[ Identification | Description | Input parameters | Output parameters | Links ]

# The `Monitor_nD` Component

This component is a general Monitor that can output 0/1/2D signals (Intensity or signal vs. [something] and vs. [something] ...)

## Identification

- Author: Emmanuel Farhi
- Origin: ILL
- Date: 14th Feb 2000.
- Version: 1.31
- Modification history:
  - EF, 29th Feb 2000 : added more options, monitor shape, theta, phi
  - EF, 01st Feb 2001 : PreMonitor for correlation studies (0.13.6)
  - EF, 5th Apr 2001 : use global functions (0.14) compile faster
  - EF, 23th Jul 2001 : log of signal, init arrays to 0, box (0.15)
  - EF, 04th Sep 2001 : log/abs of variables (0.16)
  - EF, 24th Oct 2001 : capture flux [p*lambda/1.7985] (0.16.3)
  - EF, 27th Aug 2002 : monitor a variable in place of I (0.16.5)
  - EF, 25th Oct 2002 : banana, and auto for each variable (0.16.5)

## Description

    This component is a general Monitor that can output 0/1/2D signals
    It can produce many 1D signals (one for any variable specified in
    option list), or a single 2D output (two variables correlation).
    Also, an additional 'list' of neutron events can be produced.
    By default, monitor is square (in x/y plane). A disk shape is also possible
    The 'cylinder' and 'banana' option will change that for a banana shape
    The 'sphere' option simulates spherical detector. The 'box' is a box.
    The cylinder, sphere and banana should be centered on the scattering point.
    The monitored flux may be per monitor unit area, and weighted by
    a lambda/lambda(2200m/s) factor to obtain standard integrated capture flux.
    In normal configuration, the Monitor_nD measures the current parameters
    of the neutron that is beeing detected. But a PreMonitor_nD component can
    be used in order to study correlations between a neutron being detected in
    a Monitor_nD place, and given parameters that are monitored elsewhere
    (at PreMonitor_nD).
    The monitor can also act as a 3He gas detector, taking into account the
    detection efficiency.

    The 'bins' and 'limits' modifiers are to be used after each variable,
    and 'auto','log' and 'abs' come before it. (eg: auto abs log hdiv bins=10
    limits=[-5 5]) When placed after all variables,  these two latter modifiers
    apply to the signal (e.g. intensity). Unknown keywords are ignored.

    In the case of multiple components at the same position, the 'parallel'
    keyword must be used in each instance instead of defining a GROUP.

    Possible options are
    Variables to record:
        kx ky kz k wavevector [Angs-1] (    usually axis are
        vx vy vz v            [m/s]         x=horz., y=vert., z=on axis)
        x y z                 [m]      Distance, Position
        kxy vxy xy radius     [m]      Radial wavevector, velocity and position
        t time                [s]      Time of Flight
        energy omega          [meV]
        lambda wavelength     [Angs]
        p intensity flux      [n/s] or [n/cm^2/s]
        ncounts               [1]
        sx sy sz              [1]      Spin
        vdiv ydiv dy          [deg]    vertical divergence (y)
        hdiv divergence xdiv  [deg]    horizontal divergence (x)
        angle                 [deg]    divergence from  direction
        theta longitude       [deg]    longitude (x/z) [for sphere and cylinder]
        phi   lattitude       [deg]    lattitude (y/z) [for sphere and cylinder]

        user user1            will monitor the [Mon_Name]_Vars.UserVariable{1|2}
        user2                 to be assigned in an other component (see below)

    Other options keywords are:
        abs                       Will monitor the abs of the following variable
                                  or of the signal (if used after all variables)
        auto                      Automatically set detector limits for one/all
        all  {limits|bins|auto}   To set all limits or bins values or auto mode
        binary {float|double}     with 'source' option, saves in compact files
        bins=[bins=20]            Number of bins in the detector along dimension
        borders                   To also count off-limits neutrons
                                   (X < min or X > max)
        capture                   weight by lambda/lambda(2200m/s) capture flux
        exclusive                 absorb neutrons out of monitor limits
        file=string               Detector image file name. default is component
                                   name, plus date and variable extension.
        incoming                  Monitor incoming beam in non flat det
        intermediate=[5 in %]     Save ALL results every n% steps in simulation
        limits=[min max]          Lower/Upper limits for axes
                                   (see up for the variable unit)
        list=[counts=1000] or all For a long file of neutron characteristics
                                   with [counts] or all events
        log                       Will monitor the log of the following variable
                                  or of the signal (if used after all variables)
        min=[min_value]           Same as limits, but only sets the min or max
        max=[max_value]
        multiple                  Create multiple independant 1D monitors files
        no or not                 Revert next option
        outgoing                  Monitor outgoing beam (default)
        parallel                  Use this option when the next component is at
                                   the same position (parallel components)
        per cm2                   Intensity will be per cm^2
        premonitor                Will monitor neutron parameters stored
                                   previously with PreMonitor_nD.
        signal=[var]              Will monitor [var] instead of usual intensity
        slit or absorb            Absorb neutrons that are out detector
        source                    The monitor will save neutron states
        unactivate                To unactivate detector (0D detector)
        verbose                   To display additional informations
        3He_pressure=[3 in bars]  The 3He gas pressure in detector.
                                  3He_pressure=0 is perfect detector (default)

