5.2.23. About geometrical errors¶
Value |
Explanation |
(D=10)
|
Acceptable value against lost particle (per 1 PE).
|
Value |
Explanation |
(D=0)
|
Number of recoveries from region error.
|
Value |
Explanation |
(D=0)
|
Options for region check.
|
=0
|
No region check.
|
=1
|
Set the flight mesh to deltb after region-crossing, and check region.
|
Value |
Explanation |
(D=0)
|
Option for checking material numbers and densities of each cell when different densities are defined for a given material number in [cell] section.
|
=0
|
No check. In the above conditions for the [cell] section, incorrect drawing of the geometry by gshow option may occur. Note that this does not influence the results of the particle transport simulation.
|
=1
|
Check. The geometry by gshow option is correctly drawn, but it increases the loading time of complex geometry with a lot of cells.
|
Value |
Explanation |
(D=1.e-9) |
A tiny travel distance used to avoid particle splitting exactly on region boundaries. If lost particles occur frequently when utilizing the [importance] section, please set this value to a larger number. This distance is also used in the region check when igchk=1 . |
It is applied in the following cases:
The displacement step used for region checks when igchk=1.
The offset from boundaries for particles added by [importance] and [forced collision].
The initial displacement when a particle is generated exactly on a boundary in [source].
After a particle crosses the boundary of a region, the particle’s location is artificially moved a short distance away from the boundary surface along the forward direction in the PHITS code, and this short distance is defined as “flight mesh.” The purpose of the use of flight mesh is to more accurately determine which region the particle belongs to, for prevention of misjudments due to insufficient significant digits. This function is important in particular for large scale simulations that use curved surfaces.
Value |
Explanation |
(D=1)
|
Options for minimum flight mesh.
|
=0
|
Use values of deltm and deltc as flight mesh maxima.
|
=1
|
Maximum flight mesh is deltm and deltc divided by the density in the region. Note that deltc is not linked with this parameter when the density is less than 1.0 g/cm \(^3\) .
|
Value |
Explanation |
(D=20.12345)
|
Maximum flight mesh [cm]. This parameter is linked with idelt.
|
Value |
Explanation |
(D=2.012345)
|
Maximum flight mesh [cm] for charged particles (except for electrons and positrons) if their energy or angular straggling is considered (nedisp \(\ne0\) or nspred \(\ne0\) ). This parameter is linked with idelt when the material density is greater than 1.0 g/cm \(^3\) .
|
Value |
Explanation |
(D=0.101234)
|
The maximum step size of charged particles (except for electrons and positrons) before crossing a boundary when their angular straggling is considered (nspred \(\ne0\) ). Within this distance, the angular straggling is not considered. When describing a scattering process on thin films less than 1 cm, delt0 should be set to approximately \(1/10\) of its thickness.
|
Value |
Explanation |
(D=1.012345)
|
Maximum flight mesh [cm] in electric and magnetic fields for charged particles.
|
Value |
Explanation |
(D=1.0)
|
Maximum flight time [msec] in a time-dependent magnetic field.
|
Value |
Explanation |
(D=0.0001)
|
Automatic adjustment width for the minimum and maximum values of xyz-mesh in [weight window] and [t-wwg]. Note that the minimum value is shifted by \(-1*\) deltxyz and the maximum by \(+2*\) deltxyz.
|
From ver. 2.80, idelt=1 has become the default setting of PHITS, which sets the quotients of deltm and deltc divided by the region’s density (in units of g/cm \(^3\) ) as the flight mesh maxima. This setting is useful in for shortening the particle transport calculation time in air with a spatial scale over several hundred meters.