BT-1 Data

Data Reduction

BT-1 data is typically collected over 11 degrees in 2-theta for 32 detectors. It must then be transformed to a 1-D pattern, multiples of which can then be summed with statistical weights taken in to account to give a final GSAS file (Convenient for use in EXPGUI). These files can be plotted, or saved in other useful formats using the CMPR software (thanks to Brian Toby, APS).

Windows executables of gformat and proprep with instructions.
Source code suitable to be compiled with g77 on most *nix/OSX machines. 

Notes

Process files with proprep -c1 file1 file2

Then you usually you only need to do this:  gformat -s file1 file2.... 

Though there are some further options available:

• -o will omit the background spline subtraction across detectors.
• -m will move points to closest bin
• -c will overwrite any previous data files; 'clobber'
• -a will apply absorption correction from file abs.corr
• -r will prevent rescaling to ~counts

If you use OSX you can use these pre-compiled versions osx.tar.gz(uncompress with "tar -xvf OSX.tar.gz", and note that the 2 'lib' files must be moved from their unzipped location (i.e. from that directory type: "sudo mv libgfortran.5.dylib /usr/local/lib." and give your password) You should probably move the 2 executables to somewhere in your PATH as well, for instance /usr/local/bin/. 

Data Plotting

The useful CMPR program by Brian Toby is available from the Advanced Photon Source, along with GSAS/EXPGUI and GSAS-II.

In our experience the APS site is sometimes unavailable so here are a few older (but available!) versions of these softwares:

• CMPR Windows and OSX (refer to the above installation pages as needed)
• EXPGUI Windows and OSX(10.6 or earlier) (refer to the above installation pages as needed) 

Sometimes, you may wish to do something different from the regular data collection. We have a few Python codes to plot temperature and H-field for a few circumstances. These programs assume that you have a functional python environment on your computer. These programs are installed on the BT-1 instrument computer (you only need to type 'readtemp', 'readtemp-1file xxxxx001.bt1' or 'BT1-plot xxxxx001.bt1'.) 

Plot the average temperature of all data points in a file, for all files in a directory DOWNLOAD 
This python program will read the temperatures of each data point collected in each BT-1 data file in the directory it is run from. 
The data is plotted for the mean T, a blue error bar for the std dev. and a red error bar that indicates whether the maximum deviation from the mean for each file listed horizontally. This is useful to quickly check for thermal equilibrium throughout data collection in one convenient plot. 
Usage: python readtemp.py 

Plot the temperature at each data point in a file DOWNLOAD 
This python program will read the temperatures of each data point collected in a given BT-1 data file. 
The data is plotted for each detector position. This is useful to check in more detail about the thermal history throughout data collection in one convenient plot. 
Usage: python readtemp-1file.py xxxxx001.bt1 

Plot the temperature or H-field at a fixed angle DOWNLOAD 
This python program will plot the temperature or (if available) the H-filed dependence of each data point in a BT-1 file. It is appropriate ONLY for those times when sitting on a particular Bragg peak and scanning T or H. The chosen detector (via the slider) dependence against T or H (if a BH1 file is available) is plotted. Data can be saved as det#.dat with the 'save' usa-button.  Warning - If there is random lines on the plot- you do not have the right type of measurement to make this plotting program useful! 
Usage: python BT1-plot.py xxxxx001.bt1

Data Refinement

Data refinement can proceed through a number of avenues, using a number of different softwares. The choice is up to the individual, but here we provide a simple set of data fit with a mostly gaussian peaks shape to start of the user. Please remember that the units in GSAS at in 100th's of a degree so most other software needs to have these values divided by 100 equivalent parameters.

Links to sample datasets taken at the BT-1 diffractometer using a sintered sample of alumina, kindly provided by Dr. David Cox of Brookhaven National Laboratory. This sample is a real-world sample, not a SRM. This sample contributes relatively minor amounts of broadening, so these data provide a good reference for the instrumental resolution. Data collection times vary with the requirements of the study, the quality of the material and the sample size, but the data collection times used for these measurements are representative of what is typically required for a sample with volume 3-10 ml. Files are provided in two formats: as REFINE .raw files, and as GSAS files (.gsas/.inst). 

Database

Internal to NIST? You have access to the Inorganic Crystal Structure Database - Search Page.