Experiment-day guidelines

Quick file system overview

When data are aquired, they are first passed to the DAQ (Data AQuisition) systems. These data are multiplexed into five or six streams in order to allow the high-speed readoff. This can be seen in the _sXX_ part of XTC filenames (s for stream). These streams are written to the FFB filesystem located at /reg/d/ffb, which is a fast flash drive system to be used only while online. Files are first written as XXX.inprogress during data collection, then the extention is changed to XXX.xtc once data aquisition is complete. Do not attempt to process data which is in progress, since pyana will crash when it hits the end of the file.

Data are copied to psdm for offline processing, but this is not so fast. Therfore, when online, data should be read from the ffb filesystem, and written to the psdm system (/reg/d/psdm). When offline, read and write from psdm. Do not read from ffb when not at the beamline.

Programs worth having up online

• mov_viewer to view data streams as soon as they are collected. An example config file is in tutorial setup directory as test.cfg Prepatory Steps
• The logging window