EDS Detectors

It’s All About Speed!

Dr. Oleg Lourie, Senior Product Manager EDS, EDAX

Different perceptions of speed can be measured differently, and yet in my opinion speed is one of those few fascinating concepts, which you are always aware of regardless of your activity. The world of speed is enriched with various emotional flavors which generate a multitude of reactions:  curiosity, when I observed the 690m/h cruising speed during my recent flight with KLM (‘are we getting close to 1Mach and when?’), or a contemplative focus when you accelerate to 170m/h on the German Autobahn near Düsseldorf.

In all circumstances speed inevitably arrests your attention, just as blazing fast EDS mapping did for me recently, when I saw a literally staggering acquisition speed below 200 us/pixel, which translated into a 512×400 pixel, fully quantifiable elemental map, which was collected in less than 1 min.

The ‘Octane’ EDS power, that ‘fueled’ this racing performance is equally remarkable – holding above 2Mcps in X-ray input counts without a single complaint  and exploding with 860Kcps for a single channel at about 50% dead time. I should admit I simply enjoyed it. It is inspiring to push the ‘limits’. The new electronics for this system will move things even further by leveling the throughput up to 1.8Mcps for a single channel – literally doubling the processing speed of the system.

1. Phase map of mineral clearly showing separation of zirconium silicate and calcium phosphate phases. 2. Spectrum of zirconium silicate

While astounded at the extreme throughput, a casual observer may wonder where this power can be applied in a ‘daily commute’ for elemental information. The answer is everywhere! It affects all your materials analysis when there are no boundaries imposed by your spectrometer on the scope of your experiment. It is indispensable for setting automated runs where sudden changes in sample composition, geometry or topography can impact acquisition. It aids in the formulation of statistics, where you need the fastest screening to acquire reliable statistical data. It is essential in ‘in situ’ studies where you rapidly change the sample compositional structure during the observation. It is useful in observing live Direct Phase Mapping and showing various phase distributions immediately after the scanned image is acquired. With more than 860 kcps ‘under the hood’, low noise CUBE electronics design and pulse processing times geared from 7.8 us to 120 ns, you can focus on driving your experiment at any speed you can imagine to achieve superior results in less time.

3. Spectrum of calcium phosphate 4. Superimposed spectra of 2 and 3 showing an complete overlap of the P and Zr peaks, which makes them undistinguishable in the RGB elemental map.

With all this ‘Octane’ power to keep your acquisition limits tunable on demand, there are many more exciting experiments further ‘down the road’. And yes, the roads can be icy and slippery in December. It is more fun to race with your fast EDS, collecting powerful, streamlined data and aiming towards the holidays with new observations, and possibly new discoveries.

Why you should never leave home without your plasma cleaner – at least if you are going to M&M

Dr. Jens Rafaelsen – Applications Engineer, EDAX

One of the things I learned during the 2015 Microscopy and Microanalysis meeting was just how efficient plasma cleaners really are and this is a short story about how it saved the day for us. We had shipped our older Hitachi S3400N microscope from Mahwah to Portland for the show and had tested everything before it went on the truck. The meeting opened Monday August 3 at noon so Sunday was set aside for getting everything set up and calibrated. While our service group had done most of the work, I had a bit of data I wanted to collect for the days to follow. So I sat down at the microscope, turned on the beam, and stared at the current meter showing next to nothing. I checked the usual microscope settings and fidgeted with the apertures but still couldn’t get a decent current down through the column. Since we were a little short on time and the Hitachi booth was close by, we went over and looked sufficiently desperate for the Hitachi service guys to take pity on us and come to help.

I noticed the Hitachi guys going through the same steps I had done and end up with the same problem, so at least it wasn’t just down to my short comings regarding microscope service. As the last step they pulled out the aperture strip and the black gunk covering all three apertures gave us a pretty good indication of the problem: the beam was being severely attenuated simply because the apertures were clogged up with carbon contamination. Of course the Hitachi guys’ immediate question was “Did you bring a new aperture strip?” and my answer was a meek “No…”. But then I remembered that I did bring a plasma cleaner. I didn’t really believe that it would be able to do much with the level of contamination that we had on the apertures but it was still worth a shot. So I put the aperture strip in the cleaner chamber and ran it at a pressure of 2*10-2 mbar with a power of 50 W.

