This page contains the list of (Youtube) videos I have made over time explaining SAXS and some of its workings. They are mostly sorted in order of appearance (newest on top)

A user interface for McSAS (more information):

A new Live Fourier Transform demonstration (more information):

Introducing dr. Julian Rosalie (more information):

Introducing dr. Shivani Sharma (more information):

Some new 2D fitting work I am developing at the moment (more information):

A presentation detailing my current work (more information):

A presentation with advice for scientific presenters (more information):

A presentation discussing a small-angle scattering technicality, what is the visibility of particular sizes in polydisperse samples? (more information):

A promotional video for a NIMS workshop:

A demonstration of small-angle scattering from a hair. This is a demonstration in which beams of laserlight (two lasers with different wavelengths are used to demonstrate the effect of different wavelengths as well) is shone upon two human hair samples. A small-angle scaattering pattern is seen on a whiteboard and analysed to determine the diameter of the hairs.

…and the calculation of their diameters from the small-angle scattering pattern

A demonstration of what we would see when we scatter from some samples, using a live Fourier Transform image of a laptop camera:

An explanation of what I did from 2009 to 2011 with a concise SAXS explanation and some elaboration on analysis methods:

A short explanation of small-angle scattering:

Hey!great videos, thanks!but i think at the 3rd one, where you calculate the diameters, towards the end of the video (around 4:17) you say q is wavelength independent, do you mean r is independent since you calculate q taking into account wavelength?

Hi Celen,

Thank you for your question. The definition of the scattering angle

qmakes this scattering angle independent of wavelength (this is achieved by dividing by the wavelength). Anything we calculate using q, such as the radius r, will then automatically also be wavelength independent.So, if I understand your question correctly, the numerical values for the angle q are already wavelength independent because of the way we calculate these q-values.

This is not the case in the diffraction world, where the angles are usually given in degrees. While degrees are more closely associated with the concept of angles, these degrees are only useful if the wavelength is also given for that particular measurement.

Please let me know if this answered your question, otherwise I’ll try again :).

Good afternoon Brian,

I wish to incorporate your video, entitled: “Small-angle X-ray Scattering (no voice-over, no closed caption)” in my x-ray safety training for my students. May I have your permission to do so? I will acknowledge your authorship of this clip in my presentations.

Thanks for kind consideration.

Auggie

Hi Auggie,

Sure thing, I’ve sent you the links to the full-scale versions in an e-mail.

Cheers,

B.

hi nice vids,

I wish to use your hi-res video in one of my presentations,

thank you very much.

Your videos seem to imply that scattered intensity can pass through the beam stop. This doesn’t seem to make any sense.

Dear Marty, That was more due to a limitation in my raytracing skills rather than a lack of understanding. In the simulated data and model data the beamstop is not explicitly drawn. Once I learn something else (Blender or somesuch), I might be able to update some of the videos, but until then I’m afraid there’s not much I can do.

Hi Brian,

I’d like to use your video “Small-angle X-ray Scattering (no voice-over, no closed caption)” in the ppt presentation of my diploma thesis which is based on usage of SAXS in regards of conformation of biopolyelectrolytes. May I have your permission to do so? I will acknowledge your authorship of this clip in my ppt.

Thanks

Hi Brian,

Whats difference between SAXS and XRD .

Dear Raksha,

That’s a good question, there are some similarities and some differences. I think it may make a good topic for a video, but here are the highlights:

The similarities are that:

1. Both techniques measure the intensity as a function of angle, though the angles are typically smaller in SAXS than XRD.

2. Both techniques show peaks for periodic structures, the larger the periodicity length, the smaller the angle at which the peak shows itself.

3. for any structure (crystalline or non-crystalline), there is a [000]-reflection. This is the one whose peak broadening we are typically investigating in SAXS.

4. Like XRD, we have a phase problem. We cannot say whether we are scattering from electron-dense objects in a “light” matrix or the other way around

The differences are that:

1. SAXS does not require the material to be crystalline. Any structure will affect the scattering pattern.

2. We don’t consider the scattering to be from individual atoms, but rather from contiguous regions of similar electron density.

3. We typically don’t have as many angles to worry about as the diffractionists, so perhaps SAXS is easier :)

Hope that helps!

B.

Hi Brian,

That was very good information,thanks for sharing.

I am currently working on XRD . Can we perform SAXS analysis of a tablet, a whole tablet i.e without crushing?

Can this technique be used for quatification analysis?

Regards,

Raksha

Dear Raksha,

SAXS on a tablet (in transmission mode) should be possible, but beware of nanostructure created in the tablet pressing procedure. In other words, if tiny pockets of empty space, voids or cracks are generated when you press a tablet, those will show up in the SAXS signal.

Best way is to try it and see what you get. Also, a good way to test is to try and look at the tablet structure under an electron microscope to get an idea of what you will see in the SAXS signal. If you want to see a diffraction peak of a very large lattice parameter, you’re probably fine. Check out what thickness you need to get the X-ray beam through your tablet using the site here:

http://11bm.xray.aps.anl.gov/absorb/absorb.php

SAXS can be used quantitatively if you have a good idea what the phases in your system are. For this, you will need an absolute intensity calibration standard.

Cheers,

Brian.

Thanx Brian

Hi Brian!

I would like to ask you how does the SAXS help to identify the pore shape (the network system) of the porous materials ?

Thanks in advance.

Hello Youssef,

Thanks for asking. If you are talking about ordered pore structures (like from etched block copolymer systems), the resulting diffraction peaks at small angles can tell you something about the structure. I have very little experience with these, so I’ll point you to Martin’s review for those: http://pubs.rsc.org/en/content/articlelanding/2013/cp/c3cp50293g

As for non-ordered porous systems, there are two options: either your sample has an aligned porous structure (giving you an anisotropic scattering pattern) or it has a non-aligned porous structure. In the first case, *some* information can be gleaned from the scattering pattern on the pore shapes.

In the second case (isotropic scattering from a porous structure), it is usually not possible to separate the pore shape from the polydispersity. The scattering pattern itself can be fit using a multitude of models, each using different pore shapes and polydispersities. In other words, if you change the assumptions on the elementary shape of the pores (e.g. from spherical to cylindrical), you can still find a polydispersity that will allow you to fit your data. More information on that in the introduction of my open-access review paper: http://dx.doi.org/10.1088/0953-8984/25/38/383201

Good luck!

B.

Hello,

Yes it’s about ordered mesoporous materials (with block copolymer as a surfactant), where SAXS ‘s been usually used to identify the structure or to confirm images got by the SEM (Scanning Electron Microscope) or TEM (Transmission Electron Microscope).

Thanks a lot.

Hi Brian!

First of all thank you for your nice videos.

Can you do any video for SANS and SAXS date analysis?