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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:

  1. Open the File menu and select Settings
  2. Change the facility to TEST_LIVE

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

Starting a Fake Instrument

ISIS Event

  1. Run the FakeISISEventDAE Algorithm from the Algorithms toolbox
  2. These 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
  3. 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.

ISIS Histogram

  1. Run the FakeISISHistoDAE Algorithm from the Algorithms toolbox
  2. These settings will create an instrument with 100 spectra, with 100 bins in 1 period:
    • NPeriods = 1
    • NSpectra = 100
    • NBins = 100
  3. 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.

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.

  1. 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)

  2. To use a pre-nexus file, use the REF_L_32035_neutron_event.dat file (located in the TrainingCourseData folder), open Mantid.user.properties 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

    Chunking for files can be determined by using the :ref:`DetermineChunking <algm-DetermineChunking>` algorithm.

  3. Start MantidWorkbench

  4. 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

  1. Ensure that FakeISISHistoDAE and FakeISISEventDAE are running in the background to complete this example
  2. 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 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

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: unticked
  • Accumulation Method: Add
  • OutputWorkspace: live

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: Not Ticked
  • Accumulation Method: Add
  • Post Processing: Algorithm
    • Within the Post Processing step tab select the SumSpectra algorthm
  • AccumulationWorkspace: accumulation
  • OutputWorkspace: live

Stopping a live data session

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

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