Module specification: Vacuum system
Honesty note. The r1 vacuum system is the clearest case of available ≠ optimal in this project: it was assembled from equipment we could actually obtain. This page therefore states what the vacuum system must do; the r1 build pages show one way to do it. If you are procuring from scratch, follow the procurement guide below, not the r1 parts list.
Requirement status legend used on all module pages:
- ✅ Validated — r1 operates at this value and works.
- 🟡 Estimated — we believe this bound is acceptable; not tested.
- ❓ Untested — unknown; a replication data point would be a valuable contribution (see Contributing).
Function
Provide and maintain the process environment for ablation, deposition and in-situ mask machining: a base vacuum low enough that background gas does not dominate film contamination or plume dynamics, with practical pump-down times for an iterate-heavy workflow.
Requirements
| # | Requirement | Value | Status |
|---|---|---|---|
| V1 | Base pressure | ≤ TODO mbar (r1 achieves TODO) | ✅ |
| V2 | Working pressure during deposition | TODO | ✅ |
| V3 | Pump-down time, vent → working pressure | ≤ TODO min (r1: TODO) | ✅ |
| V4 | Chamber standard | ISO160 body; see wall contract | ✅ |
| V5 | Minimum acceptable base pressure for usable films | 🟡 TODO — we suspect ≥ 1e-4 mbar degrades adhesion/purity, untested | 🟡 |
| V6 | Process gas admission (e.g. O₂ for oxides) | needle/leak valve port | ❓ if not yet used on r1 → mark accordingly |
Interfaces
Defined in Architecture → vacuum wall contract: two optical viewports (machining + ablation), motion feedthroughs for the main mechanism, electrical feedthrough(s), gauge and vent/gas ports. The main mechanism must fit through the chamber opening with the galvo slid aside on its rails — this sets the maximum mechanism envelope (TODO: dimensions).
Design rationale
- ISO160 was chosen because . ISO-K clamped flanges keep surplus compatibility high and cost low compared to CF; the pressures required (high vacuum, not UHV) do not justify CF.
- The mechanism-inside-chamber architecture means the vacuum system is deliberately dumb: all intelligence (motion, registration) lives in the main mechanism; the chamber only provides environment and crossings. This keeps chamber substitution easy.
Procurement guide
If you are starting from zero (recommended route):
- Pumping: TODO — recommended stack (e.g. turbomolecular + dry backing pump), approximate speed class for V3, and why oil-free backing is worth it near optics and thin films.
- Chamber: any ISO160 body meeting the port count in the wall contract; custom-drilled lids are often the cheapest way to get the two viewports in the right geometry.
- Gauging: one wide-range gauge is sufficient for operation (TODO: type used on r1 and whether it limits what you can claim about V1).
If you are working from surplus / donated / salvaged equipment (the r1 route): what actually matters to verify —
- Pump reaches the V1/V2 pressures on your chamber volume with your seal state, not on its datasheet blank-off.
- Flange compatibility or adaptability to ISO-K (adapters are cheap; exotic legacy flanges are not).
- For oil pumps: contamination path to the chamber (backstreaming) and to the viewports — mitigation TODO (foreline trap? bakeout practice?).
- What does not matter: cosmetic condition, age, missing controllers on gauges (heads are often reusable), ultimate-vacuum specs far beyond V1.
Reference implementation
- Build r1 → vacuum system — parts, assembly, leak-checking procedure.
Known variants
None yet. Proposed variants and validation reports: see Contributing.