sub_G01_collision1.f90

中文 English

直接用途

sub_G01_collision1 执行电子-中性粒子 MCC 碰撞，并可能更新电子和离子粒子数。

参数表

参数	方向	shape/范围	含义与局部约定
np1	in/out	scalar or caller-provided array	integer, number of electron particles.
np2	in/out	scalar or caller-provided array	integer, number of ion particles.
npmax1	in	scalar or caller-provided array	integer, maximum number of electron particles.
npmax2	in	scalar or caller-provided array	integer, maximum number of ion particles.
par1	in/out	(1:6,1:npmax1)	real (1:6,1:npmax1), electron particle array.
par2	in/out	(1:6,1:npmax2)	real (1:6,1:npmax2), ion particle array.
dt	in	scalar or caller-provided array	时间步长。
e	in	scalar or caller-provided array	基本电荷或电荷单位换算因子。
m1	in	scalar or caller-provided array	第一类粒子质量。
m2	in	scalar or caller-provided array	第二类粒子质量。
Nmax	in	scalar or caller-provided array	截面表最大点数。
Ntype	in	scalar or caller-provided array	碰撞类型数。
cross_section	in	(1:2,1:Nmax,1:Ntype)	截面表；第一行通常为能量，第二行为截面值。
collision_type	in	(1:Ntype)	碰撞类型编号数组。
vti	in	scalar or caller-provided array	中性粒子热速度。
vd	in	(1:3)	漂移速度向量。
energy_excitation	in	scalar or caller-provided array	激发能量阈值。
energy_ionization	in	scalar or caller-provided array	电离能量阈值。
il	in	(1:3)	本地 active cell 下界索引。
iu	in	(1:3)	本地 active cell 上界索引。
den	in	scalar or caller-provided array	背景密度或中性粒子密度场，按粒子位置插值得到局部密度。
S	in/out	scalar or caller-provided array	源项数组。
energy_min	in	scalar or caller-provided array	计算/查表能量下界。
energy_max	in	scalar or caller-provided array	计算/查表能量上界。
eV	in	scalar or caller-provided array	电子伏特换算因子。
wei	in	scalar or caller-provided array	粒子权重。
nu_max	in/out	scalar or caller-provided array	null-collision 最大频率，可输入缓存值并由例程更新。

局部假设

碰撞例程假定粒子数组 par(1:6,...) 中 1:3 是位置、4:6 是速度。随机数来自 Fortran random_number；能量、截面、密度和时间步单位必须由调用方保持自洽。这里不替调用方设置随机种子。

实现逻辑

实现先计算或复用 nu_max，再用 null-collision 概率抽取候选粒子；每个候选粒子按截面权重选择碰撞类型并更新速度或粒子数组。

调用注意

本页只说明该例程本身的调用边界和实现事实；完整接口声明和源码级 API 仍以英文侧的 generated API 为准。

Direct Purpose

sub_G01_collision1 electron-neutral collision process based on Vahedi’s MCC algorithm.

