# Tesla Coil Spark Course - Image Requirements

This document lists all images needed for the interactive lesson application, organized by section. Each entry includes specifications for creation.

**Total Images Required: 45+**

## Current Status (Updated 2025-10-10)

**Images Complete: 37 / 45+**

| Status | Count | Description |
|--------|-------|-------------|
| ✓ Generated (matplotlib) | 22 | High-quality programmatically generated graphs, plots, tables |
| ⚠ Placeholder | 15 | Placeholders created with descriptions for manual creation |
| ❌ Specification Only | 7 | Circuit diagrams - see CIRCUIT-SPECIFICATIONS.md |
| ➖ Optional/Future | 1 | Nice-to-have images for future enhancement |

### Generated Images (22)
- **Fundamentals (4):** complex-plane-admittance, phase-angle-visualization, phase-constraint-graph, admittance-vector-addition
- **Optimization (4):** power-vs-resistance-curves, frequency-shift-with-loading, drsstc-operating-modes, loaded-pole-analysis
- **Spark Physics (6):** energy-budget-breakdown, epsilon-by-mode-comparison, thermal-diffusion-vs-diameter, voltage-division-vs-length-plot, length-vs-energy-scaling, qcw-vs-burst-timeline
- **Advanced Modeling (7):** capacitance-matrix-heatmap, resistance-taper-initialization, power-distribution-along-spark, current-attenuation-plot, lumped-vs-distributed-comparison, position-dependent-bounds, validation-total-resistance
- **Shared (1):** complex-number-review

### Manual Creation Required
- **Circuit Diagrams (7):** See CIRCUIT-SPECIFICATIONS.md for detailed specs
- **FEMM Screenshots (5):** Require professional electrostatic simulations
- **Photography (3):** High-speed photography of actual sparks
- **Complex Diagrams (7):** Flowcharts, feedback loops, etc.

**Scripts:**
- `generate_images.py` - Generates all 22 matplotlib images
- `generate_placeholders.py` - Creates 15 placeholder images with specs
- Both scripts are rerunnable and include documentation

### Quick Status Reference

| Image # | Name | Status |
|---------|------|--------|
| 1 | field-lines-capacitances | ⚠ Placeholder (FEMM) |
| 2 | geometry-to-circuit | ❌ Circuit Spec |
| 3 | complex-plane-admittance | ✓ Generated |
| 4 | phase-angle-visualization | ✓ Generated |
| 5 | phase-constraint-graph | ✓ Generated |
| 6 | current-paths-diagram | ❌ Circuit Spec |
| 7 | admittance-vector-addition | ✓ Generated |
| 8 | impedance-matching-concept | ⚠ Placeholder (Diagram) |
| 9 | power-vs-resistance-curves | ✓ Generated |
| 10 | hungry-streamer-feedback-loop | ⚠ Placeholder (Diagram) |
| 11 | thevenin-measurement-setup | ⚠ Placeholder (Diagram) |
| 12 | thevenin-equivalent-circuit | ❌ Circuit Spec |
| 13 | frequency-shift-with-loading | ✓ Generated |
| 14 | drsstc-operating-modes | ✓ Generated |
| 15 | loaded-pole-analysis | ✓ Generated |
| 16 | electric-field-enhancement | ⚠ Placeholder (FEMM) |
| 17 | femm-field-plot-example | ⚠ Placeholder (FEMM) |
| 18 | energy-budget-breakdown | ✓ Generated |
| 19 | epsilon-by-mode-comparison | ✓ Generated |
| 20 | thermal-diffusion-vs-diameter | ✓ Generated |
| 21 | spark-channel-persistence-sequence | ⚠ Placeholder (Photo) |
| 22 | streamers-vs-leaders-photos | ⚠ Placeholder (Photo) |
| 23 | streamer-to-leader-transition-sequence | ⚠ Placeholder (Photo/Diagram) |
| 24 | voltage-division-vs-length-plot | ✓ Generated |
| 25 | capacitive-divider-circuit | ❌ Circuit Spec |
| 26 | length-vs-energy-scaling | ✓ Generated |
| 27 | qcw-vs-burst-timeline | ✓ Generated |
| 28 | lumped-model-schematic | ❌ Circuit Spec |
| 29 | femm-geometry-setup-lumped | ⚠ Placeholder (FEMM) |
| 30 | maxwell-matrix-extraction | ⚠ Placeholder (Diagram) |
| 31 | lumped-model-validation-checks | ⚠ Placeholder (Diagram) |
| 32 | distributed-model-structure | ❌ Circuit Spec |
| 33 | femm-geometry-setup-distributed | ⚠ Placeholder (FEMM) |
| 34 | capacitance-matrix-heatmap | ✓ Generated |
| 35 | partial-capacitance-transformation | ⚠ Placeholder (Diagram) |
| 36 | resistance-taper-initialization | ✓ Generated |
| 37 | iterative-optimization-convergence | ⚠ Placeholder (Diagram) |
| 38 | power-distribution-along-spark | ✓ Generated |
| 39 | current-attenuation-plot | ✓ Generated |
| 40 | lumped-vs-distributed-comparison | ✓ Generated |
| 41 | position-dependent-bounds | ✓ Generated |
| 42 | spice-implementation-methods | ⚠ Placeholder (Diagram) |
| 43 | validation-total-resistance | ✓ Generated |
| 44 | tesla-coil-system-overview | ❌ Circuit Spec |
| 45 | complex-number-review | ✓ Generated |

