XRD, Bede D1

Prepared by:

Y. Qi and J. Scanlon

Location:

2219 Dow Building

Hazards:

The following materials and equipment associated with this procedure present exposure or physical health hazards. Safety precautions are prudent and mandatory.

This machine produces high intensity x-ray beams. Take all necessary precautions to avoid exposure to x-rays.



Controls:

Prior to performing this procedure, the following safety equipment must be accessible and ready for use: (e.g. chemical fume hood, biological safety cabinet, laminar flow hood, chemical spill kits)

None



Protective Equipment:

Prior to performing this procedure, the following personal protective equipment must be obtained and ready for use: (e.g. acid resistant gloves, safety eyewear, lab coat, chemical splash apron)

You must wear a radiation dosimeter when operating this equipment. The dosimeter will be checked every 3 months to determine whether you have received any x-ray exposure.



Waste Disposal:

This procedure will result in the follow regulated waste which must be disposed of in compliance with environmental regulations.

None



Spill:

In the event that a hazardous material spills during this procedure, be prepared to execute the emergency procedure below.

Not applicable


Instructions:


Contact Ying Qi or Justin Scanlon for training or any problems while operating the Bede D1. For booking go here. You will need an MSE user account. You also will need to have radiation safety training provided by OSEH and obtain Dosimeter Rings by filling out the form and returning it to Ying.   Please fill out the form in the attachments and bring the original copy when you come for your training. Fill out theuser section and have your advisor fill out the section provided. An account shortcode and account contact will be required as well. ALL TRAINING MUST BE GIVEN BY MSE TECH STAFF.


