Module Monitor

## VITESS Monitor Modules

The monitor modules are needed to obtain information about the wavelength, time, divergence or position (y-z-plane) dependent intensity or polarization distribution of the neutron output given from the previous modules. They write the intensity or average polarization according to the segmentation of the interval of interest as ASCII data to the monitor file. So the data of these file can be visualised by any graphics tool, e.g. 'Origin', or one can try to use the plot facilities of the VITESS GUI. The monitor module do not influence the neutron stream to the following modules, unless the option 'exclusive counts' is activated (see below).
There are different kinds of monitors:
- The modules mon1_a allow to plot intensity (n/s) as a function of the parameter 'a' in a 1D plot
they exist for time, wavelength, energy, hor. position (y), vert. position (z), hor. diverg. (div-y), vert. diverg. (div-z) and radial diverg. (div-y-z)
- The modules monpol_a allow to plot polarization as a function of the parameter 'a' in a 1D plot
they exist for time, wavelength, hor. position (y), vert. position (z), hor. diverg. (div-y) and vert. diverg. (div-z)
- The generic module monitor1D allows to plot intensity (n/s) or polarisation as a function of any parameter, including color, in a 1D plot.
- The modules mon2_ab allow to plot intensity (n/s) as a function of the parameter 'a' and 'b' in a 2D plot
they exist for the combinations (y - z), (div-y - div-z), (ky - kz), (TOF - wavelength), (wavelength - div-y/div-z), (y - div-y), (z - div-z), (radius - div-y-z)
- The modules monitorpol_pos allows to plot polarization as a function of hor. and vert. pos (x - y) in a 2D plot
- The generic module monitor2D allows to plot intensity or polarisation as a function of any combination of 2 parameters, including color, in a 2D plot
- The module mon_brilliance plots the brilliance (in n/(cm2sÅ sterad)) in a given time, position, wavelength and divergenz range in a 1D plot
The variable parameter can be: time, wavelength, y- or z-position, diy-y, div-z or div-y-z.

## VITESS Modules Mon1_x, Mon2_y, Monpol_z, Monitorpol_pos

#### For the specialized 1- or 2-dimensional monitors, the following information has to be given as input

monitor file name
number of bins
the interval to be considered (e.g. the wavelength range) will be partitioned into number of bins segments of equal size.
In the case of position, one can give a different number of bins for each direction of the y-z-plane for obtaining a rectangular segmentation.
colour only for 1-dim monitors
if colour is -1, the intensity of all trajectories is displayed
if colour is greater equal 0 only the trajectories of that colour are taken into account
normalise with binsize only for 1-dim monitors
if activated, in each channel count-rate and standard deviation are normalised with the binsize on the wavelength, time-of-flight, etc axis.
all files only for 1-dim monitors
if "yes" the intensity of all trajectories is displayed in the given monitor file and additionally files containing intensities of colour 0, 1, 2, ... 'colour' are written.
if "no", only one file containing trajectories of the given colour is generated
minimal value, maximal value
the values defining the interval of interest.
probability weight
if one deactivates the probability weight each neutron is considered with the weight 1, otherwise (default) the attributed probabilities (due to the operations of the modules before) are considered.
exclusive counts
if activated, only those neutrons which have been monitored successfully are transferred to the subsequent module (e.g. the wavelength of the neutron lies in the monitored wavelength interval and it is not taken our because of filters - see below)
filters like filter lambda, filter Y pos, begin and end of evaluation varying from monitor to monitor
only neutrons arriving in that time interval are considered in the evaluation
analysis direction only for monitoring polarization
in case of monitoring polarization distributions it is represented by a vector in cartesian coordinates
file format: only for 2-dim monitors
Choose between matrix style (VITESS format) and the 'xyz' representation readable by gnuplot and other analysis software.

## VITESS Modules Monitor1D and Monitor2D

The module monitor1D allows to plot any of the following parameters in a 1D plot. The module monitor2D allows to plot arbitrary combinations of following parameters against each other in a 2D plot:

position in the y-z plane: pos_y and pos_z

divergence in the y-z plane: div_y and div_z

wavelength

energy

time

wave vector in the y-z plane: k_y and k_z, defined as k_y(z) = (div_y(z) * 2 * pi) / lambda

position in the the cylindrical r-phi (corresponding to y-z) plane: r and phi

Color: This is useful if modules modified the color parameter. In particular, guides can change the color of a trajectory with each reflection. At the same time, the monitor1D and monitor2D modules can distinguish between reflections in the horizontal and vertical plane, if needed.

Moreover, two of the above parameters, in addition to the neutron wavelength, can be used as filters in order to restrict the parameter space shown in the plot. If desired, polarisation analysis can be applied, in which the average neutron spin component parallel to the analysis direction will be plotted in each bin of the diagram.

Additional input needed by the module:

Probability weight: if one deactivates the probability weight each neutron
is considered with the weight 1, otherwise (default) the attributed
probabilities (due to the operations of the modules before) are considered.

Exclusive counts: if activated, only those neutrons which have been monitored
successfully (both parameters under study lie within the considered value range and all filter conditions are fulfilled ) are transferred to the subsequent module.

analysis direction only for monitoring polarization in case of monitoring polarization distributions it is represented by a vector in cartesian coordinates

File format: Choose between matrix style (VITESS format) and the 'xyz' representation readable by gnuplot and other analysis software.

## VITESS Module Mon_brilliance

For continuous sources the brilliance calculated is always a time averaged brilliance. Therefore, time interval and frequency have to be left blank. If the time averaged brilliance shall be calculated for pulsed sources, they have to be left blank as well. Otherwise, the brilliance is calculated as the brilliance in the given time range and needs to be normalized by the frequency.
Depending on the existence of a reference file, the monitor file contains either the brilliance [n/(cm2 s sterad Å] or the brilliance transfer, i.e. the fraction of the brilliance that is transferred from source (or another reference point) to the position of the actual brilliance monitor. To get correct result, the brilliance monitors should be identical.
Average and peak brilliance - the maximal value found in the brilliance monitor file and the average value, i.e. the sum divided by the number of bins - are written to the log file.

monitor file
Name of the file containing the brilliance or the brilliance transfer (see below) as a function of the variable parameter
reference file
Name of the file containing the brilliance relative to which the brilliance transfer is calculated. 'Monitor file' contains the brilliance transfer in this case.
flux file
If a file name is given here, one line is written or added to this file, which contains the following numbers: mean wavelength (=center of the wavelength range), mean y-position and z-position, mean horizontal, vertical and radial divergence and average and peak brilliance (see above). This can be used calculate the brilliance as a function of a second parameter in running a series of simulation.
number of bins
the interval to be considered (e.g. the wavelength range) will be partitioned into number of bins segments of equal size.
In the case of position, one can give a different number of bins for each direction of the y-z-plane for obtaining a rectangular segmentation.
colour
if colour is -1, the intensity of all trajectories is displayed
if colour is greater or equal 0 only the trajectories of that colour are considered
variable parameter
the brilliance is monitored as a function of this parameter
ranges (min_lambda, max_lambda, .... up bound radial div)
neutrons are only monitored if their properties are within all given ranges
the parameter defined by 'var. parameter' is divided in 'number of bins channels
frequency
source frequency in case of a pulsed source (necessary to calculate from time averaged to actual brilliance

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Last modified: Mon Jun 30 17:24:23 MEST 2003 G. Zs.