Standard Operating Procedure

for Measuring Texture

using the Bruker D8 with GADDS

Scott A Speakman, Ph.D.

Center for Materials Science and Engineering at MIT

Things to be careful of:

  • do not touch the face of the detector
  • use the protective plate when you are working inside the hutch
  • be gentle with the video, laser, and collimator
  • these are precisely aligned to give you good data
  • always check the shutter open/closed indicator
  • the software does not always correctly indicate whether the shutter is open or closed
  • watch for collisions
  • with so many moving parts, it is easy for you to drive one part into another

The tube operating power is 40 kV and 40 mA.

The tube standby power is 20 kV and 5 mA.

Do not turn the generator off- we want to always leave the instrument on.

Steps for Texture Measurements

1. Start GADDS

2. Create a new Project or open an existing Project

3. Check the Instrument Configuration

4. Mount and Align the sample

5. Turn the generator power up

6. Determine what angles you want to use to collect data

7. Collect a preliminary frame

8. Plan the pole figure measurement using Multex Area 2

9. Collect data in GADDS using MultiRun

1. Start GADDS

There are two versions of the GADDS software. Be sure to click on the right icon!

  • GADDS, which communicates with the diffractometer and is used for data collection and analysis
  • GADDS Off-Line, which does not communicate with the diffractometer and is used just for data analysis

When you start GADDS, it may ask if you want to set the generator power to 40 kV and 40 mA. Click No- do not turn up the generator power until after you have loaded your sample.

2. Create a new project or open an existing project

Projects are used to specify the folder where data will be saved and to set default values for the title during data collection.

To create a new project

  • Go to Project > New
  • To copy the currently loaded project, go to Project > Copy
  • The most important information to enter in the Options for Project dialog is the Working Directory
  • This is the folder where your data will be saved
  • The beginning of the pathname should always be C:\Frames\Data\
  • Then designate your personal folder and any subfolders that you want

To open an existing project

  • Go to Project > Load
  • Navigate to the folder where data for the project is saved
  • Select the gadds._nc file that is in that folder
  • Click OK

3. Check the Instrument Configuration

First, check the collimator and detector distance on the diffractometer. If these are not set properly, ask the SEF Staff to change them for you (or change them yourself if you have received the proper training).

Then, check that the software is properly configured for the detector setting that you want. This information is located in the lower right-hand corner of the GADDS software

Distance

The distance should reflect the actual physical distance of the detector from the sample. This can be determined by reading where the front edge of the detector is on the goniometer arm and adding 10.

  • A closer distance gives more intensity and collects more diffraction data simultaneously (captures a larger 2theta range and a larger gamma range).
  • A longer distance produces better angular resolution (ability to resolve peaks close to each other) and accuracy in peak positions.

Framesize

The framesize dictates how many pixels the detector will be divided into, and therefore affects the resolution of the data. A higher resolution can produce better peak shapes and angular resolution but will also produced larger files.

  • A 2048x2048 resolution produces 4 MB files.
  • This resolution is only required for data with closely spaced peaks or highly textured/epitaxial films.
  • A 1024x1024 resolution produces 1 MB files.
  • This resolution is adequate for most metals and high symmetry materials.
  • Remember, the typical pole figure will produce hundreds of files that you will need to analyze.

Floodfield and Spatial Correction Files

Finally, check the floodfield and spatial files being used and make sure the proper ones are loaded. The table below shows you the acceptable values for the Vantec2000 detector.

Distance / Framesize / Direct beam X / Direct beam Y / Floodfield / Spatial
19.95 / 2048x2048 / 1011.50 / 1022.50 / 2048_020 / 2048_020

If you need to change these values

  • Go to Edit > Congifure > User Settings
  • In the Options for Edit Configure User Settings dialog,
  • Focus on the values in the lower right-hand corner
  • Other values are not important
  • Select the desired Framesize from the drop-down menu
  • Specify the Sample to detector face distance.
  • Select a value from the table above
  • This value may be slightly different from the actual number that you read from the goniometer arm.
  • For example, if you set the physical detector to a position of 20 cm, our calibration of the instrument indicates that the actual distance is 19.95 cm and therefore this is the value that you should enter.
  • For the Framesize and Sample to detector face distance that you entered, read the appropriate Direct beam X and Direct beam Y from the table above. Enter these values.

