Chamber Types
| Chamber Type |
Geometry |
Typical Applications |
Key Characteristics |
| Cylindrical |
Round cross-section, flat or domed ends |
General-purpose HV/UHV, sputtering, evaporation |
Excellent pressure distribution; easy to manufacture; standard port placement on barrel and endplates |
| Spherical |
True sphere or near-sphere |
Research chambers, particle physics, fusion experiments |
Optimal strength-to-weight ratio; uniform stress under vacuum; complex to fabricate and port |
| Box / Rectangular |
Flat-panel construction with reinforcing ribs |
Load-lock chambers, gloveboxes, inline coating systems |
Maximum internal access; requires thicker walls or stiffeners to resist atmospheric load; easier to integrate conveyors |
| Custom / Application-Specific |
Hybrid geometries, bell jars, T-pieces |
Electron microscopy, beam lines, specialised deposition |
Designed around the process; often includes integral viewports, manipulator flanges, and feedthroughs |
Design rule of thumb:
Atmospheric pressure exerts ~10 tonnes per square metre on the chamber walls. A 300 mm diameter viewport window (area ~0.07 m²) bears ~700 kg of force. Always verify wall thickness calculations against the intended vacuum level.
Valve Types
| Valve Type |
Flow Characteristic |
Seal Type |
Typical Use Cases |
Key Notes |
| Gate Valve |
Full bore — minimal flow restriction when open |
Viton or metal bonnet seal |
Main chamber isolation; high-conductance path between pump and chamber |
Do not throttle (use fully open or fully closed). Available in manual, pneumatic, and motorised variants. |
| Angle Valve |
90° flow path — moderate conductance |
Viton O-ring or metal bellows |
Pump isolation; roughing line shut-off; gas inlet control |
Compact design. Bellows-sealed versions eliminate elastomer outgassing for HV/UHV use. |
| Butterfly Valve |
Disc rotates in flow path — variable restriction |
Viton or PTFE seat |
Throttling / pressure control; large-diameter roughing lines |
Can be used for pressure regulation (throttle mode). Not suitable for UHV due to trapped volume around disc. |
| Needle Valve |
Fine metering — very low conductance |
Metal-to-metal seat |
Gas dosing; leak calibration; controlled venting |
Provides precise flow control for introducing process gases or controlled leaks. Not for isolation. |
Feedthrough Types
| Feedthrough |
What Passes Through |
Seal Method |
Typical Applications |
| Electrical |
Power, signal, thermocouple wires |
Glass-to-metal or ceramic-to-metal brazed seal |
Heater power, sensor readout, bias voltage, in-vacuum electronics |
| Motion |
Linear or rotary mechanical motion |
Bellows (linear), ferrofluidic or magnetically-coupled (rotary) |
Sample manipulation, shutter operation, substrate rotation |
| Optical |
Light (visible, UV, IR, laser) |
Fused silica or sapphire window brazed to metal flange |
Viewports, laser access, optical pyrometry, spectroscopy |
| Fluid |
Cooling water, process gas, cryogens |
Welded tube or compression fitting with metal seal |
Substrate cooling, gas delivery, cryogenic systems |
Isolation Principles
Why isolate sections of a vacuum system?
- Protect sensitive components — turbo pumps, gauges, and samples can be damaged by sudden pressure changes or backstreaming oil vapour
- Enable partial maintenance — service one section without venting the entire system
- Contamination control — prevent cross-contamination between process zones (e.g., load-lock vs. process chamber)
- Safety — isolate high-voltage feedthroughs or hazardous process gases before opening flanges
- Pump protection — prevent roughing pumps from ingesting process gases or particles
Rule: Every distinct vacuum zone should have its own isolation valve. If a section cannot be isolated independently, a single failure (leak, pump trip, gauge failure) can compromise the entire system.
Valve Sequencing Rules
Pump-Down Sequence
- Verify all flanges sealed, chamber closed
- Open foreline valve (backing pump to turbo foreline)
- Start roughing/backing pump
- Open roughing valve to begin chamber pump-down
- Monitor pressure: wait for crossover pressure (~0.1 mbar)
- Close roughing valve
- Start turbo pump (with backing pump running)
- Open high-vacuum gate valve when turbo is at full speed
- Monitor base pressure; begin bakeout if required
Vent Sequence
- Close high-vacuum gate valve
- Allow turbo pump to spin down (do NOT vent while spinning)
- Close foreline valve
- Stop backing pump
- Open vent valve slowly — use dry nitrogen if available
- Wait for chamber to reach atmospheric pressure
- Open chamber
Emergency isolation: Close the high-vacuum gate valve FIRST. This protects the turbo pump and chamber. Then close foreline and stop pumps. Never vent a spinning turbo pump — wait for rotor to stop.