FAQ
- How to prepare samples?
- Detector type?
- Energy range?
- Acquisition time?
- How to open my data file?
- Materials Hazard Class Definitions
- Can fluorescence and transmission data be collected simultaneously?
- What is dimension of washer and capillary?
- There are multiple elements in my samples. Is it OK?
- My samples are air sensitive. Can I use my own sample holder?
- Can we use k-weighted count time during EXAFS data collection?
- How to choose number of scans?
- How to prepare samples?
- Data quality and acquisition time strongly depend on how to prepare samples.
- Sample thickness and uniformity are the key controlling parameters.
- Please find "Preparation of XAFS Samples" by Grant Bunker(IIT).
- Detector type?
- 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)
- Energy range?
- The 12-BM operates with Si(111) and Si(311) crystal pairs.
- Si(111) : 4.5 - 20 keV
- Si(311) : 20 - 40 keV
- Acquisition time?
- 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.
- How to open my data file?
- 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.
- Materials Hazard Class Definitions
- Can fluorescence and transmission data be collected simultaneously?
- 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.
- What is dimension of washer and capillary?
- There are multiple elements in my samples. Is it OK?
- 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.
- My samples are air sensitive. Can I use my own sample holder?
- Yes. if you need air tight container, you can use your own sample holder.
- You need to mount the sample to standard sample holder provided from us.
- Can we use k-weighted count time during EXAFS data collection?
- 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.
- How to choose number of scans?
- 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.