4. Mount and Align the sample

  • Mount the Sample
  • If using an SEM stub, do not tighten the set screw
  • Drive the Goniometer to the proper Position
  • Go to Collect > Goniometer > Drive
  • In the Options for Collect Goniometer Drive, enter the values:
  • 2Theta = 70
  • Omega = 60
  • Chi = 90
  • Phi, X, Y, and Z = 0
  • Click OK
  • Put instrument in manual mode
  • Go to Collect > Goniometer > Manual
  • In the dialog box Options for Collect Goniometer Manual, click OK
  • Press L to turn on the Laser
  • Other commands available to you in manual mode are listed across the bottom of the GADDS window
  • !! Be Aware that pressing S will open the shutter!!
  • Start the Video Program
  • If using an SEM stub to mount the sample
  • Move the SEM stub in its holder until the laser is observed somewhere on the video screen.
  • Then tighten the set screw

  • Use the Remote Control Box to adjust X, Y, and Z
  • The remote control box allows you to manually move the goniometer
  • If the LCD screen on the remote control box reads “Bruker D8 with GADDS” and it will not let you select a motor to control, press SHIFT and then F1 on the remote control box.
  • Pressing different numbers on the remote control box will activate different motors for you to move. The numbers and their corresponding motor are:
  • 1: 2
  • 2: 
  • 3: 
  • 4: 
  • 5: x
  • 6: y
  • 7: z
  • Use the ↑↓ arrows to move the motors
  • Adjust Z until the laser is centered on the on the horizontal crosshair in the Video Screen
  • Press 7 to active the Z motor
  • If the laser is below the horizontal crosshair, use the ↑ arrow key to move Z up
  • If the laser is above the horizontal crosshair, use the ↓ arrow key to move Z down
  • The laser may be slightly off of the vertical line; this is ok
  • Optimize the position of the laser on your sample
  • Look at where the laser is hitting your sample
  • This is the portion of your sample that will be irradiated by the X-ray beam
  • Adjust X and Y until the laser is located where you would like to collect data from on your sample
  • A flat, smooth surface is best suited for XRD
  • After X and Y are adjusted, check if the laser is still centered on the horizontal crosshair in the Video screen
  • If necessary, readjust Z
  • If desired, you can save this image from the video camera; go to File > Save
  • Either quit the Video program or click on the red stop button to stop updating the video.
  • Refocus on GADDS (click somewhere on the GADDS window)
  • Press the ‘Esc’ key on the keyboard to exit Manual Mode

5. Turn the generator power up

  • Go to Collect > Goniometer > Generator
  • Set the tube power to 40 kV and 40 mA
  • Click OK

6. Determine what angles you want to use to collect data

To determine the best detector position for collecting data, you can either consult the Powder Diffraction File (PDF) database or you can collect a preliminary scan.

This section will describe collecting a preliminary scan, and then will explain how to choose the best detector positions to collect data with.

Collecting a Preliminary Scan

On thing to remember about using the GADDS detector: rather than collecting a continuous 1D scan like a conventional diffractometer, we usually use the 2D GADDS detector to take several snapshots of diffraction space- as if we were taking photos with a camera. We can then splice these snapshots together to form a full scan. Each snapshot is called a frame.

To collect a series of frames, we use the ‘SingleRun’ option. Despite the misleading name, the SingleRun can collect multiple frames of data.

  • Go to Collect > Scan >SingleRun

  • The fields in the Options for Collect Scan SingleRun are organized as:
  • Data Collection Options (the upper portion of the dialog window)
  • # Frames- how many frames of diffraction data will be collected
  • Seconds/Frame- how long detector will be exposed for each frames
  • you can enter this information as hh:mm:ss or as an integer value for seconds.
  • 2-Theta, Omega, Phi, Chi, X, Y, Z: starting positions for these values during the first frame
  • It is a good idea to make sure the X, Y, and Z properly reflect the aligned position for the sample that you determined in step 4
  • Scan Axis #-this iswhich position/motor will change between subsequent frames.
  • The value “Coupled” will change both 2Theta and Omega in a way consistent with Bragg-Brentano geometry
  • Frame width- how much the scan axis will change between each frame.
  • If the scan axis is 'Coupled', then this is value by which 2Theta will change (omega will change by 1/2 this value)
  • Mode- usually “Step”
  • Rotate Sample- whether or not the sample will rotate about Phi during data collection.
  • sample rotation is useful if the sample is highly textured or has large grains
  • Sample Osc-- what position(s), if any, will oscillate during sample collection.
  • useful for spreading the X-ray beam over a larger area of the sample to improve particle statistics for samples with a large grain size
  • Amplitude-- how much an axis will oscillate during data collection
  • Frame Header Information
  • Miscellaneous information that will be recorded in the data file for record-keeping purposes
  • You can use these fields in any manner that makes sense to you
  • Title is inherited from the Title in the project (step 1), but it can be changed
  • some people use title to indicate the overall research project, other people use it to indicate details specific to that data scan
  • Sample name is not inherited from the sample name that you entered when creating a project, but rather will be the value last entered by the previous user or last data file opened in GADDS
  • Filename generation
  • used to autogenerate the filename
  • Job Name-- this makes up the prefix of the filename
  • Run #-- this will be held constant during a SingleRun
  • Usually this is used to differentiate slightly different measurements from the same sample
  • Frame #-- this will change between different frames in the SingleRun measurement
  • Other options
  • Max Display-- the y axis maximum value during realtime display of data
  • Realtime display- check this option to show the diffraction data during the measurement
  • Capture video image- check this option to save the image from the video camera before each frame
  • Auto Z align- never check this option
  • Click OK to begin the data collection

The example shown in the image above will collect 5 frames. The first frame will be collected with the detector centered at 2-Theta= 30deg and Omega= 15deg. In between each subsequent scan, 2-Theta will change by 15deg and Omega will change by 7.5deg. Each of the 5 frames will be collected for 60 seconds, and the sample will be rotating about Phi while the frame is being collected.

