TEXRAY LAB » Diffraction

Zero background sample holders for Siemens autosamplers

Posted by: Ken Stauver In: Uncategorized 20 Feb 2017 0 comments Tags: Bruker, crystallography, D500, D5000, D5005, Diffraction, Diffractometer, geology, Jade, Jade 2010, KS Analytical, Materials Data Inc, MDI, Phase ID, powder XRD, PXRD, quantitative XRD, Sample holder, sample preparation, Siemens, X-ray diffraction, XRD

The dreaded “amorphous” hump created by x-rays scattering off plastic sample holders has plagued XRD users for decades. It’s a serious enough problem that we make a good volume of these holders from Aluminum which works very well for loose powders. The plastic scatters xrays at around 13 degrees 2Theta (Cu anode tube) which make a real mess of most geological patterns and isn’t fun to model out for Rietveld refinement. Zero background holders like our ZBH-32 work wonderfully in standard sample stages designed for a single sample at a time, but the large plate isn’t compatible with the autosampler.

I recently had a request for a hybrid holder which would allow for analysis of very small volumes of materials while retaining compatibility with the autosampler. This is almost identical to our standard powder holders, but with a well designed specifically for our small ZBH plate.

Key features include:

6061-T6 Al material (anodized or as-machined)
Si(510) plate
Raised sample well minimizes the area of the sample holder in the plane of diffraction. (Original Siemens design)
Beveled well walls minimize the area of Al in the plane of diffraction
Other small modifications are made to improve reliability of these holders in the autosampler

Pure KA1 XRD with the Johansson monochromator

Posted by: Ken Stauver In: Uncategorized 20 Feb 2017 0 comments Tags: Bruker, crystallography, D500, D5000, D5005, Diffraction, Diffractometer, HR-XRD, Jade, Jade 2010, johansson monochromator, KS Analytical, Materials Data Inc, MDI, powder XRD, preferred orientation, primary-beam monochromator, PXRD, quantitative XRD, Siemens, X-ray diffraction, XRD, XRD data collection, XRR

One of the fundamental facts of lab-based X-ray production is that our x-ray tubes emit much more than the pure KA1 lines we rely on for material characterization and quantification. Most XRD users are familiar with techniques and hardware for the reduction or elimination of KB1, W LA1 and Bremsstrahlung, but take for granted the inseparable pair of KA1 and KA2 (referred to as the “doublet”). Luckily for us, these energies are present in strict proportion such that we can factor their paired presence into most XRD analysis to the point that one might barely notice their effect. However, the fact remains that we will see peak broadening at lower angles and completely independent additional peaks at higher angles due to this superfluous discrete emission.

Separating the doublet cannot be accomplished electronically or through absorption/attenuation such as might be effective for KB1 energies. It must be done in the primary-beam with an additional diffraction event. Primary-beam monochromators are generally classified by the number of diffraction events required for a photon to pass completely through the device. Single-bounce, 2-bounce and 4-bounce geometries are common with the latter providing the best energy resolution allbeit the lowest intensity (photon flux). My limited experience suggests that while the single-bounce models retain enough intensity to have some application in powder XRD, the others are relegated to HR-XRD applications such as XRR.

The alignment for any of this hardware is not for the faint of heart as it begins with coarse adjustments using fluorescent screens in the beam path. This was essential for us given how dramatically misaligned the monochromator had become after so many attempts to bring it back into operation. We actually needed our SDD system to verify that we were tuning for Cu KA1 energy rather than the KB1 emissions because some of the most basic aspects of the alignment had pushed way beyond their intended position.

Along the way we built ourselves a motorized remote adjustment tool which we’ll return to the user as small adjustments are required on a regular basis with this kind of monochromator to retain maximum intensity. It’s quite useful and even versatile enough to allow for the adjustment of multiple control knobs.

One final note regarding intensity. It’s easy to get excited about energy resolution like this, but bear in mind that we’re looking at ~20x reduction in intensity due to the inherent losses involved in the primary diffraction event. This data was collected at 10x the normal speed and at half the normal 2Theta step increment so it looks very good, but one would need a compelling reason to slow their data collection this much.