  1. General Information: Both the Red "Main Power" button on the front panel and the "Control Power" button found under the clear lid should be left on at all times. If they are turned of the system will drift out of alignment.
  2. Shutter controls:
    1. The only way to open the shutter on the Bede D1 is to push the yellow "Shutter Open" button on the front panel of the Bede. This will open the shutter. A red light next to the tube will come on when the shutter is open.
    2. To close the shutter, push the "Shutter Closed" button below the "Shutter Open" button.
    3. The system is interlocked such that if the shutter is open and you try to open the small sliding panel, the shutter will close. If the shutter is open and you try to lift up the main door to access the chamber more fully, the x-rays will turn off. So before you try to open the panel or lift up the main door, CLOSE THE SHUTTER! Remember that if you were able to go in with the shutter open, you would be in danger of getting direct beam or scattered radiation, which is very dangerous. The interlocks are there to protect you, and you will be banned permanently from the instrument if you are ever caught trying to bypass them! You will have to remember to open the shutter before running any scans or collecting any counts in the detector. If you forget, you will of course get a count rate of 0.
  3. Turning on the machine and preparing for alignment:
    1. Push the X-ray OFF button to show current settings for current and voltage.
    2. If not set as so, turn current to 5mA and voltage to –20kV while holding in the X-ray off button. This is the ideal start condition.
    3. Push the X-ray ON button.
    4. Increase the kV to -30 and mA to 20 .
    5. Open the enclosure and place the vertical slits located after the second crystal and before the third crystal into the holders on the smallest slit, and the horizontal slit at the second largest circle. Remove the sample holder.
    6. Visually make sure that the first and second crystals are in the high intensity or two bounce position (the slit in the crystal that is not parallel with the surface). Make sure that the third crystal is moved all the way out of the beam. These are all under computer control so do NOT move them manually!
    7. Close the enclosure door and open the shutter with the "shutter open" button.
  4. Aligning the detector and optics stage:
    1. Run a scan over 2theta. To do this enter the "Scan" menu and set up a scan with the following parameters: Axis - 2theta Units: degrees From: -5° to 5° Step size: 0.05 Speed: 0.5°/sec. Add this axis Scaler - EDR Fixed count at 0.1 Add this scaler "Go" "Run"
    2. Using "External Graph" note both the intensity and the location of the peak (either using "markers > data cursor" or "analysis > find peaks"). If the intensity is less than 200,000 counts the optics stage needs to be aligned, find Ying Qi before proceeding to step 3. If the intensity is greater than 200,000 proceed to step 9. Remember to push the "Reset Motors" button before exiting the data window!!!
    3. Remove all of the slits, both horizontal and vertical.
    4. Run a centered scan over Axis 1 with a range of 2000 sec.
    5. You will generate a scan with two peaks. These are the K alpha 1 (large) and K alpha 2 (small). Find the maximum position of the K alpha 1 peak and move Axis 1 to that position. Adjust Axis 1 a little bit in each direction to maximize the intensity. Calibrate to zero.
    6. Put the slits back in.
    7. Move Optics Z (in tens of microns) in each direction to find the maximum intensity. Calibrate to zero.
    8. Re-run the scan over 2theta. Note the intensity and the location of the peak.
    9. Move 2theta to the angle which has the highest intensity and calibrate this to zero by pushing "C" then entering zero and hitting OK.
  5. Aligning the position of the sample:
    1. Put in your sample.
    2. Adjust the Z axis (in tens of microns) so that the maximum intensity noted before is cut in half. If you have zero counts then your sample is completely blocking the beam and you need to move the sample towards the back of the machine. If you have the same intensity as before, your sample is not in the beam at all and you need to move it towards the front of the machine. (The Z axis movement is negative when moving towards the front of the machine.) Do this in the "Control" menu by choosing the Z axis and adjusting its position in microns forwards or backwards.
    3. Adjust the Omega axis in arc seconds so that any movement decreases the intensity. (that is, maximize the intensity by adjusting the omega axis).
    4. Cycle between the Z and Omega axes until you feel that the optimal intensity is achieved. Calibrate both of these axes to zero.
  6. Running a rocking curve (double axis) scan:
    1. Start with "turning on the machine and preparing for alignment".
    2. Increase the intensity to 40kV and 40 mA.
    3. Remove the slit that is before the detector. THIS IS CRITICAL BECAUSE WHEN MOVING TO THE BRAGG ANGLE THE ARM MAY RUN INTO THE SLIT!!! Make sure that the horizontal and vertical slits on the optics stage are in place.
    4. Move the Omega axis to the Bragg angle and the 2theta axis to twice the Bragg angle of your sample. NEVER RECALIBRATE THESE AXES TO ZERO!!!
    5. These values may not be precise. You will need to run a centered scan of the omega axis of approximately 3000 seconds. Move the omega axis to the maximum of the peak.
    6. Adjust the position of Omega and Chi to maximize the intensity and narrow the FWHM. You will need to iterate between the two. Another option is to use the "Optimize" menu. Set the scanning axis as Omega and the optimizing axis as Chi in tilt mode with step size of 0.05°. When you re run the omega scan from above, the peak obtained should have a FWHM (full width half maximum) of around 20-30 seconds.
    7. You are now ready to collect your rocking curve data. You will need to chose between the two types of scans:
      1. Theta rocking curve is used when the range of the scan is small and there is no fringe detail. No detector slits are used for this scan. Scan over the omega axis and collect data. The intensity of your peak should be around 80,000 or the system is not aligned properly.
      2. Theta/2theta rocking curve is used when the scan area is large and/or fringe detail exists. Place the narrowest slit in the detector slit holder. Re-optimize the 2theta axis so that a maximum intensity is detected. Run a scan over theta/2theta.
  7. Running a triple axis scan in preparation for reciprocal space mapping:
    1. Do all of the steps, starting from the top.
    2. Put in the smallest detector slit if not already in.
    3. Adjust 2theta to a maximum.
    4. Move the third crystal, Z3, into place (-53.64 mm from the hardware limit). This limits the amount of information entering the detector to a few arc seconds.
    5. Move Det Z by 4.5 mm to compensate for the third crystal placement.
    6. Adjust Axis 3 in arcseconds to achieve maximum intensity.
    7. Run a theta/2theta scan to find the range over which you should run the reciprocal space map in that direction. The intensity of the substrate peak should be around 10,000 counts, if it is not, the alignment needs to be perfected. If your scan has only the substrate peak and the film peak is missing you need to perfect the alignment of the system.
    8. Taking the number off of the theta/2theta scan, move the omega to the film peak. Run a scan over omega to determine the width of the film peak for the reciprocal space map. MAKE SURE THAT YOU MOVE OMEGA BACK TO THE SUBSTRATE PEAK AFTER THE SCAN!!
  8. Running a reciprocal space map:
    1. Do all of the steps for "running a triple axis scan".
    2. Set up the scan.
      1. Define the movement of the "Loop" axis (also called the offsetting axis). In this case, this is the Omega axis, which is going over the width of the film peak, in steps of 2 arc seconds and a speed of 500 arc sec/sec. Add this axis to the scan setup list.
      2. Setup the range and step-size for the scanning axis, in this case theta/2theta axis. Make sure that the parent axis of the theta/2theta scan is Omega. This is the range determined previously from the theta/2theta scan.
      3. Set up the setting for the scaler. Make sure that the parent axis of the scaler is the theta/2theta axis.
      4. Be sure to set "Auto-save" to yes!
  9. To shut down the system:
    1. Return all of the axes to the "zero" position for the next user.
    2. Close the shutter.
    3. Turn down and turn off the X-rays.
    4. Close the "BEDE Control" program.
    5. Take out your sample.

Equipment:


Last Revision:

Mar 11, 2014