5.3.21. Definition of time distribution¶
By specifying a time-distribution subsection starting with t-type =, the source can have a time distribution. t-type = 1, 2 correspond to rectangular and Gaussian distributions, respectively. t-type = 3, 4 define a time distribution by boundary points and intensity distribution. t-type = 5, 6 define a time-dependent intensity distribution by an arbitrary function. In addition, t-type = 100 can specify the type of time distribution as a function of energy. Items with (D=***) are omissible.
5.3.21.1. t-type = 0, 1, 2¶
Time distribution, D = 0. 0: No time distribution. t = 0.0. 1: Rectangular distribution. 2: Gaussian distribution.
t0 =: Center time of the first time distribution [ns], D = 0.0.
tw =: Width of the time distribution [ns]. For the rectangular distribution, this is the full width. For the Gaussian distribution, this is the full width at half maximum.
tn =: Number of time distributions.
td =: Interval between time distributions [ns].
tc =: Cutoff time [ns] for the Gaussian distribution, D = \(10 \times tw\).
5.3.21.2. t-type = 3¶
An arbitrary time distribution is specified by giving time boundary points t(i) and the integrated values w(i) of the source particle generation probability in each bin. The time distribution is represented by statistically adjusting the number of particles generated in each bin so that it is proportional to w(i).
ntt =: Number of time groups. Data are given in free format as follows.
(t(i), w(i), i = 1, ntt), t(ntt+1)
The integrated number of particles generated in each bin is proportional to w(i).
5.3.21.3. t-type = 4¶
The same time distribution as t-type = 3 is generated. However, whereas t-type = 3 represents the time distribution by adjusting the number of generated particles, t-type = 4 represents it by generating the same number of particles in all time bins and changing the integrated particle weight in proportion to w(i). In addition, by setting o-type = 1 and giving the generation-number ratio o(i), the number of generated particles in each bin can be changed to modify the statistics of a source at a specific time.
ntt =: Number of time groups. Data are given in free format as follows.
(t(i), w(i), i = 1, ntt), t(ntt+1)
By default, o-type = 0, the same number of particles is generated in each bin. When o-type = 1 and o(i) is specified, the integrated number of generated particles in each bin is proportional to those values.
o-type = 0, 1: Generation-number option, D = 0.
For 0, o(i)=1 in all bins, and there is no following data.
For 1, the generation-number ratio o(i) in each bin is given in the following line.
(o(i), i = 1, ntt)
5.3.21.4. t-type = 5¶
A differential time spectrum, \(d\varphi/dt\), is given by an arbitrary function \(h(t)\).
h(x): A function written in Fortran format. Here, x represents time [ns]. Internal variables and constants can be used.
ll: Number of time groups.
tg1: Lower cutoff value of the time distribution [ns].
tg2: Upper cutoff value of the time distribution [ns].
5.3.21.5. t-type = 6¶
The same time distribution as t-type = 5 is generated. However, whereas t-type = 5 represents the time distribution by adjusting the number of generated particles, t-type = 6 represents it by generating the same number of particles in all time bins and changing the integrated particle weight in proportion to w(i). In addition, by setting o-type = 1 and giving the generation-number ratio o(i), the number of generated particles in each bin can be changed to modify the statistics of a source at a specific time.
h(x): A function written in Fortran format. Here, x represents time [ns]. Internal variables and constants can be used.
ll: Number of time groups. By default, o-type = 0, the same number of particles is generated in each bin. When o-type = 1 and o(i) is specified, the integrated number of generated particles in each bin is proportional to those values.
tg1: Lower cutoff value of the time distribution [ns].
tg2: Upper cutoff value of the time distribution [ns].
o-type = 0, 1: Generation-number option, D = 0.
For 0, o(i)=1 in all bins, and there is no following data.
For 1, the generation-number ratio o(i) in each bin is given in the following line.
(o(i), i = 1, ll)
5.3.21.6. t-type = 100¶
By specifying t-type = 100 and modifying the PHITS source file, an arbitrary time distribution can be given as a function of energy.
To use this function, modify the subroutine tdis01 in the source file sors.f.
tg1: Lower cutoff value of the time distribution [ns].
tg2: Upper cutoff value of the time distribution [ns].