Another side effect of performing your energy discrimination in the primary beampath is that other issues such as fluorescence effects (incident x-rays exciting elements in the sample causing high background intensities) are harder to avoid than they would be with a diffracted-beam monochromator. The 4x reduction in intensity inherent in the diffracted-beam monochromatization makes it a poor choice to eliminate these effects when the incident intensities are already so low. We recommend energy-dispersive detectors such as our SDD-150 to eliminate extraneous energies without sacrificing net intensity. We’ve also worked with the Bruker LynxEye XE-T detector which has a very high energy resolution compared to other position sensitive detectors (PSD). Contact KS Analytical Systems for more information on these options.

Sample holder machining video

Posted by: Ken Stauver In: Uncategorized 05 Jul 2016 0 comments Tags: autosampler, Diffraction, Diffractometer, membrane filter, NIOSH 7500, Sample holder, Siemens, silica, XRD

XRD sample holders are easily the most common items we’re asked to machine. Sometimes it’s because they’re no longer available, but usually, it’s to accommodate some special application. Sometimes it’s as simple as making them from Aluminum to allow for cleaning with acetone or other harsh solvents. Other times it has more to do with the clients preferred style of loading or sample volume. The end result is that there’s very little consistency so our process needs to be as versatile as possible. This video highlights the most recent process. It’s hard to see exactly what’s going on through the coolant, but this is a test run of a program to cut special holders for 25mm filter membrane holders for respirable silica measurements (or anything else one might want to deposit onto a 25mm filter). It’s cutting the bottom of one holder and the top of another (each on its own side of the fixture). A full load of these produces 6 complete holders for every run.

Goniometer maintenance

Posted by: Ken Stauver In: Uncategorized 05 Jul 2016 0 comments Tags: Diffraction, Diffractometer, goniometer, Siemens, XRD

Siemens goniometers are about as sturdy as they come. Large diameter gears and bearings spread out forces across a wide area resulting in smooth and stable performance as well as very high load handling due to the added leverage of this arrangement. For this reason, they’ll run for many years even after the grease inside has become hard and contaminated with dust. Most users don’t even know their goniometer is getting stiff until we check it during a PM. Catching this before the goniometer starts to hang up saves thousands of dollars and weeks of down time. Our goniometer rebuild service involves complete disassembly of the goniometer down to individual ball bearings for a thorough cleaning. We’ve tried to duplicate this procedure on-site with very limited success as the large components are best cleaned in a full size solvent bath and it’s special brackets are required to avoid concentricity issues during reassembly. All the critical electronics are replaced during reassembly along with fresh lubrication. The best case scenario is that we catch issue far enough in advance to get a matching replacement goniometer rebuilt and shipped out. There are too many variants to keep rebuilt units in stock all the time. This way we only need to come to the site once to swap the goniometer and perform the necessary zero alignment. The old goniometer goes back in the same crate and we’re done in a day or two. Waiting till a hard failure of the goniometer means a trip out to identify the problem and disassemble the system. The goniometer is shipped in for a rebuild which can easily take a few days to complete before being shipped back along with a second on-site visit. I’d estimate the extra cost to be right around $6k plus the cost of shipping and two weeks of downtime. We certainly don’t mind going this route, but if it were my money, I’d rather spend it on a comprehensive check of the machine rather than emergency services.

These pictures are from one of our first full rebuilds. This instrument was installed in a D5000-MATIC instrument at a cement plant. I’ve never seen so much dust inside a goniometer. Another particularly rough one was from a horizontal goniometer on a single-crystal system at a university. The students had a terrible habit of breaking Si(100) wafers and dropping them onto the goniometer face. Those little shards made their way into the bearings resulting in a rather perilous rebuild with shards of Si throughout it.

Zero background sample holders

Posted by: Ken Stauver In: Uncategorized 17 Apr 2015 0 comments Tags: Advanced X-ray Analysis, Bruker D5000, crystallography, D500, D5000, D5005, D8, Diffraction, Diffractometer, Energy-dispersive detector, Jade, Jade 2010, Jade 9.5, KS Analytical, Materials Data Inc, X-ray diffraction, XRD, XRD data collection, Zero Background Holder

The majority of the samples we receive come in volumes high enough to completely fill the well in any of our standard sample holders. Some are too large or oddly shaped which calls for a special holding solution like those listed here, but many are simply very small quantities of powder. Placing these in a standard holder would leave them well outside the plane of diffraction and provide terrible data, not to mention substantial scatter
or diffracted background from whatever the powder is placed on. The answer is a zero background sample holder (ZBH). Most our users at KS Analytical Systems run the original Siemens/Bruker plates, but others are using Si(100) and even glass substrates. We’re very happy to say that
we’re able to offer a direct replacement for these with our new ZBH-32 holders. These fit most Siemens XRD systems and can be customized for use in most any other system. Contact us for more information on this. The scan below shows the data collected from a single mg of Silicon 640B standard powder spread across a ZBH.

