7.11. [ T-LET ] section

This tally can be used to obtain information on track length and dose as a function of the LET, \(dE/dx\), of a given material. This tally counts the energy losses of charged particles and nuclei; accordingly, the Event Generator mode, e-mode>=1, must be used to transport low-energy neutrons. Note that this tally does not consider the contributions of electrons or positrons below their cutoff energies, emin, in the result.

Table 7.11.1 mesh

value	explanation
reg, r-z, xyz	Mesh type. A mesh type subsection is required below this option.

Table 7.11.2 part

value	explanation
all (default), particle name	Tally particle.

Table 7.11.3 material

value	explanation
(optional)	Specify materials for scoring.
all	all is the default, same as no definition.
number of materials	To set number of materials, define the material numbers in the next line. The number of materials can be set as a negative value, in which case the specified materials are not included for scoring.
(next line)	2 5 8 Material numbers.

Table 7.11.4 letmat

value

explanation

(optional)

Material id for LET, \(dE/dx\). If not defined, a real material is assumed. If a material not used in the geometry is selected, its material density must be defined in [material]. To calculate LET in water, define water with 1 g/cm^3 in [material]. When letmat<0 is set, PHITS automatically calculates \(dE/dx\) for water with 1 g/cm^3 for electrons and positrons. Please see ParticleTherapy in the recommendation setting for more details.

Table 7.11.5 l-type

value	explanation
1, 2, 3, 4, 5	LET mesh. See Section 6.6.1 for mesh subsection format. Note that the LET spectrum may have unnatural peaks when a very fine mesh, for example 20 meshes per order of magnitude, is set.

Table 7.11.6 unit

value	explanation
1, 2, 3, 4, 5, 6	1: Track [cm/(keV/um)/source] 2: Dose [MeV/(keV/um)/source] 3: Track [cm/ln(keV/um)/source] 4: Dose [MeV/ln(keV/um)/source] 5: Track [cm/source] 6: Dose [MeV/source]
7, 8, 9, 10, 11, 12	7: Track [1/cm^2/(keV/um)/source] 8: Dose [MeV/cm^3/(keV/um)/source] 9: Track [1/cm^2/ln(keV/um)/source] 10: Dose [MeV/cm^3/ln(keV/um)/source] 11: Track [1/cm^2/source] 12: Dose [MeV/cm^3/source]
13, 14	13: \(L*f(L)\) [dimensionless], where \(\int f(L)dL=1\). 14: \(L*d(L)\) [keV/um], where \(\int d(L)dL=1\).

Table 7.11.7 axis

value	explanation
let, reg, x, y, z, r	x axis value of output data.
xy, yz, xz, rz	2-dimensional.

Table 7.11.8 samepage

value	explanation
(optional, D=part)	The type of data to be displayed on the same page of the image output file. Parameters that can be defined in axis can be specified.

Table 7.11.9 file

value	explanation
file name	Define output file names. This is required by each setting of axis.

Table 7.11.10 resfile

value	explanation
(optional, D=file)	Define a file name of the past tally in the restart calculation. Even if several axis parameters were defined, specify only one resfile.

Table 7.11.11 factor

value	explanation
(optional, D=1.0)	Normalization factor.

Table 7.11.12 title

value	explanation
(optional)	Title.

Table 7.11.13 angel

value	explanation
(optional)	ANGEL parameters.

Table 7.11.14 sangel

value	explanation
(optional)	Special format for ANGEL parameters.

Table 7.11.15 2d-type

value	explanation
1, 2, 3, 4, 5, 6, 7	Options for 2-dimensional plot.
(optional, D=3)

Table 7.11.16 gshow

value	explanation
0 (default), 1, 2, 3, 4, 5	When mesh=xyz and axis=xy,yz,xz, region border (1), material name (2), region name (3), and LAT number (4) are plotted using this option. gshow=5 outputs only material colors in pixel style when icntl=8.

Table 7.11.17 rshow

value	explanation
0 (default), 1, 2, 3	When mesh=reg,tet and axis=xy,yz,xz, region border (1), material name (2), and region name (3) are plotted using this option. A xyz mesh section must be added below this option.