---

## Part 1: Fundamentals (8 images)

### 1. **field-lines-capacitances.png**
**Location:** `lessons/01-fundamentals/assets/`
**Referenced in:** fund-02 (Basic Circuit Model)

**Description:**
3D visualization showing electric field lines between topload (spherical or toroidal) and a cylindrical spark channel.

**Details:**
- Show field lines for two cases side-by-side:
  - **Left**: C_mut field lines (coupling between topload and spark)
  - **Right**: C_sh field lines (spark to ground plane)
- Use different colors: Blue for C_mut, Red for C_sh
- Label key features: topload, spark channel, ground plane
- Add dimension arrows showing spark length
- Include legend with typical values (C_mut ~ 8 pF, C_sh ~ 6 pF for 3-foot spark)

**Suggested Format:** PNG, 1200x600 px, high contrast for dark/light mode

---

### 2. **geometry-to-circuit.png**
**Location:** `lessons/01-fundamentals/assets/`
**Referenced in:** fund-02 (Basic Circuit Model)

**Description:**
Side-by-side comparison showing physical geometry translating to circuit schematic.

**Details:**
- **Left side**: 3D rendering of topload with spark
  - Toroid or sphere topload
  - Cylindrical spark extending downward
  - Ground plane at bottom
  - Arrows indicating the two capacitive paths

- **Right side**: Circuit schematic
  - Topload node at top
  - (R || C_mut) in series with C_sh to ground
  - Clear node labels
  - Component values shown

**Suggested Format:** PNG, 1400x700 px

---

### 3. **complex-plane-admittance.png**
**Location:** `lessons/01-fundamentals/assets/`
**Referenced in:** fund-03 (Admittance Analysis)

**Description:**
Complex plane plots showing Y and Z phasors.

**Details:**
- Two complex planes side-by-side:
  - **Left**: Admittance (Y) plane with Re{Y} horizontal, Im{Y} vertical
  - **Right**: Impedance (Z) plane with Re{Z} horizontal, Im{Z} vertical
- Show example phasor on each: Y = 10 + j15 mS, Z = 30 - j45 Ω
- Mark angles θ_Y and φ_Z
- Show relationship φ_Z = -θ_Y with arrows
- Use grid lines for readability
- Color code: Conductance/Resistance (blue), Susceptance/Reactance (red)

**Suggested Format:** PNG, 1200x600 px

---

### 4. **phase-angle-visualization.png**
**Location:** `lessons/01-fundamentals/assets/`
**Referenced in:** fund-04 (Phase Angles)

**Description:**
Impedance phasors showing different phase angles and their meanings.

**Details:**
- Show 5 impedance phasors on single complex plane:
  1. Pure resistive (φ = 0°)
  2. Slightly capacitive (φ = -30°)
  3. Balanced (φ = -45°)
  4. More capacitive (φ = -60°)
  5. Highly capacitive (φ = -75°)
- Label each with physical interpretation
- Highlight -45° as "theoretical matched" with note: "Often impossible for Tesla coils"
- Show typical spark range (-55° to -75°) as shaded region
- Include power factor values for each

**Suggested Format:** PNG, 1000x800 px

---

### 5. **phase-constraint-graph.png**
**Location:** `lessons/01-fundamentals/assets/`
**Referenced in:** fund-05 (Phase Constraint)

**Description:**
Graph of minimum achievable phase angle vs capacitance ratio.

**Details:**
- X-axis: r = C_mut/C_sh (0 to 3)
- Y-axis: φ_Z,min (degrees, 0° to -90°)
- Plot curve: φ_Z,min = -atan(2√[r(1+r)])
- Mark critical point r = 0.207 where φ_Z,min = -45°
- Shade "impossible region" above curve
- Add horizontal line at -45° with label "Traditional 'matched' target"
- Mark typical Tesla coil region (r = 0.5 to 2.0)
- Include annotations for geometric examples

**Suggested Format:** PNG, 1000x700 px

---

### 6. **current-paths-diagram.png**
**Location:** `lessons/01-fundamentals/assets/`
**Referenced in:** fund-07 (Measurement Port)

