PHOTOPiC · PHOTO-ionization Parameter Calculator

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About

This software is dedicated for treatment of experimental measurements of plasma data.
In case of any questions please contact Dr.Yifei ZHU.

Email: Yifei.zhu.plasma@gmail.com

About

PASSKEy - 02/2021

A two-dimensional drift-diffusion fluid equation solver for low temperature plasmas code generator

Created by Yifei ZHU - yifei.zhu.plasma@gmail.com

Improved by teams from:
Atelier des Plasmas Co, Ltd., Hefei, China
Xi\'an Jiaotong University, Xi\'an, China
Ecole Polytechnique, Paris, France

Permission to use PASSKEy is granted, provided that proper reference is made in any publications making use of the
code generated with this software. For specific usage and cooperations please contact the author.

About PHOTOPiC

PHOTOPiC 是一款计算气体放电光电离参数的在线工具，用于识别主导光电离的气体、计算混合气体中各气体的光电离函数，并拟合高效光电离模型（Helmholtz）的参数，用于 PASSKEy 等各类低温等离子体数值模拟程序。内置 N₂、O₂、CO₂、H₂O 气体数据库，并支持用户自定义气体。模型理论来源于 S. Pancheshnyi 博士，由西安交通大学朱益飞教授团队与等离子体计算工坊开发维护。

PHOTOPiC is an online tool to calculate photo-ionization parameters for numerical simulation of plasma discharges. A database of N₂, O₂, CO₂, H₂O is incorporated, and custom gases can be added. It can (1) identify the dominant specie responsible for photo-ionization; (2) compute photo-ionization functions for every gas in the mixture; (3) fit parameters of efficient photo-ionization models. Algorithm based on Ref [1,2] and succeeded in [3].

[1] S. Pancheshnyi, "Photoionization produced by low-current discharges in O₂, air, N₂ and CO₂," Plasma Sources Sci. Technol. 24 (2015) 015023.

[2] A. Bourdon et al., "Efficient models for photoionization... three-group Helmholtz," Plasma Sources Sci. Technol. 16 (2007) 656.

[3] X. Chen, Y. Zhu, Y. Wu, J. Hao, X. Ma, and P. Lu, "Modeling of fast ionization waves in pure nitrogen at moderate pressure," Plasma Sources Sci. Technol. 30 (2021) 065002.

Photo-ionization function of gas i (ionized gas) to gas j (radiating gas)

Psi_0/p (pr)_ij = eta_j · (1/4π) · (ω/α_eff)_ij · [∫ ξ_λi (μ_λi/p) exp(−(μ_λ^ij/p) pr) I0_λj dλ] / [∫ I0_λj dλ] · (p_q/(p+p_q))_ij

Gas mixture & database

	Gas	Fraction (%)	λ_max (nm)	Data

Ticked fractions are normalised to 100% for the calculation. Σ active = 0%

Conditions & parameters

Live update

Temperature K ?

Pressure Torr ?

Pr range Torr·cm ?

–

Resolution points ?

Physics parameters ?

Cross-sections σ (m²)

Emission spectra I₀ (a.u.)

Ψ(pr) ≈ pr · Σ Aₘ·exp(−λₘ·pr)

term	Aₘ	λₘ

Fitted with the Nelder–Mead simplex method in log space. Use these parameters in your solver (e.g. PASSKEy) — see Userguide §2.5.

Fitted curve vs target Ψ(pr)

Parameter guide

Temperature T (K)

Gas temperature. Enters the absorption coefficient μ = σ_abs/(k_B·T). Default 298 K.

Pressure P (Torr)

Ambient (total) pressure — not the O₂ partial pressure. Scales absorption and quenching.

Reduced distance pr (Torr·cm)

Product of pressure and distance. The photo-ionization function Ψ is reported versus pr.

Cross-sections σ_ion, σ_abs

Photo-ionization and photo-absorption cross-sections per gas (×10⁻¹⁸ m² in the data files). Their ratio gives the ionization yield ν = σ_ion/σ_abs.

Emission spectrum I₀(λ)

Optical emission spectrum of the emitting gas over as wide a range as possible (nm).

λ_max (nm)

Upper integration limit = ionization threshold of the ionized gas (one value per gas).

λ_min (nm)

Lower integration limit, chosen so at least two spectral peaks fall in [λ_min, λ_max] for the emitting gas.

Scale factor ξ

Scales the absolute value (not the profile) of Ψ; relates to the radiative transition system. Set 1 for the classical (unscaled) formulation.

Quenching pressure p_q

Pressure correction p_q/(P+p_q) for collisional quenching of radiating states. Set very large for the low-pressure limit (factor→1).

Helmholtz Aₘ, λₘ

Coefficients of the three-term Helmholtz model fitted to Ψ(pr) for use in streamer/discharge solvers.

Note: cross-section abscissa is used on the same numeric axis as the nm integration limits, consistent with the original PHOTOPiC pipeline.

Gas mixture & database

Conditions & parameters

Add / edit custom gas

Advanced physics matrices

Gas data