Table 7.11.18 x-txt

value	explanation
(optional)	\(x\) axis title.

Table 7.11.19 y-txt

value	explanation
(optional)	\(y\) axis title.

Table 7.11.20 z-txt

value	explanation
(optional)	\(z\) axis title.

From version 3.02, new options, unit=13 and unit=14, were implemented. Using them, the frequency and dose probability densities of LET \(L\), \(f(L)\) and \(d(L)\), respectively, can be easily calculated. The results obtained from unit=13 and unit=14 are proportional to those obtained from unit=2 and unit=4, respectively, but their absolute values are different because the integral of the probability densities are normalized to 1 for the new options. In place of sum over, the frequency mean is output when unit=13, and the dose mean is output when unit=14, though their statistical errors are not calculated, always shown as 0.000. Note that unit=13 and unit=14 can be set only when axis=let.

Table 7.11.21 resol

value	explanation
1 (default)	This option multiplies the region line resolution by a factor of resol with the gshow or rshow option set to define the line thickness.

Table 7.11.22 width

value	explanation
0.5 (default)	The option defines the line thickness.

Table 7.11.23 volume

value	explanation
(optional)	This option defines the volume for each region for reg mesh. Volume definitions are required below this option. Values defined in [volume] are used in the case of no definition. If special description such as using (  ) is used to specify a region in reg=, its internally defined region number is output in input echo when this volume subsection is not defined.
reg vol	Volume definition. For details see the [volume] section.

Table 7.11.24 iechrl

value	explanation
72 (default)	Maximum number of columns for volume input echo.

Table 7.11.25 volmat

value	explanation
(optional, D=9)	This option corrects the volume value for each mesh when material is defined by the xyz mesh. 0 means no correction. Value of volmat is the number of scans per one xyz mesh side.

Table 7.11.26 epsout

value	explanation
0 (default), 1, 2	When epsout=1, results are plotted into eps files. The eps file is named by replacing the extension with .eps. When epsout=2, error bars are also displayed in the eps file, except for the 2-dimensional type, axis=xy, yz, xz, rz.

Table 7.11.27 maxangel

value	explanation
Number of part (default)	Specify the number of part shown in the eps file. This parameter limits the number of particles shown in a tally eps file, while it does not limit them in a numerical data file.

Table 7.11.28 ctmin(i)

value	explanation
(optional, D=-9999)	Minimum value for the i-th counter.

Table 7.11.29 ctmax(i)

value	explanation
(optional, D=9999)	Maximum value for the i-th counter.

Table 7.11.30 chmin(i)

value	explanation
(optional, D=-9999)	Minimum value for the i-th history-counter. This parameter cannot be specified in the batch variance mode, istdev=1.

Table 7.11.31 chmax(i)

value	explanation
(optional, D=9999)	Maximum value for the i-th history-counter. This parameter cannot be specified in the batch variance mode, istdev=1.

Table 7.11.32 trcl

value	explanation
(optional)	Coordinate transformation number or definition for r-z or xyz mesh.

Table 7.11.33 gslat

value	explanation
2 (default)	Option to draw lattice or tetrahedral geometry boundary lines when gshow or rshow is specified.
0	Not drawing.
1	Drawing. Note that the line of voxel phantoms may not be drawn clearly.
2	Not drawing the lines in the same cell.
3	Not drawing the lines in the same material. In this case, the boundary of two adjacent cells filled with the same material is not also drawn, even if not lattice or tetrahedral geometry. When gshow>=3, cell and lattice numbers are now shown.

Table 7.11.34 stdcut

value	explanation
(optional, D=-1)	Threshold value of STD cut off.

When specifying stdcut, PHITS automatically stop the calculation depending on values of STD, standard deviation. This function is available when stdcut is positive and itall=0,1 is set in [parameters] section. When all relative values of STD of the tally result are larger than 0 and smaller than stdcut at the last of one batch, the calculation is stopped. If stdcut in two or more tally sections is set, all the results of the tally sections have to satisfy the conditions in order for the function to work.