Advanced Photon Source

A U.S. Department of Energy, Office of Science,
Office of Basic Energy Sciences national synchrotron x-ray research facility

Glassy Carbon samples measured at UNICAT USAXS instrument

Jan Ilavsky, 2004-Sept-23

Five samples of glassy carbon manufactured by Alpha Aesar were measured at UNICAT and are used around the APS as secondary intensity standard. This web page lists the results obtained for the glassy carbon samples on UNICAT USAXS instrument. Data available here are fully desmeared and corrected, with absolute intensity calibration using USAXS standard-less absolute calibration method. The sample thickness is 1 mm.

The samples were denoted A, B, C, D, and E. Number of measurements were obtained on each sample to compare stability of measurements and samples together. The following graph shows reproducibility within one sample (sample denoted A).

As you can see, 3 measurements on one sample (in different places) are quite reproducible. Error bars (errors are available in files for download) are not displayed for clarity. Generally we have found out, that within one sample any variations of scattered intensity are likely caused by small changes in the sample thickness. These data were confirmed and better documented by use of DND CAT pinhole camera.

The following graph shows comparison of 5 available glassy carbon samples:

As you can see, there is significant difference in scattered intensity for the 5 different samples – especially at smaller Qs (below 0.1 A-1).

ASCII data

ASCII data file with Q (1/A), Intensity (1/cm), and error are available for download here:

Glassy_Carbon_A
Glassy_Carbon_B
Glassy_Carbon_C
Glassy_Carbon_D
Glassy_Carbon_E

Glassy Carbon A was currently cut into smaller pieces, each is identified by name (Adam, Bob, …). These samples are available for loan from UNICAT (Jan or Pete) and the ASCII data measured for these samples is available at the links above… If you have any questions, please contact Jan Ilavsky <ilavsky@aps.anl.gov>

Absolute intensity conversion

For details of the conversion of raw intensity to absolute units of differential scattering cross-section per unit volume per solid angle, please consult:

• Pete Jemian's 1990 PhD thesis, http://www.jemian.org/pjthesis.pdf, page 51, equation 83.
• G.G. Long, P.R. Jemian, et al., J Appl Cryst 24 (1992) 30-37.
  High Resolution Small-Angle X-ray Scattering Camera for Anomalous Scattering