Input File
The input file IN.DAT is used to change the values of the physics, engineering
and other code parameters from their default values, and to set up the constraint equations,
iteration variables etc.
If the code encounters a problem reading the input file, it will stop immediately
with an error message. The last line of the output file OUT.DAT may give an
indication of where in the input file the problem lies.
File Naming Convention
The default PROCESS input file name is IN.DAT. The user can provide a named
input file, that will produce named output files, provided the last 6 characters
of the input file name are IN.DAT.
process -i [path-to-file]/my_file_name_IN.DAT
Will produce output files named:
my_file_name_OUT.DATmy_file_name_MFILE.DAT
If no input file name is given as the first argument to the code, it assumes an
IN.DAT file is present in the current directory.
Constraints
PROCESS permits a large number of constraint equations, all of which are formulated
in the source file constraint equations.f90.
In the input file constraint equations are specified as in the following example:
icc = 2
where icc is the constraints array in PROCESS and the user is requesting constraint
equation 2. A comment on the same line is recommended:
icc = 2 * Global power balance (consistency equation)
Some constraints have f-value variables. These must be set as iteration variables,
which are discussed below.
Constraints
A full list of constraints is given on the variable description page in the row labelled
lablcc here.
See solver page for more info
Iteration Variables
Variables that are adjusted by PROCESS in order to satisfy the constraints and optimise the figure of merit are referred to as iteration variables. Successive calls are made to the physics and engineering routines, with slightly different values for the iteration variables on each call, and the equation solver determines the effect on the output due to these small changes to the input.
Iteration variables must never be initialised to zero. The code will not be able to adjust the variable’s value if this is done, and it will stop with an error message.
An iteration variable can be specified in the input file as in the following example:
ixc = 3
where ixc is the iteration variable array in PROCESS. An in-line comment is recommended:
ixc = 3 * Plasma major radius [m]
For example, the major radius is available as an iteration variable, and appears in the variable
description file as rmajor /8.14/ : plasma major radius (m) (iteration variable 3). If it
is selected as an iteration variable, it will be adjusted by the code. The value input by the user (or
the default, if no value is specified), will be used as the starting value.
Iteration Variables
A full list of iteration variables is given on the variable description page in the row labelled
lablxc here.
(See solver page for more info)
Bounds
The upper and lower bounds of an iteration variable can be set by the user in
the input file as in the following example,
where boundl is the lower bound and boundu is the upper bound:
boundl(3) = 8
boundu(3) = 12
where 3 is the iteration variable number (in this case the major radius). It is good practice to
place the iteration variable and its bounds in a block:
ixc = 3 * Plasma major radius [m]
boundl(3) = 8
boundu(3) = 12
Numerics
The user can select which solver to use, but only one solver is available at present (VMCON).
ioptimz = 1 * for optimisation VMCON only
The user can select the figure of merit to be used:
minmax = 1 * Switch for figure-of-merit (see lablmm for descriptions)
In this case the user is choosing option 1, which is major radius. For minmax
- a positive value means minimise the figure of merit
- a negative value means maximise the figure of merit
The user can also input the allowed error tolerance on the solver solution:
epsvmc = 1.0e-8 * Error tolerance for vmcon
Figure of Merit
A full list of figures of merit is given on the variable description page in the row labelled
lablmm here.
Input Variables
One can enter an input into the IN.DAT by:
rmajor = 8.90 * Plasma major radius [m]
The * is for adding comments to the input file. To comment out an entire line
one can add a * to the beginning of the line, as below:
*rmajor = 8.90 * Plasma major radius [m]
Variable Descriptions
A full list of inputs variables is given in the PROCESS html documentation
file vardes.html and on the variable description page here.
Scan
PROCESS can scan either one or two variables within a single run.
This provides a method of determining the sensitivity of the
results to different input assumptions.
1-D scan. The user specifies which variable is to be scanned as in the following example:
nsweep = 1
isweep = 4
sweep = 2.8, 2.9, 3.0, 3.1
where nsweep is the scan variable chosen (see variable descriptions),
isweep is the number of scan points and sweep is the array of scan values. In this example,
PROCESS runs for each of the four values given of the plasma aspect ratio variable aspect.
2-D scan. Two variables are scanned over a rectangular grid of values,
using the switch scan_dim = 2 as below
scan_dim = 2
nweep = 1
isweep = 4
sweep = 2.8, 2.9, 3.0, 3.1
nweep_2 = 4
isweep_2 = 3
sweep_2 = 1.0, 1.1, 1.2
where the scan parameters have duplicate names with _2 for the second scan
dimension. In this example, PROCESS runs for each of the four values given
of the plasma aspect ratio variable aspect (specified by nsweep=1) and the three values given for
the energy confinement time enhancement factor hfact (specified by nsweep_2=4).
The results from the previous scan point are used as the input to the next scan point. The output files contain all of the scan points for a given run.
Scan variables should not be confused with iteration variables.
Scanning
For obvious reasons, the active scanning variable or variables must not also be active
iteration variables.
A full list of scan variables is here.
Examples
Example IN.DAT files are available in the repository in the folder /tests/regression/input_files/.