Online (realtime) analysis

Online (realtime) analysis

So far, we discussed the offline analysis. Images become available for the analysis only after the run has completed. This imposes latency of more than 3 minutes (5150 images in a run at 30 Hz + processing time). For beam alignment and saturation monitoring, a realtime (online) pipeline has been developed. Here, we discuss how to use the online pipeline.

Starting the analysis server

The online version of Cheetah must be executed on the online analysis server, which is a dedicated node similar to fast feedback (FFB) nodes at LCLS.

First, connect to the online analysis server. This node is available from the beam line computers only (not from VPN).

ssh yourname@xu-bl3-anapc01

Go to /xnas/xufs06/yourname/ and make a folder for your experiment by copying a template. Note that /xnas is writable only from the online analysis server.

cd /xnas/xufs06/yourname/
cp -r /xnas/xufs06/sacla_sfx_app/template beamtime-2016A
cd beamtime-2016A

Edit the following line in the sacla-photon-online.ini to match the photon energy (eV) for your experiment.

defaultphotonenergyev=7000

Note that this line is used only by the online version of Cheetah. The offline version gets this information from the SyncDAQ DB, so you do not have to edit it.

Execute Cheetah and leave the terminal open.

sh run-cheetah.sh

(Press Ctrl-C to stop)

Starting the monitor

Open another terminal window in the beam line computer and connect to xhpcsmp-bl3 (or bl2 depending on your beam line).

ssh -Y [email protected]

Go to the online analysis directory and launch online-plotter.

cd /xnas/xufs06/yourname/beamtime-2016A
source ~sacla_sfx_app/setup.sh
online-plotter &

Red dots and blue dots indicate the number of spots and saturated spots in an image, respectively. The blue line indicates the hit rage (running average).