Comparing Proportional Counter vs SSD XRF Detectors

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XRF analyzers are normally provided with one of two types of detector: proportional counters or semiconductor-based detectors. The silicon drift detector, also called SDD, is widely considered to be the most effective of the semiconductor devices.

Many customers are pleased with their analyzer’s performance when it contains a proportional counter. In particular applications, the proportional counter is the best option for the job.

It is worth noting that there is a reason that SDDs are available, and they do provide benefits over the traditional proportional counter technology. Several of these advantages are described below:

Analyze More than One Element in a Single Scan, Speeding up Your Analysis Time

A secondary filter may be required in order to identify particular elements if a proportional counter is being used to analyze a sample with more than one element.

Detection becomes more precise because the filter subdues the X-ray signal from other elements that could impede the results.

If results for other elements are also required, several filters over the duration of the measurement may be necessary in order to attain a full compositional analysis.

Less scans are required and the total measurement time is decreased because an SDD views all elements simultaneously.

Less Frequent Adjustments Required to Maintain Results Accuracy

In basic terms, proportional counters are cylinders of inert gas that ionize when met with X-ray radiation. The features of this gas are changed by atmospheric temperature.

If the instrument is in a location where the atmospheric conditions vary widely throughout the day, the user will need to re-validate or re-standardize the instrument many times in order to verify the accuracy of the results.

The majority of prop counter instruments automatically perform this. As SDDs are not modified by atmospheric conditions, they are highly stable and normally offer results that are more repeatable.

Easier to Gauge Actual Composition of Your Sample if it’s Complex

The spectrum becomes increasingly more complex depending on the elements present in the sample. The SDD provides much higher resolution between elements, specifically if they are close to each other in the spectrum.

Comparing Proportional Counter vs SSD XRF Detectors

This is displayed in the diagram above. The red peaks present the SDD spectrum and the region in green demonstrates the spectrum for the same sample with a proportional counter.

It can be observed from the diagram that it is a lot easier to discern and measure the actual composition of nickel, zinc, and iron in this sample with the SDD.

Lower Detection Levels Mean SDD Instruments Cover More Applications

When a measurement is taken, background levels of radiation are omnipresent. These background levels are normally less significant with an SDD. This makes it more simple for the instrument to determine a proper signal from background radiation.

If an application requires the detection of contaminants or trace elements in the PPM range, this becomes a significant challenge. For a proportional counter, changes in the background can create a non-detect reading when elements are present.

The contemporary electronics within SDDs can handle a very high count-rate (the rate at which the detector obtains and processes secondary X-ray photons from the sample).

This greatly enhances overall performance which leads to higher accuracy, lower detection limits, and efficient measurement times.

Prop Counter vs SDD: Head to Head Challenge

An actual measurement by two different instruments will now be compared; the Lab-X3500 with a proportional counter and the LAB-X5000 with an SDD.

The test is to investigate the presence of six distinct analytes within one sample of limestone: Fe, Ca, K, Si, AI, and Mg. The proportional counter uses 6.6 minutes and a sequence of four conditions in total to measure all six elements.

It only takes 3 minutes for the SDD to analyze the same elements in a sample. In this example, the LAB-X5000 is twice as efficient as the Lab-X3500. When comparing proportional counter analysis time with SDD, the results are in line with the general findings of Hitachi.

When Should You Consider an SDD Instrument?

There are several basic applications when a proportional counter-based analyzer is a positive solution. For those who have a high-volume facility where current XRF measurements are creating a bottleneck in production, an upgrade to an SDD instrument should be carefully considered.

For those who require lower detection limits for tramp or trace element identification, it would be highly beneficial to discover what SSD-based instruments can offer.

An upgrade should also be potentially considered for applications where elements are measured that are near to each other in the periodic table, and require an optimized resolution to place more trust in the results.

Hitachi would recommend viewing the features of the LAB-X5000 for customers who currently utilize the Lab-X3500 or alternative proportional counter instruments.

Along with the enhanced performance offered by the SDD, it has further characteristics that enable it to deliver better results, which can possibly decrease the costs of analysis.

In particular applications, it can analyze light elements with no requirement for a helium purge. It also provides an instant data export using Wi-Fi to the ExTOPE Connect cloud for dynamic data management.

This information has been sourced, reviewed and adapted from materials provided by Hitachi High-Tech Analytical Science.

For more information on this source, please visit Hitachi High-Tech Analytical Science.

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