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Institut Laue-Langevin

The Computing for Science (CS) group supports ILL scientists, students and visitors in a number of activities including data analysis, instrument simulation and sample simulation.

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All Software

Other Light Functionalities

1. Temperature control

Checks that temperature remains within specified limits. If temperature has

       gone outside limits for run options:[wait on T Error] minutes:
         A warning is generated
         A new counting is started. The numor is thus incremented, keeping other run
           parameters unchanged (temporary counting, with saving). These countings
           may be repeated as long as the temperature is not stabilised
         When temperature is recovered and stable, the remaining sequence time is
           rescaled, so that the total execution time, including lost time, still
           remains close to the original execution time.
       During temperature changes, the sequence suspends for [wait on Reach T]
       before starting to count.

2. Statistics control

All regions defined with the Regions of interest (ROIs) tool are analysed, computing the noise over signal ratio, and performing simple fits (line+gaussian and line+lorentzian, 6 parameters) on them. The normalised Chi-squared, and the estimated worse parameter uncertainty are computed. These three values give an indication about the overall statistics and if fit models give reasonable results.

When all regions applied on the cumulated data (sum of repeated countings for each run) are 'good enough' (below the run options:Rel Err. specified accuracy), and if the 'Count on Statistics' has been checked, then Light ends the current counting (to save measurement time), going to the next run definition in the sequence.

3. Detector/Sample Diagnosis control

 (not implemented yet, Nov 2002)

4. Alert control

All instrument control and monitoring processes may generate warning and error reports. These are mentioned into the Light Log, and raise a blinking Alert on the Light Main frame. This alert is removed when cliking on it.

5. Configuration files

Light has three types of configuration files, all with the same format.

    The user configuration file (e.g. Light.ini) contains user preferences for displays, general Light behaviour, current Run/Sequence definition.
    The instrument configuration file (e.g. Config.ini) contains preferences, displays and instrument setting parameters. It may only be read/saved by in SuperUser mode.
    The run/sequence file is a user configuration file with only the run/sequence information.

    These file format is as follow:

    • Comment lines start with the '#' '%' or ';' character
    • Other lines give the definition of fields in the 'Light' structure, e.g. sub-structures Displays, Global, Instrument, and a few other fields.
    • Most of the useful preferences are accessible from the Menu File:Preferences.
    • Other configuration values (instrument) are detailed in the Light technical help.

6. How Runs/Sequences are executed

Runs execution gathers a list of automatic checks and functions.

    Light checks that the instrument is ready to execute sequence (Idle). No other process (instrument setting, ...) should be running.
    The Temperature (as indicated on the Exp. Runs of the Main Frame), if positive, is set to the specified value.
    Light then waits for temperature stabilisation, as specified in the run options:[wait on Reach T]
    If the specified wavelength is different from the present instrument value, and this action is allowed (either in SuperUser mode, or unrestricted wavelength changes mode set from the instrument configuration file in the line Light.Instrument.ENERGYOPTIONS), then an Automatic wavelength change is performed (see below Automaitc Setup)
    Then the counting is started
    During the counting, the temperature is monitored, and if the 'Check T' flag is checked on the Exp. Runs section of the Main Frame, then the Temperature Control is executed permanently.
    Also, if the 'Count on Statistics' flag is check in the run options window, then the Statistics Control is executed.
    Then, if the 'Run Diagnosis' flag is check in the run options window, then the Detector/Sample Diagnosis control is executed.
    The counting is repeated as many times as specified in the 'Repetition' value of the Exp. Runs section of the Main Frame.
    The runs are executed in the order of the sequence definition, until an error occurs or the end of the sequence.

7. Automatic Setup

This procedure performs a fast automatic instrument setup.
 

  • The choppers are driven to their nominal speed and phase.
  • The monochromators are driven to their nominal position (as determined from rocking curves or instrument configuration file).
  • A check of the elastic peak position is done, and displayed.