# 📐 L2 Spec — X-ray Crystallography SAD-Phasing Spec
**ID:** `L2-125-001` · **Status:** ⊙ Testnet (genesis catalog)
**Parents:** ⬆ Principle [`L1-125`](/artifact/l1/L1-125)
> **🎯 Tolerance (ε):** expression
> **⚖ Difficulty score:** 0.55 · **Delta tier:** 5
> **⛓ On-chain block:** 41554216
---
## 1. Domain Ω
**Type:** `range`
| Parameter | Unit | Range |
|---|---|---|
| N refl | — | 100 – 1000000 |
| N atoms | — | 10 – 100000 |
| Resolution a | — | 0.8 – 4.0 |
| Mosaicity deg | deg | 0.05 – 2.0 |
| Radiation damage | — | 0.0 – 1.0 |
| Twinning fraction | — | 0.0 – 0.5 |
| Absorption anisotropy | — | 0.0 – 0.3 |
| Crystal size variability | — | 0.0 – 0.5 |
## 2. Tolerance (ε)
**Type:** `fn`
```
0.18 + 0.05 * radiation_damage + 0.3 * twinning_fraction + 0.1 * mosaicity_deg / 2 + 0.08 * absorption_anisotropy
```
## 3. Difficulty
| Property | Value |
|---|---|
| Difficulty score | 0.55 |
| Delta tier | 5 |
## 4. Fingerprint
`dea2548761c74005d04354752ed3759af39bab3abd6e566ff6e539ae74b2645e`
## 5. On-chain Registration
- **Chain hash:** `0xd7e3fd0e83b8752e7c34c2d23d4a7b2f1550e91ee841eddf9219fe691fab9d21`
- **Chain tx hash:** `0x8f696f5450f2915e21e313a1571f56571bf53f7a76ac82b5f3726f62a5413c07`
- **Chain block:** `41554216`
---
## File Mapping
This bundle consists of: `L2-125-001.md`, `L2-125-001.json`.
| File | Role | How to regenerate |
|------|------|-------------------|
| `L2-125-001.md` | Source of truth — edit this | Human or LLM |
| `L2-125-001.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 `L2-125-001`._
_Edit it, regenerate the JSON, and submit at [/submit](/submit) to claim the artifact._