I have to say that I was extremely surprised when the aperture strip looked as good as new after only 10 minutes of plasma exposure. Both the EDAX and Hitachi service guys were equally impressed and after mounting the strip back in the column we were up and running again. So 10 minutes of plasma cleaning saved us from having to either try to have an aperture strip shipped in overnight or run the microscope with no aperture and ensuing risk of sample damage and reduced imaging capability. Unfortunately I didn’t take any pictures before and after cleaning, as I honestly was not expecting it to work, but the picture below shows us busy running demos on the Hitachi during the show.

The EDAX booth at M&M 2015

At this point you might wonder why I had brought a plasma cleaner in the first place. Well, one of the things that we were highlighting with the new Octane Elite detector we launched at the show was the silicon nitride window and its durability. I had run a test on my office desk with a live detector mounted directly on an asher chamber (shown in Figure 1) that I borrowed from Vince Carlino of ibss Group, Inc. When the asher chamber is running, it looks like something out of a science fiction movie so we wanted to do something similar at the M&M meeting as a visual prop.

Figure 1: Silicon nitride window detector mounted on ibss asher chamber.

Since a full detector takes up space we simply put a single detector module directly in the asher chamber and started the cleaning process on Monday when the exhibition began. I took pictures of the controller for the system and the module at the start and end of each day as can be seen in the picture sequence below.

Figure 2: The controller and module at the start and end of each day.

After almost 76 hours of continuous plasma exposure, the silicon nitride window shows no signs of degradation and knowing what plasma cleaning did to the aperture strip, I am pretty certain that was absolutely no carbon contamination on the window. Of course this is more of a show-and-tell kind of experiment and the testing I did before this involved detailed monitoring of the module performance and temperature to detect any pin-holes that would not be visible by eye. That report will be available shortly.

The next step will be to try the same with a polymer window but I am still thinking about exactly how to design the experiment. Of course I could just clean it for an extended period of time and see if the window is still intact but it would be nice to have a metric of how fast the damage occurs (or not). One idea would be to use a bare window and correlate the ratio of the carbon and aluminum signal of the window to the silicon peak from the support grid in order to monitor any changes in thickness, but if anyone has other suggestions, I would be happy to hear them.

Even though the tabletop plasma cleaner has been around for a number of years, its complete usefulness is sometimes is overlooked because it is a small piece of  auxillary equipment. Sometimes, however,  the smallest of equipment can provide the largest benefit!

When Shattering Performance Limits Makes You Think You Have Broken Your New Detector!

Tara Nylese, Global Applications Manager

The last few months have been some of the most rewarding ever throughout my time at EDAX.  In the last year or more we’ve been working on a series of new detector technology offerings, which we can now finally bring to our customers.  These detector advancements are quite literally shattering past performance limits.  And it’s not just one technology, but a combination of three technologies together which makes the Octane Elite launch one of the most exciting of my 20 year career here.

Two months ago, I sat at the system generating data that would give us an idea of the performance specifications that we could associate with the product promotion as we went to launch.  I had just achieved a never before reached input count rate of 2 million counts per second, but was slightly hesitant to promote that, since it’s variable based on SEM conditions and sample.  So, I let it sit for a bit and we went into a stellar M&M show with a strong set of performance specs from low energy performance to grid materials and spectral resolutions at high speeds.  Following the show, we had a webinar planned, which again focused on those performance limits. It’s been one of my goals this year to be very data-driven, using direct examples to let a story show itself, so a crucial piece of the webinar was to collect the applied examples that illustrate the specs, and this made a great opportunity to revisit the 2 MCPS data collection.

