HOWTO Take a new FDC Flatness Scan

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To perform a new flatness measurement, do the following:

  1. Make sure the driver box, VME crate, and Linux Desktop computer are all on
  2. Verify that the laser is mounted in the proper set of mounting holes. If scanning a cathode plane, the mounting screws should be in the middle set of holes. If scanning the granite rock, the mounting screws should be in the holes closest to the granite surface. Make sure the cable for the laser is routed through the restraint to keep the cable from brushing against the cathode during the scan.
  3. Mount the plane to be scanned and make sure all mounting screws are tight.
  4. Make sure the laser is plugged in. The cable is marked and should be plugged into the power strip that sits on top of the granite block.
  5. Open a terminal on the Linux Desktop and type MeasureFlatness and hit return. Alternatively you may either click on Applications→Laser_Control→MeasureFlatness or double click on the MeasureFlatness icon in the Laser_Control folder on the desktop (choose "run in terminal" if prompted).
  6. Type in the 3 digit plane number at the prompt and hit return. If scanning the granite rock, use "999" for the plane number. (Note: The number must be a positive, 3-digit integer with leading zeros if needed)
  7. Type in the 3 digit plane orientation (angle) at the prompt. This needs to be a whole number without a decimal point. Round up if needed. (Note it must be 3 digits, use leading zeros if needed.)
  8. The laser should begin moving to the "Home" position and begin the scan shortly thereafter. It should take between 10 and 15 minutes to complete the scan and run the macros.
  9. The results of the scan, both raw data files and plots produced by ROOT macros, will be placed in the /home/laser/FLATNESS/flatness_data and /home/laser/FLATNESS/flatness_data/images/XXX directories respectively where XXX is a unique name for the scan including the plane id, angle, and timestamp. Note that this computer can be accessed remotely via ssh or scp with the username and password that are posted in EEL126, or by copying the data files to a USB drive.
  10. When you are finished doing scans, be sure to unplug the laser and power down the stepper driver box (switch is on the back left side when facing the box from the front).

Troubleshooting

  • If you need to stop a currently executing motion immediately then you can do one of the following:
    1. Turn off power to the driver box to immediately stop motion in both directions.
    2. You can activate the limit switch by hand to stop motion in a given direction. Only do this if the laser is far from the switch you're activating to avoid getting your finger pinched.
  • If you need to stop a scan or have performed one of the above actions to interrupt the motion of the laser, then just hit Ctl-C in the terminal in which MeasureFlatness was typed. You may need to kill the telnet session before starting a new scan by entering killall -9 telnet in a terminal.
  • If there are problems of any sort with either logging in to the VME crate or getting any response from the motors, try power cycling the driver and VME crate first. It may also be that you need to kill the telnet session by entering killall -9 telnet in a terminal. If there are still problems, try rebooting the computer.
  • If the laser head sits motionless for a long time after a horizontal move, it is likely because another program has control of the serial port. Try killing the other process with the following:
    kill -9 `cat /var/lock/LCK..ttyS0`
    If this doesn't work, you may need to reboot the computer.

Contact

Please refer any questions to David Lawrence davidl@jlab.org x5567


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