Full scan of 1mg Silicon 640B standard spread across a ZBH

ZBH-32 sample holders mounted for Siemens and Bruker single sample stages.

Some users report acceptable results using simple glass plates. While there are serious caveats here, it may be a reasonable solution for some users. The issue with amorphous glass is not diffracted peaks in the background, but rather, scatter off the surface. X-ray scattering off a surface is inversely proportional to the average atomic number of that material. That is to say, the lighter the matrix, the more efficiently it will scatter X-rays. This is why we use a pure Graphite sample to characterize the emission spectra of our XRF instrumentation. The glass sample shows the expected scatter “hump” starting at a very low angle and it doesn’t flatten until nearly 100°2Θ. While some of this can be modeled and subtracted with good profile fitting software like Jade 2010, it can be challenging to match the data quality of a good ZBH. We’re working on a series of videos to guide new users through some of these features, but on-site training classes are also available.

Amorphous glass empty

Glass, ZBH-32 and off-planar quartz scans overlayed for comparison

Several of our customers in the geological industry use standard Si(100) wafers. These can be a great solution, but again have serious drawbacks for some applications. The Si(100) material creates diffracted peaks which are very sharp and therefore easier to model out sometimes, but also very high as the material is monocrystalline. The scan below shows what happens when one tries to run a normal scan across a bare plate. The largest peaks are actually only one or two which have over loaded the detector and caused it to drop out. All of these scans were collected with our SDD-150 which can handle up to 1×10^6 cps, but for the sake of good comparison, we left it tuned as it would be for a standard pattern. The monocrystalline nature of this material causes big problems, but it also allows for a creative solution. See the second scan for the results of the same measurement with the plate angled 1 degree off of theoretical. With this geometry, it’s unlikely this would affect the data quality dramatically, but the offending peaks are drastically diminished.

Si-100 empty

Si-100 standard vs skewed scan

Off-planar Quartz holders have been the industry standard for decades. Historically, these have been made from solid, monocrystalline quartz material cut at a specific angle (6° off the C axis if I’m not mistaken). While these work well, they can be inconsistent. Even some of the OEM holders we’ve tested have shown some peaks which we can’t explain. Talking to some very experienced crystallographers, we find that they’ve had similar experiences.

Off-planar Quartz empty

ZBH-32 empty

We’ve been looking for a better answer for several years, but there are few off-the-shelf materials which work as well as off-planar quartz. The ideal answer was to cut solid Si(100) oriented billets such that the face presented to the diffractometer had no d-spacings which would diffract in the normal range of these machines. This is not unlike the off-planar Quartz method, but the starting material is much more consistent and durable. Si(510) offers very low background as well as the consistency of a manufactured product. The new ZBH-32 sample holders from KSA come in two versions, ZBH-25 and ZBH-32 with the latter being ideally suited for rotating stages and low angle work.

Film effects on XRD data

Posted by: Ken Stauver In: Uncategorized 27 Nov 2014 0 comments Tags: Bruker D5000, D500, D5000, D5005, D8, Diffraction, Diffractometer, Energy-dispersive detector, film, Jade, Jade 2010, Kapton, KS Analytical, Materials Data Inc, MDI, Mylar, Polycarbonate, Polyimide, Prolene, PXRD, X-ray, XRD, XRD data collection

Our recent sealed sample cell project required a thin covering film to be applied over loose powder before analysis by XRD. We tested a few options for this film as part of the design process and the results were interesting enough that we thought it would be worth dedicating a full post to that data and expanding the range of materials a bit to satisfy our curiosity.

All data was collected on our primary powder system. This is a Siemens D5000 configured with a theta/theta goniometer, automatic anti-scatter and divergence slits, a standard sealed Cu tube (LFF) and our new KSA-XRD-150 detector system. We alternate between a digital phi stage, 40-position autosampler and the standard, single sample stage which was used in these experiments. I had a spare sealed-sample cell available which made it easy to exchange the films without disturbing the sample surface. The design of these stretches the film taught each time the cell is assembled. I’d originally tried to simply lay the film over a side-load holder, but without being tightly held, it would buckle enough that results at low angles were probably affected. A NiO standard powder was used due to its high purity and compositional difference from any of the film materials.

