Forensics

Perspectives from an exhibition

Dr. Mehdi Bolorizadeh

As the new product manager for the EDS products at EDAX, I had my first opportunity this year to attend Semicon Korea, which was held in Seoul last week. This show is the region’s largest manufacturing event with over 550 exhibitors, displaying new products and technologies for microelectronics design and manufacturing.  It featured technologies from across the microelectronics supply chain.  I was there to support the presence of the new EDAX Element Silicon Drift Detector (SDD) on the Ametek booth  and I was also looking forward to learning about all the other new products and technologies exhibited at the show. It was an amazing experience visiting different booths and talking to many different vendors each day.  Even though I thought I had planned my time carefully, I still wasn’t able to gather all the information I wanted.

As members of the materials characterization, microanalysis and research world, we all share similar challenges and experiences. We set out to analyze different materials and provide accurate results to help with the improvement of existing products and the research and development of new solutions in a wide variety of different markets. Looking at the analysis tools and techniques at the show, I was overwhelmed by the sheer volume of products available!

When we approach an analysis task, we may know, for example, that a sample contains Tungsten, but we don’t know where it is or how much of it there is. There are numerous different analytical techniques with different throughputs and resolutions, which can help us to pinpoint the location and quantity of an element in the sample. It is crucial to know which techniques and tools to use and how to balance the resolution and throughput of the signal to get the best possible results.


The new Element SDD was designed to play a key role for industrial customers who are facing critical materials analysis tasks on a daily basis, providing fast and accurate solutions in minimal time.  Its capabilities are optimized for the right balance between throughput and resolution used in industrial applications. Launching Element at SemiCon Korea was a great experience as it enabled me to share EDAX technology with materials characterization experts from many fields and companies, and learn more about actual analysis challenges, which will give us the insight to ensure that EDAX is helping to solve real problems to enable the next generation of technology.

Statistics Do Matter!

Sia Afshari, Program  Manager XRF, EDAX

As I am new at EDAX, my colleague Laurie Krupa sent me a copy of the August 2013 EDS Technical Note on “Mapping Termination Criterion” by Patrick Camus after our conversation about forensic applications.

As I read the technical note, one of those “Déjà Vu AOA” moments took me back to another application a long time ago.

In my previous job, I was involved with the development of a portable XRF device for a determination of lead in paint application.  The EPA/HUD Guidelines were cited and prescribed faithfully as the Operating Protocols (OP) due to the litigious nature of this application and any deviation from these protocols were forbidden!

The HUD Guidelines, at that time, were mandating an average of three 30-second measurements at each location without any reference to the expected error and the degree of confidence that were required for quantification of a measured value.  Digging in the archives for the origin of this OP, it became clear that these outdated protocols were drafted from the User’s Manual recommendations of the original portable XRF system that was manufactured based on 1970’s technology.

Mandating a fixed-time-based measurement by the EPA/HUD without inclusion of the measurement’s statistical error and the degree of confidence led to the collection of meaningless data that were eventually challenged and repeated at a significant cost.  Based on those protocols, there was no distinction in the two measurements below as long as they were performed in 30 seconds:

1.0 ± 0.1 mg/cm2       and     1.0 ± 1.0 mg/cm2

Additionally, the fixed time protocols prevented the effective utilization of modern XRF systems that could perform the intended measurements in a much shorter time and with a higher degree of accuracy based on a set of published performance characteristics that defined the expected error and statistical confidence for each measurement as a function of time and substrate.

It took determined pressing of the issue for a couple of years and a change in the administration to replace the status quo with scientific reasoning to publish a set of Performance Characteristic Sheets as a part of what are the EPA/HUD Chapter 7 Guidelines.  New protocols were based on statistical modeling of the data that were obtained from analyses of real-life samples and under normal operating conditions.

Back from the trip down memory lane, in my view, a similar situation seems to be present in the spectral imaging data acquisition for forensic application.  The existing OP requires a fixed termination time without reference to the statistical significance of the count rate per pixel that defines the quality of the image.  The input x-ray count rate to generate an image is a unique characteristic of the instrument used and can vary drastically from one system to the next.

In the referenced technical note, Pat Camus skillfully presents and concludes that “Spectral imaging data sets should be acquired with a termination criterion that provides a statistical level suitable for correct interpretation of the data”.  The enclosed images in his technical note clearly support his position and the necessity for including the statistical expectation as a part of the measurement criteria!

The existing spectral imaging protocols are probably drawn from an older generation of XRF operation procedures where extended measurement time for acquisition of an image was necessary due to the low count rates.  The modern XRF systems with high intensity micro-focus x-ray tubes, polycapillary x-ray optics, Silicon Drift Detectors (SDD), and advanced software algorithms can generate and process much higher count rates than their earlier generation, resulting in consistent, repeatable, and higher quality images for forensic application in a much shorter time.

As with the EPA/HUD experience, a new scientific approach should be considered in imaging protocols that is based on spectral count per pixel rather than a fixed measurement time.  Implementing a statistical approach in data acquisition will utilize the technological advances in instrumentation, increase the optimization of analyst and instrumentation time, and provide more consistent results in forensic application for direct comparison of data sets.

After all, statistics do matter!