FAQ | 12-BM

Data quality and acquisition time strongly depend on how to prepare samples.
Sample thickness and uniformity are the key controlling parameters.
Ideal thickness? 1 ~ 1.5 x absorption length.
"Preparation of XAFS Samples" by Grant Bunker(IIT).
"Sample Preparation for EXAFS Spectroscopy" by Rob Scarrow.
Here is a useful link from IXAS to calculate the thikness of samples for transmission mode.

Transmission mode : three ion chambers with 100 MHz converter: V2F100
Fluorescence mode : Vortex 7 elements or 13 elements Ge detector processed by Xspress3 (count rates up to 4 Mcps)

It varies by scan range, sample condition and concentration of samples.
Typical step scan (1 sec/step) takes ~15 min with full exafs range up to k = 15 1/A (~850 eV above edge energy).
Quick EXAFS is also available for in-situ measurements. It takes less than 10 sec for full EXAFS scan.

The data files are plain text file with multiple columns. The file can be imported as a text file with various text editor or spreadsheet programs.
We recommend to use dedicated XAS data processing programs (e.g. Athena or Larch).
For transmission mode, absorption coefficient of sample, ln(I0/I1), is mu01 column, and one for reference foil, ln(I1/I2), is mu12 column.
For fluorescence mode, absorption coefficient is ~flatot/I0.

Yes, both measurements can be done simultaneously.
If you request transmission only, and the transmission data is good enough, we will only collect transmission data.
Our new fluorescence detector(Vortex 7 elements) has a motion control to change the sample to detector distance.
The distance can be optimized for individual sample.

3/8"(OD) washer will fit this frame: nylon washers and PTFE washers are available from the links and other venders.
12 mm long, 1.5 - 2 mm OD capillary; 1/16", 5/64"

Yes, as long as your scan range of your samples are in one mono crystal, there is no problem to mix multiple elements in one sample holders.
Si(111) crystal covers 4.5 - 20 keV
Si(311) crystal covers 10 - 40 keV
Our scan macros has a built-in function to change detune and scan resolution depending on the scan energy range.
The autosampler and gripper work reproducibly to pick up sample holders back and forth.

The default macro for exafs scan includes 0.5 of exponential factor to increase acquisition time with higher k values.
You can specify the measurement parameters in the description section of sample information input web-form.

For known high concentration samples for transmission, 2-3 scan will be enough.
For low concentration samples, you need to collect and merge data to decide how many scans will be needed.
The samples will be measured minimum number of scans first; typically 3 scans
We will provide a link to download your data. The link will update for each scan.
You can analyze the data from your home institute and give us a feedback to add more scans for some samples.