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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

The Light windows

1. Main frame

The Main Frame is composed of three parts:

The Status and Integrated counts section (top)
 

This section displays the integrated counts at the Monitor and on the final Detector, as well as the Sample and Regulation temperatures. 
The Status of the ICS, as well as any Alert. indicating problems (warnings) or important errors.
In order to clear any raised Alert, just click on it. The Light log is then automatically displayed.
When in Simulation mode, the Status is indicated between brackets ([ status ]). The Control mode (active/simulation) is switched using the Menu Setup:Control Mode.

The Experiment Runs section (middle)
 

This section displays the current active Run, and enables edition/deletion/insertion of new runs. Each Run is a counting period at a given wavelength, for a given time or monitor preset, possibly repeated (a 0 value means ignore that run), and at a given temperature.
When starting a single run or a sequence, Light checks that the instrument is ready, sets the Temperature and wait until stabilisation (with time-out specified in Run Options). A negative temperature value will keep the current temperature.

During runs, depending on the activated options, Light may take care of the Temperature, finish the counting period prematurely if the specified statistic is achieved on defined ROIs, and look if some detectors are out of order, or even if the sample has changed/disappeared unexpectively (diagnosis).

Repeated runs are to be cumulated for data analysis. This enables to use part of these repetitions in case of problems occuring within one of the measurements (loss of the sample, electronics malfunction, ...)
Data is only saved when 'Save perm' is checked, else temporary saving is performed.


The Experiment Header section (bottom)
 

This section displays informations about the physicists and the current experiment/run.

2. Options for run

This window enables to customize the way runs and sequences are executed

[Temperature control]
   Checks that temperature remains within specified limits. If temperature has
   gone outside limits for [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.
   NOTE: the [wait on T Error] value should be higher than the [wait on Reach T] one

[Count on Statistics]
   basic statistics are performed for each defined ROI. This includes the computation
   of the noise/signal ratio, the normalised Chi squared corresponding to a fit
   using a single Gaussian peak over a background parabola, and an estimate of the 
   worse deduced relative uncertainty for this simple model (6 parameters). When all
   these values are better (lower) than the "Relative Error" parameter, it is
   assumed that a reasonable statistics has been achieved. Then, if the "Count on 
   Statistics" is active, the current counting is terminated, and goes-on with 
   the next run in the sequence.

[Optional Command]
   This line may contain a command to be executed when starting the run.
   It is sent to the Instrument by default, or usage may be specified with words
   "idl:", "system:", "mad:". Valid examples follow:
     idl: d=indgen(10) & plot, d
     system: ls ; nedit
     mad: par chop

3. preferences

This menu enables to change some internal settings controling the execution of Light
Verbosity=<level>
   affects the amount of messages displayed by Light.
   values can be: silent, normal, verbose, debug
IDL Echo=<0 or="" 1="">
   will display Light message in IDL promp window when true.
LogFile=<filename or empty>
   When non-empty, sets the name of the Light Log file, where messages are written.
IniFile=<filename>
   the name of the initialise file, that Light reads on start-up.
   it contains preferences and other stuff. e.g. Light.ini
ConfigDir=<dir>
   the directory where instrument configuration files are.
   e.g. /home/cs/lambda/CALIBRATION/<inst>/
ConfigFile=<filename>
   the name of the file containing instrument parameters.
   e.g. Config.ini
   ConfigDir and ConfigFile may only be changed in SuperUser mode
Simulation=<0 or="" 1="">
   sets the Instrument Control mode to "simulation" when true
   unactivate calls and commands to the instrument control program MAD
Append Runs=<0 or="" 1="">
   will append new loaded run file contents to the existing sequence if true
History size=<-2,0,3:100>
   sets the number of counts values to remember and plot in George
Frequency
   sets the update frequency of Light. A Major Update (all data displays) takes place every 10 updates.
Control Program
   sets the name of the program to control the instrument (usually 'mad')

4. Display Setting

This menu enables to change/modify the definition of variables to display in the Display panel.

Variable=[expression]
   defines the expression to be evaluated and displayed (Data)
   variables may be of type text (string array), scalar (single numerical values)
   numerical vector, and numerical image/map
   a single numerical value will be appended (catenate)
Type=<text|plot|surface|image|contour>
   defines the type of display to use
   default is to use a text, vector or surface display, depending on the Variable type
   but other displays may be chosen for images/maps, and it is also possible
   Empty type (or 'auto') determines automatically what's best.
Options=</log,/scatter,/histogram,/polar>
        </add,/overlay,/catenate,/unactivate,/exact,/no,/delete>
        <IX=[expr], IY=[expr], Name_IX="...", Name_IY="..." <br />         Comment="...", Auto_Load="...">
   sets some display options to use. 
   options that affect Data
      IX=[expr] sets the expression/variable to use as X axis values (for 1D/2D data sets)
      IY=[expr] sets the expression/variable to use as Y axis values (for 2D maps)
      Name_IX="..." sets the name of X axis (when IX is given)
      Name_IY="..." sets the name of Y axis (when IY is given)
      Name_Data="..." sets the name of the Data set (default is the Variable name)
      Auto_Load="..." sets the expression to be evaluated before each update
      Comment="..." sets a comment to appear on plot
   options that affect the way data is stored. Default is to replace data.
      /add: to add (sum-up) new data with the existing one
      /overlay: to display new data set on the same axis system
      /catenate: to append new data with previous one
      /unactivate: do not update/display data
      /delete: delete data set/display
      /no: remove the other options from data/plot options list
   options that affect the way the display appears
      /scatter: only plots symbols (default is line and symbols)
      /histogram: plots data as an histogram (steps)
      /polar: plots data in polar coordinates, when IX is given
      /detached: when a new plot will be created, it will appear as a separate window
      /exact: the [XYZ] axis will be tight around data

Know variables are e.g data, Monitor, Detectors, TOF, TSet, TSample, TReg, Power, as well as any Light variable e.g. the Mad structures t_res, t_nother, t_para...
 

Ex:
<tt>   Variable          Type    Options                                   comment</tt>
<tt>   memory(/current)                                                    (displays IDL memory usage with time)</tt>
<tt>   Mad.Temperature   surface Name_IX="Time", Name_IY="Temp", /catenate (record Temperatures vs time)</tt>
<tt>   Mad.Data,         image   Name_IX="Channels", Name_IX="TOF"         (displays all detectors)</tt>

5. Light Log

This window shows all operations performed by Light, depending on the verbosity level. This Log is saved automatically into the Light Log file (usually Light.log).

6. Regions of interest (ROIs)

This window enables to define regions of interest on the detector map, using some tools for drawing rectangles, circles, freehand drawing, polygons.
Regions may be moved and analysed.

These regions are typically elastic, quasi-elastic and inelastic peaks/features appearing on the detector image, and of particular interest.

All defined regions are used for the Regions of interest Analysis.

7. Regions of interest Analysis

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) 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 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.

This procedure is done in the background, and the Regions of interest Analysis window needs not to be opened, but is avilable for user information only.

8. SuperUser login

This window pops-up when you require to perform restricted operations, like changing instrument configuration (choppers, monochromators). Only Instrument Responsibles and Local Contact should activate this window.

To log out from the SU mode, just close the window (SU remains logged until then).

9. Analyse/Show sequence

This window is a summary of all the runs defined for execution of the experimental sequence.
it is updated at each run modification. A '<tt>*</tt>' pointer indicates which one is edited, and a '>' pointer indicates which one is runing (counting).

10. Experiment Header

This window enables to edit the experimental identification informations.

The proposal number is usually specified in the Experiment Title