레이저 후류장 가속(LWFA) 플라스마 버블 전자 가속 & 1,000Hz 0-Alloc C# 펨토초 레이저 포커싱 서보 엔진

using System;
using System.Runtime.CompilerServices;
using System.Runtime.InteropServices;

namespace ZeliDesk.Stem.LwfaControl
{
    /// <summary>
    /// 4채널 제르니케 저차 수차 모드 (디포커스, 난시, 코마, 구면수차)
    /// </summary>
    [StructLayout(LayoutKind.Sequential, Pack = 8)]
    public readonly struct ZernikeAberrations
    {
        public readonly double Defocus;      // Z(2, 0)
        public readonly double AstigmatismX; // Z(2, 2)
        public readonly double ComaX;        // Z(3, 1)
        public readonly double Spherical;    // Z(4, 0)

        public ZernikeAberrations(double defocus, double astigmatism, double coma, double spherical)
        {
            Defocus = defocus;
            AstigmatismX = astigmatism;
            ComaX = coma;
            Spherical = spherical;
        }
    }

    /// <summary>
    /// 디포머블 미러 액추에이터 전압 출력 벡터 (스택 할당 0-Alloc)
    /// </summary>
    public ref struct MirrorActuatorVoltages
    {
        public double Ch1;
        public double Ch2;
        public double Ch3;
        public double Ch4;

        [MethodImpl(MethodImplOptions.AggressiveInlining)]
        public MirrorActuatorVoltages(double v1, double v2, double v3, double v4)
        {
            Ch1 = v1;
            Ch2 = v2;
            Ch3 = v3;
            Ch4 = v4;
        }
    }

    /// <summary>
    /// 1,000Hz 무할당 LWFA 레이저 포커싱 서보 엔진
    /// </summary>
    public ref struct LwfaBeamFocusingServoEngine
    {
        private const double TargetPeakIntensity = 5.0e18; // 목표 레이저 강도 (W/cm^2)
        private const double LaserWavelengthUm = 0.8;      // Ti:Sapphire 중심 파장 (um)
        private const double PlasmaDensity = 2.5e18;       // 전자 밀도 (cm^-3)

        private double _defocusIntegral;
        private double _astigmatismIntegral;
        private double _comaIntegral;
        private double _sphericalIntegral;

        [MethodImpl(MethodImplOptions.AggressiveInlining)]
        public void ExecuteControlCycle(
            in ZernikeAberrations measuredAberration,
            double laserPulseEnergyJoule,
            double spotSizeRadiusUm,
            out MirrorActuatorVoltages actuatorVoltages,
            out double estimatedA0,
            out double acceleratingFieldGvPerM)
        {
            // 1. 레이저 상대론적 무차원 세기 a0 실시간 추정
            double focalAreaCm2 = Math.PI * Math.Pow(spotSizeRadiusUm * 1.0e-4, 2.0);
            double pulseDurationSec = 30.0e-15; // 30 fs
            double peakPowerWatts = laserPulseEnergyJoule / pulseDurationSec;
            double intensityWPerCm2 = peakPowerWatts / Math.Max(focalAreaCm2, 1e-12);

            estimatedA0 = 0.855e-9 * LaserWavelengthUm * Math.Sqrt(Math.Max(0.0, intensityWPerCm2));

            // 2. 종방향 최대 가속 전계 강도 계산 (GV/m)
            acceleratingFieldGvPerM = 96.0 * Math.Sqrt(PlasmaDensity / 1.0e18);

            // 3. 파면 수차 억제를 위한 비례-적분(PI) 제어 루프
            _defocusIntegral += measuredAberration.Defocus * 0.001;
            _astigmatismIntegral += measuredAberration.AstigmatismX * 0.001;
            _comaIntegral += measuredAberration.ComaX * 0.001;
            _sphericalIntegral += measuredAberration.Spherical * 0.001;

            double kp = 45.0;
            double ki = 320.0;

            double uDefocus = kp * measuredAberration.Defocus + ki * _defocusIntegral;
            double uAstig = kp * measuredAberration.AstigmatismX + ki * _astigmatismIntegral;
            double uComa = kp * measuredAberration.ComaX + ki * _comaIntegral;
            double uSpher = kp * measuredAberration.Spherical + ki * _sphericalIntegral;

            // 4. 모드 변환 행렬(Influence Matrix)을 통한 액추에이터 구동 전압 맵핑
            double v1 = 0.5 * uDefocus + 0.5 * uAstig + 0.25 * uSpher;
            double v2 = 0.5 * uDefocus - 0.5 * uAstig + 0.25 * uSpher;
            double v3 = 0.5 * uDefocus + 0.5 * uComa - 0.25 * uSpher;
            double v4 = 0.5 * uDefocus - 0.5 * uComa - 0.25 * uSpher;

            // 전압 리미터 (-100V ~ +100V)
            v1 = Math.Clamp(v1, -100.0, 100.0);
            v2 = Math.Clamp(v2, -100.0, 100.0);
            v3 = Math.Clamp(v3, -100.0, 100.0);
            v4 = Math.Clamp(v4, -100.0, 100.0);

            actuatorVoltages = new MirrorActuatorVoltages(v1, v2, v3, v4);
        }
    }
}