Being efficient (much like our detectors!) I like to try to use one sample to tell multiple stories, so I grabbed a favorite ductile iron sample, which has both carbon for low energy performance and iron for high speed mapping.  My first notable point was that I could run the count rate up to 750 K CPS input with max output at 60% deadtime and still obtain an excellent carbon peak in a spectrum extracted from a map (Figure 1).  At these high count rates, older technology detectors cannot maintain this type of performance, and we’ve even seen carbon dropping off at 500 K CPS, our previous best, which was also an industry high.  And by dropping off, I really do mean that the spectrum will no longer show a carbon peak as the spectrum no longer displays the peak at all, or in some cases, a highly distorted peak with little differentiation from the background.  So, by achieving a carbon map at one and a half times the highest count rate ever achieved before, I felt I really shattered previous limits.  I didn’t stop there, but pushed the count rate up to 1.5 M CPS input and still was able to detect the carbon peak, albeit with some degradation in the quality of the spectrum.

Figure 1 shows a clear display of the quality low energy performance even extracted extracted from a high speed map collected at 750 KCPS.

But why stop there?  As I was already ramping up the count rate, I figured I’d continue as far as I could, and I opened the aperture all the way on our thermal FEG.  At this point, I was running our SEM at 20 kV and max aperture, which would mean a beam current at or above 100 nA.  This is really not an achievement in itself, since most all thermal FEGs can get there, and this SEM is 15 years old, so it’s not a new type of achievement.  The steel sample was conductive, of course, making it suitable for this condition, but it was mounted in a non-conductive mount, so I had it grounded simply with carbon tape.

Once I opened the aperture, I had to do a double take at the CPS since that was a lot of numbers, and I actually counted to make sure I had it right – we were at 2.8 M CPS input!  The reason I had a hard time believing this is that normally at that count rate, the detector would saturate and this time it did not.  I was certain at that moment that I had broken our new detector and what I was seeing must be noise, because even just getting those counts without the detector turning off is a feat.  So, of course I had to collect data to see what the quality was.  And while the dead time was high at >90%, I was still able to collect a phase map (Figure 2) where both the low energy elements and higher energy steel were solved by the phase map routine in just a few passes.

These detectors have a great many additional performance enhancements with the Silicon Nitride window, vacuum encapsulation and CUBE electronics, but this example serves as a good display of the payoff of all combined, and this work would not be possible without the benefits of all of these aspects together.

To also address the windowless comments that I’ve gotten since my webinar, in summary, that’s an altogether different product.  Our Octane Elite is a mainstream, general purpose detector that has all of these performance benefits, while the windowless serves more of a niche set of applications.  I’ve had a windowless detector in my lab for years now and I’ll be very honest, it sits unused on a bench and I only mount it when I have a special requirement. My detector of choice, given my unlimited detector options, is absolutely the Octane Elite.

Figure 2 shows the highest x-ray map ever collected at EDAX at 2.8 million counts per second at 20 kV with the Octane Elite detector technology. Steel matrix is shown in red and graphite nodules are blue.

On a side note – we’re currently looking to fill an EBSD apps position in our NJ lab, and as I describe the job to potential candidates, I’m always drawn to some of the real highlights that an applications position offers someone in the technology field.  I hope this blog today captures it perfectly.  As an apps person, we bridge the area between commercial and development, or customer and engineering.  In fact, it’s even part of our mission statement that the applications group understands the real world customer needs and translates them into the product development process at EDAX for our future products.  This in turn, strengthens our products and services to meet the most important needs, those of our customers and those that further the technology into groundbreaking directions like this never before achieved detector performance.

Windows of Opportunity?

Dr. Patrick Camus, Director of Research and Innovation, EDAX

You may have heard of a new breed of SDD that has an ultra-thin Silicon-Nitride (Si3N4) window. Its main advantage over traditional polymer windows is its significantly higher low-energy sensitivity. In addition, it is both moisture and plasma-cleaning tolerant which permits the true vacuum sensor environment to persist for the lifetime of the detector.

If you have concerns about the robustness of this new window, watch this video, which shows some informal torture tests being performed. You will come away astounded at the results.

Click here for more information on EDAX detectors using a silicon nitride window:
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Octane Elite