The data clearly shows that Polyimide was the best choice for this application as it resulted in very limited attenuation as well as an extremely minimal increase in background intensity/amorphous scatter. Some of the other patterns were very interesting though.

Scotch “Magic” office tape. Adhesive side down.

Scotch “Heavy duty” packing tape. Adhesive side down.

Energy dispersive detectors for XRD systems

Posted by: Ken Stauver In: Uncategorized 20 Nov 2014 0 comments Tags: Bruker, D500, D5000, D5005, D8, Diffraction, Diffractometer, Energy-dispersive detector, KS Analytical, powder XRD, PXRD, X-ray, XRD, XRD data collection

Energy-dispersive detectors have been in use on XRD systems for decades, but have always come with caveats. Low energy resolution, Liquid nitrogen cooling, slow start-up and tedious/cryptic tuning controls have limited their popularity in many applications. Silicon Drift technology solves most of these issues and modern electronics covers the rest. The new KSA-SDD system for X-ray diffraction utilizes a full spectrum EDXRF detector which is fully software tuned. The result is a detection system with high enough energy resolution to match the performance of the traditional diffracted-beam monochromator/scintillation counter combination without the inherent 75% intensity drop. The increased countrate allows for much faster data collection speeds with the same counting statistics. We’ve been using this technology at our in-house testing lab (Texray Laboratory Services) for several months to great effect while we refined the system and are now ready to open it up to all XRD users. Contact us to discuss options for integration into your diffractometer.

SDD-XRD-150 installed on a Siemends D5000TT PXRD system. This is one of the powder systems we operate at Texray-Lab.

The detector mounts directly in place of the original scintillation counter.

Speed

Scanning 3-4 times as fast as the traditional scintillation counter/diffracted beam monochromator yields nearly identical results.
Scanning at the same rate results in much smoother scans, greatly improved statistical data and lower limits of detection/quantification.

Complete scan of Novaculite Quartz with a diffracted beam monochromator and scintillation counter vs the new KSA-SDD-150.

5-fingers of Quartz scan of Novaculite Quartz with a diffracted beam monochromator and scintillation counter vs the new KSA-SDD-150.

Energy resolution

140eV under ideal conditions.
All KB peaks eliminated electronically.
W LA1 (8.40 KeV) lines eliminated from Cu KA1,2 (8.04 KeV) scans even with thoroughly contaminated tubes.
Common fluorescence energies (i.e. Fe when Cu tube anodes are used) are greatly reduced. (Bremsstrahlung effects are impossible to remove completely)
Most PSD detectors offer no better than 650eV. This allows for a great deal of fluorescence energy to pass as well as W LA1 from older Cu tubes.

Low angle scatter

The detector mounts in place of the traditional scintillation counter allowing for use of automated variable (motorized) or interchangeable aperture slits to control angular resolution. Scans starting from 0.5 degrees 2? are possible with the proper slit arrangement just as they are with the scintillation counter. The user controls the intensity vs angular resolution of the scan based upon the ideal conditions for their work rather than the limitations of the hardware.
Position sensitive detectors are wide open by design which necessitates knife edges over the sample and additional mechanical aperture plates to block air scatter at low angles. Closing off the detector limits the useable channels and reduces the benefit of these detectors dramatically.

Minimal low angle scatter due to the use of standard aperture slits.

Cu KB1 and W LA1 energies diffract from the 100% peak of Novaculite in between the two primary peaks shown here. Tests with a severely contaminated tube showed no W LA1 passing through the discriminator.

Truly zero maintenance design

No delays – The detector is ready to collect data almost as soon as power is applied.
No external cooling – Air backed Peltier cooling eliminates the need for water circulation and/or liquid nitrogen.
Zero maintenance vacuum design eliminates reliance on an ion pump/backup battery.
12 month warranty against hardware failure under normal use.

Versatility

The Digital Pulse Processor (DPP) includes a usb interface allowing for adjustment and refinement should they be necessary for a particular application. With optional software, full quantitative EDXRF analysis can be performed.
Compatibility with grazing-incidence attachments and parallel beam optics for analysis of thin films.

The detector can be set for any common XRD anode (energy) easily. Multiple energies may even be configured to allow for use with various anodes without the need for additional hardware. We specialize in Siemens (now Bruker) XRD and WD-XRF instrumention and have installation kits ready for the D500, D5000 and D5005. The output is a standard BNC cable with a 5V square pulse output which is standard across every manufacturer we’ve worked with. Kevex and Thermo Si(Li) detectors used this same output.