**Description:**
Complete Tesla coil diagram showing all current paths.

**Details:**
- Full coil schematic: primary, secondary, topload, spark
- Show and label ALL current paths:
  1. I_spark (through spark resistance)
  2. I_displacement (topload to ground capacitance)
  3. I_coupling (primary to secondary capacitive coupling)
  4. I_secondary_sections (distributed capacitance to ground)
  5. I_base (total current at base)
- Use different colors/line styles for each current path
- Show I_base = I_spark + I_displacement + I_coupling + ...
- Highlight correct measurement port (topload-to-ground)
- Mark incorrect measurement location (I_base) with X

**Suggested Format:** PNG, 1000x1200 px (vertical)

---

### 7. **admittance-vector-addition.png**
**Location:** `lessons/01-fundamentals/assets/`
**Referenced in:** fund-03 (Admittance Analysis)

**Description:**
Vector diagram showing parallel admittance addition.

**Details:**
- Show two branches: Y₁ = G + jB₁ and Y₂ = jB₂
- Vector addition: Y_total = Y₁ + Y₂
- Graphical parallelogram method
- Label Re{Y} and Im{Y} components
- Show how parallel combination differs from series

**Suggested Format:** PNG, 800x600 px

---

### 8. **impedance-matching-concept.png**
**Location:** `lessons/01-fundamentals/assets/`
**Referenced in:** fund-06 (Why Not 45 Degrees)

**Description:**
Conceptual diagram comparing ideal vs. constrained matching.

**Details:**
- Show two scenarios side-by-side:
  - **Ideal**: Load impedance can be anywhere (full circle), conjugate match achievable
  - **Constrained**: Load impedance confined to sector (Tesla coil reality)
- Highlight φ_Z,min boundary
- Mark R_opt_power and R_opt_phase locations
- Show -45° target outside feasible region

**Suggested Format:** PNG, 1200x600 px

---

## Part 2: Optimization (7 images)

### 9. **power-vs-resistance-curves.png**
**Location:** `lessons/02-optimization/assets/`
**Referenced in:** opt-01 (Two Resistances)

**Description:**
Graph of power delivered vs. resistance, showing both optimal points.

**Details:**
- X-axis: Resistance R (log scale, 1 kΩ to 10 MΩ)
- Y-axis: Power delivered P (kW)
- Plot P(R) curve with clear peak at R_opt_power
- Mark R_opt_power with vertical line and label
- Mark R_opt_phase with different vertical line
- Show phase angle φ_Z(R) on secondary Y-axis
- Annotate: "R_opt_power maximizes power" and "R_opt_phase minimizes |φ_Z|"
- Include typical values: R_opt_power ~ 60 kΩ, R_opt_phase ~ 100 kΩ

**Suggested Format:** PNG, 1200x800 px

---

### 10. **hungry-streamer-feedback-loop.png**
**Location:** `lessons/02-optimization/assets/`
**Referenced in:** opt-02 (Hungry Streamer)

**Description:**
Feedback loop diagram showing self-optimization mechanism.

**Details:**
- Circular diagram with 6 steps:
  1. More power → Joule heating (I²R)
  2. Higher temperature → thermal ionization
  3. Increased n_e → higher conductivity
  4. Lower R → closer to R_opt
  5. Better matching → more power extracted
  6. Loop back to step 1
- Use arrows showing flow
- Add constraint boxes: R_min, R_max, source limits
- Show equilibrium point: R_actual ≈ R_opt_power
- Color code: Power (red), Temperature (orange), Conductivity (blue)

**Suggested Format:** PNG, 1000x1000 px

---

### 11. **thevenin-measurement-setup.png**
**Location:** `lessons/02-optimization/assets/`
**Referenced in:** opt-03 (Thévenin Method)

**Description:**
Two diagrams showing Z_th and V_th measurement procedures.

**Details:**
- **Top**: Z_th measurement
  - Tesla coil circuit with primary drive OFF
  - 1V AC test source at topload
  - Current measurement arrow
  - Labels: "Drive OFF", "Measure I_test", "Z_th = 1V / I_test"

- **Bottom**: V_th measurement
  - Tesla coil circuit with primary drive ON
  - No load (open circuit at topload)
  - Voltage measurement
  - Labels: "Drive ON", "No spark load", "Measure V_th"

**Suggested Format:** PNG, 1000x1000 px (vertical)

---

### 12. **thevenin-equivalent-circuit.png**
**Location:** `lessons/02-optimization/assets/`
**Referenced in:** opt-04 (Thévenin Calculations)

**Description:**
Thévenin equivalent with spark load.

**Details:**
- Simple circuit: V_th source → Z_th → Z_spark (load)
- Show voltage divider relationship
- Label currents and voltages
- Add power formula: P = 0.5|V_th|²Re{Z_spark}/|Z_th+Z_spark|²
- Show typical values: Z_th ~ 100 - j2400 Ω, V_th ~ 350 kV

**Suggested Format:** PNG, 800x600 px

---

### 13. **frequency-shift-with-loading.png**
**Location:** `lessons/02-optimization/assets/`
**Referenced in:** opt-06 (Frequency Tracking)

