Rock'n Roll Trouble Shooting

Detlef-M. Smilgies, CHESS

Rock'n Roll refers to the semiautomatic line-up macros for lining-up samples for grazing incidence scattering and for calibrating the incident angle.
Rock'n Roll works in over 95% of all line-ups, but occasionally there can be a problem, either due to a non-ideal sample or an operator error.

Here is a trouble shooting list
  1. Check whether the shutter was open during the line-up scan; if not, redo line up with shutter open
    1. you can redo "rock" as many times as needed, but do not repeat "roll"
    2. if "roll does not work (only noise in the scans, no reflected beam), your sample may have poor x-ray reflectivity
    3. for poor reflectivity samples run rock a couple of times, and then set "samth" and "samz" to ZERO
  2. Check in the hutch whether something is blocking the beam
  3. Type "wsam" and compare user values and dial values for motors samz and samth.
    1. I carefully align the sample stage relative to the beam; these motor positions are saved as "dial" values
    2. if values differ by more than 10%, use the "set" command to set the motors to the dial values: set samz <dial value>;set samth <dial value>
    3. use the "mv" command to move motors to zero: mv samz 0; mv samth 0
  4. Make sure that you use a proper sample name containing only (A-Z, a-z, 0-9, -, _); otherwise an error results
    1. redo "new" with a proper sample name
  5. Make sure that you supply the correct sample thickness when using the "new" command
  6. Check that the shutter is open.
  7. Run the "rock" and "roll" macros again.
If this does not help
  1. Remove the sample and carefully line up the sample holder with "rock"; set "samz" and "samth" to ZERO
  2. Does the sample look flat? rough samples are always hard to align, best by hand