Please contact KS Analytical Systems for a quote.

Air-sensitive sample cells

Posted by: Ken Stauver In: Uncategorized 16 Nov 2014 0 comments Tags: Diffraction, Diffractometer, powder XRD, PXRD, reactive, sample preparation, X-ray diffraction

Some months ago we had a pair of scientists visit our space to look over a refurbished Siemens D5000. Interestingly enough, they’d planned to use the system for some basic XRD, but mainly for the development of polycapillary optics. This is a fascinating new technology that’s gaining steam out in the R&D centers around the world and merits a full post dedicated to it ASAP. This is the type of “game changing” innovation which hasn’t come along in XRD in decades. They took delivery of their machine a few weeks ago, but while on-site they asked about another project. All that’s really needed is simple phase analysis by XRD with one complication, the material reacts violently when exposed to air.

We roughed out a basic design the same day, but that was only the beginning. Dealing with materials like this necessitates careful consideration of all material and procedures involved in getting it from the lab where it’s synthesized to ours and back. The final design involved billet Aluminum, BUNA rubber o-rings and polyimide (Kapton) film and took quite a while to flesh out. The end result is a complete system which allows the customer to load the samples into individual cells inside their own glove box. The individual cells can be loaded into the case inside the glove box as well. The outer o-rings on the cells seal against chamfered edges on the pockets of the case creating a second sealed area above and below the sample. It’s unlikely that the inner cell would ever rupture, but this protects the polyimide film and adds a substantial extra level of safety.

This is the complete case as it will ship. The flat-head bolts hold everything together and provide the necessary force to seal the chambers.

With the case open, you can see the individual cells along with the top and bottom of the case. The labeling shouldn’t be necessary since there are strict protocols in place for transportation of this material, but it never hurts to be cautious.

The original design called for a slightly more secure seal, but when we started working up the procedure to assemble them, it became clear that something simpler was needed, particularly considering that these will be loaded in a glove-box. An 11th hour rehash necessitated new o-rings, modification of the outer cell rings and complete redesign and fabrication of the cell center sections. I think this was well worth the effort though as they’re much easier to assemble now. There’s even a nice little tool to make it easier to open them back up for disposal or reloading. The original design would have been essential disposable.

Flexibility, versatility and adaptability

Posted by: Ken Stauver In: Uncategorized 14 Oct 2013 0 comments Tags: crystallography, D500, D5000, D5005, Datascan, Diffraction, Diffractometer, Energy-dispersive detector, Jade, Jade 9.5, KS Analytical, Materials Data Inc, MDI, PXRD, Siemens, Thin-film, X-ray, XRD, XRD data collection, XRR

A large part of our business at KS Analytical Systems is refurbishing and reselling WDXRF and XRD instrumentation. We specialize in Siemens and Bruker models because, and I can’t stress this enough, they last. Siemens was 20 years ahead of their time with features like full computer automation, interlocked radiation housings (not just an enclosed beam path) and independent axis control coming standard on most systems. The D500 may well be the most reliable powder diffractometer ever built and for most of our history, it’s outsold all other models of XRD and XRF combined. Most users are simply performing basic powder scans with many running the optional 40-position sample changer, but I always get excited when I find someone pushing the limits of the platform.

Several years ago I was approached by a new professor at a major American university about purchasing a refurbished Siemens D500 XRD. He’d been seriously considering a new instrument from one of the big-three OEMs, but chose to focus on the D500 due to its reputation for low cost of ownership, versatility and nearly identical resolution/intensity to the new system he’d been looking at. It’s been a few years since that unit was delivered and I’ve been very impressed with the improvements that have been made.

The first step was to bring the software up to date with a complete package from Materials Data Inc. (MDI). This included Datascan 5.0 for instrument control and data acquisition as well as the flagship Jade 9.5 analysis package. Whole pattern fitting (Rietveld), semi-automatic phase ID (Search/Match) and a host of other advanced quantitative and modeling options are included. Jade 9.5 is modular and can be purchased with any combination of these options. I’d estimate that 70% of the XRD systems we sell go out with some level of MDI package. We’ve been working with them for 20 years now and have never heard anything other than glowing praise for their excellent products and support. One key feature of Jade is that it was designed to be a universal analysis solution from the ground up so there’s never a problem opening any of the OEM file formats. It’s much easier to justify the cost to upgrade your software when you know it will integrate seamlessly with any other data or instruments you may encounter. Contact KSA if you’d like more information on this.