**Description:**
Graph showing resonant frequency shift as spark grows.

**Details:**
- X-axis: Spark length (meters, 0 to 3)
- Y-axis: Resonant frequency (kHz)
- Plot two curves:
  - Lower pole frequency (decreasing with length)
  - Upper pole frequency (increasing slightly with length)
- Mark unloaded resonance f₀
- Show C_sh increasing annotation (~ 2 pF/foot)
- Typical shift: 200 kHz → 175 kHz for 2 m spark
- Color code poles, add labels

**Suggested Format:** PNG, 1000x700 px

---

### 14. **drsstc-operating-modes.png**
**Location:** `lessons/02-optimization/assets/`
**Referenced in:** opt-06 (Frequency Tracking)

**Description:**
Three timing diagrams showing different DRSSTC operating modes.

**Details:**
- Three horizontal timelines:
  1. **Fixed frequency**: Square wave, constant frequency despite loading
  2. **PLL tracking**: Frequency adjusts as spark grows (show freq change)
  3. **Programmed sweep**: Frequency follows predetermined curve
- X-axis: Time (ms)
- Y-axis: Frequency or voltage
- Show spark growth underneath each
- Annotate pros/cons for each mode
- Color code drive signal (blue), actual resonance (red)

**Suggested Format:** PNG, 1200x800 px

---

### 15. **loaded-pole-analysis.png**
**Location:** `lessons/02-optimization/assets/`
**Referenced in:** opt-06 (Frequency Tracking)

**Description:**
Frequency domain showing coupled resonances.

**Details:**
- X-axis: Frequency (kHz, 150-250)
- Y-axis: |V_topload| (kV)
- Plot transfer function showing two poles (peaks)
- Show unloaded case (sharp peaks)
- Overlay loaded case (broader, shifted peaks)
- Mark operating frequency choices
- Annotate: "Wrong: operate at fixed f₀", "Right: track loaded pole"

**Suggested Format:** PNG, 1000x700 px

---

## Part 3: Spark Physics (12 images)

### 16. **electric-field-enhancement.png**
**Location:** `lessons/03-spark-physics/assets/`
**Referenced in:** phys-01 (Field Thresholds)

**Description:**
Field enhancement at spark tip vs. average field.

**Details:**
- Two side-by-side field plots from FEMM:
  - **Left**: Smooth topload (no spark), showing E_average
  - **Right**: With spark tip, showing E_tip with enhancement
- Color gradient showing field magnitude
- Mark E_tip location with annotation: κ × E_average
- Show tip enhancement factor κ ≈ 2-5
- Include scale bar and values

**Suggested Format:** PNG, 1400x700 px

---

### 17. **femm-field-plot-example.png**
**Location:** `lessons/03-spark-physics/assets/`
**Referenced in:** phys-02 (Voltage Limits)

**Description:**
FEMM electrostatic solution showing field distribution.

**Details:**
- Complete FEMM simulation output
- Toroid topload at 350 kV
- 2-meter spark extending down
- Color-coded field magnitude (rainbow scale)
- Equipotential lines overlaid
- Ground plane at bottom
- Field values annotated at key points
- Show E_propagation threshold line (e.g., 0.5 MV/m)

**Suggested Format:** PNG, 800x1200 px (vertical)

---

### 18. **energy-budget-breakdown.png**
**Location:** `lessons/03-spark-physics/assets/`
**Referenced in:** phys-03 (Energy Per Meter)

**Description:**
Pie chart showing energy distribution per meter of spark.

**Details:**
- Pie chart with segments for:
  - Ionization energy (40-50%)
  - Channel heating (20-30%)
  - Radiation losses (10-20%)
  - Shock wave / acoustic (5-10%)
  - Electrohydrodynamic work (5-10%)
- Label each segment with percentage
- Note total ε = 10 J/m (QCW example)
- Include annotation: "Minimum theoretical: ~0.5 J/m"

**Suggested Format:** PNG, 800x800 px

---

### 19. **epsilon-by-mode-comparison.png**
**Location:** `lessons/03-spark-physics/assets/`
**Referenced in:** phys-04 (Empirical Epsilon)

**Description:**
Bar chart comparing ε values by operating mode.

**Details:**
- X-axis: Operating mode (QCW, Hybrid DRSSTC, Hard-pulsed Burst)
- Y-axis: ε (J/m), log scale, 1-100
- Three bars with error ranges:
  - QCW: 5-15 J/m (green, efficient)
  - Hybrid: 20-40 J/m (yellow, moderate)
  - Burst: 30-100+ J/m (red, inefficient)
- Annotate physical reasons (leader vs streamer dominance)
- Include photos/sketches of typical spark appearance for each

**Suggested Format:** PNG, 1200x800 px

---

### 20. **thermal-diffusion-vs-diameter.png**
**Location:** `lessons/03-spark-physics/assets/`
**Referenced in:** phys-05 (Thermal Memory)

