Live Data Testing¶

Introduction ¶

A video example of using multiple live streams and full direct elastic data reduction can be seen here.

The rest of this document describes some examples you can run yourself using a fake instrument which simulates the arrival of new data. For all of these tests you will need to change your Facility to TEST_LIVE, as described below. You can use MantidWorkbench.

Time required 20 - 30 minutes

Set up the test facility ¶

In MantidWorkbench:

Open the File menu and select Settings
Change the facility to TEST_LIVE

You can follow the same approach to set your facility back afterwards.

Starting a Fake Instrument ¶

ISIS Event ¶

Run the FakeISISEventDAE algorithm from the Algorithms toolbox
The following settings will create an instrument with 100 spectra, transmitting 2000 events every 20 milliseconds in 1 period. The data is between 10,000 and 20,000 microseconds TOF:
- NPeriods = 1
- NSpectra = 100
- Rate = 20
- NEvents = 2000
To stop the fake instrument, open the Algorithm Details window, by clicking on the Details button (MantidWorkbench) at the bottom of the Algorithms Toolbox. Then click Cancel next to FakeISISEventDAE.

Running this algorithm will produce “FakeISISEventDAE started” in the Messages panel, but will not make any other data appear yet.

ISIS Histogram ¶

Run the FakeISISHistoDAE Algorithm from the Algorithms toolbox
The following settings will create an instrument with 100 spectra, with 100 bins in 1 period:
- NPeriods = 1
- NSpectra = 100
- NBins = 100
To stop the fake instrument, open the Algorithm Details window, by clicking on the Details button at the bottom of the Algorithms Toolbox. Then click Cancel next to FakeISISHistoDAE.

Running this algorithm will produce “FakeISISHistoDAE started” in the Messages panel, but will not make any other data appear yet.

ADARA Fake Event ¶

This approach reads from an SNS pre-nexus file or an event-nexus file to recreate realistic event data, however It is a little more fiddly to setup.

Find the file Mantid.user.properties. Its location will be:
- Windows: C:\MantidInstall\bin
- Mac or linux: ~/.mantid (i.e. in a .mantid directory under your home directory)
To use a pre-nexus file, use the REF_L_32035_neutron_event.dat file (located in the TrainingCourseData folder), open the Mantid.user.properties file in your favorite text editor and add the following lines:
```
fileeventdatalistener.filename=REF_L_32035_neutron_event.dat
fileeventdatalistener.chunks=300
```
A event nexus file can also be used instead, for example:
```
fileeventdatalistener.filename=EQSANS_6071_event.nxs
```
For MantidWorkbench to find these files, they must be in a directory listed under “Data Search Directories” in the “Manage User Directories” menu. Chunking for files can be determined by using the DetermineChunking algorithm.
Start MantidWorkbench
Use the instrument ADARA_FileReader in the TEST_LIVE facility in the Settings dialog (MantidWorkbench). There is no need to stop this fake instrument.

The data from this file comprises almost 50,000 events across 77,824 histograms, with TOF values between 6,000 and 23,000 microseconds.

Starting a live data session ¶

Ensure that FakeISISHistoDAE and FakeISISEventDAE are running in the background to complete this example
To open the StartLiveData interface you can either
- Click the drop down Load button in the Workspaces toolbox and select Live Data
- Run the StartLiveData algorithm from the Algorithms toolbox

Live Event Data ¶

Setup: ISIS Event

Enter the following settings in the StartLiveData interface:

Instrument: ISIS_Event
Start Time: now
Update Every: 1 second
Processing: No Processing
Accumulation Method: Replace
Post Processing: No Processing
OutputWorkspace: live

Click “Run”.

You should see successive messages in MantidWorkbench of the form Loading live data chunk x at xx:xx:xx.

Live Histogram Data ¶

Setup : ISIS Histogram

Note that for Histogram data the accumulationMethod needs to be set to Replace, otherwise you will get a warning.

Enter the following settings in the StartLiveData interface:

Instrument: ISIS_Histogram
Start Time: now
Update Every: 1 second
Processing: No Processing
Accumulation Method: Replace
Post Processing: No Processing
OutputWorkspace: live

Click “Run”.

You should see successive messages in MantidWorkbench of the form Loading live data chunk x at xx:xx:xx.

Live event rebin using an algorithm ¶

Setup : ADARA Fake Event

Enter the following settings in the StartLiveData interface:

Instrument: ADARA_FakeEvent
Start Time: now
Update Every: 1 second
Processing: Algorthim
- Within the Processing step tab select the Rebin algorthm
- In the algorithm properties set Params to 40e3,1000,60e3
- PreserveEvents should be unticked
Accumulation Method: Add
OutputWorkspace: live

Click “Run”.

You should see successive messages in MantidWorkbench of the form Loading live data chunk x at xx:xx:xx.

Double-click on the live workspace, then select Plot All. You should see a histogram with two lines automatically updating as “new” data appears.

Live event pre- and post-processing ¶

This uses Rebin to select a region of time of flight, and then after the data is accumulated it uses SumSpectra to sum all of the data into a single spectrum. When using post processing you have to give the accumulation workspace a name.

Setup : ADARA Fake Event

Enter the following settings in the StartLiveData interface:

Instrument: ADARA_FakeEvent
Start Time: now
Update Every: 1 second
Processing: Algorithm
- Within the Processing step tab select the Rebin algorthm
- In the algorthim properties set Params to 40e3,500,60e3
- PreserveEvents should be unticked
Accumulation Method: Add
Post Processing: Algorithm
- Within the Post Processing step tab select the SumSpectra algorthm
- The options can be left as their defaults
AccumulationWorkspace: accumulation
OutputWorkspace: live

Click “Run”.

You should see successive messages in MantidWorkbench of the form Loading live data chunk x at xx:xx:xx.

Double-click on the live workspace. You should see a histogram with one line automatically updating as “new” data appears. Double-click on the accumulation workspace, then select Plot All. You should see a histogram with two lines automatically updating as “new” data appears.

Stopping a live data session ¶

A live data session will run until it is cancelled or Mantid is closed. To cancel a session:

To stop the live data session, open the Algorithm Details window, by clicking on the button at the bottom of the Algorithms Toolbox
Find the Algorithm “MonitorLiveData” and click the “Cancel” button next to it.