JAEA-Conf 2011-002 - 日本原子力研究開発機構

Ztarget, Atarget are the numbers for the recoil target atom and Ttarget is the PKA energy of target. Equation (7)
indicates the scattering cross section multiplied by the number of defects.
Based on the Kinchin and Pease formula [10] modified by Norgett et al. and using the Lindhard
slowing-down theory, the number of defects produced in irradiated material is calculated
(8)
Where NNRT is the number of defects calculated by
The constant 0.8 in the formula is the displacement efficiency given independent of the PKA energy, the
target material, or its temperature. The value is intended to compensate for forward scattering in the
displacement cascade of the atoms of the lattice. Tdamage is the “damage energy” transferred to the lattice
atoms reduced by the losses for electronic stopping in the atom displacement cascade and is given by
Norgett, Robinson, and Torrens.
(9)
(10)
Where T is the transferred energy to target atom given by equation (2) as
where p is the dimensionless projectile energy given by equation (4) and the projectile energy Ep. The
parameters kcascade, and g() are as follows:
(11)
(12)
(13)
is the dimensionless transferred energy given by equations (4) and (11). The following equation shows the
summary from equations (7), (9), and (10).
JAEA-Conf 2011-002
shows a damage cross sections (eq. 14) and Coulomb scattering cross sections (T > Ed) (eq. 6)
with threshold energy of 25 eV for the Ge + W scattering. As the cross section for Coulomb scattering (T >
Ed) is much larger (~10 7 – 10 9 b) than the nuclear reaction cross section (~mb order) which are treated in
PHITS, it is difficult to calculate the DPA using full Monte Carlo calculation with Coulomb scattering in
PHITS because of spending much time for calculations. Therefore, only a part of the transferred energy to
the target T is calculated by PHITS, and damage cross sections is estimated with Eq. (14). Note that this
calculation does not include the self-healing of lattice defects.
(14)