**Description:**
Graph of thermal time constant vs. channel diameter.

**Details:**
- X-axis: Channel diameter d (μm to cm, log scale)
- Y-axis: Thermal time constant τ (ms, log scale)
- Plot curve: τ = d²/(4α)
- Mark key points:
  - d = 100 μm → τ ~ 0.1 ms (streamer)
  - d = 1 mm → τ ~ 12 ms
  - d = 5 mm → τ ~ 300 ms (leader)
- Shade regions: "Streamer regime", "Leader regime"
- Add annotation for convection effects (longer persistence)

**Suggested Format:** PNG, 1000x700 px

---

### 21. **spark-channel-persistence-sequence.png**
**Location:** `lessons/03-spark-physics/assets/`
**Referenced in:** phys-05 (Thermal Memory)

**Description:**
Time-lapse sequence showing channel cooling.

**Details:**
- 5-6 frames showing spark channel over time:
  - t = 0 ms: Bright, hot channel
  - t = 1 ms: Still visible
  - t = 5 ms: Fading
  - t = 20 ms: Nearly gone (streamer)
  - t = 100 ms: Completely dissipated (streamer) OR still visible (leader)
- Use false color to show temperature
- Label each frame with time and approximate temperature
- Show two tracks: thin streamer vs thick leader

**Suggested Format:** PNG, 1500x600 px

---

### 22. **streamers-vs-leaders-photos.png**
**Location:** `lessons/03-spark-physics/assets/`
**Referenced in:** phys-06 (Streamers vs Leaders)

**Description:**
High-speed photography comparing streamer and leader appearance.

**Details:**
- Two photos side-by-side or top/bottom:
  - **Top**: Burst mode - purple/blue, highly branched streamers
  - **Bottom**: QCW mode - white/orange, thick straight leaders
- Same scale for size comparison
- Annotations pointing out:
  - Branch density
  - Channel diameter
  - Color differences
  - Straightness vs. branching
- Include camera settings and coil parameters

**Suggested Format:** PNG, 1200x1000 px

---

### 23. **streamer-to-leader-transition-sequence.png**
**Location:** `lessons/03-spark-physics/assets/`
**Referenced in:** phys-06 (Streamers vs Leaders)

**Description:**
6-step diagram showing transition mechanism.

**Details:**
- Six sequential panels showing evolution:
  1. Initial streamers (thin, branched, purple)
  2. Current begins flowing (heat accumulation)
  3. Channel heating (color shift to blue-white)
  4. Leader forms at base (thick, bright)
  5. Leader propagates (tip launches new streamers)
  6. Full leader with streamer corona at tip
- Arrows showing progression
- Temperature scale on side (1000 K → 20000 K)
- Time scale (μs → ms)

**Suggested Format:** PNG, 1500x1000 px

---

### 24. **voltage-division-vs-length-plot.png**
**Location:** `lessons/03-spark-physics/assets/`
**Referenced in:** phys-07 (Capacitive Divider)

**Description:**
Graph showing how V_tip decreases as spark grows.

**Details:**
- X-axis: Spark length L (meters, 0 to 3)
- Y-axis: V_tip / V_topload (ratio, 0 to 1)
- Plot curve: V_tip = V_topload × C_mut/(C_mut + C_sh(L))
- Show C_sh increasing linearly with L
- Mark where E_tip = E_propagation (growth stalls)
- Annotate: "Sub-linear scaling"
- Include typical values: C_mut = 10 pF, C_sh = 6.6 pF/m

**Suggested Format:** PNG, 1000x700 px

---

### 25. **capacitive-divider-circuit.png**
**Location:** `lessons/03-spark-physics/assets/`
**Referenced in:** phys-07 (Capacitive Divider)

**Description:**
Circuit diagram showing voltage division.

**Details:**
- Vertical stack:
  - V_topload at top
  - C_mut (with R in parallel)
  - V_tip at junction
  - C_sh to ground
- Show voltage divider formula
- Annotate how C_sh grows with length
- Include example calculation

**Suggested Format:** PNG, 600x800 px (vertical)

---

### 26. **length-vs-energy-scaling.png**
**Location:** `lessons/03-spark-physics/assets/`
**Referenced in:** phys-08 (Freau Relationship)

**Description:**
Log-log plot showing L vs E scaling for different modes.

**Details:**
- X-axis: Energy E (Joules, log scale, 1 to 1000)
- Y-axis: Spark length L (meters, log scale, 0.1 to 10)
- Plot three curves:
  - Burst mode: L ∝ √E (slope = 0.5)
  - QCW ramp: L ∝ E^0.7 (slope = 0.7)
  - Ideal linear: L ∝ E (slope = 1.0, dashed reference)
- Label each with operating mode
- Add data points from real measurements
- Annotate physical reasons for sub-linear scaling

**Suggested Format:** PNG, 1000x800 px

---

### 27. **qcw-vs-burst-timeline.png**
**Location:** `lessons/03-spark-physics/assets/`
**Referenced in:** phys-05, phys-08