This type of measurement will produce diffraction data from 17 to 103deg 2-Theta, which should show plenty of information for planning out the pole figure measurement.

Analyzing the Preliminary Scan

The last frame collected will be shown in GADDS when the measurement is finished.

To navigate through frames after data collection is finished:

  • Ctrl + Right Arrow keys will go to the next frame # for a given run #
  • Ctrl + Left Arrow keys will go to the previous frame # for a given run #

To load other data frames

  • Go to File > Display > Open or File > Load
  • You will have access to different options depending which one you use

File > Display > Open dialog

File > Load dialog

To Convert Data into a 1D Scan for Evaluating in Jade

In order to analyze 2D data, we usually need to convert the data into a 1D scan. We do this by integrating the data along Debye Rings into a single data point. Data can be converted using Chi Integration or Slices

To use Chi Integration

  • Open the first frame for a measurement run
  • Go to Peaks > Integrate > Chi
  • If you have established values for 2theta and chi that you want to use, input them here
  • Otherwise, we will graphically edit the 2theta and chi ranges in the next step, so don’t worry about changing these values
  • The typical options for Normalize Intensity are
  • 3- Normalize by solid angle
  • 5- Bin normalized
  • The best Step size depends on the framesize and detector distance.
  • For detector distance <20cm and framesize 1024, use .04
  • For detector distance >20cm and framesize 2048, use .02
  • Click OK
  • You can adjust the integration arc by pressing 1, 2, 3, or 4 on your keyboard and moving the mouse
  • Remember that 2theta goes from right to left for low to high value
  • 1 selects the starting 2theta (right edge)
  • 2 selects the ending 2theta (left edge)
  • 3 selects the starting chi (upper edge)
  • 4 selects the ending chi (lower edge)
  • Once the proper range is selected, left-click to integrate
  • In the Integrate Options dialog
  • Enter any value for Title and File name
  • Format should be DIFFRACplus for the Bruker binary format
  • Plotso is the Bruker Ascii format
  • Make sure that Append Y/N is checked
  • With this checked, every frame that you integrate that has the same file name will actually be written into the same file
  • ClickOK
  • Go to the next frame
  • Repeat the integration steps
  • When saving the result, make sure that you use the same File name as before and the Append Y/N is checked

Integration by Slice works almost the same way

  • Open the first frame for a measurement run
  • Data can be converted using Chi Integration or Slices
  • To use Chi Integration
  • Go to Peaks > Integrate > Slice
  • If you have established values for 2theta and chi that you want to use, input them here
  • The typical options for Normalize Intensity is 3
  • The best Step size depends on the framesize and detector distance.
  • For detector distance <20cm and framesize 1024, use .04
  • For detector distance >20cm and framesize 2048, use .02
  • Click OK
  • Adjust the slice range by clicking 1, 2, 3, and 4 on the keyboard and moving the mouse
  • Remember that 2theta goes from right to left for low to high value
  • 1 selects the starting 2theta (right edge)
  • 2 selects the ending 2theta (left edge)
  • 3 changes the angle of orientation of the slice
  • 4 changes the chi range for the slice
  • Once the proper range is selected, left-click to integrate
  • In the Integrate Options dialog
  • Enter any value for Title and File name
  • Format should be DIFFRACplus for the Bruker binary format
  • Plotso is the Bruker Ascii format
  • Make sure that Append Y/N is checked
  • With this checked, every frame that you integrate that has the same file name will actually be written into the same file
  • Click OK
  • Go to the next frame
  • Repeat the integration steps
  • When saving the result, make sure that you use the same File name as before and the Append Y/N is checked

Open the file in Jade

All of the integrated frames will be included in the same file when you open it in Jade.

The length of each segment in jade lets you know the range 2Theta you can collect in a single scan. In this case, it is about 28deg 2Theta.

Typical 2Theta ranges for detector distances are:

  • 28 deg 2Theta at a distance of 20 cm

Choose the best detector position for polefigure data collection

  • For a polefigure, you need to collect data for at least three peaks.
  • Best polefigures come from data with high angle 2theta, but you also want peaks with decent intensity
  • The more peaks you can capture in a single frame, the faster your data collection
  • Data collected in the center of the detector are more accurate
  • Data collected at the edges of the detector may be less accurate
  • Avoid using the extreme 2theta edges of the detector
  • Intensities collected in these frames will be affected by texture, which might make some peaks look weaker than they really are
  • Consult the PDF card to make sure that you are using peaks with good intensity

In the case above, centering the detector at 69 degrees will measure three peak simultaneously-- the peak at 55deg, the peak at 69deg, and the peak at 82deg. However, 55 and 82deg 2Theta would be at the edges of the detector and therefore less accurate. It will be better to use two detector positions to collect the data: