# 📐  L2 Spec — X-ray Phase Contrast — propagation / grating / analyzer Mismatch-Only Spec

**ID:** `L2-254-001` · **Status:** ⊙ Testnet (genesis catalog)
**Parents:** ⬆ Principle [`L1-254`](/artifact/l1/L1-254)

> **🎯 Tolerance (ε):** expression
> **⚖ Difficulty score:** 0.48 · **Delta tier:** 5
> **⛓ On-chain block:** 41554002

---

## 1. Domain Ω

**Type:** `range`

| Parameter | Unit | Range |
|---|---|---|
| H | px | 256 – 8192 |
| W | px | 256 – 8192 |
| Z | — | 32 – 1024 |
| Snr db | dB | 0 – 40 |
| Z error | — | 0.0 – 0.1 |
| N distances | — | 1 – 50 |
| Coherence error | — | 0.0 – 0.3 |
| Beam harmonics error | — | 0.0 – 0.2 |

## 2. Tolerance (ε)

**Type:** `fn`

```
18.0 + 0.3*SNR_dB - 15.0*z_error - 10.0*coherence_error - 5.0*beam_harmonics_error
```

## 3. Difficulty

| Property | Value |
|---|---|
| Difficulty score | 0.48 |
| Delta tier | 5 |

## 4. Fingerprint

`4e3e776b6d3e47e8d57d02815dd6af3d723a32d3d386260dccf0fd76bca3c234`

## 5. On-chain Registration

- **Chain hash:** `0x4662d3b485e519db612160dc4507de8142450269c63ab286773d8fa1d4f35a7e`
- **Chain tx hash:** `0x902c05cf3654506655a6fc234471d20dbc1ee3ad9ec729b7371d87bffbe34af6`
- **Chain block:** `41554002`

---

## File Mapping

This bundle consists of: `L2-254-001.md`, `L2-254-001.json`.

| File | Role | How to regenerate |
|------|------|-------------------|
| `L2-254-001.md` | Source of truth — edit this | Human or LLM |
| `L2-254-001.json` | Structured metadata for the registry | LLM regenerates from the sections above |

**Prompt for your LLM after editing this Markdown:**

> Read the attached Markdown. Regenerate the sibling `.json` so every field matches.
> Preserve the schema documented in the rows above.
> Output each file in its own fenced code block tagged with the filename.
> Output only the JSON object.

_This Markdown was auto-synthesized from the catalog row for `L2-254-001`._
_Edit it, regenerate the JSON, and submit at [/submit](/submit) to claim the artifact._