Comparisons of Doom: line vs. pinhole.

Line-collimated instrument (top, not a SAXSess), versus a pinhole-collimtated instrument (bottom, not a Nanostar)

[ed: My current project is running at an end, so if you happen to have a job offer I cannot refuse, I will seriously weigh it against the (tenured) job offer I got from NIMS!]

The typical argument in favor of the line-collimated “Kratky”-type instruments is that its X-ray flux is very high and that therefore you need only short measurement times. However, its data needs to be corrected through a “desmearing”-procedure, amplifying uncertainties and noise in the process. Does this approach then really give you better data? Let’s find out! Read more »


To the States, and other cutting-room clippings

Capillary holder in action

Dear readers,

As you read this, I’ll be trying to get to the Denver X-ray Conference in Montana. I’ll be giving a talk there on Friday morning introducing small-angle scattering to fellow X-ray afficionados and hopefully convert a soul or two to the narrow field we’re in. Please come and say hi if you’re around, or contact me on my twitter account (connectivity permitting), user @drheaddamage. I have two small bits I want to talk about today: a new sample holder and 3D SAXS. Read more »


Today is a holiday, short note on data corrections

Dear readers,

Unfortunately, this week I do not have anything ready for you. It is with great regret that I must therefore skip this week, and break my “once-a-week” posting schedule. Regular scheduling should return next week.

Just a quick note, however. Thanks to Sylvain Prévost bringing this back to my attention; Brûlet et al. derived a very similar equation to what was derived in last week’s post. Additionally, Strunz et al. [2] have some additional considerations for transmission factors that may need to be considered in X-ray scattering as well (in particular for ultra-small angle X-ray scattering).

Hopefully I will have the time to look into these things in the near future and give you some more insight on the magnitude of these problems. As suggested by Sylvain, it may be a good idea to adapt the “imp2″ data reduction software to be able to handle a more general consideration of transmission factors (then supporting both SAXS and SANS). A bit of thought is needed on how to enable fancy background subtraction while keeping the modular, flexible nature of the program.

[1]: Annie Brûlet, Didier Lairez, Alain Lapp and Jean-Pierre Cotton, “Improvement of data treatment in small-angle neutron scattering”, J. Appl. Cryst. 40 (2007), 165–177. [journal link], [free link]

[2]: P. Strunz, J. Scoversheet.dviaroun, U. Keiderling, A. Wiedenmann and R. Przenioslo, “General formula for determination of cross-section from measured SANS intensities”, J. Appl. Cryst. 33 (2000) 829–833. [journal link]


Lessons from history: a look at GE’s early outreach videos

A portrait of Dr. Coolidge seen in the movie "Exploring with X-Rays, Part 1" from GE.

[ed: I'm giving a general SAXS talk at BESSY, the Berlin synchrotron on Friday the 11th at 10:00 local time. Contact me or Andreas Thünemann at BAM for more information]

Whenever I think of General Electric, I imagine a stereotypical American company: a top-heavy organization, forcing its employees to learn and recite GE’s mission statement, run by armies of beancounters and administrators who are trying their best to increase value for the shareholders while running everything else into the ground. This, of course, in stark contrast to the academic world typified by: a top-heavy organization, encouraging its undervalued employees to slave away for the dream of doing something of worth in the little time they have left besides doing administrative tasks, while the army of beancounters and administrators are trying their best to satisfy the research assessment committees and running everything else into the ground. Anyway, I digress…

GE has released some films from their early days of bright bulbs working in their research laboratories, some of which are very relevant to X-ray sciences. These videos are very interesting for a variety of reasons… Read more »