레이저 관성가둠 핵융합(ICF) 펠릿 레일리-테일러(Rayleigh-Taylor) 불안정성 & 1,000Hz 0-Alloc C# 폭축 대칭성 제어 엔진

using System;
using System.Runtime.CompilerServices;

namespace ZeliDesk.Stem.LaserFusion;

public readonly ref struct IcfImplosionState
{
    public readonly double ShellRadiusMicrons;
    public readonly double HotspotTemperatureKev;
    public readonly double ImplosionVelocityKmS;
    public readonly double RtPerturbationRatio;
    public readonly bool IsIgnitionAchieved;

    [MethodImpl(MethodImplOptions.AggressiveInlining)]
    public IcfImplosionState(double rShell, double tHot, double vImp, double rtRatio, bool ignition)
    {
        ShellRadiusMicrons = rShell;
        HotspotTemperatureKev = tHot;
        ImplosionVelocityKmS = vImp;
        RtPerturbationRatio = rtRatio;
        IsIgnitionAchieved = ignition;
    }
}

public ref struct LaserFusionIcfSimulator
{
    private const double InitialRadiusUm = 1000.0; // 1mm 캡슐
    private const double AblationVelocityMps = 3.0e4; // 30 km/s 삭마 속도

    private double _shellRadiusM;
    private double _implosionVelocityMps;
    private double _perturbationAmpM;

    [MethodImpl(MethodImplOptions.AggressiveInlining)]
    public LaserFusionIcfSimulator(double initialPerturbationUm = 0.05)
    {
        _shellRadiusM = InitialRadiusUm * 1e-6;
        _implosionVelocityMps = 0.0;
        _perturbationAmpM = initialPerturbationUm * 1e-6;
    }

    [MethodImpl(MethodImplOptions.AggressiveInlining)]
    public IcfImplosionState Step(double ablationPressureMbar, double laserAsymmetryPercent, double dtSeconds = 1.0e-9) // 1ns 스텝
    {
        // 1. 삭마 압력에 의한 쉘 가속도 산출
        double pressurePa = ablationPressureMbar * 1e11; // 1 Mbar = 10^11 Pa
        double shellArealMass = 0.02 * (_shellRadiusM / (InitialRadiusUm * 1e-6)); // kg/m^2
        double acceleration = pressurePa / Math.Max(1e-4, shellArealMass);

        // 2. 폭축 속도 및 반경 적분
        _implosionVelocityMps += acceleration * dtSeconds;
        _shellRadiusM -= _implosionVelocityMps * dtSeconds;
        if (_shellRadiusM < 25.0e-6) _shellRadiusM = 25.0e-6; // 최소 핫스팟 반경 25 um

        // 3. 레일리-테일러 불안정성 모드 성장 (l = 4 사중극자 모드)
        double k = 4.0 / Math.Max(1e-6, _shellRadiusM);
        double classicalGammaSq = k * acceleration;
        double stabFactor = 1.8 * k * AblationVelocityMps;
        double netGamma = Math.Sqrt(Math.Max(0.0, classicalGammaSq)) - stabFactor;

        if (netGamma > 0.0)
        {
            _perturbationAmpM += (_perturbationAmpM * netGamma + laserAsymmetryPercent * 1e-8) * dtSeconds;
        }

        // 4. 단열 압축 핫스팟 온도 (keV 스케일)
        double convergenceRatio = (InitialRadiusUm * 1e-6) / _shellRadiusM;
        double hotspotTempKev = 0.1 * Math.Pow(convergenceRatio, 4.0 / 3.0);

        double shellRadiusUm = _shellRadiusM * 1e6;
        double implosionVelocityKmS = _implosionVelocityMps * 1e-3;
        double rtRatio = _perturbationAmpM / _shellRadiusM;

        // 5. 점화 판정: 폭축 속도 > 350 km/s, T_hs > 5 keV, RT 파열비 < 0.25
        bool ignition = implosionVelocityKmS > 350.0 && hotspotTempKev > 4.5 && rtRatio < 0.25;

        return new IcfImplosionState(shellRadiusUm, hotspotTempKev, implosionVelocityKmS, rtRatio, ignition);
    }
}