Welcome to CHESS <QM>2 Sample Alignment

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High Dynamic Range Reciprocal Space Mapping (HDRM)

Basic Theory - HDRM

High Dynamic Range Mapping (HDRM) is primarily a method for studying single crystal samples, although it can also be effective for studying thin films. HDRM aims is to rapidly study wide regions of reciprocal space, collecting the intense Bragg peaks required to refine crystal structures along with weak features associated with superstructures, and the slowly modulated scattering associated with phonons and short-range order[1].

Single Crytal Alignment

Basic steps for single crystal sample alignment - HDRM

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Step 1: Center the sample to the beam 
        FOURC> umvr samz 0.1 (relative motion of the sample movement up (+) and down (-)) 
        FOURC> umv phi 0
        FOURC> umv phi 180
        Move x and y to make the sample to the cursor
        FOURC> umv phi 90
        FOURC> umv phi 270
        Do it iteratively until the center of the axis match the sample position
Step 2 : Create file structure 
  a) Create newfile

        FOURC>newfile <samplename> 
        # samplename : chemical name of your sample, make sure you created folder in your directory


  b) Open HDRMscans.mac script and sort your path (sortmypathout)
        i) Change the _mysample = <sample_identifier> 
        # _mysample is the sample identifier
        # save the file

check the signals

Step 3: Run HDRMscans.mac script from terminal 
    FOURC> qdo ./HDRMscans.mac  
    # Notes: HDRMscans.mac contains all the script
Step 4 : If you want to check the best height for the sample (finding smaller sample best position) 
    FOURC>heightscan

    a) Data will save at 'tiff' folder inside the user folder at id4b
    b) Check the quality of the datasets at nexpy
    b) Go to the best position of the sample 
        FOURC> umv samz <position of the sample>
Step 5: Run three rotation crystal scan 
  It will rotate the crystal three times at different chi and theta angle

    FOURC> threextalscan 300 1

    #Notes: In the threextalscan 1st parameter is temperature 300K and the second parameter is waiting time 1 min
        - It will vary chi, theta and phi angle
        - Collect data phi 0-365 with 3650 images (1 degree/frame)
        - You can the change the exposure time (if needed)

    a) Data will save at raw6M in id4b folder

Quick video on data collection (make sure you read the above instructions before watching the video)

Step 6: Check data nexpy

Please look at the Data visualization - Nexpy section

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Temperature modify and collect data

Change temperature from 300K and 90 K- (if you are at Nitrogen atomosphere)
    FOURC> te 100
    # note: temperature here is 100 Kelvin

Make sure the temperature is stable before you run script

    FOURC> threextalscan 100 1

Practical guide of the temperature switch between nitrogen and helium

Click the link for details Nitrogen --> Helium and Helium --> Nitrogen

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Thin-film Alignment

Basic steps for single crystal thin-film sample alignment - HDRM. Detector height needs to change because of grazing incidence. Make sure you are able to see the samples (proper light arrangements)

Step 1: Center the sample to the beam 

  a) Move chi, phi, and theta positions to their initial setup
        FOURC> umv chi 90   
        FOURC> umv phi 0  
        FOURC> umv th 0

  b) Perform height adjustment
        Check the signal at the diode 
        FOURC> tw samz 0.01
        Move the sample in the Z-directions and cut the beam in half (for example: if the beam size is 300 microns, move 150 microns from the surface when the signal goes down)

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  c) Place cursor at center of the sample

              FOURC> umv phi 0
              FOURC> umv phi 180
              FOURC> umv phi 90
              FOURC> umv phi 270

Step 2 : Creating the file structure

  a) Create newfile

        FOURC>newfile samplename


  b) Open HDRMscans.mac script for thin-film
        Change the sample ID

Step 3: Run HDRMscans.mac script from terminal

      FOURC> qdo ./HDRMscans.mac 
      #Notes:HDRMscans.mac contains all the script

Step 3: Check the best height for the sample it will generate tiff file

    FOURC>powderscan 300 1

    a) Check the quality of the data sets at nexpy
    b) Go to the best position of the sample

Step 4: Run three rotation crystal scan 

    FOURC> threxstalscan 300 1 
    #Notes: Parameters: Temperature = 300, Sleep = 1

Step 5: Check data nexpy (please look at the Data visulization - Nexpy section )

Examples of Temperature Dependent Scans

300K- 475K at 25K temperature interval

Step 1: Follow the instruction of temprature switch 300K-500K and the temperature to stabilize

  def TScans_high_N2 '
  te = 325
  for (loopT=325; loopT<476; loopT=loopT+25){
  eval(sprintf("threextalscan %s 180",loopT))
  }

  '

90K- 300K at 25K temperature interval

  def Tscans_low_to_high_N2 '
  for (loopT=90; loopT < 301; loopT=loopT+15){
  eval(sprintf("threextalscan %s 180", loopT))
  }
  '

90K- 100K at 2K temperature interval, 100K-126K at 5K interval and 125K-200K at 25K interval

  def HighTScans_different_range '
  for (loopT=90; loopT < 101; loopT=loopT+2){
  eval(sprintf("threextalscan_longexposure %s 180", loopT))
  }

  for (loopT=100; loopT < 126; loopT=loopT+5){
  eval(sprintf("threextalscan_longexposure %s 180", loopT))
  }

  for (loopT=125; loopT < 200; loopT=loopT+25){
  eval(sprintf("threextalscan_longexposure %s 180", loopT))
  }

  '

15K- 90K at 15K temperature interval

  def scans_low_to_high_He '
  for (loopT=15; loopT < 91; loopT=loopT+15){
  eval(sprintf("threextalscan %s 180", loopT))
  }
  '