Parameter Table

Parameter	Direction	Shape/range	Meaning and local convention
np1	in/out	scalar or caller-provided array	integer, number of electron particles.
np2	in/out	scalar or caller-provided array	integer, number of ion particles.
npmax1	in	scalar or caller-provided array	integer, maximum number of electron particles.
npmax2	in	scalar or caller-provided array	integer, maximum number of ion particles.
par1	in/out	(1:6,1:npmax1)	real (1:6,1:npmax1), electron particle array.
par2	in/out	(1:6,1:npmax2)	real (1:6,1:npmax2), ion particle array.
dt	in	scalar or caller-provided array	real, simulation time step.
e	in	scalar or caller-provided array	real, unit charge.
m1	in	scalar or caller-provided array	real, electron mass.
m2	in	scalar or caller-provided array	real, neutral particle mass.
Nmax	in	scalar or caller-provided array	integer, maximum number of energy grid points.
Ntype	in	scalar or caller-provided array	integer, number of collision types.
cross_section	in	(1:2,1:Nmax,1:Ntype)	real (1:2,1:Nmax,1:Ntype), cross-section tables.
collision_type	in	(1:Ntype)	integer (1:Ntype), collision type identifiers.
vti	in	scalar or caller-provided array	real, thermal velocity of ions.
vd	in	(1:3)	real (1:3), drifting velocity.
energy_excitation	in	scalar or caller-provided array	real, excitation energy threshold.
energy_ionization	in	scalar or caller-provided array	real, ionization energy threshold.
il	in	(1:3)	integer (1:3), cell-center lower indices in x,y,z.
iu	in	(1:3)	integer (1:3), cell-center upper indices in x,y,z.
den	in	scalar or caller-provided array	real, neutral density defined on grid points.
S	in/out	scalar or caller-provided array	real, ionization source term on grid points.
energy_min	in	scalar or caller-provided array	real, minimum energy (eV) for nu_prime evaluation.
energy_max	in	scalar or caller-provided array	real, maximum energy (eV) for nu_prime evaluation.
eV	in	scalar or caller-provided array	real, electron volt conversion factor.
wei	in	scalar or caller-provided array	real, particle weight.
nu_max	in/out	scalar or caller-provided array	real, maximum collision frequency nu_prime.

Local Assumptions

Collision routines assume par(1:6,...) stores position in 1:3 and velocity in 4:6. Random numbers come from Fortran random_number. Units of energy, cross section, density, and time step must be kept self-consistent by the caller. These routines do not seed the RNG.

Implementation Notes

The implementation computes or reuses nu_max, samples candidate particles with a null-collision probability, then selects collision type by cross-section weights and updates velocity or particle arrays.

Generated API

Electron-neutral collision process based on Vahedi’s MCC algorithm.

Functions

subroutine sub_g01_collision1(np1, np2, npmax1, npmax2, par1, par2, dt, e, m1, m2, nmax, ntype, cross_section, collision_type, vti, vd, energy_excitation, energy_ionization, il, iu, den, s, energy_min, energy_max, ev, wei, nu_max)

This subroutine implements a Monte Carlo collision (MCC) model for electron-neutral interactions following the classic algorithm proposed by V. Vahedi (CPC 87, 1995, 179-198). Elastic scattering, excitation, and ionization processes are handled using the null-collision method. The maximum collision frequency nu_max is computed only once and reused in subsequent calls. Particle collisions are sampled statistically, and ionization events generate new electron and ion particles while accumulating the ionization source term S on the grid.

Author

Lihuan XIE (2025/12/18)

Parameters:

• np1 – [inout] integer, number of electron particles.

• np2 – [inout] integer, number of ion particles.

• npmax1 – [in] integer, maximum number of electron particles.

• npmax2 – [in] integer, maximum number of ion particles.

• par1 – [inout] real (1:6,1:npmax1), electron particle array.

• par2 – [inout] real (1:6,1:npmax2), ion particle array.

• dt – [in] real, simulation time step.

• e – [in] real, unit charge.

• m1 – [in] real, electron mass.

• m2 – [in] real, neutral particle mass.

• Nmax – [in] integer, maximum number of energy grid points.

• Ntype – [in] integer, number of collision types.

• cross_section – [in] real (1:2,1:Nmax,1:Ntype), cross-section tables.

• collision_type – [in] integer (1:Ntype), collision type identifiers.

• vti – [in] real, thermal velocity of ions.

• vd – [in] real (1:3), drifting velocity.

• energy_excitation – [in] real, excitation energy threshold.

• energy_ionization – [in] real, ionization energy threshold.

• il – [in] integer (1:3), cell-center lower indices in x,y,z.

• iu – [in] integer (1:3), cell-center upper indices in x,y,z.

• den – [in] real, neutral density defined on grid points.

• S – [inout] real, ionization source term on grid points.

• energy_min – [in] real, minimum energy (eV) for nu_prime evaluation.

• energy_max – [in] real, maximum energy (eV) for nu_prime evaluation.

• eV – [in] real, electron volt conversion factor.

• wei – [in] real, particle weight.

• nu_max – [inout] real, maximum collision frequency nu_prime.