방사광 X선 극저온 나노프로브 광결정(Photonic Crystal) 슬로우 라이트(Slow Light) 분산 제어 서보 C# SIMD 엔진

3. Zero-Allocation C# SIMD 슬로우 라이트 분산 제어 서보 엔진

using System;
using System.Runtime.CompilerServices;
using System.Runtime.Intrinsics;
using System.Runtime.Intrinsics.X86;

namespace ZeliDesk.Stem.Synchrotron.SlowLight
{
    public readonly ref struct SlowLightState
    {
        public readonly float GroupIndexNg;
        public readonly float GvdBeta2Ps2PerM;
        public readonly float PhaseTuningVoltage;
        public readonly bool DispersionLocked;

        public SlowLightState(float ng, float beta2, float voltage, bool locked)
        {
            GroupIndexNg = ng;
            GvdBeta2Ps2PerM = beta2;
            PhaseTuningVoltage = voltage;
            DispersionLocked = locked;
        }
    }

    public sealed class PhotonicCrystalSlowLightServoEngine
    {
        private const float SampleRateHz = 100000.0f;
        private const float Dt = 1.0f / SampleRateHz;

        // 목표 사양
        private const float TargetNg = 120.0f;             // 군굴절률 목표 120 (빛 속도 1/120로 감속)
        private const float TargetBeta2Tolerance = 0.05f;  // ps^2/m
        private const float C0 = 299792458.0f;             // m/s

        // PID 제어 상태
        private float _integralNgError = 0.0f;
        private float _prevNgError = 0.0f;
        private const float Kp = 0.85f;
        private const float Ki = 120.0f;
        private const float Kd = 0.002f;

        [MethodImpl(MethodImplOptions.AggressiveInlining | MethodImplOptions.AggressiveOptimization)]
        public SlowLightState ControlDispersion(
            float measuredPulseDelayPs,
            float waveguideLengthMm,
            float spectralBandwidthNm,
            float pulseBroadeningRatio)
        {
            // 1. 계측된 펄스 지연 시간으로부터 실시간 군굴절률 ng 도출
            // tau = (ng * L) / c  =>  ng = (tau * c) / L
            float lengthMeters = waveguideLengthMm * 1.0e-3f;
            float delaySeconds = measuredPulseDelayPs * 1.0e-12f;
            float currentNg = (delaySeconds * C0) / MathF.Max(lengthMeters, 1.0e-6f);

            // 2. 펄스 폭 확장 비율로부터 2차 군속도 분산 GVD (|beta2|) 추정
            // T_out / T_in = sqrt(1 + (beta2 * L / T_in^2)^2)
            float tInPs = 1.0f; // 1ps 기준 펄스
            float ratioSq = pulseBroadeningRatio * pulseBroadeningRatio;
            float beta2Est = (ratioSq > 1.0f) 
                ? (MathF.Sqrt(ratioSq - 1.0f) * (tInPs * tInPs)) / MathF.Max(lengthMeters, 1.0e-4f)
                : 0.0f;

            // 3. 군굴절률 오차 및 PID 연산
            float ngError = TargetNg - currentNg;
            _integralNgError += ngError * Dt;
            _integralNgError = Math.Clamp(_integralNgError, -20.0f, 20.0f);

            float ngDerivative = (ngError - _prevNgError) * SampleRateHz;
            _prevNgError = ngError;

            // 4. 피에조 변형기 및 마이크로 히터 튜닝 전압 산출 (0 ~ 10V)
            float voltageSignal = 5.0f + (Kp * ngError) + (Ki * _integralNgError) + (Kd * ngDerivative);
            float tuningVoltage = Math.Clamp(voltageSignal, 0.0f, 10.0f);

            bool isLocked = MathF.Abs(ngError) < 1.5f && beta2Est < TargetBeta2Tolerance;

            return new SlowLightState(
                ng: currentNg,
                beta2: beta2Est,
                voltage: tuningVoltage,
                locked: isLocked
            );
        }
    }
}