation of innovative analytical methods for determining the concentration of light elements in samples. Light elements emit characteristic photons of energy so that are absorbed by the air before they can reach the detector, and is not possible, therefore, to reveal them directly. In the context of the present project, however, we want to exploit the coherent and incoherent scattering phenomena, which are particularly significant for elements with a low atomic number Z, to determine the overall concentration of the light elements present in the sample. This is it is particularly useful when aluminum or magnesium alloys have to be analysed, but also when considering alloys of more complex metals. heavy that have however; significant concentrations of silicon and/or aluminum (for example titanium alloys, silicon and aluminum bronzes, some steels and some types of nickel alloys).
   From a quantitative point of view, the goal is that of determining the overall concentration of the light elements with an error not exceeding 2%.


3. Develop analysis calibration algorithms that allow, if certified samples are available, to increase the precision of the analysis using one or more methods. modified versions of the method of the fundamental parameters, which take into account the results obtained on standard samples.
   From this point of view, there are several ways to experiment:
   
   1. Use of a limited number of samples of the same type of alloy to improve the analysis of a particular type of material: for example, if you have a series of certified steel samples, you can; think about optimizing the measurement parameters (in particular the emission spectrum of the X-ray tube and the efficiency spectrum of the detector) to improve the analysis on steels;
   
   
   2. Use of a large number of samples of different types to optimize the performance of the instrument globally, on all types of materials;
   
   
   3. Use of an intermediate strategy, i.e. based first on the approximate determination of the material composition through the use of the calibration referred to in point ii), and then on the refinement of the method through the use of the calibration referred to in point i), if there are sufficient measurements on standard samples. This procedure should be performed automatically by the analysis software, in order to obtain an extremely precise and reliable analysis on a wide range of materials.