    Detector shape options (specified as xwidth,yheight,zthick or x/y/z/min/max)
        box                       Box of size xwidth, yheight, zthick
        cylinder                  To get a cylindrical monitor
                                   (diameter is xwidth, height is yheight).
        banana                    Same as cylinder, without top/bottom,
                                   on restricted angular area; use theta
                                   variable with limits to define arc.
                                   (diameter is xwidth, height is yheight).
        disk                      Disk flat xy monitor. radius is xwidth.
        sphere                    To get a spherical monitor (e.g. a 4PI)
                                   (diameter is xwidth).
        square                    Square flat xy monitor (xwidth, yheight)

    EXAMPLES:
    MyMon = Monitor_nD(
      xwidth = 0.1, yheight = 0.1, zthick = 0,
      options = "intensity per cm2 angle,limits=[-5 5] bins=10,with
                 borders, file = mon1");
                     will monitor neutron angle from [z] axis, between -5
                     and 5 degrees, in 10 bins, into "mon1.A" output 1D file
      options = "sphere theta phi outgoing"  for a sphere PSD detector (out
                     beam)  and saves into file "MyMon_[Date_ID].th_ph"
      options = "banana, theta limits=[10,130], bins=120, y" a theta/height
             banana detector
      options = "angle radius all auto"   is a 2D monitor with automatic limits
      options = "list=1000 kx ky kz energy" records 1000 neutron event in a file
      options = "multiple kx ky kz, auto abs log t, and list all neutrons"
           makes 4 output 1D files and produces a complete list for all neutrons
           and monitor log(abs(tof)) within automatic limits (for t)

    How to monitor any instrument/component variable into a Monitor_nD
    Suppose the Monitor_nD instance is named 'MyMonitor'.
    1) put in your instrument DECLARE:
         %include "monitor_nd-lib"
         MONND_DECLARE(MyMonitor); // will monitor custom things in MyMonitor
    2) put in your instrument INITIALIZE (optional, to set monitor name):
         MONND_USER_TITLE(MyMonitor, 1, "Log(age of the Captain)");
       This will set 'user1' title (because of the '1', could be '2' as well).
    3) put just after the component where you want to monitor (to set the value)
         EXTEND
         %{ // attach a value to user1 in MyMonitor
           MONND_USER_VALUE(MyMonitor, 1, log(fabs(x*y+1)));
         %}
      This will set 'user1' (because of the '1', could be '2' as well) value.
      The value to store in user1 may be obtained from local component variables
      (this requires to look into the comp code, to extract a variable name)
      or neutron coordinates or any instrument variable, or any other component
      variable (using MC_GETPAR).
    4) put further in the instrument (to monitor the user1 value defined before)
         COMPONENT MyMonitor = Monitor_nD(
          xwidth = 0.1, yheight = 0.1,
          options="user1, auto")
         AT ...

    See also the example in PreMonitor_nD to
    monitor neutron parameters cross-correlations.

## Input parameters

Parameters in boldface are required; the others are optional.

Name | Unit | Description | Default
--- | --- | --- | ---
options | str | String that specifies the configuration of the monitor The general syntax is "[x] options..." (see Descr.). | 0
filename | str | Output file name (overrides file=XX option). | 0
xwidth | m | Width/diameter of detector (x). Default is 10 cm. | 0.1
yheight | m | Height of detector (y). Default is 10 cm. | 0.1
zthick | m | Thichness of detector (z). | 0
xmin | m | Lower x bound of opening | 0
xmax | m | Upper x bound of opening | 0
ymin | m | Lower y bound of opening | 0
ymax | m | Upper y bound of opening | 0
zmin | m | Lower z bound of opening | 0
zmax | m | Upper z bound of opening | 0
bins | 1 | Number of bins to force for all variables. Use 'bins' keyword in 'options' for heterogeneous bins | 0
min | u | Minimum range value to force for all variables Use 'min' or 'limits' keyword in 'options' for other limits | -1e40
max | u | Maximum range value to force for all variables Use 'max' or 'limits' keyword in 'options' for other limits | 1e40

## Output parameters

Name | Unit | Description | Default
--- | --- | --- | ---
DEFS | struct | structure containing Monitor_nD Defines |
Vars | struct | structure containing Monitor_nD variables |

## Links

- Source code for `Monitor_nD.comp`.
- McStas at ILL
- PreMonitor_nD

[ Identification | Description | Input parameters | Output parameters | Links ]