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XRF - Energy dispersive X-ray fluorescence analysis

XRF X-ray Fluorescence Analysis Instrument

Your Demand is our Incentive โ€“ Benefits of Fischer XRF Measurement Technology at a Glance

We have what you need: many years of comprehensive expertise in the field of X-ray fluorescence analysis (XRF analysis)! You get the optimal solution, especially for your measurement task โ€“ we promise!

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XRF Measuring Principle by Fischer โ€“ This is how it Works:

Fast, simple, and non-destructive โ€“ thatยดs what XRF analysis with Fischer XRF measurement technology stands for! The X-ray beam ionizes the atoms in the measurement sample. The detector detects the occurring fluorescence radiation, and the in-house developed software processes the signals.

Setup of Fischer XRF Measuring Instruments โ€“ This is how Optimum Measuring Results are Achieved:

Attention must be paid to the details: every single component has a stake in your measuring success!

X-ray Tube and Anode Material:
Small parts, a significant effect! The "heart" of the XRF device, the X-ray generator, consists of a standard or microfocus tube with tungsten, rhodium, molybdenum or chromium anode. These components are decisive which measurement precision and which energy spectrum are achieved.

Filter:
Only what is essential gets through: the X-ray beam passes through a filter to reduce background noise in relevant energy ranges and thus achieve higher sensitivity for signals from materials that are present in only low concentrations.

Apertures and X-ray Optics:
Focus made by Fischer! As one of only 2 manufacturers of polycapillary optics worldwide, we enable a large part of the primary radiation to be focused on a tiny measurement spot.

Detectors:
Unique on the market! Only at Fischer, you have the choice of 3 different detector types for the optimal solution of your measurement task: proportional counter tube, silicon PIN diode and silicon drift detector.

The basics of XRF X-ray fluorescence analysis and the most important XRF instrument properties

In the past, X-ray fluorescence analysis (XRF) was mainly used in geology. Today XRF analysis is firmly established as a key technology for use in both industry and in the laboratory for measuring coating thickness. This method is extraordinarily versatile: it can detect all relevant chemical elements from sodium to uranium.

XRF is often used for material analysis, i.e. to determine the amount of a given substance in the sample, like measuring the gold content in jewelry or detecting hazardous substances in everyday objects in line with the Restriction of Hazardous Substances (RoHS) directive. In addition, the thickness of coatings can be measured with XRF: itโ€™s fast, clean and non-destructive.

This is how the XRF measurement works

As an X-RAY XRF device starts a measurement, the X-ray tube emits high-energy radiation, which is also called the โ€˜primaryโ€™ radiation. When these X-rays hit an atom in the sample, they add energy โ€“ i. e. they โ€˜exciteโ€™ it โ€“ causing the atom to eject an electron close to its nucleus, a process known as โ€˜ionizationโ€™. Since this state is unstable, an electron from a higher shell moves in to fill the gap, thereby emitting โ€˜fluorescenceโ€™ radiation.

The energy level of this secondary radiation is like a fingerprint: itโ€™s characteristic for the respective element. A detector sees the fluorescence and digitizes the signal. After the signal has been processed, the device creates a spectrum: The energy level of the detected photons is plotted on the x-axis and their frequency on the y-axis (count rate). The elements in the sample can be identified from the positions (along the x-axis) of the peaks in the spectrum. The levels (along the y-axis) of these peaks provide information about the elementsโ€™ concentration.

THE MOST IMPORTANT DEVICE PROPERTIES FOR THE BEST XRF ANALYSIS RESULT

Many factors influence how well the XRF analyzer  can differentiate between elements. Components such as the X-ray tube, optics, filters and the detector play a major role in this.

X-ray tube

The materials in the X-ray tube determine the energy spectrum of the primary X-ray radiation with which the sample is excited. A tungsten anode is commonly used because it produces a particularly intensive and broad spectrum that can be employed for general applications. For specialized applications, e.g. in the semiconductor or printed circuit board (PCB) industries, molybdenum, chromium or rhodium anodes are also used; these anodes are particularly suitable for measuring light elements and material analysis.

