Unsurprisingly, Lancaster’s School of Engineering has some very cool, very expensive kit. From robotic arms to wave tanks, to full nuclear research labs (more on those another week), there’s plenty of equipment for a budding or even a seasoned engineer to get excited about. But nestled in the bowels of the new Engineering building, lives one of the most expensive pieces of equipment on campus: A million pounds-worth of Scanning Electron Microscope – or more specifically, Scanning electron microscope Analysis with FIB, EBSD/EDS and Raman system, or SAFER for short. And alongside it, the man who runs and looks after this gargantuan piece of machinery: Dr Richard Wilbraham, Experimental Officer for both the SEM labs and the UTGARD Nuclear facilities. He’s a piece of Lancaster furniture at this point, having completed his PhD here some 15 years ago and been here in various capacities ever since.

Richard in his natural environment with the SAFER system

Richard very gracefully elected to put up with me badgering him with questions about his work for the afternoon, so invited me down to the SEM labs to come and learn more about his day-to-day as the person in charge of the SAFER and X-Ray Diffraction facilities.

Today, he was running some tests on samples of ruthenium dioxide, sent in by a PhD student. The student (a nuclear engineer), is working on ways to recycle nuclear fuel rods and extract the useful uranium from them for re-use, sifting it out from the other products of fission, such as plutonium, neptunium, and the aforementioned ruthenium! Fuel rods are typically initially dissolved in nitric acid, but this student is working on ways to improve the process by adding silver ions (specifically, Ag+) to the mixture, to see if this makes the recycling process more efficient. But what he wants to know is if the silver does anything to the fission products, such as plating onto them – which is where the SAFER system comes in! This SEM is able to both image microscopic samples as well as detect what atomic elements make them up, so it’s perfect for this task.

First things first, Richard has to prepare the sample on an aluminium “stub”, which will be slotted into the machine. The sample is attached to the stub via a carbon sticker, and is then sprayed with a healthy amount of compressed air to remove any loose contamination:

Some pre-prepared stubs with a variety of samples stuck to them.

After that, into the machine the sample goes! Richard opens the drawer and installs the stub – gloves are a must to avoid contaminating the chamber, when you consider this machine can image things as small as a 70,000^th the width of a human hair, even a small amount of dust will ruin the results!

Richard installing the stub in the SEM chamber of the SAFER system. The funnel he’s pointing out is the nozzle of the electron gun.

To analyse the sample, the SEM’s electron gun fires a beam of electrons into the chamber, focused using electromagnets onto the surface of the sample. This causes a secondary electron to be ejected from the sample (as the beam’s electrons interact with the sample) which are then picked up by a detector. The beam is rasterised across the sample to measure the signal at each electron site, like refreshing pixels on your TV, which produces the final image. All of this is done under vacuum – as the presence of other atoms would disrupt the electrons reaching the sample. It takes about 15 minutes for the SEM to produce an image, depending on the resolution needed and the size of the sample.

After that, we turn to the monitors to see what we’ve got! The SAFER system runs on 3 separate computers: one for the SEM itself, one for the elemental analysis software, and one for the Raman spectroscopy (which isn’t being used today):

The SEM in action – you can see the image of the ruthenium developing on the left.

Since the student is needing an elemental breakdown of what’s in the sample, Richard is going to run the elemental analysis too. The detector, EDS - or “Energy Dispersive X-ray Analysis’’ in full – can identify and tell us the weight or atomic percentage of elements from the periodic table in the sample by analysing the x-ray energy given off when an electron is ejected from the sample. Different elements have different electron configurations, so the energy of the X-ray produced when hit by the electron beam will differ depending on where in the electron shell configuration it comes from.

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The EDX profile for the sample. The peaks can indicate where certain elements might be present. The yellow indicates the profile of ruthenium, the orange indicates silver. Bit of a problem – ruthenium overlaps a lot with silver!

Unfortunately, it turns out that ruthenium and silver actually overlap in their energy peaks, so it’s difficult to tell which is which! These results do suggest that if there is silver present, there’s not a lot of it at any rate. Richard decided to map the sample in colour to see if there are any areas particularly rich in silver:

The full spectra colour image of the sample provided by the SEM – lots of ruthenium and oxygen, some carbon from the sticker it’s attached to, but no real indication of silver!

No dice here either! Oh well, these inconclusive results are sent back to the student – they’ll likely have to perform some other types of analysis to find out if there is any silver in their sample.

Richard’s other job for today (aside from reams of paperwork which I deemed too boring to document) is to maintain the X-Ray Diffraction device in the other room . Since the X-Ray Diffractometer is a classified radiation source, Richard has to test it at least once a month to ensure that it is safe to use and working correctly. Unlike the SEM, this device is firing high energy x-ray beams at samples rather than just measuring the very weak x-rays that are produced as a side reaction of electron imaging, meaning that there is a more significant radiation hazard to be aware of.

The X-Ray Diffractor, looking appropriately worthy of a sci-fi film.

First things first – let it boot up and condition the x-ray tube. This doesn’t mean lather it in Head-and-Shoulders; rather the voltage and current are gently ramped up on the tube to keep it in good working order. After that, Richard loads in an aluminium oxide standard into the device to begin the tests. First test is passed – it just needs to light up yellow to tell us that the generator is working! Then, he has to make sure that the warning lights appear when the door is open and the shutter is up, and fire up the x-ray beams to check that the radiation warning lights also appear. All good on that front!

The most important tests come next: checking the chamber to make sure that it isn’t leaking. To do this, Richard first checks out background x-ray levels using an x-ray monitor, it measures when x-ray radiation enters the monitor and turns it into an electrical pulse, measured in “counts per second”. Our background radiation is at 14 cps:

Richard’s radiation detector. 14 cps is a normal level for background radiation, so good news for us.

Next job is to compare the radiation levels around the chamber to check for leaks. Richard must scan each panel to ensure there are no issues in any area of the machine. A result of double the background radiation is grounds to call for an investigation and stop all usage of the diffractometer:

Richard checking the radiation levels around the front of the cabinet. Ironically, all of the readings around the cabinet are lower than elsewhere in the room!

No leaks from the cabinet - which was a relief for me, I get enough X-rays from the dentist! The final checks are to run alignment checks on the x-ray beam to make sure that the beam on the moving arms is aiming at the sample. Another passing mark here too:

Richard uses a built-in laser to check the alignment of the beam. A dead centre hit, so all is working as it should!

Then, all that’s left to do is run a scan on the aluminium oxide sample and check it against the previous month’s scan to make sure that the detector is operational. The results could be a copy-paste of the January test, so it appears that the X-Ray Diffraction unit is in tip-top condition and can remain in use!

This piece of equipment can provide a more detailed compositional analysis of samples compared to the SEM (but without the pictures). Rather than telling us the individual elements that are present like EDX did, in this case Al and O, it can give us the exact compounds and crystals present in a sample, for example in the standard here Corundum (Al₂O₃), so it’s important that it is in working order and providing accurate results to support the work for researchers from across our University.

Richard, however, wears two hats at the University; whilst he runs the SEM facilities for half of his time, he is (as aforementioned) also in charge of the UTGARD nuclear facilities, based in the Science and Technology building. I’ll be following him around to find out more about his work there soon, so stay tuned!

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