**Description:**
Side-by-side timing diagrams comparing QCW and burst operation.

**Details:**
- Two horizontal timelines:
  - **Top**: QCW (10-20 ms ramp)
    - Power gradually increasing
    - Spark length growing continuously
    - Channel staying hot throughout
  - **Bottom**: Burst mode (100-500 μs pulse)
    - High peak power
    - Short growth window
    - Channel cools between pulses
- Show power, length, temperature on each
- Annotate key differences
- Time scale in ms

**Suggested Format:** PNG, 1400x800 px

---

## Part 4: Advanced Modeling (16 images)

### 28. **lumped-model-schematic.png**
**Location:** `lessons/04-advanced-modeling/assets/`
**Referenced in:** model-01 (Lumped Model)

**Description:**
Clean circuit schematic of lumped spark model.

**Details:**
- Three-terminal network:
  - Topload (input port)
  - Spark tip (internal node)
  - Ground (reference)
- Components clearly shown:
  - C_mut between topload and spark tip
  - R between topload and spark tip (parallel with C_mut)
  - C_sh from spark tip to ground
- Add node labels and component values
- Show integration with full coil circuit (secondary, etc.)

**Suggested Format:** PNG, 1000x600 px

---

### 29. **femm-geometry-setup-lumped.png**
**Location:** `lessons/04-advanced-modeling/assets/`
**Referenced in:** model-02 (FEMM Extraction Lumped)

**Description:**
FEMM geometry window showing setup for lumped model.

**Details:**
- Axisymmetric geometry:
  - Toroidal topload (cross-section shown)
  - Single cylindrical spark segment
  - Ground plane
  - Outer boundary
- Materials labeled (air, perfect conductor)
- Dimensions annotated
- Boundary conditions marked
- Mesh visible (not too dense, showing structure)

**Suggested Format:** PNG, 800x1000 px (vertical)

---

### 30. **maxwell-matrix-extraction.png**
**Location:** `lessons/04-advanced-modeling/assets/`
**Referenced in:** model-02 (FEMM Extraction Lumped)

**Description:**
Diagram showing Maxwell matrix extraction process.

**Details:**
- FEMM capacitance matrix output (2×2):
  ```
  [C_11  C_12]
  [C_21  C_22]
  ```
- Arrows showing extraction:
  - C_mut = |C_12| = |C_21|
  - C_sh = C_22 + C_12
- Sign convention clearly explained
- Example values shown
- Visual representation of what each capacitance means (field lines)

**Suggested Format:** PNG, 1000x700 px

---

### 31. **lumped-model-validation-checks.png**
**Location:** `lessons/04-advanced-modeling/assets/`
**Referenced in:** model-02 (FEMM Extraction Lumped)

**Description:**
Flowchart of validation procedure.

**Details:**
- Decision tree format:
  1. Check matrix symmetry → Pass/Fail
  2. Check C_sh vs. empirical rule → Within factor 2?
  3. Mesh convergence → Refine and recheck
  4. Boundary distance → Far enough?
  5. Calculate R_opt → Physical range?
- Color code: Green (pass), Yellow (warning), Red (fail)
- Include typical pass criteria

**Suggested Format:** PNG, 800x1000 px (vertical)

---

### 32. **distributed-model-structure.png**
**Location:** `lessons/04-advanced-modeling/assets/`
**Referenced in:** model-03 (Distributed Model)

**Description:**
Circuit diagram of nth-order distributed model.

**Details:**
- Vertical cascade of n segments (show n=5 for clarity):
  - Topload at top
  - Segment 1: [C_01][R_1][C_1,gnd]
  - Segment 2: [C_12][R_2][C_2,gnd]
  - ...
  - Segment n: [C_n-1,n][R_n][C_n,gnd]
- Show current direction arrows
- Label voltage at each node (V_0, V_1, ..., V_n)
- Add note: "Typically n = 5-20"
- Highlight complexity vs. lumped model

**Suggested Format:** PNG, 600x1200 px (vertical)

---

### 33. **femm-geometry-setup-distributed.png**
**Location:** `lessons/04-advanced-modeling/assets/`
**Referenced in:** model-04 (FEMM Extraction Distributed)

**Description:**
FEMM geometry for distributed model with multiple segments.

**Details:**
- Axisymmetric view:
  - Toroid topload
  - 10 cylindrical segments stacked
  - Each segment labeled (1-10)
  - Ground plane
  - Outer boundary
- Show segment numbering
- Equal length segments clearly visible
- Dimensions annotated
- Materials and boundaries labeled

**Suggested Format:** PNG, 800x1200 px (vertical)

---

### 34. **capacitance-matrix-heatmap.png**
**Location:** `lessons/04-advanced-modeling/assets/`
**Referenced in:** model-04 (FEMM Extraction Distributed)