Filters

On the way from the anode to the sample, the primary X-rays pass through a filter. Fischer generally uses filters made from thin metal foils, e. g. from aluminum or nickel. These filters modify the characteristics of the primary radiation by absorbing part of the spectrum. This way the background noise can be significantly reduced. Thus, a higher sensitivity to weak signals can be achieved. For example, aluminum filters help to detect lead in particularly low concentrations

Apertures and X-ray optics

The aperture (collimator) lies between the X-ray tube and the sample. It controls the size of the primary beam and ensures that only a specific, focused spot on the sample is excited.

When the measurement spot is necessarily small, the radiation that reaches the sample is minimal and the resulting fluorescence signal is correspondingly weak. To achieve high enough counts for reliable evaluation, the measurements need to take longer.

The solution to this problem is polycapillary optics. Polycapillaries are bundles of glass fibers that focus the almost entire primary radiation like a magnifying glass on a small spot. There are only two manufacturers of such optics worldwide โ€“ and Fischer is one of them! 

Detector for Quantitative Determination of the Elements

The last crucial component for the method of XRF analysis is the detector, which detects the fluorescence radiation and measures it with the highest accuracy. The information from the detector is passed to the analysis software and processed accordingly. The detector type determines which measurement tasks you can solve with the XRF spectrometer.
We offer the most comprehensive detector portfolio on the market. This means that only at Fischer will you find the detector tailored to your measurement task and solve it optimally. There are 3 types of detectors that offer specific advantages.

The well-tried proportional counter (PC) tube is indispensable in the portfolio of a measurement technology specialist. It offers a vast active detector area with a slightly curved window. This feature allows achieving high count rates as a large amount of fluorescence radiation reaches the detector. It makes measurements at 20 โ€“ 80 mm away from a sample possible. The PC tube is predestined for coating thickness measurements in the range of 1 โ€“ 30 ยตm and small measuring spots. Another advantage is that the PC tube is significantly less sensitive regarding the accuracy of the sample alignment to the detector and the measuring distance setting. The PC tube features the drift compensation developed by Fischer as standard, which gives exceptional stability.

For more demanding coating thickness measurements, a higher energy resolution is required. In this case, the application of XRF analyzers with silicon PIN diode is a good choice. This semiconductor detector can also be successfully used for simple material analysis. Thus, the silicon PIN detector is the perfect middle link in our detector portfolio.

High-quality XRF spectrometers use the silicon drift detector (SDD). This detector is the most powerful. It has a particularly good energy resolution and an especially high detection sensitivity. Thus, when investigating the elemental composition of materials, the SDD offers the best performance of all detectors. The fluorescence radiation of elements in the sample that are present in only very low concentrations is easily detected. In addition, instruments equipped with an SDD precisely determine the thickness of coatings in the nanometer range and allow the reliable evaluation of complex multilayer tasks.

The Proportional Counter Tube still has its Right to Exist. Here you can Read Why.

Patented by Fischer: the DCM method for simple and fast adjustment of the measuring distance

  • Distance-dependent measured value correction 
  • Fast and convenient adjustment of different measuring distances
  • The measuring distance can be adjusted smoothly - for measurements with the smallest possible distance and thus optimized counting rate    
  • Simple measurement of complex geometric shapes and in recesses 
  • Only with Fischer DCM: no risk of collision for the measuring head

The Distance Controlled Measurement (DCM) method patented by Fischer allows for maximum flexibility in your measurements. Thanks to DCM, the correct measuring distance for your sample can be set via the video focus and taken into account during evaluation. This ensures simple and fast measurement without prior calibration. Complicated geometry shapes and recesses are no longer a problem.

The Right Measuring Device for your Dedicated Measuring Task

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