Compton DAQ HOWTO

CREX Main << HOW TOs

PREX II Version

This page is intended for PREX-II/CREX shift crew and instructs the correct usage of the compton DAQ, as well as some troubleshooting procedures.

Things to Check Before Running Compton

Check that the Compton laser table rates (look for ComptonUSbg and ComptonDSbg on the EPICS computer strip charts) are acceptable.

Values will be alarmed and will go off in case of quick spikes. If you don't know what the "acceptable" values are, then ask at the start of your shift.

Compton DAQ CODA

Annotated window of the compton CODA. Note that this picture if of a VNC that shifters don't need to use anymore. Simply running CODA and analysis from a terminal shell will be enough.

Opening CODA

• Log in to the compton machine with ssh -Y compton@compton (Credentials can be found in the usual place)
• If CODA is not open, then in the ssh terminal, and run kcoda (to be safe) and then startcoda
  • The Compton CODA looks almost exactly like the parity DAQ CODA with one extra window: the blue terminal window titled "ROC6." When you start up the Compton CODA if ROC6 keeps spitting out an error called udpSend: write failure then you've done it correctly.
• With the compton CODA opened in the VNC window, first click Platform -> Connect.
• Afterwards click "Configure."
  • The final line in the ROC6 window should be an error message saying callbackControl: Do not understand the command: session/control/setSession. If you see this error, then you've done it correctly.
• Then click "Download."
  • If you've done it correctly, then ER1, EB6, and ROC6 will all read "downloaded" as a state.
  • If ROC6 begins showing errors other than the ones mentioned above, then contact the RC immediately.

Starting and Stopping a Compton Run

• Once CODA is open, configured, and the ROCs downloaded to, simply click "Start" to start a compton run.
• Comment with the run configuration, and the current status of the beam.
• If possible have all compton runs last approximately 90 minutes. At 240 Hz that means once every three parity runs that you start, you should also start a new compton run.
• To stop a compton run, simply click "Stop."
• After stopping each run, follow the steps to analyze it below:

Analyzing Compton Data

The compton has a much simpler and faster analysis procedure than the parity DAQ. To analyze a compton run:

1. Open a new terminal window.
2. Enter command gocompton
3. Enter command ./online.sh -r <run_num> --webupload
   • The --webupload flag will automatically place plot PDFs in the hallaweb comptonPlots directory, but they won't appear on the webpage until the compton shifter later decides which group they're in.

That's it! If you see any errors that indicate replaying did not end successfully, then inform the compton expert on-call.

ROC6 Hard Reboot

The following instructions detail how to restart ROC6 if/when it dies during compton operation:

1. In either the vnc or on the compton machine open a Firefox window. Go to the page hareboot4.jlab.org or [follow this link].
2. Login with the correct hlauser credentials.
3. Go to outlet 8 and do "Immediate off."
4. Wait at least 30 seconds
5. Select "Immediate On" for outlet 8.
6. Check CODA to see if ROC6 is responding.

EXPERTS ONLY

1. Enter the command telnet hatsv5 2005 after selecting "Immediate On" to monitor ROC6 startup.
2. If you see the VXWorks logo in ascii-art pop up, startup is proceeding regularly.
3. Exit the environment with "Ctrl+]" and quit.

IOC hacp Reboot

Have the RC contact the compton laser expert on call. This reboot should be entirely expert-driven.

Troubleshooting Common Problems

A few common problems have occurred when running the compton and should have easy fixes. A few of them are:

CODA is saying something disconnected and is asking me if I want to reset.

• This is a common occurrence. Proceed with the reset. Re-configure and re-download when you're done. If CODA still doesn't behave after that, then run kcoda and startcoda (up to five times if necessary) to attempt to recover.

CODA hangs at the end of a run in a "Waiting for..." state indefinitely.

• Reset CODA if the option is available to you. If the reset works, try configuring and downloading again. If that doesn't work, or you cannot reset CODA, then simply run kcoda (multiple times if necessary) and then startcoda.

CODA says it can't communicate with ROC6.

• First attempt a reset. If that fails, click on the blue "ROC6" window. Press enter a few times. If a new line pops up, simply kcoda and startcoda again. If you cannot get a new line on that window then call the RC and instruct them to call Adam Zec and tell them that ROC6 needs a manual power cycle.

The VNC crashed on me!

• First, make sure you can still ssh into the compton computer. If yes, then it's likely just a network hiccup and you can start running again. If you can't, briefly walk over to the compton terminal (the one farthest from the door in the counting house back room) to make sure it's still running. If not, then contact the RC who should then contact a compton expert.