**Description:**
Heatmap visualization of 11×11 capacitance matrix.

**Details:**
- Color-coded matrix (11 rows × 11 columns)
- Diagonal elements (large positive) in red/yellow
- Off-diagonal elements (smaller, some negative) in blue
- Symmetry visible
- Annotate:
  - Row/column 0: Topload
  - Rows/columns 1-10: Segments
- Include colorbar with scale (pF)
- Mark nearest-neighbor vs. distant coupling

**Suggested Format:** PNG, 1000x1000 px

---

### 35. **partial-capacitance-transformation.png**
**Location:** `lessons/04-advanced-modeling/assets/`
**Referenced in:** model-04 (FEMM Extraction Distributed)

**Description:**
Diagram showing Maxwell → Partial capacitance transformation.

**Details:**
- Two matrices side-by-side:
  - **Left**: Maxwell matrix (with negative off-diagonals)
  - **Right**: Partial capacitance matrix (all positive)
- Arrows showing transformation formulas
- Example for 3×3 case (easier to visualize)
- Physical interpretation of partial capacitances
- Note: "All SPICE capacitors must be positive"

**Suggested Format:** PNG, 1400x700 px

---

### 36. **resistance-taper-initialization.png**
**Location:** `lessons/04-advanced-modeling/assets/`
**Referenced in:** model-05 (Resistance Optimization)

**Description:**
Graph showing initial resistance distribution.

**Details:**
- X-axis: Position along spark (0 = base, 1 = tip)
- Y-axis: Resistance R[i] (log scale, Ω)
- Plot three curves:
  - Uniform initialization (flat line, wrong)
  - Linear taper (straight line, better)
  - Quadratic taper (recommended, R = R_base + (R_tip - R_base)×pos²)
- Shade physical bounds R_min(pos) and R_max(pos)
- Mark typical values at base and tip

**Suggested Format:** PNG, 1000x700 px

---

### 37. **iterative-optimization-convergence.png**
**Location:** `lessons/04-advanced-modeling/assets/`
**Referenced in:** model-05 (Resistance Optimization)

**Description:**
Convergence plot showing resistance values over iterations.

**Details:**
- X-axis: Iteration number (0 to 5)
- Y-axis: Resistance (log scale, kΩ to MΩ)
- Multiple curves: one for each segment (10 total)
- Show convergence:
  - Base segments (fast, 1-2 iterations)
  - Mid segments (moderate, 2-3 iterations)
  - Tip segments (slow, 3-4 iterations or flat)
- Horizontal lines showing convergence criteria (±1%)
- Color code by position (gradient base → tip)

**Suggested Format:** PNG, 1200x800 px

---

### 38. **power-distribution-along-spark.png**
**Location:** `lessons/04-advanced-modeling/assets/`
**Referenced in:** model-05, model-06

**Description:**
Bar chart showing power dissipation per segment.

**Details:**
- X-axis: Segment number (1-10, base to tip)
- Y-axis: Power dissipated (kW)
- Bar chart with values decreasing from base to tip
- Typical pattern: high at base, peak at segment 2-3, decay to tip
- Annotate percentages (e.g., segment 3 = 38% of total)
- Add cumulative line (reaching 100% at tip)
- Include total power value

**Suggested Format:** PNG, 1200x700 px

---

### 39. **current-attenuation-plot.png**
**Location:** `lessons/04-advanced-modeling/assets/`
**Referenced in:** model-05, model-06

**Description:**
Graph of current magnitude along spark.

**Details:**
- X-axis: Position along spark (m, 0 to 2.5)
- Y-axis: |I| / |I_base| (normalized current, 0 to 1)
- Plot curve showing exponential-like decay
- Mark segment boundaries
- Typical values:
  - Base: 100%
  - Middle: 70%
  - 3/4 point: 50%
  - Tip: 35%
- Include annotation about displacement current

**Suggested Format:** PNG, 1000x700 px

---

### 40. **lumped-vs-distributed-comparison.png**
**Location:** `lessons/04-advanced-modeling/assets/`
**Referenced in:** model-03, model-06

**Description:**
Table comparing lumped vs. distributed models.

**Details:**
- Two-column comparison table:
  - **Lumped Model**:
    - Single R, C_mut, C_sh
    - Fast simulation (0.1 s)
    - Good for <10 foot sparks
    - Impedance matching studies
  - **Distributed Model**:
    - n segments (10-20)
    - Slow simulation (100-200 s)
    - Accurate for any length
    - Spatial detail needed
- Color code: Green (advantage), Yellow (neutral), Red (disadvantage)
- Include "When to use each" decision guide

**Suggested Format:** PNG, 1200x800 px

---

### 41. **position-dependent-bounds.png**
**Location:** `lessons/04-advanced-modeling/assets/`
**Referenced in:** model-05 (Resistance Optimization)