This is Jade 9.5. You’ll notice that it’s a much different interface than the Jade 2010 program I usually use. This option is modular with available plug-ins for all the higher level functions of Jade 2010, but 9.5 is perpetually licensed.

This is actually the VirtualXRD program that comes along with Datascan. I don’t use it often, but some of my users run extremely long count times and predicting the affect of a parameter change could save them days of experimentation. It’s a great tool even for users running simple 1 hour scans.

The next step was more hardware based than anything else. The independent axis control of the D500 (in Theta/Theta or Theta/2Theta configurations) allows for both rocking curves and grazing incidence scans. With the goal of analyzing thin-films in mind, we upgraded the D500 with a grazing incidence attachment. These are designed to minimize scatter while the sample is held at a shallow (usually 3 degrees) incident angle and the scan is performed with the detector alone. The attachment consists of a long collimator coupled with a simple monochromator just before the detector. We’ve performed some rather intense studies with one of these at Texray and were very impressed with its performance. In fact, we use it whenever practical even though we have a dedicated parallel beam optics system in the lab as well. It was about time for a new tube so a new, ceramic Cu long, fine focus tube was included in the upgrade.

Some additional software solutions were developed on-site to facilitate XRR (X-ray Reflectivity) measurements around the same time. I confess that this is not something I’m personally very familiar with, but it seems fascinating. It involves scans at extremely low angles which can require caution since one is working with a very nearly direct beam.

The last upgrade he made is actually the one that most impressed me and the one I had absolutely nothing to do with. In an effort to further expand the capabilities of his instrument, he purchased and installed an energy dispersive detector with an integral digital pulse processor (DPP). Clever mounting and some experimentation allowed him to perform EDXRF elemental (qualitative AND quantitative) analysis on samples while using the D500s X-ray tube as the primary emission source. The flexibility of the D500 platform even allowed him to control the effective layer depth by adjusting the incident beam angle. Since his application involved analysis of a thin film coating, he set the goniometer to a low angle to minimize penetration depth and substrate interference. After seeing how well this worked, I immediately started working on a similar upgrade that we could offer to all our current and future XRD users. I’ll detail my early progress in the next post.

Minimum start angle tests

Posted by: Ken Stauver In: Uncategorized 01 Oct 2013 0 comments Tags: crystallography, D500, D5000, D5005, D8, Diffraction, Diffractometer, KS Analytical, PXRD, Siemens, X-ray, XRD, XRD data collection

All of the powder XRD (PXRD) systems we work with use either manually interchangeable aperture slits or automatic (stepper motor driven) slits to control divergence and scatter. One of the most common questions I hear from new users is “What is the ideal slit arrangement”. While I realize that there are many instruments out there with “one-size fits all” slits, the D500, D5000, D5005 and D8 optics are what I call “Research Grade”. This means that they can be adjusted and tuned for a particular application to maximize effects that are desirable and minimize those which are not. One of the most common reasons to change the anti-scatter and divergence slits is to reduce scatter over the sample at low angles. This scatter is the primary limiting factor for users who want to see diffracted peaks at very low angles. At Texray, we offer instrument time (data collection) as one of our services and have received requests for starting angles as low as 1 degree 2theta so it occurred to me that now would be a good time to collect some reference data and answer this question once and for all.

The image on the left shows the effect that the anti-scatter and divergence slits have on low angle scatter. The image on the right is of the two primary reflections of quartz (Novaculite) with the same slits. Note the intensity loss. The benefit of automatic slits is that they can be set very small at the beginning of the scan and gradually open up throughout the angular range. Very few users need that kind of flexibility, but since we’re talking about slits, it bears mentioning.

This data was collected with matched slits set at 0.2mm, 0.6mm, 1mm and 2mm. These correspond to practical starting angles of 0.6, 0.9, 1.4 and 2.5 degrees 2theta respectively.

Looking at the actual peaks, you can see the affect the smaller slits have on the rest of the data. These were collected without the benefit of a diffracted beam monochromator and with the primary soller slit removed. Neither of these factors would have a dramatic impact on the result, but the lack of a primary beam soller slit explains the asymmetrical peak shape in the second scan range pictured.