5.3.19.1. Continuous energy distribution with integral value

5.3.19.1.1. e-type = 1, (11)

Any energy distribution can be specified by providing the data set of energy bins e(i) and the integrated values of the particle generation probabilities w(i) by hand. The number of particles generated in a bin is proportional to w(i), and the specified energy distribution is statistically described. For case 11, the energy is given by the wave length (A).

ne : Number of energy groups. If this is a positive number, source particles are generated so that the energy differential fluxes in units of [1/MeV] become constant in each bin. If negative, the fluxes in units of [1/Lethargy] become constant for each bin. Data must be provided in the following line using the format (e(i), w(i), i=1, ne), e(ne+1). The integrated numbers of particles generated in each energy bin is proportional to w(i).

5.3.19.1.2. e-type = 4, (14)

The same energy distribution as in the case of e-type = 1, (11) can be specified, except with the energy bins e(i) and weights of the source particle w(i) entered by hand. The number of source particles generated in each bin is the same for all energy bins, but integrated values of the weights of source particles are adjusted to be proportional to w(i). The number of source particles generated in each bin can also be changed by specifying p(i). For case 14, the energy is given by wave length (A).

ne : Number of energy groups. If this is a positive number, source particles are generated so that the energy differential fluxes in units of [1/MeV] become constant in each bin. If negative, the fluxes in units of [1/Lethargy] become constant for each bin. Data must be provided in the following line using the format (e(i), w(i), i=1, ne), e(ne+1). In the default (p-type = 0), equal numbers of particles are generated in each cell. The integrated number of source particles generated in each bin is proportional to p(i).

p-type = 0, 1 : (D = 0) generation option.

• For 0, p(i) = 1 for all i is assumed without the following data.

• For 1, p(i) must be given from the next line using the format

(p(i),i=1,ne).

In the case of e-type = 1, the format is as follows.

e-type = 1
  ne = n
    e(1)   w(1)
    e(2)   w(2)
    e(3)   w(3)
    ....   ...
    e(n-1) w(n-1)
    e(n)   w(n)
    e(n+1)

In this case, the energy distribution is given as

e(1)-e(2)   w(1)
e(2)-e(3)   w(2)
e(3)-e(4)   w(3)
.......     ...
e(n-1)-e(n) w(n-1)
e(n)-e(n+1) w(n)

As an example, use the following code to set the strengths of three energy bins between 0-2 MeV, 2-4 MeV, and 4-6 MeV as 0.2, 0.6, and 0.2, respectively.

e-type = 1
  ne = 3
    0   0.2
    2   0.6
    4   0.2
    6

An alternative option for neutron optics has been developed to specify the energy as a wavelength: if e-type is set to 11, 12, 14, the wavelength (A) is used as the energy unit. In the other cases, the expression e0 = 8.180425e-8/13**2 is used, which corresponds to the energy of a neutron with a 13 A wavelength.