**Description:**
Graph showing R_min and R_max vs position.

**Details:**
- X-axis: Position (0 = base, 1 = tip)
- Y-axis: Resistance (log scale, Ω)
- Two curves:
  - R_min[i] = 1 kΩ + (10 kΩ - 1 kΩ) × position
  - R_max[i] = 100 kΩ + (100 MΩ - 100 kΩ) × position²
- Shade feasible region between curves
- Plot typical optimized R distribution within region
- Annotate physical meaning (hot leader at base, cold streamer at tip)

**Suggested Format:** PNG, 1000x700 px

---

### 42. **spice-implementation-methods.png**
**Location:** `lessons/04-advanced-modeling/assets/`
**Referenced in:** model-04 (FEMM Extraction Distributed)

**Description:**
Three circuit diagrams showing SPICE implementation options.

**Details:**
- Three side-by-side schematics:
  1. **Partial capacitance**: All positive capacitors to ground
  2. **Controlled sources**: VCCS implementing C_ij dV/dt
  3. **Nearest-neighbor**: Simplified with only adjacent couplings
- Label pros/cons of each:
  - Partial: Accurate, complex transformation
  - Controlled: Direct, requires behavioral sources
  - Nearest-neighbor: Simple, approximate
- Show 3-node example for each

**Suggested Format:** PNG, 1500x600 px

---

### 43. **validation-total-resistance.png**
**Location:** `lessons/04-advanced-modeling/assets/`
**Referenced in:** model-05 (Resistance Optimization)

**Description:**
Chart showing expected R_total ranges.

**Details:**
- Bar chart with ranges:
  - Very low frequency (<100 kHz): 1-10 kΩ
  - Standard (200 kHz), QCW/leader: 5-50 kΩ
  - Standard (200 kHz), burst/streamer: 50-300 kΩ
  - High frequency (400+ kHz): 100-500 kΩ
- X-axis: Operating condition
- Y-axis: Total R (log scale, kΩ)
- Color code: Green (typical), Yellow (edge case), Red (check simulation)
- Include dependence notes: R ∝ 1/f, R ∝ L

**Suggested Format:** PNG, 1000x700 px

---

## Shared / General Images (2 images)

### 44. **tesla-coil-system-overview.png**
**Location:** `assets/shared/`
**Referenced in:** Multiple lessons

**Description:**
Complete Tesla coil system diagram with all components labeled.

**Details:**
- Show full system:
  - Primary circuit (tank cap, primary coil, switching)
  - Secondary coil
  - Topload
  - Spark
  - Ground connections
- Label all major components
- Show coupling coefficient
- Indicate measurement points
- Clean, professional schematic style

**Suggested Format:** PNG, 1400x1000 px

---

### 45. **complex-number-review.png**
**Location:** `assets/shared/`
**Referenced in:** fund-01 (Introduction)

**Description:**
Quick reference for complex number operations.

**Details:**
- Four quadrants showing:
  - Rectangular form (a + jb)
  - Polar form (r∠θ)
  - Euler form (re^(jθ))
  - Complex conjugate (a - jb)
- Conversion formulas
- Multiplication, division, addition rules
- Complex plane with example
- Common electrical engineering conventions (j = √-1)

**Suggested Format:** PNG, 1000x800 px

---

## Screenshot Requirements (FEMM)

Several lessons require actual FEMM screenshots. These should be taken from real simulations:

1. **FEMM interface overview** (model-02, model-04)
2. **Mesh generation example** (model-02)
3. **Electrostatic solution with field plot** (phys-02, model-02)
4. **Capacitance matrix output** (model-02, model-04)
5. **Boundary condition setup** (model-02)

---

## Format Specifications

**General Guidelines:**
- **File format:** PNG with transparency where appropriate
- **Resolution:** Minimum 1000px on longest dimension
- **Color scheme:** Support both light and dark mode viewing
- **Text:** Minimum 14pt font size for labels
- **Accessibility:** High contrast, colorblind-friendly palettes
- **Compression:** Optimize for web (target <500 KB per image)

**Tools Recommended:**
- Circuit diagrams: Inkscape, Draw.io, LTspice screenshots
- Graphs/plots: Python matplotlib, MATLAB, or similar
- 3D geometry: Blender, FEMM 3D view, CAD software
- Photography: High-speed camera (if available) or stock images

---

## Priority Levels

**High Priority (Create first):**
1-6, 9-11, 16-19, 28-30 (Core concepts, most referenced)

**Medium Priority:**
7-8, 12-15, 20-27, 31-37 (Supporting material)

**Low Priority (Can use placeholders initially):**
38-45 (Nice-to-have, less critical for learning)

---

## Notes for Artists/Designers

- Maintain consistent style across all images
- Use course color scheme (define: primary, secondary, accent colors)
- Ensure equations are typeset properly (LaTeX or similar)
- Add version numbers to images for tracking updates
- Create SVG sources where possible for future editing
- Include brief image captions in the markdown lessons

---

**Document Version:** 1.0
**Last Updated:** 2025-10-10
**Total Images:** 45+
**Estimated Creation Time:** 40-60 hours