Live Data User Interface¶

How to Start a live data stream¶

To start a live data stream into Mantid you need to use the StartLiveData v1 algorithm. You can do this the same way as any other algorithm using the Algorithms toolbox, or you can select the Live Data option under the Load button.

Start Live Data¶

The start live data interface can seem quite daunting at first, but it is easy to do setup simple data streams quite easily, the next section will take you through several examples.

For now I’ll just introduce a few of the more common properties.

Starting Time

This allows you to set when you want the stream to start at facilities that support this. If your facility does not support variable start times then the stream will start from “now”.

Update Every

Here you set the delay between each “chunk” of data being read. The optimal value depends on the amount of processing you are doing, but I suggest you start with something like 3 seconds.

Processing

Here you select what processing you want to do to each live data chunk on it’s way to the accumulation workspace. If you choose algorithm or script the Processing step pane on the right will change to allow you to define the processing.

Preserve Events

This only applies to event based live data streams. If you tick preserve events the data will be maintained as events through to the accumulation workspace, this allows more flexibility for filtering and rebinning later, but will lead to large amounts or data accumulating in memory over time, eventually the system can run out of memory and the live data stream would stop.

Accumulation Method

Here you can choose how the data is “added” into the accumulation workspace. In most cases for event based data the correct option is “Add”, and for Histogram based data it is “Replace”. There is also an “append” option which will append spectra to the output workspace, increasing its size.

Post Processing

Here you select what post processing you want to do to the entire data in the accumulation workspace each time a new chunk is “added”. If you choose algorithm or script the Post Processing step pane on the right will change to allow you to define the processing.

At End of Run

At facilities that support this you can define what you want Mantid to do when one run is ended and another started.

Accumulation Workspace

This is the name that will be used for the accumulation workspace. If no post-processing is selected this is greyed out as it is not needed.

Output Workspace

The name of the output workspace containing the results you are after.

How to Stop a live data stream¶

Once you start a live data stream it creates a background algorithm called MonitorLiveData which keeps the process running. This means it will continue until one of the following happens:

1. MantidPlot (or Mantid if using through command line python) is closed.
2. You manually cancel the MonitorLiveData algorithm using the process below.
3. The run ends (although the process may continue if you set the live data stream to continue on run end).

To manually stop the live data stream you need to:

1. Bring up the running algorithm details using the “Details” button at the bottom of the algorithms toolbox (next to the progress bar).
2. Click the cancel button next to the MonitorLiveData algorithm you wish to stop.
3. If you have more than one, clicking the arrow next to the algorithm name will list all of the properties to help you select the right one to cancel.